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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 | struct fdtable_defer { |
27 | spinlock_t lock; |
28 | struct work_struct wq; |
29 | struct fdtable *next; |
30 | }; |
31 | |
32 | int sysctl_nr_open __read_mostly = 1024*1024; |
33 | int sysctl_nr_open_min = BITS_PER_LONG; |
34 | int sysctl_nr_open_max = 1024 * 1024; /* raised later */ |
35 | |
36 | /* |
37 | * We use this list to defer free fdtables that have vmalloced |
38 | * sets/arrays. By keeping a per-cpu list, we avoid having to embed |
39 | * the work_struct in fdtable itself which avoids a 64 byte (i386) increase in |
40 | * this per-task structure. |
41 | */ |
42 | static DEFINE_PER_CPU(struct fdtable_defer, fdtable_defer_list); |
43 | |
44 | static void *alloc_fdmem(size_t size) |
45 | { |
46 | /* |
47 | * Very large allocations can stress page reclaim, so fall back to |
48 | * vmalloc() if the allocation size will be considered "large" by the VM. |
49 | */ |
50 | if (size <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER)) { |
51 | void *data = kmalloc(size, GFP_KERNEL|__GFP_NOWARN); |
52 | if (data != NULL) |
53 | return data; |
54 | } |
55 | return vmalloc(size); |
56 | } |
57 | |
58 | static void free_fdmem(void *ptr) |
59 | { |
60 | is_vmalloc_addr(ptr) ? vfree(ptr) : kfree(ptr); |
61 | } |
62 | |
63 | static void __free_fdtable(struct fdtable *fdt) |
64 | { |
65 | free_fdmem(fdt->fd); |
66 | free_fdmem(fdt->open_fds); |
67 | kfree(fdt); |
68 | } |
69 | |
70 | static void free_fdtable_work(struct work_struct *work) |
71 | { |
72 | struct fdtable_defer *f = |
73 | container_of(work, struct fdtable_defer, wq); |
74 | struct fdtable *fdt; |
75 | |
76 | spin_lock_bh(&f->lock); |
77 | fdt = f->next; |
78 | f->next = NULL; |
79 | spin_unlock_bh(&f->lock); |
80 | while(fdt) { |
81 | struct fdtable *next = fdt->next; |
82 | |
83 | __free_fdtable(fdt); |
84 | fdt = next; |
85 | } |
86 | } |
87 | |
88 | static void free_fdtable_rcu(struct rcu_head *rcu) |
89 | { |
90 | struct fdtable *fdt = container_of(rcu, struct fdtable, rcu); |
91 | struct fdtable_defer *fddef; |
92 | |
93 | BUG_ON(!fdt); |
94 | BUG_ON(fdt->max_fds <= NR_OPEN_DEFAULT); |
95 | |
96 | if (!is_vmalloc_addr(fdt->fd) && !is_vmalloc_addr(fdt->open_fds)) { |
97 | kfree(fdt->fd); |
98 | kfree(fdt->open_fds); |
99 | kfree(fdt); |
100 | } else { |
101 | fddef = &get_cpu_var(fdtable_defer_list); |
102 | spin_lock(&fddef->lock); |
103 | fdt->next = fddef->next; |
104 | fddef->next = fdt; |
105 | /* vmallocs are handled from the workqueue context */ |
106 | schedule_work(&fddef->wq); |
107 | spin_unlock(&fddef->lock); |
108 | put_cpu_var(fdtable_defer_list); |
109 | } |
110 | } |
111 | |
112 | /* |
113 | * Expand the fdset in the files_struct. Called with the files spinlock |
114 | * held for write. |
115 | */ |
116 | static void copy_fdtable(struct fdtable *nfdt, struct fdtable *ofdt) |
117 | { |
118 | unsigned int cpy, set; |
119 | |
120 | BUG_ON(nfdt->max_fds < ofdt->max_fds); |
121 | |
122 | cpy = ofdt->max_fds * sizeof(struct file *); |
123 | set = (nfdt->max_fds - ofdt->max_fds) * sizeof(struct file *); |
124 | memcpy(nfdt->fd, ofdt->fd, cpy); |
125 | memset((char *)(nfdt->fd) + cpy, 0, set); |
126 | |
127 | cpy = ofdt->max_fds / BITS_PER_BYTE; |
128 | set = (nfdt->max_fds - ofdt->max_fds) / BITS_PER_BYTE; |
129 | memcpy(nfdt->open_fds, ofdt->open_fds, cpy); |
130 | memset((char *)(nfdt->open_fds) + cpy, 0, set); |
131 | memcpy(nfdt->close_on_exec, ofdt->close_on_exec, cpy); |
132 | memset((char *)(nfdt->close_on_exec) + cpy, 0, set); |
133 | } |
134 | |
135 | static struct fdtable * alloc_fdtable(unsigned int nr) |
136 | { |
137 | struct fdtable *fdt; |
138 | void *data; |
139 | |
140 | /* |
