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Source at commit b13e7eb172b6f08e5fc22da162bdde5fcde201b5 created 11 years 11 months ago. By Maarten ter Huurne, fbcon: Add 6x10 font | |
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1 | /* |
2 | * linux/ipc/sem.c |
3 | * Copyright (C) 1992 Krishna Balasubramanian |
4 | * Copyright (C) 1995 Eric Schenk, Bruno Haible |
5 | * |
6 | * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com> |
7 | * |
8 | * SMP-threaded, sysctl's added |
9 | * (c) 1999 Manfred Spraul <manfred@colorfullife.com> |
10 | * Enforced range limit on SEM_UNDO |
11 | * (c) 2001 Red Hat Inc |
12 | * Lockless wakeup |
13 | * (c) 2003 Manfred Spraul <manfred@colorfullife.com> |
14 | * Further wakeup optimizations, documentation |
15 | * (c) 2010 Manfred Spraul <manfred@colorfullife.com> |
16 | * |
17 | * support for audit of ipc object properties and permission changes |
18 | * Dustin Kirkland <dustin.kirkland@us.ibm.com> |
19 | * |
20 | * namespaces support |
21 | * OpenVZ, SWsoft Inc. |
22 | * Pavel Emelianov <xemul@openvz.org> |
23 | * |
24 | * Implementation notes: (May 2010) |
25 | * This file implements System V semaphores. |
26 | * |
27 | * User space visible behavior: |
28 | * - FIFO ordering for semop() operations (just FIFO, not starvation |
29 | * protection) |
30 | * - multiple semaphore operations that alter the same semaphore in |
31 | * one semop() are handled. |
32 | * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and |
33 | * SETALL calls. |
34 | * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO. |
35 | * - undo adjustments at process exit are limited to 0..SEMVMX. |
36 | * - namespace are supported. |
37 | * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing |
38 | * to /proc/sys/kernel/sem. |
39 | * - statistics about the usage are reported in /proc/sysvipc/sem. |
40 | * |
41 | * Internals: |
42 | * - scalability: |
43 | * - all global variables are read-mostly. |
44 | * - semop() calls and semctl(RMID) are synchronized by RCU. |
45 | * - most operations do write operations (actually: spin_lock calls) to |
46 | * the per-semaphore array structure. |
47 | * Thus: Perfect SMP scaling between independent semaphore arrays. |
48 | * If multiple semaphores in one array are used, then cache line |
49 | * trashing on the semaphore array spinlock will limit the scaling. |
50 | * - semncnt and semzcnt are calculated on demand in count_semncnt() and |
51 | * count_semzcnt() |
52 | * - the task that performs a successful semop() scans the list of all |
53 | * sleeping tasks and completes any pending operations that can be fulfilled. |
54 | * Semaphores are actively given to waiting tasks (necessary for FIFO). |
55 | * (see update_queue()) |
56 | * - To improve the scalability, the actual wake-up calls are performed after |
57 | * dropping all locks. (see wake_up_sem_queue_prepare(), |
58 | * wake_up_sem_queue_do()) |
59 | * - All work is done by the waker, the woken up task does not have to do |
60 | * anything - not even acquiring a lock or dropping a refcount. |
61 | * - A woken up task may not even touch the semaphore array anymore, it may |
62 | * have been destroyed already by a semctl(RMID). |
63 | * - The synchronizations between wake-ups due to a timeout/signal and a |
64 | * wake-up due to a completed semaphore operation is achieved by using an |
65 | * intermediate state (IN_WAKEUP). |
66 | * - UNDO values are stored in an array (one per process and per |
67 | * semaphore array, lazily allocated). For backwards compatibility, multiple |
68 | * modes for the UNDO variables are supported (per process, per thread) |
69 | * (see copy_semundo, CLONE_SYSVSEM) |
70 | * - There are two lists of the pending operations: a per-array list |
71 | * and per-semaphore list (stored in the array). This allows to achieve FIFO |
72 | * ordering without always scanning all pending operations. |
73 | * The worst-case behavior is nevertheless O(N^2) for N wakeups. |
74 | */ |
75 | |
76 | #include <linux/slab.h> |
77 | #include <linux/spinlock.h> |
78 | #include <linux/init.h> |
79 | #include <linux/proc_fs.h> |
80 | #include <linux/time.h> |
81 | #include <linux/security.h> |
82 | #include <linux/syscalls.h> |
83 | #include <linux/audit.h> |
84 | #include <linux/capability.h> |
85 | #include <linux/seq_file.h> |
86 | #include <linux/rwsem.h> |
87 | #include <linux/nsproxy.h> |
88 | #include <linux/ipc_namespace.h> |
89 | |
90 | #include <asm/uaccess.h> |
91 | #include "util.h" |
92 | |
93 | /* One semaphore structure for each semaphore in the system. */ |
94 | struct sem { |
95 | int semval; /* current value */ |
96 | int sempid; /* pid of last operation */ |
97 | struct list_head sem_pending; /* pending single-sop operations */ |
98 | }; |
99 | |
100 | /* One queue for each sleeping process in the system. */ |
101 | struct sem_queue { |
102 | struct list_head simple_list; /* queue of pending operations */ |
103 | struct list_head list; /* queue of pending operations */ |
104 | struct task_struct *sleeper; /* this process */ |
105 | struct sem_undo *undo; /* undo structure */ |
106 | int pid; /* process id of requesting process */ |
107 | int status; /* completion status of operation */ |
108 | struct sembuf *sops; /* array of pending operations */ |
109 | int nsops; /* number of operations */ |
110 | int alter; /* does *sops alter the array? */ |
111 | }; |
112 | |
113 | /* Each task has a list of undo requests. They are executed automatically |
114 | * when the process exits. |
115 | */ |
116 | struct sem_undo { |
117 | struct list_head list_proc; /* per-process list: * |
118 | * all undos from one process |
119 | * rcu protected */ |
120 | struct rcu_head rcu; /* rcu struct for sem_undo */ |
121 | struct sem_undo_list *ulp; /* back ptr to sem_undo_list */ |
122 | struct list_head list_id; /* per semaphore array list: |
123 | * all undos for one array */ |
124 | int semid; /* semaphore set identifier */ |
125 | short *semadj; /* array of adjustments */ |
126 | /* one per semaphore */ |
127 | }; |
128 | |
129 | /* sem_undo_list controls shared access to the list of sem_undo structures |
130 | * that may be shared among all a CLONE_SYSVSEM task group. |
131 | */ |
132 | struct sem_undo_list { |
133 | atomic_t refcnt; |
134 | spinlock_t lock; |
135 | struct list_head list_proc; |
136 | }; |
137 | |
138 | |
139 | #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS]) |
140 | |
141 | #define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm) |
142 | #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid) |
143 | |
144 | static int newary(struct ipc_namespace *, struct ipc_params *); |
145 | static void freeary(struct ipc_namespace *, struct kern_ipc_perm *); |
146 | #ifdef CONFIG_PROC_FS |
147 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it); |
