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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_semcnt() | |
51 | * - the task that performs a successful semop() scans the list of all | |
52 | * sleeping tasks and completes any pending operations that can be fulfilled. | |
53 | * Semaphores are actively given to waiting tasks (necessary for FIFO). | |
54 | * (see update_queue()) | |
55 | * - To improve the scalability, the actual wake-up calls are performed after | |
56 | * dropping all locks. (see wake_up_sem_queue_prepare(), | |
57 | * wake_up_sem_queue_do()) | |
58 | * - All work is done by the waker, the woken up task does not have to do | |
59 | * anything - not even acquiring a lock or dropping a refcount. | |
60 | * - A woken up task may not even touch the semaphore array anymore, it may | |
61 | * have been destroyed already by a semctl(RMID). | |
62 | * - The synchronizations between wake-ups due to a timeout/signal and a | |
63 | * wake-up due to a completed semaphore operation is achieved by using an | |
64 | * intermediate state (IN_WAKEUP). | |
65 | * - UNDO values are stored in an array (one per process and per | |
66 | * semaphore array, lazily allocated). For backwards compatibility, multiple | |
67 | * modes for the UNDO variables are supported (per process, per thread) | |
68 | * (see copy_semundo, CLONE_SYSVSEM) | |
69 | * - There are two lists of the pending operations: a per-array list | |
70 | * and per-semaphore list (stored in the array). This allows to achieve FIFO | |
71 | * ordering without always scanning all pending operations. | |
72 | * The worst-case behavior is nevertheless O(N^2) for N wakeups. | |
73 | */ | |
74 | ||
75 | #include <linux/slab.h> | |
76 | #include <linux/spinlock.h> | |
77 | #include <linux/init.h> | |
78 | #include <linux/proc_fs.h> | |
79 | #include <linux/time.h> | |
80 | #include <linux/security.h> | |
81 | #include <linux/syscalls.h> | |
82 | #include <linux/audit.h> | |
83 | #include <linux/capability.h> | |
84 | #include <linux/seq_file.h> | |
85 | #include <linux/rwsem.h> | |
86 | #include <linux/nsproxy.h> | |
87 | #include <linux/ipc_namespace.h> | |
88 | ||
89 | #include <linux/uaccess.h> | |
90 | #include "util.h" | |
91 | ||
92 | /* One semaphore structure for each semaphore in the system. */ | |
93 | struct sem { | |
94 | int semval; /* current value */ | |
95 | int sempid; /* pid of last operation */ | |
96 | spinlock_t lock; /* spinlock for fine-grained semtimedop */ | |
97 | struct list_head pending_alter; /* pending single-sop operations */ | |
98 | /* that alter the semaphore */ | |
99 | struct list_head pending_const; /* pending single-sop operations */ | |
100 | /* that do not alter the semaphore*/ | |
101 | time_t sem_otime; /* candidate for sem_otime */ | |
102 | } ____cacheline_aligned_in_smp; | |
103 | ||
104 | /* One queue for each sleeping process in the system. */ | |
105 | struct sem_queue { | |
106 | struct list_head list; /* queue of pending operations */ | |
107 | struct task_struct *sleeper; /* this process */ | |
108 | struct sem_undo *undo; /* undo structure */ | |
109 | int pid; /* process id of requesting process */ | |
110 | int status; /* completion status of operation */ | |
111 | struct sembuf *sops; /* array of pending operations */ | |
112 | struct sembuf *blocking; /* the operation that blocked */ | |
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 | * spin_unlock_wait() and !spin_is_locked() are not memory barriers, they | |
257 | * are only control barriers. | |
258 | * The code must pair with spin_unlock(&sem->lock) or | |
259 | * spin_unlock(&sem_perm.lock), thus just the control barrier is insufficient. | |
260 | * | |
261 | * smp_rmb() is sufficient, as writes cannot pass the control barrier. | |
262 | */ | |
263 | #define ipc_smp_acquire__after_spin_is_unlocked() smp_rmb() | |
264 | ||
265 | /* | |
266 | * Wait until all currently ongoing simple ops have completed. | |
267 | * Caller must own sem_perm.lock. | |
268 | * New simple ops cannot start, because simple ops first check | |
269 | * that sem_perm.lock is free. | |
270 | * that a) sem_perm.lock is free and b) complex_count is 0. | |
271 | */ | |
272 | static void sem_wait_array(struct sem_array *sma) | |
273 | { | |
274 | int i; | |
275 | struct sem *sem; | |
276 | ||
277 | if (sma->complex_count) { | |
278 | /* The thread that increased sma->complex_count waited on | |
279 | * all sem->lock locks. Thus we don't need to wait again. | |
280 | */ | |
281 | return; | |
282 | } | |
283 | ||
284 | for (i = 0; i < sma->sem_nsems; i++) { | |
285 | sem = sma->sem_base + i; | |
286 | spin_unlock_wait(&sem->lock); | |
287 | } | |
288 | ipc_smp_acquire__after_spin_is_unlocked(); | |
289 | } | |
290 | ||
291 | /* | |
292 | * If the request contains only one semaphore operation, and there are | |
293 | * no complex transactions pending, lock only the semaphore involved. | |
294 | * Otherwise, lock the entire semaphore array, since we either have | |
295 | * multiple semaphores in our own semops, or we need to look at | |
296 | * semaphores from other pending complex operations. | |
297 | */ | |
298 | static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, | |
299 | int nsops) | |
300 | { | |
301 | struct sem *sem; | |
302 | ||
303 | if (nsops != 1) { | |
304 | /* Complex operation - acquire a full lock */ | |
305 | ipc_lock_object(&sma->sem_perm); | |
306 | ||
307 | /* And wait until all simple ops that are processed | |
308 | * right now have dropped their locks. | |
309 | */ | |
310 | sem_wait_array(sma); | |
311 | return -1; | |
312 | } | |
313 | ||
314 | /* | |
315 | * Only one semaphore affected - try to optimize locking. | |
316 | * The rules are: | |
317 | * - optimized locking is possible if no complex operation | |
318 | * is either enqueued or processed right now. | |
319 | * - The test for enqueued complex ops is simple: | |
320 | * sma->complex_count != 0 | |
321 | * - Testing for complex ops that are processed right now is | |
322 | * a bit more difficult. Complex ops acquire the full lock | |
323 | * and first wait that the running simple ops have completed. | |
324 | * (see above) | |
325 | * Thus: If we own a simple lock and the global lock is free | |
326 | * and complex_count is now 0, then it will stay 0 and | |
327 | * thus just locking sem->lock is sufficient. | |
328 | */ | |
329 | sem = sma->sem_base + sops->sem_num; | |
330 | ||
331 | if (sma->complex_count == 0) { | |
332 | /* | |
333 | * It appears that no complex operation is around. | |
334 | * Acquire the per-semaphore lock. | |
335 | */ | |
336 | spin_lock(&sem->lock); | |
337 | ||
338 | /* Then check that the global lock is free */ | |
339 | if (!spin_is_locked(&sma->sem_perm.lock)) { | |
340 | /* | |
341 | * We need a memory barrier with acquire semantics, | |
342 | * otherwise we can race with another thread that does: | |
343 | * complex_count++; | |
344 | * spin_unlock(sem_perm.lock); | |
345 | */ | |
346 | ipc_smp_acquire__after_spin_is_unlocked(); | |
347 | ||
348 | /* | |
349 | * Now repeat the test of complex_count: | |
350 | * It can't change anymore until we drop sem->lock. | |
351 | * Thus: if is now 0, then it will stay 0. | |
352 | */ | |
353 | if (sma->complex_count == 0) { | |
354 | /* fast path successful! */ | |
355 | return sops->sem_num; | |
356 | } | |
357 | } | |
358 | spin_unlock(&sem->lock); | |
359 | } | |
360 | ||
361 | /* slow path: acquire the full lock */ | |
362 | ipc_lock_object(&sma->sem_perm); | |
363 | ||
364 | if (sma->complex_count == 0) { | |
365 | /* False alarm: | |
366 | * There is no complex operation, thus we can switch | |
367 | * back to the fast path. | |
368 | */ | |
369 | spin_lock(&sem->lock); | |
370 | ipc_unlock_object(&sma->sem_perm); | |
371 | return sops->sem_num; | |
372 | } else { | |
373 | /* Not a false alarm, thus complete the sequence for a | |
374 | * full lock. | |
375 | */ | |
376 | sem_wait_array(sma); | |
377 | return -1; | |
378 | } | |
379 | } | |
380 | ||
381 | static inline void sem_unlock(struct sem_array *sma, int locknum) | |
382 | { | |
383 | if (locknum == -1) { | |
384 | unmerge_queues(sma); | |
385 | ipc_unlock_object(&sma->sem_perm); | |
386 | } else { | |
387 | struct sem *sem = sma->sem_base + locknum; | |
388 | spin_unlock(&sem->lock); | |
389 | } | |
390 | } | |
391 | ||
392 | /* | |
393 | * sem_lock_(check_) routines are called in the paths where the rwsem | |
394 | * is not held. | |
395 | * | |
396 | * The caller holds the RCU read lock. | |
397 | */ | |
398 | static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns, | |
399 | int id, struct sembuf *sops, int nsops, int *locknum) | |
