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