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1 | /* |
2 | * linux/fs/file.c |
3 | * |
4 | * Copyright (C) 1998-1999, Stephen Tweedie and Bill Hawes |
5 | * |
6 | * Manage the dynamic fd arrays in the process files_struct. |
7 | */ |
8 | |
9 | #include <linux/syscalls.h> |
10 | #include <linux/export.h> |
11 | #include <linux/fs.h> |
12 | #include <linux/mm.h> |
13 | #include <linux/mmzone.h> |
14 | #include <linux/time.h> |
15 | #include <linux/sched.h> |
16 | #include <linux/slab.h> |
17 | #include <linux/vmalloc.h> |
18 | #include <linux/file.h> |
19 | #include <linux/fdtable.h> |
20 | #include <linux/bitops.h> |
21 | #include <linux/interrupt.h> |
22 | #include <linux/spinlock.h> |
23 | #include <linux/rcupdate.h> |
24 | #include <linux/workqueue.h> |
25 | |
26 | int sysctl_nr_open __read_mostly = 1024*1024; |
27 | int sysctl_nr_open_min = BITS_PER_LONG; |
28 | /* our max() is unusable in constant expressions ;-/ */ |
29 | #define __const_max(x, y) ((x) < (y) ? (x) : (y)) |
30 | int sysctl_nr_open_max = __const_max(INT_MAX, ~(size_t)0/sizeof(void *)) & |
31 | -BITS_PER_LONG; |
32 | |
33 | static void *alloc_fdmem(size_t size) |
34 | { |
35 | /* |
36 | * Very large allocations can stress page reclaim, so fall back to |
37 | * vmalloc() if the allocation size will be considered "large" by the VM. |
38 | */ |
39 | if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { |
40 | void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY); |
41 | if (data != NULL) |
42 | return data; |
43 | } |
44 | return vmalloc(size); |
45 | } |
46 | |
47 | static void free_fdmem(void *ptr) |
48 | { |
49 | is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr); |
50 | } |
51 | |
52 | static void __free_fdtable(struct fdtable *fdt) |
53 | { |
54 | free_fdmem(fdt->fd); |
55 | free_fdmem(fdt->open_fds); |
56 | kfree(fdt); |
57 | } |
58 | |
59 | static void free_fdtable_rcu(struct rcu_head *rcu) |
60 | { |
61 | __free_fdtable(container_of(rcu, struct fdtable, rcu)); |
62 | } |
63 | |
64 | /* |
65 | * Expand the fdset in the files_struct. Called with the files spinlock |
66 | * held for write. |
67 | */ |
68 | static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) |
69 | { |
70 | unsigned int cpy, set; |
71 | |
72 | BUG_ON(nfdt->max_fds < ofdt->max_fds); |
73 | |
74 | cpy = ofdt->max_fds * sizeof(struct file *); |
75 | set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *); |
76 | memcpy(nfdt->fd, ofdt->fd, cpy); |
77 | memset((char *)(nfdt->fd) + cpy, 0, set); |
78 | |
79 | cpy = ofdt->max_fds / BITS_PER_BYTE; |
80 | set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE; |
81 | memcpy(nfdt->open_fds, ofdt->open_fds, cpy); |
82 | memset((char *)(nfdt->open_fds) + cpy, 0, set); |
83 | memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy); |
84 | memset((char *)(nfdt->close_on_exec) + cpy, 0, set); |
85 | } |
86 | |
87 | static struct fdtable * alloc_fdtable(unsigned int nr) |
88 | { |
89 | struct fdtable *fdt; |
90 | void *data; |
91 | |
92 | /* |
93 | * Figure out how many fds we actually want to support in this fdtable. |
94 | * Allocation steps are keyed to the size of the fdarray, since it |
95 | * grows far faster than any of the other dynamic data. We try to fit |
96 | * the fdarray into comfortable page-tuned chunks: starting at 1024B |
97 | * and growing in powers of two from there on. |
98 | */ |
99 | nr /= (1024 / sizeof(struct file *)); |
100 | nr = roundup_pow_of_two(nr + 1); |
101 | nr *= (1024 / sizeof(struct file *)); |
102 | /* |
