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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  *  linux/fs/file.c
  *
  *  Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
  *
  *  Manage the dynamic fd arrays in the process files_struct.
  */
 
 #include <linux/syscalls.h>
 #include <linux/export.h>
 #include <linux/fs.h>
 #include <linux/kernel.h>
 #include <linux/mm.h>
 #include <linux/sched/signal.h>
 #include <linux/slab.h>
 #include <linux/file.h>
 #include <linux/fdtable.h>
 #include <linux/bitops.h>
 #include <linux/spinlock.h>
 #include <linux/rcupdate.h>
 #include <linux/close_range.h>
 #include <net/sock.h>
 
 #include "internal.h"
 
 unsigned int sysctl_nr_open __read_mostly = 1024*1024;
 unsigned int sysctl_nr_open_min = BITS_PER_LONG;
 /* our min() is unusable in constant expressions ;-/ */
 #define __const_min(x, y) ((x) < (y) ? (x) : (y))
 unsigned int sysctl_nr_open_max =
     __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
 
 static void __free_fdtable(struct fdtable *fdt)
 {
     kvfree(fdt->fd);
     kvfree(fdt->open_fds);
     kfree(fdt);
 }
 
 static void free_fdtable_rcu(struct rcu_head *rcu)
 {
     __free_fdtable(container_of(rcu, struct fdtable, rcu));
 }
 
 #define BITBIT_NR(nr)   BITS_TO_LONGS(BITS_TO_LONGS(nr))
 #define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
 
 /*
  * Copy 'count' fd bits from the old table to the new table and clear the extra
  * space if any.  This does not copy the file pointers.  Called with the files
  * spinlock held for write.
  */
 static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
                 unsigned int count)
 {
     unsigned int cpy, set;
 
     cpy = count / BITS_PER_BYTE;
     set = (nfdt->max_fds - count) / BITS_PER_BYTE;
     memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
     memset((char *)nfdt->open_fds + cpy, 0, set);
     memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
     memset((char *)nfdt->close_on_exec + cpy, 0, set);
 
     cpy = BITBIT_SIZE(count);
     set = BITBIT_SIZE(nfdt->max_fds) - cpy;
     memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
     memset((char *)nfdt->full_fds_bits + cpy, 0, set);
 }
 
 /*
  * Copy all file descriptors from the old table to the new, expanded table and
  * clear the extra space.  Called with the files spinlock held for write.
  */
 static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
 {
     size_t cpy, set;
 
     BUG_ON(nfdt->max_fds < ofdt->max_fds);
 
     cpy = ofdt->max_fds * sizeof(struct file *);
     set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
     memcpy(nfdt->fd, ofdt->fd, cpy);
     memset((char *)nfdt->fd + cpy, 0, set);
 
     copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
 }
 
 /*
  * Note how the fdtable bitmap allocations very much have to be a multiple of
  * BITS_PER_LONG. This is not only because we walk those things in chunks of
  * 'unsigned long' in some places, but simply because that is how the Linux
  * kernel bitmaps are defined to work: they are not "bits in an array of bytes",
  * they are very much "bits in an array of unsigned long".
  *
  * The ALIGN(nr, BITS_PER_LONG) here is for clarity: since we just multiplied
  * by that "1024/sizeof(ptr)" before, we already know there are sufficient
  * clear low bits. Clang seems to realize that, gcc ends up being confused.
  *
  * On a 128-bit machine, the ALIGN() would actually matter. In the meantime,
  * let's consider it documentation (and maybe a test-case for gcc to improve
  * its code generation ;)
  */
 static struct fdtable * alloc_fdtable(unsigned int nr)
 {
     struct fdtable *fdt;
     void *data;
 
     /*
      * Figure out how many fds we actually want to support in this fdtable.
      * Allocation steps are keyed to the size of the fdarray, since it
      * grows far faster than any of the other dynamic data. We try to fit
      * the fdarray into comfortable page-tuned chunks: starting at 1024B
      * and growing in powers of two from there on.
      */
     nr /= (1024 / sizeof(struct file *));
     nr = roundup_pow_of_two(nr + 1);
     nr *= (1024 / sizeof(struct file *));
     nr = ALIGN(nr, BITS_PER_LONG);
     /*
      * Note that this can drive nr *below* what we had passed if sysctl_nr_open
      * had been set lower between the check in expand_files() and here.  Deal
      * with that in caller, it's cheaper that way.
      *
      * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
      * bitmaps handling below becomes unpleasant, to put it mildly...
      */
     if (unlikely(nr > sysctl_nr_open))
         nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
 
     fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
     if (!fdt)
         goto out;
     fdt->max_fds = nr;
     data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
     if (!data)
         goto out_fdt;
     fdt->fd = data;
 
     data = kvmalloc(max_t(size_t,
                  2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
                  GFP_KERNEL_ACCOUNT);
     if (!data)
         goto out_arr;
     fdt->open_fds = data;
     data += nr / BITS_PER_BYTE;
     fdt->close_on_exec = data;
     data += nr / BITS_PER_BYTE;
     fdt->full_fds_bits = data;
 
     return fdt;
 
 out_arr:
     kvfree(fdt->fd);
 out_fdt:
     kfree(fdt);
 out:
     return NULL;
 }
 
