1 // SPDX-License-Identifier: GPL-2.0
5 * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
7 * Manage the dynamic fd arrays in the process files_struct.
10 #include <linux/syscalls.h>
11 #include <linux/export.h>
13 #include <linux/kernel.h>
15 #include <linux/sched/signal.h>
16 #include <linux/slab.h>
17 #include <linux/file.h>
18 #include <linux/fdtable.h>
19 #include <linux/bitops.h>
20 #include <linux/spinlock.h>
21 #include <linux/rcupdate.h>
22 #include <linux/close_range.h>
24 #include <linux/io_uring.h>
26 unsigned int sysctl_nr_open __read_mostly = 1024*1024;
27 unsigned int sysctl_nr_open_min = BITS_PER_LONG;
28 /* our min() is unusable in constant expressions ;-/ */
29 #define __const_min(x, y) ((x) < (y) ? (x) : (y))
30 unsigned int sysctl_nr_open_max =
31 __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
33 static void __free_fdtable(struct fdtable *fdt)
36 kvfree(fdt->open_fds);
40 static void free_fdtable_rcu(struct rcu_head *rcu)
42 __free_fdtable(container_of(rcu, struct fdtable, rcu));
45 #define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
46 #define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
49 * Copy 'count' fd bits from the old table to the new table and clear the extra
50 * space if any. This does not copy the file pointers. Called with the files
51 * spinlock held for write.
53 static void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
56 unsigned int cpy, set;
58 cpy = count / BITS_PER_BYTE;
59 set = (nfdt->max_fds - count) / BITS_PER_BYTE;
60 memcpy(nfdt->open_fds, ofdt->open_fds, cpy);
61 memset((char *)nfdt->open_fds + cpy, 0, set);
62 memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy);
63 memset((char *)nfdt->close_on_exec + cpy, 0, set);
65 cpy = BITBIT_SIZE(count);
66 set = BITBIT_SIZE(nfdt->max_fds) - cpy;
67 memcpy(nfdt->full_fds_bits, ofdt->full_fds_bits, cpy);
68 memset((char *)nfdt->full_fds_bits + cpy, 0, set);
72 * Copy all file descriptors from the old table to the new, expanded table and
73 * clear the extra space. Called with the files spinlock held for write.
75 static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
79 BUG_ON(nfdt->max_fds < ofdt->max_fds);
81 cpy = ofdt->max_fds * sizeof(struct file *);
82 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
83 memcpy(nfdt->fd, ofdt->fd, cpy);
84 memset((char *)nfdt->fd + cpy, 0, set);
86 copy_fd_bitmaps(nfdt, ofdt, ofdt->max_fds);
89 static struct fdtable * alloc_fdtable(unsigned int nr)
95 * Figure out how many fds we actually want to support in this fdtable.
96 * Allocation steps are keyed to the size of the fdarray, since it
97 * grows far faster than any of the other dynamic data. We try to fit
98 * the fdarray into comfortable page-tuned chunks: starting at 1024B
99 * and growing in powers of two from there on.
101 nr /= (1024 / sizeof(struct file *));
102 nr = roundup_pow_of_two(nr + 1);
103 nr *= (1024 / sizeof(struct file *));
105 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
106 * had been set lower between the check in expand_files() and here. Deal
107 * with that in caller, it's cheaper that way.
109 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
110 * bitmaps handling below becomes unpleasant, to put it mildly...
112 if (unlikely(nr > sysctl_nr_open))
113 nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1;
115 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
119 data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
124 data = kvmalloc(max_t(size_t,
125 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
129 fdt->open_fds = data;
130 data += nr / BITS_PER_BYTE;
131 fdt->close_on_exec = data;
132 data += nr / BITS_PER_BYTE;
133 fdt->full_fds_bits = data;
146 * Expand the file descriptor table.
147 * This function will allocate a new fdtable and both fd array and fdset, of
149 * Return <0 error code on error; 1 on successful completion.
150 * The files->file_lock should be held on entry, and will be held on exit.
