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1 | /* |
2 | * linux/ipc/sem.c |
3 | * Copyright (C) 1992 Krishna Balasubramanian |
4 | * Copyright (C) 1995 Eric Schenk, Bruno Haible |
5 | * |
6 | * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com> |
7 | * |
8 | * SMP-threaded, sysctl's added |
9 | * (c) 1999 Manfred Spraul <manfred@colorfullife.com> |
10 | * Enforced range limit on SEM_UNDO |
11 | * (c) 2001 Red Hat Inc |
12 | * Lockless wakeup |
13 | * (c) 2003 Manfred Spraul <manfred@colorfullife.com> |
14 | * Further wakeup optimizations, documentation |
15 | * (c) 2010 Manfred Spraul <manfred@colorfullife.com> |
16 | * |
17 | * support for audit of ipc object properties and permission changes |
18 | * Dustin Kirkland <dustin.kirkland@us.ibm.com> |
19 | * |
20 | * namespaces support |
21 | * OpenVZ, SWsoft Inc. |
22 | * Pavel Emelianov <xemul@openvz.org> |
23 | * |
24 | * Implementation notes: (May 2010) |
25 | * This file implements System V semaphores. |
26 | * |
27 | * User space visible behavior: |
28 | * - FIFO ordering for semop() operations (just FIFO, not starvation |
29 | * protection) |
30 | * - multiple semaphore operations that alter the same semaphore in |
31 | * one semop() are handled. |
32 | * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and |
33 | * SETALL calls. |
34 | * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO. |
35 | * - undo adjustments at process exit are limited to 0..SEMVMX. |
36 | * - namespace are supported. |
37 | * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing |
38 | * to /proc/sys/kernel/sem. |
39 | * - statistics about the usage are reported in /proc/sysvipc/sem. |
40 | * |
41 | * Internals: |
42 | * - scalability: |
43 | * - all global variables are read-mostly. |
44 | * - semop() calls and semctl(RMID) are synchronized by RCU. |
45 | * - most operations do write operations (actually: spin_lock calls) to |
46 | * the per-semaphore array structure. |
47 | * Thus: Perfect SMP scaling between independent semaphore arrays. |
48 | * If multiple semaphores in one array are used, then cache line |
49 | * trashing on the semaphore array spinlock will limit the scaling. |
50 | * - semncnt and semzcnt are calculated on demand in count_semncnt() and |
51 | * count_semzcnt() |
52 | * - the task that performs a successful semop() scans the list of all |
53 | * sleeping tasks and completes any pending operations that can be fulfilled. |
54 | * Semaphores are actively given to waiting tasks (necessary for FIFO). |
55 | * (see update_queue()) |
56 | * - To improve the scalability, the actual wake-up calls are performed after |
57 | * dropping all locks. (see wake_up_sem_queue_prepare(), |
58 | * wake_up_sem_queue_do()) |
59 | * - All work is done by the waker, the woken up task does not have to do |
60 | * anything - not even acquiring a lock or dropping a refcount. |
61 | * - A woken up task may not even touch the semaphore array anymore, it may |
62 | * have been destroyed already by a semctl(RMID). |
63 | * - The synchronizations between wake-ups due to a timeout/signal and a |
64 | * wake-up due to a completed semaphore operation is achieved by using an |
65 | * intermediate state (IN_WAKEUP). |
66 | * - UNDO values are stored in an array (one per process and per |
67 | * semaphore array, lazily allocated). For backwards compatibility, multiple |
68 | * modes for the UNDO variables are supported (per process, per thread) |
69 | * (see copy_semundo, CLONE_SYSVSEM) |
70 | * - There are two lists of the pending operations: a per-array list |
71 | * and per-semaphore list (stored in the array). This allows to achieve FIFO |
72 | * ordering without always scanning all pending operations. |
73 | * The worst-case behavior is nevertheless O(N^2) for N wakeups. |
74 | */ |
75 | |
76 | #include <linux/slab.h> |
77 | #include <linux/spinlock.h> |
78 | #include <linux/init.h> |
79 | #include <linux/proc_fs.h> |
80 | #include <linux/time.h> |
81 | #include <linux/security.h> |
82 | #include <linux/syscalls.h> |
83 | #include <linux/audit.h> |
84 | #include <linux/capability.h> |
85 | #include <linux/seq_file.h> |
86 | #include <linux/rwsem.h> |
87 | #include <linux/nsproxy.h> |
88 | #include <linux/ipc_namespace.h> |
89 | |
90 | #include <asm/uaccess.h> |
91 | #include "util.h" |
92 | |
93 | /* One semaphore structure for each semaphore in the system. */ |
94 | struct sem { |
95 | int semval; /* current value */ |
96 | int sempid; /* pid of last operation */ |
97 | spinlock_t lock; /* spinlock for fine-grained semtimedop */ |
98 | struct list_head pending_alter; /* pending single-sop operations */ |
99 | /* that alter the semaphore */ |
100 | struct list_head pending_const; /* pending single-sop operations */ |
101 | /* that do not alter the semaphore*/ |
102 | time_t sem_otime; /* candidate for sem_otime */ |
103 | } ____cacheline_aligned_in_smp; |
104 | |
105 | /* One queue for each sleeping process in the system. */ |
106 | struct sem_queue { |
107 | struct list_head list; /* queue of pending operations */ |
108 | struct task_struct *sleeper; /* this process */ |
109 | struct sem_undo *undo; /* undo structure */ |
110 | int pid; /* process id of requesting process */ |
111 | int status; /* completion status of operation */ |
112 | struct sembuf *sops; /* array of pending operations */ |
113 | int nsops; /* number of operations */ |
114 | int alter; /* does *sops alter the array? */ |
115 | }; |
116 | |
117 | /* Each task has a list of undo requests. They are executed automatically |
118 | * when the process exits. |
119 | */ |
120 | struct sem_undo { |
121 | struct list_head list_proc; /* per-process list: * |
122 | * all undos from one process |
123 | * rcu protected */ |
124 | struct rcu_head rcu; /* rcu struct for sem_undo */ |
125 | struct sem_undo_list *ulp; /* back ptr to sem_undo_list */ |
126 | struct list_head list_id; /* per semaphore array list: |
127 | * all undos for one array */ |
128 | int semid; /* semaphore set identifier */ |
129 | short *semadj; /* array of adjustments */ |
130 | /* one per semaphore */ |
131 | }; |
132 | |
133 | /* sem_undo_list controls shared access to the list of sem_undo structures |
134 | * that may be shared among all a CLONE_SYSVSEM task group. |
135 | */ |
136 | struct sem_undo_list { |
137 | atomic_t refcnt; |
138 | spinlock_t lock; |
139 | struct list_head list_proc; |
140 | }; |
141 | |
142 | |
143 | #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS]) |
144 | |
145 | #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid) |
146 | |
147 | static int newary(struct ipc_namespace *, struct ipc_params *); |
148 | static void freeary(struct ipc_namespace *, struct kern_ipc_perm *); |
149 | #ifdef CONFIG_PROC_FS |
150 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it); |
151 | #endif |
152 | |
153 | #define SEMMSL_FAST 256 /* 512 bytes on stack */ |
154 | #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ |
155 | |
156 | /* |
157 | * Locking: |
158 | * sem_undo.id_next, |
159 | * sem_array.complex_count, |
160 | * sem_array.pending{_alter,_cont}, |
161 | * sem_array.sem_undo: global sem_lock() for read/write |
162 | * sem_undo.proc_next: only "current" is allowed to read/write that field. |
163 | * |
164 | * sem_array.sem_base[i].pending_{const,alter}: |
165 | * global or semaphore sem_lock() for read/write |
166 | */ |
167 | |
168 | #define sc_semmsl sem_ctls[0] |
169 | #define sc_semmns sem_ctls[1] |
170 | #define sc_semopm sem_ctls[2] |
171 | #define sc_semmni sem_ctls[3] |
172 | |
173 | void sem_init_ns(struct ipc_namespace *ns) |
174 | { |
175 | ns->sc_semmsl = SEMMSL; |
176 | ns->sc_semmns = SEMMNS; |
177 | ns->sc_semopm = SEMOPM; |
178 | ns->sc_semmni = SEMMNI; |
179 | ns->used_sems = 0; |
180 | ipc_init_ids(&ns->ids[IPC_SEM_IDS]); |
181 | } |
182 | |
183 | #ifdef CONFIG_IPC_NS |
184 | void sem_exit_ns(struct ipc_namespace *ns) |
185 | { |
186 | free_ipcs(ns, &sem_ids(ns), freeary); |
187 | idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr); |
188 | } |
189 | #endif |
190 | |
191 | void __init sem_init (void) |
192 | { |
193 | sem_init_ns(&init_ipc_ns); |
194 | ipc_init_proc_interface("sysvipc/sem", |
195 | " key semid perms nsems uid gid cuid cgid otime ctime\n", |
196 | IPC_SEM_IDS, sysvipc_sem_proc_show); |
197 | } |
198 | |
199 | /** |
200 | * unmerge_queues - unmerge queues, if possible. |
201 | * @sma: semaphore array |
202 | * |
203 | * The function unmerges the wait queues if complex_count is 0. |
204 | * It must be called prior to dropping the global semaphore array lock. |
205 | */ |
206 | static void unmerge_queues(struct sem_array *sma) |
207 | { |
208 | struct sem_queue *q, *tq; |
209 | |
210 | /* complex operations still around? */ |
211 | if (sma->complex_count) |
212 | return; |
213 | /* |
