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 // SPDX-License-Identifier: GPL-2.0
 /*
  *  linux/fs/proc/base.c
  *
  *  Copyright (C) 1991, 1992 Linus Torvalds
  *
  *  proc base directory handling functions
  *
  *  1999, Al Viro. Rewritten. Now it covers the whole per-process part.
  *  Instead of using magical inumbers to determine the kind of object
  *  we allocate and fill in-core inodes upon lookup. They don't even
  *  go into icache. We cache the reference to task_struct upon lookup too.
  *  Eventually it should become a filesystem in its own. We don't use the
  *  rest of procfs anymore.
  *
  *
  *  Changelog:
  *  17-Jan-2005
  *  Allan Bezerra
  *  Bruna Moreira <bruna.moreira@indt.org.br>
  *  Edjard Mota <edjard.mota@indt.org.br>
  *  Ilias Biris <ilias.biris@indt.org.br>
  *  Mauricio Lin <mauricio.lin@indt.org.br>
  *
  *  Embedded Linux Lab - 10LE Instituto Nokia de Tecnologia - INdT
  *
  *  A new process specific entry (smaps) included in /proc. It shows the
  *  size of rss for each memory area. The maps entry lacks information
  *  about physical memory size (rss) for each mapped file, i.e.,
  *  rss information for executables and library files.
  *  This additional information is useful for any tools that need to know
  *  about physical memory consumption for a process specific library.
  *
  *  Changelog:
  *  21-Feb-2005
  *  Embedded Linux Lab - 10LE Instituto Nokia de Tecnologia - INdT
  *  Pud inclusion in the page table walking.
  *
  *  ChangeLog:
  *  10-Mar-2005
  *  10LE Instituto Nokia de Tecnologia - INdT:
  *  A better way to walks through the page table as suggested by Hugh Dickins.
  *
  *  Simo Piiroinen <simo.piiroinen@nokia.com>:
  *  Smaps information related to shared, private, clean and dirty pages.
  *
  *  Paul Mundt <paul.mundt@nokia.com>:
  *  Overall revision about smaps.
  */
 
 #include <linux/uaccess.h>
 
 #include <linux/errno.h>
 #include <linux/time.h>
 #include <linux/proc_fs.h>
 #include <linux/stat.h>
 #include <linux/task_io_accounting_ops.h>
 #include <linux/init.h>
 #include <linux/capability.h>
 #include <linux/file.h>
 #include <linux/fdtable.h>
 #include <linux/generic-radix-tree.h>
 #include <linux/string.h>
 #include <linux/seq_file.h>
 #include <linux/namei.h>
 #include <linux/mnt_namespace.h>
 #include <linux/mm.h>
 #include <linux/swap.h>
 #include <linux/rcupdate.h>
 #include <linux/kallsyms.h>
 #include <linux/stacktrace.h>
 #include <linux/resource.h>
 #include <linux/module.h>
 #include <linux/mount.h>
 #include <linux/security.h>
 #include <linux/ptrace.h>
 #include <linux/printk.h>
 #include <linux/cache.h>
 #include <linux/cgroup.h>
 #include <linux/cpuset.h>
 #include <linux/audit.h>
 #include <linux/poll.h>
 #include <linux/nsproxy.h>
 #include <linux/oom.h>
 #include <linux/elf.h>
 #include <linux/pid_namespace.h>
 #include <linux/user_namespace.h>
 #include <linux/fs_struct.h>
 #include <linux/slab.h>
 #include <linux/sched/autogroup.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/coredump.h>
 #include <linux/sched/debug.h>
 #include <linux/sched/stat.h>
 #include <linux/posix-timers.h>
 #include <linux/time_namespace.h>
 #include <linux/resctrl.h>
 #include <linux/cn_proc.h>
 #include <trace/events/oom.h>
 #include "internal.h"
 #include "fd.h"
 
 #include "../../lib/kstrtox.h"
 
 /* NOTE:
  *  Implementing inode permission operations in /proc is almost
  *  certainly an error.  Permission checks need to happen during
  *  each system call not at open time.  The reason is that most of
  *  what we wish to check for permissions in /proc varies at runtime.
  *
  *  The classic example of a problem is opening file descriptors
  *  in /proc for a task before it execs a suid executable.
  */
 
 static u8 nlink_tid __ro_after_init;
 static u8 nlink_tgid __ro_after_init;
 
 struct pid_entry {
     const char *name;
     unsigned int len;
     umode_t mode;
     const struct inode_operations *iop;
     const struct file_operations *fop;
     union proc_op op;
 };
 
 #define NOD(NAME, MODE, IOP, FOP, OP) {         \
     .name = (NAME),                 \
     .len  = sizeof(NAME) - 1,           \
     .mode = MODE,                   \
     .iop  = IOP,                    \
     .fop  = FOP,                    \
     .op   = OP,                 \
 }
 
 #define DIR(NAME, MODE, iops, fops) \
     NOD(NAME, (S_IFDIR|(MODE)), &iops, &fops, {} )
 #define LNK(NAME, get_link)                 \
     NOD(NAME, (S_IFLNK|S_IRWXUGO),              \
         &proc_pid_link_inode_operations, NULL,      \
         { .proc_get_link = get_link } )
 #define REG(NAME, MODE, fops)               \
     NOD(NAME, (S_IFREG|(MODE)), NULL, &fops, {})
 #define ONE(NAME, MODE, show)               \
     NOD(NAME, (S_IFREG|(MODE)),         \
         NULL, &proc_single_file_operations, \
         { .proc_show = show } )
 #define ATTR(LSM, NAME, MODE)               \
     NOD(NAME, (S_IFREG|(MODE)),         \
         NULL, &proc_pid_attr_operations,    \
         { .lsm = LSM })
 
 /*
  * Count the number of hardlinks for the pid_entry table, excluding the .
  * and .. links.
  */
 static unsigned int __init pid_entry_nlink(const struct pid_entry *entries,
     unsigned int n)
 {
     unsigned int i;
     unsigned int count;
 
     count = 2;
     for (i = 0; i < n; ++i) {
         if (S_ISDIR(entries[i].mode))
             ++count;
     }
 
     return count;
 }
 
 static int get_task_root(struct task_struct *task, struct path *root)
 {
     int result = -ENOENT;
 
     task_lock(task);
     if (task->fs) {
         get_fs_root(task->fs, root);
         result = 0;
     }
     task_unlock(task);
     return result;
 }
 
 static int proc_cwd_link(struct dentry *dentry, struct path *path)
 {
     struct task_struct *task = get_proc_task(d_inode(dentry));
     int result = -ENOENT;
 
     if (task) {
         task_lock(task);
         if (task->fs) {
             get_fs_pwd(task->fs, path);
             result = 0;
         }
         task_unlock(task);
         put_task_struct(task);
     }
     return result;
 }
 
 static int proc_root_link(struct dentry *dentry, struct path *path)
 {
     struct task_struct *task = get_proc_task(d_inode(dentry));
     int result = -ENOENT;
 
     if (task) {
         result = get_task_root(task, path);
         put_task_struct(task);
     }
     return result;
 }
 
 /*
  * If the user used setproctitle(), we just get the string from
  * user space at arg_start, and limit it to a maximum of one page.
  */
 static ssize_t get_mm_proctitle(struct mm_struct *mm, char __user *buf,
                 size_t count, unsigned long pos,
                 unsigned long arg_start)
 {
     char *page;
     int ret, got;
 
     if (pos >= PAGE_SIZE)
         return 0;
 
     page = (char *)__get_free_page(GFP_KERNEL);
     if (!page)
         return -ENOMEM;
 
     ret = 0;
     got = access_remote_vm(mm, arg_start, page, PAGE_SIZE, FOLL_ANON);
     if (got > 0) {
         int len = strnlen(page, got);
 
         /* Include the NUL character if it was found */
         if (len < got)
             len++;
 
         if (len > pos) {
             len -= pos;
             if (len > count)
                 len = count;
             len -= copy_to_user(buf, page+pos, len);
             if (!len)
                 len = -EFAULT;
             ret = len;
         }
     }
     free_page((unsigned long)page);
     return ret;
 }
 
 static ssize_t get_mm_cmdline(struct mm_struct *mm, char __user *buf,
                   size_t count, loff_t *ppos)
 {
     unsigned long arg_start, arg_end, env_start, env_end;
     unsigned long pos, len;
     char *page, c;
 
     /* Check if process spawned far enough to have cmdline. */
     if (!mm->env_end)
         return 0;
 
     spin_lock(&mm->arg_lock);
     arg_start = mm->arg_start;
     arg_end = mm->arg_end;
     env_start = mm->env_start;
     env_end = mm->env_end;
     spin_unlock(&mm->arg_lock);
 
     if (arg_start >= arg_end)
         return 0;
 
     /*
      * We allow setproctitle() to overwrite the argument
      * strings, and overflow past the original end. But
      * only when it overflows into the environment area.
      */
     if (env_start != arg_end || env_end < env_start)
         env_start = env_end = arg_end;
     len = env_end - arg_start;
 
     /* We're not going to care if "*ppos" has high bits set */
     pos = *ppos;
     if (pos >= len)
         return 0;
     if (count > len - pos)
         count = len - pos;
     if (!count)
         return 0;
 
     /*
      * Magical special case: if the argv[] end byte is not
      * zero, the user has overwritten it with setproctitle(3).
      *
      * Possible future enhancement: do this only once when
      * pos is 0, and set a flag in the 'struct file'.
      */
     if (access_remote_vm(mm, arg_end-1, &c, 1, FOLL_ANON) == 1 && c)
         return get_mm_proctitle(mm, buf, count, pos, arg_start);
 
     /*
      * For the non-setproctitle() case we limit things strictly
      * to the [arg_start, arg_end[ range.
      */
     pos += arg_start;
     if (pos < arg_start || pos >= arg_end)
         return 0;
     if (count > arg_end - pos)
         count = arg_end - pos;
 
     page = (char *)__get_free_page(GFP_KERNEL);
     if (!page)
         return -ENOMEM;
 
     len = 0;
     while (count) {
         int got;
         size_t size = min_t(size_t, PAGE_SIZE, count);
 
         got = access_remote_vm(mm, pos, page, size, FOLL_ANON);
         if (got <= 0)
             break;
         got -= copy_to_user(buf, page, got);
         if (unlikely(!got)) {
             if (!len)
                 len = -EFAULT;
             break;
         }
         pos += got;
         buf += got;
         len += got;
         count -= got;
     }
 
     free_page((unsigned long)page);
     return len;
 }
 
 static ssize_t get_task_cmdline(struct task_struct *tsk, char __user *buf,
                 size_t count, loff_t *pos)
 {
     struct mm_struct *mm;
     ssize_t ret;
 
     mm = get_task_mm(tsk);
     if (!mm)
         return 0;
 
     ret = get_mm_cmdline(mm, buf, count, pos);
     mmput(mm);
     return ret;
 }
 
 static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf,
                      size_t count, loff_t *pos)
 {
     struct task_struct *tsk;
     ssize_t ret;
 
     BUG_ON(*pos < 0);
 
     tsk = get_proc_task(file_inode(file));
     if (!tsk)
         return -ESRCH;
     ret = get_task_cmdline(tsk, buf, count, pos);
     put_task_struct(tsk);
     if (ret > 0)
         *pos += ret;
     return ret;
 }
 
 static const struct file_operations proc_pid_cmdline_ops = {
     .read   = proc_pid_cmdline_read,
     .llseek = generic_file_llseek,
 };
 
 #ifdef CONFIG_KALLSYMS
 /*
  * Provides a wchan file via kallsyms in a proper one-value-per-file format.
  * Returns the resolved symbol.  If that fails, simply return the address.
  */
 static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
               struct pid *pid, struct task_struct *task)
 {
     unsigned long wchan;
     char symname[KSYM_NAME_LEN];
 
     if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
         goto print0;
 
     wchan = get_wchan(task);
     if (wchan && !lookup_symbol_name(wchan, symname)) {
         seq_puts(m, symname);
         return 0;
     }
 
 print0:
     seq_putc(m, '0');
     return 0;
 }
 #endif /* CONFIG_KALLSYMS */
 
 static int lock_trace(struct task_struct *task)
 {
     int err = down_read_killable(&task->signal->exec_update_lock);
     if (err)
         return err;
     if (!ptrace_may_access(task, PTRACE_MODE_ATTACH_FSCREDS)) {
         up_read(&task->signal->exec_update_lock);
         return -EPERM;
     }
     return 0;
 }
 
 static void unlock_trace(struct task_struct *task)
 {
     up_read(&task->signal->exec_update_lock);
 }
 
 #ifdef CONFIG_STACKTRACE
 
 #define MAX_STACK_TRACE_DEPTH   64
 
 static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns,
               struct pid *pid, struct task_struct *task)
 {
     unsigned long *entries;
     int err;
 
     /*
      * The ability to racily run the kernel stack unwinder on a running task
      * and then observe the unwinder output is scary; while it is useful for
      * debugging kernel issues, it can also allow an attacker to leak kernel
      * stack contents.
      * Doing this in a manner that is at least safe from races would require
      * some work to ensure that the remote task can not be scheduled; and
      * even then, this would still expose the unwinder as local attack
      * surface.
      * Therefore, this interface is restricted to root.
      */
     if (!file_ns_capable(m->file, &init_user_ns, CAP_SYS_ADMIN))
         return -EACCES;
 
     entries = kmalloc_array(MAX_STACK_TRACE_DEPTH, sizeof(*entries),
                 GFP_KERNEL);
     if (!entries)
         return -ENOMEM;
 
     err = lock_trace(task);
     if (!err) {
         unsigned int i, nr_entries;
 
         nr_entries = stack_trace_save_tsk(task, entries,
                           MAX_STACK_TRACE_DEPTH, 0);
 
         for (i = 0; i < nr_entries; i++) {
             seq_printf(m, "[<0>] %pB\n", (void *)entries[i]);
         }
 
         unlock_trace(task);
     }
     kfree(entries);
 
     return err;
 }
 #endif
 
 #ifdef CONFIG_SCHED_INFO
 /*
  * Provides /proc/PID/schedstat
  */
 static int proc_pid_schedstat(struct seq_file *m, struct pid_namespace *ns,
                   struct pid *pid, struct task_struct *task)
 {
     if (unlikely(!sched_info_on()))
         seq_puts(m, "0 0 0\n");
     else
         seq_printf(m, "%llu %llu %lu\n",
            (unsigned long long)task->se.sum_exec_runtime,
            (unsigned long long)task->sched_info.run_delay,
            task->sched_info.pcount);
 
     return 0;
 }
 #endif
 
 #ifdef CONFIG_LATENCYTOP
 static int lstats_show_proc(struct seq_file *m, void *v)
 {
     int i;
     struct inode *inode = m->private;
     struct task_struct *task = get_proc_task(inode);
 
     if (!task)
         return -ESRCH;
     seq_puts(m, "Latency Top version : v0.1\n");
     for (i = 0; i < LT_SAVECOUNT; i++) {
         struct latency_record *lr = &task->latency_record[i];
         if (lr->backtrace[0]) {
             int q;
             seq_printf(m, "%i %li %li",
                    lr->count, lr->time, lr->max);
             for (q = 0; q < LT_BACKTRACEDEPTH; q++) {
                 unsigned long bt = lr->backtrace[q];
 
                 if (!bt)
                     break;
                 seq_printf(m, " %ps", (void *)bt);
             }
             seq_putc(m, '\n');
         }
 