148 | #endif |
149 | |
150 | #define SEMMSL_FAST 256 /* 512 bytes on stack */ |
151 | #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ |
152 | |
153 | /* |
154 | * linked list protection: |
155 | * sem_undo.id_next, |
156 | * sem_array.sem_pending{,last}, |
157 | * sem_array.sem_undo: sem_lock() for read/write |
158 | * sem_undo.proc_next: only "current" is allowed to read/write that field. |
159 | * |
160 | */ |
161 | |
162 | #define sc_semmsl sem_ctls[0] |
163 | #define sc_semmns sem_ctls[1] |
164 | #define sc_semopm sem_ctls[2] |
165 | #define sc_semmni sem_ctls[3] |
166 | |
167 | void sem_init_ns(struct ipc_namespace *ns) |
168 | { |
169 | ns->sc_semmsl = SEMMSL; |
170 | ns->sc_semmns = SEMMNS; |
171 | ns->sc_semopm = SEMOPM; |
172 | ns->sc_semmni = SEMMNI; |
173 | ns->used_sems = 0; |
174 | ipc_init_ids(&ns->ids[IPC_SEM_IDS]); |
175 | } |
176 | |
177 | #ifdef CONFIG_IPC_NS |
178 | void sem_exit_ns(struct ipc_namespace *ns) |
179 | { |
180 | free_ipcs(ns, &sem_ids(ns), freeary); |
181 | idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr); |
182 | } |
183 | #endif |
184 | |
185 | void __init sem_init (void) |
186 | { |
187 | sem_init_ns(&init_ipc_ns); |
188 | ipc_init_proc_interface("sysvipc/sem", |
189 | " key semid perms nsems uid gid cuid cgid otime ctime\n", |
190 | IPC_SEM_IDS, sysvipc_sem_proc_show); |
191 | } |
192 | |
193 | /* |
194 | * sem_lock_(check_) routines are called in the paths where the rw_mutex |
195 | * is not held. |
196 | */ |
197 | static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id) |
198 | { |
199 | struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id); |
200 | |
201 | if (IS_ERR(ipcp)) |
202 | return (struct sem_array *)ipcp; |
203 | |
204 | return container_of(ipcp, struct sem_array, sem_perm); |
205 | } |
206 | |
207 | static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns, |
208 | int id) |
209 | { |
210 | struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id); |
211 | |
212 | if (IS_ERR(ipcp)) |
213 | return (struct sem_array *)ipcp; |
214 | |
215 | return container_of(ipcp, struct sem_array, sem_perm); |
216 | } |
217 | |
218 | static inline void sem_lock_and_putref(struct sem_array *sma) |
219 | { |
220 | ipc_lock_by_ptr(&sma->sem_perm); |
221 | ipc_rcu_putref(sma); |
222 | } |
223 | |
224 | static inline void sem_getref_and_unlock(struct sem_array *sma) |
225 | { |
226 | ipc_rcu_getref(sma); |
227 | ipc_unlock(&(sma)->sem_perm); |
228 | } |
229 | |
230 | static inline void sem_putref(struct sem_array *sma) |
231 | { |
232 | ipc_lock_by_ptr(&sma->sem_perm); |
233 | ipc_rcu_putref(sma); |
234 | ipc_unlock(&(sma)->sem_perm); |
235 | } |
236 | |
237 | static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) |
238 | { |
239 | ipc_rmid(&sem_ids(ns), &s->sem_perm); |
240 | } |
241 | |
242 | /* |
243 | * Lockless wakeup algorithm: |
244 | * Without the check/retry algorithm a lockless wakeup is possible: |
245 | * - queue.status is initialized to -EINTR before blocking. |
246 | * - wakeup is performed by |
247 | * * unlinking the queue entry from sma->sem_pending |
248 | * * setting queue.status to IN_WAKEUP |
249 | * This is the notification for the blocked thread that a |
250 | * result value is imminent. |
251 | * * call wake_up_process |
252 | * * set queue.status to the final value. |
253 | * - the previously blocked thread checks queue.status: |
254 | * * if it's IN_WAKEUP, then it must wait until the value changes |
255 | * * if it's not -EINTR, then the operation was completed by |
256 | * update_queue. semtimedop can return queue.status without |
257 | * performing any operation on the sem array. |
258 | * * otherwise it must acquire the spinlock and check what's up. |
259 | * |
260 | * The two-stage algorithm is necessary to protect against the following |
261 | * races: |
262 | * - if queue.status is set after wake_up_process, then the woken up idle |
263 | * thread could race forward and try (and fail) to acquire sma->lock |
264 | * before update_queue had a chance to set queue.status |
265 | * - if queue.status is written before wake_up_process and if the |
266 | * blocked process is woken up by a signal between writing |
267 | * queue.status and the wake_up_process, then the woken up |
268 | * process could return from semtimedop and die by calling |
269 | * sys_exit before wake_up_process is called. Then wake_up_process |
270 | * will oops, because the task structure is already invalid. |
271 | * (yes, this happened on s390 with sysv msg). |
272 | * |
273 | */ |
274 | #define IN_WAKEUP 1 |
275 | |
276 | /** |
277 | * newary - Create a new semaphore set |
278 | * @ns: namespace |
279 | * @params: ptr to the structure that contains key, semflg and nsems |
280 | * |
281 | * Called with sem_ids.rw_mutex held (as a writer) |
282 | */ |
283 | |
284 | static int newary(struct ipc_namespace *ns, struct ipc_params *params) |
285 | { |
286 | int id; |
287 | int retval; |
288 | struct sem_array *sma; |
289 | int size; |
290 | key_t key = params->key; |
291 | int nsems = params->u.nsems; |
292 | int semflg = params->flg; |
293 | int i; |
294 | |
295 | if (!nsems) |
296 | return -EINVAL; |
297 | if (ns->used_sems + nsems > ns->sc_semmns) |
298 | return -ENOSPC; |
299 | |
300 | size = sizeof (*sma) + nsems * sizeof (struct sem); |
301 | sma = ipc_rcu_alloc(size); |
302 | if (!sma) { |
303 | return -ENOMEM; |
304 | } |
305 | memset (sma, 0, size); |
306 | |
307 | sma->sem_perm.mode = (semflg & S_IRWXUGO); |
308 | sma->sem_perm.key = key; |
309 | |
310 | sma->sem_perm.security = NULL; |
311 | retval = security_sem_alloc(sma); |
312 | if (retval) { |
313 | ipc_rcu_putref(sma); |
314 | return retval; |
315 | } |
316 | |
317 | id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); |
318 | if (id < 0) { |
319 | security_sem_free(sma); |
320 | ipc_rcu_putref(sma); |
321 | return id; |
322 | } |
323 | ns->used_sems += nsems; |
324 | |
325 | sma->sem_base = (struct sem *) &sma[1]; |
326 | |
327 | for (i = 0; i < nsems; i++) |
328 | INIT_LIST_HEAD(&sma->sem_base[i].sem_pending); |
329 | |
330 | sma->complex_count = 0; |
331 | INIT_LIST_HEAD(&sma->sem_pending); |
332 | INIT_LIST_HEAD(&sma->list_id); |
333 | sma->sem_nsems = nsems; |
334 | sma->sem_ctime = get_seconds(); |
335 | sem_unlock(sma); |
336 | |
337 | return sma->sem_perm.id; |
338 | } |
339 | |
340 | |
341 | /* |
342 | * Called with sem_ids.rw_mutex and ipcp locked. |
343 | */ |
344 | static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg) |
345 | { |
346 | struct sem_array *sma; |
347 | |
348 | sma = container_of(ipcp, struct sem_array, sem_perm); |
349 | return security_sem_associate(sma, semflg); |
350 | } |
351 | |
352 | /* |
353 | * Called with sem_ids.rw_mutex and ipcp locked. |
354 | */ |
355 | static inline int sem_more_checks(struct kern_ipc_perm *ipcp, |
