1 /*
2 * linux/ipc/sem.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
5 *
6 * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
7 * This code underwent a massive rewrite in order to solve some problems
8 * with the original code. In particular the original code failed to
9 * wake up processes that were waiting for semval to go to 0 if the
10 * value went to 0 and was then incremented rapidly enough. In solving
11 * this problem I have also modified the implementation so that it
12 * processes pending operations in a FIFO manner, thus give a guarantee
13 * that processes waiting for a lock on the semaphore won't starve
14 * unless another locking process fails to unlock.
15 * In addition the following two changes in behavior have been introduced:
16 * - The original implementation of semop returned the value
17 * last semaphore element examined on success. This does not
18 * match the manual page specifications, and effectively
19 * allows the user to read the semaphore even if they do not
20 * have read permissions. The implementation now returns 0
21 * on success as stated in the manual page.
22 * - There is some confusion over whether the set of undo adjustments
23 * to be performed at exit should be done in an atomic manner.
24 * That is, if we are attempting to decrement the semval should we queue
25 * up and wait until we can do so legally?
26 * The original implementation attempted to do this.
27 * The current implementation does not do so. This is because I don't
28 * think it is the right thing (TM) to do, and because I couldn't
29 * see a clean way to get the old behavior with the new design.
30 * The POSIX standard and SVID should be consulted to determine
31 * what behavior is mandated.
32 *
33 * Further notes on refinement (Christoph Rohland, December 1998):
34 * - The POSIX standard says, that the undo adjustments simply should
35 * redo. So the current implementation is o.K.
36 * - The previous code had two flaws:
37 * 1) It actively gave the semaphore to the next waiting process
38 * sleeping on the semaphore. Since this process did not have the
39 * cpu this led to many unnecessary context switches and bad
40 * performance. Now we only check which process should be able to
41 * get the semaphore and if this process wants to reduce some
42 * semaphore value we simply wake it up without doing the
43 * operation. So it has to try to get it later. Thus e.g. the
44 * running process may reacquire the semaphore during the current
45 * time slice. If it only waits for zero or increases the semaphore,
46 * we do the operation in advance and wake it up.
47 * 2) It did not wake up all zero waiting processes. We try to do
48 * better but only get the semops right which only wait for zero or
49 * increase. If there are decrement operations in the operations
50 * array we do the same as before.
51 *
52 * With the incarnation of O(1) scheduler, it becomes unnecessary to perform
53 * check/retry algorithm for waking up blocked processes as the new scheduler
54 * is better at handling thread switch than the old one.
55 *
56 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
57 *
58 * SMP-threaded, sysctl's added
59 * (c) 1999 Manfred Spraul <manfreds@colorfullife.com>
60 * Enforced range limit on SEM_UNDO
61 * (c) 2001 Red Hat Inc <alan@redhat.com>
62 * Lockless wakeup
63 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
64 */
65
66 #include <linux/config.h>
67 #include <linux/slab.h>
68 #include <linux/spinlock.h>
69 #include <linux/init.h>
70 #include <linux/proc_fs.h>
71 #include <linux/time.h>
72 #include <linux/smp_lock.h>
73 #include <linux/security.h>
74 #include <linux/syscalls.h>
75 #include <asm/uaccess.h>
76 #include "util.h"
77
78
79 #define sem_lock(id) ((struct sem_array*)ipc_lock(&sem_ids,id))
80 #define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
81 #define sem_rmid(id) ((struct sem_array*)ipc_rmid(&sem_ids,id))
82 #define sem_checkid(sma, semid) \
83 ipc_checkid(&sem_ids,&sma->sem_perm,semid)
84 #define sem_buildid(id, seq) \
85 ipc_buildid(&sem_ids, id, seq)
86 static struct ipc_ids sem_ids;
87
88 static int newary (key_t, int, int);
89 static void freeary (struct sem_array *sma, int id);
90 #ifdef CONFIG_PROC_FS
91 static int sysvipc_sem_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data);
92 #endif
93
94 #define SEMMSL_FAST 256 /* 512 bytes on stack */
95 #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
96
97 /*
98 * linked list protection:
99 * sem_undo.id_next,
100 * sem_array.sem_pending{,last},
101 * sem_array.sem_undo: sem_lock() for read/write
102 * sem_undo.proc_next: only "current" is allowed to read/write that field.