103 | * Note that this can drive nr *below* what we had passed if sysctl_nr_open |
104 | * had been set lower between the check in expand_files() and here. Deal |
105 | * with that in caller, it's cheaper that way. |
106 | * |
107 | * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise |
108 | * bitmaps handling below becomes unpleasant, to put it mildly... |
109 | */ |
110 | if (unlikely(nr > sysctl_nr_open)) |
111 | nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; |
112 | |
113 | fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL); |
114 | if (!fdt) |
115 | goto out; |
116 | fdt->max_fds = nr; |
117 | data = alloc_fdmem(nr * sizeof(struct file *)); |
118 | if (!data) |
119 | goto out_fdt; |
120 | fdt->fd = data; |
121 | |
122 | data = alloc_fdmem(max_t(size_t, |
123 | 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); |
124 | if (!data) |
125 | goto out_arr; |
126 | fdt->open_fds = data; |
127 | data += nr / BITS_PER_BYTE; |
128 | fdt->close_on_exec = data; |
129 | |
130 | return fdt; |
131 | |
132 | out_arr: |
133 | free_fdmem(fdt->fd); |
134 | out_fdt: |
135 | kfree(fdt); |
136 | out: |
137 | return NULL; |
138 | } |
139 | |
140 | /* |
141 | * Expand the file descriptor table. |
142 | * This function will allocate a new fdtable and both fd array and fdset, of |
143 | * the given size. |
144 | * Return <0 error code on error; 1 on successful completion. |
145 | * The files->file_lock should be held on entry, and will be held on exit. |
146 | */ |
147 | static int expand_fdtable(struct files_struct *files, int nr) |
148 | __releases(files->file_lock) |
149 | __acquires(files->file_lock) |
150 | { |
151 | struct fdtable *new_fdt, *cur_fdt; |
152 | |
153 | spin_unlock(&files->file_lock); |
154 | new_fdt = alloc_fdtable(nr); |
155 | spin_lock(&files->file_lock); |
156 | if (!new_fdt) |
157 | return -ENOMEM; |
158 | /* |
159 | * extremely unlikely race - sysctl_nr_open decreased between the check in |
160 | * caller and alloc_fdtable(). Cheaper to catch it here... |
161 | */ |
162 | if (unlikely(new_fdt->max_fds <= nr)) { |
163 | __free_fdtable(new_fdt); |
164 | return -EMFILE; |
165 | } |
166 | /* |
167 | * Check again since another task may have expanded the fd table while |
168 | * we dropped the lock |
169 | */ |
170 | cur_fdt = files_fdtable(files); |
171 | if (nr >= cur_fdt->max_fds) { |
172 | /* Continue as planned */ |
173 | copy_fdtable(new_fdt, cur_fdt); |
174 | rcu_assign_pointer(files->fdt, new_fdt); |
175 | if (cur_fdt != &files->fdtab) |
176 | call_rcu(&cur_fdt->rcu, free_fdtable_rcu); |
177 | } else { |
178 | /* Somebody else expanded, so undo our attempt */ |
179 | __free_fdtable(new_fdt); |
180 | } |
181 | return 1; |
182 | } |
183 | |
184 | /* |
185 | * Expand files. |
186 | * This function will expand the file structures, if the requested size exceeds |
187 | * the current capacity and there is room for expansion. |
188 | * Return <0 error code on error; 0 when nothing done; 1 when files were |
189 | * expanded and execution may have blocked. |
190 | * The files->file_lock should be held on entry, and will be held on exit. |
191 | */ |
192 | static int expand_files(struct files_struct *files, int nr) |
193 | { |
194 | struct fdtable *fdt; |
195 | |
196 | fdt = files_fdtable(files); |
197 | |
198 | /* Do we need to expand? */ |
199 | if (nr < fdt->max_fds) |
200 | return 0; |
201 | |
202 | /* Can we expand? */ |
203 | if (nr >= sysctl_nr_open) |
204 | return -EMFILE; |
205 | |
206 | /* All good, so we try */ |
207 | return expand_fdtable(files, nr); |
208 | } |