 /*
  * Expand the file descriptor table.
  * This function will allocate a new fdtable and both fd array and fdset, of
  * the given size.
  * Return <0 error code on error; 1 on successful completion.
  * The files->file_lock should be held on entry, and will be held on exit.
  */
 static int expand_fdtable(struct files_struct *files, unsigned int nr)
     __releases(files->file_lock)
     __acquires(files->file_lock)
 {
     struct fdtable *new_fdt, *cur_fdt;
 
     spin_unlock(&files->file_lock);
     new_fdt = alloc_fdtable(nr);
 
     /* make sure all fd_install() have seen resize_in_progress
      * or have finished their rcu_read_lock_sched() section.
      */
     if (atomic_read(&files->count) > 1)
         synchronize_rcu();
 
     spin_lock(&files->file_lock);
     if (!new_fdt)
         return -ENOMEM;
     /*
      * extremely unlikely race - sysctl_nr_open decreased between the check in
      * caller and alloc_fdtable().  Cheaper to catch it here...
      */
     if (unlikely(new_fdt->max_fds <= nr)) {
         __free_fdtable(new_fdt);
         return -EMFILE;
     }
     cur_fdt = files_fdtable(files);
     BUG_ON(nr < cur_fdt->max_fds);
     copy_fdtable(new_fdt, cur_fdt);
     rcu_assign_pointer(files->fdt, new_fdt);
     if (cur_fdt != &files->fdtab)
         call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
     /* coupled with smp_rmb() in fd_install() */
     smp_wmb();
     return 1;
 }
 
 /*
  * Expand files.
  * This function will expand the file structures, if the requested size exceeds
  * the current capacity and there is room for expansion.
  * Return <0 error code on error; 0 when nothing done; 1 when files were
  * expanded and execution may have blocked.
  * The files->file_lock should be held on entry, and will be held on exit.
  */
 static int expand_files(struct files_struct *files, unsigned int nr)
     __releases(files->file_lock)
     __acquires(files->file_lock)
 {
     struct fdtable *fdt;
     int expanded = 0;
 
 repeat:
     fdt = files_fdtable(files);
 
     /* Do we need to expand? */
     if (nr < fdt->max_fds)
         return expanded;
 
     /* Can we expand? */
     if (nr >= sysctl_nr_open)
         return -EMFILE;
 
     if (unlikely(files->resize_in_progress)) {
         spin_unlock(&files->file_lock);
         expanded = 1;
         wait_event(files->resize_wait, !files->resize_in_progress);
         spin_lock(&files->file_lock);
         goto repeat;
     }
 
     /* All good, so we try */
     files->resize_in_progress = true;
     expanded = expand_fdtable(files, nr);
     files->resize_in_progress = false;
 
     wake_up_all(&files->resize_wait);
     return expanded;
 }
 
 static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
 {
     __set_bit(fd, fdt->close_on_exec);
 }
 
 static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
 {
     if (test_bit(fd, fdt->close_on_exec))
         __clear_bit(fd, fdt->close_on_exec);
 }
 
 static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
 {
     __set_bit(fd, fdt->open_fds);
     fd /= BITS_PER_LONG;
     if (!~fdt->open_fds[fd])
         __set_bit(fd, fdt->full_fds_bits);
 }
 
 static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
 {
     __clear_bit(fd, fdt->open_fds);
     __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
 }
 
 static unsigned int count_open_files(struct fdtable *fdt)
 {
     unsigned int size = fdt->max_fds;
     unsigned int i;
 
     /* Find the last open fd */
     for (i = size / BITS_PER_LONG; i > 0; ) {
         if (fdt->open_fds[--i])
             break;
     }
     i = (i + 1) * BITS_PER_LONG;
     return i;
 }
 
