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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 | * (c) 2016 Davidlohr Bueso <dave@stgolabs.net> | |
15 | * Further wakeup optimizations, documentation | |
16 | * (c) 2010 Manfred Spraul <manfred@colorfullife.com> | |
17 | * | |
18 | * support for audit of ipc object properties and permission changes | |
19 | * Dustin Kirkland <dustin.kirkland@us.ibm.com> | |
20 | * | |
21 | * namespaces support | |
22 | * OpenVZ, SWsoft Inc. | |
23 | * Pavel Emelianov <xemul@openvz.org> | |
24 | * | |
25 | * Implementation notes: (May 2010) | |
26 | * This file implements System V semaphores. | |
27 | * | |
28 | * User space visible behavior: | |
29 | * - FIFO ordering for semop() operations (just FIFO, not starvation | |
30 | * protection) | |
31 | * - multiple semaphore operations that alter the same semaphore in | |
32 | * one semop() are handled. | |
33 | * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and | |
34 | * SETALL calls. | |
35 | * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO. | |
36 | * - undo adjustments at process exit are limited to 0..SEMVMX. | |
37 | * - namespace are supported. | |
38 | * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing | |
39 | * to /proc/sys/kernel/sem. | |
40 | * - statistics about the usage are reported in /proc/sysvipc/sem. | |
41 | * | |
42 | * Internals: | |
43 | * - scalability: | |
44 | * - all global variables are read-mostly. | |
45 | * - semop() calls and semctl(RMID) are synchronized by RCU. | |
46 | * - most operations do write operations (actually: spin_lock calls) to | |
47 | * the per-semaphore array structure. | |
48 | * Thus: Perfect SMP scaling between independent semaphore arrays. | |
49 | * If multiple semaphores in one array are used, then cache line | |
50 | * trashing on the semaphore array spinlock will limit the scaling. | |
51 | * - semncnt and semzcnt are calculated on demand in count_semcnt() | |
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 | * - 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 | * - UNDO values are stored in an array (one per process and per | |
63 | * semaphore array, lazily allocated). For backwards compatibility, multiple | |
64 | * modes for the UNDO variables are supported (per process, per thread) | |
65 | * (see copy_semundo, CLONE_SYSVSEM) | |
66 | * - There are two lists of the pending operations: a per-array list | |
67 | * and per-semaphore list (stored in the array). This allows to achieve FIFO | |
68 | * ordering without always scanning all pending operations. | |
69 | * The worst-case behavior is nevertheless O(N^2) for N wakeups. | |
70 | */ | |
71 | ||
72 | #include <linux/slab.h> | |
73 | #include <linux/spinlock.h> | |
74 | #include <linux/init.h> | |
75 | #include <linux/proc_fs.h> | |
76 | #include <linux/time.h> | |
77 | #include <linux/security.h> | |
78 | #include <linux/syscalls.h> | |
79 | #include <linux/audit.h> | |
80 | #include <linux/capability.h> | |
81 | #include <linux/seq_file.h> | |
82 | #include <linux/rwsem.h> | |
83 | #include <linux/nsproxy.h> | |
84 | #include <linux/ipc_namespace.h> | |
85 | ||
86 | #include <linux/uaccess.h> | |
87 | #include "util.h" | |
88 | ||
89 | /* One semaphore structure for each semaphore in the system. */ | |
90 | struct sem { | |
91 | int semval; /* current value */ | |
92 | /* | |
93 | * PID of the process that last modified the semaphore. For | |
94 | * Linux, specifically these are: | |
95 | * - semop | |
96 | * - semctl, via SETVAL and SETALL. | |
97 | * - at task exit when performing undo adjustments (see exit_sem). | |
98 | */ | |
99 | int sempid; | |
100 | spinlock_t lock; /* spinlock for fine-grained semtimedop */ | |
101 | struct list_head pending_alter; /* pending single-sop operations */ | |
102 | /* that alter the semaphore */ | |
103 | struct list_head pending_const; /* pending single-sop operations */ | |
104 | /* that do not alter the semaphore*/ | |
105 | time_t sem_otime; /* candidate for sem_otime */ | |
106 | } ____cacheline_aligned_in_smp; | |
107 | ||
108 | /* One queue for each sleeping process in the system. */ | |
109 | struct sem_queue { | |
110 | struct list_head list; /* queue of pending operations */ | |
111 | struct task_struct *sleeper; /* this process */ | |
112 | struct sem_undo *undo; /* undo structure */ | |
113 | int pid; /* process id of requesting process */ | |
114 | int status; /* completion status of operation */ | |
115 | struct sembuf *sops; /* array of pending operations */ | |
116 | struct sembuf *blocking; /* the operation that blocked */ | |
117 | int nsops; /* number of operations */ | |
118 | bool alter; /* does *sops alter the array? */ | |
119 | bool dupsop; /* sops on more than one sem_num */ | |
120 | }; | |
121 | ||
122 | /* Each task has a list of undo requests. They are executed automatically | |
123 | * when the process exits. | |
124 | */ | |
125 | struct sem_undo { | |
126 | struct list_head list_proc; /* per-process list: * | |
127 | * all undos from one process | |
128 | * rcu protected */ | |
129 | struct rcu_head rcu; /* rcu struct for sem_undo */ | |
130 | struct sem_undo_list *ulp; /* back ptr to sem_undo_list */ | |
131 | struct list_head list_id; /* per semaphore array list: | |
132 | * all undos for one array */ | |
133 | int semid; /* semaphore set identifier */ | |
134 | short *semadj; /* array of adjustments */ | |
135 | /* one per semaphore */ | |
136 | }; | |
137 | ||
138 | /* sem_undo_list controls shared access to the list of sem_undo structures | |
139 | * that may be shared among all a CLONE_SYSVSEM task group. | |
140 | */ | |
141 | struct sem_undo_list { | |
142 | atomic_t refcnt; | |
143 | spinlock_t lock; | |
144 | struct list_head list_proc; | |
145 | }; | |
146 | ||
147 | ||
148 | #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS]) | |
149 | ||
150 | #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid) | |
151 | ||
152 | static int newary(struct ipc_namespace *, struct ipc_params *); | |
153 | static void freeary(struct ipc_namespace *, struct kern_ipc_perm *); | |
154 | #ifdef CONFIG_PROC_FS | |
155 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it); | |
156 | #endif | |
157 | ||
158 | #define SEMMSL_FAST 256 /* 512 bytes on stack */ | |
159 | #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ | |
160 | ||
161 | /* | |
162 | * Locking: | |
163 | * a) global sem_lock() for read/write | |
164 | * sem_undo.id_next, | |
165 | * sem_array.complex_count, | |
166 | * sem_array.complex_mode | |
167 | * sem_array.pending{_alter,_const}, | |
168 | * sem_array.sem_undo | |
169 | * | |
170 | * b) global or semaphore sem_lock() for read/write: | |
171 | * sem_array.sem_base[i].pending_{const,alter}: | |
172 | * sem_array.complex_mode (for read) | |
173 | * | |
174 | * c) special: | |
175 | * sem_undo_list.list_proc: | |
176 | * * undo_list->lock for write | |
177 | * * rcu for read | |
178 | */ | |
179 | ||
180 | #define sc_semmsl sem_ctls[0] | |
181 | #define sc_semmns sem_ctls[1] | |
182 | #define sc_semopm sem_ctls[2] | |
183 | #define sc_semmni sem_ctls[3] | |
184 | ||
185 | void sem_init_ns(struct ipc_namespace *ns) | |
186 | { | |
187 | ns->sc_semmsl = SEMMSL; | |
188 | ns->sc_semmns = SEMMNS; | |
189 | ns->sc_semopm = SEMOPM; | |
190 | ns->sc_semmni = SEMMNI; | |
191 | ns->used_sems = 0; | |
192 | ipc_init_ids(&ns->ids[IPC_SEM_IDS]); | |
193 | } | |
194 | ||
195 | #ifdef CONFIG_IPC_NS | |
196 | void sem_exit_ns(struct ipc_namespace *ns) | |
197 | { | |
198 | free_ipcs(ns, &sem_ids(ns), freeary); | |
199 | idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr); | |
200 | } | |
201 | #endif | |
202 | ||
203 | void __init sem_init(void) | |
204 | { | |
205 | sem_init_ns(&init_ipc_ns); | |
206 | ipc_init_proc_interface("sysvipc/sem", | |
207 | " key semid perms nsems uid gid cuid cgid otime ctime\n", | |
208 | IPC_SEM_IDS, sysvipc_sem_proc_show); | |
209 | } | |
210 | ||
211 | /** | |
212 | * unmerge_queues - unmerge queues, if possible. | |
213 | * @sma: semaphore array | |
214 | * | |
215 | * The function unmerges the wait queues if complex_count is 0. | |
216 | * It must be called prior to dropping the global semaphore array lock. | |
217 | */ | |
218 | static void unmerge_queues(struct sem_array *sma) | |
219 | { | |
220 | struct sem_queue *q, *tq; | |
221 | ||
222 | /* complex operations still around? */ | |
223 | if (sma->complex_count) | |
224 | return; | |
225 | /* | |
226 | * We will switch back to simple mode. | |
227 | * Move all pending operation back into the per-semaphore | |
228 | * queues. | |
229 | */ | |
230 | list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { | |
231 | struct sem *curr; | |
232 | curr = &sma->sem_base[q->sops[0].sem_num]; | |
233 | ||
234 | list_add_tail(&q->list, &curr->pending_alter); | |
235 | } | |
236 | INIT_LIST_HEAD(&sma->pending_alter); | |
237 | } | |
238 | ||
239 | /** | |
240 | * merge_queues - merge single semop queues into global queue | |
241 | * @sma: semaphore array | |
242 | * | |
243 | * This function merges all per-semaphore queues into the global queue. | |
244 | * It is necessary to achieve FIFO ordering for the pending single-sop | |
245 | * operations when a multi-semop operation must sleep. | |