141 | * Figure out how many fds we actually want to support in this fdtable. |
142 | * Allocation steps are keyed to the size of the fdarray, since it |
143 | * grows far faster than any of the other dynamic data. We try to fit |
144 | * the fdarray into comfortable page-tuned chunks: starting at 1024B |
145 | * and growing in powers of two from there on. |
146 | */ |
147 | nr /= (1024 / sizeof(struct file *)); |
148 | nr = roundup_pow_of_two(nr + 1); |
149 | nr *= (1024 / sizeof(struct file *)); |
150 | /* |
151 | * Note that this can drive nr *below* what we had passed if sysctl_nr_open |
152 | * had been set lower between the check in expand_files() and here. Deal |
153 | * with that in caller, it's cheaper that way. |
154 | * |
155 | * We make sure that nr remains a multiple of BITS_PER_LONG - otherwise |
156 | * bitmaps handling below becomes unpleasant, to put it mildly... |
157 | */ |
158 | if (unlikely(nr > sysctl_nr_open)) |
159 | nr = ((sysctl_nr_open - 1) | (BITS_PER_LONG - 1)) + 1; |
160 | |
161 | fdt = kmalloc(sizeof(struct fdtable), GFP_KERNEL); |
162 | if (!fdt) |
163 | goto out; |
164 | fdt->max_fds = nr; |
165 | data = alloc_fdmem(nr * sizeof(struct file *)); |
166 | if (!data) |
167 | goto out_fdt; |
168 | fdt->fd = data; |
169 | |
170 | data = alloc_fdmem(max_t(size_t, |
171 | 2 * nr / BITS_PER_BYTE, L1_CACHE_BYTES)); |
172 | if (!data) |
173 | goto out_arr; |
174 | fdt->open_fds = data; |
175 | data += nr / BITS_PER_BYTE; |
176 | fdt->close_on_exec = data; |
177 | fdt->next = NULL; |
178 | |
179 | return fdt; |
180 | |
181 | out_arr: |
182 | free_fdmem(fdt->fd); |
183 | out_fdt: |
184 | kfree(fdt); |
185 | out: |
186 | return NULL; |
187 | } |
188 | |
189 | /* |
190 | * Expand the file descriptor table. |
191 | * This function will allocate a new fdtable and both fd array and fdset, of |
192 | * the given size. |
193 | * Return <0 error code on error; 1 on successful completion. |
194 | * The files->file_lock should be held on entry, and will be held on exit. |
195 | */ |
196 | static int expand_fdtable(struct files_struct *files, int nr) |
197 | __releases(files->file_lock) |
198 | __acquires(files->file_lock) |
199 | { |
200 | struct fdtable *new_fdt, *cur_fdt; |
201 | |
202 | spin_unlock(&files->file_lock); |
203 | new_fdt = alloc_fdtable(nr); |
204 | spin_lock(&files->file_lock); |
205 | if (!new_fdt) |
206 | return -ENOMEM; |
207 | /* |
208 | * extremely unlikely race - sysctl_nr_open decreased between the check in |
209 | * caller and alloc_fdtable(). Cheaper to catch it here... |
210 | */ |
211 | if (unlikely(new_fdt->max_fds <= nr)) { |
212 | __free_fdtable(new_fdt); |
213 | return -EMFILE; |
214 | } |
215 | /* |
216 | * Check again since another task may have expanded the fd table while |
217 | * we dropped the lock |
218 | */ |
219 | cur_fdt = files_fdtable(files); |
220 | if (nr >= cur_fdt->max_fds) { |
221 | /* Continue as planned */ |
222 | copy_fdtable(new_fdt, cur_fdt); |
223 | rcu_assign_pointer(files->fdt, new_fdt); |
224 | if (cur_fdt->max_fds > NR_OPEN_DEFAULT) |
225 | call_rcu(&cur_fdt->rcu, free_fdtable_rcu); |
226 | } else { |
227 | /* Somebody else expanded, so undo our attempt */ |
228 | __free_fdtable(new_fdt); |
229 | } |
230 | return 1; |
231 | } |
232 | |
233 | /* |
234 | * Expand files. |
235 | * This function will expand the file structures, if the requested size exceeds |
236 | * the current capacity and there is room for expansion. |
237 | * Return <0 error code on error; 0 when nothing done; 1 when files were |
238 | * expanded and execution may have blocked. |
239 | * The files->file_lock should be held on entry, and will be held on exit. |
240 | */ |
241 | static int expand_files(struct files_struct *files, int nr) |
242 | { |
243 | struct fdtable *fdt; |
244 | |
245 | fdt = files_fdtable(files); |