356 | struct ipc_params *params) |
357 | { |
358 | struct sem_array *sma; |
359 | |
360 | sma = container_of(ipcp, struct sem_array, sem_perm); |
361 | if (params->u.nsems > sma->sem_nsems) |
362 | return -EINVAL; |
363 | |
364 | return 0; |
365 | } |
366 | |
367 | SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) |
368 | { |
369 | struct ipc_namespace *ns; |
370 | struct ipc_ops sem_ops; |
371 | struct ipc_params sem_params; |
372 | |
373 | ns = current->nsproxy->ipc_ns; |
374 | |
375 | if (nsems < 0 || nsems > ns->sc_semmsl) |
376 | return -EINVAL; |
377 | |
378 | sem_ops.getnew = newary; |
379 | sem_ops.associate = sem_security; |
380 | sem_ops.more_checks = sem_more_checks; |
381 | |
382 | sem_params.key = key; |
383 | sem_params.flg = semflg; |
384 | sem_params.u.nsems = nsems; |
385 | |
386 | return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); |
387 | } |
388 | |
389 | /* |
390 | * Determine whether a sequence of semaphore operations would succeed |
391 | * all at once. Return 0 if yes, 1 if need to sleep, else return error code. |
392 | */ |
393 | |
394 | static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops, |
395 | int nsops, struct sem_undo *un, int pid) |
396 | { |
397 | int result, sem_op; |
398 | struct sembuf *sop; |
399 | struct sem * curr; |
400 | |
401 | for (sop = sops; sop < sops + nsops; sop++) { |
402 | curr = sma->sem_base + sop->sem_num; |
403 | sem_op = sop->sem_op; |
404 | result = curr->semval; |
405 | |
406 | if (!sem_op && result) |
407 | goto would_block; |
408 | |
409 | result += sem_op; |
410 | if (result < 0) |
411 | goto would_block; |
412 | if (result > SEMVMX) |
413 | goto out_of_range; |
414 | if (sop->sem_flg & SEM_UNDO) { |
415 | int undo = un->semadj[sop->sem_num] - sem_op; |
416 | /* |
417 | * Exceeding the undo range is an error. |
418 | */ |
419 | if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
420 | goto out_of_range; |
421 | } |
422 | curr->semval = result; |
423 | } |
424 | |
425 | sop--; |
426 | while (sop >= sops) { |
427 | sma->sem_base[sop->sem_num].sempid = pid; |
428 | if (sop->sem_flg & SEM_UNDO) |
429 | un->semadj[sop->sem_num] -= sop->sem_op; |
430 | sop--; |
431 | } |
432 | |
433 | return 0; |
434 | |
435 | out_of_range: |
436 | result = -ERANGE; |
437 | goto undo; |
438 | |
439 | would_block: |
440 | if (sop->sem_flg & IPC_NOWAIT) |
441 | result = -EAGAIN; |
442 | else |
443 | result = 1; |
444 | |
445 | undo: |
446 | sop--; |
447 | while (sop >= sops) { |
448 | sma->sem_base[sop->sem_num].semval -= sop->sem_op; |
449 | sop--; |
450 | } |
451 | |
452 | return result; |
453 | } |
454 | |
455 | /** wake_up_sem_queue_prepare(q, error): Prepare wake-up |
456 | * @q: queue entry that must be signaled |
457 | * @error: Error value for the signal |
458 | * |
459 | * Prepare the wake-up of the queue entry q. |
460 | */ |
461 | static void wake_up_sem_queue_prepare(struct list_head *pt, |
462 | struct sem_queue *q, int error) |
463 | { |
464 | if (list_empty(pt)) { |
465 | /* |
466 | * Hold preempt off so that we don't get preempted and have the |
467 | * wakee busy-wait until we're scheduled back on. |
468 | */ |
469 | preempt_disable(); |
470 | } |
471 | q->status = IN_WAKEUP; |
472 | q->pid = error; |
473 | |
474 | list_add_tail(&q->simple_list, pt); |
475 | } |
476 | |
477 | /** |
478 | * wake_up_sem_queue_do(pt) - do the actual wake-up |
479 | * @pt: list of tasks to be woken up |
480 | * |
481 | * Do the actual wake-up. |
482 | * The function is called without any locks held, thus the semaphore array |
483 | * could be destroyed already and the tasks can disappear as soon as the |
484 | * status is set to the actual return code. |
485 | */ |
486 | static void wake_up_sem_queue_do(struct list_head *pt) |
487 | { |
488 | struct sem_queue *q, *t; |
489 | int did_something; |
490 | |
491 | did_something = !list_empty(pt); |
492 | list_for_each_entry_safe(q, t, pt, simple_list) { |
493 | wake_up_process(q->sleeper); |
494 | /* q can disappear immediately after writing q->status. */ |
495 | smp_wmb(); |
496 | q->status = q->pid; |
497 | } |
498 | if (did_something) |
499 | preempt_enable(); |
500 | } |
501 | |
502 | static void unlink_queue(struct sem_array *sma, struct sem_queue *q) |
503 | { |
504 | list_del(&q->list); |
505 | if (q->nsops == 1) |
506 | list_del(&q->simple_list); |
507 | else |
508 | sma->complex_count--; |
509 | } |
510 | |
511 | /** check_restart(sma, q) |
512 | * @sma: semaphore array |
513 | * @q: the operation that just completed |
514 | * |
515 | * update_queue is O(N^2) when it restarts scanning the whole queue of |
516 | * waiting operations. Therefore this function checks if the restart is |
517 | * really necessary. It is called after a previously waiting operation |
518 | * was completed. |
519 | */ |
520 | static int check_restart(struct sem_array *sma, struct sem_queue *q) |
521 | { |
522 | struct sem *curr; |
523 | struct sem_queue *h; |
524 | |
525 | /* if the operation didn't modify the array, then no restart */ |
526 | if (q->alter == 0) |
527 | return 0; |
528 | |
529 | /* pending complex operations are too difficult to analyse */ |
530 | if (sma->complex_count) |
531 | return 1; |
532 | |
533 | /* we were a sleeping complex operation. Too difficult */ |
534 | if (q->nsops > 1) |
535 | return 1; |
536 | |
537 | curr = sma->sem_base + q->sops[0].sem_num; |
538 | |
539 | /* No-one waits on this queue */ |
540 | if (list_empty(&curr->sem_pending)) |
541 | return 0; |
542 | |
543 | /* the new semaphore value */ |
544 | if (curr->semval) { |
545 | /* It is impossible that someone waits for the new value: |
546 | * - q is a previously sleeping simple operation that |
547 | * altered the array. It must be a decrement, because |
548 | * simple increments never sleep. |
549 | * - The value is not 0, thus wait-for-zero won't proceed. |
550 | * - If there are older (higher priority) decrements |
551 | * in the queue, then they have observed the original |
552 | * semval value and couldn't proceed. The operation |
553 | * decremented to value - thus they won't proceed either. |
554 | */ |
555 | BUG_ON(q->sops[0].sem_op >= 0); |
556 | return 0; |
557 | } |
558 | /* |
559 | * semval is 0. Check if there are wait-for-zero semops. |
560 | * They must be the first entries in the per-semaphore simple queue |
561 | */ |
562 | h = list_first_entry(&curr->sem_pending, struct sem_queue, simple_list); |
563 | BUG_ON(h->nsops != 1); |
564 | BUG_ON(h->sops[0].sem_num != q->sops[0].sem_num); |
565 | |
566 | /* Yes, there is a wait-for-zero semop. Restart */ |
567 | if (h->sops[0].sem_op == 0) |
568 | return 1; |
569 | |
570 | /* Again - no-one is waiting for the new value. */ |
571 | return 0; |
572 | } |
573 | |
574 | |
575 | /** |
576 | * update_queue(sma, semnum): Look for tasks that can be completed. |