     }
     put_task_struct(task);
     return 0;
 }
 
 static int lstats_open(struct inode *inode, struct file *file)
 {
     return single_open(file, lstats_show_proc, inode);
 }
 
 static ssize_t lstats_write(struct file *file, const char __user *buf,
                 size_t count, loff_t *offs)
 {
     struct task_struct *task = get_proc_task(file_inode(file));
 
     if (!task)
         return -ESRCH;
     clear_tsk_latency_tracing(task);
     put_task_struct(task);
 
     return count;
 }
 
 static const struct file_operations proc_lstats_operations = {
     .open       = lstats_open,
     .read       = seq_read,
     .write      = lstats_write,
     .llseek     = seq_lseek,
     .release    = single_release,
 };
 
 #endif
 
 static int proc_oom_score(struct seq_file *m, struct pid_namespace *ns,
               struct pid *pid, struct task_struct *task)
 {
     unsigned long totalpages = totalram_pages() + total_swap_pages;
     unsigned long points = 0;
     long badness;
 
     badness = oom_badness(task, totalpages);
     /*
      * Special case OOM_SCORE_ADJ_MIN for all others scale the
      * badness value into [0, 2000] range which we have been
      * exporting for a long time so userspace might depend on it.
      */
     if (badness != LONG_MIN)
         points = (1000 + badness * 1000 / (long)totalpages) * 2 / 3;
 
     seq_printf(m, "%lu\n", points);
 
     return 0;
 }
 
 struct limit_names {
     const char *name;
     const char *unit;
 };
 
 static const struct limit_names lnames[RLIM_NLIMITS] = {
     [RLIMIT_CPU] = {"Max cpu time", "seconds"},
     [RLIMIT_FSIZE] = {"Max file size", "bytes"},
     [RLIMIT_DATA] = {"Max data size", "bytes"},
     [RLIMIT_STACK] = {"Max stack size", "bytes"},
     [RLIMIT_CORE] = {"Max core file size", "bytes"},
     [RLIMIT_RSS] = {"Max resident set", "bytes"},
     [RLIMIT_NPROC] = {"Max processes", "processes"},
     [RLIMIT_NOFILE] = {"Max open files", "files"},
     [RLIMIT_MEMLOCK] = {"Max locked memory", "bytes"},
     [RLIMIT_AS] = {"Max address space", "bytes"},
     [RLIMIT_LOCKS] = {"Max file locks", "locks"},
     [RLIMIT_SIGPENDING] = {"Max pending signals", "signals"},
     [RLIMIT_MSGQUEUE] = {"Max msgqueue size", "bytes"},
     [RLIMIT_NICE] = {"Max nice priority", NULL},
     [RLIMIT_RTPRIO] = {"Max realtime priority", NULL},
     [RLIMIT_RTTIME] = {"Max realtime timeout", "us"},
 };
 
 /* Display limits for a process */
 static int proc_pid_limits(struct seq_file *m, struct pid_namespace *ns,
                struct pid *pid, struct task_struct *task)
 {
     unsigned int i;
     unsigned long flags;
 
     struct rlimit rlim[RLIM_NLIMITS];
 
     if (!lock_task_sighand(task, &flags))
         return 0;
     memcpy(rlim, task->signal->rlim, sizeof(struct rlimit) * RLIM_NLIMITS);
     unlock_task_sighand(task, &flags);
 
     /*
      * print the file header
      */
     seq_puts(m, "Limit                     "
         "Soft Limit           "
         "Hard Limit           "
         "Units     \n");
 
     for (i = 0; i < RLIM_NLIMITS; i++) {
         if (rlim[i].rlim_cur == RLIM_INFINITY)
             seq_printf(m, "%-25s %-20s ",
                    lnames[i].name, "unlimited");
         else
             seq_printf(m, "%-25s %-20lu ",
                    lnames[i].name, rlim[i].rlim_cur);
 
         if (rlim[i].rlim_max == RLIM_INFINITY)
             seq_printf(m, "%-20s ", "unlimited");
         else
             seq_printf(m, "%-20lu ", rlim[i].rlim_max);
 
         if (lnames[i].unit)
             seq_printf(m, "%-10s\n", lnames[i].unit);
         else
             seq_putc(m, '\n');
     }
 
     return 0;
 }
 
 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
 static int proc_pid_syscall(struct seq_file *m, struct pid_namespace *ns,
                 struct pid *pid, struct task_struct *task)
 {
     struct syscall_info info;
     u64 *args = &info.data.args[0];
     int res;
 
     res = lock_trace(task);
     if (res)
         return res;
 
     if (task_current_syscall(task, &info))
         seq_puts(m, "running\n");
     else if (info.data.nr < 0)
         seq_printf(m, "%d 0x%llx 0x%llx\n",
                info.data.nr, info.sp, info.data.instruction_pointer);
     else
         seq_printf(m,
                "%d 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx 0x%llx\n",
                info.data.nr,
                args[0], args[1], args[2], args[3], args[4], args[5],
                info.sp, info.data.instruction_pointer);
     unlock_trace(task);
 
     return 0;
 }
 #endif /* CONFIG_HAVE_ARCH_TRACEHOOK */
 
 /************************************************************************/
 /*                       Here the fs part begins                        */
 /************************************************************************/
 
 /* permission checks */
 static bool proc_fd_access_allowed(struct inode *inode)
 {
     struct task_struct *task;
     bool allowed = false;
     /* Allow access to a task's file descriptors if it is us or we
      * may use ptrace attach to the process and find out that
      * information.
      */
     task = get_proc_task(inode);
     if (task) {
         allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
         put_task_struct(task);
     }
     return allowed;
 }
 
 int proc_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
          struct iattr *attr)
 {
     int error;
     struct inode *inode = d_inode(dentry);
 
     if (attr->ia_valid & ATTR_MODE)
         return -EPERM;
 
     error = setattr_prepare(&init_user_ns, dentry, attr);
     if (error)
         return error;
 
     setattr_copy(&init_user_ns, inode, attr);
     mark_inode_dirty(inode);
     return 0;
 }
 
 /*
  * May current process learn task's sched/cmdline info (for hide_pid_min=1)
  * or euid/egid (for hide_pid_min=2)?
  */
 static bool has_pid_permissions(struct proc_fs_info *fs_info,
                  struct task_struct *task,
                  enum proc_hidepid hide_pid_min)
 {
     /*
      * If 'hidpid' mount option is set force a ptrace check,
      * we indicate that we are using a filesystem syscall
      * by passing PTRACE_MODE_READ_FSCREDS
      */
     if (fs_info->hide_pid == HIDEPID_NOT_PTRACEABLE)
         return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
 
     if (fs_info->hide_pid < hide_pid_min)
         return true;
     if (in_group_p(fs_info->pid_gid))
         return true;
     return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
 }
 
 
 static int proc_pid_permission(struct user_namespace *mnt_userns,
                    struct inode *inode, int mask)
 {
     struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
     struct task_struct *task;
     bool has_perms;
 
     task = get_proc_task(inode);
     if (!task)
         return -ESRCH;
     has_perms = has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS);
     put_task_struct(task);
 
     if (!has_perms) {
         if (fs_info->hide_pid == HIDEPID_INVISIBLE) {
             /*
              * Let's make getdents(), stat(), and open()
              * consistent with each other.  If a process
              * may not stat() a file, it shouldn't be seen
              * in procfs at all.
              */
             return -ENOENT;
         }
 
         return -EPERM;
     }
     return generic_permission(&init_user_ns, inode, mask);
 }
 
 
 
 static const struct inode_operations proc_def_inode_operations = {
     .setattr    = proc_setattr,
 };
 
 static int proc_single_show(struct seq_file *m, void *v)
 {
     struct inode *inode = m->private;
     struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
     struct pid *pid = proc_pid(inode);
     struct task_struct *task;
     int ret;
 
     task = get_pid_task(pid, PIDTYPE_PID);
     if (!task)
         return -ESRCH;
 
     ret = PROC_I(inode)->op.proc_show(m, ns, pid, task);
 
     put_task_struct(task);
     return ret;
 }
 
 static int proc_single_open(struct inode *inode, struct file *filp)
 {
     return single_open(filp, proc_single_show, inode);
 }
 
 static const struct file_operations proc_single_file_operations = {
     .open       = proc_single_open,
     .read       = seq_read,
     .llseek     = seq_lseek,
     .release    = single_release,
 };
 
 
 struct mm_struct *proc_mem_open(struct inode *inode, unsigned int mode)
 {
     struct task_struct *task = get_proc_task(inode);
     struct mm_struct *mm = ERR_PTR(-ESRCH);
 
     if (task) {
         mm = mm_access(task, mode | PTRACE_MODE_FSCREDS);
         put_task_struct(task);
 
         if (!IS_ERR_OR_NULL(mm)) {
             /* ensure this mm_struct can't be freed */
             mmgrab(mm);
             /* but do not pin its memory */
             mmput(mm);
         }
     }
 
     return mm;
 }
 
 static int __mem_open(struct inode *inode, struct file *file, unsigned int mode)
 {
     struct mm_struct *mm = proc_mem_open(inode, mode);
 
     if (IS_ERR(mm))
         return PTR_ERR(mm);
 
     file->private_data = mm;
     return 0;
 }
 
 static int mem_open(struct inode *inode, struct file *file)
 {
     int ret = __mem_open(inode, file, PTRACE_MODE_ATTACH);
 
     /* OK to pass negative loff_t, we can catch out-of-range */
     file->f_mode |= FMODE_UNSIGNED_OFFSET;
 
     return ret;
 }
 
 static ssize_t mem_rw(struct file *file, char __user *buf,
             size_t count, loff_t *ppos, int write)
 {
     struct mm_struct *mm = file->private_data;
     unsigned long addr = *ppos;
     ssize_t copied;
     char *page;
     unsigned int flags;
 
     if (!mm)
         return 0;
 
     page = (char *)__get_free_page(GFP_KERNEL);
     if (!page)
         return -ENOMEM;
 
     copied = 0;
     if (!mmget_not_zero(mm))
         goto free;
 
     flags = FOLL_FORCE | (write ? FOLL_WRITE : 0);
 
     while (count > 0) {
         size_t this_len = min_t(size_t, count, PAGE_SIZE);
 
         if (write && copy_from_user(page, buf, this_len)) {
             copied = -EFAULT;
             break;
         }
 
         this_len = access_remote_vm(mm, addr, page, this_len, flags);
         if (!this_len) {
             if (!copied)
                 copied = -EIO;
             break;
         }
 
         if (!write && copy_to_user(buf, page, this_len)) {
             copied = -EFAULT;
             break;
         }
 
         buf += this_len;
         addr += this_len;
         copied += this_len;
         count -= this_len;
     }
     *ppos = addr;
 
     mmput(mm);
 free:
     free_page((unsigned long) page);
     return copied;
 }
 
 static ssize_t mem_read(struct file *file, char __user *buf,
             size_t count, loff_t *ppos)
 {
     return mem_rw(file, buf, count, ppos, 0);
 }
 
 static ssize_t mem_write(struct file *file, const char __user *buf,
              size_t count, loff_t *ppos)
 {
     return mem_rw(file, (char __user*)buf, count, ppos, 1);
 }
 
 loff_t mem_lseek(struct file *file, loff_t offset, int orig)
 {
     switch (orig) {
     case 0:
         file->f_pos = offset;
         break;
     case 1:
         file->f_pos += offset;
         break;
     default:
         return -EINVAL;
     }
     force_successful_syscall_return();
     return file->f_pos;
 }
 
 static int mem_release(struct inode *inode, struct file *file)
 {
     struct mm_struct *mm = file->private_data;
     if (mm)
         mmdrop(mm);
     return 0;
 }
 
 static const struct file_operations proc_mem_operations = {
     .llseek     = mem_lseek,
     .read       = mem_read,
     .write      = mem_write,
     .open       = mem_open,
     .release    = mem_release,
 };
 
 static int environ_open(struct inode *inode, struct file *file)
 {
     return __mem_open(inode, file, PTRACE_MODE_READ);
 }
 
 static ssize_t environ_read(struct file *file, char __user *buf,
             size_t count, loff_t *ppos)
 {
     char *page;
     unsigned long src = *ppos;
     int ret = 0;
     struct mm_struct *mm = file->private_data;
     unsigned long env_start, env_end;
 
     /* Ensure the process spawned far enough to have an environment. */
     if (!mm || !mm->env_end)
         return 0;
 
     page = (char *)__get_free_page(GFP_KERNEL);
     if (!page)
         return -ENOMEM;
 
     ret = 0;
     if (!mmget_not_zero(mm))
         goto free;
 
     spin_lock(&mm->arg_lock);
     env_start = mm->env_start;
     env_end = mm->env_end;
     spin_unlock(&mm->arg_lock);
 
     while (count > 0) {
         size_t this_len, max_len;
         int retval;
 
         if (src >= (env_end - env_start))
             break;
 
         this_len = env_end - (env_start + src);
 
         max_len = min_t(size_t, PAGE_SIZE, count);
         this_len = min(max_len, this_len);
 
         retval = access_remote_vm(mm, (env_start + src), page, this_len, FOLL_ANON);
 
         if (retval <= 0) {
             ret = retval;
             break;
         }
 
         if (copy_to_user(buf, page, retval)) {
             ret = -EFAULT;
             break;
         }
 
         ret += retval;
         src += retval;
         buf += retval;
         count -= retval;
     }
     *ppos = src;
     mmput(mm);
 
 free:
     free_page((unsigned long) page);
     return ret;
 }
 
 static const struct file_operations proc_environ_operations = {
     .open       = environ_open,
     .read       = environ_read,
     .llseek     = generic_file_llseek,
     .release    = mem_release,
 };
 
 static int auxv_open(struct inode *inode, struct file *file)
 {
     return __mem_open(inode, file, PTRACE_MODE_READ_FSCREDS);
 }
 
 static ssize_t auxv_read(struct file *file, char __user *buf,
             size_t count, loff_t *ppos)
 {
     struct mm_struct *mm = file->private_data;
     unsigned int nwords = 0;
 
     if (!mm)
         return 0;
     do {
         nwords += 2;
     } while (mm->saved_auxv[nwords - 2] != 0); /* AT_NULL */
     return simple_read_from_buffer(buf, count, ppos, mm->saved_auxv,
                        nwords * sizeof(mm->saved_auxv[0]));
 }
 
 static const struct file_operations proc_auxv_operations = {
     .open       = auxv_open,
     .read       = auxv_read,
     .llseek     = generic_file_llseek,
     .release    = mem_release,
 };
 
 static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
                 loff_t *ppos)
 {
     struct task_struct *task = get_proc_task(file_inode(file));
     char buffer[PROC_NUMBUF];
     int oom_adj = OOM_ADJUST_MIN;
     size_t len;
 
     if (!task)
         return -ESRCH;
     if (task->signal->oom_score_adj == OOM_SCORE_ADJ_MAX)
         oom_adj = OOM_ADJUST_MAX;
     else
         oom_adj = (task->signal->oom_score_adj * -OOM_DISABLE) /
               OOM_SCORE_ADJ_MAX;
     put_task_struct(task);
     if (oom_adj > OOM_ADJUST_MAX)
         oom_adj = OOM_ADJUST_MAX;
     len = snprintf(buffer, sizeof(buffer), "%d\n", oom_adj);
     return simple_read_from_buffer(buf, count, ppos, buffer, len);
 }
 
 static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
 {
     struct mm_struct *mm = NULL;
     struct task_struct *task;
     int err = 0;
 
     task = get_proc_task(file_inode(file));
     if (!task)
         return -ESRCH;
 
     mutex_lock(&oom_adj_mutex);
     if (legacy) {
         if (oom_adj < task->signal->oom_score_adj &&
                 !capable(CAP_SYS_RESOURCE)) {
             err = -EACCES;
             goto err_unlock;
         }
         /*
          * /proc/pid/oom_adj is provided for legacy purposes, ask users to use
          * /proc/pid/oom_score_adj instead.
          */
         pr_warn_once("%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n",
               current->comm, task_pid_nr(current), task_pid_nr(task),
               task_pid_nr(task));
     } else {
         if ((short)oom_adj < task->signal->oom_score_adj_min &&
                 !capable(CAP_SYS_RESOURCE)) {
             err = -EACCES;
             goto err_unlock;
         }
     }
 