246 | |
247 | /* Do we need to expand? */ |
248 | if (nr < fdt->max_fds) |
249 | return 0; |
250 | |
251 | /* Can we expand? */ |
252 | if (nr >= sysctl_nr_open) |
253 | return -EMFILE; |
254 | |
255 | /* All good, so we try */ |
256 | return expand_fdtable(files, nr); |
257 | } |
258 | |
259 | static inline void __set_close_on_exec(int fd, struct fdtable *fdt) |
260 | { |
261 | __set_bit(fd, fdt->close_on_exec); |
262 | } |
263 | |
264 | static inline void __clear_close_on_exec(int fd, struct fdtable *fdt) |
265 | { |
266 | __clear_bit(fd, fdt->close_on_exec); |
267 | } |
268 | |
269 | static inline void __set_open_fd(int fd, struct fdtable *fdt) |
270 | { |
271 | __set_bit(fd, fdt->open_fds); |
272 | } |
273 | |
274 | static inline void __clear_open_fd(int fd, struct fdtable *fdt) |
275 | { |
276 | __clear_bit(fd, fdt->open_fds); |
277 | } |
278 | |
279 | static int count_open_files(struct fdtable *fdt) |
280 | { |
281 | int size = fdt->max_fds; |
282 | int i; |
283 | |
284 | /* Find the last open fd */ |
285 | for (i = size / BITS_PER_LONG; i > 0; ) { |
286 | if (fdt->open_fds[--i]) |
287 | break; |
288 | } |
289 | i = (i + 1) * BITS_PER_LONG; |
290 | return i; |
291 | } |
292 | |
293 | /* |
294 | * Allocate a new files structure and copy contents from the |
295 | * passed in files structure. |
296 | * errorp will be valid only when the returned files_struct is NULL. |
297 | */ |
298 | struct files_struct *dup_fd(struct files_struct *oldf, int *errorp) |
299 | { |
300 | struct files_struct *newf; |
301 | struct file **old_fds, **new_fds; |
302 | int open_files, size, i; |
303 | struct fdtable *old_fdt, *new_fdt; |
304 | |
305 | *errorp = -ENOMEM; |
306 | newf = kmem_cache_alloc(files_cachep, GFP_KERNEL); |
307 | if (!newf) |
308 | goto out; |
309 | |
310 | atomic_set(&newf->count, 1); |
311 | |
312 | spin_lock_init(&newf->file_lock); |
313 | newf->next_fd = 0; |
314 | new_fdt = &newf->fdtab; |
315 | new_fdt->max_fds = NR_OPEN_DEFAULT; |
316 | new_fdt->close_on_exec = newf->close_on_exec_init; |
317 | new_fdt->open_fds = newf->open_fds_init; |
318 | new_fdt->fd = &newf->fd_array[0]; |
319 | new_fdt->next = NULL; |
320 | |
321 | spin_lock(&oldf->file_lock); |
322 | old_fdt = files_fdtable(oldf); |
323 | open_files = count_open_files(old_fdt); |
324 | |
325 | /* |
326 | * Check whether we need to allocate a larger fd array and fd set. |
327 | */ |
328 | while (unlikely(open_files > new_fdt->max_fds)) { |
329 | spin_unlock(&oldf->file_lock); |
330 | |
331 | if (new_fdt != &newf->fdtab) |
332 | __free_fdtable(new_fdt); |
333 | |
334 | new_fdt = alloc_fdtable(open_files - 1); |
335 | if (!new_fdt) { |
336 | *errorp = -ENOMEM; |
337 | goto out_release; |
338 | } |
339 | |
340 | /* beyond sysctl_nr_open; nothing to do */ |
341 | if (unlikely(new_fdt->max_fds < open_files)) { |
342 | __free_fdtable(new_fdt); |
343 | *errorp = -EMFILE; |
344 | goto out_release; |
345 | } |
346 | |
347 | /* |
348 | * Reacquire the oldf lock and a pointer to its fd table |
349 | * who knows it may have a new bigger fd table. We need |
350 | * the latest pointer. |
351 | */ |
352 | spin_lock(&oldf->file_lock); |
353 | old_fdt = files_fdtable(oldf); |
354 | open_files = count_open_files(old_fdt); |
355 | } |
356 | |
357 | old_fds = old_fdt->fd; |
358 | new_fds = new_fdt->fd; |
359 | |
360 | memcpy(new_fdt->open_fds, old_fdt->open_fds, open_files / 8); |
361 | memcpy(new_fdt->close_on_exec, old_fdt->close_on_exec, open_files / 8); |
362 | |
363 | for (i = open_files; i != 0; i--) { |
364 | struct file *f = *old_fds++; |
365 | if (f) { |
366 | get_file(f); |
367 | } else { |
368 | /* |
369 | * The fd may be claimed in the fd bitmap but not yet |
370 | * instantiated in the files array if a sibling thread |