214 | * We will switch back to simple mode. |
215 | * Move all pending operation back into the per-semaphore |
216 | * queues. |
217 | */ |
218 | list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { |
219 | struct sem *curr; |
220 | curr = &sma->sem_base[q->sops[0].sem_num]; |
221 | |
222 | list_add_tail(&q->list, &curr->pending_alter); |
223 | } |
224 | INIT_LIST_HEAD(&sma->pending_alter); |
225 | } |
226 | |
227 | /** |
228 | * merge_queues - Merge single semop queues into global queue |
229 | * @sma: semaphore array |
230 | * |
231 | * This function merges all per-semaphore queues into the global queue. |
232 | * It is necessary to achieve FIFO ordering for the pending single-sop |
233 | * operations when a multi-semop operation must sleep. |
234 | * Only the alter operations must be moved, the const operations can stay. |
235 | */ |
236 | static void merge_queues(struct sem_array *sma) |
237 | { |
238 | int i; |
239 | for (i = 0; i < sma->sem_nsems; i++) { |
240 | struct sem *sem = sma->sem_base + i; |
241 | |
242 | list_splice_init(&sem->pending_alter, &sma->pending_alter); |
243 | } |
244 | } |
245 | |
246 | static void sem_rcu_free(struct rcu_head *head) |
247 | { |
248 | struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu); |
249 | struct sem_array *sma = ipc_rcu_to_struct(p); |
250 | |
251 | security_sem_free(sma); |
252 | ipc_rcu_free(head); |
253 | } |
254 | |
255 | /* |
256 | * Wait until all currently ongoing simple ops have completed. |
257 | * Caller must own sem_perm.lock. |
258 | * New simple ops cannot start, because simple ops first check |
259 | * that sem_perm.lock is free. |
260 | * that a) sem_perm.lock is free and b) complex_count is 0. |
261 | */ |
262 | static void sem_wait_array(struct sem_array *sma) |
263 | { |
264 | int i; |
265 | struct sem *sem; |
266 | |
267 | if (sma->complex_count) { |
268 | /* The thread that increased sma->complex_count waited on |
269 | * all sem->lock locks. Thus we don't need to wait again. |
270 | */ |
271 | return; |
272 | } |
273 | |
274 | for (i = 0; i < sma->sem_nsems; i++) { |
275 | sem = sma->sem_base + i; |
276 | spin_unlock_wait(&sem->lock); |
277 | } |
278 | } |
279 | |
280 | /* |
281 | * If the request contains only one semaphore operation, and there are |
282 | * no complex transactions pending, lock only the semaphore involved. |
283 | * Otherwise, lock the entire semaphore array, since we either have |
284 | * multiple semaphores in our own semops, or we need to look at |
285 | * semaphores from other pending complex operations. |
286 | */ |
287 | static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, |
288 | int nsops) |
289 | { |
290 | struct sem *sem; |
291 | |
292 | if (nsops != 1) { |
293 | /* Complex operation - acquire a full lock */ |
294 | ipc_lock_object(&sma->sem_perm); |
295 | |
296 | /* And wait until all simple ops that are processed |
297 | * right now have dropped their locks. |
298 | */ |
299 | sem_wait_array(sma); |
300 | return -1; |
301 | } |
302 | |
303 | /* |
304 | * Only one semaphore affected - try to optimize locking. |
305 | * The rules are: |
306 | * - optimized locking is possible if no complex operation |
307 | * is either enqueued or processed right now. |
308 | * - The test for enqueued complex ops is simple: |
309 | * sma->complex_count != 0 |
310 | * - Testing for complex ops that are processed right now is |
311 | * a bit more difficult. Complex ops acquire the full lock |
312 | * and first wait that the running simple ops have completed. |
313 | * (see above) |
314 | * Thus: If we own a simple lock and the global lock is free |
315 | * and complex_count is now 0, then it will stay 0 and |
316 | * thus just locking sem->lock is sufficient. |
317 | */ |
318 | sem = sma->sem_base + sops->sem_num; |
319 | |
320 | if (sma->complex_count == 0) { |
321 | /* |
322 | * It appears that no complex operation is around. |
323 | * Acquire the per-semaphore lock. |
324 | */ |
325 | spin_lock(&sem->lock); |
326 | |
327 | /* Then check that the global lock is free */ |
328 | if (!spin_is_locked(&sma->sem_perm.lock)) { |
329 | /* spin_is_locked() is not a memory barrier */ |
330 | smp_mb(); |
331 | |
332 | /* Now repeat the test of complex_count: |
333 | * It can't change anymore until we drop sem->lock. |
334 | * Thus: if is now 0, then it will stay 0. |
335 | */ |
336 | if (sma->complex_count == 0) { |
337 | /* fast path successful! */ |
338 | return sops->sem_num; |
339 | } |
340 | } |
341 | spin_unlock(&sem->lock); |
342 | } |
343 | |
344 | /* slow path: acquire the full lock */ |
345 | ipc_lock_object(&sma->sem_perm); |
346 | |
347 | if (sma->complex_count == 0) { |
348 | /* False alarm: |
349 | * There is no complex operation, thus we can switch |
350 | * back to the fast path. |
351 | */ |
352 | spin_lock(&sem->lock); |
353 | ipc_unlock_object(&sma->sem_perm); |
354 | return sops->sem_num; |
355 | } else { |
356 | /* Not a false alarm, thus complete the sequence for a |
357 | * full lock. |
358 | */ |
359 | sem_wait_array(sma); |
360 | return -1; |
361 | } |
362 | } |
363 | |
364 | static inline void sem_unlock(struct sem_array *sma, int locknum) |
365 | { |
366 | if (locknum == -1) { |
367 | unmerge_queues(sma); |
368 | ipc_unlock_object(&sma->sem_perm); |
369 | } else { |
370 | struct sem *sem = sma->sem_base + locknum; |
371 | spin_unlock(&sem->lock); |
372 | } |
373 | } |
374 | |
375 | /* |
376 | * sem_lock_(check_) routines are called in the paths where the rwsem |
377 | * is not held. |
378 | * |
379 | * The caller holds the RCU read lock. |
380 | */ |
381 | static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns, |
382 | int id, struct sembuf *sops, int nsops, int *locknum) |
383 | { |
384 | struct kern_ipc_perm *ipcp; |
385 | struct sem_array *sma; |
386 | |
387 | ipcp = ipc_obtain_object(&sem_ids(ns), id); |
388 | if (IS_ERR(ipcp)) |
389 | return ERR_CAST(ipcp); |
390 | |
391 | sma = container_of(ipcp, struct sem_array, sem_perm); |
392 | *locknum = sem_lock(sma, sops, nsops); |
393 | |
394 | /* ipc_rmid() may have already freed the ID while sem_lock |
395 | * was spinning: verify that the structure is still valid |
396 | */ |
397 | if (!ipcp->deleted) |
398 | return container_of(ipcp, struct sem_array, sem_perm); |
399 | |
400 | sem_unlock(sma, *locknum); |
401 | return ERR_PTR(-EINVAL); |
402 | } |
403 | |
404 | static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) |
405 | { |
406 | struct kern_ipc_perm *ipcp = ipc_obtain_object(&sem_ids(ns), id); |
407 | |
408 | if (IS_ERR(ipcp)) |
409 | return ERR_CAST(ipcp); |
410 | |
411 | return container_of(ipcp, struct sem_array, sem_perm); |
412 | } |
413 | |
414 | static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns, |
415 | int id) |
416 | { |
417 | struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id); |
418 | |
419 | if (IS_ERR(ipcp)) |
420 | return ERR_CAST(ipcp); |
421 | |
422 | return container_of(ipcp, struct sem_array, sem_perm); |
423 | } |
424 | |
425 | static inline void sem_lock_and_putref(struct sem_array *sma) |
426 | { |
427 | sem_lock(sma, NULL, -1); |
428 | ipc_rcu_putref(sma, ipc_rcu_free); |
429 | } |
430 | |
431 | static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) |
432 | { |
433 | ipc_rmid(&sem_ids(ns), &s->sem_perm); |
434 | } |
435 | |
436 | /* |
437 | * Lockless wakeup algorithm: |
438 | * Without the check/retry algorithm a lockless wakeup is possible: |
439 | * - queue.status is initialized to -EINTR before blocking. |
440 | * - wakeup is performed by |
441 | * * unlinking the queue entry from the pending list |
442 | * * setting queue.status to IN_WAKEUP |
443 | * This is the notification for the blocked thread that a |
444 | * result value is imminent. |
445 | * * call wake_up_process |
446 | * * set queue.status to the final value. |
447 | * - the previously blocked thread checks queue.status: |
448 | * * if it's IN_WAKEUP, then it must wait until the value changes |
449 | * * if it's not -EINTR, then the operation was completed by |
450 | * update_queue. semtimedop can return queue.status without |
451 | * performing any operation on the sem array. |
452 | * * otherwise it must acquire the spinlock and check what's up. |
453 | * |
454 | * The two-stage algorithm is necessary to protect against the following |
455 | * races: |
456 | * - if queue.status is set after wake_up_process, then the woken up idle |
457 | * thread could race forward and try (and fail) to acquire sma->lock |
458 | * before update_queue had a chance to set queue.status |
459 | * - if queue.status is written before wake_up_process and if the |
460 | * blocked process is woken up by a signal between writing |
461 | * queue.status and the wake_up_process, then the woken up |
462 | * process could return from semtimedop and die by calling |
