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1 : : /*
2 : : * fs/eventpoll.c (Efficient event retrieval implementation)
3 : : * Copyright (C) 2001,...,2009 Davide Libenzi
4 : : *
5 : : * This program is free software; you can redistribute it and/or modify
6 : : * it under the terms of the GNU General Public License as published by
7 : : * the Free Software Foundation; either version 2 of the License, or
8 : : * (at your option) any later version.
9 : : *
10 : : * Davide Libenzi <davidel@xmailserver.org>
11 : : *
12 : : */
13 : :
14 : : #include <linux/init.h>
15 : : #include <linux/kernel.h>
16 : : #include <linux/sched.h>
17 : : #include <linux/fs.h>
18 : : #include <linux/file.h>
19 : : #include <linux/signal.h>
20 : : #include <linux/errno.h>
21 : : #include <linux/mm.h>
22 : : #include <linux/slab.h>
23 : : #include <linux/poll.h>
24 : : #include <linux/string.h>
25 : : #include <linux/list.h>
26 : : #include <linux/hash.h>
27 : : #include <linux/spinlock.h>
28 : : #include <linux/syscalls.h>
29 : : #include <linux/rbtree.h>
30 : : #include <linux/wait.h>
31 : : #include <linux/eventpoll.h>
32 : : #include <linux/mount.h>
33 : : #include <linux/bitops.h>
34 : : #include <linux/mutex.h>
35 : : #include <linux/anon_inodes.h>
36 : : #include <linux/device.h>
37 : : #include <asm/uaccess.h>
38 : : #include <asm/io.h>
39 : : #include <asm/mman.h>
40 : : #include <linux/atomic.h>
41 : : #include <linux/proc_fs.h>
42 : : #include <linux/seq_file.h>
43 : : #include <linux/compat.h>
44 : : #include <linux/rculist.h>
45 : :
46 : : /*
47 : : * LOCKING:
48 : : * There are three level of locking required by epoll :
49 : : *
50 : : * 1) epmutex (mutex)
51 : : * 2) ep->mtx (mutex)
52 : : * 3) ep->lock (spinlock)
53 : : *
54 : : * The acquire order is the one listed above, from 1 to 3.
55 : : * We need a spinlock (ep->lock) because we manipulate objects
56 : : * from inside the poll callback, that might be triggered from
57 : : * a wake_up() that in turn might be called from IRQ context.
58 : : * So we can't sleep inside the poll callback and hence we need
59 : : * a spinlock. During the event transfer loop (from kernel to
60 : : * user space) we could end up sleeping due a copy_to_user(), so
61 : : * we need a lock that will allow us to sleep. This lock is a
62 : : * mutex (ep->mtx). It is acquired during the event transfer loop,
63 : : * during epoll_ctl(EPOLL_CTL_DEL) and during eventpoll_release_file().
64 : : * Then we also need a global mutex to serialize eventpoll_release_file()
65 : : * and ep_free().
66 : : * This mutex is acquired by ep_free() during the epoll file
67 : : * cleanup path and it is also acquired by eventpoll_release_file()
68 : : * if a file has been pushed inside an epoll set and it is then
69 : : * close()d without a previous call to epoll_ctl(EPOLL_CTL_DEL).
70 : : * It is also acquired when inserting an epoll fd onto another epoll
71 : : * fd. We do this so that we walk the epoll tree and ensure that this
72 : : * insertion does not create a cycle of epoll file descriptors, which
73 : : * could lead to deadlock. We need a global mutex to prevent two
74 : : * simultaneous inserts (A into B and B into A) from racing and
75 : : * constructing a cycle without either insert observing that it is
76 : : * going to.
77 : : * It is necessary to acquire multiple "ep->mtx"es at once in the
78 : : * case when one epoll fd is added to another. In this case, we
79 : : * always acquire the locks in the order of nesting (i.e. after
80 : : * epoll_ctl(e1, EPOLL_CTL_ADD, e2), e1->mtx will always be acquired
81 : : * before e2->mtx). Since we disallow cycles of epoll file
82 : : * descriptors, this ensures that the mutexes are well-ordered. In
83 : : * order to communicate this nesting to lockdep, when walking a tree
84 : : * of epoll file descriptors, we use the current recursion depth as
85 : : * the lockdep subkey.
86 : : * It is possible to drop the "ep->mtx" and to use the global
87 : : * mutex "epmutex" (together with "ep->lock") to have it working,
88 : : * but having "ep->mtx" will make the interface more scalable.
89 : : * Events that require holding "epmutex" are very rare, while for
90 : : * normal operations the epoll private "ep->mtx" will guarantee
91 : : * a better scalability.
92 : : */
93 : :
94 : : /* Epoll private bits inside the event mask */
95 : : #define EP_PRIVATE_BITS (EPOLLWAKEUP | EPOLLONESHOT | EPOLLET)
96 : :
97 : : /* Maximum number of nesting allowed inside epoll sets */
98 : : #define EP_MAX_NESTS 4
99 : :
100 : : #define EP_MAX_EVENTS (INT_MAX / sizeof(struct epoll_event))
101 : :
102 : : #define EP_UNACTIVE_PTR ((void *) -1L)
103 : :
104 : : #define EP_ITEM_COST (sizeof(struct epitem) + sizeof(struct eppoll_entry))
105 : :
106 : : struct epoll_filefd {
107 : : struct file *file;
108 : : int fd;
109 : : } __packed;
110 : :
111 : : /*
112 : : * Structure used to track possible nested calls, for too deep recursions
113 : : * and loop cycles.
114 : : */
115 : : struct nested_call_node {
116 : : struct list_head llink;
117 : : void *cookie;
118 : : void *ctx;
119 : : };
120 : :
121 : : /*
122 : : * This structure is used as collector for nested calls, to check for
123 : : * maximum recursion dept and loop cycles.
124 : : */
125 : : struct nested_calls {
126 : : struct list_head tasks_call_list;
127 : : spinlock_t lock;
128 : : };
129 : :
130 : : /*
131 : : * Each file descriptor added to the eventpoll interface will
132 : : * have an entry of this type linked to the "rbr" RB tree.
133 : : * Avoid increasing the size of this struct, there can be many thousands
134 : : * of these on a server and we do not want this to take another cache line.
135 : : */
136 : : struct epitem {
137 : : union {
138 : : /* RB tree node links this structure to the eventpoll RB tree */
139 : : struct rb_node rbn;
140 : : /* Used to free the struct epitem */
141 : : struct rcu_head rcu;
142 : : };
143 : :
144 : : /* List header used to link this structure to the eventpoll ready list */
145 : : struct list_head rdllink;
146 : :
147 : : /*
148 : : * Works together "struct eventpoll"->ovflist in keeping the
149 : : * single linked chain of items.
150 : : */
151 : : struct epitem *next;
152 : :
153 : : /* The file descriptor information this item refers to */
154 : : struct epoll_filefd ffd;
155 : :
156 : : /* Number of active wait queue attached to poll operations */
157 : : int nwait;
158 : :
159 : : /* List containing poll wait queues */
160 : : struct list_head pwqlist;
161 : :
162 : : /* The "container" of this item */
163 : : struct eventpoll *ep;
164 : :
165 : : /* List header used to link this item to the "struct file" items list */
166 : : struct list_head fllink;
167 : :
168 : : /* wakeup_source used when EPOLLWAKEUP is set */
169 : : struct wakeup_source __rcu *ws;
170 : :
171 : : /* The structure that describe the interested events and the source fd */
172 : : struct epoll_event event;
173 : : };
174 : :
175 : : /*
176 : : * This structure is stored inside the "private_data" member of the file
177 : : * structure and represents the main data structure for the eventpoll
178 : : * interface.
179 : : */
180 : : struct eventpoll {
181 : : /* Protect the access to this structure */
182 : : spinlock_t lock;
183 : :
184 : : /*
185 : : * This mutex is used to ensure that files are not removed
186 : : * while epoll is using them. This is held during the event
187 : : * collection loop, the file cleanup path, the epoll file exit
188 : : * code and the ctl operations.
189 : : */
190 : : struct mutex mtx;
191 : :
192 : : /* Wait queue used by sys_epoll_wait() */
193 : : wait_queue_head_t wq;
194 : :
195 : : /* Wait queue used by file->poll() */
196 : : wait_queue_head_t poll_wait;
197 : :
198 : : /* List of ready file descriptors */
199 : : struct list_head rdllist;
200 : :
201 : : /* RB tree root used to store monitored fd structs */
202 : : struct rb_root rbr;
203 : :
204 : : /*
205 : : * This is a single linked list that chains all the "struct epitem" that
206 : : * happened while transferring ready events to userspace w/out
207 : : * holding ->lock.
208 : : */
209 : : struct epitem *ovflist;
210 : :
211 : : /* wakeup_source used when ep_scan_ready_list is running */
212 : : struct wakeup_source *ws;
213 : :
214 : : /* The user that created the eventpoll descriptor */
215 : : struct user_struct *user;
216 : :
217 : : struct file *file;
218 : :
219 : : /* used to optimize loop detection check */
220 : : int visited;
221 : : struct list_head visited_list_link;
222 : : };
223 : :
224 : : /* Wait structure used by the poll hooks */
225 : : struct eppoll_entry {
226 : : /* List header used to link this structure to the "struct epitem" */
227 : : struct list_head llink;
228 : :
229 : : /* The "base" pointer is set to the container "struct epitem" */
230 : : struct epitem *base;
231 : :
232 : : /*
233 : : * Wait queue item that will be linked to the target file wait
234 : : * queue head.
235 : : */
236 : : wait_queue_t wait;
237 : :
238 : : /* The wait queue head that linked the "wait" wait queue item */
239 : : wait_queue_head_t *whead;
240 : : };
241 : :
242 : : /* Wrapper struct used by poll queueing */
243 : : struct ep_pqueue {
244 : : poll_table pt;
245 : : struct epitem *epi;
246 : : };
247 : :
248 : : /* Used by the ep_send_events() function as callback private data */
249 : : struct ep_send_events_data {
250 : : int maxevents;
251 : : struct epoll_event __user *events;
252 : : };
253 : :
254 : : /*
255 : : * Configuration options available inside /proc/sys/fs/epoll/
256 : : */
257 : : /* Maximum number of epoll watched descriptors, per user */
258 : : static long max_user_watches __read_mostly;
259 : :
260 : : /*
261 : : * This mutex is used to serialize ep_free() and eventpoll_release_file().
262 : : */
263 : : static DEFINE_MUTEX(epmutex);
264 : :
265 : : /* Used to check for epoll file descriptor inclusion loops */
266 : : static struct nested_calls poll_loop_ncalls;
267 : :
268 : : /* Used for safe wake up implementation */
269 : : static struct nested_calls poll_safewake_ncalls;
270 : :
271 : : /* Used to call file's f_op->poll() under the nested calls boundaries */
272 : : static struct nested_calls poll_readywalk_ncalls;
273 : :
274 : : /* Slab cache used to allocate "struct epitem" */
275 : : static struct kmem_cache *epi_cache __read_mostly;
276 : :
277 : : /* Slab cache used to allocate "struct eppoll_entry" */
278 : : static struct kmem_cache *pwq_cache __read_mostly;
279 : :
280 : : /* Visited nodes during ep_loop_check(), so we can unset them when we finish */
281 : : static LIST_HEAD(visited_list);
282 : :
283 : : /*
284 : : * List of files with newly added links, where we may need to limit the number
285 : : * of emanating paths. Protected by the epmutex.