371 | * is partway through open(). So make sure that this |
372 | * fd is available to the new process. |
373 | */ |
374 | __clear_open_fd(open_files - i, new_fdt); |
375 | } |
376 | rcu_assign_pointer(*new_fds++, f); |
377 | } |
378 | spin_unlock(&oldf->file_lock); |
379 | |
380 | /* compute the remainder to be cleared */ |
381 | size = (new_fdt->max_fds - open_files) * sizeof(struct file *); |
382 | |
383 | /* This is long word aligned thus could use a optimized version */ |
384 | memset(new_fds, 0, size); |
385 | |
386 | if (new_fdt->max_fds > open_files) { |
387 | int left = (new_fdt->max_fds - open_files) / 8; |
388 | int start = open_files / BITS_PER_LONG; |
389 | |
390 | memset(&new_fdt->open_fds[start], 0, left); |
391 | memset(&new_fdt->close_on_exec[start], 0, left); |
392 | } |
393 | |
394 | rcu_assign_pointer(newf->fdt, new_fdt); |
395 | |
396 | return newf; |
397 | |
398 | out_release: |
399 | kmem_cache_free(files_cachep, newf); |
400 | out: |
401 | return NULL; |
402 | } |
403 | |
404 | static void close_files(struct files_struct * files) |
405 | { |
406 | int i, j; |
407 | struct fdtable *fdt; |
408 | |
409 | j = 0; |
410 | |
411 | /* |
412 | * It is safe to dereference the fd table without RCU or |
413 | * ->file_lock because this is the last reference to the |
414 | * files structure. But use RCU to shut RCU-lockdep up. |
415 | */ |
416 | rcu_read_lock(); |
417 | fdt = files_fdtable(files); |
418 | rcu_read_unlock(); |
419 | for (;;) { |
420 | unsigned long set; |
421 | i = j * BITS_PER_LONG; |
422 | if (i >= fdt->max_fds) |
423 | break; |
424 | set = fdt->open_fds[j++]; |
425 | while (set) { |
426 | if (set & 1) { |
427 | struct file * file = xchg(&fdt->fd[i], NULL); |
428 | if (file) { |
429 | filp_close(file, files); |
430 | cond_resched(); |
431 | } |
432 | } |
433 | i++; |
434 | set >>= 1; |
435 | } |
436 | } |
437 | } |
438 | |
439 | struct files_struct *get_files_struct(struct task_struct *task) |
440 | { |
441 | struct files_struct *files; |
442 | |
443 | task_lock(task); |
444 | files = task->files; |
445 | if (files) |
446 | atomic_inc(&files->count); |
447 | task_unlock(task); |
448 | |
449 | return files; |
450 | } |
451 | |
452 | void put_files_struct(struct files_struct *files) |
453 | { |
454 | struct fdtable *fdt; |
455 | |
456 | if (atomic_dec_and_test(&files->count)) { |
457 | close_files(files); |
458 | /* not really needed, since nobody can see us */ |
459 | rcu_read_lock(); |
460 | fdt = files_fdtable(files); |
461 | rcu_read_unlock(); |
462 | /* free the arrays if they are not embedded */ |
463 | if (fdt != &files->fdtab) |
464 | __free_fdtable(fdt); |
465 | kmem_cache_free(files_cachep, files); |
466 | } |
467 | } |
468 | |
469 | void reset_files_struct(struct files_struct *files) |
470 | { |
471 | struct task_struct *tsk = current; |
472 | struct files_struct *old; |
473 | |
474 | old = tsk->files; |
475 | task_lock(tsk); |
476 | tsk->files = files; |
477 | task_unlock(tsk); |
478 | put_files_struct(old); |
479 | } |
480 | |
481 | void exit_files(struct task_struct *tsk) |
482 | { |
483 | struct files_struct * files = tsk->files; |
484 | |
485 | if (files) { |
486 | task_lock(tsk); |
487 | tsk->files = NULL; |
488 | task_unlock(tsk); |
489 | put_files_struct(files); |
490 | } |
491 | } |
492 | |
493 | static void fdtable_defer_list_init(int cpu) |
494 | { |
495 | struct fdtable_defer *fddef = &per_cpu(fdtable_defer_list, cpu); |
496 | spin_lock_init(&fddef->lock); |
497 | INIT_WORK(&fddef->wq, free_fdtable_work); |
498 | fddef->next = NULL; |
499 | } |
500 | |
501 | void __init files_defer_init(void) |
502 | { |
503 | int i; |
504 | for_each_possible_cpu(i) |
505 | fdtable_defer_list_init(i); |
506 | sysctl_nr_open_max = min((size_t)INT_MAX, ~(size_t)0/sizeof(void *)) & |
507 | -BITS_PER_LONG; |
