1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/fs/file.c
4 *
5 * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes
6 *
7 * Manage the dynamic fd arrays in the process files_struct.
8 */
9
10#include <linux/syscalls.h>
11#include <linux/export.h>
12#include <linux/fs.h>
13#include <linux/kernel.h>
14#include <linux/mm.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>
23#include <linux/file_ref.h>
24#include <net/sock.h>
25#include <linux/init_task.h>
26
27#include "internal.h"
28
29static noinline bool __file_ref_put_badval(file_ref_t *ref, unsigned long cnt)
30{
31 /*
32 * If the reference count was already in the dead zone, then this
33 * put() operation is imbalanced. Warn, put the reference count back to
34 * DEAD and tell the caller to not deconstruct the object.
35 */
36 if (WARN_ONCE(cnt >= FILE_REF_RELEASED, "imbalanced put on file reference count")) {
37 atomic_long_set(v: &ref->refcnt, FILE_REF_DEAD);
38 return false;
39 }
40
41 /*
42 * This is a put() operation on a saturated refcount. Restore the
43 * mean saturation value and tell the caller to not deconstruct the
44 * object.
45 */
46 if (cnt > FILE_REF_MAXREF)
47 atomic_long_set(v: &ref->refcnt, FILE_REF_SATURATED);
48 return false;
49}
50
51/**
52 * __file_ref_put - Slowpath of file_ref_put()
53 * @ref: Pointer to the reference count
54 * @cnt: Current reference count
55 *
56 * Invoked when the reference count is outside of the valid zone.
57 *
58 * Return:
59 * True if this was the last reference with no future references
60 * possible. This signals the caller that it can safely schedule the
61 * object, which is protected by the reference counter, for
62 * deconstruction.
63 *
64 * False if there are still active references or the put() raced
65 * with a concurrent get()/put() pair. Caller is not allowed to
66 * deconstruct the protected object.
67 */
68bool __file_ref_put(file_ref_t *ref, unsigned long cnt)
69{
70 /* Did this drop the last reference? */
71 if (likely(cnt == FILE_REF_NOREF)) {
72 /*
73 * Carefully try to set the reference count to FILE_REF_DEAD.
74 *
75 * This can fail if a concurrent get() operation has
76 * elevated it again or the corresponding put() even marked
77 * it dead already. Both are valid situations and do not
78 * require a retry. If this fails the caller is not
79 * allowed to deconstruct the object.
80 */
81 if (!atomic_long_try_cmpxchg_release(v: &ref->refcnt, old: &cnt, FILE_REF_DEAD))
82 return false;
83
84 /*
85 * The caller can safely schedule the object for
86 * deconstruction. Provide acquire ordering.
87 */
88 smp_acquire__after_ctrl_dep();
89 return true;
90 }
91
92 return __file_ref_put_badval(ref, cnt);
93}
94EXPORT_SYMBOL_GPL(__file_ref_put);
95
96unsigned int sysctl_nr_open __read_mostly = 1024*1024;
97unsigned int sysctl_nr_open_min = BITS_PER_LONG;
98/* our min() is unusable in constant expressions ;-/ */
99#define __const_min(x, y) ((x) < (y) ? (x) : (y))
100unsigned int sysctl_nr_open_max =
101 __const_min(INT_MAX, ~(size_t)0/sizeof(void *)) & -BITS_PER_LONG;
102
103static void __free_fdtable(struct fdtable *fdt)
104{
105 kvfree(addr: fdt->fd);
106 kvfree(addr: fdt->open_fds);
107 kfree(objp: fdt);
108}
109
110static void free_fdtable_rcu(struct rcu_head *rcu)
111{
112 __free_fdtable(container_of(rcu, struct fdtable, rcu));
113}
114
115#define BITBIT_NR(nr) BITS_TO_LONGS(BITS_TO_LONGS(nr))
116#define BITBIT_SIZE(nr) (BITBIT_NR(nr) * sizeof(long))
117
118#define fdt_words(fdt) ((fdt)->max_fds / BITS_PER_LONG) // words in ->open_fds
119/*
120 * Copy 'count' fd bits from the old table to the new table and clear the extra
121 * space if any. This does not copy the file pointers. Called with the files
122 * spinlock held for write.
123 */
124static inline void copy_fd_bitmaps(struct fdtable *nfdt, struct fdtable *ofdt,
125 unsigned int copy_words)
126{
127 unsigned int nwords = fdt_words(nfdt);
128
129 bitmap_copy_and_extend(to: nfdt->open_fds, from: ofdt->open_fds,
130 count: copy_words * BITS_PER_LONG, size: nwords * BITS_PER_LONG);
131 bitmap_copy_and_extend(to: nfdt->close_on_exec, from: ofdt->close_on_exec,
132 count: copy_words * BITS_PER_LONG, size: nwords * BITS_PER_LONG);
133 bitmap_copy_and_extend(to: nfdt->full_fds_bits, from: ofdt->full_fds_bits,
134 count: copy_words, size: nwords);
135}
136
137/*
138 * Copy all file descriptors from the old table to the new, expanded table and
139 * clear the extra space. Called with the files spinlock held for write.
140 */
141static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt)
142{
143 size_t cpy, set;
144
145 BUG_ON(nfdt->max_fds < ofdt->max_fds);
146
147 cpy = ofdt->max_fds * sizeof(struct file *);
148 set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *);
149 memcpy(to: nfdt->fd, from: ofdt->fd, len: cpy);
150 memset(s: (char *)nfdt->fd + cpy, c: 0, n: set);
151
152 copy_fd_bitmaps(nfdt, ofdt, fdt_words(ofdt));
153}
154
155/*
156 * Note how the fdtable bitmap allocations very much have to be a multiple of
157 * BITS_PER_LONG. This is not only because we walk those things in chunks of
158 * 'unsigned long' in some places, but simply because that is how the Linux
159 * kernel bitmaps are defined to work: they are not "bits in an array of bytes",
160 * they are very much "bits in an array of unsigned long".
161 */
162static struct fdtable *alloc_fdtable(unsigned int slots_wanted)
163{
164 struct fdtable *fdt;
165 unsigned int nr;
166 void *data;
167
168 /*
169 * Figure out how many fds we actually want to support in this fdtable.
170 * Allocation steps are keyed to the size of the fdarray, since it
171 * grows far faster than any of the other dynamic data. We try to fit
172 * the fdarray into comfortable page-tuned chunks: starting at 1024B
173 * and growing in powers of two from there on. Since we called only
174 * with slots_wanted > BITS_PER_LONG (embedded instance in files->fdtab
175 * already gives BITS_PER_LONG slots), the above boils down to
176 * 1. use the smallest power of two large enough to give us that many
177 * slots.