286 : : */
287 : : static LIST_HEAD(tfile_check_list);
288 : :
289 : : #ifdef CONFIG_SYSCTL
290 : :
291 : : #include <linux/sysctl.h>
292 : :
293 : : static long zero;
294 : : static long long_max = LONG_MAX;
295 : :
296 : : ctl_table epoll_table[] = {
297 : : {
298 : : .procname = "max_user_watches",
299 : : .data = &max_user_watches,
300 : : .maxlen = sizeof(max_user_watches),
301 : : .mode = 0644,
302 : : .proc_handler = proc_doulongvec_minmax,
303 : : .extra1 = &zero,
304 : : .extra2 = &long_max,
305 : : },
306 : : { }
307 : : };
308 : : #endif /* CONFIG_SYSCTL */
309 : :
310 : : static const struct file_operations eventpoll_fops;
311 : :
312 : : static inline int is_file_epoll(struct file *f)
313 : : {
314 : 0 : return f->f_op == &eventpoll_fops;
315 : : }
316 : :
317 : : /* Setup the structure that is used as key for the RB tree */
318 : : static inline void ep_set_ffd(struct epoll_filefd *ffd,
319 : : struct file *file, int fd)
320 : : {
321 : 0 : ffd->file = file;
322 : 0 : ffd->fd = fd;
323 : : }
324 : :
325 : : /* Compare RB tree keys */
326 : : static inline int ep_cmp_ffd(struct epoll_filefd *p1,
327 : : struct epoll_filefd *p2)
328 : : {
329 [ # # ][ # # ]: 0 : return (p1->file > p2->file ? +1:
330 [ # # ][ # # ]: 0 : (p1->file < p2->file ? -1 : p1->fd - p2->fd));
331 : : }
332 : :
333 : : /* Tells us if the item is currently linked */
334 : : static inline int ep_is_linked(struct list_head *p)
335 : : {
336 : : return !list_empty(p);
337 : : }
338 : :
339 : : static inline struct eppoll_entry *ep_pwq_from_wait(wait_queue_t *p)
340 : : {
341 : : return container_of(p, struct eppoll_entry, wait);
342 : : }
343 : :
344 : : /* Get the "struct epitem" from a wait queue pointer */
345 : : static inline struct epitem *ep_item_from_wait(wait_queue_t *p)
346 : : {
347 : 336 : return container_of(p, struct eppoll_entry, wait)->base;
348 : : }
349 : :
350 : : /* Get the "struct epitem" from an epoll queue wrapper */
351 : : static inline struct epitem *ep_item_from_epqueue(poll_table *p)
352 : : {
353 : 0 : return container_of(p, struct ep_pqueue, pt)->epi;
354 : : }
355 : :
356 : : /* Tells if the epoll_ctl(2) operation needs an event copy from userspace */
357 : : static inline int ep_op_has_event(int op)
358 : : {
359 : : return op != EPOLL_CTL_DEL;
360 : : }
361 : :
362 : : /* Initialize the poll safe wake up structure */
363 : : static void ep_nested_calls_init(struct nested_calls *ncalls)
364 : : {
365 : : INIT_LIST_HEAD(&ncalls->tasks_call_list);
366 : 0 : spin_lock_init(&ncalls->lock);
367 : : }
368 : :
369 : : /**
370 : : * ep_events_available - Checks if ready events might be available.
371 : : *
372 : : * @ep: Pointer to the eventpoll context.
373 : : *
374 : : * Returns: Returns a value different than zero if ready events are available,
375 : : * or zero otherwise.
376 : : */
377 : : static inline int ep_events_available(struct eventpoll *ep)
378 : : {
379 [ + + ][ + - ]: 1674 : return !list_empty(&ep->rdllist) || ep->ovflist != EP_UNACTIVE_PTR;
[ + + ][ + - ]
[ - + ][ # # ]
380 : : }
381 : :
382 : : /**
383 : : * ep_call_nested - Perform a bound (possibly) nested call, by checking
384 : : * that the recursion limit is not exceeded, and that
385 : : * the same nested call (by the meaning of same cookie) is
386 : : * no re-entered.
387 : : *
388 : : * @ncalls: Pointer to the nested_calls structure to be used for this call.
389 : : * @max_nests: Maximum number of allowed nesting calls.
390 : : * @nproc: Nested call core function pointer.
391 : : * @priv: Opaque data to be passed to the @nproc callback.
392 : : * @cookie: Cookie to be used to identify this nested call.
393 : : * @ctx: This instance context.
394 : : *
395 : : * Returns: Returns the code returned by the @nproc callback, or -1 if
396 : : * the maximum recursion limit has been exceeded.
397 : : */
398 : 0 : static int ep_call_nested(struct nested_calls *ncalls, int max_nests,
399 : : int (*nproc)(void *, void *, int), void *priv,
400 : : void *cookie, void *ctx)
401 : : {
402 : : int error, call_nests = 0;
403 : : unsigned long flags;
404 : 1320 : struct list_head *lsthead = &ncalls->tasks_call_list;
405 : : struct nested_call_node *tncur;
406 : : struct nested_call_node tnode;
407 : :
408 : 1320 : spin_lock_irqsave(&ncalls->lock, flags);
409 : :
410 : : /*
411 : : * Try to see if the current task is already inside this wakeup call.
412 : : * We use a list here, since the population inside this set is always
413 : : * very much limited.
414 : : */
415 [ - + ]: 2640 : list_for_each_entry(tncur, lsthead, llink) {
416 [ # # ][ # # ]: 0 : if (tncur->ctx == ctx &&
417 [ # # ]: 0 : (tncur->cookie == cookie || ++call_nests > max_nests)) {
418 : : /*
419 : : * Ops ... loop detected or maximum nest level reached.
420 : : * We abort this wake by breaking the cycle itself.
421 : : */
422 : : error = -1;
423 : : goto out_unlock;
424 : : }
425 : : }
426 : :
427 : : /* Add the current task and cookie to the list */
428 : 1320 : tnode.ctx = ctx;
429 : 1320 : tnode.cookie = cookie;
430 : : list_add(&tnode.llink, lsthead);
431 : :
432 : : spin_unlock_irqrestore(&ncalls->lock, flags);
433 : :
434 : : /* Call the nested function */
435 : 1320 : error = (*nproc)(priv, cookie, call_nests);
436 : :
437 : : /* Remove the current task from the list */
438 : 1320 : spin_lock_irqsave(&ncalls->lock, flags);
439 : : list_del(&tnode.llink);
440 : : out_unlock:
441 : : spin_unlock_irqrestore(&ncalls->lock, flags);
442 : :
443 : 1320 : return error;
444 : : }
445 : :
446 : : /*
447 : : * As described in commit 0ccf831cb lockdep: annotate epoll
448 : : * the use of wait queues used by epoll is done in a very controlled
449 : : * manner. Wake ups can nest inside each other, but are never done
450 : : * with the same locking. For example:
451 : : *
452 : : * dfd = socket(...);
453 : : * efd1 = epoll_create();
454 : : * efd2 = epoll_create();
455 : : * epoll_ctl(efd1, EPOLL_CTL_ADD, dfd, ...);
456 : : * epoll_ctl(efd2, EPOLL_CTL_ADD, efd1, ...);
457 : : *
458 : : * When a packet arrives to the device underneath "dfd", the net code will
459 : : * issue a wake_up() on its poll wake list. Epoll (efd1) has installed a
460 : : * callback wakeup entry on that queue, and the wake_up() performed by the
461 : : * "dfd" net code will end up in ep_poll_callback(). At this point epoll
462 : : * (efd1) notices that it may have some event ready, so it needs to wake up
463 : : * the waiters on its poll wait list (efd2). So it calls ep_poll_safewake()
464 : : * that ends up in another wake_up(), after having checked about the
465 : : * recursion constraints. That are, no more than EP_MAX_POLLWAKE_NESTS, to
466 : : * avoid stack blasting.
467 : : *
468 : : * When CONFIG_DEBUG_LOCK_ALLOC is enabled, make sure lockdep can handle
469 : : * this special case of epoll.
470 : : */
471 : : #ifdef CONFIG_DEBUG_LOCK_ALLOC
472 : : static inline void ep_wake_up_nested(wait_queue_head_t *wqueue,
473 : : unsigned long events, int subclass)
474 : : {
475 : : unsigned long flags;
476 : :
477 : : spin_lock_irqsave_nested(&wqueue->lock, flags, subclass);
478 : : wake_up_locked_poll(wqueue, events);
479 : : spin_unlock_irqrestore(&wqueue->lock, flags);
480 : : }
481 : : #else
482 : : static inline void ep_wake_up_nested(wait_queue_head_t *wqueue,
483 : : unsigned long events, int subclass)
484 : : {
485 : 0 : wake_up_poll(wqueue, events);
486 : : }
487 : : #endif
488 : :
489 : 0 : static int ep_poll_wakeup_proc(void *priv, void *cookie, int call_nests)
490 : : {
491 : : ep_wake_up_nested((wait_queue_head_t *) cookie, POLLIN,
492 : : 1 + call_nests);
493 : 0 : return 0;
494 : : }
495 : :
496 : : /*
497 : : * Perform a safe wake up of the poll wait list. The problem is that
498 : : * with the new callback'd wake up system, it is possible that the
499 : : * poll callback is reentered from inside the call to wake_up() done
500 : : * on the poll wait queue head. The rule is that we cannot reenter the
501 : : * wake up code from the same task more than EP_MAX_NESTS times,
502 : : * and we cannot reenter the same wait queue head at all. This will
503 : : * enable to have a hierarchy of epoll file descriptor of no more than
504 : : * EP_MAX_NESTS deep.
505 : : */
506 : 0 : static void ep_poll_safewake(wait_queue_head_t *wq)
507 : : {
508 : 0 : int this_cpu = get_cpu();
509 : :
510 : 0 : ep_call_nested(&poll_safewake_ncalls, EP_MAX_NESTS,
511 : : ep_poll_wakeup_proc, NULL, wq, (void *) (long) this_cpu);
512 : :
513 : 0 : put_cpu();
514 : 0 : }
515 : :
516 : : static void ep_remove_wait_queue(struct eppoll_entry *pwq)
517 : : {
518 : : wait_queue_head_t *whead;
519 : :
520 : : rcu_read_lock();
521 : : /* If it is cleared by POLLFREE, it should be rcu-safe */
522 : 0 : whead = rcu_dereference(pwq->whead);
523 [ # # ]: 0 : if (whead)
524 : 0 : remove_wait_queue(whead, &pwq->wait);
525 : : rcu_read_unlock();
526 : : }
527 : :
528 : : /*
529 : : * This function unregisters poll callbacks from the associated file
530 : : * descriptor. Must be called with "mtx" held (or "epmutex" if called from
531 : : * ep_free).
532 : : */
533 : 0 : static void ep_unregister_pollwait(struct eventpoll *ep, struct epitem *epi)
534 : : {
535 : 0 : struct list_head *lsthead = &epi->pwqlist;
536 : : struct eppoll_entry *pwq;
537 : :
538 [ # # ]: 0 : while (!list_empty(lsthead)) {
539 : : pwq = list_first_entry(lsthead, struct eppoll_entry, llink);
540 : :
541 : : list_del(&pwq->llink);
542 : : ep_remove_wait_queue(pwq);
543 : 0 : kmem_cache_free(pwq_cache, pwq);
544 : : }
545 : 0 : }
546 : :
547 : : /* call only when ep->mtx is held */
548 : : static inline struct wakeup_source *ep_wakeup_source(struct epitem *epi)
549 : : {
550 : : return rcu_dereference_check(epi->ws, lockdep_is_held(&epi->ep->mtx));
551 : : }
552 : :
553 : : /* call only when ep->mtx is held */
554 : 0 : static inline void ep_pm_stay_awake(struct epitem *epi)
555 : : {
556 : : struct wakeup_source *ws = ep_wakeup_source(epi);
557 : :
558 [ # # ]: 330 : if (ws)
[ # # - ]
[ - + ][ # # ]
559 : 654 : __pm_stay_awake(ws);
560 : : }
561 : :
562 : : static inline bool ep_has_wakeup_source(struct epitem *epi)
563 : : {
564 : : return rcu_access_pointer(epi->ws) ? true : false;
565 : : }
566 : :
567 : : /* call when ep->mtx cannot be held (ep_poll_callback) */
568 : : static inline void ep_pm_stay_awake_rcu(struct epitem *epi)
569 : : {
570 : : struct wakeup_source *ws;
571 : :
572 : : rcu_read_lock();
573 : 324 : ws = rcu_dereference(epi->ws);
574 [ - + ]: 324 : if (ws)
575 : 0 : __pm_stay_awake(ws);
576 : : rcu_read_unlock();
577 : : }
578 : :
579 : : /**
580 : : * ep_scan_ready_list - Scans the ready list in a way that makes possible for
581 : : * the scan code, to call f_op->poll(). Also allows for
582 : : * O(NumReady) performance.