577 | * @sma: semaphore array. |
578 | * @semnum: semaphore that was modified. |
579 | * @pt: list head for the tasks that must be woken up. |
580 | * |
581 | * update_queue must be called after a semaphore in a semaphore array |
582 | * was modified. If multiple semaphore were modified, then @semnum |
583 | * must be set to -1. |
584 | * The tasks that must be woken up are added to @pt. The return code |
585 | * is stored in q->pid. |
586 | * The function return 1 if at least one semop was completed successfully. |
587 | */ |
588 | static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt) |
589 | { |
590 | struct sem_queue *q; |
591 | struct list_head *walk; |
592 | struct list_head *pending_list; |
593 | int offset; |
594 | int semop_completed = 0; |
595 | |
596 | /* if there are complex operations around, then knowing the semaphore |
597 | * that was modified doesn't help us. Assume that multiple semaphores |
598 | * were modified. |
599 | */ |
600 | if (sma->complex_count) |
601 | semnum = -1; |
602 | |
603 | if (semnum == -1) { |
604 | pending_list = &sma->sem_pending; |
605 | offset = offsetof(struct sem_queue, list); |
606 | } else { |
607 | pending_list = &sma->sem_base[semnum].sem_pending; |
608 | offset = offsetof(struct sem_queue, simple_list); |
609 | } |
610 | |
611 | again: |
612 | walk = pending_list->next; |
613 | while (walk != pending_list) { |
614 | int error, restart; |
615 | |
616 | q = (struct sem_queue *)((char *)walk - offset); |
617 | walk = walk->next; |
618 | |
619 | /* If we are scanning the single sop, per-semaphore list of |
620 | * one semaphore and that semaphore is 0, then it is not |
621 | * necessary to scan the "alter" entries: simple increments |
622 | * that affect only one entry succeed immediately and cannot |
623 | * be in the per semaphore pending queue, and decrements |
624 | * cannot be successful if the value is already 0. |
625 | */ |
626 | if (semnum != -1 && sma->sem_base[semnum].semval == 0 && |
627 | q->alter) |
628 | break; |
629 | |
630 | error = try_atomic_semop(sma, q->sops, q->nsops, |
631 | q->undo, q->pid); |
632 | |
633 | /* Does q->sleeper still need to sleep? */ |
634 | if (error > 0) |
635 | continue; |
636 | |
637 | unlink_queue(sma, q); |
638 | |
639 | if (error) { |
640 | restart = 0; |
641 | } else { |
642 | semop_completed = 1; |
643 | restart = check_restart(sma, q); |
644 | } |
645 | |
646 | wake_up_sem_queue_prepare(pt, q, error); |
647 | if (restart) |
648 | goto again; |
649 | } |
650 | return semop_completed; |
651 | } |
652 | |
653 | /** |
654 | * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue |
655 | * @sma: semaphore array |
656 | * @sops: operations that were performed |
657 | * @nsops: number of operations |
658 | * @otime: force setting otime |
659 | * @pt: list head of the tasks that must be woken up. |
660 | * |
661 | * do_smart_update() does the required called to update_queue, based on the |
662 | * actual changes that were performed on the semaphore array. |
663 | * Note that the function does not do the actual wake-up: the caller is |
664 | * responsible for calling wake_up_sem_queue_do(@pt). |
665 | * It is safe to perform this call after dropping all locks. |
666 | */ |
667 | static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops, |
668 | int otime, struct list_head *pt) |
669 | { |
670 | int i; |
671 | |
672 | if (sma->complex_count || sops == NULL) { |
673 | if (update_queue(sma, -1, pt)) |
674 | otime = 1; |
675 | goto done; |
676 | } |
677 | |
678 | for (i = 0; i < nsops; i++) { |
679 | if (sops[i].sem_op > 0 || |
680 | (sops[i].sem_op < 0 && |
681 | sma->sem_base[sops[i].sem_num].semval == 0)) |
682 | if (update_queue(sma, sops[i].sem_num, pt)) |
683 | otime = 1; |
684 | } |
685 | done: |
686 | if (otime) |
687 | sma->sem_otime = get_seconds(); |
688 | } |
689 | |
690 | |
691 | /* The following counts are associated to each semaphore: |
692 | * semncnt number of tasks waiting on semval being nonzero |
693 | * semzcnt number of tasks waiting on semval being zero |
694 | * This model assumes that a task waits on exactly one semaphore. |
695 | * Since semaphore operations are to be performed atomically, tasks actually |
696 | * wait on a whole sequence of semaphores simultaneously. |
697 | * The counts we return here are a rough approximation, but still |
698 | * warrant that semncnt+semzcnt>0 if the task is on the pending queue. |
699 | */ |
700 | static int count_semncnt (struct sem_array * sma, ushort semnum) |
701 | { |
702 | int semncnt; |
703 | struct sem_queue * q; |
704 | |
705 | semncnt = 0; |
706 | list_for_each_entry(q, &sma->sem_pending, list) { |
707 | struct sembuf * sops = q->sops; |
708 | int nsops = q->nsops; |
709 | int i; |
710 | for (i = 0; i < nsops; i++) |
711 | if (sops[i].sem_num == semnum |
712 | && (sops[i].sem_op < 0) |
713 | && !(sops[i].sem_flg & IPC_NOWAIT)) |
714 | semncnt++; |
715 | } |
716 | return semncnt; |
717 | } |
718 | |
719 | static int count_semzcnt (struct sem_array * sma, ushort semnum) |
720 | { |
721 | int semzcnt; |
722 | struct sem_queue * q; |
723 | |
724 | semzcnt = 0; |
725 | list_for_each_entry(q, &sma->sem_pending, list) { |
726 | struct sembuf * sops = q->sops; |
727 | int nsops = q->nsops; |
728 | int i; |
729 | for (i = 0; i < nsops; i++) |
730 | if (sops[i].sem_num == semnum |
731 | && (sops[i].sem_op == 0) |
732 | && !(sops[i].sem_flg & IPC_NOWAIT)) |
733 | semzcnt++; |
734 | } |
735 | return semzcnt; |
736 | } |
737 | |
738 | /* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked |
739 | * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex |
740 | * remains locked on exit. |
741 | */ |
742 | static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) |
743 | { |
744 | struct sem_undo *un, *tu; |
745 | struct sem_queue *q, *tq; |
746 | struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
747 | struct list_head tasks; |
748 | |
749 | /* Free the existing undo structures for this semaphore set. */ |
750 | assert_spin_locked(&sma->sem_perm.lock); |
751 | list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { |
752 | list_del(&un->list_id); |
753 | spin_lock(&un->ulp->lock); |
754 | un->semid = -1; |
755 | list_del_rcu(&un->list_proc); |
756 | spin_unlock(&un->ulp->lock); |
757 | kfree_rcu(un, rcu); |
758 | } |
759 | |
760 | /* Wake up all pending processes and let them fail with EIDRM. */ |
761 | INIT_LIST_HEAD(&tasks); |
762 | list_for_each_entry_safe(q, tq, &sma->sem_pending, list) { |
763 | unlink_queue(sma, q); |
764 | wake_up_sem_queue_prepare(&tasks, q, -EIDRM); |
765 | } |
766 | |
767 | /* Remove the semaphore set from the IDR */ |
768 | sem_rmid(ns, sma); |
769 | sem_unlock(sma); |
770 | |
771 | wake_up_sem_queue_do(&tasks); |
772 | ns->used_sems -= sma->sem_nsems; |
773 | security_sem_free(sma); |