103 *
104 */
105
106 int sem_ctls[4] = {SEMMSL, SEMMNS, SEMOPM, SEMMNI};
107 #define sc_semmsl (sem_ctls[0])
108 #define sc_semmns (sem_ctls[1])
109 #define sc_semopm (sem_ctls[2])
110 #define sc_semmni (sem_ctls[3])
111
112 static int used_sems;
113
114 void __init sem_init (void)
115 {
116 used_sems = 0;
117 ipc_init_ids(&sem_ids,sc_semmni);
118
119 #ifdef CONFIG_PROC_FS
120 create_proc_read_entry("sysvipc/sem", 0, NULL, sysvipc_sem_read_proc, NULL);
121 #endif
122 }
123
124 /*
125 * Lockless wakeup algorithm:
126 * Without the check/retry algorithm a lockless wakeup is possible:
127 * - queue.status is initialized to -EINTR before blocking.
128 * - wakeup is performed by
129 * * unlinking the queue entry from sma->sem_pending
130 * * setting queue.status to IN_WAKEUP
131 * This is the notification for the blocked thread that a
132 * result value is imminent.
133 * * call wake_up_process
134 * * set queue.status to the final value.
135 * - the previously blocked thread checks queue.status:
136 * * if it's IN_WAKEUP, then it must wait until the value changes
137 * * if it's not -EINTR, then the operation was completed by
138 * update_queue. semtimedop can return queue.status without
139 * performing any operation on the semaphore array.
140 * * otherwise it must acquire the spinlock and check what's up.
141 *
142 * The two-stage algorithm is necessary to protect against the following
143 * races:
144 * - if queue.status is set after wake_up_process, then the woken up idle
145 * thread could race forward and try (and fail) to acquire sma->lock
146 * before update_queue had a chance to set queue.status
147 * - if queue.status is written before wake_up_process and if the
148 * blocked process is woken up by a signal between writing
149 * queue.status and the wake_up_process, then the woken up
150 * process could return from semtimedop and die by calling
151 * sys_exit before wake_up_process is called. Then wake_up_process
152 * will oops, because the task structure is already invalid.
153 * (yes, this happened on s390 with sysv msg).
154 *
155 */
156 #define IN_WAKEUP 1
157
158 static int newary (key_t key, int nsems, int semflg)
159 {
160 int id;
161 int retval;
162 struct sem_array *sma;
163 int size;
164
165 if (!nsems)
166 return -EINVAL;
167 if (used_sems + nsems > sc_semmns)
168 return -ENOSPC;
169
170 size = sizeof (*sma) + nsems * sizeof (struct sem);
171 sma = ipc_rcu_alloc(size);
172 if (!sma) {
173 return -ENOMEM;
174 }
175 memset (sma, 0, size);
176
177 sma->sem_perm.mode = (semflg & S_IRWXUGO);
178 sma->sem_perm.key = key;
179
180 sma->sem_perm.security = NULL;
181 retval = security_sem_alloc(sma);
182 if (retval) {
183 ipc_rcu_putref(sma);
184 return retval;
185 }
186
187 id = ipc_addid(&sem_ids, &sma->sem_perm, sc_semmni);
188 if(id == -1) {
189 security_sem_free(sma);
190 ipc_rcu_putref(sma);
191 return -ENOSPC;
192 }
193 used_sems += nsems;
194
195 sma->sem_base = (struct sem *) &sma[1];
196 /* sma->sem_pending = NULL; */
197 sma->sem_pending_last = &sma->sem_pending;
198 /* sma->undo = NULL; */
199 sma->sem_nsems = nsems;
200 sma->sem_ctime = get_seconds();
201 sem_unlock(sma);
202
203 return sem_buildid(id, sma->sem_perm.seq);
204 }
205
206 asmlinkage long sys_semget (key_t key, int nsems, int semflg)
207 {
208 int id, err = -EINVAL;
209 struct sem_array *sma;
210
211 if (nsems < 0 || nsems > sc_semmsl)
212 return -EINVAL;
213 down(&sem_ids.sem);
214
215 if (key == IPC_PRIVATE) {
216 err = newary(key, nsems, semflg);
217 } else if ((id = ipc_findkey(&sem_ids, key)) == -1) { /* key not used */
218 if (!(semflg & IPC_CREAT))
219 err = -ENOENT;
220 else
221 err = newary(key, nsems, semflg);
222 } else if (semflg & IPC_CREAT && semflg & IPC_EXCL) {
223 err = -EEXIST;
224 } else {
225 sma = sem_lock(id);
226 if(sma==NULL)
227 BUG();
228 if (nsems > sma->sem_nsems)
229 err = -EINVAL;
230 else if (ipcperms(&sma->sem_perm, semflg))
231 err = -EACCES;
232 else {
233 int semid = sem_buildid(id, sma->sem_perm.seq);
234 err = security_sem_associate(sma, semflg);
235 if (!err)
236 err = semid;
237 }
238 sem_unlock(sma);
239 }
240
241 up(&sem_ids.sem);
242 return err;
243 }
244
245 /* Manage the doubly linked list sma->sem_pending as a FIFO:
246 * insert new queue elements at the tail sma->sem_pending_last.