209 | |
210 | static inline void __set_close_on_exec(int fd, struct fdtable *fdt) |
211 | { |
212 | __set_bit(fd, fdt->close_on_exec); |
213 | } |
214 | |
215 | static inline void __clear_close_on_exec(int fd, struct fdtable *fdt) |
216 | { |
217 | __clear_bit(fd, fdt->close_on_exec); |
218 | } |
219 | |
220 | static inline void __set_open_fd(int fd, struct fdtable *fdt) |
221 | { |
222 | __set_bit(fd, fdt->open_fds); |
223 | } |
224 | |
225 | static inline void __clear_open_fd(int fd, struct fdtable *fdt) |
226 | { |
227 | __clear_bit(fd, fdt->open_fds); |
228 | } |
229 | |
230 | static int count_open_files(struct fdtable *fdt) |
231 | { |
232 | int size = fdt->max_fds; |
233 | int i; |
234 | |
235 | /* Find the last open fd */ |
236 | for (i = size / BITS_PER_LONG; i > 0; ) { |
237 | if (fdt->open_fds[--i]) |
238 | break; |
239 | } |
240 | i = (i + 1) * BITS_PER_LONG; |
241 | return i; |
242 | } |
243 | |
244 | /* |
245 | * Allocate a new files structure and copy contents from the |
246 | * passed in files structure. |
247 | * errorp will be valid only when the returned files_struct is NULL. |
248 | */ |
249 | struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) |
250 | { |
251 | struct files_struct *newf; |
252 | struct file **old_fds, **new_fds; |
253 | int open_files, size, i; |
254 | struct fdtable *old_fdt, *new_fdt; |
255 | |
256 | *errorp = -ENOMEM; |
257 | newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); |
258 | if (!newf) |
259 | goto out; |
260 | |
261 | atomic_set(&newf->count, 1); |
262 | |
263 | spin_lock_init(&newf->file_lock); |
264 | newf->next_fd = 0; |
265 | new_fdt = &newf->fdtab; |
266 | new_fdt->max_fds = NR_OPEN_DEFAULT; |
267 | new_fdt->close_on_exec = newf->close_on_exec_init; |
268 | new_fdt->open_fds = newf->open_fds_init; |
269 | new_fdt->fd = &newf->fd_array[0]; |
270 | |
271 | spin_lock(&oldf->file_lock); |
272 | old_fdt = files_fdtable(oldf); |
273 | open_files = count_open_files(old_fdt); |
274 | |
275 | /* |
276 | * Check whether we need to allocate a larger fd array and fd set. |
277 | */ |
278 | while (unlikely(open_files > new_fdt->max_fds)) { |
279 | spin_unlock(&oldf->file_lock); |
280 | |
281 | if (new_fdt != &newf->fdtab) |
282 | __free_fdtable(new_fdt); |
283 | |
284 | new_fdt = alloc_fdtable(open_files - 1); |
285 | if (!new_fdt) { |
286 | *errorp = -ENOMEM; |
287 | goto out_release; |
288 | } |
289 | |
290 | /* beyond sysctl_nr_open; nothing to do */ |
291 | if (unlikely(new_fdt->max_fds < open_files)) { |
292 | __free_fdtable(new_fdt); |
293 | *errorp = -EMFILE; |
294 | goto out_release; |
295 | } |
296 | |
297 | /* |
298 | * Reacquire the oldf lock and a pointer to its fd table |
299 | * who knows it may have a new bigger fd table. We need |
300 | * the latest pointer. |
301 | */ |
302 | spin_lock(&oldf->file_lock); |
303 | old_fdt = files_fdtable(oldf); |
304 | open_files = count_open_files(old_fdt); |
305 | } |
306 | |
307 | old_fds = old_fdt->fd; |
308 | new_fds = new_fdt->fd; |
309 | |
310 | memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8); |
311 | memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8); |
312 | |
313 | for (i = open_files; i != 0; i--) { |
314 | struct file *f = *old_fds++; |
315 | if (f) { |
316 | get_file(f); |
317 | } else { |
318 | /* |
319 | * The fd may be claimed in the fd bitmap but not yet |
320 | * instantiated in the files array if a sibling thread |
321 | * is partway through open(). So make sure that this |
322 | * fd is available to the new process. |
323 | */ |