400 | { | |
401 | struct kern_ipc_perm *ipcp; | |
402 | struct sem_array *sma; | |
403 | ||
404 | ipcp = ipc_obtain_object_idr(&sem_ids(ns), id); | |
405 | if (IS_ERR(ipcp)) | |
406 | return ERR_CAST(ipcp); | |
407 | ||
408 | sma = container_of(ipcp, struct sem_array, sem_perm); | |
409 | *locknum = sem_lock(sma, sops, nsops); | |
410 | ||
411 | /* ipc_rmid() may have already freed the ID while sem_lock | |
412 | * was spinning: verify that the structure is still valid | |
413 | */ | |
414 | if (ipc_valid_object(ipcp)) | |
415 | return container_of(ipcp, struct sem_array, sem_perm); | |
416 | ||
417 | sem_unlock(sma, *locknum); | |
418 | return ERR_PTR(-EINVAL); | |
419 | } | |
420 | ||
421 | static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) | |
422 | { | |
423 | struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id); | |
424 | ||
425 | if (IS_ERR(ipcp)) | |
426 | return ERR_CAST(ipcp); | |
427 | ||
428 | return container_of(ipcp, struct sem_array, sem_perm); | |
429 | } | |
430 | ||
431 | static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns, | |
432 | int id) | |
433 | { | |
434 | struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id); | |
435 | ||
436 | if (IS_ERR(ipcp)) | |
437 | return ERR_CAST(ipcp); | |
438 | ||
439 | return container_of(ipcp, struct sem_array, sem_perm); | |
440 | } | |
441 | ||
442 | static inline void sem_lock_and_putref(struct sem_array *sma) | |
443 | { | |
444 | sem_lock(sma, NULL, -1); | |
445 | ipc_rcu_putref(sma, ipc_rcu_free); | |
446 | } | |
447 | ||
448 | static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) | |
449 | { | |
450 | ipc_rmid(&sem_ids(ns), &s->sem_perm); | |
451 | } | |
452 | ||
453 | /* | |
454 | * Lockless wakeup algorithm: | |
455 | * Without the check/retry algorithm a lockless wakeup is possible: | |
456 | * - queue.status is initialized to -EINTR before blocking. | |
457 | * - wakeup is performed by | |
458 | * * unlinking the queue entry from the pending list | |
459 | * * setting queue.status to IN_WAKEUP | |
460 | * This is the notification for the blocked thread that a | |
461 | * result value is imminent. | |
462 | * * call wake_up_process | |
463 | * * set queue.status to the final value. | |
464 | * - the previously blocked thread checks queue.status: | |
465 | * * if it's IN_WAKEUP, then it must wait until the value changes | |
466 | * * if it's not -EINTR, then the operation was completed by | |
467 | * update_queue. semtimedop can return queue.status without | |
468 | * performing any operation on the sem array. | |
469 | * * otherwise it must acquire the spinlock and check what's up. | |
470 | * | |
471 | * The two-stage algorithm is necessary to protect against the following | |
472 | * races: | |
473 | * - if queue.status is set after wake_up_process, then the woken up idle | |
474 | * thread could race forward and try (and fail) to acquire sma->lock | |
475 | * before update_queue had a chance to set queue.status | |
476 | * - if queue.status is written before wake_up_process and if the | |
477 | * blocked process is woken up by a signal between writing | |
478 | * queue.status and the wake_up_process, then the woken up | |
479 | * process could return from semtimedop and die by calling | |
480 | * sys_exit before wake_up_process is called. Then wake_up_process | |
481 | * will oops, because the task structure is already invalid. | |
482 | * (yes, this happened on s390 with sysv msg). | |
483 | * | |
484 | */ | |
485 | #define IN_WAKEUP 1 | |
486 | ||
487 | /** | |
488 | * newary - Create a new semaphore set | |
489 | * @ns: namespace | |
490 | * @params: ptr to the structure that contains key, semflg and nsems | |
491 | * | |
492 | * Called with sem_ids.rwsem held (as a writer) | |
493 | */ | |
494 | static int newary(struct ipc_namespace *ns, struct ipc_params *params) | |
495 | { | |
496 | int id; | |
497 | int retval; | |
498 | struct sem_array *sma; | |
499 | int size; | |
500 | key_t key = params->key; | |
501 | int nsems = params->u.nsems; | |
502 | int semflg = params->flg; | |
503 | int i; | |
504 | ||
505 | if (!nsems) | |
506 | return -EINVAL; | |
507 | if (ns->used_sems + nsems > ns->sc_semmns) | |
508 | return -ENOSPC; | |
509 | ||
510 | size = sizeof(*sma) + nsems * sizeof(struct sem); | |
511 | sma = ipc_rcu_alloc(size); | |
512 | if (!sma) | |
513 | return -ENOMEM; | |
514 | ||
515 | memset(sma, 0, size); | |
516 | ||
517 | sma->sem_perm.mode = (semflg & S_IRWXUGO); | |
518 | sma->sem_perm.key = key; | |
519 | ||
520 | sma->sem_perm.security = NULL; | |
521 | retval = security_sem_alloc(sma); | |
522 | if (retval) { | |
523 | ipc_rcu_putref(sma, ipc_rcu_free); | |
524 | return retval; | |
525 | } | |
526 | ||
527 | sma->sem_base = (struct sem *) &sma[1]; | |
528 | ||
529 | for (i = 0; i < nsems; i++) { | |
530 | INIT_LIST_HEAD(&sma->sem_base[i].pending_alter); | |
531 | INIT_LIST_HEAD(&sma->sem_base[i].pending_const); | |
532 | spin_lock_init(&sma->sem_base[i].lock); | |
533 | } | |
534 | ||
535 | sma->complex_count = 0; | |
536 | INIT_LIST_HEAD(&sma->pending_alter); | |
537 | INIT_LIST_HEAD(&sma->pending_const); | |
538 | INIT_LIST_HEAD(&sma->list_id); | |
539 | sma->sem_nsems = nsems; | |
540 | sma->sem_ctime = get_seconds(); | |
541 | ||
542 | id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); | |
543 | if (id < 0) { | |
544 | ipc_rcu_putref(sma, sem_rcu_free); | |
545 | return id; | |
546 | } | |
547 | ns->used_sems += nsems; | |
548 | ||
549 | sem_unlock(sma, -1); | |
550 | rcu_read_unlock(); | |
551 | ||
552 | return sma->sem_perm.id; | |
553 | } | |
554 | ||
555 | ||
556 | /* | |
557 | * Called with sem_ids.rwsem and ipcp locked. | |
558 | */ | |
559 | static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg) | |
560 | { | |
561 | struct sem_array *sma; | |
562 | ||
563 | sma = container_of(ipcp, struct sem_array, sem_perm); | |
564 | return security_sem_associate(sma, semflg); | |
565 | } | |
566 | ||
567 | /* | |
568 | * Called with sem_ids.rwsem and ipcp locked. | |
569 | */ | |
570 | static inline int sem_more_checks(struct kern_ipc_perm *ipcp, | |
571 | struct ipc_params *params) | |
572 | { | |
573 | struct sem_array *sma; | |
574 | ||
575 | sma = container_of(ipcp, struct sem_array, sem_perm); | |
576 | if (params->u.nsems > sma->sem_nsems) | |
577 | return -EINVAL; | |
578 | ||
579 | return 0; | |
580 | } | |
581 | ||
582 | SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) | |
583 | { | |
584 | struct ipc_namespace *ns; | |
585 | static const struct ipc_ops sem_ops = { | |
586 | .getnew = newary, | |
587 | .associate = sem_security, | |
588 | .more_checks = sem_more_checks, | |
589 | }; | |
590 | struct ipc_params sem_params; | |
591 | ||
592 | ns = current->nsproxy->ipc_ns; | |
593 | ||
594 | if (nsems < 0 || nsems > ns->sc_semmsl) | |
595 | return -EINVAL; | |
596 | ||
597 | sem_params.key = key; | |
598 | sem_params.flg = semflg; | |
599 | sem_params.u.nsems = nsems; | |
600 | ||
601 | return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); | |
602 | } | |
603 | ||
604 | /** | |
605 | * perform_atomic_semop - Perform (if possible) a semaphore operation | |
606 | * @sma: semaphore array | |
607 | * @q: struct sem_queue that describes the operation | |
608 | * | |
609 | * Returns 0 if the operation was possible. | |
610 | * Returns 1 if the operation is impossible, the caller must sleep. | |
611 | * Negative values are error codes. | |
612 | */ | |
613 | static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q) | |
614 | { | |
615 | int result, sem_op, nsops, pid; | |
616 | struct sembuf *sop; | |
617 | struct sem *curr; | |
618 | struct sembuf *sops; | |
619 | struct sem_undo *un; | |
620 | ||
621 | sops = q->sops; | |
622 | nsops = q->nsops; | |
623 | un = q->undo; | |
624 | ||
625 | for (sop = sops; sop < sops + nsops; sop++) { | |
626 | curr = sma->sem_base + sop->sem_num; | |
627 | sem_op = sop->sem_op; | |
628 | result = curr->semval; | |
629 | ||
630 | if (!sem_op && result) | |
631 | goto would_block; | |
632 | ||
633 | result += sem_op; | |
634 | if (result < 0) | |
635 | goto would_block; | |
636 | if (result > SEMVMX) | |
637 | goto out_of_range; | |
638 | ||
639 | if (sop->sem_flg & SEM_UNDO) { | |
640 | int undo = un->semadj[sop->sem_num] - sem_op; | |
641 | /* Exceeding the undo range is an error. */ | |
642 | if (undo < (-SEMAEM - 1) || undo > SEMAEM) | |
643 | goto out_of_range; | |
644 | un->semadj[sop->sem_num] = undo; | |
645 | } | |
646 | ||
647 | curr->semval = result; | |
648 | } | |
649 | ||
650 | sop--; | |
651 | pid = q->pid; | |
652 | while (sop >= sops) { | |