583 : : *
584 : : * @ep: Pointer to the epoll private data structure.
585 : : * @sproc: Pointer to the scan callback.
586 : : * @priv: Private opaque data passed to the @sproc callback.
587 : : * @depth: The current depth of recursive f_op->poll calls.
588 : : * @ep_locked: caller already holds ep->mtx
589 : : *
590 : : * Returns: The same integer error code returned by the @sproc callback.
591 : : */
592 : 1881 : static int ep_scan_ready_list(struct eventpoll *ep,
593 : : int (*sproc)(struct eventpoll *,
594 : : struct list_head *, void *),
595 : : void *priv, int depth, bool ep_locked)
596 : : {
597 : : int error, pwake = 0;
598 : : unsigned long flags;
599 : : struct epitem *epi, *nepi;
600 : 1881 : LIST_HEAD(txlist);
601 : :
602 : : /*
603 : : * We need to lock this because we could be hit by
604 : : * eventpoll_release_file() and epoll_ctl().
605 : : */
606 : :
607 [ + - ]: 1881 : if (!ep_locked)
608 : 1881 : mutex_lock_nested(&ep->mtx, depth);
609 : :
610 : : /*
611 : : * Steal the ready list, and re-init the original one to the
612 : : * empty list. Also, set ep->ovflist to NULL so that events
613 : : * happening while looping w/out locks, are not lost. We cannot
614 : : * have the poll callback to queue directly on ep->rdllist,
615 : : * because we want the "sproc" callback to be able to do it
616 : : * in a lockless way.
617 : : */
618 : 1881 : spin_lock_irqsave(&ep->lock, flags);
619 : 1881 : list_splice_init(&ep->rdllist, &txlist);
620 : 1881 : ep->ovflist = NULL;
621 : : spin_unlock_irqrestore(&ep->lock, flags);
622 : :
623 : : /*
624 : : * Now call the callback function.
625 : : */
626 : 1881 : error = (*sproc)(ep, &txlist, priv);
627 : :
628 : 1881 : spin_lock_irqsave(&ep->lock, flags);
629 : : /*
630 : : * During the time we spent inside the "sproc" callback, some
631 : : * other events might have been queued by the poll callback.
632 : : * We re-insert them inside the main ready-list here.
633 : : */
634 [ - + ]: 1881 : for (nepi = ep->ovflist; (epi = nepi) != NULL;
635 : 0 : nepi = epi->next, epi->next = EP_UNACTIVE_PTR) {
636 : : /*
637 : : * We need to check if the item is already in the list.
638 : : * During the "sproc" callback execution time, items are
639 : : * queued into ->ovflist but the "txlist" might already
640 : : * contain them, and the list_splice() below takes care of them.
641 : : */
642 [ # # ]: 0 : if (!ep_is_linked(&epi->rdllink)) {
643 : : list_add_tail(&epi->rdllink, &ep->rdllist);
644 : : ep_pm_stay_awake(epi);
645 : : }
646 : : }
647 : : /*
648 : : * We need to set back ep->ovflist to EP_UNACTIVE_PTR, so that after
649 : : * releasing the lock, events will be queued in the normal way inside
650 : : * ep->rdllist.
651 : : */
652 : 1881 : ep->ovflist = EP_UNACTIVE_PTR;
653 : :
654 : : /*
655 : : * Quickly re-inject items left on "txlist".
656 : : */
657 : : list_splice(&txlist, &ep->rdllist);
658 : 1881 : __pm_relax(ep->ws);
659 : :
660 [ + + ]: 1881 : if (!list_empty(&ep->rdllist)) {
661 : : /*
662 : : * Wake up (if active) both the eventpoll wait list and
663 : : * the ->poll() wait list (delayed after we release the lock).
664 : : */
665 [ - + ]: 285 : if (waitqueue_active(&ep->wq))
666 : 0 : wake_up_locked(&ep->wq);
667 [ - + ]: 2166 : if (waitqueue_active(&ep->poll_wait))
668 : : pwake++;
669 : : }
670 : : spin_unlock_irqrestore(&ep->lock, flags);
671 : :
672 [ + - ]: 1881 : if (!ep_locked)
673 : 1881 : mutex_unlock(&ep->mtx);
674 : :
675 : : /* We have to call this outside the lock */
676 [ - + ]: 1881 : if (pwake)
677 : 0 : ep_poll_safewake(&ep->poll_wait);
678 : :
679 : 1881 : return error;
680 : : }
681 : :
682 : 0 : static void epi_rcu_free(struct rcu_head *head)
683 : : {
684 : : struct epitem *epi = container_of(head, struct epitem, rcu);
685 : 0 : kmem_cache_free(epi_cache, epi);
686 : 0 : }
687 : :
688 : : /*
689 : : * Removes a "struct epitem" from the eventpoll RB tree and deallocates
690 : : * all the associated resources. Must be called with "mtx" held.
691 : : */
692 : 0 : static int ep_remove(struct eventpoll *ep, struct epitem *epi)
693 : : {
694 : : unsigned long flags;
695 : 0 : struct file *file = epi->ffd.file;
696 : :
697 : : /*
698 : : * Removes poll wait queue hooks. We _have_ to do this without holding
699 : : * the "ep->lock" otherwise a deadlock might occur. This because of the
700 : : * sequence of the lock acquisition. Here we do "ep->lock" then the wait
701 : : * queue head lock when unregistering the wait queue. The wakeup callback
702 : : * will run by holding the wait queue head lock and will call our callback
703 : : * that will try to get "ep->lock".
704 : : */
705 : 0 : ep_unregister_pollwait(ep, epi);
706 : :
707 : : /* Remove the current item from the list of epoll hooks */
708 : : spin_lock(&file->f_lock);
709 : : list_del_rcu(&epi->fllink);
710 : : spin_unlock(&file->f_lock);
711 : :
712 : 0 : rb_erase(&epi->rbn, &ep->rbr);
713 : :
714 : 0 : spin_lock_irqsave(&ep->lock, flags);
715 [ # # ]: 0 : if (ep_is_linked(&epi->rdllink))
716 : : list_del_init(&epi->rdllink);
717 : : spin_unlock_irqrestore(&ep->lock, flags);
718 : :
719 : 0 : wakeup_source_unregister(ep_wakeup_source(epi));
720 : : /*
721 : : * At this point it is safe to free the eventpoll item. Use the union
722 : : * field epi->rcu, since we are trying to minimize the size of
723 : : * 'struct epitem'. The 'rbn' field is no longer in use. Protected by
724 : : * ep->mtx. The rcu read side, reverse_path_check_proc(), does not make
725 : : * use of the rbn field.
726 : : */
727 : 0 : call_rcu(&epi->rcu, epi_rcu_free);
728 : :
729 : 0 : atomic_long_dec(&ep->user->epoll_watches);
730 : :
731 : 0 : return 0;
732 : : }
733 : :
734 : 0 : static void ep_free(struct eventpoll *ep)
735 : : {
736 : : struct rb_node *rbp;
737 : : struct epitem *epi;
738 : :
739 : : /* We need to release all tasks waiting for these file */
740 [ - + ]: 35 : if (waitqueue_active(&ep->poll_wait))
741 : 0 : ep_poll_safewake(&ep->poll_wait);
742 : :
743 : : /*
744 : : * We need to lock this because we could be hit by
745 : : * eventpoll_release_file() while we're freeing the "struct eventpoll".
746 : : * We do not need to hold "ep->mtx" here because the epoll file
747 : : * is on the way to be removed and no one has references to it
748 : : * anymore. The only hit might come from eventpoll_release_file() but
749 : : * holding "epmutex" is sufficient here.
750 : : */
751 : 35 : mutex_lock(&epmutex);
752 : :
753 : : /*
754 : : * Walks through the whole tree by unregistering poll callbacks.
755 : : */
756 [ - + ]: 35 : for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
757 : : epi = rb_entry(rbp, struct epitem, rbn);
758 : :
759 : 0 : ep_unregister_pollwait(ep, epi);
760 : 0 : cond_resched();
761 : : }
762 : :
763 : : /*
764 : : * Walks through the whole tree by freeing each "struct epitem". At this
765 : : * point we are sure no poll callbacks will be lingering around, and also by
766 : : * holding "epmutex" we can be sure that no file cleanup code will hit
767 : : * us during this operation. So we can avoid the lock on "ep->lock".
768 : : * We do not need to lock ep->mtx, either, we only do it to prevent
769 : : * a lockdep warning.
770 : : */
771 : 35 : mutex_lock(&ep->mtx);
772 [ - + ]: 35 : while ((rbp = rb_first(&ep->rbr)) != NULL) {
773 : : epi = rb_entry(rbp, struct epitem, rbn);
774 : 0 : ep_remove(ep, epi);
775 : 0 : cond_resched();
776 : : }
777 : 35 : mutex_unlock(&ep->mtx);
778 : :
779 : 35 : mutex_unlock(&epmutex);
780 : : mutex_destroy(&ep->mtx);
781 : 35 : free_uid(ep->user);
782 : 35 : wakeup_source_unregister(ep->ws);
783 : 35 : kfree(ep);
784 : 35 : }
785 : :
786 : 0 : static int ep_eventpoll_release(struct inode *inode, struct file *file)
787 : : {
788 : 35 : struct eventpoll *ep = file->private_data;
789 : :
790 [ + - ]: 35 : if (ep)
791 : 35 : ep_free(ep);
792 : :
793 : 0 : return 0;
794 : : }
795 : :
796 : : static inline unsigned int ep_item_poll(struct epitem *epi, poll_table *pt)
797 : : {
798 : 654 : pt->_key = epi->event.events;
799 : :
800 : 654 : return epi->ffd.file->f_op->poll(epi->ffd.file, pt) & epi->event.events;
801 : : }
802 : :
803 : 0 : static int ep_read_events_proc(struct eventpoll *ep, struct list_head *head,
804 : : void *priv)
805 : : {
806 : 0 : struct epitem *epi, *tmp;
807 : : poll_table pt;
808 : :
809 : : init_poll_funcptr(&pt, NULL);
810 : :
811 [ - + ]: 1320 : list_for_each_entry_safe(epi, tmp, head, rdllink) {
812 [ # # ]: 0 : if (ep_item_poll(epi, &pt))
813 : : return POLLIN | POLLRDNORM;
814 : : else {
815 : : /*
816 : : * Item has been dropped into the ready list by the poll
817 : : * callback, but it's not actually ready, as far as
818 : : * caller requested events goes. We can remove it here.