324 | __clear_open_fd(open_files - i, new_fdt); |
325 | } |
326 | rcu_assign_pointer(*new_fds++, f); |
327 | } |
328 | spin_unlock(&oldf->file_lock); |
329 | |
330 | /* compute the remainder to be cleared */ |
331 | size = (new_fdt->max_fds - open_files) * sizeof(struct file *); |
332 | |
333 | /* This is long word aligned thus could use a optimized version */ |
334 | memset(new_fds, 0, size); |
335 | |
336 | if (new_fdt->max_fds > open_files) { |
337 | int left = (new_fdt->max_fds - open_files) / 8; |
338 | int start = open_files / BITS_PER_LONG; |
339 | |
340 | memset(&new_fdt->open_fds[start], 0, left); |
341 | memset(&new_fdt->close_on_exec[start], 0, left); |
342 | } |
343 | |
344 | rcu_assign_pointer(newf->fdt, new_fdt); |
345 | |
346 | return newf; |
347 | |
348 | out_release: |
349 | kmem_cache_free(files_cachep, newf); |
350 | out: |
351 | return NULL; |
352 | } |
353 | |
354 | static struct fdtable *close_files(struct files_struct * files) |
355 | { |
356 | /* |
357 | * It is safe to dereference the fd table without RCU or |
358 | * ->file_lock because this is the last reference to the |
359 | * files structure. |
360 | */ |
361 | struct fdtable *fdt = rcu_dereference_raw(files->fdt); |
362 | int i, j = 0; |
363 | |
364 | for (;;) { |
365 | unsigned long set; |
366 | i = j * BITS_PER_LONG; |
367 | if (i >= fdt->max_fds) |
368 | break; |
369 | set = fdt->open_fds[j++]; |
370 | while (set) { |
371 | if (set & 1) { |
372 | struct file * file = xchg(&fdt->fd[i], NULL); |
373 | if (file) { |
374 | filp_close(file, files); |
375 | cond_resched(); |
376 | } |
377 | } |
378 | i++; |
379 | set >>= 1; |
380 | } |
381 | } |
382 | |
383 | return fdt; |
384 | } |
385 | |
386 | struct files_struct *get_files_struct(struct task_struct *task) |
387 | { |
388 | struct files_struct *files; |
389 | |
390 | task_lock(task); |
391 | files = task->files; |
392 | if (files) |
393 | atomic_inc(&files->count); |
394 | task_unlock(task); |
395 | |
396 | return files; |
397 | } |
398 | |
399 | void put_files_struct(struct files_struct *files) |
400 | { |
401 | if (atomic_dec_and_test(&files->count)) { |
402 | struct fdtable *fdt = close_files(files); |
403 | |
404 | /* free the arrays if they are not embedded */ |
405 | if (fdt != &files->fdtab) |
406 | __free_fdtable(fdt); |
407 | kmem_cache_free(files_cachep, files); |
408 | } |
409 | } |
410 | |
411 | void reset_files_struct(struct files_struct *files) |
412 | { |
413 | struct task_struct *tsk = current; |
414 | struct files_struct *old; |
415 | |
416 | old = tsk->files; |
417 | task_lock(tsk); |
418 | tsk->files = files; |
419 | task_unlock(tsk); |
420 | put_files_struct(old); |
421 | } |
422 | |
423 | void exit_files(struct task_struct *tsk) |
424 | { |
425 | struct files_struct * files = tsk->files; |
426 | |
427 | if (files) { |
428 | task_lock(tsk); |
429 | tsk->files = NULL; |
430 | task_unlock(tsk); |
431 | put_files_struct(files); |
432 | } |
433 | } |
434 | |
435 | struct files_struct init_files = { |
436 | .count = ATOMIC_INIT(1), |
437 | .fdt = &init_files.fdtab, |
438 | .fdtab = { |
439 | .max_fds = NR_OPEN_DEFAULT, |
440 | .fd = &init_files.fd_array[0], |
441 | .close_on_exec = init_files.close_on_exec_init, |
442 | .open_fds = init_files.open_fds_init, |
443 | }, |
444 | .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock), |
445 | }; |
446 | |
447 | /* |
448 | * allocate a file descriptor, mark it busy. |
449 | */ |
450 | int __alloc_fd(struct files_struct *files, |
451 | unsigned start, unsigned end, unsigned flags) |