247 */
248 static inline void append_to_queue (struct sem_array * sma,
249 struct sem_queue * q)
250 {
251 *(q->prev = sma->sem_pending_last) = q;
252 *(sma->sem_pending_last = &q->next) = NULL;
253 }
254
255 static inline void prepend_to_queue (struct sem_array * sma,
256 struct sem_queue * q)
257 {
258 q->next = sma->sem_pending;
259 *(q->prev = &sma->sem_pending) = q;
260 if (q->next)
261 q->next->prev = &q->next;
262 else /* sma->sem_pending_last == &sma->sem_pending */
263 sma->sem_pending_last = &q->next;
264 }
265
266 static inline void remove_from_queue (struct sem_array * sma,
267 struct sem_queue * q)
268 {
269 *(q->prev) = q->next;
270 if (q->next)
271 q->next->prev = q->prev;
272 else /* sma->sem_pending_last == &q->next */
273 sma->sem_pending_last = q->prev;
274 q->prev = NULL; /* mark as removed */
275 }
276
277 /*
278 * Determine whether a sequence of semaphore operations would succeed
279 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
280 */
281
282 static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
283 int nsops, struct sem_undo *un, int pid)
284 {
285 int result, sem_op;
286 struct sembuf *sop;
287 struct sem * curr;
288
289 for (sop = sops; sop < sops + nsops; sop++) {
290 curr = sma->sem_base + sop->sem_num;
291 sem_op = sop->sem_op;
292 result = curr->semval;
293
294 if (!sem_op && result)
295 goto would_block;
296
297 result += sem_op;
298 if (result < 0)
299 goto would_block;
300 if (result > SEMVMX)
301 goto out_of_range;
302 if (sop->sem_flg & SEM_UNDO) {
303 int undo = un->semadj[sop->sem_num] - sem_op;
304 /*
305 * Exceeding the undo range is an error.
306 */
307 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
308 goto out_of_range;
309 }
310 curr->semval = result;
311 }
312
313 sop--;
314 while (sop >= sops) {
315 sma->sem_base[sop->sem_num].sempid = pid;
316 if (sop->sem_flg & SEM_UNDO)
317 un->semadj[sop->sem_num] -= sop->sem_op;
318 sop--;
319 }
320
321 sma->sem_otime = get_seconds();
322 return 0;
323
324 out_of_range:
325 result = -ERANGE;
326 goto undo;
327
328 would_block:
329 if (sop->sem_flg & IPC_NOWAIT)
330 result = -EAGAIN;
331 else
332 result = 1;
333
334 undo:
335 sop--;
336 while (sop >= sops) {
337 sma->sem_base[sop->sem_num].semval -= sop->sem_op;
338 sop--;
339 }
340
341 return result;
342 }
343
344 /* Go through the pending queue for the indicated semaphore
345 * looking for tasks that can be completed.
346 */
347 static void update_queue (struct sem_array * sma)
348 {
349 int error;
350 struct sem_queue * q;
351
352 q = sma->sem_pending;
353 while(q) {
354 error = try_atomic_semop(sma, q->sops, q->nsops,
355 q->undo, q->pid);
356
357 /* Does q->sleeper still need to sleep? */
358 if (error <= 0) {
359 struct sem_queue *n;
360 remove_from_queue(sma,q);
361 q->status = IN_WAKEUP;
362 /*
363 * Continue scanning. The next operation
364 * that must be checked depends on the type of the
365 * completed operation:
366 * - if the operation modified the array, then
367 * restart from the head of the queue and
368 * check for threads that might be waiting
369 * for semaphore values to become 0.
370 * - if the operation didn't modify the array,
371 * then just continue.
372 */
373 if (q->alter)
374 n = sma->sem_pending;
375 else
376 n = q->next;
377 wake_up_process(q->sleeper);
378 /* hands-off: q will disappear immediately after
379 * writing q->status.
380 */
381 q->status = error;
382 q = n;
383 } else {
384 q = q->next;
385 }
386 }
387 }
388
389 /* The following counts are associated to each semaphore:
390 * semncnt number of tasks waiting on semval being nonzero
391 * semzcnt number of tasks waiting on semval being zero
392 * This model assumes that a task waits on exactly one semaphore.
393 * Since semaphore operations are to be performed atomically, tasks actually
394 * wait on a whole sequence of semaphores simultaneously.