653 | sma->sem_base[sop->sem_num].sempid = pid; | |
654 | sop--; | |
655 | } | |
656 | ||
657 | return 0; | |
658 | ||
659 | out_of_range: | |
660 | result = -ERANGE; | |
661 | goto undo; | |
662 | ||
663 | would_block: | |
664 | q->blocking = sop; | |
665 | ||
666 | if (sop->sem_flg & IPC_NOWAIT) | |
667 | result = -EAGAIN; | |
668 | else | |
669 | result = 1; | |
670 | ||
671 | undo: | |
672 | sop--; | |
673 | while (sop >= sops) { | |
674 | sem_op = sop->sem_op; | |
675 | sma->sem_base[sop->sem_num].semval -= sem_op; | |
676 | if (sop->sem_flg & SEM_UNDO) | |
677 | un->semadj[sop->sem_num] += sem_op; | |
678 | sop--; | |
679 | } | |
680 | ||
681 | return result; | |
682 | } | |
683 | ||
684 | /** wake_up_sem_queue_prepare(q, error): Prepare wake-up | |
685 | * @q: queue entry that must be signaled | |
686 | * @error: Error value for the signal | |
687 | * | |
688 | * Prepare the wake-up of the queue entry q. | |
689 | */ | |
690 | static void wake_up_sem_queue_prepare(struct list_head *pt, | |
691 | struct sem_queue *q, int error) | |
692 | { | |
693 | if (list_empty(pt)) { | |
694 | /* | |
695 | * Hold preempt off so that we don't get preempted and have the | |
696 | * wakee busy-wait until we're scheduled back on. | |
697 | */ | |
698 | preempt_disable(); | |
699 | } | |
700 | q->status = IN_WAKEUP; | |
701 | q->pid = error; | |
702 | ||
703 | list_add_tail(&q->list, pt); | |
704 | } | |
705 | ||
706 | /** | |
707 | * wake_up_sem_queue_do - do the actual wake-up | |
708 | * @pt: list of tasks to be woken up | |
709 | * | |
710 | * Do the actual wake-up. | |
711 | * The function is called without any locks held, thus the semaphore array | |
712 | * could be destroyed already and the tasks can disappear as soon as the | |
713 | * status is set to the actual return code. | |
714 | */ | |
715 | static void wake_up_sem_queue_do(struct list_head *pt) | |
716 | { | |
717 | struct sem_queue *q, *t; | |
718 | int did_something; | |
719 | ||
720 | did_something = !list_empty(pt); | |
721 | list_for_each_entry_safe(q, t, pt, list) { | |
722 | wake_up_process(q->sleeper); | |
723 | /* q can disappear immediately after writing q->status. */ | |
724 | smp_wmb(); | |
725 | q->status = q->pid; | |
726 | } | |
727 | if (did_something) | |
728 | preempt_enable(); | |
729 | } | |
730 | ||
731 | static void unlink_queue(struct sem_array *sma, struct sem_queue *q) | |
732 | { | |
733 | list_del(&q->list); | |
734 | if (q->nsops > 1) | |
735 | sma->complex_count--; | |
736 | } | |
737 | ||
738 | /** check_restart(sma, q) | |
739 | * @sma: semaphore array | |
740 | * @q: the operation that just completed | |
741 | * | |
742 | * update_queue is O(N^2) when it restarts scanning the whole queue of | |
743 | * waiting operations. Therefore this function checks if the restart is | |
744 | * really necessary. It is called after a previously waiting operation | |
745 | * modified the array. | |
746 | * Note that wait-for-zero operations are handled without restart. | |
747 | */ | |
748 | static int check_restart(struct sem_array *sma, struct sem_queue *q) | |
749 | { | |
750 | /* pending complex alter operations are too difficult to analyse */ | |
751 | if (!list_empty(&sma->pending_alter)) | |
752 | return 1; | |
753 | ||
754 | /* we were a sleeping complex operation. Too difficult */ | |
755 | if (q->nsops > 1) | |
756 | return 1; | |
757 | ||
758 | /* It is impossible that someone waits for the new value: | |
759 | * - complex operations always restart. | |
760 | * - wait-for-zero are handled seperately. | |
761 | * - q is a previously sleeping simple operation that | |
762 | * altered the array. It must be a decrement, because | |
763 | * simple increments never sleep. | |
764 | * - If there are older (higher priority) decrements | |
765 | * in the queue, then they have observed the original | |
766 | * semval value and couldn't proceed. The operation | |
767 | * decremented to value - thus they won't proceed either. | |
768 | */ | |
769 | return 0; | |
770 | } | |
771 | ||
772 | /** | |
773 | * wake_const_ops - wake up non-alter tasks | |
774 | * @sma: semaphore array. | |
775 | * @semnum: semaphore that was modified. | |
776 | * @pt: list head for the tasks that must be woken up. | |
777 | * | |
778 | * wake_const_ops must be called after a semaphore in a semaphore array | |
779 | * was set to 0. If complex const operations are pending, wake_const_ops must | |
780 | * be called with semnum = -1, as well as with the number of each modified | |
781 | * semaphore. | |
782 | * The tasks that must be woken up are added to @pt. The return code | |
783 | * is stored in q->pid. | |
784 | * The function returns 1 if at least one operation was completed successfully. | |
785 | */ | |
786 | static int wake_const_ops(struct sem_array *sma, int semnum, | |
787 | struct list_head *pt) | |
788 | { | |
789 | struct sem_queue *q; | |
790 | struct list_head *walk; | |
791 | struct list_head *pending_list; | |
792 | int semop_completed = 0; | |
793 | ||
794 | if (semnum == -1) | |
795 | pending_list = &sma->pending_const; | |
796 | else | |
797 | pending_list = &sma->sem_base[semnum].pending_const; | |
798 | ||
799 | walk = pending_list->next; | |
800 | while (walk != pending_list) { | |
801 | int error; | |
802 | ||
803 | q = container_of(walk, struct sem_queue, list); | |
804 | walk = walk->next; | |
805 | ||
806 | error = perform_atomic_semop(sma, q); | |
807 | ||
808 | if (error <= 0) { | |
809 | /* operation completed, remove from queue & wakeup */ | |
810 | ||
811 | unlink_queue(sma, q); | |
812 | ||
813 | wake_up_sem_queue_prepare(pt, q, error); | |
814 | if (error == 0) | |
815 | semop_completed = 1; | |
816 | } | |
817 | } | |
818 | return semop_completed; | |
819 | } | |
820 | ||
821 | /** | |
822 | * do_smart_wakeup_zero - wakeup all wait for zero tasks | |
823 | * @sma: semaphore array | |
824 | * @sops: operations that were performed | |
825 | * @nsops: number of operations | |
826 | * @pt: list head of the tasks that must be woken up. | |
827 | * | |
828 | * Checks all required queue for wait-for-zero operations, based | |
829 | * on the actual changes that were performed on the semaphore array. | |
830 | * The function returns 1 if at least one operation was completed successfully. | |
831 | */ | |
832 | static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops, | |
833 | int nsops, struct list_head *pt) | |
834 | { | |
835 | int i; | |
836 | int semop_completed = 0; | |
837 | int got_zero = 0; | |
838 | ||
839 | /* first: the per-semaphore queues, if known */ | |
840 | if (sops) { | |
841 | for (i = 0; i < nsops; i++) { | |
842 | int num = sops[i].sem_num; | |
843 | ||
844 | if (sma->sem_base[num].semval == 0) { | |
845 | got_zero = 1; | |
846 | semop_completed |= wake_const_ops(sma, num, pt); | |
847 | } | |
848 | } | |
849 | } else { | |
850 | /* | |
851 | * No sops means modified semaphores not known. | |
852 | * Assume all were changed. | |
853 | */ | |
854 | for (i = 0; i < sma->sem_nsems; i++) { | |
855 | if (sma->sem_base[i].semval == 0) { | |
856 | got_zero = 1; | |
857 | semop_completed |= wake_const_ops(sma, i, pt); | |
858 | } | |
859 | } | |
860 | } | |
861 | /* | |
862 | * If one of the modified semaphores got 0, | |
863 | * then check the global queue, too. | |
864 | */ | |
865 | if (got_zero) | |
866 | semop_completed |= wake_const_ops(sma, -1, pt); | |
867 | ||
868 | return semop_completed; | |
869 | } | |
870 | ||
871 | ||
872 | /** | |
873 | * update_queue - look for tasks that can be completed. | |
874 | * @sma: semaphore array. | |
875 | * @semnum: semaphore that was modified. | |
876 | * @pt: list head for the tasks that must be woken up. | |
877 | * | |
878 | * update_queue must be called after a semaphore in a semaphore array | |
879 | * was modified. If multiple semaphores were modified, update_queue must | |
880 | * be called with semnum = -1, as well as with the number of each modified | |
881 | * semaphore. | |
882 | * The tasks that must be woken up are added to @pt. The return code | |
883 | * is stored in q->pid. | |
884 | * The function internally checks if const operations can now succeed. | |
885 | * | |
886 | * The function return 1 if at least one semop was completed successfully. | |
887 | */ | |
888 | static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt) | |
889 | { | |
890 | struct sem_queue *q; | |
891 | struct list_head *walk; | |
892 | struct list_head *pending_list; | |
893 | int semop_completed = 0; | |
894 | ||
895 | if (semnum == -1) | |
896 | pending_list = &sma->pending_alter; | |
897 | else | |
898 | pending_list = &sma->sem_base[semnum].pending_alter; | |