463 | * sys_exit before wake_up_process is called. Then wake_up_process |
464 | * will oops, because the task structure is already invalid. |
465 | * (yes, this happened on s390 with sysv msg). |
466 | * |
467 | */ |
468 | #define IN_WAKEUP 1 |
469 | |
470 | /** |
471 | * newary - Create a new semaphore set |
472 | * @ns: namespace |
473 | * @params: ptr to the structure that contains key, semflg and nsems |
474 | * |
475 | * Called with sem_ids.rwsem held (as a writer) |
476 | */ |
477 | |
478 | static int newary(struct ipc_namespace *ns, struct ipc_params *params) |
479 | { |
480 | int id; |
481 | int retval; |
482 | struct sem_array *sma; |
483 | int size; |
484 | key_t key = params->key; |
485 | int nsems = params->u.nsems; |
486 | int semflg = params->flg; |
487 | int i; |
488 | |
489 | if (!nsems) |
490 | return -EINVAL; |
491 | if (ns->used_sems + nsems > ns->sc_semmns) |
492 | return -ENOSPC; |
493 | |
494 | size = sizeof (*sma) + nsems * sizeof (struct sem); |
495 | sma = ipc_rcu_alloc(size); |
496 | if (!sma) { |
497 | return -ENOMEM; |
498 | } |
499 | memset (sma, 0, size); |
500 | |
501 | sma->sem_perm.mode = (semflg & S_IRWXUGO); |
502 | sma->sem_perm.key = key; |
503 | |
504 | sma->sem_perm.security = NULL; |
505 | retval = security_sem_alloc(sma); |
506 | if (retval) { |
507 | ipc_rcu_putref(sma, ipc_rcu_free); |
508 | return retval; |
509 | } |
510 | |
511 | id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); |
512 | if (id < 0) { |
513 | ipc_rcu_putref(sma, sem_rcu_free); |
514 | return id; |
515 | } |
516 | ns->used_sems += nsems; |
517 | |
518 | sma->sem_base = (struct sem *) &sma[1]; |
519 | |
520 | for (i = 0; i < nsems; i++) { |
521 | INIT_LIST_HEAD(&sma->sem_base[i].pending_alter); |
522 | INIT_LIST_HEAD(&sma->sem_base[i].pending_const); |
523 | spin_lock_init(&sma->sem_base[i].lock); |
524 | } |
525 | |
526 | sma->complex_count = 0; |
527 | INIT_LIST_HEAD(&sma->pending_alter); |
528 | INIT_LIST_HEAD(&sma->pending_const); |
529 | INIT_LIST_HEAD(&sma->list_id); |
530 | sma->sem_nsems = nsems; |
531 | sma->sem_ctime = get_seconds(); |
532 | sem_unlock(sma, -1); |
533 | rcu_read_unlock(); |
534 | |
535 | return sma->sem_perm.id; |
536 | } |
537 | |
538 | |
539 | /* |
540 | * Called with sem_ids.rwsem and ipcp locked. |
541 | */ |
542 | static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg) |
543 | { |
544 | struct sem_array *sma; |
545 | |
546 | sma = container_of(ipcp, struct sem_array, sem_perm); |
547 | return security_sem_associate(sma, semflg); |
548 | } |
549 | |
550 | /* |
551 | * Called with sem_ids.rwsem and ipcp locked. |
552 | */ |
553 | static inline int sem_more_checks(struct kern_ipc_perm *ipcp, |
554 | struct ipc_params *params) |
555 | { |
556 | struct sem_array *sma; |
557 | |
558 | sma = container_of(ipcp, struct sem_array, sem_perm); |
559 | if (params->u.nsems > sma->sem_nsems) |
560 | return -EINVAL; |
561 | |
562 | return 0; |
563 | } |
564 | |
565 | SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) |
566 | { |
567 | struct ipc_namespace *ns; |
568 | struct ipc_ops sem_ops; |
569 | struct ipc_params sem_params; |
570 | |
571 | ns = current->nsproxy->ipc_ns; |
572 | |
573 | if (nsems < 0 || nsems > ns->sc_semmsl) |
574 | return -EINVAL; |
575 | |
576 | sem_ops.getnew = newary; |
577 | sem_ops.associate = sem_security; |
578 | sem_ops.more_checks = sem_more_checks; |
579 | |
580 | sem_params.key = key; |
581 | sem_params.flg = semflg; |
582 | sem_params.u.nsems = nsems; |
583 | |
584 | return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); |
585 | } |
586 | |
587 | /** perform_atomic_semop - Perform (if possible) a semaphore operation |
588 | * @sma: semaphore array |
589 | * @sops: array with operations that should be checked |
590 | * @nsems: number of sops |
591 | * @un: undo array |
592 | * @pid: pid that did the change |
593 | * |
594 | * Returns 0 if the operation was possible. |
595 | * Returns 1 if the operation is impossible, the caller must sleep. |
596 | * Negative values are error codes. |
597 | */ |
598 | |
599 | static int perform_atomic_semop(struct sem_array *sma, struct sembuf *sops, |
600 | int nsops, struct sem_undo *un, int pid) |
601 | { |
602 | int result, sem_op; |
603 | struct sembuf *sop; |
604 | struct sem * curr; |
605 | |
606 | for (sop = sops; sop < sops + nsops; sop++) { |
607 | curr = sma->sem_base + sop->sem_num; |
608 | sem_op = sop->sem_op; |
609 | result = curr->semval; |
610 | |
611 | if (!sem_op && result) |
612 | goto would_block; |
613 | |
614 | result += sem_op; |
615 | if (result < 0) |
616 | goto would_block; |
617 | if (result > SEMVMX) |
618 | goto out_of_range; |
619 | if (sop->sem_flg & SEM_UNDO) { |
620 | int undo = un->semadj[sop->sem_num] - sem_op; |
621 | /* |
622 | * Exceeding the undo range is an error. |
623 | */ |
624 | if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
625 | goto out_of_range; |
626 | } |
627 | curr->semval = result; |
628 | } |
629 | |
630 | sop--; |
631 | while (sop >= sops) { |
632 | sma->sem_base[sop->sem_num].sempid = pid; |
633 | if (sop->sem_flg & SEM_UNDO) |
634 | un->semadj[sop->sem_num] -= sop->sem_op; |
635 | sop--; |
636 | } |
637 | |
638 | return 0; |
639 | |
640 | out_of_range: |
641 | result = -ERANGE; |
642 | goto undo; |
643 | |
644 | would_block: |
645 | if (sop->sem_flg & IPC_NOWAIT) |
646 | result = -EAGAIN; |
647 | else |
648 | result = 1; |
649 | |
650 | undo: |
651 | sop--; |
652 | while (sop >= sops) { |
653 | sma->sem_base[sop->sem_num].semval -= sop->sem_op; |
654 | sop--; |
655 | } |
656 | |
657 | return result; |
658 | } |
659 | |
660 | /** wake_up_sem_queue_prepare(q, error): Prepare wake-up |
661 | * @q: queue entry that must be signaled |
662 | * @error: Error value for the signal |
663 | * |
664 | * Prepare the wake-up of the queue entry q. |
665 | */ |
666 | static void wake_up_sem_queue_prepare(struct list_head *pt, |
667 | struct sem_queue *q, int error) |
668 | { |
669 | if (list_empty(pt)) { |
670 | /* |
671 | * Hold preempt off so that we don't get preempted and have the |
672 | * wakee busy-wait until we're scheduled back on. |
673 | */ |
674 | preempt_disable(); |
675 | } |
676 | q->status = IN_WAKEUP; |
677 | q->pid = error; |
678 | |
679 | list_add_tail(&q->list, pt); |
680 | } |
681 | |
682 | /** |
683 | * wake_up_sem_queue_do(pt) - do the actual wake-up |
684 | * @pt: list of tasks to be woken up |
685 | * |
686 | * Do the actual wake-up. |
687 | * The function is called without any locks held, thus the semaphore array |
688 | * could be destroyed already and the tasks can disappear as soon as the |
689 | * status is set to the actual return code. |
690 | */ |
691 | static void wake_up_sem_queue_do(struct list_head *pt) |
692 | { |
693 | struct sem_queue *q, *t; |
694 | int did_something; |
695 | |
696 | did_something = !list_empty(pt); |
697 | list_for_each_entry_safe(q, t, pt, list) { |
698 | wake_up_process(q->sleeper); |
699 | /* q can disappear immediately after writing q->status. */ |
700 | smp_wmb(); |
701 | q->status = q->pid; |
702 | } |
703 | if (did_something) |
704 | preempt_enable(); |
705 | } |
706 | |
707 | static void unlink_queue(struct sem_array *sma, struct sem_queue *q) |
708 | { |
709 | list_del(&q->list); |
710 | if (q->nsops > 1) |
711 | sma->complex_count--; |
712 | } |
713 | |
714 | /** check_restart(sma, q) |
715 | * @sma: semaphore array |
716 | * @q: the operation that just completed |
717 | * |
718 | * update_queue is O(N^2) when it restarts scanning the whole queue of |
719 | * waiting operations. Therefore this function checks if the restart is |
720 | * really necessary. It is called after a previously waiting operation |
721 | * modified the array. |
722 | * Note that wait-for-zero operations are handled without restart. |
723 | */ |
724 | static int check_restart(struct sem_array *sma, struct sem_queue *q) |
725 | { |
726 | /* pending complex alter operations are too difficult to analyse */ |
727 | if (!list_empty(&sma->pending_alter)) |
728 | return 1; |
729 | |
730 | /* we were a sleeping complex operation. Too difficult */ |
731 | if (q->nsops > 1) |
732 | return 1; |
733 | |
734 | /* It is impossible that someone waits for the new value: |
735 | * - complex operations always restart. |
736 | * - wait-for-zero are handled seperately. |
737 | * - q is a previously sleeping simple operation that |
738 | * altered the array. It must be a decrement, because |
739 | * simple increments never sleep. |
740 | * - If there are older (higher priority) decrements |
741 | * in the queue, then they have observed the original |
742 | * semval value and couldn't proceed. The operation |
743 | * decremented to value - thus they won't proceed either. |
744 | */ |
745 | return 0; |
746 | } |
747 | |
748 | /** |