152 static int expand_fdtable(struct files_struct *files, unsigned int nr)
153 __releases(files->file_lock)
154 __acquires(files->file_lock)
156 struct fdtable *new_fdt, *cur_fdt;
158 spin_unlock(&files->file_lock);
159 new_fdt = alloc_fdtable(nr);
161 /* make sure all fd_install() have seen resize_in_progress
162 * or have finished their rcu_read_lock_sched() section.
164 if (atomic_read(&files->count) > 1)
167 spin_lock(&files->file_lock);
171 * extremely unlikely race - sysctl_nr_open decreased between the check in
172 * caller and alloc_fdtable(). Cheaper to catch it here...
174 if (unlikely(new_fdt->max_fds <= nr)) {
175 __free_fdtable(new_fdt);
178 cur_fdt = files_fdtable(files);
179 BUG_ON(nr < cur_fdt->max_fds);
180 copy_fdtable(new_fdt, cur_fdt);
181 rcu_assign_pointer(files->fdt, new_fdt);
182 if (cur_fdt != &files->fdtab)
183 call_rcu(&cur_fdt->rcu, free_fdtable_rcu);
184 /* coupled with smp_rmb() in fd_install() */
191 * This function will expand the file structures, if the requested size exceeds
192 * the current capacity and there is room for expansion.
193 * Return <0 error code on error; 0 when nothing done; 1 when files were
194 * expanded and execution may have blocked.
195 * The files->file_lock should be held on entry, and will be held on exit.
197 static int expand_files(struct files_struct *files, unsigned int nr)
198 __releases(files->file_lock)
199 __acquires(files->file_lock)
205 fdt = files_fdtable(files);
207 /* Do we need to expand? */
208 if (nr < fdt->max_fds)
212 if (nr >= sysctl_nr_open)
215 if (unlikely(files->resize_in_progress)) {
216 spin_unlock(&files->file_lock);
218 wait_event(files->resize_wait, !files->resize_in_progress);
219 spin_lock(&files->file_lock);
223 /* All good, so we try */
224 files->resize_in_progress = true;
225 expanded = expand_fdtable(files, nr);
226 files->resize_in_progress = false;
228 wake_up_all(&files->resize_wait);
232 static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt)
234 __set_bit(fd, fdt->close_on_exec);
237 static inline void __clear_close_on_exec(unsigned int fd, struct fdtable *fdt)
239 if (test_bit(fd, fdt->close_on_exec))
240 __clear_bit(fd, fdt->close_on_exec);
243 static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt)
245 __set_bit(fd, fdt->open_fds);
247 if (!~fdt->open_fds[fd])
248 __set_bit(fd, fdt->full_fds_bits);
251 static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
253 __clear_bit(fd, fdt->open_fds);
254 __clear_bit(fd / BITS_PER_LONG, fdt->full_fds_bits);
257 static unsigned int count_open_files(struct fdtable *fdt)
259 unsigned int size = fdt->max_fds;
262 /* Find the last open fd */
263 for (i = size / BITS_PER_LONG; i > 0; ) {
264 if (fdt->open_fds[--i])
267 i = (i + 1) * BITS_PER_LONG;
271 static unsigned int sane_fdtable_size(struct fdtable *fdt, unsigned int max_fds)
275 count = count_open_files(fdt);
276 if (max_fds < NR_OPEN_DEFAULT)
277 max_fds = NR_OPEN_DEFAULT;
278 return min(count, max_fds);
282 * Allocate a new files structure and copy contents from the
283 * passed in files structure.
284 * errorp will be valid only when the returned files_struct is NULL.