452 | { |
453 | unsigned int fd; |
454 | int error; |
455 | struct fdtable *fdt; |
456 | |
457 | spin_lock(&files->file_lock); |
458 | repeat: |
459 | fdt = files_fdtable(files); |
460 | fd = start; |
461 | if (fd < files->next_fd) |
462 | fd = files->next_fd; |
463 | |
464 | if (fd < fdt->max_fds) |
465 | fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); |
466 | |
467 | /* |
468 | * N.B. For clone tasks sharing a files structure, this test |
469 | * will limit the total number of files that can be opened. |
470 | */ |
471 | error = -EMFILE; |
472 | if (fd >= end) |
473 | goto out; |
474 | |
475 | error = expand_files(files, fd); |
476 | if (error < 0) |
477 | goto out; |
478 | |
479 | /* |
480 | * If we needed to expand the fs array we |
481 | * might have blocked - try again. |
482 | */ |
483 | if (error) |
484 | goto repeat; |
485 | |
486 | if (start <= files->next_fd) |
487 | files->next_fd = fd + 1; |
488 | |
489 | __set_open_fd(fd, fdt); |
490 | if (flags & O_CLOEXEC) |
491 | __set_close_on_exec(fd, fdt); |
492 | else |
493 | __clear_close_on_exec(fd, fdt); |
494 | error = fd; |
495 | #if 1 |
496 | /* Sanity check */ |
497 | if (rcu_access_pointer(fdt->fd[fd]) != NULL) { |
498 | printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); |
499 | rcu_assign_pointer(fdt->fd[fd], NULL); |
500 | } |
501 | #endif |
502 | |
503 | out: |
504 | spin_unlock(&files->file_lock); |
505 | return error; |
506 | } |
507 | |
508 | static int alloc_fd(unsigned start, unsigned flags) |
509 | { |
510 | return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags); |
511 | } |
512 | |
513 | int get_unused_fd_flags(unsigned flags) |
514 | { |
515 | return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags); |
516 | } |
517 | EXPORT_SYMBOL(get_unused_fd_flags); |
518 | |
519 | static void __put_unused_fd(struct files_struct *files, unsigned int fd) |
520 | { |
521 | struct fdtable *fdt = files_fdtable(files); |
522 | __clear_open_fd(fd, fdt); |
523 | if (fd < files->next_fd) |
524 | files->next_fd = fd; |
525 | } |
526 | |
527 | void put_unused_fd(unsigned int fd) |
528 | { |
529 | struct files_struct *files = current->files; |
530 | spin_lock(&files->file_lock); |
531 | __put_unused_fd(files, fd); |
532 | spin_unlock(&files->file_lock); |
533 | } |
534 | |
535 | EXPORT_SYMBOL(put_unused_fd); |
536 | |
537 | /* |
538 | * Install a file pointer in the fd array. |
539 | * |
540 | * The VFS is full of places where we drop the files lock between |
541 | * setting the open_fds bitmap and installing the file in the file |
542 | * array. At any such point, we are vulnerable to a dup2() race |
543 | * installing a file in the array before us. We need to detect this and |
544 | * fput() the struct file we are about to overwrite in this case. |
545 | * |
546 | * It should never happen - if we allow dup2() do it, _really_ bad things |
547 | * will follow. |
548 | * |
549 | * NOTE: __fd_install() variant is really, really low-level; don't |
550 | * use it unless you are forced to by truly lousy API shoved down |
551 | * your throat. 'files' *MUST* be either current->files or obtained |
552 | * by get_files_struct(current) done by whoever had given it to you, |
553 | * or really bad things will happen. Normally you want to use |
554 | * fd_install() instead. |
555 | */ |
556 | |
557 | void __fd_install(struct files_struct *files, unsigned int fd, |
558 | struct file *file) |
559 | { |
560 | struct fdtable *fdt; |
561 | spin_lock(&files->file_lock); |
562 | fdt = files_fdtable(files); |