178 * 2. on 32bit skip 64 and 128 - the minimal capacity we want there is
179 * 256 slots (i.e. 1Kb fd array).
180 * 3. on 64bit don't skip anything, 1Kb fd array means 128 slots there
181 * and we are never going to be asked for 64 or less.
182 */
183 if (IS_ENABLED(CONFIG_32BIT) && slots_wanted < 256)
184 nr = 256;
185 else
186 nr = roundup_pow_of_two(slots_wanted);
187 /*
188 * Note that this can drive nr *below* what we had passed if sysctl_nr_open
189 * had been set lower between the check in expand_files() and here.
190 *
191 * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise
192 * bitmaps handling below becomes unpleasant, to put it mildly...
193 */
194 if (unlikely(nr > sysctl_nr_open)) {
195 nr = round_down(sysctl_nr_open, BITS_PER_LONG);
196 if (nr < slots_wanted)
197 return ERR_PTR(error: -EMFILE);
198 }
199
200 /*
201 * Check if the allocation size would exceed INT_MAX. kvmalloc_array()
202 * and kvmalloc() will warn if the allocation size is greater than
203 * INT_MAX, as filp_cachep objects are not __GFP_NOWARN.
204 *
205 * This can happen when sysctl_nr_open is set to a very high value and
206 * a process tries to use a file descriptor near that limit. For example,
207 * if sysctl_nr_open is set to 1073741816 (0x3ffffff8) - which is what
208 * systemd typically sets it to - then trying to use a file descriptor
209 * close to that value will require allocating a file descriptor table
210 * that exceeds 8GB in size.
211 */
212 if (unlikely(nr > INT_MAX / sizeof(struct file *)))
213 return ERR_PTR(error: -EMFILE);
214
215 fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL_ACCOUNT);
216 if (!fdt)
217 goto out;
218 fdt->max_fds = nr;
219 data = kvmalloc_array(nr, sizeof(struct file *), GFP_KERNEL_ACCOUNT);
220 if (!data)
221 goto out_fdt;
222 fdt->fd = data;
223
224 data = kvmalloc(max_t(size_t,
225 2 * nr / BITS_PER_BYTE + BITBIT_SIZE(nr), L1_CACHE_BYTES),
226 GFP_KERNEL_ACCOUNT);
227 if (!data)
228 goto out_arr;
229 fdt->open_fds = data;
230 data += nr / BITS_PER_BYTE;
231 fdt->close_on_exec = data;
232 data += nr / BITS_PER_BYTE;
233 fdt->full_fds_bits = data;
234
235 return fdt;
236
237out_arr:
238 kvfree(addr: fdt->fd);
239out_fdt:
240 kfree(objp: fdt);
241out:
242 return ERR_PTR(error: -ENOMEM);
243}
244
245/*
246 * Expand the file descriptor table.
247 * This function will allocate a new fdtable and both fd array and fdset, of
248 * the given size.
249 * Return <0 error code on error; 0 on successful completion.
250 * The files->file_lock should be held on entry, and will be held on exit.
251 */
252static int expand_fdtable(struct files_struct *files, unsigned int nr)
253 __releases(files->file_lock)
254 __acquires(files->file_lock)
255{
256 struct fdtable *new_fdt, *cur_fdt;
257
258 spin_unlock(lock: &files->file_lock);
259 new_fdt = alloc_fdtable(slots_wanted: nr + 1);
260
261 /* make sure all fd_install() have seen resize_in_progress
262 * or have finished their rcu_read_lock_sched() section.
263 */
264 if (atomic_read(v: &files->count) > 1)
265 synchronize_rcu();
266
267 spin_lock(lock: &files->file_lock);
268 if (IS_ERR(ptr: new_fdt))
269 return PTR_ERR(ptr: new_fdt);
270 cur_fdt = files_fdtable(files);
271 BUG_ON(nr < cur_fdt->max_fds);
272 copy_fdtable(nfdt: new_fdt, ofdt: cur_fdt);
273 rcu_assign_pointer(files->fdt, new_fdt);
274 if (cur_fdt != &files->fdtab)
275 call_rcu(head: &cur_fdt->rcu, func: free_fdtable_rcu);
276 /* coupled with smp_rmb() in fd_install() */
277 smp_wmb();
278 return 0;
279}
280
281/*
282 * Expand files.
283 * This function will expand the file structures, if the requested size exceeds
284 * the current capacity and there is room for expansion.
285 * Return <0 error code on error; 0 on success.
286 * The files->file_lock should be held on entry, and will be held on exit.
287 */
288static int expand_files(struct files_struct *files, unsigned int nr)
289 __releases(files->file_lock)
290 __acquires(files->file_lock)
291{
292 struct fdtable *fdt;
293 int error;
294
295repeat:
296 fdt = files_fdtable(files);
297
298 /* Do we need to expand? */
299 if (nr < fdt->max_fds)
300 return 0;
301
302 if (unlikely(files->resize_in_progress)) {
303 spin_unlock(lock: &files->file_lock);
304 wait_event(files->resize_wait, !files->resize_in_progress);
305 spin_lock(lock: &files->file_lock);
306 goto repeat;
307 }
308
309 /* Can we expand? */
310 if (unlikely(nr >= sysctl_nr_open))
311 return -EMFILE;
312
313 /* All good, so we try */
314 files->resize_in_progress = true;
315 error = expand_fdtable(files, nr);
316 files->resize_in_progress = false;
317
318 wake_up_all(&files->resize_wait);
319 return error;
320}
321
322static inline void __set_close_on_exec(unsigned int fd, struct fdtable *fdt,
323 bool set)
324{
325 if (set) {
326 __set_bit(fd, fdt->close_on_exec);
327 } else {
328 if (test_bit(fd, fdt->close_on_exec))
329 __clear_bit(fd, fdt->close_on_exec);
330 }
331}
332
333static inline void __set_open_fd(unsigned int fd, struct fdtable *fdt, bool set)
334{
335 __set_bit(fd, fdt->open_fds);
336 __set_close_on_exec(fd, fdt, set);
337 fd /= BITS_PER_LONG;
338 if (!~fdt->open_fds[fd])
339 __set_bit(fd, fdt->full_fds_bits);
340}
341
342static inline void __clear_open_fd(unsigned int fd, struct fdtable *fdt)
343{
344 __clear_bit(fd, fdt->open_fds);
345 fd /= BITS_PER_LONG;
346 if (test_bit(fd, fdt->full_fds_bits))
347 __clear_bit(fd, fdt->full_fds_bits);
348}
349
350static inline bool fd_is_open(unsigned int fd, const struct fdtable *fdt)
351{
352 return test_bit(fd, fdt->open_fds);
353}
354
355/*
356 * Note that a sane fdtable size always has to be a multiple of
357 * BITS_PER_LONG, since we have bitmaps that are sized by this.