774 | ipc_rcu_putref(sma); |
775 | } |
776 | |
777 | static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) |
778 | { |
779 | switch(version) { |
780 | case IPC_64: |
781 | return copy_to_user(buf, in, sizeof(*in)); |
782 | case IPC_OLD: |
783 | { |
784 | struct semid_ds out; |
785 | |
786 | memset(&out, 0, sizeof(out)); |
787 | |
788 | ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); |
789 | |
790 | out.sem_otime = in->sem_otime; |
791 | out.sem_ctime = in->sem_ctime; |
792 | out.sem_nsems = in->sem_nsems; |
793 | |
794 | return copy_to_user(buf, &out, sizeof(out)); |
795 | } |
796 | default: |
797 | return -EINVAL; |
798 | } |
799 | } |
800 | |
801 | static int semctl_nolock(struct ipc_namespace *ns, int semid, |
802 | int cmd, int version, union semun arg) |
803 | { |
804 | int err; |
805 | struct sem_array *sma; |
806 | |
807 | switch(cmd) { |
808 | case IPC_INFO: |
809 | case SEM_INFO: |
810 | { |
811 | struct seminfo seminfo; |
812 | int max_id; |
813 | |
814 | err = security_sem_semctl(NULL, cmd); |
815 | if (err) |
816 | return err; |
817 | |
818 | memset(&seminfo,0,sizeof(seminfo)); |
819 | seminfo.semmni = ns->sc_semmni; |
820 | seminfo.semmns = ns->sc_semmns; |
821 | seminfo.semmsl = ns->sc_semmsl; |
822 | seminfo.semopm = ns->sc_semopm; |
823 | seminfo.semvmx = SEMVMX; |
824 | seminfo.semmnu = SEMMNU; |
825 | seminfo.semmap = SEMMAP; |
826 | seminfo.semume = SEMUME; |
827 | down_read(&sem_ids(ns).rw_mutex); |
828 | if (cmd == SEM_INFO) { |
829 | seminfo.semusz = sem_ids(ns).in_use; |
830 | seminfo.semaem = ns->used_sems; |
831 | } else { |
832 | seminfo.semusz = SEMUSZ; |
833 | seminfo.semaem = SEMAEM; |
834 | } |
835 | max_id = ipc_get_maxid(&sem_ids(ns)); |
836 | up_read(&sem_ids(ns).rw_mutex); |
837 | if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo))) |
838 | return -EFAULT; |
839 | return (max_id < 0) ? 0: max_id; |
840 | } |
841 | case IPC_STAT: |
842 | case SEM_STAT: |
843 | { |
844 | struct semid64_ds tbuf; |
845 | int id; |
846 | |
847 | if (cmd == SEM_STAT) { |
848 | sma = sem_lock(ns, semid); |
849 | if (IS_ERR(sma)) |
850 | return PTR_ERR(sma); |
851 | id = sma->sem_perm.id; |
852 | } else { |
853 | sma = sem_lock_check(ns, semid); |
854 | if (IS_ERR(sma)) |
855 | return PTR_ERR(sma); |
856 | id = 0; |
857 | } |
858 | |
859 | err = -EACCES; |
860 | if (ipcperms(ns, &sma->sem_perm, S_IRUGO)) |
861 | goto out_unlock; |
862 | |
863 | err = security_sem_semctl(sma, cmd); |
864 | if (err) |
865 | goto out_unlock; |
866 | |
867 | memset(&tbuf, 0, sizeof(tbuf)); |
868 | |
869 | kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm); |
870 | tbuf.sem_otime = sma->sem_otime; |
871 | tbuf.sem_ctime = sma->sem_ctime; |
872 | tbuf.sem_nsems = sma->sem_nsems; |
873 | sem_unlock(sma); |
874 | if (copy_semid_to_user (arg.buf, &tbuf, version)) |
875 | return -EFAULT; |
876 | return id; |
877 | } |
878 | default: |
879 | return -EINVAL; |
880 | } |
881 | out_unlock: |
882 | sem_unlock(sma); |
883 | return err; |
884 | } |
885 | |
886 | static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, |
887 | int cmd, int version, union semun arg) |
888 | { |
889 | struct sem_array *sma; |
890 | struct sem* curr; |
891 | int err; |
892 | ushort fast_sem_io[SEMMSL_FAST]; |
893 | ushort* sem_io = fast_sem_io; |
894 | int nsems; |
895 | struct list_head tasks; |
896 | |
897 | sma = sem_lock_check(ns, semid); |
898 | if (IS_ERR(sma)) |
899 | return PTR_ERR(sma); |
900 | |
901 | INIT_LIST_HEAD(&tasks); |
902 | nsems = sma->sem_nsems; |
903 | |
904 | err = -EACCES; |
905 | if (ipcperms(ns, &sma->sem_perm, |
906 | (cmd == SETVAL || cmd == SETALL) ? S_IWUGO : S_IRUGO)) |
907 | goto out_unlock; |
908 | |
909 | err = security_sem_semctl(sma, cmd); |
910 | if (err) |
911 | goto out_unlock; |
912 | |
913 | err = -EACCES; |
914 | switch (cmd) { |
915 | case GETALL: |
916 | { |
917 | ushort __user *array = arg.array; |
918 | int i; |
919 | |
920 | if(nsems > SEMMSL_FAST) { |
921 | sem_getref_and_unlock(sma); |
922 | |
923 | sem_io = ipc_alloc(sizeof(ushort)*nsems); |
924 | if(sem_io == NULL) { |
925 | sem_putref(sma); |
926 | return -ENOMEM; |
927 | } |
928 | |
929 | sem_lock_and_putref(sma); |
930 | if (sma->sem_perm.deleted) { |
931 | sem_unlock(sma); |
932 | err = -EIDRM; |
933 | goto out_free; |
934 | } |
935 | } |
936 | |
937 | for (i = 0; i < sma->sem_nsems; i++) |
938 | sem_io[i] = sma->sem_base[i].semval; |
939 | sem_unlock(sma); |
940 | err = 0; |
941 | if(copy_to_user(array, sem_io, nsems*sizeof(ushort))) |
942 | err = -EFAULT; |
943 | goto out_free; |
944 | } |
945 | case SETALL: |
946 | { |
947 | int i; |
948 | struct sem_undo *un; |
949 | |
950 | sem_getref_and_unlock(sma); |
951 | |
952 | if(nsems > SEMMSL_FAST) { |
953 | sem_io = ipc_alloc(sizeof(ushort)*nsems); |
954 | if(sem_io == NULL) { |
955 | sem_putref(sma); |
956 | return -ENOMEM; |
957 | } |
958 | } |
959 | |
960 | if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) { |
961 | sem_putref(sma); |
962 | err = -EFAULT; |
963 | goto out_free; |
964 | } |
965 | |
966 | for (i = 0; i < nsems; i++) { |
967 | if (sem_io[i] > SEMVMX) { |
968 | sem_putref(sma); |
969 | err = -ERANGE; |
970 | goto out_free; |
971 | } |
972 | } |
973 | sem_lock_and_putref(sma); |
974 | if (sma->sem_perm.deleted) { |
975 | sem_unlock(sma); |
976 | err = -EIDRM; |
977 | goto out_free; |
978 | } |
979 | |
980 | for (i = 0; i < nsems; i++) |
981 | sma->sem_base[i].semval = sem_io[i]; |
982 | |
983 | assert_spin_locked(&sma->sem_perm.lock); |
984 | list_for_each_entry(un, &sma->list_id, list_id) { |
985 | for (i = 0; i < nsems; i++) |
986 | un->semadj[i] = 0; |
987 | } |
988 | sma->sem_ctime = get_seconds(); |
989 | /* maybe some queued-up processes were waiting for this */ |
990 | do_smart_update(sma, NULL, 0, 0, &tasks); |
991 | err = 0; |
992 | goto out_unlock; |
993 | } |
994 | /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */ |
995 | } |
996 | err = -EINVAL; |
997 | if(semnum < 0 || semnum >= nsems) |
998 | goto out_unlock; |
999 | |
1000 | curr = &sma->sem_base[semnum]; |
1001 | |
1002 | switch (cmd) { |
1003 | case GETVAL: |
1004 | err = curr->semval; |
1005 | goto out_unlock; |
1006 | case GETPID: |
1007 | err = curr->sempid; |
1008 | goto out_unlock; |
1009 | case GETNCNT: |
1010 | err = count_semncnt(sma,semnum); |
1011 | goto out_unlock; |
1012 | case GETZCNT: |
1013 | err = count_semzcnt(sma,semnum); |
1014 | goto out_unlock; |
1015 | case SETVAL: |
1016 | { |
1017 | int val = arg.val; |
1018 | struct sem_undo *un; |
1019 | |
1020 | err = -ERANGE; |
1021 | if (val > SEMVMX || val < 0) |
1022 | goto out_unlock; |
1023 | |
1024 | assert_spin_locked(&sma->sem_perm.lock); |
1025 | list_for_each_entry(un, &sma->list_id, list_id) |
1026 | un->semadj[semnum] = 0; |
1027 | |
1028 | curr->semval = val; |