286 struct files_struct *dup_fd(struct files_struct *oldf, unsigned int max_fds, int *errorp)
288 struct files_struct *newf;
289 struct file **old_fds, **new_fds;
290 unsigned int open_files, i;
291 struct fdtable *old_fdt, *new_fdt;
294 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
298 atomic_set(&newf->count, 1);
300 spin_lock_init(&newf->file_lock);
301 newf->resize_in_progress = false;
302 init_waitqueue_head(&newf->resize_wait);
304 new_fdt = &newf->fdtab;
305 new_fdt->max_fds = NR_OPEN_DEFAULT;
306 new_fdt->close_on_exec = newf->close_on_exec_init;
307 new_fdt->open_fds = newf->open_fds_init;
308 new_fdt->full_fds_bits = newf->full_fds_bits_init;
309 new_fdt->fd = &newf->fd_array[0];
311 spin_lock(&oldf->file_lock);
312 old_fdt = files_fdtable(oldf);
313 open_files = sane_fdtable_size(old_fdt, max_fds);
316 * Check whether we need to allocate a larger fd array and fd set.
318 while (unlikely(open_files > new_fdt->max_fds)) {
319 spin_unlock(&oldf->file_lock);
321 if (new_fdt != &newf->fdtab)
322 __free_fdtable(new_fdt);
324 new_fdt = alloc_fdtable(open_files - 1);
330 /* beyond sysctl_nr_open; nothing to do */
331 if (unlikely(new_fdt->max_fds < open_files)) {
332 __free_fdtable(new_fdt);
338 * Reacquire the oldf lock and a pointer to its fd table
339 * who knows it may have a new bigger fd table. We need
340 * the latest pointer.
342 spin_lock(&oldf->file_lock);
343 old_fdt = files_fdtable(oldf);
344 open_files = sane_fdtable_size(old_fdt, max_fds);
347 copy_fd_bitmaps(new_fdt, old_fdt, open_files);
349 old_fds = old_fdt->fd;
350 new_fds = new_fdt->fd;
352 for (i = open_files; i != 0; i--) {
353 struct file *f = *old_fds++;
358 * The fd may be claimed in the fd bitmap but not yet
359 * instantiated in the files array if a sibling thread
360 * is partway through open(). So make sure that this
361 * fd is available to the new process.
363 __clear_open_fd(open_files - i, new_fdt);
365 rcu_assign_pointer(*new_fds++, f);
367 spin_unlock(&oldf->file_lock);
369 /* clear the remainder */
370 memset(new_fds, 0, (new_fdt->max_fds - open_files) * sizeof(struct file *));
372 rcu_assign_pointer(newf->fdt, new_fdt);
377 kmem_cache_free(files_cachep, newf);
382 static struct fdtable *close_files(struct files_struct * files)
385 * It is safe to dereference the fd table without RCU or
386 * ->file_lock because this is the last reference to the
389 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
390 unsigned int i, j = 0;
394 i = j * BITS_PER_LONG;
395 if (i >= fdt->max_fds)
397 set = fdt->open_fds[j++];
400 struct file * file = xchg(&fdt->fd[i], NULL);
402 filp_close(file, files);
414 struct files_struct *get_files_struct(struct task_struct *task)
416 struct files_struct *files;
421 atomic_inc(&files->count);
427 void put_files_struct(struct files_struct *files)
429 if (atomic_dec_and_test(&files->count)) {
430 struct fdtable *fdt = close_files(files);
432 /* free the arrays if they are not embedded */
433 if (fdt != &files->fdtab)
435 kmem_cache_free(files_cachep, files);
439 void exit_files(struct task_struct *tsk)
441 struct files_struct * files = tsk->files;
444 io_uring_files_cancel(files);
448 put_files_struct(files);
452 struct files_struct init_files = {
453 .count = ATOMIC_INIT(1),
454 .fdt = &init_files.fdtab,
456 .max_fds = NR_OPEN_DEFAULT,
457 .fd = &init_files.fd_array[0],
458 .close_on_exec = init_files.close_on_exec_init,
459 .open_fds = init_files.open_fds_init,
460 .full_fds_bits = init_files.full_fds_bits_init,
462 .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
463 .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
466 static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
468 unsigned int maxfd = fdt->max_fds;
469 unsigned int maxbit = maxfd / BITS_PER_LONG;
470 unsigned int bitbit = start / BITS_PER_LONG;
472 bitbit = find_next_zero_bit(fdt->full_fds_bits, maxbit, bitbit) * BITS_PER_LONG;
477 return find_next_zero_bit(fdt->open_fds, maxfd, start);
481 * allocate a file descriptor, mark it busy.