508 | } |
509 | |
510 | struct files_struct init_files = { |
511 | .count = ATOMIC_INIT(1), |
512 | .fdt = &init_files.fdtab, |
513 | .fdtab = { |
514 | .max_fds = NR_OPEN_DEFAULT, |
515 | .fd = &init_files.fd_array[0], |
516 | .close_on_exec = init_files.close_on_exec_init, |
517 | .open_fds = init_files.open_fds_init, |
518 | }, |
519 | .file_lock = __SPIN_LOCK_UNLOCKED(init_files.file_lock), |
520 | }; |
521 | |
522 | /* |
523 | * allocate a file descriptor, mark it busy. |
524 | */ |
525 | int __alloc_fd(struct files_struct *files, |
526 | unsigned start, unsigned end, unsigned flags) |
527 | { |
528 | unsigned int fd; |
529 | int error; |
530 | struct fdtable *fdt; |
531 | |
532 | spin_lock(&files->file_lock); |
533 | repeat: |
534 | fdt = files_fdtable(files); |
535 | fd = start; |
536 | if (fd < files->next_fd) |
537 | fd = files->next_fd; |
538 | |
539 | if (fd < fdt->max_fds) |
540 | fd = find_next_zero_bit(fdt->open_fds, fdt->max_fds, fd); |
541 | |
542 | /* |
543 | * N.B. For clone tasks sharing a files structure, this test |
544 | * will limit the total number of files that can be opened. |
545 | */ |
546 | error = -EMFILE; |
547 | if (fd >= end) |
548 | goto out; |
549 | |
550 | error = expand_files(files, fd); |
551 | if (error < 0) |
552 | goto out; |
553 | |
554 | /* |
555 | * If we needed to expand the fs array we |
556 | * might have blocked - try again. |
557 | */ |
558 | if (error) |
559 | goto repeat; |
560 | |
561 | if (start <= files->next_fd) |
562 | files->next_fd = fd + 1; |
563 | |
564 | __set_open_fd(fd, fdt); |
565 | if (flags & O_CLOEXEC) |
566 | __set_close_on_exec(fd, fdt); |
567 | else |
568 | __clear_close_on_exec(fd, fdt); |
569 | error = fd; |
570 | #if 1 |
571 | /* Sanity check */ |
572 | if (rcu_dereference_raw(fdt->fd[fd]) != NULL) { |
573 | printk(KERN_WARNING "alloc_fd: slot %d not NULL!\n", fd); |
574 | rcu_assign_pointer(fdt->fd[fd], NULL); |
575 | } |
576 | #endif |
577 | |
578 | out: |
579 | spin_unlock(&files->file_lock); |
580 | return error; |
581 | } |
582 | |
583 | static int alloc_fd(unsigned start, unsigned flags) |
584 | { |
585 | return __alloc_fd(current->files, start, rlimit(RLIMIT_NOFILE), flags); |
586 | } |
587 | |
588 | int get_unused_fd_flags(unsigned flags) |
589 | { |
590 | return __alloc_fd(current->files, 0, rlimit(RLIMIT_NOFILE), flags); |
591 | } |
592 | EXPORT_SYMBOL(get_unused_fd_flags); |
593 | |
594 | static void __put_unused_fd(struct files_struct *files, unsigned int fd) |
595 | { |
596 | struct fdtable *fdt = files_fdtable(files); |
597 | __clear_open_fd(fd, fdt); |
598 | if (fd < files->next_fd) |
599 | files->next_fd = fd; |
600 | } |
601 | |
602 | void put_unused_fd(unsigned int fd) |
603 | { |
604 | struct files_struct *files = current->files; |
605 | spin_lock(&files->file_lock); |
606 | __put_unused_fd(files, fd); |
607 | spin_unlock(&files->file_lock); |
608 | } |
609 | |
610 | EXPORT_SYMBOL(put_unused_fd); |
611 | |
612 | /* |
613 | * Install a file pointer in the fd array. |
614 | * |
615 | * The VFS is full of places where we drop the files lock between |
616 | * setting the open_fds bitmap and installing the file in the file |
617 | * array. At any such point, we are vulnerable to a dup2() race |
618 | * installing a file in the array before us. We need to detect this and |
619 | * fput() the struct file we are about to overwrite in this case. |
620 | * |
621 | * It should never happen - if we allow dup2() do it, _really_ bad things |
622 | * will follow. |
623 | * |
624 | * NOTE: __fd_install() variant is really, really low-level; don't |
625 | * use it unless you are forced to by truly lousy API shoved down |
626 | * your throat. 'files' *MUST* be either current->files or obtained |
627 | * by get_files_struct(current) done by whoever had given it to you, |