1029 | curr->sempid = task_tgid_vnr(current); |
1030 | sma->sem_ctime = get_seconds(); |
1031 | /* maybe some queued-up processes were waiting for this */ |
1032 | do_smart_update(sma, NULL, 0, 0, &tasks); |
1033 | err = 0; |
1034 | goto out_unlock; |
1035 | } |
1036 | } |
1037 | out_unlock: |
1038 | sem_unlock(sma); |
1039 | wake_up_sem_queue_do(&tasks); |
1040 | |
1041 | out_free: |
1042 | if(sem_io != fast_sem_io) |
1043 | ipc_free(sem_io, sizeof(ushort)*nsems); |
1044 | return err; |
1045 | } |
1046 | |
1047 | static inline unsigned long |
1048 | copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) |
1049 | { |
1050 | switch(version) { |
1051 | case IPC_64: |
1052 | if (copy_from_user(out, buf, sizeof(*out))) |
1053 | return -EFAULT; |
1054 | return 0; |
1055 | case IPC_OLD: |
1056 | { |
1057 | struct semid_ds tbuf_old; |
1058 | |
1059 | if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) |
1060 | return -EFAULT; |
1061 | |
1062 | out->sem_perm.uid = tbuf_old.sem_perm.uid; |
1063 | out->sem_perm.gid = tbuf_old.sem_perm.gid; |
1064 | out->sem_perm.mode = tbuf_old.sem_perm.mode; |
1065 | |
1066 | return 0; |
1067 | } |
1068 | default: |
1069 | return -EINVAL; |
1070 | } |
1071 | } |
1072 | |
1073 | /* |
1074 | * This function handles some semctl commands which require the rw_mutex |
1075 | * to be held in write mode. |
1076 | * NOTE: no locks must be held, the rw_mutex is taken inside this function. |
1077 | */ |
1078 | static int semctl_down(struct ipc_namespace *ns, int semid, |
1079 | int cmd, int version, union semun arg) |
1080 | { |
1081 | struct sem_array *sma; |
1082 | int err; |
1083 | struct semid64_ds semid64; |
1084 | struct kern_ipc_perm *ipcp; |
1085 | |
1086 | if(cmd == IPC_SET) { |
1087 | if (copy_semid_from_user(&semid64, arg.buf, version)) |
1088 | return -EFAULT; |
1089 | } |
1090 | |
1091 | ipcp = ipcctl_pre_down(ns, &sem_ids(ns), semid, cmd, |
1092 | &semid64.sem_perm, 0); |
1093 | if (IS_ERR(ipcp)) |
1094 | return PTR_ERR(ipcp); |
1095 | |
1096 | sma = container_of(ipcp, struct sem_array, sem_perm); |
1097 | |
1098 | err = security_sem_semctl(sma, cmd); |
1099 | if (err) |
1100 | goto out_unlock; |
1101 | |
1102 | switch(cmd){ |
1103 | case IPC_RMID: |
1104 | freeary(ns, ipcp); |
1105 | goto out_up; |
1106 | case IPC_SET: |
1107 | ipc_update_perm(&semid64.sem_perm, ipcp); |
1108 | sma->sem_ctime = get_seconds(); |
1109 | break; |
1110 | default: |
1111 | err = -EINVAL; |
1112 | } |
1113 | |
1114 | out_unlock: |
1115 | sem_unlock(sma); |
1116 | out_up: |
1117 | up_write(&sem_ids(ns).rw_mutex); |
1118 | return err; |
1119 | } |
1120 | |
1121 | SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg) |
1122 | { |
1123 | int err = -EINVAL; |
1124 | int version; |
1125 | struct ipc_namespace *ns; |
1126 | |
1127 | if (semid < 0) |
1128 | return -EINVAL; |
1129 | |
1130 | version = ipc_parse_version(&cmd); |
1131 | ns = current->nsproxy->ipc_ns; |
1132 | |
1133 | switch(cmd) { |
1134 | case IPC_INFO: |
1135 | case SEM_INFO: |
1136 | case IPC_STAT: |
1137 | case SEM_STAT: |
1138 | err = semctl_nolock(ns, semid, cmd, version, arg); |
1139 | return err; |
1140 | case GETALL: |
1141 | case GETVAL: |
1142 | case GETPID: |
1143 | case GETNCNT: |
1144 | case GETZCNT: |
1145 | case SETVAL: |
1146 | case SETALL: |
1147 | err = semctl_main(ns,semid,semnum,cmd,version,arg); |
1148 | return err; |
1149 | case IPC_RMID: |
1150 | case IPC_SET: |
1151 | err = semctl_down(ns, semid, cmd, version, arg); |
1152 | return err; |
1153 | default: |
1154 | return -EINVAL; |
1155 | } |
1156 | } |
1157 | #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS |
1158 | asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg) |
1159 | { |
1160 | return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg); |
1161 | } |
1162 | SYSCALL_ALIAS(sys_semctl, SyS_semctl); |
1163 | #endif |
1164 | |
1165 | /* If the task doesn't already have a undo_list, then allocate one |
1166 | * here. We guarantee there is only one thread using this undo list, |
1167 | * and current is THE ONE |
1168 | * |
1169 | * If this allocation and assignment succeeds, but later |
1170 | * portions of this code fail, there is no need to free the sem_undo_list. |
1171 | * Just let it stay associated with the task, and it'll be freed later |
1172 | * at exit time. |
1173 | * |
1174 | * This can block, so callers must hold no locks. |
1175 | */ |
1176 | static inline int get_undo_list(struct sem_undo_list **undo_listp) |
1177 | { |
1178 | struct sem_undo_list *undo_list; |
1179 | |
1180 | undo_list = current->sysvsem.undo_list; |
1181 | if (!undo_list) { |
1182 | undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL); |
1183 | if (undo_list == NULL) |
1184 | return -ENOMEM; |
1185 | spin_lock_init(&undo_list->lock); |
1186 | atomic_set(&undo_list->refcnt, 1); |
1187 | INIT_LIST_HEAD(&undo_list->list_proc); |
1188 | |
1189 | current->sysvsem.undo_list = undo_list; |
1190 | } |
1191 | *undo_listp = undo_list; |
1192 | return 0; |
1193 | } |
1194 | |
1195 | static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) |
1196 | { |
1197 | struct sem_undo *un; |
1198 | |
1199 | list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) { |
1200 | if (un->semid == semid) |
1201 | return un; |
1202 | } |
1203 | return NULL; |
1204 | } |
1205 | |
1206 | static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) |
1207 | { |
1208 | struct sem_undo *un; |
1209 | |
1210 | assert_spin_locked(&ulp->lock); |
1211 | |
1212 | un = __lookup_undo(ulp, semid); |
1213 | if (un) { |
1214 | list_del_rcu(&un->list_proc); |
1215 | list_add_rcu(&un->list_proc, &ulp->list_proc); |
1216 | } |
1217 | return un; |
1218 | } |
1219 | |
1220 | /** |
1221 | * find_alloc_undo - Lookup (and if not present create) undo array |
1222 | * @ns: namespace |
1223 | * @semid: semaphore array id |
1224 | * |
1225 | * The function looks up (and if not present creates) the undo structure. |
1226 | * The size of the undo structure depends on the size of the semaphore |
1227 | * array, thus the alloc path is not that straightforward. |
1228 | * Lifetime-rules: sem_undo is rcu-protected, on success, the function |
1229 | * performs a rcu_read_lock(). |
1230 | */ |
1231 | static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) |
1232 | { |
1233 | struct sem_array *sma; |
1234 | struct sem_undo_list *ulp; |
1235 | struct sem_undo *un, *new; |
1236 | int nsems; |
1237 | int error; |
1238 | |
1239 | error = get_undo_list(&ulp); |
1240 | if (error) |
1241 | return ERR_PTR(error); |
1242 | |
1243 | rcu_read_lock(); |
1244 | spin_lock(&ulp->lock); |
1245 | un = lookup_undo(ulp, semid); |
1246 | spin_unlock(&ulp->lock); |
1247 | if (likely(un!=NULL)) |
1248 | goto out; |
1249 | rcu_read_unlock(); |
1250 | |
1251 | /* no undo structure around - allocate one. */ |
