fs/proc/fd.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <linux/sched/signal.h>
0003 #include <linux/errno.h>
0004 #include <linux/dcache.h>
0005 #include <linux/path.h>
0006 #include <linux/fdtable.h>
0007 #include <linux/namei.h>
0008 #include <linux/pid.h>
0009 #include <linux/ptrace.h>
0010 #include <linux/security.h>
0011 #include <linux/file.h>
0012 #include <linux/seq_file.h>
0013 #include <linux/fs.h>
0014
0015 #include <linux/proc_fs.h>
0016
0017 #include "../mount.h"
0018 #include "internal.h"
0019 #include "fd.h"
0020
0021 static int seq_show(struct seq_file *m, void *v)
0022 {
0023     struct files_struct *files = NULL;
0024     int f_flags = 0, ret = -ENOENT;
0025     struct file *file = NULL;
0026     struct task_struct *task;
0027
0028     task = get_proc_task(m->private);
0029     if (!task)
0030         return -ENOENT;
0031
0032     task_lock(task);
0033     files = task->files;
0034     if (files) {
0035         unsigned int fd = proc_fd(m->private);
0036
0037         spin_lock(&files->file_lock);
0038         file = files_lookup_fd_locked(files, fd);
0039         if (file) {
0040             struct fdtable *fdt = files_fdtable(files);
0041
0042             f_flags = file->f_flags;
0043             if (close_on_exec(fd, fdt))
0044                 f_flags |= O_CLOEXEC;
0045
0046             get_file(file);
0047             ret = 0;
0048         }
0049         spin_unlock(&files->file_lock);
0050     }
0051     task_unlock(task);
0052     put_task_struct(task);
0053
0054     if (ret)
0055         return ret;
0056
0057     seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\nino:\t%lu\n",
0058            (long long)file->f_pos, f_flags,
0059            real_mount(file->f_path.mnt)->mnt_id,
0060            file_inode(file)->i_ino);
0061
0062     /* show_fd_locks() never deferences files so a stale value is safe */
0063     show_fd_locks(m, file, files);
0064     if (seq_has_overflowed(m))
0065         goto out;
0066
0067     if (file->f_op->show_fdinfo)
0068         file->f_op->show_fdinfo(m, file);
0069
0070 out:
0071     fput(file);
0072     return 0;
0073 }
0074
0075 static int proc_fdinfo_access_allowed(struct inode *inode)
0076 {
0077     bool allowed = false;
0078     struct task_struct *task = get_proc_task(inode);
0079
0080     if (!task)
0081         return -ESRCH;
0082
0083     allowed = ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS);
0084     put_task_struct(task);
0085
0086     if (!allowed)
0087         return -EACCES;
0088
0089     return 0;
0090 }
0091
0092 static int seq_fdinfo_open(struct inode *inode, struct file *file)
0093 {
0094     int ret = proc_fdinfo_access_allowed(inode);
0095
0096     if (ret)
0097         return ret;
0098
0099     return single_open(file, seq_show, inode);
0100 }
0101
0102 static const struct file_operations proc_fdinfo_file_operations = {
0103     .open       = seq_fdinfo_open,
0104     .read       = seq_read,
0105     .llseek     = seq_lseek,
0106     .release    = single_release,
0107 };
0108
0109 static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
0110 {
0111     struct file *file;
0112
0113     rcu_read_lock();
0114     file = task_lookup_fd_rcu(task, fd);
0115     if (file)
0116         *mode = file->f_mode;
0117     rcu_read_unlock();
0118     return !!file;
0119 }
0120
0121 static void tid_fd_update_inode(struct task_struct *task, struct inode *inode,
0122                 fmode_t f_mode)
0123 {
0124     task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
0125
0126     if (S_ISLNK(inode->i_mode)) {
0127         unsigned i_mode = S_IFLNK;
0128         if (f_mode & FMODE_READ)
0129             i_mode |= S_IRUSR | S_IXUSR;