     /*
      * Make sure we will check other processes sharing the mm if this is
      * not vfrok which wants its own oom_score_adj.
      * pin the mm so it doesn't go away and get reused after task_unlock
      */
     if (!task->vfork_done) {
         struct task_struct *p = find_lock_task_mm(task);
 
         if (p) {
             if (test_bit(MMF_MULTIPROCESS, &p->mm->flags)) {
                 mm = p->mm;
                 mmgrab(mm);
             }
             task_unlock(p);
         }
     }
 
     task->signal->oom_score_adj = oom_adj;
     if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE))
         task->signal->oom_score_adj_min = (short)oom_adj;
     trace_oom_score_adj_update(task);
 
     if (mm) {
         struct task_struct *p;
 
         rcu_read_lock();
         for_each_process(p) {
             if (same_thread_group(task, p))
                 continue;
 
             /* do not touch kernel threads or the global init */
             if (p->flags & PF_KTHREAD || is_global_init(p))
                 continue;
 
             task_lock(p);
             if (!p->vfork_done && process_shares_mm(p, mm)) {
                 p->signal->oom_score_adj = oom_adj;
                 if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE))
                     p->signal->oom_score_adj_min = (short)oom_adj;
             }
             task_unlock(p);
         }
         rcu_read_unlock();
         mmdrop(mm);
     }
 err_unlock:
     mutex_unlock(&oom_adj_mutex);
     put_task_struct(task);
     return err;
 }
 
 /*
  * /proc/pid/oom_adj exists solely for backwards compatibility with previous
  * kernels.  The effective policy is defined by oom_score_adj, which has a
  * different scale: oom_adj grew exponentially and oom_score_adj grows linearly.
  * Values written to oom_adj are simply mapped linearly to oom_score_adj.
  * Processes that become oom disabled via oom_adj will still be oom disabled
  * with this implementation.
  *
  * oom_adj cannot be removed since existing userspace binaries use it.
  */
 static ssize_t oom_adj_write(struct file *file, const char __user *buf,
                  size_t count, loff_t *ppos)
 {
     char buffer[PROC_NUMBUF];
     int oom_adj;
     int err;
 
     memset(buffer, 0, sizeof(buffer));
     if (count > sizeof(buffer) - 1)
         count = sizeof(buffer) - 1;
     if (copy_from_user(buffer, buf, count)) {
         err = -EFAULT;
         goto out;
     }
 
     err = kstrtoint(strstrip(buffer), 0, &oom_adj);
     if (err)
         goto out;
     if ((oom_adj < OOM_ADJUST_MIN || oom_adj > OOM_ADJUST_MAX) &&
          oom_adj != OOM_DISABLE) {
         err = -EINVAL;
         goto out;
     }
 
     /*
      * Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum
      * value is always attainable.
      */
     if (oom_adj == OOM_ADJUST_MAX)
         oom_adj = OOM_SCORE_ADJ_MAX;
     else
         oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
 
     err = __set_oom_adj(file, oom_adj, true);
 out:
     return err < 0 ? err : count;
 }
 
 static const struct file_operations proc_oom_adj_operations = {
     .read       = oom_adj_read,
     .write      = oom_adj_write,
     .llseek     = generic_file_llseek,
 };
 
 static ssize_t oom_score_adj_read(struct file *file, char __user *buf,
                     size_t count, loff_t *ppos)
 {
     struct task_struct *task = get_proc_task(file_inode(file));
     char buffer[PROC_NUMBUF];
     short oom_score_adj = OOM_SCORE_ADJ_MIN;
     size_t len;
 
     if (!task)
         return -ESRCH;
     oom_score_adj = task->signal->oom_score_adj;
     put_task_struct(task);
     len = snprintf(buffer, sizeof(buffer), "%hd\n", oom_score_adj);
     return simple_read_from_buffer(buf, count, ppos, buffer, len);
 }
 
 static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
                     size_t count, loff_t *ppos)
 {
     char buffer[PROC_NUMBUF];
     int oom_score_adj;
     int err;
 
     memset(buffer, 0, sizeof(buffer));
     if (count > sizeof(buffer) - 1)
         count = sizeof(buffer) - 1;
     if (copy_from_user(buffer, buf, count)) {
         err = -EFAULT;
         goto out;
     }
 
     err = kstrtoint(strstrip(buffer), 0, &oom_score_adj);
     if (err)
         goto out;
     if (oom_score_adj < OOM_SCORE_ADJ_MIN ||
             oom_score_adj > OOM_SCORE_ADJ_MAX) {
         err = -EINVAL;
         goto out;
     }
 
     err = __set_oom_adj(file, oom_score_adj, false);
 out:
     return err < 0 ? err : count;
 }
 
 static const struct file_operations proc_oom_score_adj_operations = {
     .read       = oom_score_adj_read,
     .write      = oom_score_adj_write,
     .llseek     = default_llseek,
 };
 
 #ifdef CONFIG_AUDIT
 #define TMPBUFLEN 11
 static ssize_t proc_loginuid_read(struct file * file, char __user * buf,
                   size_t count, loff_t *ppos)
 {
     struct inode * inode = file_inode(file);
     struct task_struct *task = get_proc_task(inode);
     ssize_t length;
     char tmpbuf[TMPBUFLEN];
 
     if (!task)
         return -ESRCH;
     length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
                from_kuid(file->f_cred->user_ns,
                      audit_get_loginuid(task)));
     put_task_struct(task);
     return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
 }
 
 static ssize_t proc_loginuid_write(struct file * file, const char __user * buf,
                    size_t count, loff_t *ppos)
 {
     struct inode * inode = file_inode(file);
     uid_t loginuid;
     kuid_t kloginuid;
     int rv;
 
     /* Don't let kthreads write their own loginuid */
     if (current->flags & PF_KTHREAD)
         return -EPERM;
 
     rcu_read_lock();
     if (current != pid_task(proc_pid(inode), PIDTYPE_PID)) {
         rcu_read_unlock();
         return -EPERM;
     }
     rcu_read_unlock();
 
     if (*ppos != 0) {
         /* No partial writes. */
         return -EINVAL;
     }
 
     rv = kstrtou32_from_user(buf, count, 10, &loginuid);
     if (rv < 0)
         return rv;
 
     /* is userspace tring to explicitly UNSET the loginuid? */
     if (loginuid == AUDIT_UID_UNSET) {
         kloginuid = INVALID_UID;
     } else {
         kloginuid = make_kuid(file->f_cred->user_ns, loginuid);
         if (!uid_valid(kloginuid))
             return -EINVAL;
     }
 
     rv = audit_set_loginuid(kloginuid);
     if (rv < 0)
         return rv;
     return count;
 }
 
 static const struct file_operations proc_loginuid_operations = {
     .read       = proc_loginuid_read,
     .write      = proc_loginuid_write,
     .llseek     = generic_file_llseek,
 };
 
 static ssize_t proc_sessionid_read(struct file * file, char __user * buf,
                   size_t count, loff_t *ppos)
 {
     struct inode * inode = file_inode(file);
     struct task_struct *task = get_proc_task(inode);
     ssize_t length;
     char tmpbuf[TMPBUFLEN];
 
     if (!task)
         return -ESRCH;
     length = scnprintf(tmpbuf, TMPBUFLEN, "%u",
                 audit_get_sessionid(task));
     put_task_struct(task);
     return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
 }
 
 static const struct file_operations proc_sessionid_operations = {
     .read       = proc_sessionid_read,
     .llseek     = generic_file_llseek,
 };
 #endif
 
 #ifdef CONFIG_FAULT_INJECTION
 static ssize_t proc_fault_inject_read(struct file * file, char __user * buf,
                       size_t count, loff_t *ppos)
 {
     struct task_struct *task = get_proc_task(file_inode(file));
     char buffer[PROC_NUMBUF];
     size_t len;
     int make_it_fail;
 
     if (!task)
         return -ESRCH;
     make_it_fail = task->make_it_fail;
     put_task_struct(task);
 
     len = snprintf(buffer, sizeof(buffer), "%i\n", make_it_fail);
 
     return simple_read_from_buffer(buf, count, ppos, buffer, len);
 }
 
 static ssize_t proc_fault_inject_write(struct file * file,
             const char __user * buf, size_t count, loff_t *ppos)
 {
     struct task_struct *task;
     char buffer[PROC_NUMBUF];
     int make_it_fail;
     int rv;
 
     if (!capable(CAP_SYS_RESOURCE))
         return -EPERM;
     memset(buffer, 0, sizeof(buffer));
     if (count > sizeof(buffer) - 1)
         count = sizeof(buffer) - 1;
     if (copy_from_user(buffer, buf, count))
         return -EFAULT;
     rv = kstrtoint(strstrip(buffer), 0, &make_it_fail);
     if (rv < 0)
         return rv;
     if (make_it_fail < 0 || make_it_fail > 1)
         return -EINVAL;
 
     task = get_proc_task(file_inode(file));
     if (!task)
         return -ESRCH;
     task->make_it_fail = make_it_fail;
     put_task_struct(task);
 
     return count;
 }
 
 static const struct file_operations proc_fault_inject_operations = {
     .read       = proc_fault_inject_read,
     .write      = proc_fault_inject_write,
     .llseek     = generic_file_llseek,
 };
 
 static ssize_t proc_fail_nth_write(struct file *file, const char __user *buf,
                    size_t count, loff_t *ppos)
 {
     struct task_struct *task;
     int err;
     unsigned int n;
 
     err = kstrtouint_from_user(buf, count, 0, &n);
     if (err)
         return err;
 
     task = get_proc_task(file_inode(file));
     if (!task)
         return -ESRCH;
     task->fail_nth = n;
     put_task_struct(task);
 
     return count;
 }
 
 static ssize_t proc_fail_nth_read(struct file *file, char __user *buf,
                   size_t count, loff_t *ppos)
 {
     struct task_struct *task;
     char numbuf[PROC_NUMBUF];
     ssize_t len;
 
     task = get_proc_task(file_inode(file));
     if (!task)
         return -ESRCH;
     len = snprintf(numbuf, sizeof(numbuf), "%u\n", task->fail_nth);
     put_task_struct(task);
     return simple_read_from_buffer(buf, count, ppos, numbuf, len);
 }
 
 static const struct file_operations proc_fail_nth_operations = {
     .read       = proc_fail_nth_read,
     .write      = proc_fail_nth_write,
 };
 #endif
 
 
 #ifdef CONFIG_SCHED_DEBUG
 /*
  * Print out various scheduling related per-task fields:
  */
 static int sched_show(struct seq_file *m, void *v)
 {
     struct inode *inode = m->private;
     struct pid_namespace *ns = proc_pid_ns(inode->i_sb);
     struct task_struct *p;
 
     p = get_proc_task(inode);
     if (!p)
         return -ESRCH;
     proc_sched_show_task(p, ns, m);
 
     put_task_struct(p);
 
     return 0;
 }
 
 static ssize_t
 sched_write(struct file *file, const char __user *buf,
         size_t count, loff_t *offset)
 {
     struct inode *inode = file_inode(file);
     struct task_struct *p;
 
     p = get_proc_task(inode);
     if (!p)
         return -ESRCH;
     proc_sched_set_task(p);
 
     put_task_struct(p);
 
     return count;
 }
 
 static int sched_open(struct inode *inode, struct file *filp)
 {
     return single_open(filp, sched_show, inode);
 }
 
 static const struct file_operations proc_pid_sched_operations = {
     .open       = sched_open,
     .read       = seq_read,
     .write      = sched_write,
     .llseek     = seq_lseek,
     .release    = single_release,
 };
 
 #endif
 
 #ifdef CONFIG_SCHED_AUTOGROUP
 /*
  * Print out autogroup related information:
  */
 static int sched_autogroup_show(struct seq_file *m, void *v)
 {
     struct inode *inode = m->private;
     struct task_struct *p;
 
     p = get_proc_task(inode);
     if (!p)
         return -ESRCH;
     proc_sched_autogroup_show_task(p, m);
 
     put_task_struct(p);
 
     return 0;
 }
 
 static ssize_t
 sched_autogroup_write(struct file *file, const char __user *buf,
         size_t count, loff_t *offset)
 {
     struct inode *inode = file_inode(file);
     struct task_struct *p;
     char buffer[PROC_NUMBUF];
     int nice;
     int err;
 
     memset(buffer, 0, sizeof(buffer));
     if (count > sizeof(buffer) - 1)
         count = sizeof(buffer) - 1;
     if (copy_from_user(buffer, buf, count))
         return -EFAULT;
 
     err = kstrtoint(strstrip(buffer), 0, &nice);
     if (err < 0)
         return err;
 
     p = get_proc_task(inode);
     if (!p)
         return -ESRCH;
 
     err = proc_sched_autogroup_set_nice(p, nice);
     if (err)
         count = err;
 
     put_task_struct(p);
 
     return count;
 }
 
 static int sched_autogroup_open(struct inode *inode, struct file *filp)
 {
     int ret;
 
     ret = single_open(filp, sched_autogroup_show, NULL);
     if (!ret) {
         struct seq_file *m = filp->private_data;
 
         m->private = inode;
     }
     return ret;
 }
 
 static const struct file_operations proc_pid_sched_autogroup_operations = {
     .open       = sched_autogroup_open,
     .read       = seq_read,
     .write      = sched_autogroup_write,
     .llseek     = seq_lseek,
     .release    = single_release,
 };
 