483 int __alloc_fd(struct files_struct *files,
484 unsigned start, unsigned end, unsigned flags)
490 spin_lock(&files->file_lock);
492 fdt = files_fdtable(files);
494 if (fd < files->next_fd)
497 if (fd < fdt->max_fds)
498 fd = find_next_fd(fdt, fd);
501 * N.B. For clone tasks sharing a files structure, this test
502 * will limit the total number of files that can be opened.
508 error = expand_files(files, fd);
513 * If we needed to expand the fs array we
514 * might have blocked - try again.
519 if (start <= files->next_fd)
520 files->next_fd = fd + 1;
522 __set_open_fd(fd, fdt);
523 if (flags & O_CLOEXEC)
524 __set_close_on_exec(fd, fdt);
526 __clear_close_on_exec(fd, fdt);
530 if (rcu_access_pointer(fdt->fd[fd]) != NULL) {
531 printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd);
532 rcu_assign_pointer(fdt->fd[fd], NULL);
537 spin_unlock(&files->file_lock);
541 static int alloc_fd(unsigned start, unsigned flags)
543 return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags);
546 int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
548 return __alloc_fd(current->files, 0, nofile, flags);
551 int get_unused_fd_flags(unsigned flags)
553 return __get_unused_fd_flags(flags, rlimit(RLIMIT_NOFILE));
555 EXPORT_SYMBOL(get_unused_fd_flags);
557 static void __put_unused_fd(struct files_struct *files, unsigned int fd)
559 struct fdtable *fdt = files_fdtable(files);
560 __clear_open_fd(fd, fdt);
561 if (fd < files->next_fd)
565 void put_unused_fd(unsigned int fd)
567 struct files_struct *files = current->files;
568 spin_lock(&files->file_lock);
569 __put_unused_fd(files, fd);
570 spin_unlock(&files->file_lock);
573 EXPORT_SYMBOL(put_unused_fd);
576 * Install a file pointer in the fd array.
578 * The VFS is full of places where we drop the files lock between
579 * setting the open_fds bitmap and installing the file in the file
580 * array. At any such point, we are vulnerable to a dup2() race
581 * installing a file in the array before us. We need to detect this and
582 * fput() the struct file we are about to overwrite in this case.
584 * It should never happen - if we allow dup2() do it, _really_ bad things
587 * This consumes the "file" refcount, so callers should treat it
588 * as if they had called fput(file).
591 void fd_install(unsigned int fd, struct file *file)
593 struct files_struct *files = current->files;
596 rcu_read_lock_sched();
598 if (unlikely(files->resize_in_progress)) {
599 rcu_read_unlock_sched();
600 spin_lock(&files->file_lock);
601 fdt = files_fdtable(files);
602 BUG_ON(fdt->fd[fd] != NULL);
603 rcu_assign_pointer(fdt->fd[fd], file);
604 spin_unlock(&files->file_lock);
607 /* coupled with smp_wmb() in expand_fdtable() */
609 fdt = rcu_dereference_sched(files->fdt);
610 BUG_ON(fdt->fd[fd] != NULL);
611 rcu_assign_pointer(fdt->fd[fd], file);
612 rcu_read_unlock_sched();
615 EXPORT_SYMBOL(fd_install);
617 static struct file *pick_file(struct files_struct *files, unsigned fd)
619 struct file *file = NULL;
622 spin_lock(&files->file_lock);
623 fdt = files_fdtable(files);
624 if (fd >= fdt->max_fds)
629 rcu_assign_pointer(fdt->fd[fd], NULL);
630 __put_unused_fd(files, fd);
633 spin_unlock(&files->file_lock);
638 * The same warnings as for __alloc_fd()/__fd_install() apply here...