358 *
359 * punch_hole is optional - when close_range() is asked to unshare
360 * and close, we don't need to copy descriptors in that range, so
361 * a smaller cloned descriptor table might suffice if the last
362 * currently opened descriptor falls into that range.
363 */
364static unsigned int sane_fdtable_size(struct fdtable *fdt, struct fd_range *punch_hole)
365{
366 unsigned int last = find_last_bit(addr: fdt->open_fds, size: fdt->max_fds);
367
368 if (last == fdt->max_fds)
369 return NR_OPEN_DEFAULT;
370 if (punch_hole && punch_hole->to >= last && punch_hole->from <= last) {
371 last = find_last_bit(addr: fdt->open_fds, size: punch_hole->from);
372 if (last == punch_hole->from)
373 return NR_OPEN_DEFAULT;
374 }
375 return ALIGN(last + 1, BITS_PER_LONG);
376}
377
378/*
379 * Allocate a new descriptor table and copy contents from the passed in
380 * instance. Returns a pointer to cloned table on success, ERR_PTR()
381 * on failure. For 'punch_hole' see sane_fdtable_size().
382 */
383struct files_struct *dup_fd(struct files_struct *oldf, struct fd_range *punch_hole)
384{
385 struct files_struct *newf;
386 struct file **old_fds, **new_fds;
387 unsigned int open_files, i;
388 struct fdtable *old_fdt, *new_fdt;
389
390 newf = kmem_cache_alloc(files_cachep, GFP_KERNEL);
391 if (!newf)
392 return ERR_PTR(error: -ENOMEM);
393
394 atomic_set(v: &newf->count, i: 1);
395
396 spin_lock_init(&newf->file_lock);
397 newf->resize_in_progress = false;
398 init_waitqueue_head(&newf->resize_wait);
399 newf->next_fd = 0;
400 new_fdt = &newf->fdtab;
401 new_fdt->max_fds = NR_OPEN_DEFAULT;
402 new_fdt->close_on_exec = newf->close_on_exec_init;
403 new_fdt->open_fds = newf->open_fds_init;
404 new_fdt->full_fds_bits = newf->full_fds_bits_init;
405 new_fdt->fd = &newf->fd_array[0];
406
407 spin_lock(lock: &oldf->file_lock);
408 old_fdt = files_fdtable(oldf);
409 open_files = sane_fdtable_size(fdt: old_fdt, punch_hole);
410
411 /*
412 * Check whether we need to allocate a larger fd array and fd set.
413 */
414 while (unlikely(open_files > new_fdt->max_fds)) {
415 spin_unlock(lock: &oldf->file_lock);
416
417 if (new_fdt != &newf->fdtab)
418 __free_fdtable(fdt: new_fdt);
419
420 new_fdt = alloc_fdtable(slots_wanted: open_files);
421 if (IS_ERR(ptr: new_fdt)) {
422 kmem_cache_free(s: files_cachep, objp: newf);
423 return ERR_CAST(ptr: new_fdt);
424 }
425
426 /*
427 * Reacquire the oldf lock and a pointer to its fd table
428 * who knows it may have a new bigger fd table. We need
429 * the latest pointer.
430 */
431 spin_lock(lock: &oldf->file_lock);
432 old_fdt = files_fdtable(oldf);
433 open_files = sane_fdtable_size(fdt: old_fdt, punch_hole);
434 }
435
436 copy_fd_bitmaps(nfdt: new_fdt, ofdt: old_fdt, copy_words: open_files / BITS_PER_LONG);
437
438 old_fds = old_fdt->fd;
439 new_fds = new_fdt->fd;
440
441 /*
442 * We may be racing against fd allocation from other threads using this
443 * files_struct, despite holding ->file_lock.
444 *
445 * alloc_fd() might have already claimed a slot, while fd_install()
446 * did not populate it yet. Note the latter operates locklessly, so
447 * the file can show up as we are walking the array below.
448 *
449 * At the same time we know no files will disappear as all other
450 * operations take the lock.
451 *
452 * Instead of trying to placate userspace racing with itself, we
453 * ref the file if we see it and mark the fd slot as unused otherwise.
454 */
455 for (i = open_files; i != 0; i--) {
456 struct file *f = rcu_dereference_raw(*old_fds++);
457 if (f) {
458 get_file(f);
459 } else {
460 __clear_open_fd(fd: open_files - i, fdt: new_fdt);
461 }
462 rcu_assign_pointer(*new_fds++, f);
463 }
464 spin_unlock(lock: &oldf->file_lock);
465
466 /* clear the remainder */
467 memset(s: new_fds, c: 0, n: (new_fdt->max_fds - open_files) * sizeof(struct file *));
468
469 rcu_assign_pointer(newf->fdt, new_fdt);
470
471 return newf;
472}
473
474static struct fdtable *close_files(struct files_struct * files)
475{
476 /*
477 * It is safe to dereference the fd table without RCU or
478 * ->file_lock because this is the last reference to the
479 * files structure.