246 | * Only the alter operations must be moved, the const operations can stay. | |
247 | */ | |
248 | static void merge_queues(struct sem_array *sma) | |
249 | { | |
250 | int i; | |
251 | for (i = 0; i < sma->sem_nsems; i++) { | |
252 | struct sem *sem = sma->sem_base + i; | |
253 | ||
254 | list_splice_init(&sem->pending_alter, &sma->pending_alter); | |
255 | } | |
256 | } | |
257 | ||
258 | static void sem_rcu_free(struct rcu_head *head) | |
259 | { | |
260 | struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu); | |
261 | struct sem_array *sma = ipc_rcu_to_struct(p); | |
262 | ||
263 | security_sem_free(sma); | |
264 | ipc_rcu_free(head); | |
265 | } | |
266 | ||
267 | /* | |
268 | * Enter the mode suitable for non-simple operations: | |
269 | * Caller must own sem_perm.lock. | |
270 | */ | |
271 | static void complexmode_enter(struct sem_array *sma) | |
272 | { | |
273 | int i; | |
274 | struct sem *sem; | |
275 | ||
276 | if (sma->complex_mode) { | |
277 | /* We are already in complex_mode. Nothing to do */ | |
278 | return; | |
279 | } | |
280 | ||
281 | /* We need a full barrier after seting complex_mode: | |
282 | * The write to complex_mode must be visible | |
283 | * before we read the first sem->lock spinlock state. | |
284 | */ | |
285 | smp_store_mb(sma->complex_mode, true); | |
286 | ||
287 | for (i = 0; i < sma->sem_nsems; i++) { | |
288 | sem = sma->sem_base + i; | |
289 | spin_unlock_wait(&sem->lock); | |
290 | } | |
291 | /* | |
292 | * spin_unlock_wait() is not a memory barriers, it is only a | |
293 | * control barrier. The code must pair with spin_unlock(&sem->lock), | |
294 | * thus just the control barrier is insufficient. | |
295 | * | |
296 | * smp_rmb() is sufficient, as writes cannot pass the control barrier. | |
297 | */ | |
298 | smp_rmb(); | |
299 | } | |
300 | ||
301 | /* | |
302 | * Try to leave the mode that disallows simple operations: | |
303 | * Caller must own sem_perm.lock. | |
304 | */ | |
305 | static void complexmode_tryleave(struct sem_array *sma) | |
306 | { | |
307 | if (sma->complex_count) { | |
308 | /* Complex ops are sleeping. | |
309 | * We must stay in complex mode | |
310 | */ | |
311 | return; | |
312 | } | |
313 | /* | |
314 | * Immediately after setting complex_mode to false, | |
315 | * a simple op can start. Thus: all memory writes | |
316 | * performed by the current operation must be visible | |
317 | * before we set complex_mode to false. | |
318 | */ | |
319 | smp_store_release(&sma->complex_mode, false); | |
320 | } | |
321 | ||
322 | #define SEM_GLOBAL_LOCK (-1) | |
323 | /* | |
324 | * If the request contains only one semaphore operation, and there are | |
325 | * no complex transactions pending, lock only the semaphore involved. | |
326 | * Otherwise, lock the entire semaphore array, since we either have | |
327 | * multiple semaphores in our own semops, or we need to look at | |
328 | * semaphores from other pending complex operations. | |
329 | */ | |
330 | static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, | |
331 | int nsops) | |
332 | { | |
333 | struct sem *sem; | |
334 | ||
335 | if (nsops != 1) { | |
336 | /* Complex operation - acquire a full lock */ | |
337 | ipc_lock_object(&sma->sem_perm); | |
338 | ||
339 | /* Prevent parallel simple ops */ | |
340 | complexmode_enter(sma); | |
341 | return SEM_GLOBAL_LOCK; | |
342 | } | |
343 | ||
344 | /* | |
345 | * Only one semaphore affected - try to optimize locking. | |
346 | * Optimized locking is possible if no complex operation | |
347 | * is either enqueued or processed right now. | |
348 | * | |
349 | * Both facts are tracked by complex_mode. | |
350 | */ | |
351 | sem = sma->sem_base + sops->sem_num; | |
352 | ||
353 | /* | |
354 | * Initial check for complex_mode. Just an optimization, | |
355 | * no locking, no memory barrier. | |
356 | */ | |
357 | if (!sma->complex_mode) { | |
358 | /* | |
359 | * It appears that no complex operation is around. | |
360 | * Acquire the per-semaphore lock. | |
361 | */ | |
362 | spin_lock(&sem->lock); | |
363 | ||
364 | /* | |
365 | * See 51d7d5205d33 | |
366 | * ("powerpc: Add smp_mb() to arch_spin_is_locked()"): | |
367 | * A full barrier is required: the write of sem->lock | |
368 | * must be visible before the read is executed | |
369 | */ | |
370 | smp_mb(); | |
371 | ||
372 | if (!smp_load_acquire(&sma->complex_mode)) { | |
373 | /* fast path successful! */ | |
374 | return sops->sem_num; | |
375 | } | |
376 | spin_unlock(&sem->lock); | |
377 | } | |
378 | ||
379 | /* slow path: acquire the full lock */ | |
380 | ipc_lock_object(&sma->sem_perm); | |
381 | ||
382 | if (sma->complex_count == 0) { | |
383 | /* False alarm: | |
384 | * There is no complex operation, thus we can switch | |
385 | * back to the fast path. | |
386 | */ | |
387 | spin_lock(&sem->lock); | |
388 | ipc_unlock_object(&sma->sem_perm); | |
389 | return sops->sem_num; | |
390 | } else { | |
391 | /* Not a false alarm, thus complete the sequence for a | |
392 | * full lock. | |
393 | */ | |
394 | complexmode_enter(sma); | |
395 | return SEM_GLOBAL_LOCK; | |
396 | } | |
397 | } | |
398 | ||
399 | static inline void sem_unlock(struct sem_array *sma, int locknum) | |
400 | { | |
401 | if (locknum == SEM_GLOBAL_LOCK) { | |
402 | unmerge_queues(sma); | |
403 | complexmode_tryleave(sma); | |
404 | ipc_unlock_object(&sma->sem_perm); | |
405 | } else { | |
406 | struct sem *sem = sma->sem_base + locknum; | |
407 | spin_unlock(&sem->lock); | |
408 | } | |
409 | } | |
410 | ||
411 | /* | |
412 | * sem_lock_(check_) routines are called in the paths where the rwsem | |
413 | * is not held. | |
414 | * | |
415 | * The caller holds the RCU read lock. | |
416 | */ | |
417 | static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) | |
418 | { | |
419 | struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id); | |
420 | ||
421 | if (IS_ERR(ipcp)) | |
422 | return ERR_CAST(ipcp); | |
423 | ||
424 | return container_of(ipcp, struct sem_array, sem_perm); | |
425 | } | |
426 | ||
427 | static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns, | |
428 | int id) | |
429 | { | |
430 | struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id); | |
431 | ||
432 | if (IS_ERR(ipcp)) | |
433 | return ERR_CAST(ipcp); | |
434 | ||
435 | return container_of(ipcp, struct sem_array, sem_perm); | |
436 | } | |
437 | ||
438 | static inline void sem_lock_and_putref(struct sem_array *sma) | |
439 | { | |
440 | sem_lock(sma, NULL, -1); | |
441 | ipc_rcu_putref(sma, sem_rcu_free); | |
442 | } | |
443 | ||
444 | static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) | |
445 | { | |
446 | ipc_rmid(&sem_ids(ns), &s->sem_perm); | |
447 | } | |
448 | ||
449 | /** | |
450 | * newary - Create a new semaphore set | |
451 | * @ns: namespace | |
452 | * @params: ptr to the structure that contains key, semflg and nsems | |
453 | * | |
454 | * Called with sem_ids.rwsem held (as a writer) | |
455 | */ | |
456 | static int newary(struct ipc_namespace *ns, struct ipc_params *params) | |
457 | { | |
458 | int id; | |
459 | int retval; | |
460 | struct sem_array *sma; | |
461 | int size; | |
462 | key_t key = params->key; | |
463 | int nsems = params->u.nsems; | |
464 | int semflg = params->flg; | |
465 | int i; | |
466 | ||
467 | if (!nsems) | |
468 | return -EINVAL; | |
469 | if (ns->used_sems + nsems > ns->sc_semmns) | |
470 | return -ENOSPC; | |
471 | ||
472 | size = sizeof(*sma) + nsems * sizeof(struct sem); | |
473 | sma = ipc_rcu_alloc(size); | |
474 | if (!sma) | |
475 | return -ENOMEM; | |
476 | ||
477 | memset(sma, 0, size); | |
478 | ||
479 | sma->sem_perm.mode = (semflg & S_IRWXUGO); | |
480 | sma->sem_perm.key = key; | |
481 | ||
482 | sma->sem_perm.security = NULL; | |
483 | retval = security_sem_alloc(sma); | |
484 | if (retval) { | |
485 | ipc_rcu_putref(sma, ipc_rcu_free); | |
486 | return retval; | |
487 | } | |
488 | ||
489 | sma->sem_base = (struct sem *) &sma[1]; | |
490 | ||
491 | for (i = 0; i < nsems; i++) { | |
492 | INIT_LIST_HEAD(&sma->sem_base[i].pending_alter); | |
493 | INIT_LIST_HEAD(&sma->sem_base[i].pending_const); | |
494 | spin_lock_init(&sma->sem_base[i].lock); | |
495 | } | |
496 | ||
497 | sma->complex_count = 0; | |
498 | sma->complex_mode = true; /* dropped by sem_unlock below */ | |
499 | INIT_LIST_HEAD(&sma->pending_alter); | |
500 | INIT_LIST_HEAD(&sma->pending_const); | |
501 | INIT_LIST_HEAD(&sma->list_id); | |
502 | sma->sem_nsems = nsems; | |
503 | sma->sem_ctime = get_seconds(); | |
504 | ||
505 | id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); | |
506 | if (id < 0) { | |
507 | ipc_rcu_putref(sma, sem_rcu_free); | |
508 | return id; | |
509 | } | |
510 | ns->used_sems += nsems; | |
511 | ||
512 | sem_unlock(sma, -1); | |
513 | rcu_read_unlock(); | |
514 | ||
515 | return sma->sem_perm.id; | |
516 | } | |
517 | ||
518 | ||
519 | /* | |
520 | * Called with sem_ids.rwsem and ipcp locked. | |
521 | */ | |
522 | static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg) | |
523 | { | |
524 | struct sem_array *sma; | |
525 | ||
526 | sma = container_of(ipcp, struct sem_array, sem_perm); | |
527 | return security_sem_associate(sma, semflg); | |
528 | } | |
529 | ||