899 | ||
900 | again: | |
901 | walk = pending_list->next; | |
902 | while (walk != pending_list) { | |
903 | int error, restart; | |
904 | ||
905 | q = container_of(walk, struct sem_queue, list); | |
906 | walk = walk->next; | |
907 | ||
908 | /* If we are scanning the single sop, per-semaphore list of | |
909 | * one semaphore and that semaphore is 0, then it is not | |
910 | * necessary to scan further: simple increments | |
911 | * that affect only one entry succeed immediately and cannot | |
912 | * be in the per semaphore pending queue, and decrements | |
913 | * cannot be successful if the value is already 0. | |
914 | */ | |
915 | if (semnum != -1 && sma->sem_base[semnum].semval == 0) | |
916 | break; | |
917 | ||
918 | error = perform_atomic_semop(sma, q); | |
919 | ||
920 | /* Does q->sleeper still need to sleep? */ | |
921 | if (error > 0) | |
922 | continue; | |
923 | ||
924 | unlink_queue(sma, q); | |
925 | ||
926 | if (error) { | |
927 | restart = 0; | |
928 | } else { | |
929 | semop_completed = 1; | |
930 | do_smart_wakeup_zero(sma, q->sops, q->nsops, pt); | |
931 | restart = check_restart(sma, q); | |
932 | } | |
933 | ||
934 | wake_up_sem_queue_prepare(pt, q, error); | |
935 | if (restart) | |
936 | goto again; | |
937 | } | |
938 | return semop_completed; | |
939 | } | |
940 | ||
941 | /** | |
942 | * set_semotime - set sem_otime | |
943 | * @sma: semaphore array | |
944 | * @sops: operations that modified the array, may be NULL | |
945 | * | |
946 | * sem_otime is replicated to avoid cache line trashing. | |
947 | * This function sets one instance to the current time. | |
948 | */ | |
949 | static void set_semotime(struct sem_array *sma, struct sembuf *sops) | |
950 | { | |
951 | if (sops == NULL) { | |
952 | sma->sem_base[0].sem_otime = get_seconds(); | |
953 | } else { | |
954 | sma->sem_base[sops[0].sem_num].sem_otime = | |
955 | get_seconds(); | |
956 | } | |
957 | } | |
958 | ||
959 | /** | |
960 | * do_smart_update - optimized update_queue | |
961 | * @sma: semaphore array | |
962 | * @sops: operations that were performed | |
963 | * @nsops: number of operations | |
964 | * @otime: force setting otime | |
965 | * @pt: list head of the tasks that must be woken up. | |
966 | * | |
967 | * do_smart_update() does the required calls to update_queue and wakeup_zero, | |
968 | * based on the actual changes that were performed on the semaphore array. | |
969 | * Note that the function does not do the actual wake-up: the caller is | |
970 | * responsible for calling wake_up_sem_queue_do(@pt). | |
971 | * It is safe to perform this call after dropping all locks. | |
972 | */ | |
973 | static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops, | |
974 | int otime, struct list_head *pt) | |
975 | { | |
976 | int i; | |
977 | ||
978 | otime |= do_smart_wakeup_zero(sma, sops, nsops, pt); | |
979 | ||
980 | if (!list_empty(&sma->pending_alter)) { | |
981 | /* semaphore array uses the global queue - just process it. */ | |
982 | otime |= update_queue(sma, -1, pt); | |
983 | } else { | |
984 | if (!sops) { | |
985 | /* | |
986 | * No sops, thus the modified semaphores are not | |
987 | * known. Check all. | |
988 | */ | |
989 | for (i = 0; i < sma->sem_nsems; i++) | |
990 | otime |= update_queue(sma, i, pt); | |
991 | } else { | |
992 | /* | |
993 | * Check the semaphores that were increased: | |
994 | * - No complex ops, thus all sleeping ops are | |
995 | * decrease. | |
996 | * - if we decreased the value, then any sleeping | |
997 | * semaphore ops wont be able to run: If the | |
998 | * previous value was too small, then the new | |
999 | * value will be too small, too. | |
1000 | */ | |
1001 | for (i = 0; i < nsops; i++) { | |
1002 | if (sops[i].sem_op > 0) { | |
1003 | otime |= update_queue(sma, | |
1004 | sops[i].sem_num, pt); | |
1005 | } | |
1006 | } | |
1007 | } | |
1008 | } | |
1009 | if (otime) | |
1010 | set_semotime(sma, sops); | |
1011 | } | |
1012 | ||
1013 | /* | |
1014 | * check_qop: Test if a queued operation sleeps on the semaphore semnum | |
1015 | */ | |
1016 | static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q, | |
1017 | bool count_zero) | |
1018 | { | |
1019 | struct sembuf *sop = q->blocking; | |
1020 | ||
1021 | /* | |
1022 | * Linux always (since 0.99.10) reported a task as sleeping on all | |
1023 | * semaphores. This violates SUS, therefore it was changed to the | |
1024 | * standard compliant behavior. | |
1025 | * Give the administrators a chance to notice that an application | |
1026 | * might misbehave because it relies on the Linux behavior. | |
1027 | */ | |
1028 | pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n" | |
1029 | "The task %s (%d) triggered the difference, watch for misbehavior.\n", | |
1030 | current->comm, task_pid_nr(current)); | |
1031 | ||
1032 | if (sop->sem_num != semnum) | |
1033 | return 0; | |
1034 | ||
1035 | if (count_zero && sop->sem_op == 0) | |
1036 | return 1; | |
1037 | if (!count_zero && sop->sem_op < 0) | |
1038 | return 1; | |
1039 | ||
1040 | return 0; | |
1041 | } | |
1042 | ||
1043 | /* The following counts are associated to each semaphore: | |
1044 | * semncnt number of tasks waiting on semval being nonzero | |
1045 | * semzcnt number of tasks waiting on semval being zero | |
1046 | * | |
1047 | * Per definition, a task waits only on the semaphore of the first semop | |
1048 | * that cannot proceed, even if additional operation would block, too. | |
1049 | */ | |
1050 | static int count_semcnt(struct sem_array *sma, ushort semnum, | |
1051 | bool count_zero) | |
1052 | { | |
1053 | struct list_head *l; | |
1054 | struct sem_queue *q; | |
1055 | int semcnt; | |
1056 | ||
1057 | semcnt = 0; | |
1058 | /* First: check the simple operations. They are easy to evaluate */ | |
1059 | if (count_zero) | |
1060 | l = &sma->sem_base[semnum].pending_const; | |
1061 | else | |
1062 | l = &sma->sem_base[semnum].pending_alter; | |
1063 | ||
1064 | list_for_each_entry(q, l, list) { | |
1065 | /* all task on a per-semaphore list sleep on exactly | |
1066 | * that semaphore | |
1067 | */ | |
1068 | semcnt++; | |
1069 | } | |
1070 | ||
1071 | /* Then: check the complex operations. */ | |
1072 | list_for_each_entry(q, &sma->pending_alter, list) { | |
1073 | semcnt += check_qop(sma, semnum, q, count_zero); | |
1074 | } | |
1075 | if (count_zero) { | |
1076 | list_for_each_entry(q, &sma->pending_const, list) { | |
1077 | semcnt += check_qop(sma, semnum, q, count_zero); | |
1078 | } | |
1079 | } | |
1080 | return semcnt; | |
1081 | } | |
1082 | ||
1083 | /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked | |
1084 | * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem | |
1085 | * remains locked on exit. | |
1086 | */ | |
1087 | static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) | |
1088 | { | |
1089 | struct sem_undo *un, *tu; | |
1090 | struct sem_queue *q, *tq; | |
1091 | struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); | |
1092 | struct list_head tasks; | |
1093 | int i; | |
1094 | ||
1095 | /* Free the existing undo structures for this semaphore set. */ | |
1096 | ipc_assert_locked_object(&sma->sem_perm); | |
1097 | list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { | |
1098 | list_del(&un->list_id); | |
1099 | spin_lock(&un->ulp->lock); | |
1100 | un->semid = -1; | |
1101 | list_del_rcu(&un->list_proc); | |
1102 | spin_unlock(&un->ulp->lock); | |
1103 | kfree_rcu(un, rcu); | |
1104 | } | |
1105 | ||
1106 | /* Wake up all pending processes and let them fail with EIDRM. */ | |
1107 | INIT_LIST_HEAD(&tasks); | |
1108 | list_for_each_entry_safe(q, tq, &sma->pending_const, list) { | |
1109 | unlink_queue(sma, q); | |
1110 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); | |
1111 | } | |
1112 | ||
1113 | list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { | |
1114 | unlink_queue(sma, q); | |
1115 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); | |
1116 | } | |
1117 | for (i = 0; i < sma->sem_nsems; i++) { | |
1118 | struct sem *sem = sma->sem_base + i; | |
1119 | list_for_each_entry_safe(q, tq, &sem->pending_const, list) { | |
1120 | unlink_queue(sma, q); | |
1121 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); | |
1122 | } | |
1123 | list_for_each_entry_safe(q, tq, &sem->pending_alter, list) { | |
1124 | unlink_queue(sma, q); | |
1125 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); | |
1126 | } | |
1127 | } | |
1128 | ||
1129 | /* Remove the semaphore set from the IDR */ | |
1130 | sem_rmid(ns, sma); | |
1131 | sem_unlock(sma, -1); | |
1132 | rcu_read_unlock(); | |
1133 | ||
1134 | wake_up_sem_queue_do(&tasks); | |