 /*
  * Note that a sane fdtable size always has to be a multiple of
  * BITS_PER_LONG, since we have bitmaps that are sized by this.
  *
  * 'max_fds' will normally already be properly aligned, but it
  * turns out that in the close_range() -> __close_range() ->
  * unshare_fd() -> dup_fd() -> sane_fdtable_size() we can end
  * up having a 'max_fds' value that isn't already aligned.
  *
  * Rather than make close_range() have to worry about this,
  * just make that BITS_PER_LONG alignment be part of a sane
  * fdtable size. Becuase that's really what it is.
  */
 static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
 {
     unsigned int count;
 
     count = count_open_files(fdt);
     if (max_fds < NR_OPEN_DEFAULT)
         max_fds = NR_OPEN_DEFAULT;
     return ALIGN(min(count, max_fds), BITS_PER_LONG);
 }
 
 /*
  * Allocate a new files structure and copy contents from the
  * passed in files structure.
  * errorp will be valid only when the returned files_struct is NULL.
  */
 struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp)
 {
     struct files_struct *newf;
     struct file **old_fds, **new_fds;
     unsigned int open_files, i;
     struct fdtable *old_fdt, *new_fdt;
 
     *errorp = -ENOMEM;
     newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
     if (!newf)
         goto out;
 
     atomic_set(&newf->count, 1);
 
     spin_lock_init(&newf->file_lock);
     newf->resize_in_progress = false;
     init_waitqueue_head(&newf->resize_wait);
     newf->next_fd = 0;
     new_fdt = &newf->fdtab;
     new_fdt->max_fds = NR_OPEN_DEFAULT;
     new_fdt->close_on_exec = newf->close_on_exec_init;
     new_fdt->open_fds = newf->open_fds_init;
     new_fdt->full_fds_bits = newf->full_fds_bits_init;
     new_fdt->fd = &newf->fd_array[0];
 
     spin_lock(&oldf->file_lock);
     old_fdt = files_fdtable(oldf);
     open_files = sane_fdtable_size(old_fdt, max_fds);
 
     /*
      * Check whether we need to allocate a larger fd array and fd set.
      */
     while (unlikely(open_files > new_fdt->max_fds)) {
         spin_unlock(&oldf->file_lock);
 
         if (new_fdt != &newf->fdtab)
             __free_fdtable(new_fdt);
 
         new_fdt = alloc_fdtable(open_files - 1);
         if (!new_fdt) {
             *errorp = -ENOMEM;
             goto out_release;
         }
 
         /* beyond sysctl_nr_open; nothing to do */
         if (unlikely(new_fdt->max_fds < open_files)) {
             __free_fdtable(new_fdt);
             *errorp = -EMFILE;
             goto out_release;
         }
 
         /*
          * Reacquire the oldf lock and a pointer to its fd table
          * who knows it may have a new bigger fd table. We need
          * the latest pointer.
          */
         spin_lock(&oldf->file_lock);
         old_fdt = files_fdtable(oldf);
         open_files = sane_fdtable_size(old_fdt, max_fds);
     }
 
     copy_fd_bitmaps(new_fdt, old_fdt, open_files);
 
     old_fds = old_fdt->fd;
     new_fds = new_fdt->fd;
 
     for (i = open_files; i != 0; i--) {
         struct file *f = *old_fds++;
         if (f) {
             get_file(f);
         } else {
             /*
              * The fd may be claimed in the fd bitmap but not yet
              * instantiated in the files array if a sibling thread
              * is partway through open().  So make sure that this
              * fd is available to the new process.
              */
             __clear_open_fd(open_files - i, new_fdt);
         }
         rcu_assign_pointer(*new_fds++, f);
     }
     spin_unlock(&oldf->file_lock);
 
     /* clear the remainder */
     memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
 
     rcu_assign_pointer(newf->fdt, new_fdt);
 
     return newf;
 
 out_release:
     kmem_cache_free(files_cachep, newf);
 out:
     return NULL;
 }
 
 static struct fdtable *close_files(struct files_struct * files)
 {
     /*
      * It is safe to dereference the fd table without RCU or
      * ->file_lock because this is the last reference to the
      * files structure.
      */
     struct fdtable *fdt = rcu_dereference_raw(files->fdt);
     unsigned int i, j = 0;
 
     for (;;) {
         unsigned long set;
         i = j * BITS_PER_LONG;
         if (i >= fdt->max_fds)
             break;
         set = fdt->open_fds[j++];
         while (set) {
             if (set & 1) {
                 struct file * file = xchg(&fdt->fd[i], NULL);
                 if (file) {
                     filp_close(file, files);
                     cond_resched();
                 }
             }
             i++;
             set >>= 1;
         }
     }
 
     return fdt;
 }
 
 void put_files_struct(struct files_struct *files)
 {
     if (atomic_dec_and_test(&files->count)) {
         struct fdtable *fdt = close_files(files);
 