530 | /* | |
531 | * Called with sem_ids.rwsem and ipcp locked. | |
532 | */ | |
533 | static inline int sem_more_checks(struct kern_ipc_perm *ipcp, | |
534 | struct ipc_params *params) | |
535 | { | |
536 | struct sem_array *sma; | |
537 | ||
538 | sma = container_of(ipcp, struct sem_array, sem_perm); | |
539 | if (params->u.nsems > sma->sem_nsems) | |
540 | return -EINVAL; | |
541 | ||
542 | return 0; | |
543 | } | |
544 | ||
545 | SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) | |
546 | { | |
547 | struct ipc_namespace *ns; | |
548 | static const struct ipc_ops sem_ops = { | |
549 | .getnew = newary, | |
550 | .associate = sem_security, | |
551 | .more_checks = sem_more_checks, | |
552 | }; | |
553 | struct ipc_params sem_params; | |
554 | ||
555 | ns = current->nsproxy->ipc_ns; | |
556 | ||
557 | if (nsems < 0 || nsems > ns->sc_semmsl) | |
558 | return -EINVAL; | |
559 | ||
560 | sem_params.key = key; | |
561 | sem_params.flg = semflg; | |
562 | sem_params.u.nsems = nsems; | |
563 | ||
564 | return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); | |
565 | } | |
566 | ||
567 | /** | |
568 | * perform_atomic_semop[_slow] - Attempt to perform semaphore | |
569 | * operations on a given array. | |
570 | * @sma: semaphore array | |
571 | * @q: struct sem_queue that describes the operation | |
572 | * | |
573 | * Caller blocking are as follows, based the value | |
574 | * indicated by the semaphore operation (sem_op): | |
575 | * | |
576 | * (1) >0 never blocks. | |
577 | * (2) 0 (wait-for-zero operation): semval is non-zero. | |
578 | * (3) <0 attempting to decrement semval to a value smaller than zero. | |
579 | * | |
580 | * Returns 0 if the operation was possible. | |
581 | * Returns 1 if the operation is impossible, the caller must sleep. | |
582 | * Returns <0 for error codes. | |
583 | */ | |
584 | static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q) | |
585 | { | |
586 | int result, sem_op, nsops, pid; | |
587 | struct sembuf *sop; | |
588 | struct sem *curr; | |
589 | struct sembuf *sops; | |
590 | struct sem_undo *un; | |
591 | ||
592 | sops = q->sops; | |
593 | nsops = q->nsops; | |
594 | un = q->undo; | |
595 | ||
596 | for (sop = sops; sop < sops + nsops; sop++) { | |
597 | curr = sma->sem_base + sop->sem_num; | |
598 | sem_op = sop->sem_op; | |
599 | result = curr->semval; | |
600 | ||
601 | if (!sem_op && result) | |
602 | goto would_block; | |
603 | ||
604 | result += sem_op; | |
605 | if (result < 0) | |
606 | goto would_block; | |
607 | if (result > SEMVMX) | |
608 | goto out_of_range; | |
609 | ||
610 | if (sop->sem_flg & SEM_UNDO) { | |
611 | int undo = un->semadj[sop->sem_num] - sem_op; | |
612 | /* Exceeding the undo range is an error. */ | |
613 | if (undo < (-SEMAEM - 1) || undo > SEMAEM) | |
614 | goto out_of_range; | |
615 | un->semadj[sop->sem_num] = undo; | |
616 | } | |
617 | ||
618 | curr->semval = result; | |
619 | } | |
620 | ||
621 | sop--; | |
622 | pid = q->pid; | |
623 | while (sop >= sops) { | |
624 | sma->sem_base[sop->sem_num].sempid = pid; | |
625 | sop--; | |
626 | } | |
627 | ||
628 | return 0; | |
629 | ||
630 | out_of_range: | |
631 | result = -ERANGE; | |
632 | goto undo; | |
633 | ||
634 | would_block: | |
635 | q->blocking = sop; | |
636 | ||
637 | if (sop->sem_flg & IPC_NOWAIT) | |
638 | result = -EAGAIN; | |
639 | else | |
640 | result = 1; | |
641 | ||
642 | undo: | |
643 | sop--; | |
644 | while (sop >= sops) { | |
645 | sem_op = sop->sem_op; | |
646 | sma->sem_base[sop->sem_num].semval -= sem_op; | |
647 | if (sop->sem_flg & SEM_UNDO) | |
648 | un->semadj[sop->sem_num] += sem_op; | |
649 | sop--; | |
650 | } | |
651 | ||
652 | return result; | |
653 | } | |
654 | ||
655 | static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q) | |
656 | { | |
657 | int result, sem_op, nsops; | |
658 | struct sembuf *sop; | |
659 | struct sem *curr; | |
660 | struct sembuf *sops; | |
661 | struct sem_undo *un; | |
662 | ||
663 | sops = q->sops; | |
664 | nsops = q->nsops; | |
665 | un = q->undo; | |
666 | ||
667 | if (unlikely(q->dupsop)) | |
668 | return perform_atomic_semop_slow(sma, q); | |
669 | ||
670 | /* | |
671 | * We scan the semaphore set twice, first to ensure that the entire | |
672 | * operation can succeed, therefore avoiding any pointless writes | |
673 | * to shared memory and having to undo such changes in order to block | |
674 | * until the operations can go through. | |
675 | */ | |
676 | for (sop = sops; sop < sops + nsops; sop++) { | |
677 | curr = sma->sem_base + sop->sem_num; | |
678 | sem_op = sop->sem_op; | |
679 | result = curr->semval; | |
680 | ||
681 | if (!sem_op && result) | |
682 | goto would_block; /* wait-for-zero */ | |
683 | ||
684 | result += sem_op; | |
685 | if (result < 0) | |
686 | goto would_block; | |
687 | ||
688 | if (result > SEMVMX) | |
689 | return -ERANGE; | |
690 | ||
691 | if (sop->sem_flg & SEM_UNDO) { | |
692 | int undo = un->semadj[sop->sem_num] - sem_op; | |
693 | ||
694 | /* Exceeding the undo range is an error. */ | |
695 | if (undo < (-SEMAEM - 1) || undo > SEMAEM) | |
696 | return -ERANGE; | |
697 | } | |
698 | } | |
699 | ||
700 | for (sop = sops; sop < sops + nsops; sop++) { | |
701 | curr = sma->sem_base + sop->sem_num; | |
702 | sem_op = sop->sem_op; | |
703 | result = curr->semval; | |
704 | ||
705 | if (sop->sem_flg & SEM_UNDO) { | |
706 | int undo = un->semadj[sop->sem_num] - sem_op; | |
707 | ||
708 | un->semadj[sop->sem_num] = undo; | |
709 | } | |
710 | curr->semval += sem_op; | |
711 | curr->sempid = q->pid; | |
712 | } | |
713 | ||
714 | return 0; | |
715 | ||
716 | would_block: | |
717 | q->blocking = sop; | |
718 | return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1; | |
719 | } | |
720 | ||
721 | static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error, | |
722 | struct wake_q_head *wake_q) | |
723 | { | |
724 | wake_q_add(wake_q, q->sleeper); | |
725 | /* | |
726 | * Rely on the above implicit barrier, such that we can | |
727 | * ensure that we hold reference to the task before setting | |
728 | * q->status. Otherwise we could race with do_exit if the | |
729 | * task is awoken by an external event before calling | |
730 | * wake_up_process(). | |
731 | */ | |
732 | WRITE_ONCE(q->status, error); | |
733 | } | |
734 | ||
735 | static void unlink_queue(struct sem_array *sma, struct sem_queue *q) | |
736 | { | |
737 | list_del(&q->list); | |
738 | if (q->nsops > 1) | |
739 | sma->complex_count--; | |
740 | } | |
741 | ||
742 | /** check_restart(sma, q) | |
743 | * @sma: semaphore array | |
744 | * @q: the operation that just completed | |
745 | * | |
746 | * update_queue is O(N^2) when it restarts scanning the whole queue of | |
747 | * waiting operations. Therefore this function checks if the restart is | |
748 | * really necessary. It is called after a previously waiting operation | |
749 | * modified the array. | |
750 | * Note that wait-for-zero operations are handled without restart. | |
751 | */ | |
752 | static inline int check_restart(struct sem_array *sma, struct sem_queue *q) | |
753 | { | |
754 | /* pending complex alter operations are too difficult to analyse */ | |
755 | if (!list_empty(&sma->pending_alter)) | |
756 | return 1; | |
757 | ||
758 | /* we were a sleeping complex operation. Too difficult */ | |
759 | if (q->nsops > 1) | |
760 | return 1; | |
761 | ||
762 | /* It is impossible that someone waits for the new value: | |
763 | * - complex operations always restart. | |
764 | * - wait-for-zero are handled seperately. | |
765 | * - q is a previously sleeping simple operation that | |
766 | * altered the array. It must be a decrement, because | |
767 | * simple increments never sleep. | |
768 | * - If there are older (higher priority) decrements | |
769 | * in the queue, then they have observed the original | |
770 | * semval value and couldn't proceed. The operation | |
771 | * decremented to value - thus they won't proceed either. | |
772 | */ | |
773 | return 0; | |
774 | } | |
775 | ||
776 | /** | |
777 | * wake_const_ops - wake up non-alter tasks | |
778 | * @sma: semaphore array. | |
779 | * @semnum: semaphore that was modified. | |
780 | * @wake_q: lockless wake-queue head. | |
781 | * | |
782 | * wake_const_ops must be called after a semaphore in a semaphore array | |
783 | * was set to 0. If complex const operations are pending, wake_const_ops must | |
784 | * be called with semnum = -1, as well as with the number of each modified | |
785 | * semaphore. | |
786 | * The tasks that must be woken up are added to @wake_q. The return code | |
787 | * is stored in q->pid. | |
788 | * The function returns 1 if at least one operation was completed successfully. | |
789 | */ | |
790 | static int wake_const_ops(struct sem_array *sma, int semnum, | |
791 | struct wake_q_head *wake_q) | |
792 | { | |
793 | struct sem_queue *q, *tmp; | |
794 | struct list_head *pending_list; | |
795 | int semop_completed = 0; | |
796 | ||
797 | if (semnum == -1) | |
798 | pending_list = &sma->pending_const; | |
799 | else | |
800 | pending_list = &sma->sem_base[semnum].pending_const; | |
801 | ||
802 | list_for_each_entry_safe(q, tmp, pending_list, list) { | |
803 | int error = perform_atomic_semop(sma, q); | |
804 | ||