 #endif /* CONFIG_SCHED_AUTOGROUP */
 
 #ifdef CONFIG_TIME_NS
 static int timens_offsets_show(struct seq_file *m, void *v)
 {
     struct task_struct *p;
 
     p = get_proc_task(file_inode(m->file));
     if (!p)
         return -ESRCH;
     proc_timens_show_offsets(p, m);
 
     put_task_struct(p);
 
     return 0;
 }
 
 static ssize_t timens_offsets_write(struct file *file, const char __user *buf,
                     size_t count, loff_t *ppos)
 {
     struct inode *inode = file_inode(file);
     struct proc_timens_offset offsets[2];
     char *kbuf = NULL, *pos, *next_line;
     struct task_struct *p;
     int ret, noffsets;
 
     /* Only allow < page size writes at the beginning of the file */
     if ((*ppos != 0) || (count >= PAGE_SIZE))
         return -EINVAL;
 
     /* Slurp in the user data */
     kbuf = memdup_user_nul(buf, count);
     if (IS_ERR(kbuf))
         return PTR_ERR(kbuf);
 
     /* Parse the user data */
     ret = -EINVAL;
     noffsets = 0;
     for (pos = kbuf; pos; pos = next_line) {
         struct proc_timens_offset *off = &offsets[noffsets];
         char clock[10];
         int err;
 
         /* Find the end of line and ensure we don't look past it */
         next_line = strchr(pos, '\n');
         if (next_line) {
             *next_line = '\0';
             next_line++;
             if (*next_line == '\0')
                 next_line = NULL;
         }
 
         err = sscanf(pos, "%9s %lld %lu", clock,
                 &off->val.tv_sec, &off->val.tv_nsec);
         if (err != 3 || off->val.tv_nsec >= NSEC_PER_SEC)
             goto out;
 
         clock[sizeof(clock) - 1] = 0;
         if (strcmp(clock, "monotonic") == 0 ||
             strcmp(clock, __stringify(CLOCK_MONOTONIC)) == 0)
             off->clockid = CLOCK_MONOTONIC;
         else if (strcmp(clock, "boottime") == 0 ||
              strcmp(clock, __stringify(CLOCK_BOOTTIME)) == 0)
             off->clockid = CLOCK_BOOTTIME;
         else
             goto out;
 
         noffsets++;
         if (noffsets == ARRAY_SIZE(offsets)) {
             if (next_line)
                 count = next_line - kbuf;
             break;
         }
     }
 
     ret = -ESRCH;
     p = get_proc_task(inode);
     if (!p)
         goto out;
     ret = proc_timens_set_offset(file, p, offsets, noffsets);
     put_task_struct(p);
     if (ret)
         goto out;
 
     ret = count;
 out:
     kfree(kbuf);
     return ret;
 }
 
 static int timens_offsets_open(struct inode *inode, struct file *filp)
 {
     return single_open(filp, timens_offsets_show, inode);
 }
 
 static const struct file_operations proc_timens_offsets_operations = {
     .open       = timens_offsets_open,
     .read       = seq_read,
     .write      = timens_offsets_write,
     .llseek     = seq_lseek,
     .release    = single_release,
 };
 #endif /* CONFIG_TIME_NS */
 
 static ssize_t comm_write(struct file *file, const char __user *buf,
                 size_t count, loff_t *offset)
 {
     struct inode *inode = file_inode(file);
     struct task_struct *p;
     char buffer[TASK_COMM_LEN];
     const size_t maxlen = sizeof(buffer) - 1;
 
     memset(buffer, 0, sizeof(buffer));
     if (copy_from_user(buffer, buf, count > maxlen ? maxlen : count))
         return -EFAULT;
 
     p = get_proc_task(inode);
     if (!p)
         return -ESRCH;
 
     if (same_thread_group(current, p)) {
         set_task_comm(p, buffer);
         proc_comm_connector(p);
     }
     else
         count = -EINVAL;
 
     put_task_struct(p);
 
     return count;
 }
 
 static int comm_show(struct seq_file *m, void *v)
 {
     struct inode *inode = m->private;
     struct task_struct *p;
 
     p = get_proc_task(inode);
     if (!p)
         return -ESRCH;
 
     proc_task_name(m, p, false);
     seq_putc(m, '\n');
 
     put_task_struct(p);
 
     return 0;
 }
 
 static int comm_open(struct inode *inode, struct file *filp)
 {
     return single_open(filp, comm_show, inode);
 }
 
 static const struct file_operations proc_pid_set_comm_operations = {
     .open       = comm_open,
     .read       = seq_read,
     .write      = comm_write,
     .llseek     = seq_lseek,
     .release    = single_release,
 };
 
 static int proc_exe_link(struct dentry *dentry, struct path *exe_path)
 {
     struct task_struct *task;
     struct file *exe_file;
 
     task = get_proc_task(d_inode(dentry));
     if (!task)
         return -ENOENT;
     exe_file = get_task_exe_file(task);
     put_task_struct(task);
     if (exe_file) {
         *exe_path = exe_file->f_path;
         path_get(&exe_file->f_path);
         fput(exe_file);
         return 0;
     } else
         return -ENOENT;
 }
 
 static const char *proc_pid_get_link(struct dentry *dentry,
                      struct inode *inode,
                      struct delayed_call *done)
 {
     struct path path;
     int error = -EACCES;
 
     if (!dentry)
         return ERR_PTR(-ECHILD);
 
     /* Are we allowed to snoop on the tasks file descriptors? */
     if (!proc_fd_access_allowed(inode))
         goto out;
 
     error = PROC_I(inode)->op.proc_get_link(dentry, &path);
     if (error)
         goto out;
 
     error = nd_jump_link(&path);
 out:
     return ERR_PTR(error);
 }
 
 static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
 {
     char *tmp = kmalloc(PATH_MAX, GFP_KERNEL);
     char *pathname;
     int len;
 
     if (!tmp)
         return -ENOMEM;
 
     pathname = d_path(path, tmp, PATH_MAX);
     len = PTR_ERR(pathname);
     if (IS_ERR(pathname))
         goto out;
     len = tmp + PATH_MAX - 1 - pathname;
 
     if (len > buflen)
         len = buflen;
     if (copy_to_user(buffer, pathname, len))
         len = -EFAULT;
  out:
     kfree(tmp);
     return len;
 }
 
 static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int buflen)
 {
     int error = -EACCES;
     struct inode *inode = d_inode(dentry);
     struct path path;
 
     /* Are we allowed to snoop on the tasks file descriptors? */
     if (!proc_fd_access_allowed(inode))
         goto out;
 
     error = PROC_I(inode)->op.proc_get_link(dentry, &path);
     if (error)
         goto out;
 
     error = do_proc_readlink(&path, buffer, buflen);
     path_put(&path);
 out:
     return error;
 }
 
 const struct inode_operations proc_pid_link_inode_operations = {
     .readlink   = proc_pid_readlink,
     .get_link   = proc_pid_get_link,
     .setattr    = proc_setattr,
 };
 
 
 /* building an inode */
 
 void task_dump_owner(struct task_struct *task, umode_t mode,
              kuid_t *ruid, kgid_t *rgid)
 {
     /* Depending on the state of dumpable compute who should own a
      * proc file for a task.
      */
     const struct cred *cred;
     kuid_t uid;
     kgid_t gid;
 
     if (unlikely(task->flags & PF_KTHREAD)) {
         *ruid = GLOBAL_ROOT_UID;
         *rgid = GLOBAL_ROOT_GID;
         return;
     }
 
     /* Default to the tasks effective ownership */
     rcu_read_lock();
     cred = __task_cred(task);
     uid = cred->euid;
     gid = cred->egid;
     rcu_read_unlock();
 
     /*
      * Before the /proc/pid/status file was created the only way to read
      * the effective uid of a /process was to stat /proc/pid.  Reading
      * /proc/pid/status is slow enough that procps and other packages
      * kept stating /proc/pid.  To keep the rules in /proc simple I have
      * made this apply to all per process world readable and executable
      * directories.
      */
     if (mode != (S_IFDIR|S_IRUGO|S_IXUGO)) {
         struct mm_struct *mm;
         task_lock(task);
         mm = task->mm;
         /* Make non-dumpable tasks owned by some root */
         if (mm) {
             if (get_dumpable(mm) != SUID_DUMP_USER) {
                 struct user_namespace *user_ns = mm->user_ns;
 
                 uid = make_kuid(user_ns, 0);
                 if (!uid_valid(uid))
                     uid = GLOBAL_ROOT_UID;
 
                 gid = make_kgid(user_ns, 0);
                 if (!gid_valid(gid))
                     gid = GLOBAL_ROOT_GID;
             }
         } else {
             uid = GLOBAL_ROOT_UID;
             gid = GLOBAL_ROOT_GID;
         }
         task_unlock(task);
     }
     *ruid = uid;
     *rgid = gid;
 }
 
 void proc_pid_evict_inode(struct proc_inode *ei)
 {
     struct pid *pid = ei->pid;
 
     if (S_ISDIR(ei->vfs_inode.i_mode)) {
         spin_lock(&pid->lock);
         hlist_del_init_rcu(&ei->sibling_inodes);
         spin_unlock(&pid->lock);
     }
 
     put_pid(pid);
 }
 
 struct inode *proc_pid_make_inode(struct super_block *sb,
                   struct task_struct *task, umode_t mode)
 {
     struct inode * inode;
     struct proc_inode *ei;
     struct pid *pid;
 
     /* We need a new inode */
 
     inode = new_inode(sb);
     if (!inode)
         goto out;
 
     /* Common stuff */
     ei = PROC_I(inode);
     inode->i_mode = mode;
     inode->i_ino = get_next_ino();
     inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
     inode->i_op = &proc_def_inode_operations;
 
     /*
      * grab the reference to task.
      */
     pid = get_task_pid(task, PIDTYPE_PID);
     if (!pid)
         goto out_unlock;
 
     /* Let the pid remember us for quick removal */
     ei->pid = pid;
 
     task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
     security_task_to_inode(task, inode);
 
 out:
     return inode;
 
 out_unlock:
     iput(inode);
     return NULL;
 }
 
 /*
  * Generating an inode and adding it into @pid->inodes, so that task will
  * invalidate inode's dentry before being released.
  *
  * This helper is used for creating dir-type entries under '/proc' and
  * '/proc/<tgid>/task'. Other entries(eg. fd, stat) under '/proc/<tgid>'
  * can be released by invalidating '/proc/<tgid>' dentry.
  * In theory, dentries under '/proc/<tgid>/task' can also be released by
  * invalidating '/proc/<tgid>' dentry, we reserve it to handle single
  * thread exiting situation: Any one of threads should invalidate its
  * '/proc/<tgid>/task/<pid>' dentry before released.
  */
 static struct inode *proc_pid_make_base_inode(struct super_block *sb,
                 struct task_struct *task, umode_t mode)
 {
     struct inode *inode;
     struct proc_inode *ei;
     struct pid *pid;
 
     inode = proc_pid_make_inode(sb, task, mode);
     if (!inode)
         return NULL;
 
     /* Let proc_flush_pid find this directory inode */
     ei = PROC_I(inode);
     pid = ei->pid;
     spin_lock(&pid->lock);
     hlist_add_head_rcu(&ei->sibling_inodes, &pid->inodes);
     spin_unlock(&pid->lock);
 
     return inode;
 }
 
 int pid_getattr(struct user_namespace *mnt_userns, const struct path *path,
         struct kstat *stat, u32 request_mask, unsigned int query_flags)
 {
     struct inode *inode = d_inode(path->dentry);
     struct proc_fs_info *fs_info = proc_sb_info(inode->i_sb);
     struct task_struct *task;
 
     generic_fillattr(&init_user_ns, inode, stat);
 
     stat->uid = GLOBAL_ROOT_UID;
     stat->gid = GLOBAL_ROOT_GID;
     rcu_read_lock();
     task = pid_task(proc_pid(inode), PIDTYPE_PID);
     if (task) {
         if (!has_pid_permissions(fs_info, task, HIDEPID_INVISIBLE)) {
             rcu_read_unlock();
             /*
              * This doesn't prevent learning whether PID exists,
              * it only makes getattr() consistent with readdir().
              */
             return -ENOENT;
         }
         task_dump_owner(task, inode->i_mode, &stat->uid, &stat->gid);
     }
     rcu_read_unlock();
     return 0;
 }
 
 /* dentry stuff */
 
 /*
  * Set <pid>/... inode ownership (can change due to setuid(), etc.)
  */
 void pid_update_inode(struct task_struct *task, struct inode *inode)
 {
     task_dump_owner(task, inode->i_mode, &inode->i_uid, &inode->i_gid);
 
     inode->i_mode &= ~(S_ISUID | S_ISGID);
     security_task_to_inode(task, inode);
 }
 
 /*
  * Rewrite the inode's ownerships here because the owning task may have
  * performed a setuid(), etc.
  *
  */
 static int pid_revalidate(struct dentry *dentry, unsigned int flags)
 {
     struct inode *inode;
     struct task_struct *task;
     int ret = 0;
 
     rcu_read_lock();
     inode = d_inode_rcu(dentry);
     if (!inode)
         goto out;
     task = pid_task(proc_pid(inode), PIDTYPE_PID);
 
     if (task) {
         pid_update_inode(task, inode);
         ret = 1;
     }
 out:
     rcu_read_unlock();
     return ret;
 }
 
 static inline bool proc_inode_is_dead(struct inode *inode)
 {
     return !proc_pid(inode)->tasks[PIDTYPE_PID].first;
 }
 
 int pid_delete_dentry(const struct dentry *dentry)
 {
     /* Is the task we represent dead?
      * If so, then don't put the dentry on the lru list,
      * kill it immediately.
      */
     return proc_inode_is_dead(d_inode(dentry));
 }
 
 const struct dentry_operations pid_dentry_operations =
 {
     .d_revalidate   = pid_revalidate,
     .d_delete   = pid_delete_dentry,
 };
 