         /* free the arrays if they are not embedded */
         if (fdt != &files->fdtab)
             __free_fdtable(fdt);
         kmem_cache_free(files_cachep, files);
     }
 }
 
 void exit_files(struct task_struct *tsk)
 {
     struct files_struct * files = tsk->files;
 
     if (files) {
         task_lock(tsk);
         tsk->files = NULL;
         task_unlock(tsk);
         put_files_struct(files);
     }
 }
 
 struct files_struct init_files = {
     .count      = ATOMIC_INIT(1),
     .fdt        = &init_files.fdtab,
     .fdtab      = {
         .max_fds    = NR_OPEN_DEFAULT,
         .fd     = &init_files.fd_array[0],
         .close_on_exec  = init_files.close_on_exec_init,
         .open_fds   = init_files.open_fds_init,
         .full_fds_bits  = init_files.full_fds_bits_init,
     },
     .file_lock  = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
     .resize_wait    = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
 };
 
 static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
 {
     unsigned int maxfd = fdt->max_fds;
     unsigned int maxbit = maxfd / BITS_PER_LONG;
     unsigned int bitbit = start / BITS_PER_LONG;
 
     bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
     if (bitbit > maxfd)
         return maxfd;
     if (bitbit > start)
         start = bitbit;
     return find_next_zero_bit(fdt->open_fds, maxfd, start);
 }
 
 /*
  * allocate a file descriptor, mark it busy.
  */
 static int alloc_fd(unsigned start, unsigned end, unsigned flags)
 {
     struct files_struct *files = current->files;
     unsigned int fd;
     int error;
     struct fdtable *fdt;
 
     spin_lock(&files->file_lock);
 repeat:
     fdt = files_fdtable(files);
     fd = start;
     if (fd < files->next_fd)
         fd = files->next_fd;
 
     if (fd < fdt->max_fds)
         fd = find_next_fd(fdt, fd);
 
     /*
      * N.B. For clone tasks sharing a files structure, this test
      * will limit the total number of files that can be opened.
      */
     error = -EMFILE;
     if (fd >= end)
         goto out;
 
     error = expand_files(files, fd);
     if (error < 0)
         goto out;
 
     /*
      * If we needed to expand the fs array we
      * might have blocked - try again.
      */
     if (error)
         goto repeat;
 
     if (start <= files->next_fd)
         files->next_fd = fd + 1;
 
     __set_open_fd(fd, fdt);
     if (flags & O_CLOEXEC)
         __set_close_on_exec(fd, fdt);
     else
         __clear_close_on_exec(fd, fdt);
     error = fd;
 #if 1
     /* Sanity check */
     if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
         printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
         rcu_assign_pointer(fdt->fd[fd], NULL);
     }
 #endif
 
 out:
     spin_unlock(&files->file_lock);
     return error;
 }
 
 int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
 {
     return alloc_fd(0, nofile, flags);
 }
 
 int get_unused_fd_flags(unsigned flags)
 {
     return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
 }
 EXPORT_SYMBOL(get_unused_fd_flags);
 
 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
 {
     struct fdtable *fdt = files_fdtable(files);
     __clear_open_fd(fd, fdt);
     if (fd < files->next_fd)
         files->next_fd = fd;
 }
 
 void put_unused_fd(unsigned int fd)
 {
     struct files_struct *files = current->files;
     spin_lock(&files->file_lock);
     __put_unused_fd(files, fd);
     spin_unlock(&files->file_lock);
 }
 
 EXPORT_SYMBOL(put_unused_fd);
 
 /*
  * Install a file pointer in the fd array.
  *
  * The VFS is full of places where we drop the files lock between
  * setting the open_fds bitmap and installing the file in the file
  * array.  At any such point, we are vulnerable to a dup2() race
  * installing a file in the array before us.  We need to detect this and
  * fput() the struct file we are about to overwrite in this case.
  *
  * It should never happen - if we allow dup2() do it, _really_ bad things
  * will follow.
  *
  * This consumes the "file" refcount, so callers should treat it
  * as if they had called fput(file).
  */
 
 void fd_install(unsigned int fd, struct file *file)
 {
     struct files_struct *files = current->files;
     struct fdtable *fdt;
 
     rcu_read_lock_sched();
 
     if (unlikely(files->resize_in_progress)) {
         rcu_read_unlock_sched();
         spin_lock(&files->file_lock);
         fdt = files_fdtable(files);
         BUG_ON(fdt->fd[fd] != NULL);
         rcu_assign_pointer(fdt->fd[fd], file);
         spin_unlock(&files->file_lock);
         return;
     }
     /* coupled with smp_wmb() in expand_fdtable() */
     smp_rmb();
     fdt = rcu_dereference_sched(files->fdt);
     BUG_ON(fdt->fd[fd] != NULL);
     rcu_assign_pointer(fdt->fd[fd], file);
     rcu_read_unlock_sched();
 }
 