805 | if (error > 0) | |
806 | continue; | |
807 | /* operation completed, remove from queue & wakeup */ | |
808 | unlink_queue(sma, q); | |
809 | ||
810 | wake_up_sem_queue_prepare(q, error, wake_q); | |
811 | if (error == 0) | |
812 | semop_completed = 1; | |
813 | } | |
814 | ||
815 | return semop_completed; | |
816 | } | |
817 | ||
818 | /** | |
819 | * do_smart_wakeup_zero - wakeup all wait for zero tasks | |
820 | * @sma: semaphore array | |
821 | * @sops: operations that were performed | |
822 | * @nsops: number of operations | |
823 | * @wake_q: lockless wake-queue head | |
824 | * | |
825 | * Checks all required queue for wait-for-zero operations, based | |
826 | * on the actual changes that were performed on the semaphore array. | |
827 | * The function returns 1 if at least one operation was completed successfully. | |
828 | */ | |
829 | static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops, | |
830 | int nsops, struct wake_q_head *wake_q) | |
831 | { | |
832 | int i; | |
833 | int semop_completed = 0; | |
834 | int got_zero = 0; | |
835 | ||
836 | /* first: the per-semaphore queues, if known */ | |
837 | if (sops) { | |
838 | for (i = 0; i < nsops; i++) { | |
839 | int num = sops[i].sem_num; | |
840 | ||
841 | if (sma->sem_base[num].semval == 0) { | |
842 | got_zero = 1; | |
843 | semop_completed |= wake_const_ops(sma, num, wake_q); | |
844 | } | |
845 | } | |
846 | } else { | |
847 | /* | |
848 | * No sops means modified semaphores not known. | |
849 | * Assume all were changed. | |
850 | */ | |
851 | for (i = 0; i < sma->sem_nsems; i++) { | |
852 | if (sma->sem_base[i].semval == 0) { | |
853 | got_zero = 1; | |
854 | semop_completed |= wake_const_ops(sma, i, wake_q); | |
855 | } | |
856 | } | |
857 | } | |
858 | /* | |
859 | * If one of the modified semaphores got 0, | |
860 | * then check the global queue, too. | |
861 | */ | |
862 | if (got_zero) | |
863 | semop_completed |= wake_const_ops(sma, -1, wake_q); | |
864 | ||
865 | return semop_completed; | |
866 | } | |
867 | ||
868 | ||
869 | /** | |
870 | * update_queue - look for tasks that can be completed. | |
871 | * @sma: semaphore array. | |
872 | * @semnum: semaphore that was modified. | |
873 | * @wake_q: lockless wake-queue head. | |
874 | * | |
875 | * update_queue must be called after a semaphore in a semaphore array | |
876 | * was modified. If multiple semaphores were modified, update_queue must | |
877 | * be called with semnum = -1, as well as with the number of each modified | |
878 | * semaphore. | |
879 | * The tasks that must be woken up are added to @wake_q. The return code | |
880 | * is stored in q->pid. | |
881 | * The function internally checks if const operations can now succeed. | |
882 | * | |
883 | * The function return 1 if at least one semop was completed successfully. | |
884 | */ | |
885 | static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q) | |
886 | { | |
887 | struct sem_queue *q, *tmp; | |
888 | struct list_head *pending_list; | |
889 | int semop_completed = 0; | |
890 | ||
891 | if (semnum == -1) | |
892 | pending_list = &sma->pending_alter; | |
893 | else | |
894 | pending_list = &sma->sem_base[semnum].pending_alter; | |
895 | ||
896 | again: | |
897 | list_for_each_entry_safe(q, tmp, pending_list, list) { | |
898 | int error, restart; | |
899 | ||
900 | /* If we are scanning the single sop, per-semaphore list of | |
901 | * one semaphore and that semaphore is 0, then it is not | |
902 | * necessary to scan further: simple increments | |
903 | * that affect only one entry succeed immediately and cannot | |
904 | * be in the per semaphore pending queue, and decrements | |
905 | * cannot be successful if the value is already 0. | |
906 | */ | |
907 | if (semnum != -1 && sma->sem_base[semnum].semval == 0) | |
908 | break; | |
909 | ||
910 | error = perform_atomic_semop(sma, q); | |
911 | ||
912 | /* Does q->sleeper still need to sleep? */ | |
913 | if (error > 0) | |
914 | continue; | |
915 | ||
916 | unlink_queue(sma, q); | |
917 | ||
918 | if (error) { | |
919 | restart = 0; | |
920 | } else { | |
921 | semop_completed = 1; | |
922 | do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q); | |
923 | restart = check_restart(sma, q); | |
924 | } | |
925 | ||
926 | wake_up_sem_queue_prepare(q, error, wake_q); | |
927 | if (restart) | |
928 | goto again; | |
929 | } | |
930 | return semop_completed; | |
931 | } | |
932 | ||
933 | /** | |
934 | * set_semotime - set sem_otime | |
935 | * @sma: semaphore array | |
936 | * @sops: operations that modified the array, may be NULL | |
937 | * | |
938 | * sem_otime is replicated to avoid cache line trashing. | |
939 | * This function sets one instance to the current time. | |
940 | */ | |
941 | static void set_semotime(struct sem_array *sma, struct sembuf *sops) | |
942 | { | |
943 | if (sops == NULL) { | |
944 | sma->sem_base[0].sem_otime = get_seconds(); | |
945 | } else { | |
946 | sma->sem_base[sops[0].sem_num].sem_otime = | |
947 | get_seconds(); | |
948 | } | |
949 | } | |
950 | ||
951 | /** | |
952 | * do_smart_update - optimized update_queue | |
953 | * @sma: semaphore array | |
954 | * @sops: operations that were performed | |
955 | * @nsops: number of operations | |
956 | * @otime: force setting otime | |
957 | * @wake_q: lockless wake-queue head | |
958 | * | |
959 | * do_smart_update() does the required calls to update_queue and wakeup_zero, | |
960 | * based on the actual changes that were performed on the semaphore array. | |
961 | * Note that the function does not do the actual wake-up: the caller is | |
962 | * responsible for calling wake_up_q(). | |
963 | * It is safe to perform this call after dropping all locks. | |
964 | */ | |
965 | static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops, | |
966 | int otime, struct wake_q_head *wake_q) | |
967 | { | |
968 | int i; | |
969 | ||
970 | otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q); | |
971 | ||
972 | if (!list_empty(&sma->pending_alter)) { | |
973 | /* semaphore array uses the global queue - just process it. */ | |
974 | otime |= update_queue(sma, -1, wake_q); | |
975 | } else { | |
976 | if (!sops) { | |
977 | /* | |
978 | * No sops, thus the modified semaphores are not | |
979 | * known. Check all. | |
980 | */ | |
981 | for (i = 0; i < sma->sem_nsems; i++) | |
982 | otime |= update_queue(sma, i, wake_q); | |
983 | } else { | |
984 | /* | |
985 | * Check the semaphores that were increased: | |
986 | * - No complex ops, thus all sleeping ops are | |
987 | * decrease. | |
988 | * - if we decreased the value, then any sleeping | |
989 | * semaphore ops wont be able to run: If the | |
990 | * previous value was too small, then the new | |
991 | * value will be too small, too. | |
992 | */ | |
993 | for (i = 0; i < nsops; i++) { | |
994 | if (sops[i].sem_op > 0) { | |
995 | otime |= update_queue(sma, | |
996 | sops[i].sem_num, wake_q); | |
997 | } | |
998 | } | |
999 | } | |
1000 | } | |
1001 | if (otime) | |
1002 | set_semotime(sma, sops); | |
1003 | } | |
1004 | ||
1005 | /* | |
1006 | * check_qop: Test if a queued operation sleeps on the semaphore semnum | |
1007 | */ | |
1008 | static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q, | |
1009 | bool count_zero) | |
1010 | { | |
1011 | struct sembuf *sop = q->blocking; | |
1012 | ||
1013 | /* | |
1014 | * Linux always (since 0.99.10) reported a task as sleeping on all | |
1015 | * semaphores. This violates SUS, therefore it was changed to the | |
1016 | * standard compliant behavior. | |
1017 | * Give the administrators a chance to notice that an application | |
1018 | * might misbehave because it relies on the Linux behavior. | |
1019 | */ | |
1020 | pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n" | |
1021 | "The task %s (%d) triggered the difference, watch for misbehavior.\n", | |
1022 | current->comm, task_pid_nr(current)); | |
1023 | ||
1024 | if (sop->sem_num != semnum) | |
1025 | return 0; | |
1026 | ||
1027 | if (count_zero && sop->sem_op == 0) | |
1028 | return 1; | |
1029 | if (!count_zero && sop->sem_op < 0) | |
1030 | return 1; | |
1031 | ||
1032 | return 0; | |
1033 | } | |
1034 | ||
1035 | /* The following counts are associated to each semaphore: | |
1036 | * semncnt number of tasks waiting on semval being nonzero | |
1037 | * semzcnt number of tasks waiting on semval being zero | |
1038 | * | |
1039 | * Per definition, a task waits only on the semaphore of the first semop | |
1040 | * that cannot proceed, even if additional operation would block, too. | |
1041 | */ | |
1042 | static int count_semcnt(struct sem_array *sma, ushort semnum, | |
1043 | bool count_zero) | |
1044 | { | |
1045 | struct list_head *l; | |
1046 | struct sem_queue *q; | |
1047 | int semcnt; | |
1048 | ||
1049 | semcnt = 0; | |
1050 | /* First: check the simple operations. They are easy to evaluate */ | |
1051 | if (count_zero) | |
1052 | l = &sma->sem_base[semnum].pending_const; | |
1053 | else | |
1054 | l = &sma->sem_base[semnum].pending_alter; | |
1055 | ||
1056 | list_for_each_entry(q, l, list) { | |
1057 | /* all task on a per-semaphore list sleep on exactly | |
1058 | * that semaphore | |
1059 | */ | |
1060 | semcnt++; | |
1061 | } | |
1062 | ||