819 : : */
820 : 0 : __pm_relax(ep_wakeup_source(epi));
821 : : list_del_init(&epi->rdllink);
822 : : }
823 : : }
824 : :
825 : : return 0;
826 : : }
827 : :
828 : : static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
829 : : poll_table *pt);
830 : :
831 : : struct readyevents_arg {
832 : : struct eventpoll *ep;
833 : : bool locked;
834 : : };
835 : :
836 : 0 : static int ep_poll_readyevents_proc(void *priv, void *cookie, int call_nests)
837 : : {
838 : : struct readyevents_arg *arg = priv;
839 : :
840 : 1320 : return ep_scan_ready_list(arg->ep, ep_read_events_proc, NULL,
841 : : call_nests + 1, arg->locked);
842 : : }
843 : :
844 : 0 : static unsigned int ep_eventpoll_poll(struct file *file, poll_table *wait)
845 : : {
846 : : int pollflags;
847 : 1320 : struct eventpoll *ep = file->private_data;
848 : : struct readyevents_arg arg;
849 : :
850 : : /*
851 : : * During ep_insert() we already hold the ep->mtx for the tfile.
852 : : * Prevent re-aquisition.
853 : : */
854 [ + - ][ + - ]: 1320 : arg.locked = wait && (wait->_qproc == ep_ptable_queue_proc);
855 : 1320 : arg.ep = ep;
856 : :
857 : : /* Insert inside our poll wait queue */
858 : 1320 : poll_wait(file, &ep->poll_wait, wait);
859 : :
860 : : /*
861 : : * Proceed to find out if wanted events are really available inside
862 : : * the ready list. This need to be done under ep_call_nested()
863 : : * supervision, since the call to f_op->poll() done on listed files
864 : : * could re-enter here.
865 : : */
866 : 1320 : pollflags = ep_call_nested(&poll_readywalk_ncalls, EP_MAX_NESTS,
867 : 0 : ep_poll_readyevents_proc, &arg, ep, current);
868 : :
869 [ + - ]: 1320 : return pollflags != -1 ? pollflags : 0;
870 : : }
871 : :
872 : : #ifdef CONFIG_PROC_FS
873 : 0 : static int ep_show_fdinfo(struct seq_file *m, struct file *f)
874 : : {
875 : 0 : struct eventpoll *ep = f->private_data;
876 : : struct rb_node *rbp;
877 : : int ret = 0;
878 : :
879 : 0 : mutex_lock(&ep->mtx);
880 [ # # ]: 0 : for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
881 : : struct epitem *epi = rb_entry(rbp, struct epitem, rbn);
882 : :
883 : 0 : ret = seq_printf(m, "tfd: %8d events: %8x data: %16llx\n",
884 : : epi->ffd.fd, epi->event.events,
885 : 0 : (long long)epi->event.data);
886 [ # # ]: 0 : if (ret)
887 : : break;
888 : : }
889 : 0 : mutex_unlock(&ep->mtx);
890 : :
891 : 0 : return ret;
892 : : }
893 : : #endif
894 : :
895 : : /* File callbacks that implement the eventpoll file behaviour */
896 : : static const struct file_operations eventpoll_fops = {
897 : : #ifdef CONFIG_PROC_FS
898 : : .show_fdinfo = ep_show_fdinfo,
899 : : #endif
900 : : .release = ep_eventpoll_release,
901 : : .poll = ep_eventpoll_poll,
902 : : .llseek = noop_llseek,
903 : : };
904 : :
905 : : /*
906 : : * This is called from eventpoll_release() to unlink files from the eventpoll
907 : : * interface. We need to have this facility to cleanup correctly files that are
908 : : * closed without being removed from the eventpoll interface.
909 : : */
910 : 0 : void eventpoll_release_file(struct file *file)
911 : : {
912 : : struct eventpoll *ep;
913 : : struct epitem *epi;
914 : :
915 : : /*
916 : : * We don't want to get "file->f_lock" because it is not
917 : : * necessary. It is not necessary because we're in the "struct file"
918 : : * cleanup path, and this means that no one is using this file anymore.
919 : : * So, for example, epoll_ctl() cannot hit here since if we reach this
920 : : * point, the file counter already went to zero and fget() would fail.
921 : : * The only hit might come from ep_free() but by holding the mutex
922 : : * will correctly serialize the operation. We do need to acquire
923 : : * "ep->mtx" after "epmutex" because ep_remove() requires it when called
924 : : * from anywhere but ep_free().
925 : : *
926 : : * Besides, ep_remove() acquires the lock, so we can't hold it here.
927 : : */
928 : 0 : mutex_lock(&epmutex);
929 [ # # ]: 0 : list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) {
930 : 0 : ep = epi->ep;
931 : 0 : mutex_lock_nested(&ep->mtx, 0);
932 : 0 : ep_remove(ep, epi);
933 : 0 : mutex_unlock(&ep->mtx);
934 : : }
935 : 0 : mutex_unlock(&epmutex);
936 : 0 : }
937 : :
938 : 0 : static int ep_alloc(struct eventpoll **pep)
939 : : {
940 : : int error;
941 : : struct user_struct *user;
942 : : struct eventpoll *ep;
943 : :
944 : 35 : user = get_current_user();
945 : : error = -ENOMEM;
946 : : ep = kzalloc(sizeof(*ep), GFP_KERNEL);
947 [ + - ]: 35 : if (unlikely(!ep))
948 : : goto free_uid;
949 : :
950 : 35 : spin_lock_init(&ep->lock);
951 : 35 : mutex_init(&ep->mtx);
952 : 35 : init_waitqueue_head(&ep->wq);
953 : 35 : init_waitqueue_head(&ep->poll_wait);
954 : 35 : INIT_LIST_HEAD(&ep->rdllist);
955 : 35 : ep->rbr = RB_ROOT;
956 : 35 : ep->ovflist = EP_UNACTIVE_PTR;
957 : 35 : ep->user = user;
958 : :
959 : 35 : *pep = ep;
960 : :
961 : 35 : return 0;
962 : :
963 : : free_uid:
964 : 0 : free_uid(user);
965 : 0 : return error;
966 : : }
967 : :
968 : : /*
969 : : * Search the file inside the eventpoll tree. The RB tree operations
970 : : * are protected by the "mtx" mutex, and ep_find() must be called with
971 : : * "mtx" held.
972 : : */
973 : 0 : static struct epitem *ep_find(struct eventpoll *ep, struct file *file, int fd)
974 : : {
975 : : int kcmp;
976 : : struct rb_node *rbp;
977 : : struct epitem *epi, *epir = NULL;
978 : : struct epoll_filefd ffd;
979 : :
980 : : ep_set_ffd(&ffd, file, fd);
981 [ # # ]: 0 : for (rbp = ep->rbr.rb_node; rbp; ) {
982 : : epi = rb_entry(rbp, struct epitem, rbn);
983 : : kcmp = ep_cmp_ffd(&ffd, &epi->ffd);
984 [ # # ]: 0 : if (kcmp > 0)
985 : 0 : rbp = rbp->rb_right;
986 [ # # ]: 0 : else if (kcmp < 0)
987 : 0 : rbp = rbp->rb_left;
988 : : else {
989 : : epir = epi;
990 : : break;
991 : : }
992 : : }
993 : :
994 : 0 : return epir;
995 : : }
996 : :
997 : : /*
998 : : * This is the callback that is passed to the wait queue wakeup
999 : : * mechanism. It is called by the stored file descriptors when they
1000 : : * have events to report.
1001 : : */
1002 : 0 : static int ep_poll_callback(wait_queue_t *wait, unsigned mode, int sync, void *key)
1003 : : {
1004 : : int pwake = 0;
1005 : : unsigned long flags;
1006 : : struct epitem *epi = ep_item_from_wait(wait);
1007 : 336 : struct eventpoll *ep = epi->ep;
1008 : :
1009 [ - + ]: 336 : if ((unsigned long)key & POLLFREE) {
1010 : 0 : ep_pwq_from_wait(wait)->whead = NULL;
1011 : : /*
1012 : : * whead = NULL above can race with ep_remove_wait_queue()
1013 : : * which can do another remove_wait_queue() after us, so we
1014 : : * can't use __remove_wait_queue(). whead->lock is held by
1015 : : * the caller.
1016 : : */
1017 : 0 : list_del_init(&wait->task_list);
1018 : : }
1019 : :
1020 : 336 : spin_lock_irqsave(&ep->lock, flags);
1021 : :
1022 : : /*
1023 : : * If the event mask does not contain any poll(2) event, we consider the
1024 : : * descriptor to be disabled. This condition is likely the effect of the
1025 : : * EPOLLONESHOT bit that disables the descriptor when an event is received,
1026 : : * until the next EPOLL_CTL_MOD will be issued.
1027 : : */
1028 [ + - ]: 336 : if (!(epi->event.events & ~EP_PRIVATE_BITS))
1029 : : goto out_unlock;
1030 : :
1031 : : /*
1032 : : * Check the events coming with the callback. At this stage, not
1033 : : * every device reports the events in the "key" parameter of the
1034 : : * callback. We need to be able to handle both cases here, hence the
1035 : : * test for "key" != NULL before the event match test.
1036 : : */
1037 [ + - ][ + - ]: 336 : if (key && !((unsigned long) key & epi->event.events))
1038 : : goto out_unlock;
1039 : :
1040 : : /*
1041 : : * If we are transferring events to userspace, we can hold no locks
1042 : : * (because we're accessing user memory, and because of linux f_op->poll()
1043 : : * semantics). All the events that happen during that period of time are
1044 : : * chained in ep->ovflist and requeued later on.
1045 : : */
1046 [ - + ]: 336 : if (unlikely(ep->ovflist != EP_UNACTIVE_PTR)) {
1047 [ # # ]: 0 : if (epi->next == EP_UNACTIVE_PTR) {
1048 : 0 : epi->next = ep->ovflist;
1049 : 0 : ep->ovflist = epi;
1050 [ # # ]: 0 : if (epi->ws) {
1051 : : /*
1052 : : * Activate ep->ws since epi->ws may get
1053 : : * deactivated at any time.
1054 : : */
1055 : 0 : __pm_stay_awake(ep->ws);
1056 : : }
1057 : :
1058 : : }
1059 : : goto out_unlock;
1060 : : }
1061 : :
1062 : : /* If this file is already in the ready list we exit soon */
1063 [ + + ]: 336 : if (!ep_is_linked(&epi->rdllink)) {
1064 : 324 : list_add_tail(&epi->rdllink, &ep->rdllist);
1065 : : ep_pm_stay_awake_rcu(epi);
1066 : : }
1067 : :
1068 : : /*
1069 : : * Wake up ( if active ) both the eventpoll wait list and the ->poll()
1070 : : * wait list.
1071 : : */
1072 [ + + ]: 672 : if (waitqueue_active(&ep->wq))
1073 : 327 : wake_up_locked(&ep->wq);
1074 [ - + ]: 336 : if (waitqueue_active(&ep->poll_wait))
1075 : : pwake++;
1076 : :
1077 : : out_unlock:
1078 : : spin_unlock_irqrestore(&ep->lock, flags);
1079 : :
1080 : : /* We have to call this outside the lock */
1081 [ - + ]: 336 : if (pwake)
1082 : 0 : ep_poll_safewake(&ep->poll_wait);
1083 : :
1084 : 336 : return 1;
1085 : : }
1086 : :
1087 : : /*
1088 : : * This is the callback that is used to add our wait queue to the
1089 : : * target file wakeup lists.