480 */
481 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
482 unsigned int i, j = 0;
483
484 for (;;) {
485 unsigned long set;
486 i = j * BITS_PER_LONG;
487 if (i >= fdt->max_fds)
488 break;
489 set = fdt->open_fds[j++];
490 while (set) {
491 if (set & 1) {
492 struct file *file = fdt->fd[i];
493 if (file) {
494 filp_close(file, id: files);
495 cond_resched();
496 }
497 }
498 i++;
499 set >>= 1;
500 }
501 }
502
503 return fdt;
504}
505
506void put_files_struct(struct files_struct *files)
507{
508 if (atomic_dec_and_test(v: &files->count)) {
509 struct fdtable *fdt = close_files(files);
510
511 /* free the arrays if they are not embedded */
512 if (fdt != &files->fdtab)
513 __free_fdtable(fdt);
514 kmem_cache_free(s: files_cachep, objp: files);
515 }
516}
517
518void exit_files(struct task_struct *tsk)
519{
520 struct files_struct * files = tsk->files;
521
522 if (files) {
523 task_lock(p: tsk);
524 tsk->files = NULL;
525 task_unlock(p: tsk);
526 put_files_struct(files);
527 }
528}
529
530struct files_struct init_files = {
531 .count = ATOMIC_INIT(1),
532 .fdt = &init_files.fdtab,
533 .fdtab = {
534 .max_fds = NR_OPEN_DEFAULT,
535 .fd = &init_files.fd_array[0],
536 .close_on_exec = init_files.close_on_exec_init,
537 .open_fds = init_files.open_fds_init,
538 .full_fds_bits = init_files.full_fds_bits_init,
539 },
540 .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock),
541 .resize_wait = __WAIT_QUEUE_HEAD_INITIALIZER(init_files.resize_wait),
542};
543
544static unsigned int find_next_fd(struct fdtable *fdt, unsigned int start)
545{
546 unsigned int maxfd = fdt->max_fds; /* always multiple of BITS_PER_LONG */
547 unsigned int maxbit = maxfd / BITS_PER_LONG;
548 unsigned int bitbit = start / BITS_PER_LONG;
549 unsigned int bit;
550
551 /*
552 * Try to avoid looking at the second level bitmap
553 */
554 bit = find_next_zero_bit(addr: &fdt->open_fds[bitbit], BITS_PER_LONG,
555 offset: start & (BITS_PER_LONG - 1));
556 if (bit < BITS_PER_LONG)
557 return bit + bitbit * BITS_PER_LONG;
558
559 bitbit = find_next_zero_bit(addr: fdt->full_fds_bits, size: maxbit, offset: bitbit) * BITS_PER_LONG;
560 if (bitbit >= maxfd)
561 return maxfd;
562 if (bitbit > start)
563 start = bitbit;
564 return find_next_zero_bit(addr: fdt->open_fds, size: maxfd, offset: start);
565}
566
567/*
568 * allocate a file descriptor, mark it busy.
569 */
570static int alloc_fd(unsigned start, unsigned end, unsigned flags)
571{
572 struct files_struct *files = current->files;
573 unsigned int fd;
574 int error;
575 struct fdtable *fdt;
576
577 spin_lock(lock: &files->file_lock);
578repeat:
579 fdt = files_fdtable(files);
580 fd = start;
581 if (fd < files->next_fd)
582 fd = files->next_fd;
583
584 if (likely(fd < fdt->max_fds))
585 fd = find_next_fd(fdt, start: fd);
586
587 /*
588 * N.B. For clone tasks sharing a files structure, this test
589 * will limit the total number of files that can be opened.
590 */
591 error = -EMFILE;
592 if (unlikely(fd >= end))
593 goto out;
594
595 if (unlikely(fd >= fdt->max_fds)) {
596 error = expand_files(files, nr: fd);
597 if (error < 0)
598 goto out;
599
600 goto repeat;
601 }
602
603 if (start <= files->next_fd)
604 files->next_fd = fd + 1;
605
606 __set_open_fd(fd, fdt, set: flags & O_CLOEXEC);
607 error = fd;
608 VFS_BUG_ON(rcu_access_pointer(fdt->fd[fd]) != NULL);
609
610out:
611 spin_unlock(lock: &files->file_lock);
612 return error;
613}
614
615int __get_unused_fd_flags(unsigned flags, unsigned long nofile)
616{
617 return alloc_fd(start: 0, end: nofile, flags);
618}
619
620int get_unused_fd_flags(unsigned flags)
621{
622 return __get_unused_fd_flags(flags, nofile: rlimit(RLIMIT_NOFILE));
623}
624EXPORT_SYMBOL(get_unused_fd_flags);
625
626static void __put_unused_fd(struct files_struct *files, unsigned int fd)
627{
628 struct fdtable *fdt = files_fdtable(files);
629 __clear_open_fd(fd, fdt);
630 if (fd < files->next_fd)
631 files->next_fd = fd;
632}
633
634void put_unused_fd(unsigned int fd)
635{
636 struct files_struct *files = current->files;
637 spin_lock(lock: &files->file_lock);
638 __put_unused_fd(files, fd);
639 spin_unlock(lock: &files->file_lock);
640}
641
642EXPORT_SYMBOL(put_unused_fd);
643
644/**
645 * fd_install - install a file pointer in the fd array
646 * @fd: file descriptor to install the file in
647 * @file: the file to install
648 *
649 * This consumes the "file" refcount, so callers should treat it
650 * as if they had called fput(file).
651 */
652void fd_install(unsigned int fd, struct file *file)
653{
654 struct files_struct *files = current->files;
655 struct fdtable *fdt;
656
657 if (WARN_ON_ONCE(unlikely(file->f_mode & FMODE_BACKING)))
658 return;
659
660 rcu_read_lock_sched();
661
662 if (unlikely(files->resize_in_progress)) {
663 rcu_read_unlock_sched();
664 spin_lock(lock: &files->file_lock);
665 fdt = files_fdtable(files);
666 VFS_BUG_ON(rcu_access_pointer(fdt->fd[fd]) != NULL);
667 rcu_assign_pointer(fdt->fd[fd], file);
668 spin_unlock(lock: &files->file_lock);
669 return;
670 }
671 /* coupled with smp_wmb() in expand_fdtable() */
672 smp_rmb();
673 fdt = rcu_dereference_sched(files->fdt);
674 VFS_BUG_ON(rcu_access_pointer(fdt->fd[fd]) != NULL);
675 rcu_assign_pointer(fdt->fd[fd], file);
676 rcu_read_unlock_sched();
677}
678
679EXPORT_SYMBOL(fd_install);
680
681/**
682 * file_close_fd_locked - return file associated with fd
683 * @files: file struct to retrieve file from
684 * @fd: file descriptor to retrieve file for
685 *
686 * Doesn't take a separate reference count.
687 *
688 * Context: files_lock must be held.
689 *
690 * Returns: The file associated with @fd (NULL if @fd is not open)
691 */
692struct file *file_close_fd_locked(struct files_struct *files, unsigned fd)
693{
694 struct fdtable *fdt = files_fdtable(files);
695 struct file *file;
696
697 lockdep_assert_held(&files->file_lock);
698
699 if (fd >= fdt->max_fds)
700 return NULL;
701
702 fd = array_index_nospec(fd, fdt->max_fds);
703 file = rcu_dereference_raw(fdt->fd[fd]);
704 if (file) {
705 rcu_assign_pointer(fdt->fd[fd], NULL);
706 __put_unused_fd(files, fd);
707 }
708 return file;
709}
710
711int close_fd(unsigned fd)
712{
713 struct files_struct *files = current->files;
714 struct file *file;
715
716 spin_lock(lock: &files->file_lock);
717 file = file_close_fd_locked(files, fd);
718 spin_unlock(lock: &files->file_lock);
719 if (!file)
720 return -EBADF;
721
722 return filp_close(file, id: files);
723}
724EXPORT_SYMBOL(close_fd);
725
726/**
727 * last_fd - return last valid index into fd table
728 * @fdt: File descriptor table.