1135 | ns->used_sems -= sma->sem_nsems; | |
1136 | ipc_rcu_putref(sma, sem_rcu_free); | |
1137 | } | |
1138 | ||
1139 | static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) | |
1140 | { | |
1141 | switch (version) { | |
1142 | case IPC_64: | |
1143 | return copy_to_user(buf, in, sizeof(*in)); | |
1144 | case IPC_OLD: | |
1145 | { | |
1146 | struct semid_ds out; | |
1147 | ||
1148 | memset(&out, 0, sizeof(out)); | |
1149 | ||
1150 | ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); | |
1151 | ||
1152 | out.sem_otime = in->sem_otime; | |
1153 | out.sem_ctime = in->sem_ctime; | |
1154 | out.sem_nsems = in->sem_nsems; | |
1155 | ||
1156 | return copy_to_user(buf, &out, sizeof(out)); | |
1157 | } | |
1158 | default: | |
1159 | return -EINVAL; | |
1160 | } | |
1161 | } | |
1162 | ||
1163 | static time_t get_semotime(struct sem_array *sma) | |
1164 | { | |
1165 | int i; | |
1166 | time_t res; | |
1167 | ||
1168 | res = sma->sem_base[0].sem_otime; | |
1169 | for (i = 1; i < sma->sem_nsems; i++) { | |
1170 | time_t to = sma->sem_base[i].sem_otime; | |
1171 | ||
1172 | if (to > res) | |
1173 | res = to; | |
1174 | } | |
1175 | return res; | |
1176 | } | |
1177 | ||
1178 | static int semctl_nolock(struct ipc_namespace *ns, int semid, | |
1179 | int cmd, int version, void __user *p) | |
1180 | { | |
1181 | int err; | |
1182 | struct sem_array *sma; | |
1183 | ||
1184 | switch (cmd) { | |
1185 | case IPC_INFO: | |
1186 | case SEM_INFO: | |
1187 | { | |
1188 | struct seminfo seminfo; | |
1189 | int max_id; | |
1190 | ||
1191 | err = security_sem_semctl(NULL, cmd); | |
1192 | if (err) | |
1193 | return err; | |
1194 | ||
1195 | memset(&seminfo, 0, sizeof(seminfo)); | |
1196 | seminfo.semmni = ns->sc_semmni; | |
1197 | seminfo.semmns = ns->sc_semmns; | |
1198 | seminfo.semmsl = ns->sc_semmsl; | |
1199 | seminfo.semopm = ns->sc_semopm; | |
1200 | seminfo.semvmx = SEMVMX; | |
1201 | seminfo.semmnu = SEMMNU; | |
1202 | seminfo.semmap = SEMMAP; | |
1203 | seminfo.semume = SEMUME; | |
1204 | down_read(&sem_ids(ns).rwsem); | |
1205 | if (cmd == SEM_INFO) { | |
1206 | seminfo.semusz = sem_ids(ns).in_use; | |
1207 | seminfo.semaem = ns->used_sems; | |
1208 | } else { | |
1209 | seminfo.semusz = SEMUSZ; | |
1210 | seminfo.semaem = SEMAEM; | |
1211 | } | |
1212 | max_id = ipc_get_maxid(&sem_ids(ns)); | |
1213 | up_read(&sem_ids(ns).rwsem); | |
1214 | if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) | |
1215 | return -EFAULT; | |
1216 | return (max_id < 0) ? 0 : max_id; | |
1217 | } | |
1218 | case IPC_STAT: | |
1219 | case SEM_STAT: | |
1220 | { | |
1221 | struct semid64_ds tbuf; | |
1222 | int id = 0; | |
1223 | ||
1224 | memset(&tbuf, 0, sizeof(tbuf)); | |
1225 | ||
1226 | rcu_read_lock(); | |
1227 | if (cmd == SEM_STAT) { | |
1228 | sma = sem_obtain_object(ns, semid); | |
1229 | if (IS_ERR(sma)) { | |
1230 | err = PTR_ERR(sma); | |
1231 | goto out_unlock; | |
1232 | } | |
1233 | id = sma->sem_perm.id; | |
1234 | } else { | |
1235 | sma = sem_obtain_object_check(ns, semid); | |
1236 | if (IS_ERR(sma)) { | |
1237 | err = PTR_ERR(sma); | |
1238 | goto out_unlock; | |
1239 | } | |
1240 | } | |
1241 | ||
1242 | err = -EACCES; | |
1243 | if (ipcperms(ns, &sma->sem_perm, S_IRUGO)) | |
1244 | goto out_unlock; | |
1245 | ||
1246 | err = security_sem_semctl(sma, cmd); | |
1247 | if (err) | |
1248 | goto out_unlock; | |
1249 | ||
1250 | kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm); | |
1251 | tbuf.sem_otime = get_semotime(sma); | |
1252 | tbuf.sem_ctime = sma->sem_ctime; | |
1253 | tbuf.sem_nsems = sma->sem_nsems; | |
1254 | rcu_read_unlock(); | |
1255 | if (copy_semid_to_user(p, &tbuf, version)) | |
1256 | return -EFAULT; | |
1257 | return id; | |
1258 | } | |
1259 | default: | |
1260 | return -EINVAL; | |
1261 | } | |
1262 | out_unlock: | |
1263 | rcu_read_unlock(); | |
1264 | return err; | |
1265 | } | |
1266 | ||
1267 | static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, | |
1268 | unsigned long arg) | |
1269 | { | |
1270 | struct sem_undo *un; | |
1271 | struct sem_array *sma; | |
1272 | struct sem *curr; | |
1273 | int err; | |
1274 | struct list_head tasks; | |
1275 | int val; | |
1276 | #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN) | |
1277 | /* big-endian 64bit */ | |
1278 | val = arg >> 32; | |
1279 | #else | |
1280 | /* 32bit or little-endian 64bit */ | |
1281 | val = arg; | |
1282 | #endif | |
1283 | ||
1284 | if (val > SEMVMX || val < 0) | |
1285 | return -ERANGE; | |
1286 | ||
1287 | INIT_LIST_HEAD(&tasks); | |
1288 | ||
1289 | rcu_read_lock(); | |
1290 | sma = sem_obtain_object_check(ns, semid); | |
1291 | if (IS_ERR(sma)) { | |
1292 | rcu_read_unlock(); | |
1293 | return PTR_ERR(sma); | |
1294 | } | |
1295 | ||
1296 | if (semnum < 0 || semnum >= sma->sem_nsems) { | |
1297 | rcu_read_unlock(); | |
1298 | return -EINVAL; | |
1299 | } | |
1300 | ||
1301 | ||
1302 | if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) { | |
1303 | rcu_read_unlock(); | |
1304 | return -EACCES; | |
1305 | } | |
1306 | ||
1307 | err = security_sem_semctl(sma, SETVAL); | |
1308 | if (err) { | |
1309 | rcu_read_unlock(); | |
1310 | return -EACCES; | |
1311 | } | |
1312 | ||
1313 | sem_lock(sma, NULL, -1); | |
1314 | ||
1315 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1316 | sem_unlock(sma, -1); | |
1317 | rcu_read_unlock(); | |
1318 | return -EIDRM; | |
1319 | } | |
1320 | ||
1321 | curr = &sma->sem_base[semnum]; | |
1322 | ||
1323 | ipc_assert_locked_object(&sma->sem_perm); | |
1324 | list_for_each_entry(un, &sma->list_id, list_id) | |
1325 | un->semadj[semnum] = 0; | |
1326 | ||
1327 | curr->semval = val; | |
1328 | curr->sempid = task_tgid_vnr(current); | |
1329 | sma->sem_ctime = get_seconds(); | |
1330 | /* maybe some queued-up processes were waiting for this */ | |
1331 | do_smart_update(sma, NULL, 0, 0, &tasks); | |
1332 | sem_unlock(sma, -1); | |
1333 | rcu_read_unlock(); | |
1334 | wake_up_sem_queue_do(&tasks); | |
1335 | return 0; | |
1336 | } | |
1337 | ||
1338 | static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, | |
1339 | int cmd, void __user *p) | |
1340 | { | |
1341 | struct sem_array *sma; | |
1342 | struct sem *curr; | |
1343 | int err, nsems; | |
1344 | ushort fast_sem_io[SEMMSL_FAST]; | |
1345 | ushort *sem_io = fast_sem_io; | |
1346 | struct list_head tasks; | |
1347 | ||
1348 | INIT_LIST_HEAD(&tasks); | |
1349 | ||
1350 | rcu_read_lock(); | |
1351 | sma = sem_obtain_object_check(ns, semid); | |
1352 | if (IS_ERR(sma)) { | |
1353 | rcu_read_unlock(); | |
1354 | return PTR_ERR(sma); | |
1355 | } | |
1356 | ||
1357 | nsems = sma->sem_nsems; | |
1358 | ||
1359 | err = -EACCES; | |
1360 | if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO)) | |
1361 | goto out_rcu_wakeup; | |
1362 | ||
1363 | err = security_sem_semctl(sma, cmd); | |
1364 | if (err) | |
1365 | goto out_rcu_wakeup; | |
1366 | ||
1367 | err = -EACCES; | |
1368 | switch (cmd) { | |
1369 | case GETALL: | |
1370 | { | |
1371 | ushort __user *array = p; | |
1372 | int i; | |
1373 | ||
1374 | sem_lock(sma, NULL, -1); | |
1375 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1376 | err = -EIDRM; | |
1377 | goto out_unlock; | |
1378 | } | |
1379 | if (nsems > SEMMSL_FAST) { | |
1380 | if (!ipc_rcu_getref(sma)) { | |
1381 | err = -EIDRM; | |
1382 | goto out_unlock; | |
1383 | } | |
1384 | sem_unlock(sma, -1); | |
1385 | rcu_read_unlock(); | |
1386 | sem_io = ipc_alloc(sizeof(ushort)*nsems); | |
1387 | if (sem_io == NULL) { | |
1388 | ipc_rcu_putref(sma, ipc_rcu_free); | |
1389 | return -ENOMEM; | |
1390 | } | |
1391 | ||
1392 | rcu_read_lock(); | |
1393 | sem_lock_and_putref(sma); | |
1394 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1395 | err = -EIDRM; | |
1396 | goto out_unlock; | |
1397 | } | |
1398 | } | |
1399 | for (i = 0; i < sma->sem_nsems; i++) | |
1400 | sem_io[i] = sma->sem_base[i].semval; | |
1401 | sem_unlock(sma, -1); | |
1402 | rcu_read_unlock(); | |
1403 | err = 0; | |
1404 | if (copy_to_user(array, sem_io, nsems*sizeof(ushort))) | |
1405 | err = -EFAULT; | |
1406 | goto out_free; | |
1407 | } | |
1408 | case SETALL: | |
1409 | { | |
1410 | int i; | |
1411 | struct sem_undo *un; | |
1412 | ||
1413 | if (!ipc_rcu_getref(sma)) { | |
1414 | err = -EIDRM; | |
1415 | goto out_rcu_wakeup; | |
1416 | } | |
1417 | rcu_read_unlock(); | |
1418 | ||
1419 | if (nsems > SEMMSL_FAST) { | |
1420 | sem_io = ipc_alloc(sizeof(ushort)*nsems); | |
1421 | if (sem_io == NULL) { | |
1422 | ipc_rcu_putref(sma, ipc_rcu_free); | |
1423 | return -ENOMEM; | |
1424 | } | |
1425 | } | |
1426 | ||
1427 | if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) { | |