1090 : : */
1091 : 0 : static void ep_ptable_queue_proc(struct file *file, wait_queue_head_t *whead,
1092 : : poll_table *pt)
1093 : : {
1094 : : struct epitem *epi = ep_item_from_epqueue(pt);
1095 : : struct eppoll_entry *pwq;
1096 : :
1097 [ # # ][ # # ]: 0 : if (epi->nwait >= 0 && (pwq = kmem_cache_alloc(pwq_cache, GFP_KERNEL))) {
1098 : : init_waitqueue_func_entry(&pwq->wait, ep_poll_callback);
1099 : 0 : pwq->whead = whead;
1100 : 0 : pwq->base = epi;
1101 : 0 : add_wait_queue(whead, &pwq->wait);
1102 : 0 : list_add_tail(&pwq->llink, &epi->pwqlist);
1103 : 0 : epi->nwait++;
1104 : : } else {
1105 : : /* We have to signal that an error occurred */
1106 : 0 : epi->nwait = -1;
1107 : : }
1108 : 0 : }
1109 : :
1110 : 0 : static void ep_rbtree_insert(struct eventpoll *ep, struct epitem *epi)
1111 : : {
1112 : : int kcmp;
1113 : 0 : struct rb_node **p = &ep->rbr.rb_node, *parent = NULL;
1114 : : struct epitem *epic;
1115 : :
1116 [ # # ]: 0 : while (*p) {
1117 : : parent = *p;
1118 : : epic = rb_entry(parent, struct epitem, rbn);
1119 : : kcmp = ep_cmp_ffd(&epi->ffd, &epic->ffd);
1120 [ # # ]: 0 : if (kcmp > 0)
1121 : 0 : p = &parent->rb_right;
1122 : : else
1123 : 0 : p = &parent->rb_left;
1124 : : }
1125 : 0 : rb_link_node(&epi->rbn, parent, p);
1126 : 0 : rb_insert_color(&epi->rbn, &ep->rbr);
1127 : 0 : }
1128 : :
1129 : :
1130 : :
1131 : : #define PATH_ARR_SIZE 5
1132 : : /*
1133 : : * These are the number paths of length 1 to 5, that we are allowing to emanate
1134 : : * from a single file of interest. For example, we allow 1000 paths of length
1135 : : * 1, to emanate from each file of interest. This essentially represents the
1136 : : * potential wakeup paths, which need to be limited in order to avoid massive
1137 : : * uncontrolled wakeup storms. The common use case should be a single ep which
1138 : : * is connected to n file sources. In this case each file source has 1 path
1139 : : * of length 1. Thus, the numbers below should be more than sufficient. These
1140 : : * path limits are enforced during an EPOLL_CTL_ADD operation, since a modify
1141 : : * and delete can't add additional paths. Protected by the epmutex.
1142 : : */
1143 : : static const int path_limits[PATH_ARR_SIZE] = { 1000, 500, 100, 50, 10 };
1144 : : static int path_count[PATH_ARR_SIZE];
1145 : :
1146 : : static int path_count_inc(int nests)
1147 : : {
1148 : : /* Allow an arbitrary number of depth 1 paths */
1149 [ # # ]: 0 : if (nests == 0)
1150 : : return 0;
1151 : :
1152 [ # # ]: 0 : if (++path_count[nests] > path_limits[nests])
1153 : : return -1;
1154 : : return 0;
1155 : : }
1156 : :
1157 : : static void path_count_init(void)
1158 : : {
1159 : : int i;
1160 : :
1161 [ # # ]: 0 : for (i = 0; i < PATH_ARR_SIZE; i++)
1162 : 0 : path_count[i] = 0;
1163 : : }
1164 : :
1165 : 0 : static int reverse_path_check_proc(void *priv, void *cookie, int call_nests)
1166 : : {
1167 : : int error = 0;
1168 : : struct file *file = priv;
1169 : 0 : struct file *child_file;
1170 : : struct epitem *epi;
1171 : :
1172 : : /* CTL_DEL can remove links here, but that can't increase our count */
1173 : : rcu_read_lock();
1174 [ # # ]: 0 : list_for_each_entry_rcu(epi, &file->f_ep_links, fllink) {
1175 : 0 : child_file = epi->ep->file;
1176 [ # # ]: 0 : if (is_file_epoll(child_file)) {
1177 [ # # ]: 0 : if (list_empty(&child_file->f_ep_links)) {
1178 [ # # ]: 0 : if (path_count_inc(call_nests)) {
1179 : : error = -1;
1180 : : break;
1181 : : }
1182 : : } else {
1183 : 0 : error = ep_call_nested(&poll_loop_ncalls,
1184 : : EP_MAX_NESTS,
1185 : : reverse_path_check_proc,
1186 : : child_file, child_file,
1187 : 0 : current);
1188 : : }
1189 [ # # ]: 0 : if (error != 0)
1190 : : break;
1191 : : } else {
1192 : 0 : printk(KERN_ERR "reverse_path_check_proc: "
1193 : : "file is not an ep!\n");
1194 : : }
1195 : : }
1196 : : rcu_read_unlock();
1197 : 0 : return error;
1198 : : }
1199 : :
1200 : : /**
1201 : : * reverse_path_check - The tfile_check_list is list of file *, which have
1202 : : * links that are proposed to be newly added. We need to
1203 : : * make sure that those added links don't add too many
1204 : : * paths such that we will spend all our time waking up
1205 : : * eventpoll objects.
1206 : : *
1207 : : * Returns: Returns zero if the proposed links don't create too many paths,
1208 : : * -1 otherwise.
1209 : : */
1210 : 0 : static int reverse_path_check(void)
1211 : : {
1212 : : int error = 0;
1213 : : struct file *current_file;
1214 : :
1215 : : /* let's call this for all tfiles */
1216 [ # # ]: 0 : list_for_each_entry(current_file, &tfile_check_list, f_tfile_llink) {
1217 : : path_count_init();
1218 : 0 : error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
1219 : : reverse_path_check_proc, current_file,
1220 : 0 : current_file, current);
1221 [ # # ]: 0 : if (error)
1222 : : break;
1223 : : }
1224 : 0 : return error;
1225 : : }
1226 : :
1227 : 0 : static int ep_create_wakeup_source(struct epitem *epi)
1228 : : {
1229 : : const char *name;
1230 : : struct wakeup_source *ws;
1231 : :
1232 [ # # ]: 0 : if (!epi->ep->ws) {
1233 : 0 : epi->ep->ws = wakeup_source_register("eventpoll");
1234 [ # # ]: 0 : if (!epi->ep->ws)
1235 : : return -ENOMEM;
1236 : : }
1237 : :
1238 : 0 : name = epi->ffd.file->f_path.dentry->d_name.name;
1239 : 0 : ws = wakeup_source_register(name);
1240 : :
1241 [ # # ]: 0 : if (!ws)
1242 : : return -ENOMEM;
1243 : 0 : rcu_assign_pointer(epi->ws, ws);
1244 : :
1245 : 0 : return 0;
1246 : : }
1247 : :
1248 : : /* rare code path, only used when EPOLL_CTL_MOD removes a wakeup source */
1249 : 0 : static noinline void ep_destroy_wakeup_source(struct epitem *epi)
1250 : : {
1251 : : struct wakeup_source *ws = ep_wakeup_source(epi);
1252 : :
1253 : 0 : RCU_INIT_POINTER(epi->ws, NULL);
1254 : :
1255 : : /*
1256 : : * wait for ep_pm_stay_awake_rcu to finish, synchronize_rcu is
1257 : : * used internally by wakeup_source_remove, too (called by
1258 : : * wakeup_source_unregister), so we cannot use call_rcu
1259 : : */
1260 : : synchronize_rcu();
1261 : 0 : wakeup_source_unregister(ws);
1262 : 0 : }
1263 : :
1264 : : /*
1265 : : * Must be called with "mtx" held.
1266 : : */
1267 : 0 : static int ep_insert(struct eventpoll *ep, struct epoll_event *event,
1268 : : struct file *tfile, int fd, int full_check)
1269 : : {
1270 : : int error, revents, pwake = 0;
1271 : : unsigned long flags;
1272 : : long user_watches;
1273 : 0 : struct epitem *epi;
1274 : : struct ep_pqueue epq;
1275 : :
1276 : 0 : user_watches = atomic_long_read(&ep->user->epoll_watches);
1277 [ # # ]: 0 : if (unlikely(user_watches >= max_user_watches))
1278 : : return -ENOSPC;
1279 [ # # ]: 0 : if (!(epi = kmem_cache_alloc(epi_cache, GFP_KERNEL)))
1280 : : return -ENOMEM;
1281 : :
1282 : : /* Item initialization follow here ... */
1283 : 0 : INIT_LIST_HEAD(&epi->rdllink);
1284 : 0 : INIT_LIST_HEAD(&epi->fllink);
1285 : 0 : INIT_LIST_HEAD(&epi->pwqlist);
1286 : 0 : epi->ep = ep;
1287 : : ep_set_ffd(&epi->ffd, tfile, fd);
1288 : 0 : epi->event = *event;
1289 : 0 : epi->nwait = 0;
1290 : 0 : epi->next = EP_UNACTIVE_PTR;
1291 [ # # ]: 0 : if (epi->event.events & EPOLLWAKEUP) {
1292 : 0 : error = ep_create_wakeup_source(epi);
1293 [ # # ]: 0 : if (error)
1294 : : goto error_create_wakeup_source;
1295 : : } else {
1296 : 0 : RCU_INIT_POINTER(epi->ws, NULL);
1297 : : }
1298 : :
1299 : : /* Initialize the poll table using the queue callback */
1300 : 0 : epq.epi = epi;
1301 : : init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
1302 : :
1303 : : /*
1304 : : * Attach the item to the poll hooks and get current event bits.
1305 : : * We can safely use the file* here because its usage count has
1306 : : * been increased by the caller of this function. Note that after
1307 : : * this operation completes, the poll callback can start hitting
1308 : : * the new item.
1309 : : */
1310 : : revents = ep_item_poll(epi, &epq.pt);
1311 : :
1312 : : /*
1313 : : * We have to check if something went wrong during the poll wait queue
1314 : : * install process. Namely an allocation for a wait queue failed due
1315 : : * high memory pressure.
1316 : : */
1317 : : error = -ENOMEM;
1318 [ # # ]: 0 : if (epi->nwait < 0)
1319 : : goto error_unregister;
1320 : :
1321 : : /* Add the current item to the list of active epoll hook for this file */
1322 : : spin_lock(&tfile->f_lock);
1323 : 0 : list_add_tail_rcu(&epi->fllink, &tfile->f_ep_links);
1324 : : spin_unlock(&tfile->f_lock);
1325 : :
1326 : : /*
1327 : : * Add the current item to the RB tree. All RB tree operations are
1328 : : * protected by "mtx", and ep_insert() is called with "mtx" held.
1329 : : */
1330 : 0 : ep_rbtree_insert(ep, epi);
1331 : :
1332 : : /* now check if we've created too many backpaths */
1333 : : error = -EINVAL;
1334 [ # # ][ # # ]: 0 : if (full_check && reverse_path_check())
1335 : : goto error_remove_epi;
1336 : :
1337 : : /* We have to drop the new item inside our item list to keep track of it */
1338 : 0 : spin_lock_irqsave(&ep->lock, flags);
1339 : :
1340 : : /* If the file is already "ready" we drop it inside the ready list */
1341 [ # # ][ # # ]: 0 : if ((revents & event->events) && !ep_is_linked(&epi->rdllink)) {
1342 : 0 : list_add_tail(&epi->rdllink, &ep->rdllist);
1343 : : ep_pm_stay_awake(epi);
1344 : :
1345 : : /* Notify waiting tasks that events are available */
1346 [ # # ]: 0 : if (waitqueue_active(&ep->wq))
1347 : 0 : wake_up_locked(&ep->wq);
1348 [ # # ]: 0 : if (waitqueue_active(&ep->poll_wait))
1349 : : pwake++;
1350 : : }
1351 : :
1352 : : spin_unlock_irqrestore(&ep->lock, flags);
1353 : :
1354 : 0 : atomic_long_inc(&ep->user->epoll_watches);
1355 : :
1356 : : /* We have to call this outside the lock */
1357 [ # # ]: 0 : if (pwake)
1358 : 0 : ep_poll_safewake(&ep->poll_wait);
1359 : :
1360 : : return 0;
1361 : :
1362 : : error_remove_epi:
1363 : : spin_lock(&tfile->f_lock);
1364 : : list_del_rcu(&epi->fllink);
1365 : : spin_unlock(&tfile->f_lock);
1366 : :
1367 : 0 : rb_erase(&epi->rbn, &ep->rbr);
1368 : :
1369 : : error_unregister:
1370 : 0 : ep_unregister_pollwait(ep, epi);
1371 : :
1372 : : /*
1373 : : * We need to do this because an event could have been arrived on some
1374 : : * allocated wait queue. Note that we don't care about the ep->ovflist
1375 : : * list, since that is used/cleaned only inside a section bound by "mtx".