563 | BUG_ON(fdt->fd[fd] != NULL); |
564 | rcu_assign_pointer(fdt->fd[fd], file); |
565 | spin_unlock(&files->file_lock); |
566 | } |
567 | |
568 | void fd_install(unsigned int fd, struct file *file) |
569 | { |
570 | __fd_install(current->files, fd, file); |
571 | } |
572 | |
573 | EXPORT_SYMBOL(fd_install); |
574 | |
575 | /* |
576 | * The same warnings as for __alloc_fd()/__fd_install() apply here... |
577 | */ |
578 | int __close_fd(struct files_struct *files, unsigned fd) |
579 | { |
580 | struct file *file; |
581 | struct fdtable *fdt; |
582 | |
583 | spin_lock(&files->file_lock); |
584 | fdt = files_fdtable(files); |
585 | if (fd >= fdt->max_fds) |
586 | goto out_unlock; |
587 | file = fdt->fd[fd]; |
588 | if (!file) |
589 | goto out_unlock; |
590 | rcu_assign_pointer(fdt->fd[fd], NULL); |
591 | __clear_close_on_exec(fd, fdt); |
592 | __put_unused_fd(files, fd); |
593 | spin_unlock(&files->file_lock); |
594 | return filp_close(file, files); |
595 | |
596 | out_unlock: |
597 | spin_unlock(&files->file_lock); |
598 | return -EBADF; |
599 | } |
600 | |
601 | void do_close_on_exec(struct files_struct *files) |
602 | { |
603 | unsigned i; |
604 | struct fdtable *fdt; |
605 | |
606 | /* exec unshares first */ |
607 | spin_lock(&files->file_lock); |
608 | for (i = 0; ; i++) { |
609 | unsigned long set; |
610 | unsigned fd = i * BITS_PER_LONG; |
611 | fdt = files_fdtable(files); |
612 | if (fd >= fdt->max_fds) |
613 | break; |
614 | set = fdt->close_on_exec[i]; |
615 | if (!set) |
616 | continue; |
617 | fdt->close_on_exec[i] = 0; |
618 | for ( ; set ; fd++, set >>= 1) { |
619 | struct file *file; |
620 | if (!(set & 1)) |
621 | continue; |
622 | file = fdt->fd[fd]; |
623 | if (!file) |
624 | continue; |
625 | rcu_assign_pointer(fdt->fd[fd], NULL); |
626 | __put_unused_fd(files, fd); |
627 | spin_unlock(&files->file_lock); |
628 | filp_close(file, files); |
629 | cond_resched(); |
630 | spin_lock(&files->file_lock); |
631 | } |
632 | |
633 | } |
634 | spin_unlock(&files->file_lock); |
635 | } |
636 | |
637 | static struct file *__fget(unsigned int fd, fmode_t mask) |
638 | { |
639 | struct files_struct *files = current->files; |
640 | struct file *file; |
641 | |
642 | rcu_read_lock(); |
643 | file = fcheck_files(files, fd); |
644 | if (file) { |
645 | /* File object ref couldn't be taken */ |
646 | if ((file->f_mode & mask) || |
647 | !atomic_long_inc_not_zero(&file->f_count)) |
648 | file = NULL; |
649 | } |
650 | rcu_read_unlock(); |
651 | |
652 | return file; |
653 | } |
654 | |
655 | struct file *fget(unsigned int fd) |
656 | { |
657 | return __fget(fd, FMODE_PATH); |
658 | } |
659 | EXPORT_SYMBOL(fget); |
660 | |
661 | struct file *fget_raw(unsigned int fd) |
662 | { |
663 | return __fget(fd, 0); |
664 | } |
665 | EXPORT_SYMBOL(fget_raw); |
666 | |
667 | /* |
668 | * Lightweight file lookup - no refcnt increment if fd table isn't shared. |
669 | * |
670 | * You can use this instead of fget if you satisfy all of the following |
671 | * conditions: |
672 | * 1) You must call fput_light before exiting the syscall and returning control |
673 | * to userspace (i.e. you cannot remember the returned struct file * after |
674 | * returning to userspace). |
675 | * 2) You must not call filp_close on the returned struct file * in between |
676 | * calls to fget_light and fput_light. |
677 | * 3) You must not clone the current task in between the calls to fget_light |
678 | * and fput_light. |
679 | * |
680 | * The fput_needed flag returned by fget_light should be passed to the |