0130         if (f_mode & FMODE_WRITE)
0131             i_mode |= S_IWUSR | S_IXUSR;
0132         inode->i_mode = i_mode;
0133     }
0134     security_task_to_inode(task, inode);
0135 }
0136
0137 static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
0138 {
0139     struct task_struct *task;
0140     struct inode *inode;
0141     unsigned int fd;
0142
0143     if (flags & LOOKUP_RCU)
0144         return -ECHILD;
0145
0146     inode = d_inode(dentry);
0147     task = get_proc_task(inode);
0148     fd = proc_fd(inode);
0149
0150     if (task) {
0151         fmode_t f_mode;
0152         if (tid_fd_mode(task, fd, &f_mode)) {
0153             tid_fd_update_inode(task, inode, f_mode);
0154             put_task_struct(task);
0155             return 1;
0156         }
0157         put_task_struct(task);
0158     }
0159     return 0;
0160 }
0161
0162 static const struct dentry_operations tid_fd_dentry_operations = {
0163     .d_revalidate   = tid_fd_revalidate,
0164     .d_delete   = pid_delete_dentry,
0165 };
0166
0167 static int proc_fd_link(struct dentry *dentry, struct path *path)
0168 {
0169     struct task_struct *task;
0170     int ret = -ENOENT;
0171
0172     task = get_proc_task(d_inode(dentry));
0173     if (task) {
0174         unsigned int fd = proc_fd(d_inode(dentry));
0175         struct file *fd_file;
0176
0177         fd_file = fget_task(task, fd);
0178         if (fd_file) {
0179             *path = fd_file->f_path;
0180             path_get(&fd_file->f_path);
0181             ret = 0;
0182             fput(fd_file);
0183         }
0184         put_task_struct(task);
0185     }
0186
0187     return ret;
0188 }
0189
0190 struct fd_data {
0191     fmode_t mode;
0192     unsigned fd;
0193 };
0194
0195 static struct dentry *proc_fd_instantiate(struct dentry *dentry,
0196     struct task_struct *task, const void *ptr)
0197 {
0198     const struct fd_data *data = ptr;
0199     struct proc_inode *ei;
0200     struct inode *inode;
0201
0202     inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK);
0203     if (!inode)
0204         return ERR_PTR(-ENOENT);
0205
0206     ei = PROC_I(inode);
0207     ei->fd = data->fd;
0208
0209     inode->i_op = &proc_pid_link_inode_operations;
0210     inode->i_size = 64;
0211
0212     ei->op.proc_get_link = proc_fd_link;
0213     tid_fd_update_inode(task, inode, data->mode);
0214
0215     d_set_d_op(dentry, &tid_fd_dentry_operations);
0216     return d_splice_alias(inode, dentry);
0217 }
0218
0219 static struct dentry *proc_lookupfd_common(struct inode *dir,
0220                        struct dentry *dentry,
0221                        instantiate_t instantiate)
0222 {
0223     struct task_struct *task = get_proc_task(dir);
0224     struct fd_data data = {.fd = name_to_int(&dentry->d_name)};
0225     struct dentry *result = ERR_PTR(-ENOENT);
0226
0227     if (!task)
0228         goto out_no_task;
0229     if (data.fd == ~0U)
0230         goto out;
0231     if (!tid_fd_mode(task, data.fd, &data.mode))
0232         goto out;
0233
0234     result = instantiate(dentry, task, &data);
0235 out:
0236     put_task_struct(task);
0237 out_no_task:
0238     return result;
0239 }
0240
0241 static int proc_readfd_common(struct file *file, struct dir_context *ctx,
0242                   instantiate_t instantiate)
0243 {
0244     struct task_struct *p = get_proc_task(file_inode(file));
0245     unsigned int fd;
0246
0247     if (!p)
0248         return -ENOENT;
0249
0250     if (!dir_emit_dots(file, ctx))
0251         goto out;
0252
0253     rcu_read_lock();
0254     for (fd = ctx->pos - 2;; fd++) {
0255         struct file *f;
0256         struct fd_data data;
0257         char name[10 + 1];