729 *
730 * Context: Either rcu read lock or files_lock must be held.
731 *
732 * Returns: Last valid index into fdtable.
733 */
734static inline unsigned last_fd(struct fdtable *fdt)
735{
736 return fdt->max_fds - 1;
737}
738
739static inline void __range_cloexec(struct files_struct *cur_fds,
740 unsigned int fd, unsigned int max_fd)
741{
742 struct fdtable *fdt;
743
744 /* make sure we're using the correct maximum value */
745 spin_lock(lock: &cur_fds->file_lock);
746 fdt = files_fdtable(cur_fds);
747 max_fd = min(last_fd(fdt), max_fd);
748 if (fd <= max_fd)
749 bitmap_set(map: fdt->close_on_exec, start: fd, nbits: max_fd - fd + 1);
750 spin_unlock(lock: &cur_fds->file_lock);
751}
752
753static inline void __range_close(struct files_struct *files, unsigned int fd,
754 unsigned int max_fd)
755{
756 struct file *file;
757 unsigned n;
758
759 spin_lock(lock: &files->file_lock);
760 n = last_fd(files_fdtable(files));
761 max_fd = min(max_fd, n);
762
763 for (; fd <= max_fd; fd++) {
764 file = file_close_fd_locked(files, fd);
765 if (file) {
766 spin_unlock(lock: &files->file_lock);
767 filp_close(file, id: files);
768 cond_resched();
769 spin_lock(lock: &files->file_lock);
770 } else if (need_resched()) {
771 spin_unlock(lock: &files->file_lock);
772 cond_resched();
773 spin_lock(lock: &files->file_lock);
774 }
775 }
776 spin_unlock(lock: &files->file_lock);
777}
778
779/**
780 * sys_close_range() - Close all file descriptors in a given range.
781 *
782 * @fd: starting file descriptor to close
783 * @max_fd: last file descriptor to close
784 * @flags: CLOSE_RANGE flags.
785 *
786 * This closes a range of file descriptors. All file descriptors
787 * from @fd up to and including @max_fd are closed.
788 * Currently, errors to close a given file descriptor are ignored.
789 */
790SYSCALL_DEFINE3(close_range, unsigned int, fd, unsigned int, max_fd,
791 unsigned int, flags)
792{
793 struct task_struct *me = current;
794 struct files_struct *cur_fds = me->files, *fds = NULL;
795
796 if (flags & ~(CLOSE_RANGE_UNSHARE | CLOSE_RANGE_CLOEXEC))
797 return -EINVAL;
798
799 if (fd > max_fd)
800 return -EINVAL;
801
802 if ((flags & CLOSE_RANGE_UNSHARE) && atomic_read(v: &cur_fds->count) > 1) {
803 struct fd_range range = {fd, max_fd}, *punch_hole = &range;
804
805 /*
806 * If the caller requested all fds to be made cloexec we always
807 * copy all of the file descriptors since they still want to
808 * use them.
809 */
810 if (flags & CLOSE_RANGE_CLOEXEC)
811 punch_hole = NULL;
812
813 fds = dup_fd(oldf: cur_fds, punch_hole);
814 if (IS_ERR(ptr: fds))
815 return PTR_ERR(ptr: fds);
816 /*
817 * We used to share our file descriptor table, and have now
818 * created a private one, make sure we're using it below.
819 */
820 swap(cur_fds, fds);
821 }
822
823 if (flags & CLOSE_RANGE_CLOEXEC)
824 __range_cloexec(cur_fds, fd, max_fd);
825 else
826 __range_close(files: cur_fds, fd, max_fd);
827
828 if (fds) {
829 /*
830 * We're done closing the files we were supposed to. Time to install
831 * the new file descriptor table and drop the old one.
832 */
833 task_lock(p: me);
834 me->files = cur_fds;
835 task_unlock(p: me);
836 put_files_struct(files: fds);
837 }
838
839 return 0;
840}
841
842/**
843 * file_close_fd - return file associated with fd
844 * @fd: file descriptor to retrieve file for
845 *
846 * Doesn't take a separate reference count.
847 *
848 * Returns: The file associated with @fd (NULL if @fd is not open)
849 */
850struct file *file_close_fd(unsigned int fd)
851{
852 struct files_struct *files = current->files;
853 struct file *file;
854
855 spin_lock(lock: &files->file_lock);
856 file = file_close_fd_locked(files, fd);
857 spin_unlock(lock: &files->file_lock);
858
859 return file;
860}
861
862void do_close_on_exec(struct files_struct *files)
863{
864 unsigned i;
865 struct fdtable *fdt;
866
867 /* exec unshares first */
868 spin_lock(lock: &files->file_lock);
869 for (i = 0; ; i++) {
870 unsigned long set;
871 unsigned fd = i * BITS_PER_LONG;
872 fdt = files_fdtable(files);
873 if (fd >= fdt->max_fds)
874 break;
875 set = fdt->close_on_exec[i];
876 if (!set)
877 continue;
878 fdt->close_on_exec[i] = 0;
879 for ( ; set ; fd++, set >>= 1) {
880 struct file *file;
881 if (!(set & 1))
882 continue;
883 file = fdt->fd[fd];
884 if (!file)
885 continue;
886 rcu_assign_pointer(fdt->fd[fd], NULL);
887 __put_unused_fd(files, fd);
888 spin_unlock(lock: &files->file_lock);
889 filp_close(file, id: files);
890 cond_resched();
891 spin_lock(lock: &files->file_lock);
892 }
893
894 }
895 spin_unlock(lock: &files->file_lock);
896}
897
898static struct file *__get_file_rcu(struct file __rcu **f)
899{
900 struct file __rcu *file;
901 struct file __rcu *file_reloaded;
902 struct file __rcu *file_reloaded_cmp;
903
904 file = rcu_dereference_raw(*f);
905 if (!file)
906 return NULL;
907
908 if (unlikely(!file_ref_get(&file->f_ref)))
909 return ERR_PTR(error: -EAGAIN);
910
911 file_reloaded = rcu_dereference_raw(*f);
912
913 /*
914 * Ensure that all accesses have a dependency on the load from
915 * rcu_dereference_raw() above so we get correct ordering
916 * between reuse/allocation and the pointer check below.