640 int __close_fd(struct files_struct *files, unsigned fd)
644 file = pick_file(files, fd);
648 return filp_close(file, files);
650 EXPORT_SYMBOL(__close_fd); /* for ksys_close() */
653 * __close_range() - Close all file descriptors in a given range.
655 * @fd: starting file descriptor to close
656 * @max_fd: last file descriptor to close
658 * This closes a range of file descriptors. All file descriptors
659 * from @fd up to and including @max_fd are closed.
661 int __close_range(unsigned fd, unsigned max_fd, unsigned int flags)
663 unsigned int cur_max;
664 struct task_struct *me = current;
665 struct files_struct *cur_fds = me->files, *fds = NULL;
667 if (flags & ~CLOSE_RANGE_UNSHARE)
674 cur_max = files_fdtable(cur_fds)->max_fds;
677 /* cap to last valid index into fdtable */
680 if (flags & CLOSE_RANGE_UNSHARE) {
682 unsigned int max_unshare_fds = NR_OPEN_MAX;
685 * If the requested range is greater than the current maximum,
686 * we're closing everything so only copy all file descriptors
687 * beneath the lowest file descriptor.
689 if (max_fd >= cur_max)
690 max_unshare_fds = fd;
692 ret = unshare_fd(CLONE_FILES, max_unshare_fds, &fds);
697 * We used to share our file descriptor table, and have now
698 * created a private one, make sure we're using it below.
704 max_fd = min(max_fd, cur_max);
705 while (fd <= max_fd) {
708 file = pick_file(cur_fds, fd++);
712 filp_close(file, cur_fds);
718 * We're done closing the files we were supposed to. Time to install
719 * the new file descriptor table and drop the old one.
724 put_files_struct(fds);
731 * variant of __close_fd that gets a ref on the file for later fput.
732 * The caller must ensure that filp_close() called on the file, and then
735 int __close_fd_get_file(unsigned int fd, struct file **res)
737 struct files_struct *files = current->files;
741 spin_lock(&files->file_lock);
742 fdt = files_fdtable(files);
743 if (fd >= fdt->max_fds)
748 rcu_assign_pointer(fdt->fd[fd], NULL);
749 __put_unused_fd(files, fd);
750 spin_unlock(&files->file_lock);
756 spin_unlock(&files->file_lock);
761 void do_close_on_exec(struct files_struct *files)
766 /* exec unshares first */
767 spin_lock(&files->file_lock);
770 unsigned fd = i * BITS_PER_LONG;
771 fdt = files_fdtable(files);
772 if (fd >= fdt->max_fds)
774 set = fdt->close_on_exec[i];
777 fdt->close_on_exec[i] = 0;
778 for ( ; set ; fd++, set >>= 1) {
785 rcu_assign_pointer(fdt->fd[fd], NULL);
786 __put_unused_fd(files, fd);
787 spin_unlock(&files->file_lock);
788 filp_close(file, files);
790 spin_lock(&files->file_lock);
794 spin_unlock(&files->file_lock);
797 static struct file *__fget_files(struct files_struct *files, unsigned int fd,
798 fmode_t mask, unsigned int refs)
804 file = files_lookup_fd_rcu(files, fd);
806 /* File object ref couldn't be taken.