1063 | /* Then: check the complex operations. */ | |
1064 | list_for_each_entry(q, &sma->pending_alter, list) { | |
1065 | semcnt += check_qop(sma, semnum, q, count_zero); | |
1066 | } | |
1067 | if (count_zero) { | |
1068 | list_for_each_entry(q, &sma->pending_const, list) { | |
1069 | semcnt += check_qop(sma, semnum, q, count_zero); | |
1070 | } | |
1071 | } | |
1072 | return semcnt; | |
1073 | } | |
1074 | ||
1075 | /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked | |
1076 | * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem | |
1077 | * remains locked on exit. | |
1078 | */ | |
1079 | static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) | |
1080 | { | |
1081 | struct sem_undo *un, *tu; | |
1082 | struct sem_queue *q, *tq; | |
1083 | struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); | |
1084 | int i; | |
1085 | DEFINE_WAKE_Q(wake_q); | |
1086 | ||
1087 | /* Free the existing undo structures for this semaphore set. */ | |
1088 | ipc_assert_locked_object(&sma->sem_perm); | |
1089 | list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { | |
1090 | list_del(&un->list_id); | |
1091 | spin_lock(&un->ulp->lock); | |
1092 | un->semid = -1; | |
1093 | list_del_rcu(&un->list_proc); | |
1094 | spin_unlock(&un->ulp->lock); | |
1095 | kfree_rcu(un, rcu); | |
1096 | } | |
1097 | ||
1098 | /* Wake up all pending processes and let them fail with EIDRM. */ | |
1099 | list_for_each_entry_safe(q, tq, &sma->pending_const, list) { | |
1100 | unlink_queue(sma, q); | |
1101 | wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); | |
1102 | } | |
1103 | ||
1104 | list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { | |
1105 | unlink_queue(sma, q); | |
1106 | wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); | |
1107 | } | |
1108 | for (i = 0; i < sma->sem_nsems; i++) { | |
1109 | struct sem *sem = sma->sem_base + i; | |
1110 | list_for_each_entry_safe(q, tq, &sem->pending_const, list) { | |
1111 | unlink_queue(sma, q); | |
1112 | wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); | |
1113 | } | |
1114 | list_for_each_entry_safe(q, tq, &sem->pending_alter, list) { | |
1115 | unlink_queue(sma, q); | |
1116 | wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); | |
1117 | } | |
1118 | } | |
1119 | ||
1120 | /* Remove the semaphore set from the IDR */ | |
1121 | sem_rmid(ns, sma); | |
1122 | sem_unlock(sma, -1); | |
1123 | rcu_read_unlock(); | |
1124 | ||
1125 | wake_up_q(&wake_q); | |
1126 | ns->used_sems -= sma->sem_nsems; | |
1127 | ipc_rcu_putref(sma, sem_rcu_free); | |
1128 | } | |
1129 | ||
1130 | static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) | |
1131 | { | |
1132 | switch (version) { | |
1133 | case IPC_64: | |
1134 | return copy_to_user(buf, in, sizeof(*in)); | |
1135 | case IPC_OLD: | |
1136 | { | |
1137 | struct semid_ds out; | |
1138 | ||
1139 | memset(&out, 0, sizeof(out)); | |
1140 | ||
1141 | ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); | |
1142 | ||
1143 | out.sem_otime = in->sem_otime; | |
1144 | out.sem_ctime = in->sem_ctime; | |
1145 | out.sem_nsems = in->sem_nsems; | |
1146 | ||
1147 | return copy_to_user(buf, &out, sizeof(out)); | |
1148 | } | |
1149 | default: | |
1150 | return -EINVAL; | |
1151 | } | |
1152 | } | |
1153 | ||
1154 | static time_t get_semotime(struct sem_array *sma) | |
1155 | { | |
1156 | int i; | |
1157 | time_t res; | |
1158 | ||
1159 | res = sma->sem_base[0].sem_otime; | |
1160 | for (i = 1; i < sma->sem_nsems; i++) { | |
1161 | time_t to = sma->sem_base[i].sem_otime; | |
1162 | ||
1163 | if (to > res) | |
1164 | res = to; | |
1165 | } | |
1166 | return res; | |
1167 | } | |
1168 | ||
1169 | static int semctl_nolock(struct ipc_namespace *ns, int semid, | |
1170 | int cmd, int version, void __user *p) | |
1171 | { | |
1172 | int err; | |
1173 | struct sem_array *sma; | |
1174 | ||
1175 | switch (cmd) { | |
1176 | case IPC_INFO: | |
1177 | case SEM_INFO: | |
1178 | { | |
1179 | struct seminfo seminfo; | |
1180 | int max_id; | |
1181 | ||
1182 | err = security_sem_semctl(NULL, cmd); | |
1183 | if (err) | |
1184 | return err; | |
1185 | ||
1186 | memset(&seminfo, 0, sizeof(seminfo)); | |
1187 | seminfo.semmni = ns->sc_semmni; | |
1188 | seminfo.semmns = ns->sc_semmns; | |
1189 | seminfo.semmsl = ns->sc_semmsl; | |
1190 | seminfo.semopm = ns->sc_semopm; | |
1191 | seminfo.semvmx = SEMVMX; | |
1192 | seminfo.semmnu = SEMMNU; | |
1193 | seminfo.semmap = SEMMAP; | |
1194 | seminfo.semume = SEMUME; | |
1195 | down_read(&sem_ids(ns).rwsem); | |
1196 | if (cmd == SEM_INFO) { | |
1197 | seminfo.semusz = sem_ids(ns).in_use; | |
1198 | seminfo.semaem = ns->used_sems; | |
1199 | } else { | |
1200 | seminfo.semusz = SEMUSZ; | |
1201 | seminfo.semaem = SEMAEM; | |
1202 | } | |
1203 | max_id = ipc_get_maxid(&sem_ids(ns)); | |
1204 | up_read(&sem_ids(ns).rwsem); | |
1205 | if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) | |
1206 | return -EFAULT; | |
1207 | return (max_id < 0) ? 0 : max_id; | |
1208 | } | |
1209 | case IPC_STAT: | |
1210 | case SEM_STAT: | |
1211 | { | |
1212 | struct semid64_ds tbuf; | |
1213 | int id = 0; | |
1214 | ||
1215 | memset(&tbuf, 0, sizeof(tbuf)); | |
1216 | ||
1217 | rcu_read_lock(); | |
1218 | if (cmd == SEM_STAT) { | |
1219 | sma = sem_obtain_object(ns, semid); | |
1220 | if (IS_ERR(sma)) { | |
1221 | err = PTR_ERR(sma); | |
1222 | goto out_unlock; | |
1223 | } | |
1224 | id = sma->sem_perm.id; | |
1225 | } else { | |
1226 | sma = sem_obtain_object_check(ns, semid); | |
1227 | if (IS_ERR(sma)) { | |
1228 | err = PTR_ERR(sma); | |
1229 | goto out_unlock; | |
1230 | } | |
1231 | } | |
1232 | ||
1233 | err = -EACCES; | |
1234 | if (ipcperms(ns, &sma->sem_perm, S_IRUGO)) | |
1235 | goto out_unlock; | |
1236 | ||
1237 | err = security_sem_semctl(sma, cmd); | |
1238 | if (err) | |
1239 | goto out_unlock; | |
1240 | ||
1241 | kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm); | |
1242 | tbuf.sem_otime = get_semotime(sma); | |
1243 | tbuf.sem_ctime = sma->sem_ctime; | |
1244 | tbuf.sem_nsems = sma->sem_nsems; | |
1245 | rcu_read_unlock(); | |
1246 | if (copy_semid_to_user(p, &tbuf, version)) | |
1247 | return -EFAULT; | |
1248 | return id; | |
1249 | } | |
1250 | default: | |
1251 | return -EINVAL; | |
1252 | } | |
1253 | out_unlock: | |
1254 | rcu_read_unlock(); | |
1255 | return err; | |
1256 | } | |
1257 | ||
1258 | static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, | |
1259 | unsigned long arg) | |
1260 | { | |
1261 | struct sem_undo *un; | |
1262 | struct sem_array *sma; | |
1263 | struct sem *curr; | |
1264 | int err, val; | |
1265 | DEFINE_WAKE_Q(wake_q); | |
1266 | ||
1267 | #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN) | |
1268 | /* big-endian 64bit */ | |
1269 | val = arg >> 32; | |
1270 | #else | |
1271 | /* 32bit or little-endian 64bit */ | |
1272 | val = arg; | |
1273 | #endif | |
1274 | ||
1275 | if (val > SEMVMX || val < 0) | |
1276 | return -ERANGE; | |
1277 | ||
1278 | rcu_read_lock(); | |
1279 | sma = sem_obtain_object_check(ns, semid); | |
1280 | if (IS_ERR(sma)) { | |
1281 | rcu_read_unlock(); | |
1282 | return PTR_ERR(sma); | |
1283 | } | |
1284 | ||
1285 | if (semnum < 0 || semnum >= sma->sem_nsems) { | |
1286 | rcu_read_unlock(); | |
1287 | return -EINVAL; | |
1288 | } | |
1289 | ||
1290 | ||
1291 | if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) { | |
1292 | rcu_read_unlock(); | |
1293 | return -EACCES; | |
1294 | } | |
1295 | ||
1296 | err = security_sem_semctl(sma, SETVAL); | |
1297 | if (err) { | |
1298 | rcu_read_unlock(); | |
1299 | return -EACCES; | |
1300 | } | |
1301 | ||
1302 | sem_lock(sma, NULL, -1); | |
1303 | ||
1304 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1305 | sem_unlock(sma, -1); | |
1306 | rcu_read_unlock(); | |
1307 | return -EIDRM; | |
1308 | } | |
1309 | ||
1310 | curr = &sma->sem_base[semnum]; | |
1311 | ||
1312 | ipc_assert_locked_object(&sma->sem_perm); | |
1313 | list_for_each_entry(un, &sma->list_id, list_id) | |
1314 | un->semadj[semnum] = 0; | |
1315 | ||
1316 | curr->semval = val; | |
1317 | curr->sempid = task_tgid_vnr(current); | |
1318 | sma->sem_ctime = get_seconds(); | |
1319 | /* maybe some queued-up processes were waiting for this */ | |
1320 | do_smart_update(sma, NULL, 0, 0, &wake_q); | |
1321 | sem_unlock(sma, -1); | |
1322 | rcu_read_unlock(); | |
1323 | wake_up_q(&wake_q); | |
1324 | return 0; | |
1325 | } | |
1326 | ||
1327 | static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, | |
1328 | int cmd, void __user *p) | |
1329 | { | |
1330 | struct sem_array *sma; | |
1331 | struct sem *curr; | |
1332 | int err, nsems; | |
1333 | ushort fast_sem_io[SEMMSL_FAST]; | |
1334 | ushort *sem_io = fast_sem_io; | |
1335 | DEFINE_WAKE_Q(wake_q); | |
1336 | ||
1337 | rcu_read_lock(); | |
1338 | sma = sem_obtain_object_check(ns, semid); | |
1339 | if (IS_ERR(sma)) { | |
1340 | rcu_read_unlock(); | |
1341 | return PTR_ERR(sma); | |
1342 | } | |
1343 | ||
1344 | nsems = sma->sem_nsems; | |
1345 | ||
1346 | err = -EACCES; | |
1347 | if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO)) | |
1348 | goto out_rcu_wakeup; | |
1349 | ||
1350 | err = security_sem_semctl(sma, cmd); | |
1351 | if (err) | |
1352 | goto out_rcu_wakeup; | |
1353 | ||