681 | * corresponding fput_light. |
682 | */ |
683 | static unsigned long __fget_light(unsigned int fd, fmode_t mask) |
684 | { |
685 | struct files_struct *files = current->files; |
686 | struct file *file; |
687 | |
688 | if (atomic_read(&files->count) == 1) { |
689 | file = __fcheck_files(files, fd); |
690 | if (!file || unlikely(file->f_mode & mask)) |
691 | return 0; |
692 | return (unsigned long)file; |
693 | } else { |
694 | file = __fget(fd, mask); |
695 | if (!file) |
696 | return 0; |
697 | return FDPUT_FPUT | (unsigned long)file; |
698 | } |
699 | } |
700 | unsigned long __fdget(unsigned int fd) |
701 | { |
702 | return __fget_light(fd, FMODE_PATH); |
703 | } |
704 | EXPORT_SYMBOL(__fdget); |
705 | |
706 | unsigned long __fdget_raw(unsigned int fd) |
707 | { |
708 | return __fget_light(fd, 0); |
709 | } |
710 | |
711 | unsigned long __fdget_pos(unsigned int fd) |
712 | { |
713 | unsigned long v = __fdget(fd); |
714 | struct file *file = (struct file *)(v & ~3); |
715 | |
716 | if (file && (file->f_mode & FMODE_ATOMIC_POS)) { |
717 | if (file_count(file) > 1) { |
718 | v |= FDPUT_POS_UNLOCK; |
719 | mutex_lock(&file->f_pos_lock); |
720 | } |
721 | } |
722 | return v; |
723 | } |
724 | |
725 | /* |
726 | * We only lock f_pos if we have threads or if the file might be |
727 | * shared with another process. In both cases we'll have an elevated |
728 | * file count (done either by fdget() or by fork()). |
729 | */ |
730 | |
731 | void set_close_on_exec(unsigned int fd, int flag) |
732 | { |
733 | struct files_struct *files = current->files; |
734 | struct fdtable *fdt; |
735 | spin_lock(&files->file_lock); |
736 | fdt = files_fdtable(files); |
737 | if (flag) |
738 | __set_close_on_exec(fd, fdt); |
739 | else |
740 | __clear_close_on_exec(fd, fdt); |
741 | spin_unlock(&files->file_lock); |
742 | } |
743 | |
744 | bool get_close_on_exec(unsigned int fd) |
745 | { |
746 | struct files_struct *files = current->files; |
747 | struct fdtable *fdt; |
748 | bool res; |
749 | rcu_read_lock(); |
750 | fdt = files_fdtable(files); |
751 | res = close_on_exec(fd, fdt); |
752 | rcu_read_unlock(); |
753 | return res; |
754 | } |
755 | |
756 | static int do_dup2(struct files_struct *files, |
757 | struct file *file, unsigned fd, unsigned flags) |
758 | { |
759 | struct file *tofree; |
760 | struct fdtable *fdt; |
761 | |
762 | /* |
763 | * We need to detect attempts to do dup2() over allocated but still |
764 | * not finished descriptor. NB: OpenBSD avoids that at the price of |
765 | * extra work in their equivalent of fget() - they insert struct |
766 | * file immediately after grabbing descriptor, mark it larval if |
767 | * more work (e.g. actual opening) is needed and make sure that |
768 | * fget() treats larval files as absent. Potentially interesting, |
769 | * but while extra work in fget() is trivial, locking implications |
770 | * and amount of surgery on open()-related paths in VFS are not. |
771 | * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" |
772 | * deadlocks in rather amusing ways, AFAICS. All of that is out of |
773 | * scope of POSIX or SUS, since neither considers shared descriptor |
774 | * tables and this condition does not arise without those. |
775 | */ |
776 | fdt = files_fdtable(files); |
777 | tofree = fdt->fd[fd]; |
778 | if (!tofree && fd_is_open(fd, fdt)) |
779 | goto Ebusy; |
780 | get_file(file); |
781 | rcu_assign_pointer(fdt->fd[fd], file); |
782 | __set_open_fd(fd, fdt); |
783 | if (flags & O_CLOEXEC) |
784 | __set_close_on_exec(fd, fdt); |