 EXPORT_SYMBOL(fd_install);
 
 /**
  * pick_file - return file associatd with fd
  * @files: file struct to retrieve file from
  * @fd: file descriptor to retrieve file for
  *
  * Context: files_lock must be held.
  *
  * Returns: The file associated with @fd (NULL if @fd is not open)
  */
 static struct file *pick_file(struct files_struct *files, unsigned fd)
 {
     struct fdtable *fdt = files_fdtable(files);
     struct file *file;
 
     if (fd >= fdt->max_fds)
         return NULL;
 
     file = fdt->fd[fd];
     if (file) {
         rcu_assign_pointer(fdt->fd[fd], NULL);
         __put_unused_fd(files, fd);
     }
     return file;
 }
 
 int close_fd(unsigned fd)
 {
     struct files_struct *files = current->files;
     struct file *file;
 
     spin_lock(&files->file_lock);
     file = pick_file(files, fd);
     spin_unlock(&files->file_lock);
     if (!file)
         return -EBADF;
 
     return filp_close(file, files);
 }
 EXPORT_SYMBOL(close_fd); /* for ksys_close() */
 
 /**
  * last_fd - return last valid index into fd table
  * @cur_fds: files struct
  *
  * Context: Either rcu read lock or files_lock must be held.
  *
  * Returns: Last valid index into fdtable.
  */
 static inline unsigned last_fd(struct fdtable *fdt)
 {
     return fdt->max_fds - 1;
 }
 
 static inline void __range_cloexec(struct files_struct *cur_fds,
                    unsigned int fd, unsigned int max_fd)
 {
     struct fdtable *fdt;
 
     /* make sure we're using the correct maximum value */
     spin_lock(&cur_fds->file_lock);
     fdt = files_fdtable(cur_fds);
     max_fd = min(last_fd(fdt), max_fd);
     if (fd <= max_fd)
         bitmap_set(fdt->close_on_exec, fd, max_fd - fd + 1);
     spin_unlock(&cur_fds->file_lock);
 }
 
 static inline void __range_close(struct files_struct *cur_fds, unsigned int fd,
                  unsigned int max_fd)
 {
     unsigned n;
 
     rcu_read_lock();
     n = last_fd(files_fdtable(cur_fds));
     rcu_read_unlock();
     max_fd = min(max_fd, n);
 
     while (fd <= max_fd) {
         struct file *file;
 
         spin_lock(&cur_fds->file_lock);
         file = pick_file(cur_fds, fd++);
         spin_unlock(&cur_fds->file_lock);
 
         if (file) {
             /* found a valid file to close */
             filp_close(file, cur_fds);
             cond_resched();
         }
     }
 }
 
 /**
  * __close_range() - Close all file descriptors in a given range.
  *
  * @fd:     starting file descriptor to close
  * @max_fd: last file descriptor to close
  *
  * This closes a range of file descriptors. All file descriptors
  * from @fd up to and including @max_fd are closed.
  */
 int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
 {
     struct task_struct *me = current;
     struct files_struct *cur_fds = me->files, *fds = NULL;
 
     if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC))
         return -EINVAL;
 
     if (fd > max_fd)
         return -EINVAL;
 
     if (flags & CLOSE_RANGE_UNSHARE) {
         int ret;
         unsigned int max_unshare_fds = NR_OPEN_MAX;
 
         /*
          * If the caller requested all fds to be made cloexec we always
          * copy all of the file descriptors since they still want to
          * use them.
          */
         if (!(flags & CLOSE_RANGE_CLOEXEC)) {
             /*
              * If the requested range is greater than the current
              * maximum, we're closing everything so only copy all
              * file descriptors beneath the lowest file descriptor.
              */
             rcu_read_lock();
             if (max_fd >= last_fd(files_fdtable(cur_fds)))
                 max_unshare_fds = fd;
             rcu_read_unlock();
         }
 
         ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
         if (ret)
             return ret;
 
         /*
          * We used to share our file descriptor table, and have now
          * created a private one, make sure we're using it below.
          */
         if (fds)
             swap(cur_fds, fds);
     }
 
     if (flags & CLOSE_RANGE_CLOEXEC)
         __range_cloexec(cur_fds, fd, max_fd);
     else
         __range_close(cur_fds, fd, max_fd);
 
     if (fds) {
         /*
          * We're done closing the files we were supposed to. Time to install
          * the new file descriptor table and drop the old one.
          */
         task_lock(me);
         me->files = cur_fds;
         task_unlock(me);
         put_files_struct(fds);
     }
 
     return 0;
 }
 
 /*
  * See close_fd_get_file() below, this variant assumes current->files->file_lock
  * is held.
  */
 struct file *__close_fd_get_file(unsigned int fd)
 {
     return pick_file(current->files, fd);
 }
 