1354 | err = -EACCES; | |
1355 | switch (cmd) { | |
1356 | case GETALL: | |
1357 | { | |
1358 | ushort __user *array = p; | |
1359 | int i; | |
1360 | ||
1361 | sem_lock(sma, NULL, -1); | |
1362 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1363 | err = -EIDRM; | |
1364 | goto out_unlock; | |
1365 | } | |
1366 | if (nsems > SEMMSL_FAST) { | |
1367 | if (!ipc_rcu_getref(sma)) { | |
1368 | err = -EIDRM; | |
1369 | goto out_unlock; | |
1370 | } | |
1371 | sem_unlock(sma, -1); | |
1372 | rcu_read_unlock(); | |
1373 | sem_io = ipc_alloc(sizeof(ushort)*nsems); | |
1374 | if (sem_io == NULL) { | |
1375 | ipc_rcu_putref(sma, sem_rcu_free); | |
1376 | return -ENOMEM; | |
1377 | } | |
1378 | ||
1379 | rcu_read_lock(); | |
1380 | sem_lock_and_putref(sma); | |
1381 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1382 | err = -EIDRM; | |
1383 | goto out_unlock; | |
1384 | } | |
1385 | } | |
1386 | for (i = 0; i < sma->sem_nsems; i++) | |
1387 | sem_io[i] = sma->sem_base[i].semval; | |
1388 | sem_unlock(sma, -1); | |
1389 | rcu_read_unlock(); | |
1390 | err = 0; | |
1391 | if (copy_to_user(array, sem_io, nsems*sizeof(ushort))) | |
1392 | err = -EFAULT; | |
1393 | goto out_free; | |
1394 | } | |
1395 | case SETALL: | |
1396 | { | |
1397 | int i; | |
1398 | struct sem_undo *un; | |
1399 | ||
1400 | if (!ipc_rcu_getref(sma)) { | |
1401 | err = -EIDRM; | |
1402 | goto out_rcu_wakeup; | |
1403 | } | |
1404 | rcu_read_unlock(); | |
1405 | ||
1406 | if (nsems > SEMMSL_FAST) { | |
1407 | sem_io = ipc_alloc(sizeof(ushort)*nsems); | |
1408 | if (sem_io == NULL) { | |
1409 | ipc_rcu_putref(sma, sem_rcu_free); | |
1410 | return -ENOMEM; | |
1411 | } | |
1412 | } | |
1413 | ||
1414 | if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) { | |
1415 | ipc_rcu_putref(sma, sem_rcu_free); | |
1416 | err = -EFAULT; | |
1417 | goto out_free; | |
1418 | } | |
1419 | ||
1420 | for (i = 0; i < nsems; i++) { | |
1421 | if (sem_io[i] > SEMVMX) { | |
1422 | ipc_rcu_putref(sma, sem_rcu_free); | |
1423 | err = -ERANGE; | |
1424 | goto out_free; | |
1425 | } | |
1426 | } | |
1427 | rcu_read_lock(); | |
1428 | sem_lock_and_putref(sma); | |
1429 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1430 | err = -EIDRM; | |
1431 | goto out_unlock; | |
1432 | } | |
1433 | ||
1434 | for (i = 0; i < nsems; i++) { | |
1435 | sma->sem_base[i].semval = sem_io[i]; | |
1436 | sma->sem_base[i].sempid = task_tgid_vnr(current); | |
1437 | } | |
1438 | ||
1439 | ipc_assert_locked_object(&sma->sem_perm); | |
1440 | list_for_each_entry(un, &sma->list_id, list_id) { | |
1441 | for (i = 0; i < nsems; i++) | |
1442 | un->semadj[i] = 0; | |
1443 | } | |
1444 | sma->sem_ctime = get_seconds(); | |
1445 | /* maybe some queued-up processes were waiting for this */ | |
1446 | do_smart_update(sma, NULL, 0, 0, &wake_q); | |
1447 | err = 0; | |
1448 | goto out_unlock; | |
1449 | } | |
1450 | /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */ | |
1451 | } | |
1452 | err = -EINVAL; | |
1453 | if (semnum < 0 || semnum >= nsems) | |
1454 | goto out_rcu_wakeup; | |
1455 | ||
1456 | sem_lock(sma, NULL, -1); | |
1457 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1458 | err = -EIDRM; | |
1459 | goto out_unlock; | |
1460 | } | |
1461 | curr = &sma->sem_base[semnum]; | |
1462 | ||
1463 | switch (cmd) { | |
1464 | case GETVAL: | |
1465 | err = curr->semval; | |
1466 | goto out_unlock; | |
1467 | case GETPID: | |
1468 | err = curr->sempid; | |
1469 | goto out_unlock; | |
1470 | case GETNCNT: | |
1471 | err = count_semcnt(sma, semnum, 0); | |
1472 | goto out_unlock; | |
1473 | case GETZCNT: | |
1474 | err = count_semcnt(sma, semnum, 1); | |
1475 | goto out_unlock; | |
1476 | } | |
1477 | ||
1478 | out_unlock: | |
1479 | sem_unlock(sma, -1); | |
1480 | out_rcu_wakeup: | |
1481 | rcu_read_unlock(); | |
1482 | wake_up_q(&wake_q); | |
1483 | out_free: | |
1484 | if (sem_io != fast_sem_io) | |
1485 | ipc_free(sem_io); | |
1486 | return err; | |
1487 | } | |
1488 | ||
1489 | static inline unsigned long | |
1490 | copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) | |
1491 | { | |
1492 | switch (version) { | |
1493 | case IPC_64: | |
1494 | if (copy_from_user(out, buf, sizeof(*out))) | |
1495 | return -EFAULT; | |
1496 | return 0; | |
1497 | case IPC_OLD: | |
1498 | { | |
1499 | struct semid_ds tbuf_old; | |
1500 | ||
1501 | if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) | |
1502 | return -EFAULT; | |
1503 | ||
1504 | out->sem_perm.uid = tbuf_old.sem_perm.uid; | |
1505 | out->sem_perm.gid = tbuf_old.sem_perm.gid; | |
1506 | out->sem_perm.mode = tbuf_old.sem_perm.mode; | |
1507 | ||
1508 | return 0; | |
1509 | } | |
1510 | default: | |
1511 | return -EINVAL; | |
1512 | } | |
1513 | } | |
1514 | ||
1515 | /* | |
1516 | * This function handles some semctl commands which require the rwsem | |
1517 | * to be held in write mode. | |
1518 | * NOTE: no locks must be held, the rwsem is taken inside this function. | |
1519 | */ | |
1520 | static int semctl_down(struct ipc_namespace *ns, int semid, | |
1521 | int cmd, int version, void __user *p) | |
1522 | { | |
1523 | struct sem_array *sma; | |
1524 | int err; | |
1525 | struct semid64_ds semid64; | |
1526 | struct kern_ipc_perm *ipcp; | |
1527 | ||
1528 | if (cmd == IPC_SET) { | |
1529 | if (copy_semid_from_user(&semid64, p, version)) | |
1530 | return -EFAULT; | |
1531 | } | |
1532 | ||
1533 | down_write(&sem_ids(ns).rwsem); | |
1534 | rcu_read_lock(); | |
1535 | ||
1536 | ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd, | |
1537 | &semid64.sem_perm, 0); | |
1538 | if (IS_ERR(ipcp)) { | |
1539 | err = PTR_ERR(ipcp); | |
1540 | goto out_unlock1; | |
1541 | } | |
1542 | ||
1543 | sma = container_of(ipcp, struct sem_array, sem_perm); | |
1544 | ||
1545 | err = security_sem_semctl(sma, cmd); | |
1546 | if (err) | |
1547 | goto out_unlock1; | |
1548 | ||
1549 | switch (cmd) { | |
1550 | case IPC_RMID: | |
1551 | sem_lock(sma, NULL, -1); | |
1552 | /* freeary unlocks the ipc object and rcu */ | |
1553 | freeary(ns, ipcp); | |
1554 | goto out_up; | |
1555 | case IPC_SET: | |
1556 | sem_lock(sma, NULL, -1); | |
1557 | err = ipc_update_perm(&semid64.sem_perm, ipcp); | |
1558 | if (err) | |
1559 | goto out_unlock0; | |
1560 | sma->sem_ctime = get_seconds(); | |
1561 | break; | |
1562 | default: | |
1563 | err = -EINVAL; | |
1564 | goto out_unlock1; | |
1565 | } | |
1566 | ||
1567 | out_unlock0: | |
1568 | sem_unlock(sma, -1); | |
1569 | out_unlock1: | |
1570 | rcu_read_unlock(); | |
1571 | out_up: | |
1572 | up_write(&sem_ids(ns).rwsem); | |
1573 | return err; | |
1574 | } | |
1575 | ||
1576 | SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) | |
1577 | { | |
1578 | int version; | |
1579 | struct ipc_namespace *ns; | |
1580 | void __user *p = (void __user *)arg; | |
1581 | ||
1582 | if (semid < 0) | |
1583 | return -EINVAL; | |
1584 | ||
1585 | version = ipc_parse_version(&cmd); | |
1586 | ns = current->nsproxy->ipc_ns; | |
1587 | ||
1588 | switch (cmd) { | |
1589 | case IPC_INFO: | |
1590 | case SEM_INFO: | |
1591 | case IPC_STAT: | |
1592 | case SEM_STAT: | |
1593 | return semctl_nolock(ns, semid, cmd, version, p); | |
1594 | case GETALL: | |
1595 | case GETVAL: | |
1596 | case GETPID: | |
1597 | case GETNCNT: | |
1598 | case GETZCNT: | |
1599 | case SETALL: | |
1600 | return semctl_main(ns, semid, semnum, cmd, p); | |
1601 | case SETVAL: | |
1602 | return semctl_setval(ns, semid, semnum, arg); | |
1603 | case IPC_RMID: | |
1604 | case IPC_SET: | |
1605 | return semctl_down(ns, semid, cmd, version, p); | |
1606 | default: | |
1607 | return -EINVAL; | |
1608 | } | |
1609 | } | |
1610 | ||
1611 | /* If the task doesn't already have a undo_list, then allocate one | |
1612 | * here. We guarantee there is only one thread using this undo list, | |
1613 | * and current is THE ONE | |
1614 | * | |
1615 | * If this allocation and assignment succeeds, but later | |
1616 | * portions of this code fail, there is no need to free the sem_undo_list. | |
1617 | * Just let it stay associated with the task, and it'll be freed later | |
1618 | * at exit time. | |
1619 | * | |
1620 | * This can block, so callers must hold no locks. | |
1621 | */ | |
1622 | static inline int get_undo_list(struct sem_undo_list **undo_listp) | |
1623 | { | |
1624 | struct sem_undo_list *undo_list; | |
1625 | ||
1626 | undo_list = current->sysvsem.undo_list; | |
1627 | if (!undo_list) { | |
1628 | undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL); | |
1629 | if (undo_list == NULL) | |
1630 | return -ENOMEM; | |
1631 | spin_lock_init(&undo_list->lock); | |
1632 | atomic_set(&undo_list->refcnt, 1); | |
1633 | INIT_LIST_HEAD(&undo_list->list_proc); | |
1634 | ||
1635 | current->sysvsem.undo_list = undo_list; | |
1636 | } | |
1637 | *undo_listp = undo_list; | |
1638 | return 0; | |
1639 | } | |
1640 | ||
1641 | static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) | |
1642 | { | |
1643 | struct sem_undo *un; | |
1644 | ||
1645 | list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) { | |
1646 | if (un->semid == semid) | |
1647 | return un; | |
1648 | } | |
1649 | return NULL; | |
1650 | } | |
1651 | ||
1652 | static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) | |
1653 | { | |