 /* Lookups */
 
 /*
  * Fill a directory entry.
  *
  * If possible create the dcache entry and derive our inode number and
  * file type from dcache entry.
  *
  * Since all of the proc inode numbers are dynamically generated, the inode
  * numbers do not exist until the inode is cache.  This means creating
  * the dcache entry in readdir is necessary to keep the inode numbers
  * reported by readdir in sync with the inode numbers reported
  * by stat.
  */
 bool proc_fill_cache(struct file *file, struct dir_context *ctx,
     const char *name, unsigned int len,
     instantiate_t instantiate, struct task_struct *task, const void *ptr)
 {
     struct dentry *child, *dir = file->f_path.dentry;
     struct qstr qname = QSTR_INIT(name, len);
     struct inode *inode;
     unsigned type = DT_UNKNOWN;
     ino_t ino = 1;
 
     child = d_hash_and_lookup(dir, &qname);
     if (!child) {
         DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
         child = d_alloc_parallel(dir, &qname, &wq);
         if (IS_ERR(child))
             goto end_instantiate;
         if (d_in_lookup(child)) {
             struct dentry *res;
             res = instantiate(child, task, ptr);
             d_lookup_done(child);
             if (unlikely(res)) {
                 dput(child);
                 child = res;
                 if (IS_ERR(child))
                     goto end_instantiate;
             }
         }
     }
     inode = d_inode(child);
     ino = inode->i_ino;
     type = inode->i_mode >> 12;
     dput(child);
 end_instantiate:
     return dir_emit(ctx, name, len, ino, type);
 }
 
 /*
  * dname_to_vma_addr - maps a dentry name into two unsigned longs
  * which represent vma start and end addresses.
  */
 static int dname_to_vma_addr(struct dentry *dentry,
                  unsigned long *start, unsigned long *end)
 {
     const char *str = dentry->d_name.name;
     unsigned long long sval, eval;
     unsigned int len;
 
     if (str[0] == '0' && str[1] != '-')
         return -EINVAL;
     len = _parse_integer(str, 16, &sval);
     if (len & KSTRTOX_OVERFLOW)
         return -EINVAL;
     if (sval != (unsigned long)sval)
         return -EINVAL;
     str += len;
 
     if (*str != '-')
         return -EINVAL;
     str++;
 
     if (str[0] == '0' && str[1])
         return -EINVAL;
     len = _parse_integer(str, 16, &eval);
     if (len & KSTRTOX_OVERFLOW)
         return -EINVAL;
     if (eval != (unsigned long)eval)
         return -EINVAL;
     str += len;
 
     if (*str != '\0')
         return -EINVAL;
 
     *start = sval;
     *end = eval;
 
     return 0;
 }
 
 static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags)
 {
     unsigned long vm_start, vm_end;
     bool exact_vma_exists = false;
     struct mm_struct *mm = NULL;
     struct task_struct *task;
     struct inode *inode;
     int status = 0;
 
     if (flags & LOOKUP_RCU)
         return -ECHILD;
 
     inode = d_inode(dentry);
     task = get_proc_task(inode);
     if (!task)
         goto out_notask;
 
     mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
     if (IS_ERR_OR_NULL(mm))
         goto out;
 
     if (!dname_to_vma_addr(dentry, &vm_start, &vm_end)) {
         status = mmap_read_lock_killable(mm);
         if (!status) {
             exact_vma_exists = !!find_exact_vma(mm, vm_start,
                                 vm_end);
             mmap_read_unlock(mm);
         }
     }
 
     mmput(mm);
 
     if (exact_vma_exists) {
         task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
 
         security_task_to_inode(task, inode);
         status = 1;
     }
 
 out:
     put_task_struct(task);
 
 out_notask:
     return status;
 }
 
 static const struct dentry_operations tid_map_files_dentry_operations = {
     .d_revalidate   = map_files_d_revalidate,
     .d_delete   = pid_delete_dentry,
 };
 
 static int map_files_get_link(struct dentry *dentry, struct path *path)
 {
     unsigned long vm_start, vm_end;
     struct vm_area_struct *vma;
     struct task_struct *task;
     struct mm_struct *mm;
     int rc;
 
     rc = -ENOENT;
     task = get_proc_task(d_inode(dentry));
     if (!task)
         goto out;
 
     mm = get_task_mm(task);
     put_task_struct(task);
     if (!mm)
         goto out;
 
     rc = dname_to_vma_addr(dentry, &vm_start, &vm_end);
     if (rc)
         goto out_mmput;
 
     rc = mmap_read_lock_killable(mm);
     if (rc)
         goto out_mmput;
 
     rc = -ENOENT;
     vma = find_exact_vma(mm, vm_start, vm_end);
     if (vma && vma->vm_file) {
         *path = vma->vm_file->f_path;
         path_get(path);
         rc = 0;
     }
     mmap_read_unlock(mm);
 
 out_mmput:
     mmput(mm);
 out:
     return rc;
 }
 
 struct map_files_info {
     unsigned long   start;
     unsigned long   end;
     fmode_t     mode;
 };
 
 /*
  * Only allow CAP_SYS_ADMIN and CAP_CHECKPOINT_RESTORE to follow the links, due
  * to concerns about how the symlinks may be used to bypass permissions on
  * ancestor directories in the path to the file in question.
  */
 static const char *
 proc_map_files_get_link(struct dentry *dentry,
             struct inode *inode,
                 struct delayed_call *done)
 {
     if (!checkpoint_restore_ns_capable(&init_user_ns))
         return ERR_PTR(-EPERM);
 
     return proc_pid_get_link(dentry, inode, done);
 }
 
 /*
  * Identical to proc_pid_link_inode_operations except for get_link()
  */
 static const struct inode_operations proc_map_files_link_inode_operations = {
     .readlink   = proc_pid_readlink,
     .get_link   = proc_map_files_get_link,
     .setattr    = proc_setattr,
 };
 
 static struct dentry *
 proc_map_files_instantiate(struct dentry *dentry,
                struct task_struct *task, const void *ptr)
 {
     fmode_t mode = (fmode_t)(unsigned long)ptr;
     struct proc_inode *ei;
     struct inode *inode;
 
     inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK |
                     ((mode & FMODE_READ ) ? S_IRUSR : 0) |
                     ((mode & FMODE_WRITE) ? S_IWUSR : 0));
     if (!inode)
         return ERR_PTR(-ENOENT);
 
     ei = PROC_I(inode);
     ei->op.proc_get_link = map_files_get_link;
 
     inode->i_op = &proc_map_files_link_inode_operations;
     inode->i_size = 64;
 
     d_set_d_op(dentry, &tid_map_files_dentry_operations);
     return d_splice_alias(inode, dentry);
 }
 
 static struct dentry *proc_map_files_lookup(struct inode *dir,
         struct dentry *dentry, unsigned int flags)
 {
     unsigned long vm_start, vm_end;
     struct vm_area_struct *vma;
     struct task_struct *task;
     struct dentry *result;
     struct mm_struct *mm;
 
     result = ERR_PTR(-ENOENT);
     task = get_proc_task(dir);
     if (!task)
         goto out;
 
     result = ERR_PTR(-EACCES);
     if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
         goto out_put_task;
 
     result = ERR_PTR(-ENOENT);
     if (dname_to_vma_addr(dentry, &vm_start, &vm_end))
         goto out_put_task;
 
     mm = get_task_mm(task);
     if (!mm)
         goto out_put_task;
 
     result = ERR_PTR(-EINTR);
     if (mmap_read_lock_killable(mm))
         goto out_put_mm;
 
     result = ERR_PTR(-ENOENT);
     vma = find_exact_vma(mm, vm_start, vm_end);
     if (!vma)
         goto out_no_vma;
 
     if (vma->vm_file)
         result = proc_map_files_instantiate(dentry, task,
                 (void *)(unsigned long)vma->vm_file->f_mode);
 
 out_no_vma:
     mmap_read_unlock(mm);
 out_put_mm:
     mmput(mm);
 out_put_task:
     put_task_struct(task);
 out:
     return result;
 }
 
 static const struct inode_operations proc_map_files_inode_operations = {
     .lookup     = proc_map_files_lookup,
     .permission = proc_fd_permission,
     .setattr    = proc_setattr,
 };
 
 static int
 proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 {
     struct vm_area_struct *vma;
     struct task_struct *task;
     struct mm_struct *mm;
     unsigned long nr_files, pos, i;
     GENRADIX(struct map_files_info) fa;
     struct map_files_info *p;
     int ret;
 
     genradix_init(&fa);
 
     ret = -ENOENT;
     task = get_proc_task(file_inode(file));
     if (!task)
         goto out;
 
     ret = -EACCES;
     if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
         goto out_put_task;
 
     ret = 0;
     if (!dir_emit_dots(file, ctx))
         goto out_put_task;
 
     mm = get_task_mm(task);
     if (!mm)
         goto out_put_task;
 
     ret = mmap_read_lock_killable(mm);
     if (ret) {
         mmput(mm);
         goto out_put_task;
     }
 
     nr_files = 0;
 
     /*
      * We need two passes here:
      *
      *  1) Collect vmas of mapped files with mmap_lock taken
      *  2) Release mmap_lock and instantiate entries
      *
      * otherwise we get lockdep complained, since filldir()
      * routine might require mmap_lock taken in might_fault().
      */
 
     for (vma = mm->mmap, pos = 2; vma; vma = vma->vm_next) {
         if (!vma->vm_file)
             continue;
         if (++pos <= ctx->pos)
             continue;
 
         p = genradix_ptr_alloc(&fa, nr_files++, GFP_KERNEL);
         if (!p) {
             ret = -ENOMEM;
             mmap_read_unlock(mm);
             mmput(mm);
             goto out_put_task;
         }
 
         p->start = vma->vm_start;
         p->end = vma->vm_end;
         p->mode = vma->vm_file->f_mode;
     }
     mmap_read_unlock(mm);
     mmput(mm);
 
     for (i = 0; i < nr_files; i++) {
         char buf[4 * sizeof(long) + 2]; /* max: %lx-%lx\0 */
         unsigned int len;
 
         p = genradix_ptr(&fa, i);
         len = snprintf(buf, sizeof(buf), "%lx-%lx", p->start, p->end);
         if (!proc_fill_cache(file, ctx,
                       buf, len,
                       proc_map_files_instantiate,
                       task,
                       (void *)(unsigned long)p->mode))
             break;
         ctx->pos++;
     }
 
 out_put_task:
     put_task_struct(task);
 out:
     genradix_free(&fa);
     return ret;
 }
 
 static const struct file_operations proc_map_files_operations = {
     .read       = generic_read_dir,
     .iterate_shared = proc_map_files_readdir,
     .llseek     = generic_file_llseek,
 };
 
 #if defined(CONFIG_CHECKPOINT_RESTORE) && defined(CONFIG_POSIX_TIMERS)
 struct timers_private {
     struct pid *pid;
     struct task_struct *task;
     struct sighand_struct *sighand;
     struct pid_namespace *ns;
     unsigned long flags;
 };
 
 static void *timers_start(struct seq_file *m, loff_t *pos)
 {
     struct timers_private *tp = m->private;
 
     tp->task = get_pid_task(tp->pid, PIDTYPE_PID);
     if (!tp->task)
         return ERR_PTR(-ESRCH);
 
     tp->sighand = lock_task_sighand(tp->task, &tp->flags);
     if (!tp->sighand)
         return ERR_PTR(-ESRCH);
 
     return seq_list_start(&tp->task->signal->posix_timers, *pos);
 }
 
 static void *timers_next(struct seq_file *m, void *v, loff_t *pos)
 {
     struct timers_private *tp = m->private;
     return seq_list_next(v, &tp->task->signal->posix_timers, pos);
 }
 
 static void timers_stop(struct seq_file *m, void *v)
 {
     struct timers_private *tp = m->private;
 
     if (tp->sighand) {
         unlock_task_sighand(tp->task, &tp->flags);
         tp->sighand = NULL;
     }
 
     if (tp->task) {
         put_task_struct(tp->task);
         tp->task = NULL;
     }
 }
 
 static int show_timer(struct seq_file *m, void *v)
 {
     struct k_itimer *timer;
     struct timers_private *tp = m->private;
     int notify;
     static const char * const nstr[] = {
         [SIGEV_SIGNAL] = "signal",
         [SIGEV_NONE] = "none",
         [SIGEV_THREAD] = "thread",
     };
 
     timer = list_entry((struct list_head *)v, struct k_itimer, list);
     notify = timer->it_sigev_notify;
 
     seq_printf(m, "ID: %d\n", timer->it_id);
     seq_printf(m, "signal: %d/%px\n",
            timer->sigq->info.si_signo,
            timer->sigq->info.si_value.sival_ptr);
     seq_printf(m, "notify: %s/%s.%d\n",
            nstr[notify & ~SIGEV_THREAD_ID],
            (notify & SIGEV_THREAD_ID) ? "tid" : "pid",
            pid_nr_ns(timer->it_pid, tp->ns));
     seq_printf(m, "ClockID: %d\n", timer->it_clock);
 
     return 0;
 }
 
 static const struct seq_operations proc_timers_seq_ops = {
     .start  = timers_start,
     .next   = timers_next,
     .stop   = timers_stop,
     .show   = show_timer,
 };
 
 static int proc_timers_open(struct inode *inode, struct file *file)
 {
     struct timers_private *tp;
 
     tp = __seq_open_private(file, &proc_timers_seq_ops,
             sizeof(struct timers_private));
     if (!tp)
         return -ENOMEM;
 
     tp->pid = proc_pid(inode);
     tp->ns = proc_pid_ns(inode->i_sb);
     return 0;
 }
 
 static const struct file_operations proc_timers_operations = {
     .open       = proc_timers_open,
     .read       = seq_read,
     .llseek     = seq_lseek,
     .release    = seq_release_private,
 };
 #endif
 
 static ssize_t timerslack_ns_write(struct file *file, const char __user *buf,
                     size_t count, loff_t *offset)
 {
     struct inode *inode = file_inode(file);
     struct task_struct *p;
     u64 slack_ns;
     int err;
 
     err = kstrtoull_from_user(buf, count, 10, &slack_ns);
     if (err < 0)
         return err;
 
     p = get_proc_task(inode);
     if (!p)
         return -ESRCH;
 
     if (p != current) {
         rcu_read_lock();
         if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
             rcu_read_unlock();
             count = -EPERM;
             goto out;
         }
         rcu_read_unlock();
 
         err = security_task_setscheduler(p);
         if (err) {
             count = err;
             goto out;
         }
     }
 
     task_lock(p);
     if (slack_ns == 0)
         p->timer_slack_ns = p->default_timer_slack_ns;
     else
         p->timer_slack_ns = slack_ns;
     task_unlock(p);
 
 out:
     put_task_struct(p);
 
     return count;
 }
 
 static int timerslack_ns_show(struct seq_file *m, void *v)
 {
     struct inode *inode = m->private;
     struct task_struct *p;
     int err = 0;
 
     p = get_proc_task(inode);
     if (!p)
         return -ESRCH;
 
     if (p != current) {
         rcu_read_lock();
         if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) {
             rcu_read_unlock();
             err = -EPERM;
             goto out;
         }
         rcu_read_unlock();
 
         err = security_task_getscheduler(p);
         if (err)
             goto out;
     }
 
     task_lock(p);
     seq_printf(m, "%llu\n", p->timer_slack_ns);
     task_unlock(p);
 
 out:
     put_task_struct(p);
 
     return err;
 }
 
 static int timerslack_ns_open(struct inode *inode, struct file *filp)
 {
     return single_open(filp, timerslack_ns_show, inode);
 }
 
 static const struct file_operations proc_pid_set_timerslack_ns_operations = {
     .open       = timerslack_ns_open,
     .read       = seq_read,
     .write      = timerslack_ns_write,
     .llseek     = seq_lseek,
     .release    = single_release,
 };
 
 static struct dentry *proc_pident_instantiate(struct dentry *dentry,
     struct task_struct *task, const void *ptr)
 {
     const struct pid_entry *p = ptr;
     struct inode *inode;
     struct proc_inode *ei;
 
     inode = proc_pid_make_inode(dentry->d_sb, task, p->mode);
     if (!inode)
         return ERR_PTR(-ENOENT);
 
     ei = PROC_I(inode);
     if (S_ISDIR(inode->i_mode))
         set_nlink(inode, 2);    /* Use getattr to fix if necessary */
     if (p->iop)
         inode->i_op = p->iop;
     if (p->fop)
         inode->i_fop = p->fop;
     ei->op = p->op;
     pid_update_inode(task, inode);
     d_set_d_op(dentry, &pid_dentry_operations);
     return d_splice_alias(inode, dentry);
 }
 
 static struct dentry *proc_pident_lookup(struct inode *dir, 
                      struct dentry *dentry,
                      const struct pid_entry *p,
                      const struct pid_entry *end)
 {
     struct task_struct *task = get_proc_task(dir);
     struct dentry *res = ERR_PTR(-ENOENT);
 
     if (!task)
         goto out_no_task;
 