749 | * wake_const_ops(sma, semnum, pt) - Wake up non-alter tasks |
750 | * @sma: semaphore array. |
751 | * @semnum: semaphore that was modified. |
752 | * @pt: list head for the tasks that must be woken up. |
753 | * |
754 | * wake_const_ops must be called after a semaphore in a semaphore array |
755 | * was set to 0. If complex const operations are pending, wake_const_ops must |
756 | * be called with semnum = -1, as well as with the number of each modified |
757 | * semaphore. |
758 | * The tasks that must be woken up are added to @pt. The return code |
759 | * is stored in q->pid. |
760 | * The function returns 1 if at least one operation was completed successfully. |
761 | */ |
762 | static int wake_const_ops(struct sem_array *sma, int semnum, |
763 | struct list_head *pt) |
764 | { |
765 | struct sem_queue *q; |
766 | struct list_head *walk; |
767 | struct list_head *pending_list; |
768 | int semop_completed = 0; |
769 | |
770 | if (semnum == -1) |
771 | pending_list = &sma->pending_const; |
772 | else |
773 | pending_list = &sma->sem_base[semnum].pending_const; |
774 | |
775 | walk = pending_list->next; |
776 | while (walk != pending_list) { |
777 | int error; |
778 | |
779 | q = container_of(walk, struct sem_queue, list); |
780 | walk = walk->next; |
781 | |
782 | error = perform_atomic_semop(sma, q->sops, q->nsops, |
783 | q->undo, q->pid); |
784 | |
785 | if (error <= 0) { |
786 | /* operation completed, remove from queue & wakeup */ |
787 | |
788 | unlink_queue(sma, q); |
789 | |
790 | wake_up_sem_queue_prepare(pt, q, error); |
791 | if (error == 0) |
792 | semop_completed = 1; |
793 | } |
794 | } |
795 | return semop_completed; |
796 | } |
797 | |
798 | /** |
799 | * do_smart_wakeup_zero(sma, sops, nsops, pt) - wakeup all wait for zero tasks |
800 | * @sma: semaphore array |
801 | * @sops: operations that were performed |
802 | * @nsops: number of operations |
803 | * @pt: list head of the tasks that must be woken up. |
804 | * |
805 | * do_smart_wakeup_zero() checks all required queue for wait-for-zero |
806 | * operations, based on the actual changes that were performed on the |
807 | * semaphore array. |
808 | * The function returns 1 if at least one operation was completed successfully. |
809 | */ |
810 | static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops, |
811 | int nsops, struct list_head *pt) |
812 | { |
813 | int i; |
814 | int semop_completed = 0; |
815 | int got_zero = 0; |
816 | |
817 | /* first: the per-semaphore queues, if known */ |
818 | if (sops) { |
819 | for (i = 0; i < nsops; i++) { |
820 | int num = sops[i].sem_num; |
821 | |
822 | if (sma->sem_base[num].semval == 0) { |
823 | got_zero = 1; |
824 | semop_completed |= wake_const_ops(sma, num, pt); |
825 | } |
826 | } |
827 | } else { |
828 | /* |
829 | * No sops means modified semaphores not known. |
830 | * Assume all were changed. |
831 | */ |
832 | for (i = 0; i < sma->sem_nsems; i++) { |
833 | if (sma->sem_base[i].semval == 0) { |
834 | got_zero = 1; |
835 | semop_completed |= wake_const_ops(sma, i, pt); |
836 | } |
837 | } |
838 | } |
839 | /* |
840 | * If one of the modified semaphores got 0, |
841 | * then check the global queue, too. |
842 | */ |
843 | if (got_zero) |
844 | semop_completed |= wake_const_ops(sma, -1, pt); |
845 | |
846 | return semop_completed; |
847 | } |
848 | |
849 | |
850 | /** |
851 | * update_queue(sma, semnum): Look for tasks that can be completed. |
852 | * @sma: semaphore array. |
853 | * @semnum: semaphore that was modified. |
854 | * @pt: list head for the tasks that must be woken up. |
855 | * |
856 | * update_queue must be called after a semaphore in a semaphore array |
857 | * was modified. If multiple semaphores were modified, update_queue must |
858 | * be called with semnum = -1, as well as with the number of each modified |
859 | * semaphore. |
860 | * The tasks that must be woken up are added to @pt. The return code |
861 | * is stored in q->pid. |
862 | * The function internally checks if const operations can now succeed. |
863 | * |
864 | * The function return 1 if at least one semop was completed successfully. |
865 | */ |
866 | static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt) |
867 | { |
868 | struct sem_queue *q; |
869 | struct list_head *walk; |
870 | struct list_head *pending_list; |
871 | int semop_completed = 0; |
872 | |
873 | if (semnum == -1) |
874 | pending_list = &sma->pending_alter; |
875 | else |
876 | pending_list = &sma->sem_base[semnum].pending_alter; |
877 | |
878 | again: |
879 | walk = pending_list->next; |
880 | while (walk != pending_list) { |
881 | int error, restart; |
882 | |
883 | q = container_of(walk, struct sem_queue, list); |
884 | walk = walk->next; |
885 | |
886 | /* If we are scanning the single sop, per-semaphore list of |
887 | * one semaphore and that semaphore is 0, then it is not |
888 | * necessary to scan further: simple increments |
889 | * that affect only one entry succeed immediately and cannot |
890 | * be in the per semaphore pending queue, and decrements |
891 | * cannot be successful if the value is already 0. |
892 | */ |
893 | if (semnum != -1 && sma->sem_base[semnum].semval == 0) |
894 | break; |
895 | |
896 | error = perform_atomic_semop(sma, q->sops, q->nsops, |
897 | q->undo, q->pid); |
898 | |
899 | /* Does q->sleeper still need to sleep? */ |
900 | if (error > 0) |
901 | continue; |
902 | |
903 | unlink_queue(sma, q); |
904 | |
905 | if (error) { |
906 | restart = 0; |
907 | } else { |
908 | semop_completed = 1; |
909 | do_smart_wakeup_zero(sma, q->sops, q->nsops, pt); |
910 | restart = check_restart(sma, q); |
911 | } |
912 | |
913 | wake_up_sem_queue_prepare(pt, q, error); |
914 | if (restart) |
915 | goto again; |
916 | } |
917 | return semop_completed; |
918 | } |
919 | |
920 | /** |
921 | * set_semotime(sma, sops) - set sem_otime |
922 | * @sma: semaphore array |
923 | * @sops: operations that modified the array, may be NULL |
924 | * |
925 | * sem_otime is replicated to avoid cache line trashing. |
926 | * This function sets one instance to the current time. |
927 | */ |
928 | static void set_semotime(struct sem_array *sma, struct sembuf *sops) |
929 | { |
930 | if (sops == NULL) { |
931 | sma->sem_base[0].sem_otime = get_seconds(); |
932 | } else { |
933 | sma->sem_base[sops[0].sem_num].sem_otime = |
934 | get_seconds(); |
935 | } |
936 | } |
937 | |
938 | /** |
939 | * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue |
940 | * @sma: semaphore array |
941 | * @sops: operations that were performed |
942 | * @nsops: number of operations |
943 | * @otime: force setting otime |
944 | * @pt: list head of the tasks that must be woken up. |
945 | * |
946 | * do_smart_update() does the required calls to update_queue and wakeup_zero, |
947 | * based on the actual changes that were performed on the semaphore array. |
948 | * Note that the function does not do the actual wake-up: the caller is |
949 | * responsible for calling wake_up_sem_queue_do(@pt). |
950 | * It is safe to perform this call after dropping all locks. |
951 | */ |
952 | static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops, |
953 | int otime, struct list_head *pt) |
954 | { |
955 | int i; |
956 | |
957 | otime |= do_smart_wakeup_zero(sma, sops, nsops, pt); |
958 | |
959 | if (!list_empty(&sma->pending_alter)) { |
960 | /* semaphore array uses the global queue - just process it. */ |
961 | otime |= update_queue(sma, -1, pt); |
962 | } else { |
963 | if (!sops) { |
964 | /* |
965 | * No sops, thus the modified semaphores are not |
966 | * known. Check all. |
967 | */ |
968 | for (i = 0; i < sma->sem_nsems; i++) |
969 | otime |= update_queue(sma, i, pt); |
970 | } else { |
971 | /* |
972 | * Check the semaphores that were increased: |
973 | * - No complex ops, thus all sleeping ops are |
974 | * decrease. |
975 | * - if we decreased the value, then any sleeping |
976 | * semaphore ops wont be able to run: If the |
977 | * previous value was too small, then the new |
978 | * value will be too small, too. |
979 | */ |
980 | for (i = 0; i < nsops; i++) { |
981 | if (sops[i].sem_op > 0) { |
982 | otime |= update_queue(sma, |
983 | sops[i].sem_num, pt); |
984 | } |
985 | } |
986 | } |
987 | } |
988 | if (otime) |
989 | set_semotime(sma, sops); |
990 | } |
991 | |
992 | /* The following counts are associated to each semaphore: |
993 | * semncnt number of tasks waiting on semval being nonzero |
994 | * semzcnt number of tasks waiting on semval being zero |
995 | * This model assumes that a task waits on exactly one semaphore. |
996 | * Since semaphore operations are to be performed atomically, tasks actually |
997 | * wait on a whole sequence of semaphores simultaneously. |
998 | * The counts we return here are a rough approximation, but still |