1252 | /* step 1: figure out the size of the semaphore array */ |
1253 | sma = sem_lock_check(ns, semid); |
1254 | if (IS_ERR(sma)) |
1255 | return ERR_CAST(sma); |
1256 | |
1257 | nsems = sma->sem_nsems; |
1258 | sem_getref_and_unlock(sma); |
1259 | |
1260 | /* step 2: allocate new undo structure */ |
1261 | new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL); |
1262 | if (!new) { |
1263 | sem_putref(sma); |
1264 | return ERR_PTR(-ENOMEM); |
1265 | } |
1266 | |
1267 | /* step 3: Acquire the lock on semaphore array */ |
1268 | sem_lock_and_putref(sma); |
1269 | if (sma->sem_perm.deleted) { |
1270 | sem_unlock(sma); |
1271 | kfree(new); |
1272 | un = ERR_PTR(-EIDRM); |
1273 | goto out; |
1274 | } |
1275 | spin_lock(&ulp->lock); |
1276 | |
1277 | /* |
1278 | * step 4: check for races: did someone else allocate the undo struct? |
1279 | */ |
1280 | un = lookup_undo(ulp, semid); |
1281 | if (un) { |
1282 | kfree(new); |
1283 | goto success; |
1284 | } |
1285 | /* step 5: initialize & link new undo structure */ |
1286 | new->semadj = (short *) &new[1]; |
1287 | new->ulp = ulp; |
1288 | new->semid = semid; |
1289 | assert_spin_locked(&ulp->lock); |
1290 | list_add_rcu(&new->list_proc, &ulp->list_proc); |
1291 | assert_spin_locked(&sma->sem_perm.lock); |
1292 | list_add(&new->list_id, &sma->list_id); |
1293 | un = new; |
1294 | |
1295 | success: |
1296 | spin_unlock(&ulp->lock); |
1297 | rcu_read_lock(); |
1298 | sem_unlock(sma); |
1299 | out: |
1300 | return un; |
1301 | } |
1302 | |
1303 | |
1304 | /** |
1305 | * get_queue_result - Retrieve the result code from sem_queue |
1306 | * @q: Pointer to queue structure |
1307 | * |
1308 | * Retrieve the return code from the pending queue. If IN_WAKEUP is found in |
1309 | * q->status, then we must loop until the value is replaced with the final |
1310 | * value: This may happen if a task is woken up by an unrelated event (e.g. |
1311 | * signal) and in parallel the task is woken up by another task because it got |
1312 | * the requested semaphores. |
1313 | * |
1314 | * The function can be called with or without holding the semaphore spinlock. |
1315 | */ |
1316 | static int get_queue_result(struct sem_queue *q) |
1317 | { |
1318 | int error; |
1319 | |
1320 | error = q->status; |
1321 | while (unlikely(error == IN_WAKEUP)) { |
1322 | cpu_relax(); |
1323 | error = q->status; |
1324 | } |
1325 | |
1326 | return error; |
1327 | } |
1328 | |
1329 | |
1330 | SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, |
1331 | unsigned, nsops, const struct timespec __user *, timeout) |
1332 | { |
1333 | int error = -EINVAL; |
1334 | struct sem_array *sma; |
1335 | struct sembuf fast_sops[SEMOPM_FAST]; |
1336 | struct sembuf* sops = fast_sops, *sop; |
1337 | struct sem_undo *un; |
1338 | int undos = 0, alter = 0, max; |
1339 | struct sem_queue queue; |
1340 | unsigned long jiffies_left = 0; |
1341 | struct ipc_namespace *ns; |
1342 | struct list_head tasks; |
1343 | |
1344 | ns = current->nsproxy->ipc_ns; |
1345 | |
1346 | if (nsops < 1 || semid < 0) |
1347 | return -EINVAL; |
1348 | if (nsops > ns->sc_semopm) |
1349 | return -E2BIG; |
1350 | if(nsops > SEMOPM_FAST) { |
1351 | sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL); |
1352 | if(sops==NULL) |
1353 | return -ENOMEM; |
1354 | } |
1355 | if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) { |
1356 | error=-EFAULT; |
1357 | goto out_free; |
1358 | } |
1359 | if (timeout) { |
1360 | struct timespec _timeout; |
1361 | if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) { |
1362 | error = -EFAULT; |
1363 | goto out_free; |
1364 | } |
1365 | if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 || |
1366 | _timeout.tv_nsec >= 1000000000L) { |
1367 | error = -EINVAL; |
1368 | goto out_free; |
1369 | } |
1370 | jiffies_left = timespec_to_jiffies(&_timeout); |
1371 | } |
1372 | max = 0; |
1373 | for (sop = sops; sop < sops + nsops; sop++) { |
1374 | if (sop->sem_num >= max) |
1375 | max = sop->sem_num; |
1376 | if (sop->sem_flg & SEM_UNDO) |
1377 | undos = 1; |
1378 | if (sop->sem_op != 0) |
1379 | alter = 1; |
1380 | } |
1381 | |
1382 | if (undos) { |
1383 | un = find_alloc_undo(ns, semid); |
1384 | if (IS_ERR(un)) { |
1385 | error = PTR_ERR(un); |
1386 | goto out_free; |
1387 | } |
1388 | } else |
1389 | un = NULL; |
1390 | |
1391 | INIT_LIST_HEAD(&tasks); |
1392 | |
1393 | sma = sem_lock_check(ns, semid); |
1394 | if (IS_ERR(sma)) { |
1395 | if (un) |
1396 | rcu_read_unlock(); |
1397 | error = PTR_ERR(sma); |
1398 | goto out_free; |
1399 | } |
1400 | |
1401 | /* |
1402 | * semid identifiers are not unique - find_alloc_undo may have |
1403 | * allocated an undo structure, it was invalidated by an RMID |
1404 | * and now a new array with received the same id. Check and fail. |
1405 | * This case can be detected checking un->semid. The existence of |
1406 | * "un" itself is guaranteed by rcu. |
1407 | */ |
1408 | error = -EIDRM; |
1409 | if (un) { |
1410 | if (un->semid == -1) { |
1411 | rcu_read_unlock(); |
1412 | goto out_unlock_free; |
1413 | } else { |
1414 | /* |
1415 | * rcu lock can be released, "un" cannot disappear: |
1416 | * - sem_lock is acquired, thus IPC_RMID is |
1417 | * impossible. |
1418 | * - exit_sem is impossible, it always operates on |
1419 | * current (or a dead task). |
1420 | */ |
1421 | |
1422 | rcu_read_unlock(); |
1423 | } |
1424 | } |
1425 | |
1426 | error = -EFBIG; |
1427 | if (max >= sma->sem_nsems) |
1428 | goto out_unlock_free; |
1429 | |
1430 | error = -EACCES; |
1431 | if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) |
1432 | goto out_unlock_free; |
1433 | |
1434 | error = security_sem_semop(sma, sops, nsops, alter); |
1435 | if (error) |
1436 | goto out_unlock_free; |
1437 | |
1438 | error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current)); |
1439 | if (error <= 0) { |
1440 | if (alter && error == 0) |
1441 | do_smart_update(sma, sops, nsops, 1, &tasks); |
1442 | |
1443 | goto out_unlock_free; |
1444 | } |
1445 | |
1446 | /* We need to sleep on this operation, so we put the current |
1447 | * task into the pending queue and go to sleep. |
1448 | */ |
1449 | |
1450 | queue.sops = sops; |
1451 | queue.nsops = nsops; |
1452 | queue.undo = un; |
1453 | queue.pid = task_tgid_vnr(current); |
1454 | queue.alter = alter; |
1455 | if (alter) |
1456 | list_add_tail(&queue.list, &sma->sem_pending); |
1457 | else |
1458 | list_add(&queue.list, &sma->sem_pending); |
1459 | |
1460 | if (nsops == 1) { |
1461 | struct sem *curr; |
1462 | curr = &sma->sem_base[sops->sem_num]; |
1463 | |
1464 | if (alter) |
1465 | list_add_tail(&queue.simple_list, &curr->sem_pending); |
1466 | else |
1467 | list_add(&queue.simple_list, &curr->sem_pending); |
1468 | } else { |
1469 | INIT_LIST_HEAD(&queue.simple_list); |
1470 | sma->complex_count++; |
1471 | } |
1472 | |