628 | * or really bad things will happen. Normally you want to use |
629 | * fd_install() instead. |
630 | */ |
631 | |
632 | void __fd_install(struct files_struct *files, unsigned int fd, |
633 | struct file *file) |
634 | { |
635 | struct fdtable *fdt; |
636 | spin_lock(&files->file_lock); |
637 | fdt = files_fdtable(files); |
638 | BUG_ON(fdt->fd[fd] != NULL); |
639 | rcu_assign_pointer(fdt->fd[fd], file); |
640 | spin_unlock(&files->file_lock); |
641 | } |
642 | |
643 | void fd_install(unsigned int fd, struct file *file) |
644 | { |
645 | __fd_install(current->files, fd, file); |
646 | } |
647 | |
648 | EXPORT_SYMBOL(fd_install); |
649 | |
650 | /* |
651 | * The same warnings as for __alloc_fd()/__fd_install() apply here... |
652 | */ |
653 | int __close_fd(struct files_struct *files, unsigned fd) |
654 | { |
655 | struct file *file; |
656 | struct fdtable *fdt; |
657 | |
658 | spin_lock(&files->file_lock); |
659 | fdt = files_fdtable(files); |
660 | if (fd >= fdt->max_fds) |
661 | goto out_unlock; |
662 | file = fdt->fd[fd]; |
663 | if (!file) |
664 | goto out_unlock; |
665 | rcu_assign_pointer(fdt->fd[fd], NULL); |
666 | __clear_close_on_exec(fd, fdt); |
667 | __put_unused_fd(files, fd); |
668 | spin_unlock(&files->file_lock); |
669 | return filp_close(file, files); |
670 | |
671 | out_unlock: |
672 | spin_unlock(&files->file_lock); |
673 | return -EBADF; |
674 | } |
675 | |
676 | void do_close_on_exec(struct files_struct *files) |
677 | { |
678 | unsigned i; |
679 | struct fdtable *fdt; |
680 | |
681 | /* exec unshares first */ |
682 | spin_lock(&files->file_lock); |
683 | for (i = 0; ; i++) { |
684 | unsigned long set; |
685 | unsigned fd = i * BITS_PER_LONG; |
686 | fdt = files_fdtable(files); |
687 | if (fd >= fdt->max_fds) |
688 | break; |
689 | set = fdt->close_on_exec[i]; |
690 | if (!set) |
691 | continue; |
692 | fdt->close_on_exec[i] = 0; |
693 | for ( ; set ; fd++, set >>= 1) { |
694 | struct file *file; |
695 | if (!(set & 1)) |
696 | continue; |
697 | file = fdt->fd[fd]; |
698 | if (!file) |
699 | continue; |
700 | rcu_assign_pointer(fdt->fd[fd], NULL); |
701 | __put_unused_fd(files, fd); |
702 | spin_unlock(&files->file_lock); |
703 | filp_close(file, files); |
704 | cond_resched(); |
705 | spin_lock(&files->file_lock); |
706 | } |
707 | |
708 | } |
709 | spin_unlock(&files->file_lock); |
710 | } |
711 | |
712 | struct file *fget(unsigned int fd) |
713 | { |
714 | struct file *file; |
715 | struct files_struct *files = current->files; |
716 | |
717 | rcu_read_lock(); |
718 | file = fcheck_files(files, fd); |
719 | if (file) { |
720 | /* File object ref couldn't be taken */ |
721 | if (file->f_mode & FMODE_PATH || |
722 | !atomic_long_inc_not_zero(&file->f_count)) |
723 | file = NULL; |
724 | } |
725 | rcu_read_unlock(); |
726 | |
727 | return file; |
728 | } |
729 | |
730 | EXPORT_SYMBOL(fget); |
731 | |
732 | struct file *fget_raw(unsigned int fd) |
733 | { |
734 | struct file *file; |
735 | struct files_struct *files = current->files; |
736 | |
737 | rcu_read_lock(); |
738 | file = fcheck_files(files, fd); |
739 | if (file) { |
740 | /* File object ref couldn't be taken */ |
741 | if (!atomic_long_inc_not_zero(&file->f_count)) |
742 | file = NULL; |
743 | } |
744 | rcu_read_unlock(); |
745 | |
746 | return file; |
747 | } |
748 | |
749 | EXPORT_SYMBOL(fget_raw); |
750 | |
751 | /* |
752 | * Lightweight file lookup - no refcnt increment if fd table isn't shared. |
753 | * |
754 | * You can use this instead of fget if you satisfy all of the following |
755 | * conditions: |
756 | * 1) You must call fput_light before exiting the syscall and returning control |
757 | * to userspace (i.e. you cannot remember the returned struct file * after |
758 | * returning to userspace). |