1654 | struct sem_undo *un; | |
1655 | ||
1656 | assert_spin_locked(&ulp->lock); | |
1657 | ||
1658 | un = __lookup_undo(ulp, semid); | |
1659 | if (un) { | |
1660 | list_del_rcu(&un->list_proc); | |
1661 | list_add_rcu(&un->list_proc, &ulp->list_proc); | |
1662 | } | |
1663 | return un; | |
1664 | } | |
1665 | ||
1666 | /** | |
1667 | * find_alloc_undo - lookup (and if not present create) undo array | |
1668 | * @ns: namespace | |
1669 | * @semid: semaphore array id | |
1670 | * | |
1671 | * The function looks up (and if not present creates) the undo structure. | |
1672 | * The size of the undo structure depends on the size of the semaphore | |
1673 | * array, thus the alloc path is not that straightforward. | |
1674 | * Lifetime-rules: sem_undo is rcu-protected, on success, the function | |
1675 | * performs a rcu_read_lock(). | |
1676 | */ | |
1677 | static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) | |
1678 | { | |
1679 | struct sem_array *sma; | |
1680 | struct sem_undo_list *ulp; | |
1681 | struct sem_undo *un, *new; | |
1682 | int nsems, error; | |
1683 | ||
1684 | error = get_undo_list(&ulp); | |
1685 | if (error) | |
1686 | return ERR_PTR(error); | |
1687 | ||
1688 | rcu_read_lock(); | |
1689 | spin_lock(&ulp->lock); | |
1690 | un = lookup_undo(ulp, semid); | |
1691 | spin_unlock(&ulp->lock); | |
1692 | if (likely(un != NULL)) | |
1693 | goto out; | |
1694 | ||
1695 | /* no undo structure around - allocate one. */ | |
1696 | /* step 1: figure out the size of the semaphore array */ | |
1697 | sma = sem_obtain_object_check(ns, semid); | |
1698 | if (IS_ERR(sma)) { | |
1699 | rcu_read_unlock(); | |
1700 | return ERR_CAST(sma); | |
1701 | } | |
1702 | ||
1703 | nsems = sma->sem_nsems; | |
1704 | if (!ipc_rcu_getref(sma)) { | |
1705 | rcu_read_unlock(); | |
1706 | un = ERR_PTR(-EIDRM); | |
1707 | goto out; | |
1708 | } | |
1709 | rcu_read_unlock(); | |
1710 | ||
1711 | /* step 2: allocate new undo structure */ | |
1712 | new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL); | |
1713 | if (!new) { | |
1714 | ipc_rcu_putref(sma, sem_rcu_free); | |
1715 | return ERR_PTR(-ENOMEM); | |
1716 | } | |
1717 | ||
1718 | /* step 3: Acquire the lock on semaphore array */ | |
1719 | rcu_read_lock(); | |
1720 | sem_lock_and_putref(sma); | |
1721 | if (!ipc_valid_object(&sma->sem_perm)) { | |
1722 | sem_unlock(sma, -1); | |
1723 | rcu_read_unlock(); | |
1724 | kfree(new); | |
1725 | un = ERR_PTR(-EIDRM); | |
1726 | goto out; | |
1727 | } | |
1728 | spin_lock(&ulp->lock); | |
1729 | ||
1730 | /* | |
1731 | * step 4: check for races: did someone else allocate the undo struct? | |
1732 | */ | |
1733 | un = lookup_undo(ulp, semid); | |
1734 | if (un) { | |
1735 | kfree(new); | |
1736 | goto success; | |
1737 | } | |
1738 | /* step 5: initialize & link new undo structure */ | |
1739 | new->semadj = (short *) &new[1]; | |
1740 | new->ulp = ulp; | |
1741 | new->semid = semid; | |
1742 | assert_spin_locked(&ulp->lock); | |
1743 | list_add_rcu(&new->list_proc, &ulp->list_proc); | |
1744 | ipc_assert_locked_object(&sma->sem_perm); | |
1745 | list_add(&new->list_id, &sma->list_id); | |
1746 | un = new; | |
1747 | ||
1748 | success: | |
1749 | spin_unlock(&ulp->lock); | |
1750 | sem_unlock(sma, -1); | |
1751 | out: | |
1752 | return un; | |
1753 | } | |
1754 | ||
1755 | SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, | |
1756 | unsigned, nsops, const struct timespec __user *, timeout) | |
1757 | { | |
1758 | int error = -EINVAL; | |
1759 | struct sem_array *sma; | |
1760 | struct sembuf fast_sops[SEMOPM_FAST]; | |
1761 | struct sembuf *sops = fast_sops, *sop; | |
1762 | struct sem_undo *un; | |
1763 | int max, locknum; | |
1764 | bool undos = false, alter = false, dupsop = false; | |
1765 | struct sem_queue queue; | |
1766 | unsigned long dup = 0, jiffies_left = 0; | |
1767 | struct ipc_namespace *ns; | |
1768 | ||
1769 | ns = current->nsproxy->ipc_ns; | |
1770 | ||
1771 | if (nsops < 1 || semid < 0) | |
1772 | return -EINVAL; | |
1773 | if (nsops > ns->sc_semopm) | |
1774 | return -E2BIG; | |
1775 | if (nsops > SEMOPM_FAST) { | |
1776 | sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL); | |
1777 | if (sops == NULL) | |
1778 | return -ENOMEM; | |
1779 | } | |
1780 | ||
1781 | if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) { | |
1782 | error = -EFAULT; | |
1783 | goto out_free; | |
1784 | } | |
1785 | ||
1786 | if (timeout) { | |
1787 | struct timespec _timeout; | |
1788 | if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) { | |
1789 | error = -EFAULT; | |
1790 | goto out_free; | |
1791 | } | |
1792 | if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 || | |
1793 | _timeout.tv_nsec >= 1000000000L) { | |
1794 | error = -EINVAL; | |
1795 | goto out_free; | |
1796 | } | |
1797 | jiffies_left = timespec_to_jiffies(&_timeout); | |
1798 | } | |
1799 | ||
1800 | max = 0; | |
1801 | for (sop = sops; sop < sops + nsops; sop++) { | |
1802 | unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG); | |
1803 | ||
1804 | if (sop->sem_num >= max) | |
1805 | max = sop->sem_num; | |
1806 | if (sop->sem_flg & SEM_UNDO) | |
1807 | undos = true; | |
1808 | if (dup & mask) { | |
1809 | /* | |
1810 | * There was a previous alter access that appears | |
1811 | * to have accessed the same semaphore, thus use | |
1812 | * the dupsop logic. "appears", because the detection | |
1813 | * can only check % BITS_PER_LONG. | |
1814 | */ | |
1815 | dupsop = true; | |
1816 | } | |
1817 | if (sop->sem_op != 0) { | |
1818 | alter = true; | |
1819 | dup |= mask; | |
1820 | } | |
1821 | } | |
1822 | ||
1823 | if (undos) { | |
1824 | /* On success, find_alloc_undo takes the rcu_read_lock */ | |
1825 | un = find_alloc_undo(ns, semid); | |
1826 | if (IS_ERR(un)) { | |
1827 | error = PTR_ERR(un); | |
1828 | goto out_free; | |
1829 | } | |
1830 | } else { | |
1831 | un = NULL; | |
1832 | rcu_read_lock(); | |
1833 | } | |
1834 | ||
1835 | sma = sem_obtain_object_check(ns, semid); | |
1836 | if (IS_ERR(sma)) { | |
1837 | rcu_read_unlock(); | |
1838 | error = PTR_ERR(sma); | |
1839 | goto out_free; | |
1840 | } | |
1841 | ||
1842 | error = -EFBIG; | |
1843 | if (max >= sma->sem_nsems) { | |
1844 | rcu_read_unlock(); | |
1845 | goto out_free; | |
1846 | } | |
1847 | ||
1848 | error = -EACCES; | |
1849 | if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) { | |
1850 | rcu_read_unlock(); | |
1851 | goto out_free; | |
1852 | } | |
1853 | ||
1854 | error = security_sem_semop(sma, sops, nsops, alter); | |
1855 | if (error) { | |
1856 | rcu_read_unlock(); | |
1857 | goto out_free; | |
1858 | } | |
1859 | ||
1860 | error = -EIDRM; | |
1861 | locknum = sem_lock(sma, sops, nsops); | |
1862 | /* | |
1863 | * We eventually might perform the following check in a lockless | |
1864 | * fashion, considering ipc_valid_object() locking constraints. | |
1865 | * If nsops == 1 and there is no contention for sem_perm.lock, then | |
1866 | * only a per-semaphore lock is held and it's OK to proceed with the | |
1867 | * check below. More details on the fine grained locking scheme | |
1868 | * entangled here and why it's RMID race safe on comments at sem_lock() | |
1869 | */ | |
1870 | if (!ipc_valid_object(&sma->sem_perm)) | |
1871 | goto out_unlock_free; | |
1872 | /* | |
1873 | * semid identifiers are not unique - find_alloc_undo may have | |
1874 | * allocated an undo structure, it was invalidated by an RMID | |
1875 | * and now a new array with received the same id. Check and fail. | |
1876 | * This case can be detected checking un->semid. The existence of | |
1877 | * "un" itself is guaranteed by rcu. | |
1878 | */ | |
1879 | if (un && un->semid == -1) | |
1880 | goto out_unlock_free; | |
1881 | ||
1882 | queue.sops = sops; | |
1883 | queue.nsops = nsops; | |
1884 | queue.undo = un; | |
1885 | queue.pid = task_tgid_vnr(current); | |
1886 | queue.alter = alter; | |
1887 | queue.dupsop = dupsop; | |
1888 | ||
1889 | error = perform_atomic_semop(sma, &queue); | |
1890 | if (error == 0) { /* non-blocking succesfull path */ | |
1891 | DEFINE_WAKE_Q(wake_q); | |
1892 | ||
1893 | /* | |
1894 | * If the operation was successful, then do | |
1895 | * the required updates. | |
1896 | */ | |
1897 | if (alter) | |
1898 | do_smart_update(sma, sops, nsops, 1, &wake_q); | |
1899 | else | |
1900 | set_semotime(sma, sops); | |
1901 | ||
1902 | sem_unlock(sma, locknum); | |
1903 | rcu_read_unlock(); | |
1904 | wake_up_q(&wake_q); | |
1905 | ||
1906 | goto out_free; | |
1907 | } | |
1908 | if (error < 0) /* non-blocking error path */ | |
1909 | goto out_unlock_free; | |
1910 | ||
1911 | /* | |
1912 | * We need to sleep on this operation, so we put the current | |
1913 | * task into the pending queue and go to sleep. | |
1914 | */ | |
1915 | if (nsops == 1) { | |
1916 | struct sem *curr; | |
1917 | curr = &sma->sem_base[sops->sem_num]; | |
1918 | ||
1919 | if (alter) { | |
1920 | if (sma->complex_count) { | |
1921 | list_add_tail(&queue.list, | |
1922 | &sma->pending_alter); | |
1923 | } else { | |
1924 | ||
1925 | list_add_tail(&queue.list, | |
1926 | &curr->pending_alter); | |
1927 | } | |
1928 | } else { | |
1929 | list_add_tail(&queue.list, &curr->pending_const); | |
1930 | } | |
1931 | } else { | |