 /*
  * variant of close_fd that gets a ref on the file for later fput.
  * The caller must ensure that filp_close() called on the file.
  */
 struct file *close_fd_get_file(unsigned int fd)
 {
     struct files_struct *files = current->files;
     struct file *file;
 
     spin_lock(&files->file_lock);
     file = pick_file(files, fd);
     spin_unlock(&files->file_lock);
 
     return file;
 }
 
 void do_close_on_exec(struct files_struct *files)
 {
     unsigned i;
     struct fdtable *fdt;
 
     /* exec unshares first */
     spin_lock(&files->file_lock);
     for (i = 0; ; i++) {
         unsigned long set;
         unsigned fd = i * BITS_PER_LONG;
         fdt = files_fdtable(files);
         if (fd >= fdt->max_fds)
             break;
         set = fdt->close_on_exec[i];
         if (!set)
             continue;
         fdt->close_on_exec[i] = 0;
         for ( ; set ; fd++, set >>= 1) {
             struct file *file;
             if (!(set & 1))
                 continue;
             file = fdt->fd[fd];
             if (!file)
                 continue;
             rcu_assign_pointer(fdt->fd[fd], NULL);
             __put_unused_fd(files, fd);
             spin_unlock(&files->file_lock);
             filp_close(file, files);
             cond_resched();
             spin_lock(&files->file_lock);
         }
 
     }
     spin_unlock(&files->file_lock);
 }
 
 static inline struct file *__fget_files_rcu(struct files_struct *files,
     unsigned int fd, fmode_t mask)
 {
     for (;;) {
         struct file *file;
         struct fdtable *fdt = rcu_dereference_raw(files->fdt);
         struct file __rcu **fdentry;
 
         if (unlikely(fd >= fdt->max_fds))
             return NULL;
 
         fdentry = fdt->fd + array_index_nospec(fd, fdt->max_fds);
         file = rcu_dereference_raw(*fdentry);
         if (unlikely(!file))
             return NULL;
 
         if (unlikely(file->f_mode & mask))
             return NULL;
 
         /*
          * Ok, we have a file pointer. However, because we do
          * this all locklessly under RCU, we may be racing with
          * that file being closed.
          *
          * Such a race can take two forms:
          *
          *  (a) the file ref already went down to zero,
          *      and get_file_rcu() fails. Just try again:
          */
         if (unlikely(!get_file_rcu(file)))
             continue;
 
         /*
          *  (b) the file table entry has changed under us.
          *       Note that we don't need to re-check the 'fdt->fd'
          *       pointer having changed, because it always goes
          *       hand-in-hand with 'fdt'.
          *
          * If so, we need to put our ref and try again.
          */
         if (unlikely(rcu_dereference_raw(files->fdt) != fdt) ||
             unlikely(rcu_dereference_raw(*fdentry) != file)) {
             fput(file);
             continue;
         }
 
         /*
          * Ok, we have a ref to the file, and checked that it
          * still exists.
          */
         return file;
     }
 }
 
 static struct file *__fget_files(struct files_struct *files, unsigned int fd,
                  fmode_t mask)
 {
     struct file *file;
 
     rcu_read_lock();
     file = __fget_files_rcu(files, fd, mask);
     rcu_read_unlock();
 
     return file;
 }
 
 static inline struct file *__fget(unsigned int fd, fmode_t mask)
 {
     return __fget_files(current->files, fd, mask);
 }
 
 struct file *fget(unsigned int fd)
 {
     return __fget(fd, FMODE_PATH);
 }
 EXPORT_SYMBOL(fget);
 
 struct file *fget_raw(unsigned int fd)
 {
     return __fget(fd, 0);
 }
 EXPORT_SYMBOL(fget_raw);
 
 struct file *fget_task(struct task_struct *task, unsigned int fd)
 {
     struct file *file = NULL;
 
     task_lock(task);
     if (task->files)
         file = __fget_files(task->files, fd, 0);
     task_unlock(task);
 
     return file;
 }
 
 struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)
 {
     /* Must be called with rcu_read_lock held */
     struct files_struct *files;
     struct file *file = NULL;
 
     task_lock(task);
     files = task->files;
     if (files)
         file = files_lookup_fd_rcu(files, fd);
     task_unlock(task);
 
     return file;
 }
 
 struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *ret_fd)
 {
     /* Must be called with rcu_read_lock held */
     struct files_struct *files;
     unsigned int fd = *ret_fd;
     struct file *file = NULL;
 
     task_lock(task);
     files = task->files;
     if (files) {
         for (; fd < files_fdtable(files)->max_fds; fd++) {
             file = files_lookup_fd_rcu(files, fd);
             if (file)
                 break;
         }
     }
     task_unlock(task);
     *ret_fd = fd;
     return file;
 }
 