807 * dup2() atomicity guarantee is the reason
808 * we loop to catch the new file (or NULL pointer)
810 if (file->f_mode & mask)
812 else if (!get_file_rcu_many(file, refs))
820 static inline struct file *__fget(unsigned int fd, fmode_t mask,
823 return __fget_files(current->files, fd, mask, refs);
826 struct file *fget_many(unsigned int fd, unsigned int refs)
828 return __fget(fd, FMODE_PATH, refs);
831 struct file *fget(unsigned int fd)
833 return __fget(fd, FMODE_PATH, 1);
837 struct file *fget_raw(unsigned int fd)
839 return __fget(fd, 0, 1);
841 EXPORT_SYMBOL(fget_raw);
843 struct file *fget_task(struct task_struct *task, unsigned int fd)
845 struct file *file = NULL;
849 file = __fget_files(task->files, fd, 0, 1);
855 struct file *task_lookup_fd_rcu(struct task_struct *task, unsigned int fd)
857 /* Must be called with rcu_read_lock held */
858 struct files_struct *files;
859 struct file *file = NULL;
864 file = files_lookup_fd_rcu(files, fd);
870 struct file *task_lookup_next_fd_rcu(struct task_struct *task, unsigned int *ret_fd)
872 /* Must be called with rcu_read_lock held */
873 struct files_struct *files;
874 unsigned int fd = *ret_fd;
875 struct file *file = NULL;
880 for (; fd < files_fdtable(files)->max_fds; fd++) {
881 file = files_lookup_fd_rcu(files, fd);
892 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
894 * You can use this instead of fget if you satisfy all of the following
896 * 1) You must call fput_light before exiting the syscall and returning control
897 * to userspace (i.e. you cannot remember the returned struct file * after
898 * returning to userspace).
899 * 2) You must not call filp_close on the returned struct file * in between
900 * calls to fget_light and fput_light.
901 * 3) You must not clone the current task in between the calls to fget_light
904 * The fput_needed flag returned by fget_light should be passed to the
905 * corresponding fput_light.
907 static unsigned long __fget_light(unsigned int fd, fmode_t mask)
909 struct files_struct *files = current->files;
912 if (atomic_read(&files->count) == 1) {
913 file = files_lookup_fd_raw(files, fd);
914 if (!file || unlikely(file->f_mode & mask))
916 return (unsigned long)file;
918 file = __fget(fd, mask, 1);
921 return FDPUT_FPUT | (unsigned long)file;
924 unsigned long __fdget(unsigned int fd)
926 return __fget_light(fd, FMODE_PATH);
928 EXPORT_SYMBOL(__fdget);
930 unsigned long __fdget_raw(unsigned int fd)
932 return __fget_light(fd, 0);
935 unsigned long __fdget_pos(unsigned int fd)
937 unsigned long v = __fdget(fd);
938 struct file *file = (struct file *)(v & ~3);
940 if (file && (file->f_mode & FMODE_ATOMIC_POS)) {
941 if (file_count(file) > 1) {
942 v |= FDPUT_POS_UNLOCK;
943 mutex_lock(&file->f_pos_lock);
949 void __f_unlock_pos(struct file *f)
951 mutex_unlock(&f->f_pos_lock);
955 * We only lock f_pos if we have threads or if the file might be
956 * shared with another process. In both cases we'll have an elevated
957 * file count (done either by fdget() or by fork()).
960 void set_close_on_exec(unsigned int fd, int flag)
962 struct files_struct *files = current->files;
964 spin_lock(&files->file_lock);
965 fdt = files_fdtable(files);
967 __set_close_on_exec(fd, fdt);
969 __clear_close_on_exec(fd, fdt);
970 spin_unlock(&files->file_lock);
973 bool get_close_on_exec(unsigned int fd)
975 struct files_struct *files = current->files;
979 fdt = files_fdtable(files);
980 res = close_on_exec(fd, fdt);
985 static int do_dup2(struct files_struct *files,
986 struct file *file, unsigned fd, unsigned flags)
987 __releases(&files->file_lock)
993 * We need to detect attempts to do dup2() over allocated but still
994 * not finished descriptor. NB: OpenBSD avoids that at the price of
995 * extra work in their equivalent of fget() - they insert struct
996 * file immediately after grabbing descriptor, mark it larval if
997 * more work (e.g. actual opening) is needed and make sure that
998 * fget() treats larval files as absent. Potentially interesting,
999 * but while extra work in fget() is trivial, locking implications
1000 * and amount of surgery on open()-related paths in VFS are not.