1428 | ipc_rcu_putref(sma, ipc_rcu_free); | |
1429 | err = -EFAULT; | |
1430 | goto out_free; | |
1431 | } | |
1432 | ||
1433 | for (i = 0; i < nsems; i++) { | |
1434 | if (sem_io[i] > SEMVMX) { | |
1435 | ipc_rcu_putref(sma, ipc_rcu_free); | |
1436 | err = -ERANGE; | |
1437 | goto out_free; | |
1438 | } | |
1439 | } | |
1440 | rcu_read_lock(); | |
1441 | sem_lock_and_putref(sma); | |
1442 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1443 | err = -EIDRM; | |
1444 | goto out_unlock; | |
1445 | } | |
1446 | ||
1447 | for (i = 0; i < nsems; i++) | |
1448 | sma->sem_base[i].semval = sem_io[i]; | |
1449 | ||
1450 | ipc_assert_locked_object(&sma->sem_perm); | |
1451 | list_for_each_entry(un, &sma->list_id, list_id) { | |
1452 | for (i = 0; i < nsems; i++) | |
1453 | un->semadj[i] = 0; | |
1454 | } | |
1455 | sma->sem_ctime = get_seconds(); | |
1456 | /* maybe some queued-up processes were waiting for this */ | |
1457 | do_smart_update(sma, NULL, 0, 0, &tasks); | |
1458 | err = 0; | |
1459 | goto out_unlock; | |
1460 | } | |
1461 | /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */ | |
1462 | } | |
1463 | err = -EINVAL; | |
1464 | if (semnum < 0 || semnum >= nsems) | |
1465 | goto out_rcu_wakeup; | |
1466 | ||
1467 | sem_lock(sma, NULL, -1); | |
1468 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1469 | err = -EIDRM; | |
1470 | goto out_unlock; | |
1471 | } | |
1472 | curr = &sma->sem_base[semnum]; | |
1473 | ||
1474 | switch (cmd) { | |
1475 | case GETVAL: | |
1476 | err = curr->semval; | |
1477 | goto out_unlock; | |
1478 | case GETPID: | |
1479 | err = curr->sempid; | |
1480 | goto out_unlock; | |
1481 | case GETNCNT: | |
1482 | err = count_semcnt(sma, semnum, 0); | |
1483 | goto out_unlock; | |
1484 | case GETZCNT: | |
1485 | err = count_semcnt(sma, semnum, 1); | |
1486 | goto out_unlock; | |
1487 | } | |
1488 | ||
1489 | out_unlock: | |
1490 | sem_unlock(sma, -1); | |
1491 | out_rcu_wakeup: | |
1492 | rcu_read_unlock(); | |
1493 | wake_up_sem_queue_do(&tasks); | |
1494 | out_free: | |
1495 | if (sem_io != fast_sem_io) | |
1496 | ipc_free(sem_io); | |
1497 | return err; | |
1498 | } | |
1499 | ||
1500 | static inline unsigned long | |
1501 | copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) | |
1502 | { | |
1503 | switch (version) { | |
1504 | case IPC_64: | |
1505 | if (copy_from_user(out, buf, sizeof(*out))) | |
1506 | return -EFAULT; | |
1507 | return 0; | |
1508 | case IPC_OLD: | |
1509 | { | |
1510 | struct semid_ds tbuf_old; | |
1511 | ||
1512 | if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) | |
1513 | return -EFAULT; | |
1514 | ||
1515 | out->sem_perm.uid = tbuf_old.sem_perm.uid; | |
1516 | out->sem_perm.gid = tbuf_old.sem_perm.gid; | |
1517 | out->sem_perm.mode = tbuf_old.sem_perm.mode; | |
1518 | ||
1519 | return 0; | |
1520 | } | |
1521 | default: | |
1522 | return -EINVAL; | |
1523 | } | |
1524 | } | |
1525 | ||
1526 | /* | |
1527 | * This function handles some semctl commands which require the rwsem | |
1528 | * to be held in write mode. | |
1529 | * NOTE: no locks must be held, the rwsem is taken inside this function. | |
1530 | */ | |
1531 | static int semctl_down(struct ipc_namespace *ns, int semid, | |
1532 | int cmd, int version, void __user *p) | |
1533 | { | |
1534 | struct sem_array *sma; | |
1535 | int err; | |
1536 | struct semid64_ds semid64; | |
1537 | struct kern_ipc_perm *ipcp; | |
1538 | ||
1539 | if (cmd == IPC_SET) { | |
1540 | if (copy_semid_from_user(&semid64, p, version)) | |
1541 | return -EFAULT; | |
1542 | } | |
1543 | ||
1544 | down_write(&sem_ids(ns).rwsem); | |
1545 | rcu_read_lock(); | |
1546 | ||
1547 | ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd, | |
1548 | &semid64.sem_perm, 0); | |
1549 | if (IS_ERR(ipcp)) { | |
1550 | err = PTR_ERR(ipcp); | |
1551 | goto out_unlock1; | |
1552 | } | |
1553 | ||
1554 | sma = container_of(ipcp, struct sem_array, sem_perm); | |
1555 | ||
1556 | err = security_sem_semctl(sma, cmd); | |
1557 | if (err) | |
1558 | goto out_unlock1; | |
1559 | ||
1560 | switch (cmd) { | |
1561 | case IPC_RMID: | |
1562 | sem_lock(sma, NULL, -1); | |
1563 | /* freeary unlocks the ipc object and rcu */ | |
1564 | freeary(ns, ipcp); | |
1565 | goto out_up; | |
1566 | case IPC_SET: | |
1567 | sem_lock(sma, NULL, -1); | |
1568 | err = ipc_update_perm(&semid64.sem_perm, ipcp); | |
1569 | if (err) | |
1570 | goto out_unlock0; | |
1571 | sma->sem_ctime = get_seconds(); | |
1572 | break; | |
1573 | default: | |
1574 | err = -EINVAL; | |
1575 | goto out_unlock1; | |
1576 | } | |
1577 | ||
1578 | out_unlock0: | |
1579 | sem_unlock(sma, -1); | |
1580 | out_unlock1: | |
1581 | rcu_read_unlock(); | |
1582 | out_up: | |
1583 | up_write(&sem_ids(ns).rwsem); | |
1584 | return err; | |
1585 | } | |
1586 | ||
1587 | SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) | |
1588 | { | |
1589 | int version; | |
1590 | struct ipc_namespace *ns; | |
1591 | void __user *p = (void __user *)arg; | |
1592 | ||
1593 | if (semid < 0) | |
1594 | return -EINVAL; | |
1595 | ||
1596 | version = ipc_parse_version(&cmd); | |
1597 | ns = current->nsproxy->ipc_ns; | |
1598 | ||
1599 | switch (cmd) { | |
1600 | case IPC_INFO: | |
1601 | case SEM_INFO: | |
1602 | case IPC_STAT: | |
1603 | case SEM_STAT: | |
1604 | return semctl_nolock(ns, semid, cmd, version, p); | |
1605 | case GETALL: | |
1606 | case GETVAL: | |
1607 | case GETPID: | |
1608 | case GETNCNT: | |
1609 | case GETZCNT: | |
1610 | case SETALL: | |
1611 | return semctl_main(ns, semid, semnum, cmd, p); | |
1612 | case SETVAL: | |
1613 | return semctl_setval(ns, semid, semnum, arg); | |
1614 | case IPC_RMID: | |
1615 | case IPC_SET: | |
1616 | return semctl_down(ns, semid, cmd, version, p); | |
1617 | default: | |
1618 | return -EINVAL; | |
1619 | } | |
1620 | } | |
1621 | ||
1622 | /* If the task doesn't already have a undo_list, then allocate one | |
1623 | * here. We guarantee there is only one thread using this undo list, | |
1624 | * and current is THE ONE | |
1625 | * | |
1626 | * If this allocation and assignment succeeds, but later | |
1627 | * portions of this code fail, there is no need to free the sem_undo_list. | |
1628 | * Just let it stay associated with the task, and it'll be freed later | |
1629 | * at exit time. | |
1630 | * | |
1631 | * This can block, so callers must hold no locks. | |
1632 | */ | |
1633 | static inline int get_undo_list(struct sem_undo_list **undo_listp) | |
1634 | { | |
1635 | struct sem_undo_list *undo_list; | |
1636 | ||
1637 | undo_list = current->sysvsem.undo_list; | |
1638 | if (!undo_list) { | |
1639 | undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL); | |
1640 | if (undo_list == NULL) | |
1641 | return -ENOMEM; | |
1642 | spin_lock_init(&undo_list->lock); | |
1643 | atomic_set(&undo_list->refcnt, 1); | |
1644 | INIT_LIST_HEAD(&undo_list->list_proc); | |
1645 | ||
1646 | current->sysvsem.undo_list = undo_list; | |
1647 | } | |
1648 | *undo_listp = undo_list; | |
1649 | return 0; | |
1650 | } | |
1651 | ||
1652 | static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) | |
1653 | { | |
1654 | struct sem_undo *un; | |
1655 | ||
1656 | list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) { | |
1657 | if (un->semid == semid) | |
1658 | return un; | |
1659 | } | |
1660 | return NULL; | |
1661 | } | |
1662 | ||
1663 | static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) | |
1664 | { | |
1665 | struct sem_undo *un; | |
1666 | ||
1667 | assert_spin_locked(&ulp->lock); | |
1668 | ||
1669 | un = __lookup_undo(ulp, semid); | |
1670 | if (un) { | |
1671 | list_del_rcu(&un->list_proc); | |
1672 | list_add_rcu(&un->list_proc, &ulp->list_proc); | |
1673 | } | |
1674 | return un; | |
1675 | } | |
1676 | ||
1677 | /** | |
1678 | * find_alloc_undo - lookup (and if not present create) undo array | |
1679 | * @ns: namespace | |
1680 | * @semid: semaphore array id | |
1681 | * | |
1682 | * The function looks up (and if not present creates) the undo structure. | |
1683 | * The size of the undo structure depends on the size of the semaphore | |
1684 | * array, thus the alloc path is not that straightforward. | |
1685 | * Lifetime-rules: sem_undo is rcu-protected, on success, the function | |
1686 | * performs a rcu_read_lock(). | |
1687 | */ | |
1688 | static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) | |
1689 | { | |
1690 | struct sem_array *sma; | |
1691 | struct sem_undo_list *ulp; | |
1692 | struct sem_undo *un, *new; | |
1693 | int nsems, error; | |
1694 | ||
1695 | error = get_undo_list(&ulp); | |
1696 | if (error) | |
1697 | return ERR_PTR(error); | |
1698 | ||
1699 | rcu_read_lock(); | |
1700 | spin_lock(&ulp->lock); | |