 /*
  * Lightweight file lookup - no refcnt increment if fd table isn't shared.
  *
  * You can use this instead of fget if you satisfy all of the following
  * conditions:
  * 1) You must call fput_light before exiting the syscall and returning control
  *    to userspace (i.e. you cannot remember the returned struct file * after
  *    returning to userspace).
  * 2) You must not call filp_close on the returned struct file * in between
  *    calls to fget_light and fput_light.
  * 3) You must not clone the current task in between the calls to fget_light
  *    and fput_light.
  *
  * The fput_needed flag returned by fget_light should be passed to the
  * corresponding fput_light.
  */
 static unsigned long __fget_light(unsigned int fd, fmode_t mask)
 {
     struct files_struct *files = current->files;
     struct file *file;
 
     if (atomic_read(&files->count) == 1) {
         file = files_lookup_fd_raw(files, fd);
         if (!file || unlikely(file->f_mode & mask))
             return 0;
         return (unsigned long)file;
     } else {
         file = __fget(fd, mask);
         if (!file)
             return 0;
         return FDPUT_FPUT | (unsigned long)file;
     }
 }
 unsigned long __fdget(unsigned int fd)
 {
     return __fget_light(fd, FMODE_PATH);
 }
 EXPORT_SYMBOL(__fdget);
 
 unsigned long __fdget_raw(unsigned int fd)
 {
     return __fget_light(fd, 0);
 }
 
 unsigned long __fdget_pos(unsigned int fd)
 {
     unsigned long v = __fdget(fd);
     struct file *file = (struct file *)(v & ~3);
 
     if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
         if (file_count(file) > 1) {
             v |= FDPUT_POS_UNLOCK;
             mutex_lock(&file->f_pos_lock);
         }
     }
     return v;
 }
 
 void __f_unlock_pos(struct file *f)
 {
     mutex_unlock(&f->f_pos_lock);
 }
 
 /*
  * We only lock f_pos if we have threads or if the file might be
  * shared with another process. In both cases we'll have an elevated
  * file count (done either by fdget() or by fork()).
  */
 
 void set_close_on_exec(unsigned int fd, int flag)
 {
     struct files_struct *files = current->files;
     struct fdtable *fdt;
     spin_lock(&files->file_lock);
     fdt = files_fdtable(files);
     if (flag)
         __set_close_on_exec(fd, fdt);
     else
         __clear_close_on_exec(fd, fdt);
     spin_unlock(&files->file_lock);
 }
 
 bool get_close_on_exec(unsigned int fd)
 {
     struct files_struct *files = current->files;
     struct fdtable *fdt;
     bool res;
     rcu_read_lock();
     fdt = files_fdtable(files);
     res = close_on_exec(fd, fdt);
     rcu_read_unlock();
     return res;
 }
 
 static int do_dup2(struct files_struct *files,
     struct file *file, unsigned fd, unsigned flags)
 __releases(&files->file_lock)
 {
     struct file *tofree;
     struct fdtable *fdt;
 
     /*
      * We need to detect attempts to do dup2() over allocated but still
      * not finished descriptor.  NB: OpenBSD avoids that at the price of
      * extra work in their equivalent of fget() - they insert struct
      * file immediately after grabbing descriptor, mark it larval if
      * more work (e.g. actual opening) is needed and make sure that
      * fget() treats larval files as absent.  Potentially interesting,
      * but while extra work in fget() is trivial, locking implications
      * and amount of surgery on open()-related paths in VFS are not.
      * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
      * deadlocks in rather amusing ways, AFAICS.  All of that is out of
      * scope of POSIX or SUS, since neither considers shared descriptor
      * tables and this condition does not arise without those.
      */
     fdt = files_fdtable(files);
     tofree = fdt->fd[fd];
     if (!tofree && fd_is_open(fd, fdt))
         goto Ebusy;
     get_file(file);
     rcu_assign_pointer(fdt->fd[fd], file);
     __set_open_fd(fd, fdt);
     if (flags & O_CLOEXEC)
         __set_close_on_exec(fd, fdt);
     else
         __clear_close_on_exec(fd, fdt);
     spin_unlock(&files->file_lock);
 
     if (tofree)
         filp_close(tofree, files);
 
     return fd;
 