1001 * FreeBSD fails with -EBADF in the same situation, NetBSD "solution"
1002 * deadlocks in rather amusing ways, AFAICS. All of that is out of
1003 * scope of POSIX or SUS, since neither considers shared descriptor
1004 * tables and this condition does not arise without those.
1006 fdt = files_fdtable(files);
1007 tofree = fdt->fd[fd];
1008 if (!tofree && fd_is_open(fd, fdt))
1011 rcu_assign_pointer(fdt->fd[fd], file);
1012 __set_open_fd(fd, fdt);
1013 if (flags & O_CLOEXEC)
1014 __set_close_on_exec(fd, fdt);
1016 __clear_close_on_exec(fd, fdt);
1017 spin_unlock(&files->file_lock);
1020 filp_close(tofree, files);
1025 spin_unlock(&files->file_lock);
1029 int replace_fd(unsigned fd, struct file *file, unsigned flags)
1032 struct files_struct *files = current->files;
1035 return __close_fd(files, fd);
1037 if (fd >= rlimit(RLIMIT_NOFILE))
1040 spin_lock(&files->file_lock);
1041 err = expand_files(files, fd);
1042 if (unlikely(err < 0))
1044 return do_dup2(files, file, fd, flags);
1047 spin_unlock(&files->file_lock);
1052 * __receive_fd() - Install received file into file descriptor table
1054 * @fd: fd to install into (if negative, a new fd will be allocated)
1055 * @file: struct file that was received from another process
1056 * @ufd: __user pointer to write new fd number to
1057 * @o_flags: the O_* flags to apply to the new fd entry
1059 * Installs a received file into the file descriptor table, with appropriate
1060 * checks and count updates. Optionally writes the fd number to userspace, if
1063 * This helper handles its own reference counting of the incoming
1066 * Returns newly install fd or -ve on error.
1068 int __receive_fd(int fd, struct file *file, int __user *ufd, unsigned int o_flags)
1073 error = security_file_receive(file);
1078 new_fd = get_unused_fd_flags(o_flags);
1086 error = put_user(new_fd, ufd);
1089 put_unused_fd(new_fd);
1095 fd_install(new_fd, get_file(file));
1097 error = replace_fd(new_fd, file, o_flags);
1102 /* Bump the sock usage counts, if any. */
1103 __receive_sock(file);
1107 static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
1111 struct files_struct *files = current->files;
1113 if ((flags & ~O_CLOEXEC) != 0)
1116 if (unlikely(oldfd == newfd))
1119 if (newfd >= rlimit(RLIMIT_NOFILE))
1122 spin_lock(&files->file_lock);
1123 err = expand_files(files, newfd);
1124 file = files_lookup_fd_locked(files, oldfd);
1125 if (unlikely(!file))
1127 if (unlikely(err < 0)) {
1132 return do_dup2(files, file, newfd, flags);
1137 spin_unlock(&files->file_lock);
1141 SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
1143 return ksys_dup3(oldfd, newfd, flags);
1146 SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
1148 if (unlikely(newfd == oldfd)) { /* corner case */
1149 struct files_struct *files = current->files;
1153 if (!files_lookup_fd_rcu(files, oldfd))
1158 return ksys_dup3(oldfd, newfd, 0);
1161 SYSCALL_DEFINE1(dup, unsigned int, fildes)
1164 struct file *file = fget_raw(fildes);
1167 ret = get_unused_fd_flags(0);
1169 fd_install(ret, file);
1176 int f_dupfd(unsigned int from, struct file *file, unsigned flags)
1179 if (from >= rlimit(RLIMIT_NOFILE))
1181 err = alloc_fd(from, flags);
1184 fd_install(err, file);
1189 int iterate_fd(struct files_struct *files, unsigned n,
1190 int (*f)(const void *, struct file *, unsigned),
1193 struct fdtable *fdt;
1197 spin_lock(&files->file_lock);
1198 for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1200 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1203 res = f(p, file, n);
1207 spin_unlock(&files->file_lock);
1210 EXPORT_SYMBOL(iterate_fd);