1701 | un = lookup_undo(ulp, semid); | |
1702 | spin_unlock(&ulp->lock); | |
1703 | if (likely(un != NULL)) | |
1704 | goto out; | |
1705 | ||
1706 | /* no undo structure around - allocate one. */ | |
1707 | /* step 1: figure out the size of the semaphore array */ | |
1708 | sma = sem_obtain_object_check(ns, semid); | |
1709 | if (IS_ERR(sma)) { | |
1710 | rcu_read_unlock(); | |
1711 | return ERR_CAST(sma); | |
1712 | } | |
1713 | ||
1714 | nsems = sma->sem_nsems; | |
1715 | if (!ipc_rcu_getref(sma)) { | |
1716 | rcu_read_unlock(); | |
1717 | un = ERR_PTR(-EIDRM); | |
1718 | goto out; | |
1719 | } | |
1720 | rcu_read_unlock(); | |
1721 | ||
1722 | /* step 2: allocate new undo structure */ | |
1723 | new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL); | |
1724 | if (!new) { | |
1725 | ipc_rcu_putref(sma, ipc_rcu_free); | |
1726 | return ERR_PTR(-ENOMEM); | |
1727 | } | |
1728 | ||
1729 | /* step 3: Acquire the lock on semaphore array */ | |
1730 | rcu_read_lock(); | |
1731 | sem_lock_and_putref(sma); | |
1732 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1733 | sem_unlock(sma, -1); | |
1734 | rcu_read_unlock(); | |
1735 | kfree(new); | |
1736 | un = ERR_PTR(-EIDRM); | |
1737 | goto out; | |
1738 | } | |
1739 | spin_lock(&ulp->lock); | |
1740 | ||
1741 | /* | |
1742 | * step 4: check for races: did someone else allocate the undo struct? | |
1743 | */ | |
1744 | un = lookup_undo(ulp, semid); | |
1745 | if (un) { | |
1746 | kfree(new); | |
1747 | goto success; | |
1748 | } | |
1749 | /* step 5: initialize & link new undo structure */ | |
1750 | new->semadj = (short *) &new[1]; | |
1751 | new->ulp = ulp; | |
1752 | new->semid = semid; | |
1753 | assert_spin_locked(&ulp->lock); | |
1754 | list_add_rcu(&new->list_proc, &ulp->list_proc); | |
1755 | ipc_assert_locked_object(&sma->sem_perm); | |
1756 | list_add(&new->list_id, &sma->list_id); | |
1757 | un = new; | |
1758 | ||
1759 | success: | |
1760 | spin_unlock(&ulp->lock); | |
1761 | sem_unlock(sma, -1); | |
1762 | out: | |
1763 | return un; | |
1764 | } | |
1765 | ||
1766 | ||
1767 | /** | |
1768 | * get_queue_result - retrieve the result code from sem_queue | |
1769 | * @q: Pointer to queue structure | |
1770 | * | |
1771 | * Retrieve the return code from the pending queue. If IN_WAKEUP is found in | |
1772 | * q->status, then we must loop until the value is replaced with the final | |
1773 | * value: This may happen if a task is woken up by an unrelated event (e.g. | |
1774 | * signal) and in parallel the task is woken up by another task because it got | |
1775 | * the requested semaphores. | |
1776 | * | |
1777 | * The function can be called with or without holding the semaphore spinlock. | |
1778 | */ | |
1779 | static int get_queue_result(struct sem_queue *q) | |
1780 | { | |
1781 | int error; | |
1782 | ||
1783 | error = q->status; | |
1784 | while (unlikely(error == IN_WAKEUP)) { | |
1785 | cpu_relax(); | |
1786 | error = q->status; | |
1787 | } | |
1788 | ||
1789 | return error; | |
1790 | } | |
1791 | ||
1792 | SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, | |
1793 | unsigned, nsops, const struct timespec __user *, timeout) | |
1794 | { | |
1795 | int error = -EINVAL; | |
1796 | struct sem_array *sma; | |
1797 | struct sembuf fast_sops[SEMOPM_FAST]; | |
1798 | struct sembuf *sops = fast_sops, *sop; | |
1799 | struct sem_undo *un; | |
1800 | int undos = 0, alter = 0, max, locknum; | |
1801 | struct sem_queue queue; | |
1802 | unsigned long jiffies_left = 0; | |
1803 | struct ipc_namespace *ns; | |
1804 | struct list_head tasks; | |
1805 | ||
1806 | ns = current->nsproxy->ipc_ns; | |
1807 | ||
1808 | if (nsops < 1 || semid < 0) | |
1809 | return -EINVAL; | |
1810 | if (nsops > ns->sc_semopm) | |
1811 | return -E2BIG; | |
1812 | if (nsops > SEMOPM_FAST) { | |
1813 | sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL); | |
1814 | if (sops == NULL) | |
1815 | return -ENOMEM; | |
1816 | } | |
1817 | if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) { | |
1818 | error = -EFAULT; | |
1819 | goto out_free; | |
1820 | } | |
1821 | if (timeout) { | |
1822 | struct timespec _timeout; | |
1823 | if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) { | |
1824 | error = -EFAULT; | |
1825 | goto out_free; | |
1826 | } | |
1827 | if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 || | |
1828 | _timeout.tv_nsec >= 1000000000L) { | |
1829 | error = -EINVAL; | |
1830 | goto out_free; | |
1831 | } | |
1832 | jiffies_left = timespec_to_jiffies(&_timeout); | |
1833 | } | |
1834 | max = 0; | |
1835 | for (sop = sops; sop < sops + nsops; sop++) { | |
1836 | if (sop->sem_num >= max) | |
1837 | max = sop->sem_num; | |
1838 | if (sop->sem_flg & SEM_UNDO) | |
1839 | undos = 1; | |
1840 | if (sop->sem_op != 0) | |
1841 | alter = 1; | |
1842 | } | |
1843 | ||
1844 | INIT_LIST_HEAD(&tasks); | |
1845 | ||
1846 | if (undos) { | |
1847 | /* On success, find_alloc_undo takes the rcu_read_lock */ | |
1848 | un = find_alloc_undo(ns, semid); | |
1849 | if (IS_ERR(un)) { | |
1850 | error = PTR_ERR(un); | |
1851 | goto out_free; | |
1852 | } | |
1853 | } else { | |
1854 | un = NULL; | |
1855 | rcu_read_lock(); | |
1856 | } | |
1857 | ||
1858 | sma = sem_obtain_object_check(ns, semid); | |
1859 | if (IS_ERR(sma)) { | |
1860 | rcu_read_unlock(); | |
1861 | error = PTR_ERR(sma); | |
1862 | goto out_free; | |
1863 | } | |
1864 | ||
1865 | error = -EFBIG; | |
1866 | if (max >= sma->sem_nsems) | |
1867 | goto out_rcu_wakeup; | |
1868 | ||
1869 | error = -EACCES; | |
1870 | if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) | |
1871 | goto out_rcu_wakeup; | |
1872 | ||
1873 | error = security_sem_semop(sma, sops, nsops, alter); | |
1874 | if (error) | |
1875 | goto out_rcu_wakeup; | |
1876 | ||
1877 | error = -EIDRM; | |
1878 | locknum = sem_lock(sma, sops, nsops); | |
1879 | /* | |
1880 | * We eventually might perform the following check in a lockless | |
1881 | * fashion, considering ipc_valid_object() locking constraints. | |
1882 | * If nsops == 1 and there is no contention for sem_perm.lock, then | |
1883 | * only a per-semaphore lock is held and it's OK to proceed with the | |
1884 | * check below. More details on the fine grained locking scheme | |
1885 | * entangled here and why it's RMID race safe on comments at sem_lock() | |
1886 | */ | |
1887 | if (!ipc_valid_object(&sma->sem_perm)) | |
1888 | goto out_unlock_free; | |
1889 | /* | |
1890 | * semid identifiers are not unique - find_alloc_undo may have | |
1891 | * allocated an undo structure, it was invalidated by an RMID | |
1892 | * and now a new array with received the same id. Check and fail. | |
1893 | * This case can be detected checking un->semid. The existence of | |
1894 | * "un" itself is guaranteed by rcu. | |
1895 | */ | |
1896 | if (un && un->semid == -1) | |
1897 | goto out_unlock_free; | |
1898 | ||
1899 | queue.sops = sops; | |
1900 | queue.nsops = nsops; | |
1901 | queue.undo = un; | |
1902 | queue.pid = task_tgid_vnr(current); | |
1903 | queue.alter = alter; | |
1904 | ||
1905 | error = perform_atomic_semop(sma, &queue); | |
1906 | if (error == 0) { | |
1907 | /* If the operation was successful, then do | |
1908 | * the required updates. | |
1909 | */ | |
1910 | if (alter) | |
1911 | do_smart_update(sma, sops, nsops, 1, &tasks); | |
1912 | else | |
1913 | set_semotime(sma, sops); | |
1914 | } | |
1915 | if (error <= 0) | |
1916 | goto out_unlock_free; | |
1917 | ||
1918 | /* We need to sleep on this operation, so we put the current | |
1919 | * task into the pending queue and go to sleep. | |
1920 | */ | |
1921 | ||
1922 | if (nsops == 1) { | |
1923 | struct sem *curr; | |
1924 | curr = &sma->sem_base[sops->sem_num]; | |
1925 | ||
1926 | if (alter) { | |
1927 | if (sma->complex_count) { | |
1928 | list_add_tail(&queue.list, | |
1929 | &sma->pending_alter); | |
1930 | } else { | |
1931 | ||
1932 | list_add_tail(&queue.list, | |
1933 | &curr->pending_alter); | |
1934 | } | |
1935 | } else { | |
1936 | list_add_tail(&queue.list, &curr->pending_const); | |
1937 | } | |
1938 | } else { | |
1939 | if (!sma->complex_count) | |
1940 | merge_queues(sma); | |
1941 | ||
1942 | if (alter) | |
1943 | list_add_tail(&queue.list, &sma->pending_alter); | |
1944 | else | |
1945 | list_add_tail(&queue.list, &sma->pending_const); | |
1946 | ||
1947 | sma->complex_count++; | |
1948 | } | |
1949 | ||
1950 | queue.status = -EINTR; | |
1951 | queue.sleeper = current; | |
1952 | ||
1953 | sleep_again: | |
1954 | __set_current_state(TASK_INTERRUPTIBLE); | |
1955 | sem_unlock(sma, locknum); | |
1956 | rcu_read_unlock(); | |
1957 | ||
1958 | if (timeout) | |