 Ebusy:
     spin_unlock(&files->file_lock);
     return -EBUSY;
 }
 
 int replace_fd(unsigned fd, struct file *file, unsigned flags)
 {
     int err;
     struct files_struct *files = current->files;
 
     if (!file)
         return close_fd(fd);
 
     if (fd >= rlimit(RLIMIT_NOFILE))
         return -EBADF;
 
     spin_lock(&files->file_lock);
     err = expand_files(files, fd);
     if (unlikely(err < 0))
         goto out_unlock;
     return do_dup2(files, file, fd, flags);
 
 out_unlock:
     spin_unlock(&files->file_lock);
     return err;
 }
 
 /**
  * __receive_fd() - Install received file into file descriptor table
  * @file: struct file that was received from another process
  * @ufd: __user pointer to write new fd number to
  * @o_flags: the O_* flags to apply to the new fd entry
  *
  * Installs a received file into the file descriptor table, with appropriate
  * checks and count updates. Optionally writes the fd number to userspace, if
  * @ufd is non-NULL.
  *
  * This helper handles its own reference counting of the incoming
  * struct file.
  *
  * Returns newly install fd or -ve on error.
  */
 int __receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
 {
     int new_fd;
     int error;
 
     error = security_file_receive(file);
     if (error)
         return error;
 
     new_fd = get_unused_fd_flags(o_flags);
     if (new_fd < 0)
         return new_fd;
 
     if (ufd) {
         error = put_user(new_fd, ufd);
         if (error) {
             put_unused_fd(new_fd);
             return error;
         }
     }
 
     fd_install(new_fd, get_file(file));
     __receive_sock(file);
     return new_fd;
 }
 
 int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags)
 {
     int error;
 
     error = security_file_receive(file);
     if (error)
         return error;
     error = replace_fd(new_fd, file, o_flags);
     if (error)
         return error;
     __receive_sock(file);
     return new_fd;
 }
 
 int receive_fd(struct file *file, unsigned int o_flags)
 {
     return __receive_fd(file, NULL, o_flags);
 }
 EXPORT_SYMBOL_GPL(receive_fd);
 
 static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
 {
     int err = -EBADF;
     struct file *file;
     struct files_struct *files = current->files;
 
     if ((flags & ~O_CLOEXEC) != 0)
         return -EINVAL;
 
     if (unlikely(oldfd == newfd))
         return -EINVAL;
 
     if (newfd >= rlimit(RLIMIT_NOFILE))
         return -EBADF;
 
     spin_lock(&files->file_lock);
     err = expand_files(files, newfd);
     file = files_lookup_fd_locked(files, oldfd);
     if (unlikely(!file))
         goto Ebadf;
     if (unlikely(err < 0)) {
         if (err == -EMFILE)
             goto Ebadf;
         goto out_unlock;
     }
     return do_dup2(files, file, newfd, flags);
 
 Ebadf:
     err = -EBADF;
 out_unlock:
     spin_unlock(&files->file_lock);
     return err;
 }
 
 SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
 {
     return ksys_dup3(oldfd, newfd, flags);
 }
 
 SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
 {
     if (unlikely(newfd == oldfd)) { /* corner case */
         struct files_struct *files = current->files;
         int retval = oldfd;
 
         rcu_read_lock();
         if (!files_lookup_fd_rcu(files, oldfd))
             retval = -EBADF;
         rcu_read_unlock();
         return retval;
     }
     return ksys_dup3(oldfd, newfd, 0);
 }
 
 SYSCALL_DEFINE1(dup, unsigned int, fildes)
 {
     int ret = -EBADF;
     struct file *file = fget_raw(fildes);
 
     if (file) {
         ret = get_unused_fd_flags(0);
         if (ret >= 0)
             fd_install(ret, file);
         else
             fput(file);
     }
     return ret;
 }
 
 int f_dupfd(unsigned int from, struct file *file, unsigned flags)
 {
     unsigned long nofile = rlimit(RLIMIT_NOFILE);
     int err;
     if (from >= nofile)
         return -EINVAL;
     err = alloc_fd(from, nofile, flags);
     if (err >= 0) {
         get_file(file);
         fd_install(err, file);
     }
     return err;
 }
 
 int iterate_fd(struct files_struct *files, unsigned n,
         int (*f)(const void *, struct file *, unsigned),
         const void *p)
 {
     struct fdtable *fdt;
     int res = 0;
     if (!files)
         return 0;
     spin_lock(&files->file_lock);
     for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
         struct file *file;
         file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
         if (!file)
             continue;
         res = f(p, file, n);
         if (res)
             break;
     }
     spin_unlock(&files->file_lock);
     return res;
 }
 EXPORT_SYMBOL(iterate_fd);

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