1376 : : * And ep_insert() is called with "mtx" held.
1377 : : */
1378 : 0 : spin_lock_irqsave(&ep->lock, flags);
1379 [ # # ]: 0 : if (ep_is_linked(&epi->rdllink))
1380 : : list_del_init(&epi->rdllink);
1381 : : spin_unlock_irqrestore(&ep->lock, flags);
1382 : :
1383 : 0 : wakeup_source_unregister(ep_wakeup_source(epi));
1384 : :
1385 : : error_create_wakeup_source:
1386 : 0 : kmem_cache_free(epi_cache, epi);
1387 : :
1388 : 0 : return error;
1389 : : }
1390 : :
1391 : : /*
1392 : : * Modify the interest event mask by dropping an event if the new mask
1393 : : * has a match in the current file status. Must be called with "mtx" held.
1394 : : */
1395 : 0 : static int ep_modify(struct eventpoll *ep, struct epitem *epi, struct epoll_event *event)
1396 : : {
1397 : : int pwake = 0;
1398 : : unsigned int revents;
1399 : : poll_table pt;
1400 : :
1401 : : init_poll_funcptr(&pt, NULL);
1402 : :
1403 : : /*
1404 : : * Set the new event interest mask before calling f_op->poll();
1405 : : * otherwise we might miss an event that happens between the
1406 : : * f_op->poll() call and the new event set registering.
1407 : : */
1408 : 0 : epi->event.events = event->events; /* need barrier below */
1409 : 0 : epi->event.data = event->data; /* protected by mtx */
1410 [ # # ]: 0 : if (epi->event.events & EPOLLWAKEUP) {
1411 [ # # ]: 0 : if (!ep_has_wakeup_source(epi))
1412 : 0 : ep_create_wakeup_source(epi);
1413 [ # # ]: 0 : } else if (ep_has_wakeup_source(epi)) {
1414 : 0 : ep_destroy_wakeup_source(epi);
1415 : : }
1416 : :
1417 : : /*
1418 : : * The following barrier has two effects:
1419 : : *
1420 : : * 1) Flush epi changes above to other CPUs. This ensures
1421 : : * we do not miss events from ep_poll_callback if an
1422 : : * event occurs immediately after we call f_op->poll().
1423 : : * We need this because we did not take ep->lock while
1424 : : * changing epi above (but ep_poll_callback does take
1425 : : * ep->lock).
1426 : : *
1427 : : * 2) We also need to ensure we do not miss _past_ events
1428 : : * when calling f_op->poll(). This barrier also
1429 : : * pairs with the barrier in wq_has_sleeper (see
1430 : : * comments for wq_has_sleeper).
1431 : : *
1432 : : * This barrier will now guarantee ep_poll_callback or f_op->poll
1433 : : * (or both) will notice the readiness of an item.
1434 : : */
1435 : 0 : smp_mb();
1436 : :
1437 : : /*
1438 : : * Get current event bits. We can safely use the file* here because
1439 : : * its usage count has been increased by the caller of this function.
1440 : : */
1441 : : revents = ep_item_poll(epi, &pt);
1442 : :
1443 : : /*
1444 : : * If the item is "hot" and it is not registered inside the ready
1445 : : * list, push it inside.
1446 : : */
1447 [ # # ]: 0 : if (revents & event->events) {
1448 : : spin_lock_irq(&ep->lock);
1449 [ # # ]: 0 : if (!ep_is_linked(&epi->rdllink)) {
1450 : 0 : list_add_tail(&epi->rdllink, &ep->rdllist);
1451 : : ep_pm_stay_awake(epi);
1452 : :
1453 : : /* Notify waiting tasks that events are available */
1454 [ # # ]: 0 : if (waitqueue_active(&ep->wq))
1455 : 0 : wake_up_locked(&ep->wq);
1456 [ # # ]: 0 : if (waitqueue_active(&ep->poll_wait))
1457 : : pwake++;
1458 : : }
1459 : : spin_unlock_irq(&ep->lock);
1460 : : }
1461 : :
1462 : : /* We have to call this outside the lock */
1463 [ # # ]: 0 : if (pwake)
1464 : 0 : ep_poll_safewake(&ep->poll_wait);
1465 : :
1466 : 0 : return 0;
1467 : : }
1468 : :
1469 : 0 : static int ep_send_events_proc(struct eventpoll *ep, struct list_head *head,
1470 : : void *priv)
1471 : : {
1472 : : struct ep_send_events_data *esed = priv;
1473 : : int eventcnt;
1474 : : unsigned int revents;
1475 : 654 : struct epitem *epi;
1476 : : struct epoll_event __user *uevent;
1477 : : struct wakeup_source *ws;
1478 : : poll_table pt;
1479 : :
1480 : : init_poll_funcptr(&pt, NULL);
1481 : :
1482 : : /*
1483 : : * We can loop without lock because we are passed a task private list.
1484 : : * Items cannot vanish during the loop because ep_scan_ready_list() is
1485 : : * holding "mtx" during this call.
1486 : : */
1487 [ + + ]: 1215 : for (eventcnt = 0, uevent = esed->events;
1488 [ + - ]: 654 : !list_empty(head) && eventcnt < esed->maxevents;) {
1489 : : epi = list_first_entry(head, struct epitem, rdllink);
1490 : :
1491 : : /*
1492 : : * Activate ep->ws before deactivating epi->ws to prevent
1493 : : * triggering auto-suspend here (in case we reactive epi->ws
1494 : : * below).
1495 : : *
1496 : : * This could be rearranged to delay the deactivation of epi->ws
1497 : : * instead, but then epi->ws would temporarily be out of sync
1498 : : * with ep_is_linked().
1499 : : */
1500 : : ws = ep_wakeup_source(epi);
1501 [ - + ]: 654 : if (ws) {
1502 [ # # ]: 0 : if (ws->active)
1503 : 0 : __pm_stay_awake(ep->ws);
1504 : 0 : __pm_relax(ws);
1505 : : }
1506 : :
1507 : 654 : list_del_init(&epi->rdllink);
1508 : :
1509 : : revents = ep_item_poll(epi, &pt);
1510 : :
1511 : : /*
1512 : : * If the event mask intersect the caller-requested one,
1513 : : * deliver the event to userspace. Again, ep_scan_ready_list()
1514 : : * is holding "mtx", so no operations coming from userspace
1515 : : * can change the item.
1516 : : */
1517 [ + + ]: 654 : if (revents) {
1518 [ + - - + ]: 660 : if (__put_user(revents, &uevent->events) ||
1519 : 330 : __put_user(epi->event.data, &uevent->data)) {
1520 : : list_add(&epi->rdllink, head);
1521 : : ep_pm_stay_awake(epi);
1522 [ # # ]: 0 : return eventcnt ? eventcnt : -EFAULT;
1523 : : }
1524 : 330 : eventcnt++;
1525 : 330 : uevent++;
1526 [ - + ]: 330 : if (epi->event.events & EPOLLONESHOT)
1527 : 0 : epi->event.events &= EP_PRIVATE_BITS;
1528 [ + - ]: 330 : else if (!(epi->event.events & EPOLLET)) {
1529 : : /*
1530 : : * If this file has been added with Level
1531 : : * Trigger mode, we need to insert back inside
1532 : : * the ready list, so that the next call to
1533 : : * epoll_wait() will check again the events
1534 : : * availability. At this point, no one can insert
1535 : : * into ep->rdllist besides us. The epoll_ctl()
1536 : : * callers are locked out by
1537 : : * ep_scan_ready_list() holding "mtx" and the
1538 : : * poll callback will queue them in ep->ovflist.
1539 : : */
1540 : 330 : list_add_tail(&epi->rdllink, &ep->rdllist);
1541 : : ep_pm_stay_awake(epi);
1542 : : }
1543 : : }
1544 : : }
1545 : :
1546 : : return eventcnt;
1547 : : }
1548 : :
1549 : : static int ep_send_events(struct eventpoll *ep,
1550 : : struct epoll_event __user *events, int maxevents)
1551 : : {
1552 : : struct ep_send_events_data esed;
1553 : :
1554 : 561 : esed.maxevents = maxevents;
1555 : 561 : esed.events = events;
1556 : :
1557 : 561 : return ep_scan_ready_list(ep, ep_send_events_proc, &esed, 0, false);
1558 : : }
1559 : :
1560 : : static inline struct timespec ep_set_mstimeout(long ms)
1561 : : {
1562 : 0 : struct timespec now, ts = {
1563 : 0 : .tv_sec = ms / MSEC_PER_SEC,
1564 : 0 : .tv_nsec = NSEC_PER_MSEC * (ms % MSEC_PER_SEC),
1565 : : };
1566 : :
1567 : 0 : ktime_get_ts(&now);
1568 : 0 : return timespec_add_safe(now, ts);
1569 : : }
1570 : :
1571 : : /**
1572 : : * ep_poll - Retrieves ready events, and delivers them to the caller supplied
1573 : : * event buffer.
1574 : : *
1575 : : * @ep: Pointer to the eventpoll context.
1576 : : * @events: Pointer to the userspace buffer where the ready events should be
1577 : : * stored.
1578 : : * @maxevents: Size (in terms of number of events) of the caller event buffer.
1579 : : * @timeout: Maximum timeout for the ready events fetch operation, in
1580 : : * milliseconds. If the @timeout is zero, the function will not block,
1581 : : * while if the @timeout is less than zero, the function will block
1582 : : * until at least one event has been retrieved (or an error
1583 : : * occurred).
1584 : : *
1585 : : * Returns: Returns the number of ready events which have been fetched, or an
1586 : : * error code, in case of error.
1587 : : */
1588 : 0 : static int ep_poll(struct eventpoll *ep, struct epoll_event __user *events,
1589 : : int maxevents, long timeout)
1590 : : {
1591 : : int res = 0, eavail, timed_out = 0;
1592 : : unsigned long flags;
1593 : : long slack = 0;
1594 : : wait_queue_t wait;
1595 : : ktime_t expires, *to = NULL;
1596 : :
1597 [ - + ]: 285 : if (timeout > 0) {
1598 : : struct timespec end_time = ep_set_mstimeout(timeout);
1599 : :
1600 : 0 : slack = select_estimate_accuracy(&end_time);
1601 : : to = &expires;
1602 : 0 : *to = timespec_to_ktime(end_time);
1603 [ - + ]: 285 : } else if (timeout == 0) {
1604 : : /*
1605 : : * Avoid the unnecessary trip to the wait queue loop, if the
1606 : : * caller specified a non blocking operation.
1607 : : */
1608 : : timed_out = 1;
1609 : 0 : spin_lock_irqsave(&ep->lock, flags);
1610 : 0 : goto check_events;
1611 : : }
1612 : :
1613 : : fetch_events:
1614 : 561 : spin_lock_irqsave(&ep->lock, flags);
1615 : :
1616 [ + + ]: 561 : if (!ep_events_available(ep)) {
1617 : : /*
1618 : : * We don't have any available event to return to the caller.