1932 | if (!sma->complex_count) | |
1933 | merge_queues(sma); | |
1934 | ||
1935 | if (alter) | |
1936 | list_add_tail(&queue.list, &sma->pending_alter); | |
1937 | else | |
1938 | list_add_tail(&queue.list, &sma->pending_const); | |
1939 | ||
1940 | sma->complex_count++; | |
1941 | } | |
1942 | ||
1943 | do { | |
1944 | queue.status = -EINTR; | |
1945 | queue.sleeper = current; | |
1946 | ||
1947 | __set_current_state(TASK_INTERRUPTIBLE); | |
1948 | sem_unlock(sma, locknum); | |
1949 | rcu_read_unlock(); | |
1950 | ||
1951 | if (timeout) | |
1952 | jiffies_left = schedule_timeout(jiffies_left); | |
1953 | else | |
1954 | schedule(); | |
1955 | ||
1956 | /* | |
1957 | * fastpath: the semop has completed, either successfully or | |
1958 | * not, from the syscall pov, is quite irrelevant to us at this | |
1959 | * point; we're done. | |
1960 | * | |
1961 | * We _do_ care, nonetheless, about being awoken by a signal or | |
1962 | * spuriously. The queue.status is checked again in the | |
1963 | * slowpath (aka after taking sem_lock), such that we can detect | |
1964 | * scenarios where we were awakened externally, during the | |
1965 | * window between wake_q_add() and wake_up_q(). | |
1966 | */ | |
1967 | error = READ_ONCE(queue.status); | |
1968 | if (error != -EINTR) { | |
1969 | /* | |
1970 | * User space could assume that semop() is a memory | |
1971 | * barrier: Without the mb(), the cpu could | |
1972 | * speculatively read in userspace stale data that was | |
1973 | * overwritten by the previous owner of the semaphore. | |
1974 | */ | |
1975 | smp_mb(); | |
1976 | goto out_free; | |
1977 | } | |
1978 | ||
1979 | rcu_read_lock(); | |
1980 | locknum = sem_lock(sma, sops, nsops); | |
1981 | ||
1982 | if (!ipc_valid_object(&sma->sem_perm)) | |
1983 | goto out_unlock_free; | |
1984 | ||
1985 | error = READ_ONCE(queue.status); | |
1986 | ||
1987 | /* | |
1988 | * If queue.status != -EINTR we are woken up by another process. | |
1989 | * Leave without unlink_queue(), but with sem_unlock(). | |
1990 | */ | |
1991 | if (error != -EINTR) | |
1992 | goto out_unlock_free; | |
1993 | ||
1994 | /* | |
1995 | * If an interrupt occurred we have to clean up the queue. | |
1996 | */ | |
1997 | if (timeout && jiffies_left == 0) | |
1998 | error = -EAGAIN; | |
1999 | } while (error == -EINTR && !signal_pending(current)); /* spurious */ | |
2000 | ||
2001 | unlink_queue(sma, &queue); | |
2002 | ||
2003 | out_unlock_free: | |
2004 | sem_unlock(sma, locknum); | |
2005 | rcu_read_unlock(); | |
2006 | out_free: | |
2007 | if (sops != fast_sops) | |
2008 | kfree(sops); | |
2009 | return error; | |
2010 | } | |
2011 | ||
2012 | SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, | |
2013 | unsigned, nsops) | |
2014 | { | |
2015 | return sys_semtimedop(semid, tsops, nsops, NULL); | |
2016 | } | |
2017 | ||
2018 | /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between | |
2019 | * parent and child tasks. | |
2020 | */ | |
2021 | ||
2022 | int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) | |
2023 | { | |
2024 | struct sem_undo_list *undo_list; | |
2025 | int error; | |
2026 | ||
2027 | if (clone_flags & CLONE_SYSVSEM) { | |
2028 | error = get_undo_list(&undo_list); | |
2029 | if (error) | |
2030 | return error; | |
2031 | atomic_inc(&undo_list->refcnt); | |
2032 | tsk->sysvsem.undo_list = undo_list; | |
2033 | } else | |
2034 | tsk->sysvsem.undo_list = NULL; | |
2035 | ||
2036 | return 0; | |
2037 | } | |
2038 | ||
2039 | /* | |
2040 | * add semadj values to semaphores, free undo structures. | |
2041 | * undo structures are not freed when semaphore arrays are destroyed | |
2042 | * so some of them may be out of date. | |
2043 | * IMPLEMENTATION NOTE: There is some confusion over whether the | |
2044 | * set of adjustments that needs to be done should be done in an atomic | |
2045 | * manner or not. That is, if we are attempting to decrement the semval | |
2046 | * should we queue up and wait until we can do so legally? | |
2047 | * The original implementation attempted to do this (queue and wait). | |
2048 | * The current implementation does not do so. The POSIX standard | |
2049 | * and SVID should be consulted to determine what behavior is mandated. | |
2050 | */ | |
2051 | void exit_sem(struct task_struct *tsk) | |
2052 | { | |
2053 | struct sem_undo_list *ulp; | |
2054 | ||
2055 | ulp = tsk->sysvsem.undo_list; | |
2056 | if (!ulp) | |
2057 | return; | |
2058 | tsk->sysvsem.undo_list = NULL; | |
2059 | ||
2060 | if (!atomic_dec_and_test(&ulp->refcnt)) | |
2061 | return; | |
2062 | ||
2063 | for (;;) { | |
2064 | struct sem_array *sma; | |
2065 | struct sem_undo *un; | |
2066 | int semid, i; | |
2067 | DEFINE_WAKE_Q(wake_q); | |
2068 | ||
2069 | cond_resched(); | |
2070 | ||
2071 | rcu_read_lock(); | |
2072 | un = list_entry_rcu(ulp->list_proc.next, | |
2073 | struct sem_undo, list_proc); | |
2074 | if (&un->list_proc == &ulp->list_proc) { | |
2075 | /* | |
2076 | * We must wait for freeary() before freeing this ulp, | |
2077 | * in case we raced with last sem_undo. There is a small | |
2078 | * possibility where we exit while freeary() didn't | |
2079 | * finish unlocking sem_undo_list. | |
2080 | */ | |
2081 | spin_unlock_wait(&ulp->lock); | |
2082 | rcu_read_unlock(); | |
2083 | break; | |
2084 | } | |
2085 | spin_lock(&ulp->lock); | |
2086 | semid = un->semid; | |
2087 | spin_unlock(&ulp->lock); | |
2088 | ||
2089 | /* exit_sem raced with IPC_RMID, nothing to do */ | |
2090 | if (semid == -1) { | |
2091 | rcu_read_unlock(); | |
2092 | continue; | |
2093 | } | |
2094 | ||
2095 | sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid); | |
2096 | /* exit_sem raced with IPC_RMID, nothing to do */ | |
2097 | if (IS_ERR(sma)) { | |
2098 | rcu_read_unlock(); | |
2099 | continue; | |
2100 | } | |
2101 | ||
2102 | sem_lock(sma, NULL, -1); | |
2103 | /* exit_sem raced with IPC_RMID, nothing to do */ | |
2104 | if (!ipc_valid_object(&sma->sem_perm)) { | |
2105 | sem_unlock(sma, -1); | |
2106 | rcu_read_unlock(); | |
2107 | continue; | |
2108 | } | |
2109 | un = __lookup_undo(ulp, semid); | |
2110 | if (un == NULL) { | |
2111 | /* exit_sem raced with IPC_RMID+semget() that created | |
2112 | * exactly the same semid. Nothing to do. | |
2113 | */ | |
2114 | sem_unlock(sma, -1); | |
2115 | rcu_read_unlock(); | |
2116 | continue; | |
2117 | } | |
2118 | ||
2119 | /* remove un from the linked lists */ | |
2120 | ipc_assert_locked_object(&sma->sem_perm); | |
2121 | list_del(&un->list_id); | |
2122 | ||
2123 | /* we are the last process using this ulp, acquiring ulp->lock | |
2124 | * isn't required. Besides that, we are also protected against | |
2125 | * IPC_RMID as we hold sma->sem_perm lock now | |
2126 | */ | |
2127 | list_del_rcu(&un->list_proc); | |
2128 | ||
2129 | /* perform adjustments registered in un */ | |
2130 | for (i = 0; i < sma->sem_nsems; i++) { | |
2131 | struct sem *semaphore = &sma->sem_base[i]; | |
2132 | if (un->semadj[i]) { | |
2133 | semaphore->semval += un->semadj[i]; | |
2134 | /* | |
2135 | * Range checks of the new semaphore value, | |
2136 | * not defined by sus: | |
2137 | * - Some unices ignore the undo entirely | |
2138 | * (e.g. HP UX 11i 11.22, Tru64 V5.1) | |
2139 | * - some cap the value (e.g. FreeBSD caps | |
2140 | * at 0, but doesn't enforce SEMVMX) | |
2141 | * | |
2142 | * Linux caps the semaphore value, both at 0 | |
2143 | * and at SEMVMX. | |
2144 | * | |
2145 | * Manfred <manfred@colorfullife.com> | |
2146 | */ | |
2147 | if (semaphore->semval < 0) | |
2148 | semaphore->semval = 0; | |
2149 | if (semaphore->semval > SEMVMX) | |
2150 | semaphore->semval = SEMVMX; | |
2151 | semaphore->sempid = task_tgid_vnr(current); | |
2152 | } | |
2153 | } | |
2154 | /* maybe some queued-up processes were waiting for this */ | |
2155 | do_smart_update(sma, NULL, 0, 1, &wake_q); | |
2156 | sem_unlock(sma, -1); | |
2157 | rcu_read_unlock(); | |
2158 | wake_up_q(&wake_q); | |
2159 | ||
2160 | kfree_rcu(un, rcu); | |
2161 | } | |
2162 | kfree(ulp); | |
2163 | } | |
2164 | ||
2165 | #ifdef CONFIG_PROC_FS | |
2166 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it) | |
2167 | { | |
2168 | struct user_namespace *user_ns = seq_user_ns(s); | |
2169 | struct sem_array *sma = it; | |
2170 | time_t sem_otime; | |
2171 | ||
2172 | /* | |
2173 | * The proc interface isn't aware of sem_lock(), it calls | |
2174 | * ipc_lock_object() directly (in sysvipc_find_ipc). | |
2175 | * In order to stay compatible with sem_lock(), we must | |
2176 | * enter / leave complex_mode. | |
2177 | */ | |
2178 | complexmode_enter(sma); | |
2179 | ||
2180 | sem_otime = get_semotime(sma); | |
2181 | ||
2182 | seq_printf(s, | |
2183 | "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n", | |
2184 | sma->sem_perm.key, | |
2185 | sma->sem_perm.id, | |
2186 | sma->sem_perm.mode, | |
2187 | sma->sem_nsems, | |
2188 | from_kuid_munged(user_ns, sma->sem_perm.uid), | |
2189 | from_kgid_munged(user_ns, sma->sem_perm.gid), | |
2190 | from_kuid_munged(user_ns, sma->sem_perm.cuid), | |
2191 | from_kgid_munged(user_ns, sma->sem_perm.cgid), | |
2192 | sem_otime, | |
2193 | sma->sem_ctime); | |
2194 | ||
2195 | complexmode_tryleave(sma); | |
2196 | ||
2197 | return 0; | |
2198 | } | |
2199 | #endif |