999 | * warrant that semncnt+semzcnt>0 if the task is on the pending queue. |
1000 | */ |
1001 | static int count_semncnt (struct sem_array * sma, ushort semnum) |
1002 | { |
1003 | int semncnt; |
1004 | struct sem_queue * q; |
1005 | |
1006 | semncnt = 0; |
1007 | list_for_each_entry(q, &sma->sem_base[semnum].pending_alter, list) { |
1008 | struct sembuf * sops = q->sops; |
1009 | BUG_ON(sops->sem_num != semnum); |
1010 | if ((sops->sem_op < 0) && !(sops->sem_flg & IPC_NOWAIT)) |
1011 | semncnt++; |
1012 | } |
1013 | |
1014 | list_for_each_entry(q, &sma->pending_alter, list) { |
1015 | struct sembuf * sops = q->sops; |
1016 | int nsops = q->nsops; |
1017 | int i; |
1018 | for (i = 0; i < nsops; i++) |
1019 | if (sops[i].sem_num == semnum |
1020 | && (sops[i].sem_op < 0) |
1021 | && !(sops[i].sem_flg & IPC_NOWAIT)) |
1022 | semncnt++; |
1023 | } |
1024 | return semncnt; |
1025 | } |
1026 | |
1027 | static int count_semzcnt (struct sem_array * sma, ushort semnum) |
1028 | { |
1029 | int semzcnt; |
1030 | struct sem_queue * q; |
1031 | |
1032 | semzcnt = 0; |
1033 | list_for_each_entry(q, &sma->sem_base[semnum].pending_const, list) { |
1034 | struct sembuf * sops = q->sops; |
1035 | BUG_ON(sops->sem_num != semnum); |
1036 | if ((sops->sem_op == 0) && !(sops->sem_flg & IPC_NOWAIT)) |
1037 | semzcnt++; |
1038 | } |
1039 | |
1040 | list_for_each_entry(q, &sma->pending_const, list) { |
1041 | struct sembuf * sops = q->sops; |
1042 | int nsops = q->nsops; |
1043 | int i; |
1044 | for (i = 0; i < nsops; i++) |
1045 | if (sops[i].sem_num == semnum |
1046 | && (sops[i].sem_op == 0) |
1047 | && !(sops[i].sem_flg & IPC_NOWAIT)) |
1048 | semzcnt++; |
1049 | } |
1050 | return semzcnt; |
1051 | } |
1052 | |
1053 | /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked |
1054 | * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem |
1055 | * remains locked on exit. |
1056 | */ |
1057 | static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) |
1058 | { |
1059 | struct sem_undo *un, *tu; |
1060 | struct sem_queue *q, *tq; |
1061 | struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
1062 | struct list_head tasks; |
1063 | int i; |
1064 | |
1065 | /* Free the existing undo structures for this semaphore set. */ |
1066 | ipc_assert_locked_object(&sma->sem_perm); |
1067 | list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { |
1068 | list_del(&un->list_id); |
1069 | spin_lock(&un->ulp->lock); |
1070 | un->semid = -1; |
1071 | list_del_rcu(&un->list_proc); |
1072 | spin_unlock(&un->ulp->lock); |
1073 | kfree_rcu(un, rcu); |
1074 | } |
1075 | |
1076 | /* Wake up all pending processes and let them fail with EIDRM. */ |
1077 | INIT_LIST_HEAD(&tasks); |
1078 | list_for_each_entry_safe(q, tq, &sma->pending_const, list) { |
1079 | unlink_queue(sma, q); |
1080 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); |
1081 | } |
1082 | |
1083 | list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { |
1084 | unlink_queue(sma, q); |
1085 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); |
1086 | } |
1087 | for (i = 0; i < sma->sem_nsems; i++) { |
1088 | struct sem *sem = sma->sem_base + i; |
1089 | list_for_each_entry_safe(q, tq, &sem->pending_const, list) { |
1090 | unlink_queue(sma, q); |
1091 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); |
1092 | } |
1093 | list_for_each_entry_safe(q, tq, &sem->pending_alter, list) { |
1094 | unlink_queue(sma, q); |
1095 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); |
1096 | } |
1097 | } |
1098 | |
1099 | /* Remove the semaphore set from the IDR */ |
1100 | sem_rmid(ns, sma); |
1101 | sem_unlock(sma, -1); |
1102 | rcu_read_unlock(); |
1103 | |
1104 | wake_up_sem_queue_do(&tasks); |
1105 | ns->used_sems -= sma->sem_nsems; |
1106 | ipc_rcu_putref(sma, sem_rcu_free); |
1107 | } |
1108 | |
1109 | static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) |
1110 | { |
1111 | switch(version) { |
1112 | case IPC_64: |
1113 | return copy_to_user(buf, in, sizeof(*in)); |
1114 | case IPC_OLD: |
1115 | { |
1116 | struct semid_ds out; |
1117 | |
1118 | memset(&out, 0, sizeof(out)); |
1119 | |
1120 | ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); |
1121 | |
1122 | out.sem_otime = in->sem_otime; |
1123 | out.sem_ctime = in->sem_ctime; |
1124 | out.sem_nsems = in->sem_nsems; |
1125 | |
1126 | return copy_to_user(buf, &out, sizeof(out)); |
1127 | } |
1128 | default: |
1129 | return -EINVAL; |
1130 | } |
1131 | } |
1132 | |
1133 | static time_t get_semotime(struct sem_array *sma) |
1134 | { |
1135 | int i; |
1136 | time_t res; |
1137 | |
1138 | res = sma->sem_base[0].sem_otime; |
1139 | for (i = 1; i < sma->sem_nsems; i++) { |
1140 | time_t to = sma->sem_base[i].sem_otime; |
1141 | |
1142 | if (to > res) |
1143 | res = to; |
1144 | } |
1145 | return res; |
1146 | } |
1147 | |
1148 | static int semctl_nolock(struct ipc_namespace *ns, int semid, |
1149 | int cmd, int version, void __user *p) |
1150 | { |
1151 | int err; |
1152 | struct sem_array *sma; |
1153 | |
1154 | switch(cmd) { |
1155 | case IPC_INFO: |
1156 | case SEM_INFO: |
1157 | { |
1158 | struct seminfo seminfo; |
1159 | int max_id; |
1160 | |
1161 | err = security_sem_semctl(NULL, cmd); |
1162 | if (err) |
1163 | return err; |
1164 | |
1165 | memset(&seminfo,0,sizeof(seminfo)); |
1166 | seminfo.semmni = ns->sc_semmni; |
1167 | seminfo.semmns = ns->sc_semmns; |
1168 | seminfo.semmsl = ns->sc_semmsl; |
1169 | seminfo.semopm = ns->sc_semopm; |
1170 | seminfo.semvmx = SEMVMX; |
1171 | seminfo.semmnu = SEMMNU; |
1172 | seminfo.semmap = SEMMAP; |
1173 | seminfo.semume = SEMUME; |
1174 | down_read(&sem_ids(ns).rwsem); |
1175 | if (cmd == SEM_INFO) { |
1176 | seminfo.semusz = sem_ids(ns).in_use; |
1177 | seminfo.semaem = ns->used_sems; |
1178 | } else { |
1179 | seminfo.semusz = SEMUSZ; |
1180 | seminfo.semaem = SEMAEM; |
1181 | } |
1182 | max_id = ipc_get_maxid(&sem_ids(ns)); |
1183 | up_read(&sem_ids(ns).rwsem); |
1184 | if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) |
1185 | return -EFAULT; |
1186 | return (max_id < 0) ? 0: max_id; |
1187 | } |
1188 | case IPC_STAT: |
1189 | case SEM_STAT: |
1190 | { |
1191 | struct semid64_ds tbuf; |
1192 | int id = 0; |
1193 | |
1194 | memset(&tbuf, 0, sizeof(tbuf)); |
1195 | |
1196 | rcu_read_lock(); |
1197 | if (cmd == SEM_STAT) { |
1198 | sma = sem_obtain_object(ns, semid); |
1199 | if (IS_ERR(sma)) { |
1200 | err = PTR_ERR(sma); |
1201 | goto out_unlock; |
1202 | } |
1203 | id = sma->sem_perm.id; |
1204 | } else { |
1205 | sma = sem_obtain_object_check(ns, semid); |
1206 | if (IS_ERR(sma)) { |
1207 | err = PTR_ERR(sma); |
1208 | goto out_unlock; |
1209 | } |
1210 | } |
1211 | |
1212 | err = -EACCES; |
1213 | if (ipcperms(ns, &sma->sem_perm, S_IRUGO)) |
1214 | goto out_unlock; |
1215 | |
1216 | err = security_sem_semctl(sma, cmd); |
1217 | if (err) |
1218 | goto out_unlock; |
1219 | |
1220 | kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm); |
1221 | tbuf.sem_otime = get_semotime(sma); |
1222 | tbuf.sem_ctime = sma->sem_ctime; |
1223 | tbuf.sem_nsems = sma->sem_nsems; |
1224 | rcu_read_unlock(); |
1225 | if (copy_semid_to_user(p, &tbuf, version)) |
1226 | return -EFAULT; |
1227 | return id; |
1228 | } |
1229 | default: |
1230 | return -EINVAL; |
1231 | } |
1232 | out_unlock: |
1233 | rcu_read_unlock(); |
1234 | return err; |
1235 | } |
1236 | |
1237 | static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, |
1238 | unsigned long arg) |
1239 | { |
1240 | struct sem_undo *un; |
1241 | struct sem_array *sma; |
1242 | struct sem* curr; |
1243 | int err; |
1244 | struct list_head tasks; |
1245 | int val; |
1246 | #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN) |
1247 | /* big-endian 64bit */ |
1248 | val = arg >> 32; |
1249 | #else |
1250 | /* 32bit or little-endian 64bit */ |
1251 | val = arg; |
1252 | #endif |
1253 | |
1254 | if (val > SEMVMX || val < 0) |
1255 | return -ERANGE; |
1256 | |
1257 | INIT_LIST_HEAD(&tasks); |
1258 | |
1259 | rcu_read_lock(); |
1260 | sma = sem_obtain_object_check(ns, semid); |
1261 | if (IS_ERR(sma)) { |
1262 | rcu_read_unlock(); |
1263 | return PTR_ERR(sma); |
1264 | } |
1265 | |
1266 | if (semnum < 0 || semnum >= sma->sem_nsems) { |
1267 | rcu_read_unlock(); |
1268 | return -EINVAL; |
1269 | } |
1270 | |
1271 | |
1272 | if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) { |
1273 | rcu_read_unlock(); |
1274 | return -EACCES; |
1275 | } |
1276 | |
1277 | err = security_sem_semctl(sma, SETVAL); |
1278 | if (err) { |
1279 | rcu_read_unlock(); |
1280 | return -EACCES; |
1281 | } |
1282 | |
1283 | sem_lock(sma, NULL, -1); |
1284 | |
1285 | if (sma->sem_perm.deleted) { |
1286 | sem_unlock(sma, -1); |
1287 | rcu_read_unlock(); |
1288 | return -EIDRM; |
1289 | } |
1290 | |
1291 | curr = &sma->sem_base[semnum]; |
1292 | |