917 */
918 file_reloaded_cmp = file_reloaded;
919 OPTIMIZER_HIDE_VAR(file_reloaded_cmp);
920
921 /*
922 * file_ref_get() above provided a full memory barrier when we
923 * acquired a reference.
924 *
925 * This is paired with the write barrier from assigning to the
926 * __rcu protected file pointer so that if that pointer still
927 * matches the current file, we know we have successfully
928 * acquired a reference to the right file.
929 *
930 * If the pointers don't match the file has been reallocated by
931 * SLAB_TYPESAFE_BY_RCU.
932 */
933 if (file == file_reloaded_cmp)
934 return file_reloaded;
935
936 fput(file);
937 return ERR_PTR(error: -EAGAIN);
938}
939
940/**
941 * get_file_rcu - try go get a reference to a file under rcu
942 * @f: the file to get a reference on
943 *
944 * This function tries to get a reference on @f carefully verifying that
945 * @f hasn't been reused.
946 *
947 * This function should rarely have to be used and only by users who
948 * understand the implications of SLAB_TYPESAFE_BY_RCU. Try to avoid it.
949 *
950 * Return: Returns @f with the reference count increased or NULL.
951 */
952struct file *get_file_rcu(struct file __rcu **f)
953{
954 for (;;) {
955 struct file __rcu *file;
956
957 file = __get_file_rcu(f);
958 if (!IS_ERR(ptr: file))
959 return file;
960 }
961}
962EXPORT_SYMBOL_GPL(get_file_rcu);
963
964/**
965 * get_file_active - try go get a reference to a file
966 * @f: the file to get a reference on
967 *
968 * In contast to get_file_rcu() the pointer itself isn't part of the
969 * reference counting.
970 *
971 * This function should rarely have to be used and only by users who
972 * understand the implications of SLAB_TYPESAFE_BY_RCU. Try to avoid it.
973 *
974 * Return: Returns @f with the reference count increased or NULL.
975 */
976struct file *get_file_active(struct file **f)
977{
978 struct file __rcu *file;
979
980 rcu_read_lock();
981 file = __get_file_rcu(f);
982 rcu_read_unlock();
983 if (IS_ERR(ptr: file))
984 file = NULL;
985 return file;
986}
987EXPORT_SYMBOL_GPL(get_file_active);
988
989static inline struct file *__fget_files_rcu(struct files_struct *files,
990 unsigned int fd, fmode_t mask)
991{
992 for (;;) {
993 struct file *file;
994 struct fdtable *fdt = rcu_dereference_raw(files->fdt);
995 struct file __rcu **fdentry;
996 unsigned long nospec_mask;
997
998 /* Mask is a 0 for invalid fd's, ~0 for valid ones */
999 nospec_mask = array_index_mask_nospec(fd, fdt->max_fds);
1000
1001 /*
1002 * fdentry points to the 'fd' offset, or fdt->fd[0].
1003 * Loading from fdt->fd[0] is always safe, because the
1004 * array always exists.
1005 */
1006 fdentry = fdt->fd + (fd & nospec_mask);
1007
1008 /* Do the load, then mask any invalid result */
1009 file = rcu_dereference_raw(*fdentry);
1010 file = (void *)(nospec_mask & (unsigned long)file);
1011 if (unlikely(!file))
1012 return NULL;
1013
1014 /*
1015 * Ok, we have a file pointer that was valid at
1016 * some point, but it might have become stale since.
1017 *
1018 * We need to confirm it by incrementing the refcount
1019 * and then check the lookup again.
1020 *
1021 * file_ref_get() gives us a full memory barrier. We
1022 * only really need an 'acquire' one to protect the
1023 * loads below, but we don't have that.
1024 */
1025 if (unlikely(!file_ref_get(&file->f_ref)))
1026 continue;
1027
1028 /*
1029 * Such a race can take two forms:
1030 *
1031 * (a) the file ref already went down to zero and the
1032 * file hasn't been reused yet or the file count
1033 * isn't zero but the file has already been reused.
1034 *
1035 * (b) the file table entry has changed under us.
1036 * Note that we don't need to re-check the 'fdt->fd'
1037 * pointer having changed, because it always goes
1038 * hand-in-hand with 'fdt'.
1039 *
1040 * If so, we need to put our ref and try again.
1041 */
1042 if (unlikely(file != rcu_dereference_raw(*fdentry)) ||
1043 unlikely(rcu_dereference_raw(files->fdt) != fdt)) {
1044 fput(file);
1045 continue;
1046 }
1047
1048 /*
1049 * This isn't the file we're looking for or we're not
1050 * allowed to get a reference to it.
1051 */
1052 if (unlikely(file->f_mode & mask)) {
1053 fput(file);
1054 return NULL;
1055 }
1056
1057 /*
1058 * Ok, we have a ref to the file, and checked that it
1059 * still exists.
1060 */
1061 return file;
1062 }
1063}
1064
1065static struct file *__fget_files(struct files_struct *files, unsigned int fd,
1066 fmode_t mask)
1067{
1068 struct file *file;
1069
1070 rcu_read_lock();
1071 file = __fget_files_rcu(files, fd, mask);
1072 rcu_read_unlock();
1073
1074 return file;
1075}
1076
1077static inline struct file *__fget(unsigned int fd, fmode_t mask)
1078{
1079 return __fget_files(current->files, fd, mask);
1080}
1081
1082struct file *fget(unsigned int fd)
1083{
1084 return __fget(fd, FMODE_PATH);
1085}
1086EXPORT_SYMBOL(fget);
1087
1088struct file *fget_raw(unsigned int fd)
1089{
1090 return __fget(fd, mask: 0);
1091}
1092EXPORT_SYMBOL(fget_raw);
1093
1094struct file *fget_task(struct task_struct *task, unsigned int fd)
1095{
1096 struct file *file = NULL;
1097
1098 task_lock(p: task);
1099 if (task->files)
1100 file = __fget_files(files: task->files, fd, mask: 0);
1101 task_unlock(p: task);
1102
1103 return file;
1104}
1105
1106struct file *fget_task_next(struct task_struct *task, unsigned int *ret_fd)
1107{
1108 /* Must be called with rcu_read_lock held */
1109 struct files_struct *files;
1110 unsigned int fd = *ret_fd;
1111 struct file *file = NULL;
1112
1113 task_lock(p: task);
1114 files = task->files;
1115 if (files) {
1116 rcu_read_lock();
1117 for (; fd < files_fdtable(files)->max_fds; fd++) {
1118 file = __fget_files_rcu(files, fd, mask: 0);
1119 if (file)
1120 break;
1121 }
1122 rcu_read_unlock();
1123 }
1124 task_unlock(p: task);
1125 *ret_fd = fd;
1126 return file;
1127}
1128EXPORT_SYMBOL(fget_task_next);
1129
1130/*
1131 * Lightweight file lookup - no refcnt increment if fd table isn't shared.