     /*
      * Yes, it does not scale. And it should not. Don't add
      * new entries into /proc/<tgid>/ without very good reasons.
      */
     for (; p < end; p++) {
         if (p->len != dentry->d_name.len)
             continue;
         if (!memcmp(dentry->d_name.name, p->name, p->len)) {
             res = proc_pident_instantiate(dentry, task, p);
             break;
         }
     }
     put_task_struct(task);
 out_no_task:
     return res;
 }
 
 static int proc_pident_readdir(struct file *file, struct dir_context *ctx,
         const struct pid_entry *ents, unsigned int nents)
 {
     struct task_struct *task = get_proc_task(file_inode(file));
     const struct pid_entry *p;
 
     if (!task)
         return -ENOENT;
 
     if (!dir_emit_dots(file, ctx))
         goto out;
 
     if (ctx->pos >= nents + 2)
         goto out;
 
     for (p = ents + (ctx->pos - 2); p < ents + nents; p++) {
         if (!proc_fill_cache(file, ctx, p->name, p->len,
                 proc_pident_instantiate, task, p))
             break;
         ctx->pos++;
     }
 out:
     put_task_struct(task);
     return 0;
 }
 
 #ifdef CONFIG_SECURITY
 static int proc_pid_attr_open(struct inode *inode, struct file *file)
 {
     file->private_data = NULL;
     __mem_open(inode, file, PTRACE_MODE_READ_FSCREDS);
     return 0;
 }
 
 static ssize_t proc_pid_attr_read(struct file * file, char __user * buf,
                   size_t count, loff_t *ppos)
 {
     struct inode * inode = file_inode(file);
     char *p = NULL;
     ssize_t length;
     struct task_struct *task = get_proc_task(inode);
 
     if (!task)
         return -ESRCH;
 
     length = security_getprocattr(task, PROC_I(inode)->op.lsm,
                       (char*)file->f_path.dentry->d_name.name,
                       &p);
     put_task_struct(task);
     if (length > 0)
         length = simple_read_from_buffer(buf, count, ppos, p, length);
     kfree(p);
     return length;
 }
 
 static ssize_t proc_pid_attr_write(struct file * file, const char __user * buf,
                    size_t count, loff_t *ppos)
 {
     struct inode * inode = file_inode(file);
     struct task_struct *task;
     void *page;
     int rv;
 
     /* A task may only write when it was the opener. */
     if (file->private_data != current->mm)
         return -EPERM;
 
     rcu_read_lock();
     task = pid_task(proc_pid(inode), PIDTYPE_PID);
     if (!task) {
         rcu_read_unlock();
         return -ESRCH;
     }
     /* A task may only write its own attributes. */
     if (current != task) {
         rcu_read_unlock();
         return -EACCES;
     }
     /* Prevent changes to overridden credentials. */
     if (current_cred() != current_real_cred()) {
         rcu_read_unlock();
         return -EBUSY;
     }
     rcu_read_unlock();
 
     if (count > PAGE_SIZE)
         count = PAGE_SIZE;
 
     /* No partial writes. */
     if (*ppos != 0)
         return -EINVAL;
 
     page = memdup_user(buf, count);
     if (IS_ERR(page)) {
         rv = PTR_ERR(page);
         goto out;
     }
 
     /* Guard against adverse ptrace interaction */
     rv = mutex_lock_interruptible(&current->signal->cred_guard_mutex);
     if (rv < 0)
         goto out_free;
 
     rv = security_setprocattr(PROC_I(inode)->op.lsm,
                   file->f_path.dentry->d_name.name, page,
                   count);
     mutex_unlock(&current->signal->cred_guard_mutex);
 out_free:
     kfree(page);
 out:
     return rv;
 }
 
 static const struct file_operations proc_pid_attr_operations = {
     .open       = proc_pid_attr_open,
     .read       = proc_pid_attr_read,
     .write      = proc_pid_attr_write,
     .llseek     = generic_file_llseek,
     .release    = mem_release,
 };
 
 #define LSM_DIR_OPS(LSM) \
 static int proc_##LSM##_attr_dir_iterate(struct file *filp, \
                  struct dir_context *ctx) \
 { \
     return proc_pident_readdir(filp, ctx, \
                    LSM##_attr_dir_stuff, \
                    ARRAY_SIZE(LSM##_attr_dir_stuff)); \
 } \
 \
 static const struct file_operations proc_##LSM##_attr_dir_ops = { \
     .read       = generic_read_dir, \
     .iterate    = proc_##LSM##_attr_dir_iterate, \
     .llseek     = default_llseek, \
 }; \
 \
 static struct dentry *proc_##LSM##_attr_dir_lookup(struct inode *dir, \
                 struct dentry *dentry, unsigned int flags) \
 { \
     return proc_pident_lookup(dir, dentry, \
                   LSM##_attr_dir_stuff, \
                   LSM##_attr_dir_stuff + ARRAY_SIZE(LSM##_attr_dir_stuff)); \
 } \
 \
 static const struct inode_operations proc_##LSM##_attr_dir_inode_ops = { \
     .lookup     = proc_##LSM##_attr_dir_lookup, \
     .getattr    = pid_getattr, \
     .setattr    = proc_setattr, \
 }
 
 #ifdef CONFIG_SECURITY_SMACK
 static const struct pid_entry smack_attr_dir_stuff[] = {
     ATTR("smack", "current",    0666),
 };
 LSM_DIR_OPS(smack);
 #endif
 
 #ifdef CONFIG_SECURITY_APPARMOR
 static const struct pid_entry apparmor_attr_dir_stuff[] = {
     ATTR("apparmor", "current", 0666),
     ATTR("apparmor", "prev",    0444),
     ATTR("apparmor", "exec",    0666),
 };
 LSM_DIR_OPS(apparmor);
 #endif
 
 static const struct pid_entry attr_dir_stuff[] = {
     ATTR(NULL, "current",       0666),
     ATTR(NULL, "prev",      0444),
     ATTR(NULL, "exec",      0666),
     ATTR(NULL, "fscreate",      0666),
     ATTR(NULL, "keycreate",     0666),
     ATTR(NULL, "sockcreate",    0666),
 #ifdef CONFIG_SECURITY_SMACK
     DIR("smack",            0555,
         proc_smack_attr_dir_inode_ops, proc_smack_attr_dir_ops),
 #endif
 #ifdef CONFIG_SECURITY_APPARMOR
     DIR("apparmor",         0555,
         proc_apparmor_attr_dir_inode_ops, proc_apparmor_attr_dir_ops),
 #endif
 };
 
 static int proc_attr_dir_readdir(struct file *file, struct dir_context *ctx)
 {
     return proc_pident_readdir(file, ctx, 
                    attr_dir_stuff, ARRAY_SIZE(attr_dir_stuff));
 }
 
 static const struct file_operations proc_attr_dir_operations = {
     .read       = generic_read_dir,
     .iterate_shared = proc_attr_dir_readdir,
     .llseek     = generic_file_llseek,
 };
 
 static struct dentry *proc_attr_dir_lookup(struct inode *dir,
                 struct dentry *dentry, unsigned int flags)
 {
     return proc_pident_lookup(dir, dentry,
                   attr_dir_stuff,
                   attr_dir_stuff + ARRAY_SIZE(attr_dir_stuff));
 }
 
 static const struct inode_operations proc_attr_dir_inode_operations = {
     .lookup     = proc_attr_dir_lookup,
     .getattr    = pid_getattr,
     .setattr    = proc_setattr,
 };
 
 #endif
 
 #ifdef CONFIG_ELF_CORE
 static ssize_t proc_coredump_filter_read(struct file *file, char __user *buf,
                      size_t count, loff_t *ppos)
 {
     struct task_struct *task = get_proc_task(file_inode(file));
     struct mm_struct *mm;
     char buffer[PROC_NUMBUF];
     size_t len;
     int ret;
 
     if (!task)
         return -ESRCH;
 
     ret = 0;
     mm = get_task_mm(task);
     if (mm) {
         len = snprintf(buffer, sizeof(buffer), "%08lx\n",
                    ((mm->flags & MMF_DUMP_FILTER_MASK) >>
                 MMF_DUMP_FILTER_SHIFT));
         mmput(mm);
         ret = simple_read_from_buffer(buf, count, ppos, buffer, len);
     }
 
     put_task_struct(task);
 
     return ret;
 }
 
 static ssize_t proc_coredump_filter_write(struct file *file,
                       const char __user *buf,
                       size_t count,
                       loff_t *ppos)
 {
     struct task_struct *task;
     struct mm_struct *mm;
     unsigned int val;
     int ret;
     int i;
     unsigned long mask;
 
     ret = kstrtouint_from_user(buf, count, 0, &val);
     if (ret < 0)
         return ret;
 
     ret = -ESRCH;
     task = get_proc_task(file_inode(file));
     if (!task)
         goto out_no_task;
 
     mm = get_task_mm(task);
     if (!mm)
         goto out_no_mm;
     ret = 0;
 
     for (i = 0, mask = 1; i < MMF_DUMP_FILTER_BITS; i++, mask <<= 1) {
         if (val & mask)
             set_bit(i + MMF_DUMP_FILTER_SHIFT, &mm->flags);
         else
             clear_bit(i + MMF_DUMP_FILTER_SHIFT, &mm->flags);
     }
 
     mmput(mm);
  out_no_mm:
     put_task_struct(task);
  out_no_task:
     if (ret < 0)
         return ret;
     return count;
 }
 
 static const struct file_operations proc_coredump_filter_operations = {
     .read       = proc_coredump_filter_read,
     .write      = proc_coredump_filter_write,
     .llseek     = generic_file_llseek,
 };
 #endif
 
 #ifdef CONFIG_TASK_IO_ACCOUNTING
 static int do_io_accounting(struct task_struct *task, struct seq_file *m, int whole)
 {
     struct task_io_accounting acct = task->ioac;
     unsigned long flags;
     int result;
 
     result = down_read_killable(&task->signal->exec_update_lock);
     if (result)
         return result;
 
     if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
         result = -EACCES;
         goto out_unlock;
     }
 
     if (whole && lock_task_sighand(task, &flags)) {
         struct task_struct *t = task;
 
         task_io_accounting_add(&acct, &task->signal->ioac);
         while_each_thread(task, t)
             task_io_accounting_add(&acct, &t->ioac);
 
         unlock_task_sighand(task, &flags);
     }
     seq_printf(m,
            "rchar: %llu\n"
            "wchar: %llu\n"
            "syscr: %llu\n"
            "syscw: %llu\n"
            "read_bytes: %llu\n"
            "write_bytes: %llu\n"
            "cancelled_write_bytes: %llu\n",
            (unsigned long long)acct.rchar,
            (unsigned long long)acct.wchar,
            (unsigned long long)acct.syscr,
            (unsigned long long)acct.syscw,
            (unsigned long long)acct.read_bytes,
            (unsigned long long)acct.write_bytes,
            (unsigned long long)acct.cancelled_write_bytes);
     result = 0;
 
 out_unlock:
     up_read(&task->signal->exec_update_lock);
     return result;
 }
 
 static int proc_tid_io_accounting(struct seq_file *m, struct pid_namespace *ns,
                   struct pid *pid, struct task_struct *task)
 {
     return do_io_accounting(task, m, 0);
 }
 
 static int proc_tgid_io_accounting(struct seq_file *m, struct pid_namespace *ns,
                    struct pid *pid, struct task_struct *task)
 {
     return do_io_accounting(task, m, 1);
 }
 #endif /* CONFIG_TASK_IO_ACCOUNTING */
 
 #ifdef CONFIG_USER_NS
 static int proc_id_map_open(struct inode *inode, struct file *file,
     const struct seq_operations *seq_ops)
 {
     struct user_namespace *ns = NULL;
     struct task_struct *task;
     struct seq_file *seq;
     int ret = -EINVAL;
 
     task = get_proc_task(inode);
     if (task) {
         rcu_read_lock();
         ns = get_user_ns(task_cred_xxx(task, user_ns));
         rcu_read_unlock();
         put_task_struct(task);
     }
     if (!ns)
         goto err;
 
     ret = seq_open(file, seq_ops);
     if (ret)
         goto err_put_ns;
 
     seq = file->private_data;
     seq->private = ns;
 
     return 0;
 err_put_ns:
     put_user_ns(ns);
 err:
     return ret;
 }
 
 static int proc_id_map_release(struct inode *inode, struct file *file)
 {
     struct seq_file *seq = file->private_data;
     struct user_namespace *ns = seq->private;
     put_user_ns(ns);
     return seq_release(inode, file);
 }
 
 static int proc_uid_map_open(struct inode *inode, struct file *file)
 {
     return proc_id_map_open(inode, file, &proc_uid_seq_operations);
 }
 
 static int proc_gid_map_open(struct inode *inode, struct file *file)
 {
     return proc_id_map_open(inode, file, &proc_gid_seq_operations);
 }
 
 static int proc_projid_map_open(struct inode *inode, struct file *file)
 {
     return proc_id_map_open(inode, file, &proc_projid_seq_operations);
 }
 
 static const struct file_operations proc_uid_map_operations = {
     .open       = proc_uid_map_open,
     .write      = proc_uid_map_write,
     .read       = seq_read,
     .llseek     = seq_lseek,
     .release    = proc_id_map_release,
 };
 
 static const struct file_operations proc_gid_map_operations = {
     .open       = proc_gid_map_open,
     .write      = proc_gid_map_write,
     .read       = seq_read,
     .llseek     = seq_lseek,
     .release    = proc_id_map_release,
 };
 
 static const struct file_operations proc_projid_map_operations = {
     .open       = proc_projid_map_open,
     .write      = proc_projid_map_write,
     .read       = seq_read,
     .llseek     = seq_lseek,
     .release    = proc_id_map_release,
 };
 
 static int proc_setgroups_open(struct inode *inode, struct file *file)
 {
     struct user_namespace *ns = NULL;
     struct task_struct *task;
     int ret;
 
     ret = -ESRCH;
     task = get_proc_task(inode);
     if (task) {
         rcu_read_lock();
         ns = get_user_ns(task_cred_xxx(task, user_ns));
         rcu_read_unlock();
         put_task_struct(task);
     }
     if (!ns)
         goto err;
 
     if (file->f_mode & FMODE_WRITE) {
         ret = -EACCES;
         if (!ns_capable(ns, CAP_SYS_ADMIN))
             goto err_put_ns;
     }
 
     ret = single_open(file, &proc_setgroups_show, ns);
     if (ret)
         goto err_put_ns;
 
     return 0;
 err_put_ns:
     put_user_ns(ns);
 err:
     return ret;
 }
 
 static int proc_setgroups_release(struct inode *inode, struct file *file)
 {
     struct seq_file *seq = file->private_data;
     struct user_namespace *ns = seq->private;
     int ret = single_release(inode, file);
     put_user_ns(ns);
     return ret;
 }
 
 static const struct file_operations proc_setgroups_operations = {
     .open       = proc_setgroups_open,
     .write      = proc_setgroups_write,
     .read       = seq_read,
     .llseek     = seq_lseek,
     .release    = proc_setgroups_release,
 };
 #endif /* CONFIG_USER_NS */
 
 static int proc_pid_personality(struct seq_file *m, struct pid_namespace *ns,
                 struct pid *pid, struct task_struct *task)
 {
     int err = lock_trace(task);
     if (!err) {
         seq_printf(m, "%08x\n", task->personality);
         unlock_trace(task);
     }
     return err;
 }
 