785 | else |
786 | __clear_close_on_exec(fd, fdt); |
787 | spin_unlock(&files->file_lock); |
788 | |
789 | if (tofree) |
790 | filp_close(tofree, files); |
791 | |
792 | return fd; |
793 | |
794 | Ebusy: |
795 | spin_unlock(&files->file_lock); |
796 | return -EBUSY; |
797 | } |
798 | |
799 | int replace_fd(unsigned fd, struct file *file, unsigned flags) |
800 | { |
801 | int err; |
802 | struct files_struct *files = current->files; |
803 | |
804 | if (!file) |
805 | return __close_fd(files, fd); |
806 | |
807 | if (fd >= rlimit(RLIMIT_NOFILE)) |
808 | return -EBADF; |
809 | |
810 | spin_lock(&files->file_lock); |
811 | err = expand_files(files, fd); |
812 | if (unlikely(err < 0)) |
813 | goto out_unlock; |
814 | return do_dup2(files, file, fd, flags); |
815 | |
816 | out_unlock: |
817 | spin_unlock(&files->file_lock); |
818 | return err; |
819 | } |
820 | |
821 | SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) |
822 | { |
823 | int err = -EBADF; |
824 | struct file *file; |
825 | struct files_struct *files = current->files; |
826 | |
827 | if ((flags & ~O_CLOEXEC) != 0) |
828 | return -EINVAL; |
829 | |
830 | if (unlikely(oldfd == newfd)) |
831 | return -EINVAL; |
832 | |
833 | if (newfd >= rlimit(RLIMIT_NOFILE)) |
834 | return -EBADF; |
835 | |
836 | spin_lock(&files->file_lock); |
837 | err = expand_files(files, newfd); |
838 | file = fcheck(oldfd); |
839 | if (unlikely(!file)) |
840 | goto Ebadf; |
841 | if (unlikely(err < 0)) { |
842 | if (err == -EMFILE) |
843 | goto Ebadf; |
844 | goto out_unlock; |
845 | } |
846 | return do_dup2(files, file, newfd, flags); |
847 | |
848 | Ebadf: |
849 | err = -EBADF; |
850 | out_unlock: |
851 | spin_unlock(&files->file_lock); |
852 | return err; |
853 | } |
854 | |
855 | SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) |
856 | { |
857 | if (unlikely(newfd == oldfd)) { /* corner case */ |
858 | struct files_struct *files = current->files; |
859 | int retval = oldfd; |
860 | |
861 | rcu_read_lock(); |
862 | if (!fcheck_files(files, oldfd)) |
863 | retval = -EBADF; |
864 | rcu_read_unlock(); |
865 | return retval; |
866 | } |
867 | return sys_dup3(oldfd, newfd, 0); |
868 | } |
869 | |
870 | SYSCALL_DEFINE1(dup, unsigned int, fildes) |
871 | { |
872 | int ret = -EBADF; |
873 | struct file *file = fget_raw(fildes); |
874 | |
875 | if (file) { |
876 | ret = get_unused_fd(); |
877 | if (ret >= 0) |
878 | fd_install(ret, file); |
879 | else |
880 | fput(file); |
881 | } |
882 | return ret; |
883 | } |
884 | |
885 | int f_dupfd(unsigned int from, struct file *file, unsigned flags) |
886 | { |
887 | int err; |
888 | if (from >= rlimit(RLIMIT_NOFILE)) |
889 | return -EINVAL; |
890 | err = alloc_fd(from, flags); |
891 | if (err >= 0) { |
892 | get_file(file); |
893 | fd_install(err, file); |
894 | } |
895 | return err; |
896 | } |
897 | |
898 | int iterate_fd(struct files_struct *files, unsigned n, |
899 | int (*f)(const void *, struct file *, unsigned), |
900 | const void *p) |
901 | { |
902 | struct fdtable *fdt; |
903 | int res = 0; |
904 | if (!files) |
905 | return 0; |
906 | spin_lock(&files->file_lock); |
907 | for (fdt = files_fdtable(files); n < fdt->max_fds; n++) { |
908 | struct file *file; |
909 | file = rcu_dereference_check_fdtable(files, fdt->fd[n]); |
910 | if (!file) |
911 | continue; |
912 | res = f(p, file, n); |
913 | if (res) |
914 | break; |
915 | } |
916 | spin_unlock(&files->file_lock); |
917 | return res; |
918 | } |
919 | EXPORT_SYMBOL(iterate_fd); |
920 |
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