0258         unsigned int len;
0259
0260         f = task_lookup_next_fd_rcu(p, &fd);
0261         ctx->pos = fd + 2LL;
0262         if (!f)
0263             break;
0264         data.mode = f->f_mode;
0265         rcu_read_unlock();
0266         data.fd = fd;
0267
0268         len = snprintf(name, sizeof(name), "%u", fd);
0269         if (!proc_fill_cache(file, ctx,
0270                      name, len, instantiate, p,
0271                      &data))
0272             goto out;
0273         cond_resched();
0274         rcu_read_lock();
0275     }
0276     rcu_read_unlock();
0277 out:
0278     put_task_struct(p);
0279     return 0;
0280 }
0281
0282 static int proc_readfd(struct file *file, struct dir_context *ctx)
0283 {
0284     return proc_readfd_common(file, ctx, proc_fd_instantiate);
0285 }
0286
0287 const struct file_operations proc_fd_operations = {
0288     .read       = generic_read_dir,
0289     .iterate_shared = proc_readfd,
0290     .llseek     = generic_file_llseek,
0291 };
0292
0293 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
0294                     unsigned int flags)
0295 {
0296     return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
0297 }
0298
0299 /*
0300  * /proc/pid/fd needs a special permission handler so that a process can still
0301  * access /proc/self/fd after it has executed a setuid().
0302  */
0303 int proc_fd_permission(struct user_namespace *mnt_userns,
0304                struct inode *inode, int mask)
0305 {
0306     struct task_struct *p;
0307     int rv;
0308
0309     rv = generic_permission(&init_user_ns, inode, mask);
0310     if (rv == 0)
0311         return rv;
0312
0313     rcu_read_lock();
0314     p = pid_task(proc_pid(inode), PIDTYPE_PID);
0315     if (p && same_thread_group(p, current))
0316         rv = 0;
0317     rcu_read_unlock();
0318
0319     return rv;
0320 }
0321
0322 const struct inode_operations proc_fd_inode_operations = {
0323     .lookup     = proc_lookupfd,
0324     .permission = proc_fd_permission,
0325     .setattr    = proc_setattr,
0326 };
0327
0328 static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry,
0329     struct task_struct *task, const void *ptr)
0330 {
0331     const struct fd_data *data = ptr;
0332     struct proc_inode *ei;
0333     struct inode *inode;
0334
0335     inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUGO);
0336     if (!inode)
0337         return ERR_PTR(-ENOENT);
0338
0339     ei = PROC_I(inode);
0340     ei->fd = data->fd;
0341
0342     inode->i_fop = &proc_fdinfo_file_operations;
0343     tid_fd_update_inode(task, inode, 0);
0344
0345     d_set_d_op(dentry, &tid_fd_dentry_operations);
0346     return d_splice_alias(inode, dentry);
0347 }
0348
0349 static struct dentry *
0350 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
0351 {
0352     return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
0353 }
0354
0355 static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
0356 {
0357     return proc_readfd_common(file, ctx,
0358                   proc_fdinfo_instantiate);
0359 }
0360
0361 static int proc_open_fdinfo(struct inode *inode, struct file *file)
0362 {
0363     int ret = proc_fdinfo_access_allowed(inode);
0364
0365     if (ret)
0366         return ret;
0367
0368     return 0;
0369 }
0370
0371 const struct inode_operations proc_fdinfo_inode_operations = {
0372     .lookup     = proc_lookupfdinfo,
0373     .setattr    = proc_setattr,
0374 };
0375
0376 const struct file_operations proc_fdinfo_operations = {
0377     .open       = proc_open_fdinfo,
0378     .read       = generic_read_dir,
0379     .iterate_shared = proc_readfdinfo,
0380     .llseek     = generic_file_llseek,
0381 };