759 | * 2) You must not call filp_close on the returned struct file * in between |
760 | * calls to fget_light and fput_light. |
761 | * 3) You must not clone the current task in between the calls to fget_light |
762 | * and fput_light. |
763 | * |
764 | * The fput_needed flag returned by fget_light should be passed to the |
765 | * corresponding fput_light. |
766 | */ |
767 | struct file *fget_light(unsigned int fd, int *fput_needed) |
768 | { |
769 | struct file *file; |
770 | struct files_struct *files = current->files; |
771 | |
772 | *fput_needed = 0; |
773 | if (atomic_read(&files->count) == 1) { |
774 | file = fcheck_files(files, fd); |
775 | if (file && (file->f_mode & FMODE_PATH)) |
776 | file = NULL; |
777 | } else { |
778 | rcu_read_lock(); |
779 | file = fcheck_files(files, fd); |
780 | if (file) { |
781 | if (!(file->f_mode & FMODE_PATH) && |
782 | atomic_long_inc_not_zero(&file->f_count)) |
783 | *fput_needed = 1; |
784 | else |
785 | /* Didn't get the reference, someone's freed */ |
786 | file = NULL; |
787 | } |
788 | rcu_read_unlock(); |
789 | } |
790 | |
791 | return file; |
792 | } |
793 | EXPORT_SYMBOL(fget_light); |
794 | |
795 | struct file *fget_raw_light(unsigned int fd, int *fput_needed) |
796 | { |
797 | struct file *file; |
798 | struct files_struct *files = current->files; |
799 | |
800 | *fput_needed = 0; |
801 | if (atomic_read(&files->count) == 1) { |
802 | file = fcheck_files(files, fd); |
803 | } else { |
804 | rcu_read_lock(); |
805 | file = fcheck_files(files, fd); |
806 | if (file) { |
807 | if (atomic_long_inc_not_zero(&file->f_count)) |
808 | *fput_needed = 1; |
809 | else |
810 | /* Didn't get the reference, someone's freed */ |
811 | file = NULL; |
812 | } |
813 | rcu_read_unlock(); |
814 | } |
815 | |
816 | return file; |
817 | } |
818 | |
819 | void set_close_on_exec(unsigned int fd, int flag) |
820 | { |
821 | struct files_struct *files = current->files; |
822 | struct fdtable *fdt; |
823 | spin_lock(&files->file_lock); |
824 | fdt = files_fdtable(files); |
825 | if (flag) |
826 | __set_close_on_exec(fd, fdt); |
827 | else |
828 | __clear_close_on_exec(fd, fdt); |
829 | spin_unlock(&files->file_lock); |
830 | } |
831 | |
832 | bool get_close_on_exec(unsigned int fd) |
833 | { |
834 | struct files_struct *files = current->files; |
835 | struct fdtable *fdt; |
836 | bool res; |
837 | rcu_read_lock(); |
838 | fdt = files_fdtable(files); |
839 | res = close_on_exec(fd, fdt); |
840 | rcu_read_unlock(); |
841 | return res; |
842 | } |
843 | |
844 | static int do_dup2(struct files_struct *files, |
845 | struct file *file, unsigned fd, unsigned flags) |
846 | { |
847 | struct file *tofree; |
848 | struct fdtable *fdt; |
849 | |
850 | /* |
851 | * We need to detect attempts to do dup2() over allocated but still |
852 | * not finished descriptor. NB: OpenBSD avoids that at the price of |
853 | * extra work in their equivalent of fget() - they insert struct |
854 | * file immediately after grabbing descriptor, mark it larval if |
855 | * more work (e.g. actual opening) is needed and make sure that |
856 | * fget() treats larval files as absent. Potentially interesting, |
857 | * but while extra work in fget() is trivial, locking implications |
858 | * and amount of surgery on open()-related paths in VFS are not. |
859 | * FreeBSD fails with -EBADF in the same situation, NetBSD "solution" |
860 | * deadlocks in rather amusing ways, AFAICS. All of that is out of |
861 | * scope of POSIX or SUS, since neither considers shared descriptor |
862 | * tables and this condition does not arise without those. |
863 | */ |
864 | fdt = files_fdtable(files); |
865 | tofree = fdt->fd[fd]; |
866 | if (!tofree && fd_is_open(fd, fdt)) |
867 | goto Ebusy; |
868 | get_file(file); |