1619 : : * We need to sleep here, and we will be wake up by
1620 : : * ep_poll_callback() when events will become available.
1621 : : */
1622 : 276 : init_waitqueue_entry(&wait, current);
1623 : : __add_wait_queue_exclusive(&ep->wq, &wait);
1624 : :
1625 : : for (;;) {
1626 : : /*
1627 : : * We don't want to sleep if the ep_poll_callback() sends us
1628 : : * a wakeup in between. That's why we set the task state
1629 : : * to TASK_INTERRUPTIBLE before doing the checks.
1630 : : */
1631 : 552 : set_current_state(TASK_INTERRUPTIBLE);
1632 [ + + ][ + - ]: 552 : if (ep_events_available(ep) || timed_out)
1633 : : break;
1634 [ + - ]: 276 : if (signal_pending(current)) {
1635 : : res = -EINTR;
1636 : : break;
1637 : : }
1638 : :
1639 : : spin_unlock_irqrestore(&ep->lock, flags);
1640 [ - + ]: 276 : if (!schedule_hrtimeout_range(to, slack, HRTIMER_MODE_ABS))
1641 : : timed_out = 1;
1642 : :
1643 : 276 : spin_lock_irqsave(&ep->lock, flags);
1644 : 276 : }
1645 : : __remove_wait_queue(&ep->wq, &wait);
1646 : :
1647 : 276 : set_current_state(TASK_RUNNING);
1648 : : }
1649 : : check_events:
1650 : : /* Is it worth to try to dig for events ? */
1651 : : eavail = ep_events_available(ep);
1652 : :
1653 : : spin_unlock_irqrestore(&ep->lock, flags);
1654 : :
1655 : : /*
1656 : : * Try to transfer events to user space. In case we get 0 events and
1657 : : * there's still timeout left over, we go trying again in search of
1658 : : * more luck.
1659 : : */
1660 [ + - + + ]: 1122 : if (!res && eavail &&
1661 [ + - ]: 276 : !(res = ep_send_events(ep, events, maxevents)) && !timed_out)
1662 : : goto fetch_events;
1663 : :
1664 : 285 : return res;
1665 : : }
1666 : :
1667 : : /**
1668 : : * ep_loop_check_proc - Callback function to be passed to the @ep_call_nested()
1669 : : * API, to verify that adding an epoll file inside another
1670 : : * epoll structure, does not violate the constraints, in
1671 : : * terms of closed loops, or too deep chains (which can
1672 : : * result in excessive stack usage).
1673 : : *
1674 : : * @priv: Pointer to the epoll file to be currently checked.
1675 : : * @cookie: Original cookie for this call. This is the top-of-the-chain epoll
1676 : : * data structure pointer.
1677 : : * @call_nests: Current dept of the @ep_call_nested() call stack.
1678 : : *
1679 : : * Returns: Returns zero if adding the epoll @file inside current epoll
1680 : : * structure @ep does not violate the constraints, or -1 otherwise.
1681 : : */
1682 : 0 : static int ep_loop_check_proc(void *priv, void *cookie, int call_nests)
1683 : : {
1684 : : int error = 0;
1685 : : struct file *file = priv;
1686 : 0 : struct eventpoll *ep = file->private_data;
1687 : : struct eventpoll *ep_tovisit;
1688 : : struct rb_node *rbp;
1689 : : struct epitem *epi;
1690 : :
1691 : 0 : mutex_lock_nested(&ep->mtx, call_nests + 1);
1692 : 0 : ep->visited = 1;
1693 : 0 : list_add(&ep->visited_list_link, &visited_list);
1694 [ # # ]: 0 : for (rbp = rb_first(&ep->rbr); rbp; rbp = rb_next(rbp)) {
1695 : : epi = rb_entry(rbp, struct epitem, rbn);
1696 [ # # ]: 0 : if (unlikely(is_file_epoll(epi->ffd.file))) {
1697 : 0 : ep_tovisit = epi->ffd.file->private_data;
1698 [ # # ]: 0 : if (ep_tovisit->visited)
1699 : 0 : continue;
1700 : 0 : error = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
1701 : : ep_loop_check_proc, epi->ffd.file,
1702 : 0 : ep_tovisit, current);
1703 [ # # ]: 0 : if (error != 0)
1704 : : break;
1705 : : } else {
1706 : : /*
1707 : : * If we've reached a file that is not associated with
1708 : : * an ep, then we need to check if the newly added
1709 : : * links are going to add too many wakeup paths. We do
1710 : : * this by adding it to the tfile_check_list, if it's
1711 : : * not already there, and calling reverse_path_check()
1712 : : * during ep_insert().
1713 : : */
1714 [ # # ]: 0 : if (list_empty(&epi->ffd.file->f_tfile_llink))
1715 : : list_add(&epi->ffd.file->f_tfile_llink,
1716 : : &tfile_check_list);
1717 : : }
1718 : : }
1719 : 0 : mutex_unlock(&ep->mtx);
1720 : :
1721 : 0 : return error;
1722 : : }
1723 : :
1724 : : /**
1725 : : * ep_loop_check - Performs a check to verify that adding an epoll file (@file)
1726 : : * another epoll file (represented by @ep) does not create
1727 : : * closed loops or too deep chains.
1728 : : *
1729 : : * @ep: Pointer to the epoll private data structure.
1730 : : * @file: Pointer to the epoll file to be checked.
1731 : : *
1732 : : * Returns: Returns zero if adding the epoll @file inside current epoll
1733 : : * structure @ep does not violate the constraints, or -1 otherwise.
1734 : : */
1735 : 0 : static int ep_loop_check(struct eventpoll *ep, struct file *file)
1736 : : {
1737 : : int ret;
1738 : : struct eventpoll *ep_cur, *ep_next;
1739 : :
1740 : 0 : ret = ep_call_nested(&poll_loop_ncalls, EP_MAX_NESTS,
1741 : 0 : ep_loop_check_proc, file, ep, current);
1742 : : /* clear visited list */
1743 [ # # ]: 0 : list_for_each_entry_safe(ep_cur, ep_next, &visited_list,
1744 : : visited_list_link) {
1745 : 0 : ep_cur->visited = 0;
1746 : : list_del(&ep_cur->visited_list_link);
1747 : : }
1748 : 0 : return ret;
1749 : : }
1750 : :
1751 : 0 : static void clear_tfile_check_list(void)
1752 : : {
1753 : : struct file *file;
1754 : :
1755 : : /* first clear the tfile_check_list */
1756 [ # # ]: 0 : while (!list_empty(&tfile_check_list)) {
1757 : : file = list_first_entry(&tfile_check_list, struct file,
1758 : : f_tfile_llink);
1759 : 0 : list_del_init(&file->f_tfile_llink);
1760 : : }
1761 : : INIT_LIST_HEAD(&tfile_check_list);
1762 : 0 : }
1763 : :
1764 : : /*
1765 : : * Open an eventpoll file descriptor.
1766 : : */
1767 : 0 : SYSCALL_DEFINE1(epoll_create1, int, flags)
1768 : : {
1769 : : int error, fd;
1770 : 35 : struct eventpoll *ep = NULL;
1771 : : struct file *file;
1772 : :
1773 : : /* Check the EPOLL_* constant for consistency. */
1774 : : BUILD_BUG_ON(EPOLL_CLOEXEC != O_CLOEXEC);
1775 : :
1776 [ + - ]: 35 : if (flags & ~EPOLL_CLOEXEC)
1777 : : return -EINVAL;
1778 : : /*
1779 : : * Create the internal data structure ("struct eventpoll").
1780 : : */
1781 : 35 : error = ep_alloc(&ep);
1782 [ + - ]: 35 : if (error < 0)
1783 : : return error;
1784 : : /*
1785 : : * Creates all the items needed to setup an eventpoll file. That is,
1786 : : * a file structure and a free file descriptor.
1787 : : */
1788 : 35 : fd = get_unused_fd_flags(O_RDWR | (flags & O_CLOEXEC));
1789 [ + - ]: 35 : if (fd < 0) {
1790 : : error = fd;
1791 : : goto out_free_ep;
1792 : : }
1793 : 35 : file = anon_inode_getfile("[eventpoll]", &eventpoll_fops, ep,
1794 : : O_RDWR | (flags & O_CLOEXEC));
1795 [ - + ]: 35 : if (IS_ERR(file)) {
1796 : : error = PTR_ERR(file);
1797 : : goto out_free_fd;
1798 : : }
1799 : 35 : ep->file = file;
1800 : 35 : fd_install(fd, file);
1801 : : return fd;
1802 : :
1803 : : out_free_fd:
1804 : 0 : put_unused_fd(fd);
1805 : : out_free_ep:
1806 : 0 : ep_free(ep);
1807 : : return error;
1808 : : }
1809 : :
1810 : 0 : SYSCALL_DEFINE1(epoll_create, int, size)
1811 : : {
1812 [ + + ]: 34 : if (size <= 0)
1813 : : return -EINVAL;
1814 : :
1815 : 33 : return sys_epoll_create1(0);
1816 : : }
1817 : :
1818 : : /*
1819 : : * The following function implements the controller interface for
1820 : : * the eventpoll file that enables the insertion/removal/change of
1821 : : * file descriptors inside the interest set.
1822 : : */
1823 : 0 : SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
1824 : : struct epoll_event __user *, event)
1825 : : {
1826 : : int error;
1827 : : int full_check = 0;
1828 : : struct fd f, tf;
1829 : 0 : struct eventpoll *ep;
1830 : : struct epitem *epi;
1831 : : struct epoll_event epds;
1832 : : struct eventpoll *tep = NULL;
1833 : :
1834 : : error = -EFAULT;
1835 [ + + ][ + + ]: 23040 : if (ep_op_has_event(op) &&
1836 : : copy_from_user(&epds, event, sizeof(struct epoll_event)))
1837 : : goto error_return;
1838 : :
1839 : : error = -EBADF;
1840 : 10752 : f = fdget(epfd);
1841 [ + + ]: 10752 : if (!f.file)
1842 : : goto error_return;
1843 : :
1844 : : /* Get the "struct file *" for the target file */
1845 : 3840 : tf = fdget(fd);
1846 [ - + ]: 3840 : if (!tf.file)
1847 : : goto error_fput;
1848 : :
1849 : : /* The target file descriptor must support poll */
1850 : : error = -EPERM;
1851 [ # # ]: 0 : if (!tf.file->f_op->poll)
1852 : : goto error_tgt_fput;
1853 : :
1854 : : /* Check if EPOLLWAKEUP is allowed */
1855 : : ep_take_care_of_epollwakeup(&epds);
1856 : :
1857 : : /*
1858 : : * We have to check that the file structure underneath the file descriptor
1859 : : * the user passed to us _is_ an eventpoll file. And also we do not permit
1860 : : * adding an epoll file descriptor inside itself.
1861 : : */
1862 : : error = -EINVAL;
1863 [ # # ][ # # ]: 0 : if (f.file == tf.file || !is_file_epoll(f.file))
1864 : : goto error_tgt_fput;
1865 : :
1866 : : /*
1867 : : * At this point it is safe to assume that the "private_data" contains
1868 : : * our own data structure.
1869 : : */
1870 : 0 : ep = f.file->private_data;
1871 : :
1872 : : /*
1873 : : * When we insert an epoll file descriptor, inside another epoll file
1874 : : * descriptor, there is the change of creating closed loops, which are
1875 : : * better be handled here, than in more critical paths. While we are
1876 : : * checking for loops we also determine the list of files reachable
1877 : : * and hang them on the tfile_check_list, so we can check that we
1878 : : * haven't created too many possible wakeup paths.