1293 | ipc_assert_locked_object(&sma->sem_perm); |
1294 | list_for_each_entry(un, &sma->list_id, list_id) |
1295 | un->semadj[semnum] = 0; |
1296 | |
1297 | curr->semval = val; |
1298 | curr->sempid = task_tgid_vnr(current); |
1299 | sma->sem_ctime = get_seconds(); |
1300 | /* maybe some queued-up processes were waiting for this */ |
1301 | do_smart_update(sma, NULL, 0, 0, &tasks); |
1302 | sem_unlock(sma, -1); |
1303 | rcu_read_unlock(); |
1304 | wake_up_sem_queue_do(&tasks); |
1305 | return 0; |
1306 | } |
1307 | |
1308 | static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, |
1309 | int cmd, void __user *p) |
1310 | { |
1311 | struct sem_array *sma; |
1312 | struct sem* curr; |
1313 | int err, nsems; |
1314 | ushort fast_sem_io[SEMMSL_FAST]; |
1315 | ushort* sem_io = fast_sem_io; |
1316 | struct list_head tasks; |
1317 | |
1318 | INIT_LIST_HEAD(&tasks); |
1319 | |
1320 | rcu_read_lock(); |
1321 | sma = sem_obtain_object_check(ns, semid); |
1322 | if (IS_ERR(sma)) { |
1323 | rcu_read_unlock(); |
1324 | return PTR_ERR(sma); |
1325 | } |
1326 | |
1327 | nsems = sma->sem_nsems; |
1328 | |
1329 | err = -EACCES; |
1330 | if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO)) |
1331 | goto out_rcu_wakeup; |
1332 | |
1333 | err = security_sem_semctl(sma, cmd); |
1334 | if (err) |
1335 | goto out_rcu_wakeup; |
1336 | |
1337 | err = -EACCES; |
1338 | switch (cmd) { |
1339 | case GETALL: |
1340 | { |
1341 | ushort __user *array = p; |
1342 | int i; |
1343 | |
1344 | sem_lock(sma, NULL, -1); |
1345 | if (sma->sem_perm.deleted) { |
1346 | err = -EIDRM; |
1347 | goto out_unlock; |
1348 | } |
1349 | if(nsems > SEMMSL_FAST) { |
1350 | if (!ipc_rcu_getref(sma)) { |
1351 | err = -EIDRM; |
1352 | goto out_unlock; |
1353 | } |
1354 | sem_unlock(sma, -1); |
1355 | rcu_read_unlock(); |
1356 | sem_io = ipc_alloc(sizeof(ushort)*nsems); |
1357 | if(sem_io == NULL) { |
1358 | ipc_rcu_putref(sma, ipc_rcu_free); |
1359 | return -ENOMEM; |
1360 | } |
1361 | |
1362 | rcu_read_lock(); |
1363 | sem_lock_and_putref(sma); |
1364 | if (sma->sem_perm.deleted) { |
1365 | err = -EIDRM; |
1366 | goto out_unlock; |
1367 | } |
1368 | } |
1369 | for (i = 0; i < sma->sem_nsems; i++) |
1370 | sem_io[i] = sma->sem_base[i].semval; |
1371 | sem_unlock(sma, -1); |
1372 | rcu_read_unlock(); |
1373 | err = 0; |
1374 | if(copy_to_user(array, sem_io, nsems*sizeof(ushort))) |
1375 | err = -EFAULT; |
1376 | goto out_free; |
1377 | } |
1378 | case SETALL: |
1379 | { |
1380 | int i; |
1381 | struct sem_undo *un; |
1382 | |
1383 | if (!ipc_rcu_getref(sma)) { |
1384 | err = -EIDRM; |
1385 | goto out_rcu_wakeup; |
1386 | } |
1387 | rcu_read_unlock(); |
1388 | |
1389 | if(nsems > SEMMSL_FAST) { |
1390 | sem_io = ipc_alloc(sizeof(ushort)*nsems); |
1391 | if(sem_io == NULL) { |
1392 | ipc_rcu_putref(sma, ipc_rcu_free); |
1393 | return -ENOMEM; |
1394 | } |
1395 | } |
1396 | |
1397 | if (copy_from_user (sem_io, p, nsems*sizeof(ushort))) { |
1398 | ipc_rcu_putref(sma, ipc_rcu_free); |
1399 | err = -EFAULT; |
1400 | goto out_free; |
1401 | } |
1402 | |
1403 | for (i = 0; i < nsems; i++) { |
1404 | if (sem_io[i] > SEMVMX) { |
1405 | ipc_rcu_putref(sma, ipc_rcu_free); |
1406 | err = -ERANGE; |
1407 | goto out_free; |
1408 | } |
1409 | } |
1410 | rcu_read_lock(); |
1411 | sem_lock_and_putref(sma); |
1412 | if (sma->sem_perm.deleted) { |
1413 | err = -EIDRM; |
1414 | goto out_unlock; |
1415 | } |
1416 | |
1417 | for (i = 0; i < nsems; i++) |
1418 | sma->sem_base[i].semval = sem_io[i]; |
1419 | |
1420 | ipc_assert_locked_object(&sma->sem_perm); |
1421 | list_for_each_entry(un, &sma->list_id, list_id) { |
1422 | for (i = 0; i < nsems; i++) |
1423 | un->semadj[i] = 0; |
1424 | } |
1425 | sma->sem_ctime = get_seconds(); |
1426 | /* maybe some queued-up processes were waiting for this */ |
1427 | do_smart_update(sma, NULL, 0, 0, &tasks); |
1428 | err = 0; |
1429 | goto out_unlock; |
1430 | } |
1431 | /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */ |
1432 | } |
1433 | err = -EINVAL; |
1434 | if (semnum < 0 || semnum >= nsems) |
1435 | goto out_rcu_wakeup; |
1436 | |
1437 | sem_lock(sma, NULL, -1); |
1438 | if (sma->sem_perm.deleted) { |
1439 | err = -EIDRM; |
1440 | goto out_unlock; |
1441 | } |
1442 | curr = &sma->sem_base[semnum]; |
1443 | |
1444 | switch (cmd) { |
1445 | case GETVAL: |
1446 | err = curr->semval; |
1447 | goto out_unlock; |
1448 | case GETPID: |
1449 | err = curr->sempid; |
1450 | goto out_unlock; |
1451 | case GETNCNT: |
1452 | err = count_semncnt(sma,semnum); |
1453 | goto out_unlock; |
1454 | case GETZCNT: |
1455 | err = count_semzcnt(sma,semnum); |
1456 | goto out_unlock; |
1457 | } |
1458 | |
1459 | out_unlock: |
1460 | sem_unlock(sma, -1); |
1461 | out_rcu_wakeup: |
1462 | rcu_read_unlock(); |
1463 | wake_up_sem_queue_do(&tasks); |
1464 | out_free: |
1465 | if(sem_io != fast_sem_io) |
1466 | ipc_free(sem_io, sizeof(ushort)*nsems); |
1467 | return err; |
1468 | } |
1469 | |
1470 | static inline unsigned long |
1471 | copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) |
1472 | { |
1473 | switch(version) { |
1474 | case IPC_64: |
1475 | if (copy_from_user(out, buf, sizeof(*out))) |
1476 | return -EFAULT; |
1477 | return 0; |
1478 | case IPC_OLD: |
1479 | { |
1480 | struct semid_ds tbuf_old; |
1481 | |
1482 | if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) |
1483 | return -EFAULT; |
1484 | |
1485 | out->sem_perm.uid = tbuf_old.sem_perm.uid; |
1486 | out->sem_perm.gid = tbuf_old.sem_perm.gid; |
1487 | out->sem_perm.mode = tbuf_old.sem_perm.mode; |
1488 | |
1489 | return 0; |
1490 | } |
1491 | default: |
1492 | return -EINVAL; |
1493 | } |
1494 | } |
1495 | |
1496 | /* |
1497 | * This function handles some semctl commands which require the rwsem |
1498 | * to be held in write mode. |
1499 | * NOTE: no locks must be held, the rwsem is taken inside this function. |
1500 | */ |
1501 | static int semctl_down(struct ipc_namespace *ns, int semid, |
1502 | int cmd, int version, void __user *p) |
1503 | { |
1504 | struct sem_array *sma; |
1505 | int err; |
1506 | struct semid64_ds semid64; |
1507 | struct kern_ipc_perm *ipcp; |
1508 | |
1509 | if(cmd == IPC_SET) { |
1510 | if (copy_semid_from_user(&semid64, p, version)) |
1511 | return -EFAULT; |
1512 | } |
1513 | |
1514 | down_write(&sem_ids(ns).rwsem); |
1515 | rcu_read_lock(); |
1516 | |
1517 | ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd, |
1518 | &semid64.sem_perm, 0); |
1519 | if (IS_ERR(ipcp)) { |
1520 | err = PTR_ERR(ipcp); |
1521 | goto out_unlock1; |
1522 | } |
1523 | |
1524 | sma = container_of(ipcp, struct sem_array, sem_perm); |
1525 | |
1526 | err = security_sem_semctl(sma, cmd); |
1527 | if (err) |
1528 | goto out_unlock1; |
1529 | |
1530 | switch (cmd) { |
1531 | case IPC_RMID: |
1532 | sem_lock(sma, NULL, -1); |
1533 | /* freeary unlocks the ipc object and rcu */ |
1534 | freeary(ns, ipcp); |
1535 | goto out_up; |
1536 | case IPC_SET: |
1537 | sem_lock(sma, NULL, -1); |
1538 | err = ipc_update_perm(&semid64.sem_perm, ipcp); |
1539 | if (err) |
1540 | goto out_unlock0; |
1541 | sma->sem_ctime = get_seconds(); |
1542 | break; |
1543 | default: |
1544 | err = -EINVAL; |
1545 | goto out_unlock1; |
1546 | } |
1547 | |
1548 | out_unlock0: |
1549 | sem_unlock(sma, -1); |
1550 | out_unlock1: |
1551 | rcu_read_unlock(); |
1552 | out_up: |
1553 | up_write(&sem_ids(ns).rwsem); |
1554 | return err; |
1555 | } |
1556 | |
1557 | SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) |
1558 | { |
1559 | int version; |
1560 | struct ipc_namespace *ns; |
1561 | void __user *p = (void __user *)arg; |
1562 | |
1563 | if (semid < 0) |
1564 | return -EINVAL; |
1565 | |
1566 | version = ipc_parse_version(&cmd); |
1567 | ns = current->nsproxy->ipc_ns; |
1568 | |
1569 | switch(cmd) { |
1570 | case IPC_INFO: |
1571 | case SEM_INFO: |
1572 | case IPC_STAT: |
1573 | case SEM_STAT: |
1574 | return semctl_nolock(ns, semid, cmd, version, p); |
1575 | case GETALL: |
1576 | case GETVAL: |
1577 | case GETPID: |
1578 | case GETNCNT: |
1579 | case GETZCNT: |
1580 | case SETALL: |
1581 | return semctl_main(ns, semid, semnum, cmd, p); |
1582 | case SETVAL: |
1583 | return semctl_setval(ns, semid, semnum, arg); |
1584 | case IPC_RMID: |
1585 | case IPC_SET: |
1586 | return semctl_down(ns, semid, cmd, version, p); |
1587 | default: |
1588 | return -EINVAL; |
1589 | } |
1590 | } |
1591 | |
1592 | /* If the task doesn't already have a undo_list, then allocate one |
1593 | * here. We guarantee there is only one thread using this undo list, |
1594 | * and current is THE ONE |
1595 | * |
1596 | * If this allocation and assignment succeeds, but later |
1597 | * portions of this code fail, there is no need to free the sem_undo_list. |
1598 | * Just let it stay associated with the task, and it'll be freed later |
1599 | * at exit time. |
1600 | * |