869 | rcu_assign_pointer(fdt->fd[fd], file); |
870 | __set_open_fd(fd, fdt); |
871 | if (flags & O_CLOEXEC) |
872 | __set_close_on_exec(fd, fdt); |
873 | else |
874 | __clear_close_on_exec(fd, fdt); |
875 | spin_unlock(&files->file_lock); |
876 | |
877 | if (tofree) |
878 | filp_close(tofree, files); |
879 | |
880 | return fd; |
881 | |
882 | Ebusy: |
883 | spin_unlock(&files->file_lock); |
884 | return -EBUSY; |
885 | } |
886 | |
887 | int replace_fd(unsigned fd, struct file *file, unsigned flags) |
888 | { |
889 | int err; |
890 | struct files_struct *files = current->files; |
891 | |
892 | if (!file) |
893 | return __close_fd(files, fd); |
894 | |
895 | if (fd >= rlimit(RLIMIT_NOFILE)) |
896 | return -EBADF; |
897 | |
898 | spin_lock(&files->file_lock); |
899 | err = expand_files(files, fd); |
900 | if (unlikely(err < 0)) |
901 | goto out_unlock; |
902 | return do_dup2(files, file, fd, flags); |
903 | |
904 | out_unlock: |
905 | spin_unlock(&files->file_lock); |
906 | return err; |
907 | } |
908 | |
909 | SYSCALL_DEFINE3(dup3, unsigned int, oldfd, unsigned int, newfd, int, flags) |
910 | { |
911 | int err = -EBADF; |
912 | struct file *file; |
913 | struct files_struct *files = current->files; |
914 | |
915 | if ((flags & ~O_CLOEXEC) != 0) |
916 | return -EINVAL; |
917 | |
918 | if (unlikely(oldfd == newfd)) |
919 | return -EINVAL; |
920 | |
921 | if (newfd >= rlimit(RLIMIT_NOFILE)) |
922 | return -EBADF; |
923 | |
924 | spin_lock(&files->file_lock); |
925 | err = expand_files(files, newfd); |
926 | file = fcheck(oldfd); |
927 | if (unlikely(!file)) |
928 | goto Ebadf; |
929 | if (unlikely(err < 0)) { |
930 | if (err == -EMFILE) |
931 | goto Ebadf; |
932 | goto out_unlock; |
933 | } |
934 | return do_dup2(files, file, newfd, flags); |
935 | |
936 | Ebadf: |
937 | err = -EBADF; |
938 | out_unlock: |
939 | spin_unlock(&files->file_lock); |
940 | return err; |
941 | } |
942 | |
943 | SYSCALL_DEFINE2(dup2, unsigned int, oldfd, unsigned int, newfd) |
944 | { |
945 | if (unlikely(newfd == oldfd)) { /* corner case */ |
946 | struct files_struct *files = current->files; |
947 | int retval = oldfd; |
948 | |
949 | rcu_read_lock(); |
950 | if (!fcheck_files(files, oldfd)) |
951 | retval = -EBADF; |
952 | rcu_read_unlock(); |
953 | return retval; |
954 | } |
955 | return sys_dup3(oldfd, newfd, 0); |
956 | } |
957 | |
958 | SYSCALL_DEFINE1(dup, unsigned int, fildes) |
959 | { |
960 | int ret = -EBADF; |
961 | struct file *file = fget_raw(fildes); |
962 | |
963 | if (file) { |
964 | ret = get_unused_fd(); |
965 | if (ret >= 0) |
966 | fd_install(ret, file); |
967 | else |
968 | fput(file); |
969 | } |
970 | return ret; |
971 | } |
972 | |
973 | int f_dupfd(unsigned int from, struct file *file, unsigned flags) |
974 | { |
975 | int err; |
976 | if (from >= rlimit(RLIMIT_NOFILE)) |
977 | return -EINVAL; |
978 | err = alloc_fd(from, flags); |
979 | if (err >= 0) { |
980 | get_file(file); |
981 | fd_install(err, file); |
982 | } |
983 | return err; |
984 | } |
985 | |
986 | int iterate_fd(struct files_struct *files, unsigned n, |
987 | int (*f)(const void *, struct file *, unsigned), |
988 | const void *p) |
989 | { |
990 | struct fdtable *fdt; |
991 | int res = 0; |
992 | if (!files) |
993 | return 0; |
994 | spin_lock(&files->file_lock); |
995 | for (fdt = files_fdtable(files); n < fdt->max_fds; n++) { |
996 | struct file *file; |
997 | file = rcu_dereference_check_fdtable(files, fdt->fd[n]); |
998 | if (!file) |
999 | continue; |
1000 | res = f(p, file, n); |
1001 | if (res) |
1002 | break; |
1003 | } |
1004 | spin_unlock(&files->file_lock); |
1005 | return res; |
1006 | } |
1007 | EXPORT_SYMBOL(iterate_fd); |
1008 |
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v2.6.34-rc5
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