1879 : : *
1880 : : * We do not need to take the global 'epumutex' on EPOLL_CTL_ADD when
1881 : : * the epoll file descriptor is attaching directly to a wakeup source,
1882 : : * unless the epoll file descriptor is nested. The purpose of taking the
1883 : : * 'epmutex' on add is to prevent complex toplogies such as loops and
1884 : : * deep wakeup paths from forming in parallel through multiple
1885 : : * EPOLL_CTL_ADD operations.
1886 : : */
1887 : 0 : mutex_lock_nested(&ep->mtx, 0);
1888 [ # # ]: 0 : if (op == EPOLL_CTL_ADD) {
1889 [ # # ][ # # ]: 0 : if (!list_empty(&f.file->f_ep_links) ||
1890 : : is_file_epoll(tf.file)) {
1891 : : full_check = 1;
1892 : 0 : mutex_unlock(&ep->mtx);
1893 : 0 : mutex_lock(&epmutex);
1894 [ # # ]: 0 : if (is_file_epoll(tf.file)) {
1895 : : error = -ELOOP;
1896 [ # # ]: 0 : if (ep_loop_check(ep, tf.file) != 0) {
1897 : 0 : clear_tfile_check_list();
1898 : : goto error_tgt_fput;
1899 : : }
1900 : : } else
1901 : 0 : list_add(&tf.file->f_tfile_llink,
1902 : : &tfile_check_list);
1903 : 0 : mutex_lock_nested(&ep->mtx, 0);
1904 [ # # ]: 0 : if (is_file_epoll(tf.file)) {
1905 : 0 : tep = tf.file->private_data;
1906 : 0 : mutex_lock_nested(&tep->mtx, 1);
1907 : : }
1908 : : }
1909 : : }
1910 : :
1911 : : /*
1912 : : * Try to lookup the file inside our RB tree, Since we grabbed "mtx"
1913 : : * above, we can be sure to be able to use the item looked up by
1914 : : * ep_find() till we release the mutex.
1915 : : */
1916 : 0 : epi = ep_find(ep, tf.file, fd);
1917 : :
1918 : : error = -EINVAL;
1919 [ # # # # ]: 0 : switch (op) {
1920 : : case EPOLL_CTL_ADD:
1921 [ # # ]: 0 : if (!epi) {
1922 : 0 : epds.events |= POLLERR | POLLHUP;
1923 : 0 : error = ep_insert(ep, &epds, tf.file, fd, full_check);
1924 : : } else
1925 : : error = -EEXIST;
1926 [ # # ]: 0 : if (full_check)
1927 : 0 : clear_tfile_check_list();
1928 : : break;
1929 : : case EPOLL_CTL_DEL:
1930 [ # # ]: 0 : if (epi)
1931 : 0 : error = ep_remove(ep, epi);
1932 : : else
1933 : : error = -ENOENT;
1934 : : break;
1935 : : case EPOLL_CTL_MOD:
1936 [ # # ]: 0 : if (epi) {
1937 : 0 : epds.events |= POLLERR | POLLHUP;
1938 : 0 : error = ep_modify(ep, epi, &epds);
1939 : : } else
1940 : : error = -ENOENT;
1941 : : break;
1942 : : }
1943 [ # # ]: 0 : if (tep != NULL)
1944 : 0 : mutex_unlock(&tep->mtx);
1945 : 0 : mutex_unlock(&ep->mtx);
1946 : :
1947 : : error_tgt_fput:
1948 [ # # ]: 13824 : if (full_check)
1949 : 0 : mutex_unlock(&epmutex);
1950 : :
1951 : : fdput(tf);
1952 : : error_fput:
1953 : : fdput(f);
1954 : : error_return:
1955 : :
1956 : : return error;
1957 : : }
1958 : :
1959 : : /*
1960 : : * Implement the event wait interface for the eventpoll file. It is the kernel
1961 : : * part of the user space epoll_wait(2).
1962 : : */
1963 : 0 : SYSCALL_DEFINE4(epoll_wait, int, epfd, struct epoll_event __user *, events,
1964 : : int, maxevents, int, timeout)
1965 : : {
1966 : : int error;
1967 : : struct fd f;
1968 : : struct eventpoll *ep;
1969 : :
1970 : : /* The maximum number of event must be greater than zero */
1971 [ + - ]: 285 : if (maxevents <= 0 || maxevents > EP_MAX_EVENTS)
1972 : : return -EINVAL;
1973 : :
1974 : : /* Verify that the area passed by the user is writeable */
1975 [ + - ]: 285 : if (!access_ok(VERIFY_WRITE, events, maxevents * sizeof(struct epoll_event)))
1976 : : return -EFAULT;
1977 : :
1978 : : /* Get the "struct file *" for the eventpoll file */
1979 : 285 : f = fdget(epfd);
1980 [ + - ]: 285 : if (!f.file)
1981 : : return -EBADF;
1982 : :
1983 : : /*
1984 : : * We have to check that the file structure underneath the fd
1985 : : * the user passed to us _is_ an eventpoll file.
1986 : : */
1987 : : error = -EINVAL;
1988 [ + - ]: 285 : if (!is_file_epoll(f.file))
1989 : : goto error_fput;
1990 : :
1991 : : /*
1992 : : * At this point it is safe to assume that the "private_data" contains
1993 : : * our own data structure.
1994 : : */
1995 : 285 : ep = f.file->private_data;
1996 : :
1997 : : /* Time to fish for events ... */
1998 : 285 : error = ep_poll(ep, events, maxevents, timeout);
1999 : :
2000 : : error_fput:
2001 : : fdput(f);
2002 : : return error;
2003 : : }
2004 : :
2005 : : /*
2006 : : * Implement the event wait interface for the eventpoll file. It is the kernel
2007 : : * part of the user space epoll_pwait(2).
2008 : : */
2009 : 0 : SYSCALL_DEFINE6(epoll_pwait, int, epfd, struct epoll_event __user *, events,
2010 : : int, maxevents, int, timeout, const sigset_t __user *, sigmask,
2011 : : size_t, sigsetsize)
2012 : : {
2013 : : int error;
2014 : : sigset_t ksigmask, sigsaved;
2015 : :
2016 : : /*
2017 : : * If the caller wants a certain signal mask to be set during the wait,
2018 : : * we apply it here.
2019 : : */
2020 [ # # ]: 0 : if (sigmask) {
2021 [ # # ]: 0 : if (sigsetsize != sizeof(sigset_t))
2022 : : return -EINVAL;
2023 [ # # ]: 0 : if (copy_from_user(&ksigmask, sigmask, sizeof(ksigmask)))
2024 : : return -EFAULT;
2025 : 0 : sigsaved = current->blocked;
2026 : 0 : set_current_blocked(&ksigmask);
2027 : : }
2028 : :
2029 : 0 : error = sys_epoll_wait(epfd, events, maxevents, timeout);
2030 : :
2031 : : /*
2032 : : * If we changed the signal mask, we need to restore the original one.
2033 : : * In case we've got a signal while waiting, we do not restore the
2034 : : * signal mask yet, and we allow do_signal() to deliver the signal on
2035 : : * the way back to userspace, before the signal mask is restored.
2036 : : */
2037 [ # # ]: 0 : if (sigmask) {
2038 [ # # ]: 0 : if (error == -EINTR) {
2039 : 0 : memcpy(¤t->saved_sigmask, &sigsaved,
2040 : : sizeof(sigsaved));
2041 : : set_restore_sigmask();
2042 : : } else
2043 : 0 : set_current_blocked(&sigsaved);
2044 : : }
2045 : :
2046 : : return error;
2047 : : }
2048 : :
2049 : : #ifdef CONFIG_COMPAT
2050 : : COMPAT_SYSCALL_DEFINE6(epoll_pwait, int, epfd,
2051 : : struct epoll_event __user *, events,
2052 : : int, maxevents, int, timeout,
2053 : : const compat_sigset_t __user *, sigmask,
2054 : : compat_size_t, sigsetsize)
2055 : : {
2056 : : long err;
2057 : : compat_sigset_t csigmask;
2058 : : sigset_t ksigmask, sigsaved;
2059 : :
2060 : : /*
2061 : : * If the caller wants a certain signal mask to be set during the wait,
2062 : : * we apply it here.
2063 : : */
2064 : : if (sigmask) {
2065 : : if (sigsetsize != sizeof(compat_sigset_t))
2066 : : return -EINVAL;
2067 : : if (copy_from_user(&csigmask, sigmask, sizeof(csigmask)))
2068 : : return -EFAULT;
2069 : : sigset_from_compat(&ksigmask, &csigmask);
2070 : : sigsaved = current->blocked;
2071 : : set_current_blocked(&ksigmask);
2072 : : }
2073 : :
2074 : : err = sys_epoll_wait(epfd, events, maxevents, timeout);
2075 : :
2076 : : /*
2077 : : * If we changed the signal mask, we need to restore the original one.
2078 : : * In case we've got a signal while waiting, we do not restore the
2079 : : * signal mask yet, and we allow do_signal() to deliver the signal on
2080 : : * the way back to userspace, before the signal mask is restored.
2081 : : */
2082 : : if (sigmask) {
2083 : : if (err == -EINTR) {
2084 : : memcpy(¤t->saved_sigmask, &sigsaved,
2085 : : sizeof(sigsaved));
2086 : : set_restore_sigmask();
2087 : : } else
2088 : : set_current_blocked(&sigsaved);
2089 : : }
2090 : :
2091 : : return err;
2092 : : }
2093 : : #endif
2094 : :
2095 : 0 : static int __init eventpoll_init(void)
2096 : : {
2097 : : struct sysinfo si;
2098 : :
2099 : 0 : si_meminfo(&si);
2100 : : /*
2101 : : * Allows top 4% of lomem to be allocated for epoll watches (per user).
2102 : : */
2103 : 0 : max_user_watches = (((si.totalram - si.totalhigh) / 25) << PAGE_SHIFT) /
2104 : : EP_ITEM_COST;
2105 [ # # ]: 0 : BUG_ON(max_user_watches < 0);
2106 : :
2107 : : /*
2108 : : * Initialize the structure used to perform epoll file descriptor
2109 : : * inclusion loops checks.
2110 : : */
2111 : : ep_nested_calls_init(&poll_loop_ncalls);
2112 : :
2113 : : /* Initialize the structure used to perform safe poll wait head wake ups */
2114 : : ep_nested_calls_init(&poll_safewake_ncalls);
2115 : :
2116 : : /* Initialize the structure used to perform file's f_op->poll() calls */
2117 : : ep_nested_calls_init(&poll_readywalk_ncalls);
2118 : :
2119 : : /*
2120 : : * We can have many thousands of epitems, so prevent this from
2121 : : * using an extra cache line on 64-bit (and smaller) CPUs
2122 : : */
2123 : : BUILD_BUG_ON(sizeof(void *) <= 8 && sizeof(struct epitem) > 128);
2124 : :
2125 : : /* Allocates slab cache used to allocate "struct epitem" items */
2126 : 0 : epi_cache = kmem_cache_create("eventpoll_epi", sizeof(struct epitem),
2127 : : 0, SLAB_HWCACHE_ALIGN | SLAB_PANIC, NULL);
2128 : :
2129 : : /* Allocates slab cache used to allocate "struct eppoll_entry" */
2130 : 0 : pwq_cache = kmem_cache_create("eventpoll_pwq",
2131 : : sizeof(struct eppoll_entry), 0, SLAB_PANIC, NULL);
2132 : :
2133 : 0 : return 0;
2134 : : }
2135 : : fs_initcall(eventpoll_init);
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