 #ifdef CONFIG_LIVEPATCH
 static int proc_pid_patch_state(struct seq_file *m, struct pid_namespace *ns,
                 struct pid *pid, struct task_struct *task)
 {
     seq_printf(m, "%d\n", task->patch_state);
     return 0;
 }
 #endif /* CONFIG_LIVEPATCH */
 
 #ifdef CONFIG_KSM
 static int proc_pid_ksm_merging_pages(struct seq_file *m, struct pid_namespace *ns,
                 struct pid *pid, struct task_struct *task)
 {
     struct mm_struct *mm;
 
     mm = get_task_mm(task);
     if (mm) {
         seq_printf(m, "%lu\n", mm->ksm_merging_pages);
         mmput(mm);
     }
 
     return 0;
 }
 #endif /* CONFIG_KSM */
 
 #ifdef CONFIG_STACKLEAK_METRICS
 static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns,
                 struct pid *pid, struct task_struct *task)
 {
     unsigned long prev_depth = THREAD_SIZE -
                 (task->prev_lowest_stack & (THREAD_SIZE - 1));
     unsigned long depth = THREAD_SIZE -
                 (task->lowest_stack & (THREAD_SIZE - 1));
 
     seq_printf(m, "previous stack depth: %lu\nstack depth: %lu\n",
                             prev_depth, depth);
     return 0;
 }
 #endif /* CONFIG_STACKLEAK_METRICS */
 
 /*
  * Thread groups
  */
 static const struct file_operations proc_task_operations;
 static const struct inode_operations proc_task_inode_operations;
 
 static const struct pid_entry tgid_base_stuff[] = {
     DIR("task",       S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations),
     DIR("fd",         S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
     DIR("map_files",  S_IRUSR|S_IXUSR, proc_map_files_inode_operations, proc_map_files_operations),
     DIR("fdinfo",     S_IRUGO|S_IXUGO, proc_fdinfo_inode_operations, proc_fdinfo_operations),
     DIR("ns",     S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
 #ifdef CONFIG_NET
     DIR("net",        S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations),
 #endif
     REG("environ",    S_IRUSR, proc_environ_operations),
     REG("auxv",       S_IRUSR, proc_auxv_operations),
     ONE("status",     S_IRUGO, proc_pid_status),
     ONE("personality", S_IRUSR, proc_pid_personality),
     ONE("limits",     S_IRUGO, proc_pid_limits),
 #ifdef CONFIG_SCHED_DEBUG
     REG("sched",      S_IRUGO|S_IWUSR, proc_pid_sched_operations),
 #endif
 #ifdef CONFIG_SCHED_AUTOGROUP
     REG("autogroup",  S_IRUGO|S_IWUSR, proc_pid_sched_autogroup_operations),
 #endif
 #ifdef CONFIG_TIME_NS
     REG("timens_offsets",  S_IRUGO|S_IWUSR, proc_timens_offsets_operations),
 #endif
     REG("comm",      S_IRUGO|S_IWUSR, proc_pid_set_comm_operations),
 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
     ONE("syscall",    S_IRUSR, proc_pid_syscall),
 #endif
     REG("cmdline",    S_IRUGO, proc_pid_cmdline_ops),
     ONE("stat",       S_IRUGO, proc_tgid_stat),
     ONE("statm",      S_IRUGO, proc_pid_statm),
     REG("maps",       S_IRUGO, proc_pid_maps_operations),
 #ifdef CONFIG_NUMA
     REG("numa_maps",  S_IRUGO, proc_pid_numa_maps_operations),
 #endif
     REG("mem",        S_IRUSR|S_IWUSR, proc_mem_operations),
     LNK("cwd",        proc_cwd_link),
     LNK("root",       proc_root_link),
     LNK("exe",        proc_exe_link),
     REG("mounts",     S_IRUGO, proc_mounts_operations),
     REG("mountinfo",  S_IRUGO, proc_mountinfo_operations),
     REG("mountstats", S_IRUSR, proc_mountstats_operations),
 #ifdef CONFIG_PROC_PAGE_MONITOR
     REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
     REG("smaps",      S_IRUGO, proc_pid_smaps_operations),
     REG("smaps_rollup", S_IRUGO, proc_pid_smaps_rollup_operations),
     REG("pagemap",    S_IRUSR, proc_pagemap_operations),
 #endif
 #ifdef CONFIG_SECURITY
     DIR("attr",       S_IRUGO|S_IXUGO, proc_attr_dir_inode_operations, proc_attr_dir_operations),
 #endif
 #ifdef CONFIG_KALLSYMS
     ONE("wchan",      S_IRUGO, proc_pid_wchan),
 #endif
 #ifdef CONFIG_STACKTRACE
     ONE("stack",      S_IRUSR, proc_pid_stack),
 #endif
 #ifdef CONFIG_SCHED_INFO
     ONE("schedstat",  S_IRUGO, proc_pid_schedstat),
 #endif
 #ifdef CONFIG_LATENCYTOP
     REG("latency",  S_IRUGO, proc_lstats_operations),
 #endif
 #ifdef CONFIG_PROC_PID_CPUSET
     ONE("cpuset",     S_IRUGO, proc_cpuset_show),
 #endif
 #ifdef CONFIG_CGROUPS
     ONE("cgroup",  S_IRUGO, proc_cgroup_show),
 #endif
 #ifdef CONFIG_PROC_CPU_RESCTRL
     ONE("cpu_resctrl_groups", S_IRUGO, proc_resctrl_show),
 #endif
     ONE("oom_score",  S_IRUGO, proc_oom_score),
     REG("oom_adj",    S_IRUGO|S_IWUSR, proc_oom_adj_operations),
     REG("oom_score_adj", S_IRUGO|S_IWUSR, proc_oom_score_adj_operations),
 #ifdef CONFIG_AUDIT
     REG("loginuid",   S_IWUSR|S_IRUGO, proc_loginuid_operations),
     REG("sessionid",  S_IRUGO, proc_sessionid_operations),
 #endif
 #ifdef CONFIG_FAULT_INJECTION
     REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
     REG("fail-nth", 0644, proc_fail_nth_operations),
 #endif
 #ifdef CONFIG_ELF_CORE
     REG("coredump_filter", S_IRUGO|S_IWUSR, proc_coredump_filter_operations),
 #endif
 #ifdef CONFIG_TASK_IO_ACCOUNTING
     ONE("io",   S_IRUSR, proc_tgid_io_accounting),
 #endif
 #ifdef CONFIG_USER_NS
     REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
     REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
     REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
     REG("setgroups",  S_IRUGO|S_IWUSR, proc_setgroups_operations),
 #endif
 #if defined(CONFIG_CHECKPOINT_RESTORE) && defined(CONFIG_POSIX_TIMERS)
     REG("timers",     S_IRUGO, proc_timers_operations),
 #endif
     REG("timerslack_ns", S_IRUGO|S_IWUGO, proc_pid_set_timerslack_ns_operations),
 #ifdef CONFIG_LIVEPATCH
     ONE("patch_state",  S_IRUSR, proc_pid_patch_state),
 #endif
 #ifdef CONFIG_STACKLEAK_METRICS
     ONE("stack_depth", S_IRUGO, proc_stack_depth),
 #endif
 #ifdef CONFIG_PROC_PID_ARCH_STATUS
     ONE("arch_status", S_IRUGO, proc_pid_arch_status),
 #endif
 #ifdef CONFIG_SECCOMP_CACHE_DEBUG
     ONE("seccomp_cache", S_IRUSR, proc_pid_seccomp_cache),
 #endif
 #ifdef CONFIG_KSM
     ONE("ksm_merging_pages",  S_IRUSR, proc_pid_ksm_merging_pages),
 #endif
 };
 
 static int proc_tgid_base_readdir(struct file *file, struct dir_context *ctx)
 {
     return proc_pident_readdir(file, ctx,
                    tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff));
 }
 
 static const struct file_operations proc_tgid_base_operations = {
     .read       = generic_read_dir,
     .iterate_shared = proc_tgid_base_readdir,
     .llseek     = generic_file_llseek,
 };
 
 struct pid *tgid_pidfd_to_pid(const struct file *file)
 {
     if (file->f_op != &proc_tgid_base_operations)
         return ERR_PTR(-EBADF);
 
     return proc_pid(file_inode(file));
 }
 
 static struct dentry *proc_tgid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 {
     return proc_pident_lookup(dir, dentry,
                   tgid_base_stuff,
                   tgid_base_stuff + ARRAY_SIZE(tgid_base_stuff));
 }
 
 static const struct inode_operations proc_tgid_base_inode_operations = {
     .lookup     = proc_tgid_base_lookup,
     .getattr    = pid_getattr,
     .setattr    = proc_setattr,
     .permission = proc_pid_permission,
 };
 
 /**
  * proc_flush_pid -  Remove dcache entries for @pid from the /proc dcache.
  * @pid: pid that should be flushed.
  *
  * This function walks a list of inodes (that belong to any proc
  * filesystem) that are attached to the pid and flushes them from
  * the dentry cache.
  *
  * It is safe and reasonable to cache /proc entries for a task until
  * that task exits.  After that they just clog up the dcache with
  * useless entries, possibly causing useful dcache entries to be
  * flushed instead.  This routine is provided to flush those useless
  * dcache entries when a process is reaped.
  *
  * NOTE: This routine is just an optimization so it does not guarantee
  *       that no dcache entries will exist after a process is reaped
  *       it just makes it very unlikely that any will persist.
  */
 
 void proc_flush_pid(struct pid *pid)
 {
     proc_invalidate_siblings_dcache(&pid->inodes, &pid->lock);
 }
 
 static struct dentry *proc_pid_instantiate(struct dentry * dentry,
                    struct task_struct *task, const void *ptr)
 {
     struct inode *inode;
 
     inode = proc_pid_make_base_inode(dentry->d_sb, task,
                      S_IFDIR | S_IRUGO | S_IXUGO);
     if (!inode)
         return ERR_PTR(-ENOENT);
 
     inode->i_op = &proc_tgid_base_inode_operations;
     inode->i_fop = &proc_tgid_base_operations;
     inode->i_flags|=S_IMMUTABLE;
 
     set_nlink(inode, nlink_tgid);
     pid_update_inode(task, inode);
 
     d_set_d_op(dentry, &pid_dentry_operations);
     return d_splice_alias(inode, dentry);
 }
 
 struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags)
 {
     struct task_struct *task;
     unsigned tgid;
     struct proc_fs_info *fs_info;
     struct pid_namespace *ns;
     struct dentry *result = ERR_PTR(-ENOENT);
 
     tgid = name_to_int(&dentry->d_name);
     if (tgid == ~0U)
         goto out;
 
     fs_info = proc_sb_info(dentry->d_sb);
     ns = fs_info->pid_ns;
     rcu_read_lock();
     task = find_task_by_pid_ns(tgid, ns);
     if (task)
         get_task_struct(task);
     rcu_read_unlock();
     if (!task)
         goto out;
 
     /* Limit procfs to only ptraceable tasks */
     if (fs_info->hide_pid == HIDEPID_NOT_PTRACEABLE) {
         if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS))
             goto out_put_task;
     }
 
     result = proc_pid_instantiate(dentry, task, NULL);
 out_put_task:
     put_task_struct(task);
 out:
     return result;
 }
 
 /*
  * Find the first task with tgid >= tgid
  *
  */
 struct tgid_iter {
     unsigned int tgid;
     struct task_struct *task;
 };
 static struct tgid_iter next_tgid(struct pid_namespace *ns, struct tgid_iter iter)
 {
     struct pid *pid;
 
     if (iter.task)
         put_task_struct(iter.task);
     rcu_read_lock();
 retry:
     iter.task = NULL;
     pid = find_ge_pid(iter.tgid, ns);
     if (pid) {
         iter.tgid = pid_nr_ns(pid, ns);
         iter.task = pid_task(pid, PIDTYPE_TGID);
         if (!iter.task) {
             iter.tgid += 1;
             goto retry;
         }
         get_task_struct(iter.task);
     }
     rcu_read_unlock();
     return iter;
 }
 
 #define TGID_OFFSET (FIRST_PROCESS_ENTRY + 2)
 