1132 *
1133 * You can use this instead of fget if you satisfy all of the following
1134 * conditions:
1135 * 1) You must call fput_light before exiting the syscall and returning control
1136 * to userspace (i.e. you cannot remember the returned struct file * after
1137 * returning to userspace).
1138 * 2) You must not call filp_close on the returned struct file * in between
1139 * calls to fget_light and fput_light.
1140 * 3) You must not clone the current task in between the calls to fget_light
1141 * and fput_light.
1142 *
1143 * The fput_needed flag returned by fget_light should be passed to the
1144 * corresponding fput_light.
1145 *
1146 * (As an exception to rule 2, you can call filp_close between fget_light and
1147 * fput_light provided that you capture a real refcount with get_file before
1148 * the call to filp_close, and ensure that this real refcount is fput *after*
1149 * the fput_light call.)
1150 *
1151 * See also the documentation in rust/kernel/file.rs.
1152 */
1153static inline struct fd __fget_light(unsigned int fd, fmode_t mask)
1154{
1155 struct files_struct *files = current->files;
1156 struct file *file;
1157
1158 /*
1159 * If another thread is concurrently calling close_fd() followed
1160 * by put_files_struct(), we must not observe the old table
1161 * entry combined with the new refcount - otherwise we could
1162 * return a file that is concurrently being freed.
1163 *
1164 * atomic_read_acquire() pairs with atomic_dec_and_test() in
1165 * put_files_struct().
1166 */
1167 if (likely(atomic_read_acquire(&files->count) == 1)) {
1168 file = files_lookup_fd_raw(files, fd);
1169 if (!file || unlikely(file->f_mode & mask))
1170 return EMPTY_FD;
1171 return BORROWED_FD(file);
1172 } else {
1173 file = __fget_files(files, fd, mask);
1174 if (!file)
1175 return EMPTY_FD;
1176 return CLONED_FD(file);
1177 }
1178}
1179struct fd fdget(unsigned int fd)
1180{
1181 return __fget_light(fd, FMODE_PATH);
1182}
1183EXPORT_SYMBOL(fdget);
1184
1185struct fd fdget_raw(unsigned int fd)
1186{
1187 return __fget_light(fd, mask: 0);
1188}
1189
1190/*
1191 * Try to avoid f_pos locking. We only need it if the
1192 * file is marked for FMODE_ATOMIC_POS, and it can be
1193 * accessed multiple ways.
1194 *
1195 * Always do it for directories, because pidfd_getfd()
1196 * can make a file accessible even if it otherwise would
1197 * not be, and for directories this is a correctness
1198 * issue, not a "POSIX requirement".
1199 */
1200static inline bool file_needs_f_pos_lock(struct file *file)
1201{
1202 if (!(file->f_mode & FMODE_ATOMIC_POS))
1203 return false;
1204 if (__file_ref_read_raw(ref: &file->f_ref) != FILE_REF_ONEREF)
1205 return true;
1206 if (file->f_op->iterate_shared)
1207 return true;
1208 return false;
1209}
1210
1211bool file_seek_cur_needs_f_lock(struct file *file)
1212{
1213 if (!(file->f_mode & FMODE_ATOMIC_POS) && !file->f_op->iterate_shared)
1214 return false;
1215
1216 /*
1217 * Note that we are not guaranteed to be called after fdget_pos() on
1218 * this file obj, in which case the caller is expected to provide the
1219 * appropriate locking.
1220 */
1221
1222 return true;
1223}
1224
1225struct fd fdget_pos(unsigned int fd)
1226{
1227 struct fd f = fdget(fd);
1228 struct file *file = fd_file(f);
1229
1230 if (likely(file) && file_needs_f_pos_lock(file)) {
1231 f.word |= FDPUT_POS_UNLOCK;
1232 mutex_lock(lock: &file->f_pos_lock);
1233 }
1234 return f;
1235}
1236
1237void __f_unlock_pos(struct file *f)
1238{
1239 mutex_unlock(lock: &f->f_pos_lock);
1240}
1241
1242/*
1243 * We only lock f_pos if we have threads or if the file might be
1244 * shared with another process. In both cases we'll have an elevated
1245 * file count (done either by fdget() or by fork()).
1246 */
1247
1248void set_close_on_exec(unsigned int fd, int flag)
1249{
1250 struct files_struct *files = current->files;
1251 spin_lock(lock: &files->file_lock);
1252 __set_close_on_exec(fd, files_fdtable(files), set: flag);
1253 spin_unlock(lock: &files->file_lock);
1254}
1255
1256bool get_close_on_exec(unsigned int fd)
1257{
1258 bool res;
1259 rcu_read_lock();
1260 res = close_on_exec(fd, current->files);
1261 rcu_read_unlock();
1262 return res;
1263}
1264
1265static int do_dup2(struct files_struct *files,
1266 struct file *file, unsigned fd, unsigned flags)
1267__releases(&files->file_lock)
1268{
1269 struct file *tofree;
1270 struct fdtable *fdt;
1271
1272 /*
1273 * dup2() is expected to close the file installed in the target fd slot
1274 * (if any). However, userspace hand-picking a fd may be racing against
1275 * its own threads which happened to allocate it in open() et al but did
1276 * not populate it yet.
1277 *
1278 * Broadly speaking we may be racing against the following:
1279 * fd = get_unused_fd_flags(); // fd slot reserved, ->fd[fd] == NULL
1280 * file = hard_work_goes_here();
1281 * fd_install(fd, file); // only now ->fd[fd] == file
1282 *
1283 * It is an invariant that a successfully allocated fd has a NULL entry
1284 * in the array until the matching fd_install().
1285 *
1286 * If we fit the window, we have the fd to populate, yet no target file
1287 * to close. Trying to ignore it and install our new file would violate
1288 * the invariant and make fd_install() overwrite our file.
1289 *
1290 * Things can be done(tm) to handle this. However, the issue does not
1291 * concern legitimate programs and we only need to make sure the kernel
1292 * does not trip over it.
1293 *
1294 * The simplest way out is to return an error if we find ourselves here.
1295 *
1296 * POSIX is silent on the issue, we return -EBUSY.