1601 | * This can block, so callers must hold no locks. |
1602 | */ |
1603 | static inline int get_undo_list(struct sem_undo_list **undo_listp) |
1604 | { |
1605 | struct sem_undo_list *undo_list; |
1606 | |
1607 | undo_list = current->sysvsem.undo_list; |
1608 | if (!undo_list) { |
1609 | undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL); |
1610 | if (undo_list == NULL) |
1611 | return -ENOMEM; |
1612 | spin_lock_init(&undo_list->lock); |
1613 | atomic_set(&undo_list->refcnt, 1); |
1614 | INIT_LIST_HEAD(&undo_list->list_proc); |
1615 | |
1616 | current->sysvsem.undo_list = undo_list; |
1617 | } |
1618 | *undo_listp = undo_list; |
1619 | return 0; |
1620 | } |
1621 | |
1622 | static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) |
1623 | { |
1624 | struct sem_undo *un; |
1625 | |
1626 | list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) { |
1627 | if (un->semid == semid) |
1628 | return un; |
1629 | } |
1630 | return NULL; |
1631 | } |
1632 | |
1633 | static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) |
1634 | { |
1635 | struct sem_undo *un; |
1636 | |
1637 | assert_spin_locked(&ulp->lock); |
1638 | |
1639 | un = __lookup_undo(ulp, semid); |
1640 | if (un) { |
1641 | list_del_rcu(&un->list_proc); |
1642 | list_add_rcu(&un->list_proc, &ulp->list_proc); |
1643 | } |
1644 | return un; |
1645 | } |
1646 | |
1647 | /** |
1648 | * find_alloc_undo - Lookup (and if not present create) undo array |
1649 | * @ns: namespace |
1650 | * @semid: semaphore array id |
1651 | * |
1652 | * The function looks up (and if not present creates) the undo structure. |
1653 | * The size of the undo structure depends on the size of the semaphore |
1654 | * array, thus the alloc path is not that straightforward. |
1655 | * Lifetime-rules: sem_undo is rcu-protected, on success, the function |
1656 | * performs a rcu_read_lock(). |
1657 | */ |
1658 | static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) |
1659 | { |
1660 | struct sem_array *sma; |
1661 | struct sem_undo_list *ulp; |
1662 | struct sem_undo *un, *new; |
1663 | int nsems, error; |
1664 | |
1665 | error = get_undo_list(&ulp); |
1666 | if (error) |
1667 | return ERR_PTR(error); |
1668 | |
1669 | rcu_read_lock(); |
1670 | spin_lock(&ulp->lock); |
1671 | un = lookup_undo(ulp, semid); |
1672 | spin_unlock(&ulp->lock); |
1673 | if (likely(un!=NULL)) |
1674 | goto out; |
1675 | |
1676 | /* no undo structure around - allocate one. */ |
1677 | /* step 1: figure out the size of the semaphore array */ |
1678 | sma = sem_obtain_object_check(ns, semid); |
1679 | if (IS_ERR(sma)) { |
1680 | rcu_read_unlock(); |
1681 | return ERR_CAST(sma); |
1682 | } |
1683 | |
1684 | nsems = sma->sem_nsems; |
1685 | if (!ipc_rcu_getref(sma)) { |
1686 | rcu_read_unlock(); |
1687 | un = ERR_PTR(-EIDRM); |
1688 | goto out; |
1689 | } |
1690 | rcu_read_unlock(); |
1691 | |
1692 | /* step 2: allocate new undo structure */ |
1693 | new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL); |
1694 | if (!new) { |
1695 | ipc_rcu_putref(sma, ipc_rcu_free); |
1696 | return ERR_PTR(-ENOMEM); |
1697 | } |
1698 | |
1699 | /* step 3: Acquire the lock on semaphore array */ |
1700 | rcu_read_lock(); |
1701 | sem_lock_and_putref(sma); |
1702 | if (sma->sem_perm.deleted) { |
1703 | sem_unlock(sma, -1); |
1704 | rcu_read_unlock(); |
1705 | kfree(new); |
1706 | un = ERR_PTR(-EIDRM); |
1707 | goto out; |
1708 | } |
1709 | spin_lock(&ulp->lock); |
1710 | |
1711 | /* |
1712 | * step 4: check for races: did someone else allocate the undo struct? |
1713 | */ |
1714 | un = lookup_undo(ulp, semid); |
1715 | if (un) { |
1716 | kfree(new); |
1717 | goto success; |
1718 | } |
1719 | /* step 5: initialize & link new undo structure */ |
1720 | new->semadj = (short *) &new[1]; |
1721 | new->ulp = ulp; |
1722 | new->semid = semid; |
1723 | assert_spin_locked(&ulp->lock); |
1724 | list_add_rcu(&new->list_proc, &ulp->list_proc); |
1725 | ipc_assert_locked_object(&sma->sem_perm); |
1726 | list_add(&new->list_id, &sma->list_id); |
1727 | un = new; |
1728 | |
1729 | success: |
1730 | spin_unlock(&ulp->lock); |
1731 | sem_unlock(sma, -1); |
1732 | out: |
1733 | return un; |
1734 | } |
1735 | |
1736 | |
1737 | /** |
1738 | * get_queue_result - Retrieve the result code from sem_queue |
1739 | * @q: Pointer to queue structure |
1740 | * |
1741 | * Retrieve the return code from the pending queue. If IN_WAKEUP is found in |
1742 | * q->status, then we must loop until the value is replaced with the final |
1743 | * value: This may happen if a task is woken up by an unrelated event (e.g. |
1744 | * signal) and in parallel the task is woken up by another task because it got |
1745 | * the requested semaphores. |
1746 | * |
1747 | * The function can be called with or without holding the semaphore spinlock. |
1748 | */ |
1749 | static int get_queue_result(struct sem_queue *q) |
1750 | { |
1751 | int error; |
1752 | |
1753 | error = q->status; |
1754 | while (unlikely(error == IN_WAKEUP)) { |
1755 | cpu_relax(); |
1756 | error = q->status; |
1757 | } |
1758 | |
1759 | return error; |
1760 | } |
1761 | |
1762 | SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, |
1763 | unsigned, nsops, const struct timespec __user *, timeout) |
1764 | { |
1765 | int error = -EINVAL; |
1766 | struct sem_array *sma; |
1767 | struct sembuf fast_sops[SEMOPM_FAST]; |
1768 | struct sembuf* sops = fast_sops, *sop; |
1769 | struct sem_undo *un; |
1770 | int undos = 0, alter = 0, max, locknum; |
1771 | struct sem_queue queue; |
1772 | unsigned long jiffies_left = 0; |
1773 | struct ipc_namespace *ns; |
1774 | struct list_head tasks; |
1775 | |
1776 | ns = current->nsproxy->ipc_ns; |
1777 | |
1778 | if (nsops < 1 || semid < 0) |
1779 | return -EINVAL; |
1780 | if (nsops > ns->sc_semopm) |
1781 | return -E2BIG; |
1782 | if(nsops > SEMOPM_FAST) { |
1783 | sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL); |
1784 | if(sops==NULL) |
1785 | return -ENOMEM; |
1786 | } |
1787 | if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) { |
1788 | error=-EFAULT; |
1789 | goto out_free; |
1790 | } |
1791 | if (timeout) { |
1792 | struct timespec _timeout; |
1793 | if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) { |
1794 | error = -EFAULT; |
1795 | goto out_free; |
1796 | } |
1797 | if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 || |
1798 | _timeout.tv_nsec >= 1000000000L) { |
1799 | error = -EINVAL; |
1800 | goto out_free; |
1801 | } |
1802 | jiffies_left = timespec_to_jiffies(&_timeout); |
1803 | } |
1804 | max = 0; |
1805 | for (sop = sops; sop < sops + nsops; sop++) { |
1806 | if (sop->sem_num >= max) |
1807 | max = sop->sem_num; |
1808 | if (sop->sem_flg & SEM_UNDO) |
1809 | undos = 1; |
1810 | if (sop->sem_op != 0) |
1811 | alter = 1; |
1812 | } |
1813 | |
1814 | INIT_LIST_HEAD(&tasks); |
1815 | |
1816 | if (undos) { |
1817 | /* On success, find_alloc_undo takes the rcu_read_lock */ |
1818 | un = find_alloc_undo(ns, semid); |
1819 | if (IS_ERR(un)) { |
1820 | error = PTR_ERR(un); |
1821 | goto out_free; |
1822 | } |
1823 | } else { |
1824 | un = NULL; |
1825 | rcu_read_lock(); |
1826 | } |
1827 | |
1828 | sma = sem_obtain_object_check(ns, semid); |
1829 | if (IS_ERR(sma)) { |
1830 | rcu_read_unlock(); |
1831 | error = PTR_ERR(sma); |
1832 | goto out_free; |
1833 | } |
1834 | |
1835 | error = -EFBIG; |
1836 | if (max >= sma->sem_nsems) |
1837 | goto out_rcu_wakeup; |
1838 | |
1839 | error = -EACCES; |
1840 | if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) |
1841 | goto out_rcu_wakeup; |
1842 | |
1843 | error = security_sem_semop(sma, sops, nsops, alter); |
1844 | if (error) |
1845 | goto out_rcu_wakeup; |
1846 | |
1847 | error = -EIDRM; |
1848 | locknum = sem_lock(sma, sops, nsops); |
1849 | if (sma->sem_perm.deleted) |
1850 | goto out_unlock_free; |
1851 | /* |
1852 | * semid identifiers are not unique - find_alloc_undo may have |
1853 | * allocated an undo structure, it was invalidated by an RMID |
1854 | * and now a new array with received the same id. Check and fail. |
1855 | * This case can be detected checking un->semid. The existence of |
1856 | * "un" itself is guaranteed by rcu. |
1857 | */ |
1858 | if (un && un->semid == -1) |
1859 | goto out_unlock_free; |
1860 | |
1861 | error = perform_atomic_semop(sma, sops, nsops, un, |
1862 | task_tgid_vnr(current)); |
1863 | if (error == 0) { |
1864 | /* If the operation was successful, then do |
1865 | * the required updates. |
1866 | */ |
1867 | if (alter) |
1868 | do_smart_update(sma, sops, nsops, 1, &tasks); |
1869 | else |
1870 | set_semotime(sma, sops); |
1871 | } |
1872 | if (error <= 0) |
1873 | goto out_unlock_free; |
1874 | |
1875 | /* We need to sleep on this operation, so we put the current |
1876 | * task into the pending queue and go to sleep. |
1877 | */ |