 /* for the /proc/ directory itself, after non-process stuff has been done */
 int proc_pid_readdir(struct file *file, struct dir_context *ctx)
 {
     struct tgid_iter iter;
     struct proc_fs_info *fs_info = proc_sb_info(file_inode(file)->i_sb);
     struct pid_namespace *ns = proc_pid_ns(file_inode(file)->i_sb);
     loff_t pos = ctx->pos;
 
     if (pos >= PID_MAX_LIMIT + TGID_OFFSET)
         return 0;
 
     if (pos == TGID_OFFSET - 2) {
         struct inode *inode = d_inode(fs_info->proc_self);
         if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK))
             return 0;
         ctx->pos = pos = pos + 1;
     }
     if (pos == TGID_OFFSET - 1) {
         struct inode *inode = d_inode(fs_info->proc_thread_self);
         if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK))
             return 0;
         ctx->pos = pos = pos + 1;
     }
     iter.tgid = pos - TGID_OFFSET;
     iter.task = NULL;
     for (iter = next_tgid(ns, iter);
          iter.task;
          iter.tgid += 1, iter = next_tgid(ns, iter)) {
         char name[10 + 1];
         unsigned int len;
 
         cond_resched();
         if (!has_pid_permissions(fs_info, iter.task, HIDEPID_INVISIBLE))
             continue;
 
         len = snprintf(name, sizeof(name), "%u", iter.tgid);
         ctx->pos = iter.tgid + TGID_OFFSET;
         if (!proc_fill_cache(file, ctx, name, len,
                      proc_pid_instantiate, iter.task, NULL)) {
             put_task_struct(iter.task);
             return 0;
         }
     }
     ctx->pos = PID_MAX_LIMIT + TGID_OFFSET;
     return 0;
 }
 
 /*
  * proc_tid_comm_permission is a special permission function exclusively
  * used for the node /proc/<pid>/task/<tid>/comm.
  * It bypasses generic permission checks in the case where a task of the same
  * task group attempts to access the node.
  * The rationale behind this is that glibc and bionic access this node for
  * cross thread naming (pthread_set/getname_np(!self)). However, if
  * PR_SET_DUMPABLE gets set to 0 this node among others becomes uid=0 gid=0,
  * which locks out the cross thread naming implementation.
  * This function makes sure that the node is always accessible for members of
  * same thread group.
  */
 static int proc_tid_comm_permission(struct user_namespace *mnt_userns,
                     struct inode *inode, int mask)
 {
     bool is_same_tgroup;
     struct task_struct *task;
 
     task = get_proc_task(inode);
     if (!task)
         return -ESRCH;
     is_same_tgroup = same_thread_group(current, task);
     put_task_struct(task);
 
     if (likely(is_same_tgroup && !(mask & MAY_EXEC))) {
         /* This file (/proc/<pid>/task/<tid>/comm) can always be
          * read or written by the members of the corresponding
          * thread group.
          */
         return 0;
     }
 
     return generic_permission(&init_user_ns, inode, mask);
 }
 
 static const struct inode_operations proc_tid_comm_inode_operations = {
         .permission = proc_tid_comm_permission,
 };
 
 /*
  * Tasks
  */
 static const struct pid_entry tid_base_stuff[] = {
     DIR("fd",        S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations),
     DIR("fdinfo",    S_IRUGO|S_IXUGO, proc_fdinfo_inode_operations, proc_fdinfo_operations),
     DIR("ns",    S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations),
 #ifdef CONFIG_NET
     DIR("net",        S_IRUGO|S_IXUGO, proc_net_inode_operations, proc_net_operations),
 #endif
     REG("environ",   S_IRUSR, proc_environ_operations),
     REG("auxv",      S_IRUSR, proc_auxv_operations),
     ONE("status",    S_IRUGO, proc_pid_status),
     ONE("personality", S_IRUSR, proc_pid_personality),
     ONE("limits",    S_IRUGO, proc_pid_limits),
 #ifdef CONFIG_SCHED_DEBUG
     REG("sched",     S_IRUGO|S_IWUSR, proc_pid_sched_operations),
 #endif
     NOD("comm",      S_IFREG|S_IRUGO|S_IWUSR,
              &proc_tid_comm_inode_operations,
              &proc_pid_set_comm_operations, {}),
 #ifdef CONFIG_HAVE_ARCH_TRACEHOOK
     ONE("syscall",   S_IRUSR, proc_pid_syscall),
 #endif
     REG("cmdline",   S_IRUGO, proc_pid_cmdline_ops),
     ONE("stat",      S_IRUGO, proc_tid_stat),
     ONE("statm",     S_IRUGO, proc_pid_statm),
     REG("maps",      S_IRUGO, proc_pid_maps_operations),
 #ifdef CONFIG_PROC_CHILDREN
     REG("children",  S_IRUGO, proc_tid_children_operations),
 #endif
 #ifdef CONFIG_NUMA
     REG("numa_maps", S_IRUGO, proc_pid_numa_maps_operations),
 #endif
     REG("mem",       S_IRUSR|S_IWUSR, proc_mem_operations),
     LNK("cwd",       proc_cwd_link),
     LNK("root",      proc_root_link),
     LNK("exe",       proc_exe_link),
     REG("mounts",    S_IRUGO, proc_mounts_operations),
     REG("mountinfo",  S_IRUGO, proc_mountinfo_operations),
 #ifdef CONFIG_PROC_PAGE_MONITOR
     REG("clear_refs", S_IWUSR, proc_clear_refs_operations),
     REG("smaps",     S_IRUGO, proc_pid_smaps_operations),
     REG("smaps_rollup", S_IRUGO, proc_pid_smaps_rollup_operations),
     REG("pagemap",    S_IRUSR, proc_pagemap_operations),
 #endif
 #ifdef CONFIG_SECURITY
     DIR("attr",      S_IRUGO|S_IXUGO, proc_attr_dir_inode_operations, proc_attr_dir_operations),
 #endif
 #ifdef CONFIG_KALLSYMS
     ONE("wchan",     S_IRUGO, proc_pid_wchan),
 #endif
 #ifdef CONFIG_STACKTRACE
     ONE("stack",      S_IRUSR, proc_pid_stack),
 #endif
 #ifdef CONFIG_SCHED_INFO
     ONE("schedstat", S_IRUGO, proc_pid_schedstat),
 #endif
 #ifdef CONFIG_LATENCYTOP
     REG("latency",  S_IRUGO, proc_lstats_operations),
 #endif
 #ifdef CONFIG_PROC_PID_CPUSET
     ONE("cpuset",    S_IRUGO, proc_cpuset_show),
 #endif
 #ifdef CONFIG_CGROUPS
     ONE("cgroup",  S_IRUGO, proc_cgroup_show),
 #endif
 #ifdef CONFIG_PROC_CPU_RESCTRL
     ONE("cpu_resctrl_groups", S_IRUGO, proc_resctrl_show),
 #endif
     ONE("oom_score", S_IRUGO, proc_oom_score),
     REG("oom_adj",   S_IRUGO|S_IWUSR, proc_oom_adj_operations),
     REG("oom_score_adj", S_IRUGO|S_IWUSR, proc_oom_score_adj_operations),
 #ifdef CONFIG_AUDIT
     REG("loginuid",  S_IWUSR|S_IRUGO, proc_loginuid_operations),
     REG("sessionid",  S_IRUGO, proc_sessionid_operations),
 #endif
 #ifdef CONFIG_FAULT_INJECTION
     REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
     REG("fail-nth", 0644, proc_fail_nth_operations),
 #endif
 #ifdef CONFIG_TASK_IO_ACCOUNTING
     ONE("io",   S_IRUSR, proc_tid_io_accounting),
 #endif
 #ifdef CONFIG_USER_NS
     REG("uid_map",    S_IRUGO|S_IWUSR, proc_uid_map_operations),
     REG("gid_map",    S_IRUGO|S_IWUSR, proc_gid_map_operations),
     REG("projid_map", S_IRUGO|S_IWUSR, proc_projid_map_operations),
     REG("setgroups",  S_IRUGO|S_IWUSR, proc_setgroups_operations),
 #endif
 #ifdef CONFIG_LIVEPATCH
     ONE("patch_state",  S_IRUSR, proc_pid_patch_state),
 #endif
 #ifdef CONFIG_PROC_PID_ARCH_STATUS
     ONE("arch_status", S_IRUGO, proc_pid_arch_status),
 #endif
 #ifdef CONFIG_SECCOMP_CACHE_DEBUG
     ONE("seccomp_cache", S_IRUSR, proc_pid_seccomp_cache),
 #endif
 #ifdef CONFIG_KSM
     ONE("ksm_merging_pages",  S_IRUSR, proc_pid_ksm_merging_pages),
 #endif
 };
 
 static int proc_tid_base_readdir(struct file *file, struct dir_context *ctx)
 {
     return proc_pident_readdir(file, ctx,
                    tid_base_stuff, ARRAY_SIZE(tid_base_stuff));
 }
 
 static struct dentry *proc_tid_base_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
 {
     return proc_pident_lookup(dir, dentry,
                   tid_base_stuff,
                   tid_base_stuff + ARRAY_SIZE(tid_base_stuff));
 }
 
 static const struct file_operations proc_tid_base_operations = {
     .read       = generic_read_dir,
     .iterate_shared = proc_tid_base_readdir,
     .llseek     = generic_file_llseek,
 };
 
 static const struct inode_operations proc_tid_base_inode_operations = {
     .lookup     = proc_tid_base_lookup,
     .getattr    = pid_getattr,
     .setattr    = proc_setattr,
 };
 
 static struct dentry *proc_task_instantiate(struct dentry *dentry,
     struct task_struct *task, const void *ptr)
 {
     struct inode *inode;
     inode = proc_pid_make_base_inode(dentry->d_sb, task,
                      S_IFDIR | S_IRUGO | S_IXUGO);
     if (!inode)
         return ERR_PTR(-ENOENT);
 
     inode->i_op = &proc_tid_base_inode_operations;
     inode->i_fop = &proc_tid_base_operations;
     inode->i_flags |= S_IMMUTABLE;
 
     set_nlink(inode, nlink_tid);
     pid_update_inode(task, inode);
 
     d_set_d_op(dentry, &pid_dentry_operations);
     return d_splice_alias(inode, dentry);
 }
 
 static struct dentry *proc_task_lookup(struct inode *dir, struct dentry * dentry, unsigned int flags)
 {
     struct task_struct *task;
     struct task_struct *leader = get_proc_task(dir);
     unsigned tid;
     struct proc_fs_info *fs_info;
     struct pid_namespace *ns;
     struct dentry *result = ERR_PTR(-ENOENT);
 
     if (!leader)
         goto out_no_task;
 
     tid = name_to_int(&dentry->d_name);
     if (tid == ~0U)
         goto out;
 
     fs_info = proc_sb_info(dentry->d_sb);
     ns = fs_info->pid_ns;
     rcu_read_lock();
     task = find_task_by_pid_ns(tid, ns);
     if (task)
         get_task_struct(task);
     rcu_read_unlock();
     if (!task)
         goto out;
     if (!same_thread_group(leader, task))
         goto out_drop_task;
 
     result = proc_task_instantiate(dentry, task, NULL);
 out_drop_task:
     put_task_struct(task);
 out:
     put_task_struct(leader);
 out_no_task:
     return result;
 }
 
 /*
  * Find the first tid of a thread group to return to user space.
  *
  * Usually this is just the thread group leader, but if the users
  * buffer was too small or there was a seek into the middle of the
  * directory we have more work todo.
  *
  * In the case of a short read we start with find_task_by_pid.
  *
  * In the case of a seek we start with the leader and walk nr
  * threads past it.
  */
 static struct task_struct *first_tid(struct pid *pid, int tid, loff_t f_pos,
                     struct pid_namespace *ns)
 {
     struct task_struct *pos, *task;
     unsigned long nr = f_pos;
 
     if (nr != f_pos)    /* 32bit overflow? */
         return NULL;
 
     rcu_read_lock();
     task = pid_task(pid, PIDTYPE_PID);
     if (!task)
         goto fail;
 
     /* Attempt to start with the tid of a thread */
     if (tid && nr) {
         pos = find_task_by_pid_ns(tid, ns);
         if (pos && same_thread_group(pos, task))
             goto found;
     }
 
     /* If nr exceeds the number of threads there is nothing todo */
     if (nr >= get_nr_threads(task))
         goto fail;
 
     /* If we haven't found our starting place yet start
      * with the leader and walk nr threads forward.
      */
     pos = task = task->group_leader;
     do {
         if (!nr--)
             goto found;
     } while_each_thread(task, pos);
 fail:
     pos = NULL;
     goto out;
 found:
     get_task_struct(pos);
 out:
     rcu_read_unlock();
     return pos;
 }
 
 /*
  * Find the next thread in the thread list.
  * Return NULL if there is an error or no next thread.
  *
  * The reference to the input task_struct is released.
  */
 static struct task_struct *next_tid(struct task_struct *start)
 {
     struct task_struct *pos = NULL;
     rcu_read_lock();
     if (pid_alive(start)) {
         pos = next_thread(start);
         if (thread_group_leader(pos))
             pos = NULL;
         else
             get_task_struct(pos);
     }
     rcu_read_unlock();
     put_task_struct(start);
     return pos;
 }
 
 /* for the /proc/TGID/task/ directories */
 static int proc_task_readdir(struct file *file, struct dir_context *ctx)
 {
     struct inode *inode = file_inode(file);
     struct task_struct *task;
     struct pid_namespace *ns;
     int tid;
 
     if (proc_inode_is_dead(inode))
         return -ENOENT;
 
     if (!dir_emit_dots(file, ctx))
         return 0;
 
     /* f_version caches the tgid value that the last readdir call couldn't
      * return. lseek aka telldir automagically resets f_version to 0.
      */
     ns = proc_pid_ns(inode->i_sb);
     tid = (int)file->f_version;
     file->f_version = 0;
     for (task = first_tid(proc_pid(inode), tid, ctx->pos - 2, ns);
          task;
          task = next_tid(task), ctx->pos++) {
         char name[10 + 1];
         unsigned int len;
 
         tid = task_pid_nr_ns(task, ns);
         if (!tid)
             continue;   /* The task has just exited. */
         len = snprintf(name, sizeof(name), "%u", tid);
         if (!proc_fill_cache(file, ctx, name, len,
                 proc_task_instantiate, task, NULL)) {
             /* returning this tgid failed, save it as the first
              * pid for the next readir call */
             file->f_version = (u64)tid;
             put_task_struct(task);
             break;
         }
     }
 
     return 0;
 }
 
 static int proc_task_getattr(struct user_namespace *mnt_userns,
                  const struct path *path, struct kstat *stat,
                  u32 request_mask, unsigned int query_flags)
 {
     struct inode *inode = d_inode(path->dentry);
     struct task_struct *p = get_proc_task(inode);
     generic_fillattr(&init_user_ns, inode, stat);
 
     if (p) {
         stat->nlink += get_nr_threads(p);
         put_task_struct(p);
     }
 
     return 0;
 }
 
 static const struct inode_operations proc_task_inode_operations = {
     .lookup     = proc_task_lookup,
     .getattr    = proc_task_getattr,
     .setattr    = proc_setattr,
     .permission = proc_pid_permission,
 };
 
 static const struct file_operations proc_task_operations = {
     .read       = generic_read_dir,
     .iterate_shared = proc_task_readdir,
     .llseek     = generic_file_llseek,
 };
 
 void __init set_proc_pid_nlink(void)
 {
     nlink_tid = pid_entry_nlink(tid_base_stuff, ARRAY_SIZE(tid_base_stuff));
     nlink_tgid = pid_entry_nlink(tgid_base_stuff, ARRAY_SIZE(tgid_base_stuff));
 }