1297 */
1298 fdt = files_fdtable(files);
1299 fd = array_index_nospec(fd, fdt->max_fds);
1300 tofree = rcu_dereference_raw(fdt->fd[fd]);
1301 if (!tofree && fd_is_open(fd, fdt))
1302 goto Ebusy;
1303 get_file(f: file);
1304 rcu_assign_pointer(fdt->fd[fd], file);
1305 __set_open_fd(fd, fdt, set: flags & O_CLOEXEC);
1306 spin_unlock(lock: &files->file_lock);
1307
1308 if (tofree)
1309 filp_close(tofree, id: files);
1310
1311 return fd;
1312
1313Ebusy:
1314 spin_unlock(lock: &files->file_lock);
1315 return -EBUSY;
1316}
1317
1318int replace_fd(unsigned fd, struct file *file, unsigned flags)
1319{
1320 int err;
1321 struct files_struct *files = current->files;
1322
1323 if (!file)
1324 return close_fd(fd);
1325
1326 if (fd >= rlimit(RLIMIT_NOFILE))
1327 return -EBADF;
1328
1329 spin_lock(lock: &files->file_lock);
1330 err = expand_files(files, nr: fd);
1331 if (unlikely(err < 0))
1332 goto out_unlock;
1333 err = do_dup2(files, file, fd, flags);
1334 if (err < 0)
1335 return err;
1336 return 0;
1337
1338out_unlock:
1339 spin_unlock(lock: &files->file_lock);
1340 return err;
1341}
1342
1343/**
1344 * receive_fd() - Install received file into file descriptor table
1345 * @file: struct file that was received from another process
1346 * @ufd: __user pointer to write new fd number to
1347 * @o_flags: the O_* flags to apply to the new fd entry
1348 *
1349 * Installs a received file into the file descriptor table, with appropriate
1350 * checks and count updates. Optionally writes the fd number to userspace, if
1351 * @ufd is non-NULL.
1352 *
1353 * This helper handles its own reference counting of the incoming
1354 * struct file.
1355 *
1356 * Returns newly install fd or -ve on error.
1357 */
1358int receive_fd(struct file *file, int __user *ufd, unsigned int o_flags)
1359{
1360 int new_fd;
1361 int error;
1362
1363 error = security_file_receive(file);
1364 if (error)
1365 return error;
1366
1367 new_fd = get_unused_fd_flags(o_flags);
1368 if (new_fd < 0)
1369 return new_fd;
1370
1371 if (ufd) {
1372 error = put_user(new_fd, ufd);
1373 if (error) {
1374 put_unused_fd(new_fd);
1375 return error;
1376 }
1377 }
1378
1379 fd_install(new_fd, get_file(f: file));
1380 __receive_sock(file);
1381 return new_fd;
1382}
1383EXPORT_SYMBOL_GPL(receive_fd);
1384
1385int receive_fd_replace(int new_fd, struct file *file, unsigned int o_flags)
1386{
1387 int error;
1388
1389 error = security_file_receive(file);
1390 if (error)
1391 return error;
1392 error = replace_fd(fd: new_fd, file, flags: o_flags);
1393 if (error)
1394 return error;
1395 __receive_sock(file);
1396 return new_fd;
1397}
1398
1399static int ksys_dup3(unsigned int oldfd, unsigned int newfd, int flags)
1400{
1401 int err = -EBADF;
1402 struct file *file;
1403 struct files_struct *files = current->files;
1404
1405 if ((flags & ~O_CLOEXEC) != 0)
1406 return -EINVAL;
1407
1408 if (unlikely(oldfd == newfd))
1409 return -EINVAL;
1410
1411 if (newfd >= rlimit(RLIMIT_NOFILE))
1412 return -EBADF;
1413
1414 spin_lock(lock: &files->file_lock);
1415 err = expand_files(files, nr: newfd);
1416 file = files_lookup_fd_locked(files, fd: oldfd);
1417 if (unlikely(!file))
1418 goto Ebadf;
1419 if (unlikely(err < 0)) {
1420 if (err == -EMFILE)
1421 goto Ebadf;
1422 goto out_unlock;
1423 }
1424 return do_dup2(files, file, fd: newfd, flags);
1425
1426Ebadf:
1427 err = -EBADF;
1428out_unlock:
1429 spin_unlock(lock: &files->file_lock);
1430 return err;
1431}
1432
1433SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags)
1434{
1435 return ksys_dup3(oldfd, newfd, flags);
1436}
1437
1438SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd)
1439{
1440 if (unlikely(newfd == oldfd)) { /* corner case */
1441 struct files_struct *files = current->files;
1442 struct file *f;
1443 int retval = oldfd;
1444
1445 rcu_read_lock();
1446 f = __fget_files_rcu(files, fd: oldfd, mask: 0);
1447 if (!f)
1448 retval = -EBADF;
1449 rcu_read_unlock();
1450 if (f)
1451 fput(f);
1452 return retval;
1453 }
1454 return ksys_dup3(oldfd, newfd, flags: 0);
1455}
1456
1457SYSCALL_DEFINE1(dup, unsigned int, fildes)
1458{
1459 int ret = -EBADF;
1460 struct file *file = fget_raw(fildes);
1461
1462 if (file) {
1463 ret = get_unused_fd_flags(0);
1464 if (ret >= 0)
1465 fd_install(ret, file);
1466 else
1467 fput(file);
1468 }
1469 return ret;
1470}
1471
1472int f_dupfd(unsigned int from, struct file *file, unsigned flags)
1473{
1474 unsigned long nofile = rlimit(RLIMIT_NOFILE);
1475 int err;
1476 if (from >= nofile)
1477 return -EINVAL;
1478 err = alloc_fd(start: from, end: nofile, flags);
1479 if (err >= 0) {
1480 get_file(f: file);
1481 fd_install(err, file);
1482 }
1483 return err;
1484}
1485
1486int iterate_fd(struct files_struct *files, unsigned n,
1487 int (*f)(const void *, struct file *, unsigned),
1488 const void *p)
1489{
1490 struct fdtable *fdt;
1491 int res = 0;
1492 if (!files)
1493 return 0;
1494 spin_lock(lock: &files->file_lock);
1495 for (fdt = files_fdtable(files); n < fdt->max_fds; n++) {
1496 struct file *file;
1497 file = rcu_dereference_check_fdtable(files, fdt->fd[n]);
1498 if (!file)
1499 continue;
1500 res = f(p, file, n);
1501 if (res)
1502 break;
1503 }
1504 spin_unlock(lock: &files->file_lock);
1505 return res;
1506}
1507EXPORT_SYMBOL(iterate_fd);
1508