1473 | queue.status = -EINTR; |
1474 | queue.sleeper = current; |
1475 | |
1476 | sleep_again: |
1477 | current->state = TASK_INTERRUPTIBLE; |
1478 | sem_unlock(sma); |
1479 | |
1480 | if (timeout) |
1481 | jiffies_left = schedule_timeout(jiffies_left); |
1482 | else |
1483 | schedule(); |
1484 | |
1485 | error = get_queue_result(&queue); |
1486 | |
1487 | if (error != -EINTR) { |
1488 | /* fast path: update_queue already obtained all requested |
1489 | * resources. |
1490 | * Perform a smp_mb(): User space could assume that semop() |
1491 | * is a memory barrier: Without the mb(), the cpu could |
1492 | * speculatively read in user space stale data that was |
1493 | * overwritten by the previous owner of the semaphore. |
1494 | */ |
1495 | smp_mb(); |
1496 | |
1497 | goto out_free; |
1498 | } |
1499 | |
1500 | sma = sem_lock(ns, semid); |
1501 | |
1502 | /* |
1503 | * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing. |
1504 | */ |
1505 | error = get_queue_result(&queue); |
1506 | |
1507 | /* |
1508 | * Array removed? If yes, leave without sem_unlock(). |
1509 | */ |
1510 | if (IS_ERR(sma)) { |
1511 | goto out_free; |
1512 | } |
1513 | |
1514 | |
1515 | /* |
1516 | * If queue.status != -EINTR we are woken up by another process. |
1517 | * Leave without unlink_queue(), but with sem_unlock(). |
1518 | */ |
1519 | |
1520 | if (error != -EINTR) { |
1521 | goto out_unlock_free; |
1522 | } |
1523 | |
1524 | /* |
1525 | * If an interrupt occurred we have to clean up the queue |
1526 | */ |
1527 | if (timeout && jiffies_left == 0) |
1528 | error = -EAGAIN; |
1529 | |
1530 | /* |
1531 | * If the wakeup was spurious, just retry |
1532 | */ |
1533 | if (error == -EINTR && !signal_pending(current)) |
1534 | goto sleep_again; |
1535 | |
1536 | unlink_queue(sma, &queue); |
1537 | |
1538 | out_unlock_free: |
1539 | sem_unlock(sma); |
1540 | |
1541 | wake_up_sem_queue_do(&tasks); |
1542 | out_free: |
1543 | if(sops != fast_sops) |
1544 | kfree(sops); |
1545 | return error; |
1546 | } |
1547 | |
1548 | SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, |
1549 | unsigned, nsops) |
1550 | { |
1551 | return sys_semtimedop(semid, tsops, nsops, NULL); |
1552 | } |
1553 | |
1554 | /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between |
1555 | * parent and child tasks. |
1556 | */ |
1557 | |
1558 | int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) |
1559 | { |
1560 | struct sem_undo_list *undo_list; |
1561 | int error; |
1562 | |
1563 | if (clone_flags & CLONE_SYSVSEM) { |
1564 | error = get_undo_list(&undo_list); |
1565 | if (error) |
1566 | return error; |
1567 | atomic_inc(&undo_list->refcnt); |
1568 | tsk->sysvsem.undo_list = undo_list; |
1569 | } else |
1570 | tsk->sysvsem.undo_list = NULL; |
1571 | |
1572 | return 0; |
1573 | } |
1574 | |
1575 | /* |
1576 | * add semadj values to semaphores, free undo structures. |
1577 | * undo structures are not freed when semaphore arrays are destroyed |
1578 | * so some of them may be out of date. |
1579 | * IMPLEMENTATION NOTE: There is some confusion over whether the |
1580 | * set of adjustments that needs to be done should be done in an atomic |
1581 | * manner or not. That is, if we are attempting to decrement the semval |
1582 | * should we queue up and wait until we can do so legally? |
1583 | * The original implementation attempted to do this (queue and wait). |
1584 | * The current implementation does not do so. The POSIX standard |
1585 | * and SVID should be consulted to determine what behavior is mandated. |
1586 | */ |
1587 | void exit_sem(struct task_struct *tsk) |
1588 | { |
1589 | struct sem_undo_list *ulp; |
1590 | |
1591 | ulp = tsk->sysvsem.undo_list; |
1592 | if (!ulp) |
1593 | return; |
1594 | tsk->sysvsem.undo_list = NULL; |
1595 | |
1596 | if (!atomic_dec_and_test(&ulp->refcnt)) |
1597 | return; |
1598 | |
1599 | for (;;) { |
1600 | struct sem_array *sma; |
1601 | struct sem_undo *un; |
1602 | struct list_head tasks; |
1603 | int semid; |
1604 | int i; |
1605 | |
1606 | rcu_read_lock(); |
1607 | un = list_entry_rcu(ulp->list_proc.next, |
1608 | struct sem_undo, list_proc); |
1609 | if (&un->list_proc == &ulp->list_proc) |
1610 | semid = -1; |
1611 | else |
1612 | semid = un->semid; |
1613 | rcu_read_unlock(); |
1614 | |
1615 | if (semid == -1) |
1616 | break; |
1617 | |
1618 | sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid); |
1619 | |
1620 | /* exit_sem raced with IPC_RMID, nothing to do */ |
1621 | if (IS_ERR(sma)) |
1622 | continue; |
1623 | |
1624 | un = __lookup_undo(ulp, semid); |
1625 | if (un == NULL) { |
1626 | /* exit_sem raced with IPC_RMID+semget() that created |
1627 | * exactly the same semid. Nothing to do. |
1628 | */ |
1629 | sem_unlock(sma); |
1630 | continue; |
1631 | } |
1632 | |
1633 | /* remove un from the linked lists */ |
1634 | assert_spin_locked(&sma->sem_perm.lock); |
1635 | list_del(&un->list_id); |
1636 | |
1637 | spin_lock(&ulp->lock); |
1638 | list_del_rcu(&un->list_proc); |
1639 | spin_unlock(&ulp->lock); |
1640 | |
1641 | /* perform adjustments registered in un */ |
1642 | for (i = 0; i < sma->sem_nsems; i++) { |
1643 | struct sem * semaphore = &sma->sem_base[i]; |
1644 | if (un->semadj[i]) { |
1645 | semaphore->semval += un->semadj[i]; |
1646 | /* |
1647 | * Range checks of the new semaphore value, |
1648 | * not defined by sus: |
1649 | * - Some unices ignore the undo entirely |
1650 | * (e.g. HP UX 11i 11.22, Tru64 V5.1) |
1651 | * - some cap the value (e.g. FreeBSD caps |
1652 | * at 0, but doesn't enforce SEMVMX) |
1653 | * |
1654 | * Linux caps the semaphore value, both at 0 |
1655 | * and at SEMVMX. |
1656 | * |
1657 | * Manfred <manfred@colorfullife.com> |
1658 | */ |
1659 | if (semaphore->semval < 0) |
1660 | semaphore->semval = 0; |
1661 | if (semaphore->semval > SEMVMX) |
1662 | semaphore->semval = SEMVMX; |
1663 | semaphore->sempid = task_tgid_vnr(current); |
1664 | } |
1665 | } |
1666 | /* maybe some queued-up processes were waiting for this */ |
1667 | INIT_LIST_HEAD(&tasks); |
1668 | do_smart_update(sma, NULL, 0, 1, &tasks); |
1669 | sem_unlock(sma); |
1670 | wake_up_sem_queue_do(&tasks); |
1671 | |
1672 | kfree_rcu(un, rcu); |
1673 | } |
1674 | kfree(ulp); |
1675 | } |
1676 | |
1677 | #ifdef CONFIG_PROC_FS |
1678 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it) |
1679 | { |
1680 | struct sem_array *sma = it; |
1681 | |
1682 | return seq_printf(s, |
1683 | "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n", |
1684 | sma->sem_perm.key, |
1685 | sma->sem_perm.id, |
1686 | sma->sem_perm.mode, |
1687 | sma->sem_nsems, |
1688 | sma->sem_perm.uid, |
1689 | sma->sem_perm.gid, |
1690 | sma->sem_perm.cuid, |
1691 | sma->sem_perm.cgid, |
1692 | sma->sem_otime, |
1693 | sma->sem_ctime); |
1694 | } |
1695 | #endif |
1696 |
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