1959 | jiffies_left = schedule_timeout(jiffies_left); | |
1960 | else | |
1961 | schedule(); | |
1962 | ||
1963 | error = get_queue_result(&queue); | |
1964 | ||
1965 | if (error != -EINTR) { | |
1966 | /* fast path: update_queue already obtained all requested | |
1967 | * resources. | |
1968 | * Perform a smp_mb(): User space could assume that semop() | |
1969 | * is a memory barrier: Without the mb(), the cpu could | |
1970 | * speculatively read in user space stale data that was | |
1971 | * overwritten by the previous owner of the semaphore. | |
1972 | */ | |
1973 | smp_mb(); | |
1974 | ||
1975 | goto out_free; | |
1976 | } | |
1977 | ||
1978 | rcu_read_lock(); | |
1979 | sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum); | |
1980 | ||
1981 | /* | |
1982 | * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing. | |
1983 | */ | |
1984 | error = get_queue_result(&queue); | |
1985 | ||
1986 | /* | |
1987 | * Array removed? If yes, leave without sem_unlock(). | |
1988 | */ | |
1989 | if (IS_ERR(sma)) { | |
1990 | rcu_read_unlock(); | |
1991 | goto out_free; | |
1992 | } | |
1993 | ||
1994 | ||
1995 | /* | |
1996 | * If queue.status != -EINTR we are woken up by another process. | |
1997 | * Leave without unlink_queue(), but with sem_unlock(). | |
1998 | */ | |
1999 | if (error != -EINTR) | |
2000 | goto out_unlock_free; | |
2001 | ||
2002 | /* | |
2003 | * If an interrupt occurred we have to clean up the queue | |
2004 | */ | |
2005 | if (timeout && jiffies_left == 0) | |
2006 | error = -EAGAIN; | |
2007 | ||
2008 | /* | |
2009 | * If the wakeup was spurious, just retry | |
2010 | */ | |
2011 | if (error == -EINTR && !signal_pending(current)) | |
2012 | goto sleep_again; | |
2013 | ||
2014 | unlink_queue(sma, &queue); | |
2015 | ||
2016 | out_unlock_free: | |
2017 | sem_unlock(sma, locknum); | |
2018 | out_rcu_wakeup: | |
2019 | rcu_read_unlock(); | |
2020 | wake_up_sem_queue_do(&tasks); | |
2021 | out_free: | |
2022 | if (sops != fast_sops) | |
2023 | kfree(sops); | |
2024 | return error; | |
2025 | } | |
2026 | ||
2027 | SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, | |
2028 | unsigned, nsops) | |
2029 | { | |
2030 | return sys_semtimedop(semid, tsops, nsops, NULL); | |
2031 | } | |
2032 | ||
2033 | /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between | |
2034 | * parent and child tasks. | |
2035 | */ | |
2036 | ||
2037 | int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) | |
2038 | { | |
2039 | struct sem_undo_list *undo_list; | |
2040 | int error; | |
2041 | ||
2042 | if (clone_flags & CLONE_SYSVSEM) { | |
2043 | error = get_undo_list(&undo_list); | |
2044 | if (error) | |
2045 | return error; | |
2046 | atomic_inc(&undo_list->refcnt); | |
2047 | tsk->sysvsem.undo_list = undo_list; | |
2048 | } else | |
2049 | tsk->sysvsem.undo_list = NULL; | |
2050 | ||
2051 | return 0; | |
2052 | } | |
2053 | ||
2054 | /* | |
2055 | * add semadj values to semaphores, free undo structures. | |
2056 | * undo structures are not freed when semaphore arrays are destroyed | |
2057 | * so some of them may be out of date. | |
2058 | * IMPLEMENTATION NOTE: There is some confusion over whether the | |
2059 | * set of adjustments that needs to be done should be done in an atomic | |
2060 | * manner or not. That is, if we are attempting to decrement the semval | |
2061 | * should we queue up and wait until we can do so legally? | |
2062 | * The original implementation attempted to do this (queue and wait). | |
2063 | * The current implementation does not do so. The POSIX standard | |
2064 | * and SVID should be consulted to determine what behavior is mandated. | |
2065 | */ | |
2066 | void exit_sem(struct task_struct *tsk) | |
2067 | { | |
2068 | struct sem_undo_list *ulp; | |
2069 | ||
2070 | ulp = tsk->sysvsem.undo_list; | |
2071 | if (!ulp) | |
2072 | return; | |
2073 | tsk->sysvsem.undo_list = NULL; | |
2074 | ||
2075 | if (!atomic_dec_and_test(&ulp->refcnt)) | |
2076 | return; | |
2077 | ||
2078 | for (;;) { | |
2079 | struct sem_array *sma; | |
2080 | struct sem_undo *un; | |
2081 | struct list_head tasks; | |
2082 | int semid, i; | |
2083 | ||
2084 | rcu_read_lock(); | |
2085 | un = list_entry_rcu(ulp->list_proc.next, | |
2086 | struct sem_undo, list_proc); | |
2087 | if (&un->list_proc == &ulp->list_proc) { | |
2088 | /* | |
2089 | * We must wait for freeary() before freeing this ulp, | |
2090 | * in case we raced with last sem_undo. There is a small | |
2091 | * possibility where we exit while freeary() didn't | |
2092 | * finish unlocking sem_undo_list. | |
2093 | */ | |
2094 | spin_unlock_wait(&ulp->lock); | |
2095 | rcu_read_unlock(); | |
2096 | break; | |
2097 | } | |
2098 | spin_lock(&ulp->lock); | |
2099 | semid = un->semid; | |
2100 | spin_unlock(&ulp->lock); | |
2101 | ||
2102 | /* exit_sem raced with IPC_RMID, nothing to do */ | |
2103 | if (semid == -1) { | |
2104 | rcu_read_unlock(); | |
2105 | continue; | |
2106 | } | |
2107 | ||
2108 | sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid); | |
2109 | /* exit_sem raced with IPC_RMID, nothing to do */ | |
2110 | if (IS_ERR(sma)) { | |
2111 | rcu_read_unlock(); | |
2112 | continue; | |
2113 | } | |
2114 | ||
2115 | sem_lock(sma, NULL, -1); | |
2116 | /* exit_sem raced with IPC_RMID, nothing to do */ | |
2117 | if (!ipc_valid_object(&sma->sem_perm)) { | |
2118 | sem_unlock(sma, -1); | |
2119 | rcu_read_unlock(); | |
2120 | continue; | |
2121 | } | |
2122 | un = __lookup_undo(ulp, semid); | |
2123 | if (un == NULL) { | |
2124 | /* exit_sem raced with IPC_RMID+semget() that created | |
2125 | * exactly the same semid. Nothing to do. | |
2126 | */ | |
2127 | sem_unlock(sma, -1); | |
2128 | rcu_read_unlock(); | |
2129 | continue; | |
2130 | } | |
2131 | ||
2132 | /* remove un from the linked lists */ | |
2133 | ipc_assert_locked_object(&sma->sem_perm); | |
2134 | list_del(&un->list_id); | |
2135 | ||
2136 | /* we are the last process using this ulp, acquiring ulp->lock | |
2137 | * isn't required. Besides that, we are also protected against | |
2138 | * IPC_RMID as we hold sma->sem_perm lock now | |
2139 | */ | |
2140 | list_del_rcu(&un->list_proc); | |
2141 | ||
2142 | /* perform adjustments registered in un */ | |
2143 | for (i = 0; i < sma->sem_nsems; i++) { | |
2144 | struct sem *semaphore = &sma->sem_base[i]; | |
2145 | if (un->semadj[i]) { | |
2146 | semaphore->semval += un->semadj[i]; | |
2147 | /* | |
2148 | * Range checks of the new semaphore value, | |
2149 | * not defined by sus: | |
2150 | * - Some unices ignore the undo entirely | |
2151 | * (e.g. HP UX 11i 11.22, Tru64 V5.1) | |
2152 | * - some cap the value (e.g. FreeBSD caps | |
2153 | * at 0, but doesn't enforce SEMVMX) | |
2154 | * | |
2155 | * Linux caps the semaphore value, both at 0 | |
2156 | * and at SEMVMX. | |
2157 | * | |
2158 | * Manfred <manfred@colorfullife.com> | |
2159 | */ | |
2160 | if (semaphore->semval < 0) | |
2161 | semaphore->semval = 0; | |
2162 | if (semaphore->semval > SEMVMX) | |
2163 | semaphore->semval = SEMVMX; | |
2164 | semaphore->sempid = task_tgid_vnr(current); | |
2165 | } | |
2166 | } | |
2167 | /* maybe some queued-up processes were waiting for this */ | |
2168 | INIT_LIST_HEAD(&tasks); | |
2169 | do_smart_update(sma, NULL, 0, 1, &tasks); | |
2170 | sem_unlock(sma, -1); | |
2171 | rcu_read_unlock(); | |
2172 | wake_up_sem_queue_do(&tasks); | |
2173 | ||
2174 | kfree_rcu(un, rcu); | |
2175 | } | |
2176 | kfree(ulp); | |
2177 | } | |
2178 | ||
2179 | #ifdef CONFIG_PROC_FS | |
2180 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it) | |
2181 | { | |
2182 | struct user_namespace *user_ns = seq_user_ns(s); | |
2183 | struct sem_array *sma = it; | |
2184 | time_t sem_otime; | |
2185 | ||
2186 | /* | |
2187 | * The proc interface isn't aware of sem_lock(), it calls | |
2188 | * ipc_lock_object() directly (in sysvipc_find_ipc). | |
2189 | * In order to stay compatible with sem_lock(), we must wait until | |
2190 | * all simple semop() calls have left their critical regions. | |
2191 | */ | |
2192 | sem_wait_array(sma); | |
2193 | ||
2194 | sem_otime = get_semotime(sma); | |
2195 | ||
2196 | seq_printf(s, | |
2197 | "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n", | |
2198 | sma->sem_perm.key, | |
2199 | sma->sem_perm.id, | |
2200 | sma->sem_perm.mode, | |
2201 | sma->sem_nsems, | |
2202 | from_kuid_munged(user_ns, sma->sem_perm.uid), | |
2203 | from_kgid_munged(user_ns, sma->sem_perm.gid), | |
2204 | from_kuid_munged(user_ns, sma->sem_perm.cuid), | |
2205 | from_kgid_munged(user_ns, sma->sem_perm.cgid), | |
2206 | sem_otime, | |
2207 | sma->sem_ctime); | |
2208 | ||
2209 | return 0; | |
2210 | } | |
2211 | #endif |