1878 | |
1879 | queue.sops = sops; |
1880 | queue.nsops = nsops; |
1881 | queue.undo = un; |
1882 | queue.pid = task_tgid_vnr(current); |
1883 | queue.alter = alter; |
1884 | |
1885 | if (nsops == 1) { |
1886 | struct sem *curr; |
1887 | curr = &sma->sem_base[sops->sem_num]; |
1888 | |
1889 | if (alter) { |
1890 | if (sma->complex_count) { |
1891 | list_add_tail(&queue.list, |
1892 | &sma->pending_alter); |
1893 | } else { |
1894 | |
1895 | list_add_tail(&queue.list, |
1896 | &curr->pending_alter); |
1897 | } |
1898 | } else { |
1899 | list_add_tail(&queue.list, &curr->pending_const); |
1900 | } |
1901 | } else { |
1902 | if (!sma->complex_count) |
1903 | merge_queues(sma); |
1904 | |
1905 | if (alter) |
1906 | list_add_tail(&queue.list, &sma->pending_alter); |
1907 | else |
1908 | list_add_tail(&queue.list, &sma->pending_const); |
1909 | |
1910 | sma->complex_count++; |
1911 | } |
1912 | |
1913 | queue.status = -EINTR; |
1914 | queue.sleeper = current; |
1915 | |
1916 | sleep_again: |
1917 | current->state = TASK_INTERRUPTIBLE; |
1918 | sem_unlock(sma, locknum); |
1919 | rcu_read_unlock(); |
1920 | |
1921 | if (timeout) |
1922 | jiffies_left = schedule_timeout(jiffies_left); |
1923 | else |
1924 | schedule(); |
1925 | |
1926 | error = get_queue_result(&queue); |
1927 | |
1928 | if (error != -EINTR) { |
1929 | /* fast path: update_queue already obtained all requested |
1930 | * resources. |
1931 | * Perform a smp_mb(): User space could assume that semop() |
1932 | * is a memory barrier: Without the mb(), the cpu could |
1933 | * speculatively read in user space stale data that was |
1934 | * overwritten by the previous owner of the semaphore. |
1935 | */ |
1936 | smp_mb(); |
1937 | |
1938 | goto out_free; |
1939 | } |
1940 | |
1941 | rcu_read_lock(); |
1942 | sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum); |
1943 | |
1944 | /* |
1945 | * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing. |
1946 | */ |
1947 | error = get_queue_result(&queue); |
1948 | |
1949 | /* |
1950 | * Array removed? If yes, leave without sem_unlock(). |
1951 | */ |
1952 | if (IS_ERR(sma)) { |
1953 | rcu_read_unlock(); |
1954 | goto out_free; |
1955 | } |
1956 | |
1957 | |
1958 | /* |
1959 | * If queue.status != -EINTR we are woken up by another process. |
1960 | * Leave without unlink_queue(), but with sem_unlock(). |
1961 | */ |
1962 | |
1963 | if (error != -EINTR) { |
1964 | goto out_unlock_free; |
1965 | } |
1966 | |
1967 | /* |
1968 | * If an interrupt occurred we have to clean up the queue |
1969 | */ |
1970 | if (timeout && jiffies_left == 0) |
1971 | error = -EAGAIN; |
1972 | |
1973 | /* |
1974 | * If the wakeup was spurious, just retry |
1975 | */ |
1976 | if (error == -EINTR && !signal_pending(current)) |
1977 | goto sleep_again; |
1978 | |
1979 | unlink_queue(sma, &queue); |
1980 | |
1981 | out_unlock_free: |
1982 | sem_unlock(sma, locknum); |
1983 | out_rcu_wakeup: |
1984 | rcu_read_unlock(); |
1985 | wake_up_sem_queue_do(&tasks); |
1986 | out_free: |
1987 | if(sops != fast_sops) |
1988 | kfree(sops); |
1989 | return error; |
1990 | } |
1991 | |
1992 | SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, |
1993 | unsigned, nsops) |
1994 | { |
1995 | return sys_semtimedop(semid, tsops, nsops, NULL); |
1996 | } |
1997 | |
1998 | /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between |
1999 | * parent and child tasks. |
2000 | */ |
2001 | |
2002 | int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) |
2003 | { |
2004 | struct sem_undo_list *undo_list; |
2005 | int error; |
2006 | |
2007 | if (clone_flags & CLONE_SYSVSEM) { |
2008 | error = get_undo_list(&undo_list); |
2009 | if (error) |
2010 | return error; |
2011 | atomic_inc(&undo_list->refcnt); |
2012 | tsk->sysvsem.undo_list = undo_list; |
2013 | } else |
2014 | tsk->sysvsem.undo_list = NULL; |
2015 | |
2016 | return 0; |
2017 | } |
2018 | |
2019 | /* |
2020 | * add semadj values to semaphores, free undo structures. |
2021 | * undo structures are not freed when semaphore arrays are destroyed |
2022 | * so some of them may be out of date. |
2023 | * IMPLEMENTATION NOTE: There is some confusion over whether the |
2024 | * set of adjustments that needs to be done should be done in an atomic |
2025 | * manner or not. That is, if we are attempting to decrement the semval |
2026 | * should we queue up and wait until we can do so legally? |
2027 | * The original implementation attempted to do this (queue and wait). |
2028 | * The current implementation does not do so. The POSIX standard |
2029 | * and SVID should be consulted to determine what behavior is mandated. |
2030 | */ |
2031 | void exit_sem(struct task_struct *tsk) |
2032 | { |
2033 | struct sem_undo_list *ulp; |
2034 | |
2035 | ulp = tsk->sysvsem.undo_list; |
2036 | if (!ulp) |
2037 | return; |
2038 | tsk->sysvsem.undo_list = NULL; |
2039 | |
2040 | if (!atomic_dec_and_test(&ulp->refcnt)) |
2041 | return; |
2042 | |
2043 | for (;;) { |
2044 | struct sem_array *sma; |
2045 | struct sem_undo *un; |
2046 | struct list_head tasks; |
2047 | int semid, i; |
2048 | |
2049 | rcu_read_lock(); |
2050 | un = list_entry_rcu(ulp->list_proc.next, |
2051 | struct sem_undo, list_proc); |
2052 | if (&un->list_proc == &ulp->list_proc) |
2053 | semid = -1; |
2054 | else |
2055 | semid = un->semid; |
2056 | |
2057 | if (semid == -1) { |
2058 | rcu_read_unlock(); |
2059 | break; |
2060 | } |
2061 | |
2062 | sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid); |
2063 | /* exit_sem raced with IPC_RMID, nothing to do */ |
2064 | if (IS_ERR(sma)) { |
2065 | rcu_read_unlock(); |
2066 | continue; |
2067 | } |
2068 | |
2069 | sem_lock(sma, NULL, -1); |
2070 | /* exit_sem raced with IPC_RMID, nothing to do */ |
2071 | if (sma->sem_perm.deleted) { |
2072 | sem_unlock(sma, -1); |
2073 | rcu_read_unlock(); |
2074 | continue; |
2075 | } |
2076 | un = __lookup_undo(ulp, semid); |
2077 | if (un == NULL) { |
2078 | /* exit_sem raced with IPC_RMID+semget() that created |
2079 | * exactly the same semid. Nothing to do. |
2080 | */ |
2081 | sem_unlock(sma, -1); |
2082 | rcu_read_unlock(); |
2083 | continue; |
2084 | } |
2085 | |
2086 | /* remove un from the linked lists */ |
2087 | ipc_assert_locked_object(&sma->sem_perm); |
2088 | list_del(&un->list_id); |
2089 | |
2090 | spin_lock(&ulp->lock); |
2091 | list_del_rcu(&un->list_proc); |
2092 | spin_unlock(&ulp->lock); |
2093 | |
2094 | /* perform adjustments registered in un */ |
2095 | for (i = 0; i < sma->sem_nsems; i++) { |
2096 | struct sem * semaphore = &sma->sem_base[i]; |
2097 | if (un->semadj[i]) { |
2098 | semaphore->semval += un->semadj[i]; |
2099 | /* |
2100 | * Range checks of the new semaphore value, |
2101 | * not defined by sus: |
2102 | * - Some unices ignore the undo entirely |
2103 | * (e.g. HP UX 11i 11.22, Tru64 V5.1) |
2104 | * - some cap the value (e.g. FreeBSD caps |
2105 | * at 0, but doesn't enforce SEMVMX) |
2106 | * |
2107 | * Linux caps the semaphore value, both at 0 |
2108 | * and at SEMVMX. |
2109 | * |
2110 | * Manfred <manfred@colorfullife.com> |
2111 | */ |
2112 | if (semaphore->semval < 0) |
2113 | semaphore->semval = 0; |
2114 | if (semaphore->semval > SEMVMX) |
2115 | semaphore->semval = SEMVMX; |
2116 | semaphore->sempid = task_tgid_vnr(current); |
2117 | } |
2118 | } |
2119 | /* maybe some queued-up processes were waiting for this */ |
2120 | INIT_LIST_HEAD(&tasks); |
2121 | do_smart_update(sma, NULL, 0, 1, &tasks); |
2122 | sem_unlock(sma, -1); |
2123 | rcu_read_unlock(); |
2124 | wake_up_sem_queue_do(&tasks); |
2125 | |
2126 | kfree_rcu(un, rcu); |
2127 | } |
2128 | kfree(ulp); |
2129 | } |
2130 | |
2131 | #ifdef CONFIG_PROC_FS |
2132 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it) |
2133 | { |
2134 | struct user_namespace *user_ns = seq_user_ns(s); |
2135 | struct sem_array *sma = it; |
2136 | time_t sem_otime; |
2137 | |
2138 | /* |
2139 | * The proc interface isn't aware of sem_lock(), it calls |
2140 | * ipc_lock_object() directly (in sysvipc_find_ipc). |
2141 | * In order to stay compatible with sem_lock(), we must wait until |
2142 | * all simple semop() calls have left their critical regions. |
2143 | */ |
2144 | sem_wait_array(sma); |
2145 | |
2146 | sem_otime = get_semotime(sma); |
2147 | |
2148 | return seq_printf(s, |
2149 | "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n", |
2150 | sma->sem_perm.key, |
2151 | sma->sem_perm.id, |
2152 | sma->sem_perm.mode, |
2153 | sma->sem_nsems, |
2154 | from_kuid_munged(user_ns, sma->sem_perm.uid), |
2155 | from_kgid_munged(user_ns, sma->sem_perm.gid), |
2156 | from_kuid_munged(user_ns, sma->sem_perm.cuid), |
2157 | from_kgid_munged(user_ns, sma->sem_perm.cgid), |
2158 | sem_otime, |
2159 | sma->sem_ctime); |
2160 | } |
2161 | #endif |
2162 |
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