395 * The counts we return here are a rough approximation, but still
396 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
397 */
398 static int count_semncnt (struct sem_array * sma, ushort semnum)
399 {
400 int semncnt;
401 struct sem_queue * q;
402
403 semncnt = 0;
404 for (q = sma->sem_pending; q; q = q->next) {
405 struct sembuf * sops = q->sops;
406 int nsops = q->nsops;
407 int i;
408 for (i = 0; i < nsops; i++)
409 if (sops[i].sem_num == semnum
410 && (sops[i].sem_op < 0)
411 && !(sops[i].sem_flg & IPC_NOWAIT))
412 semncnt++;
413 }
414 return semncnt;
415 }
416 static int count_semzcnt (struct sem_array * sma, ushort semnum)
417 {
418 int semzcnt;
419 struct sem_queue * q;
420
421 semzcnt = 0;
422 for (q = sma->sem_pending; q; q = q->next) {
423 struct sembuf * sops = q->sops;
424 int nsops = q->nsops;
425 int i;
426 for (i = 0; i < nsops; i++)
427 if (sops[i].sem_num == semnum
428 && (sops[i].sem_op == 0)
429 && !(sops[i].sem_flg & IPC_NOWAIT))
430 semzcnt++;
431 }
432 return semzcnt;
433 }
434
435 /* Free a semaphore set. freeary() is called with sem_ids.sem down and
436 * the spinlock for this semaphore set hold. sem_ids.sem remains locked
437 * on exit.
438 */
439 static void freeary (struct sem_array *sma, int id)
440 {
441 struct sem_undo *un;
442 struct sem_queue *q;
443 int size;
444
445 /* Invalidate the existing undo structures for this semaphore set.
446 * (They will be freed without any further action in exit_sem()
447 * or during the next semop.)
448 */
449 for (un = sma->undo; un; un = un->id_next)
450 un->semid = -1;
451
452 /* Wake up all pending processes and let them fail with EIDRM. */
453 q = sma->sem_pending;
454 while(q) {
455 struct sem_queue *n;
456 /* lazy remove_from_queue: we are killing the whole queue */
457 q->prev = NULL;
458 n = q->next;
459 q->status = IN_WAKEUP;
460 wake_up_process(q->sleeper); /* doesn't sleep */
461 q->status = -EIDRM; /* hands-off q */
462 q = n;
463 }
464
465 /* Remove the semaphore set from the ID array*/
466 sma = sem_rmid(id);
467 sem_unlock(sma);
468
469 used_sems -= sma->sem_nsems;
470 size = sizeof (*sma) + sma->sem_nsems * sizeof (struct sem);
471 security_sem_free(sma);
472 ipc_rcu_putref(sma);
473 }
474
475 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
476 {
477 switch(version) {
478 case IPC_64:
479 return copy_to_user(buf, in, sizeof(*in));
480 case IPC_OLD:
481 {
482 struct semid_ds out;
483
484 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
485
486 out.sem_otime = in->sem_otime;
487 out.sem_ctime = in->sem_ctime;
488 out.sem_nsems = in->sem_nsems;
489
490 return copy_to_user(buf, &out, sizeof(out));
491 }
492 default:
493 return -EINVAL;
494 }
495 }
496
497 static int semctl_nolock(int semid, int semnum, int cmd, int version, union semun arg)
498 {
499 int err = -EINVAL;
500 struct sem_array *sma;
501
502 switch(cmd) {
503 case IPC_INFO:
504 case SEM_INFO:
505 {
506 struct seminfo seminfo;
507 int max_id;
508
509 err = security_sem_semctl(NULL, cmd);
510 if (err)
511 return err;
512
513 memset(&seminfo,0,sizeof(seminfo));
514 seminfo.semmni = sc_semmni;
515 seminfo.semmns = sc_semmns;
516 seminfo.semmsl = sc_semmsl;
517 seminfo.semopm = sc_semopm;
518 seminfo.semvmx = SEMVMX;
519 seminfo.semmnu = SEMMNU;
520 seminfo.semmap = SEMMAP;
521 seminfo.semume = SEMUME;
522 down(&sem_ids.sem);
523 if (cmd == SEM_INFO) {
524 seminfo.semusz = sem_ids.in_use;
525 seminfo.semaem = used_sems;
526 } else {
527 seminfo.semusz = SEMUSZ;
528 seminfo.semaem = SEMAEM;
529 }
530 max_id = sem_ids.max_id;
531 up(&sem_ids.sem);
532 if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
533 return -EFAULT;
534 return (max_id < 0) ? 0: max_id;
535 }
536 case SEM_STAT:
537 {
538 struct semid64_ds tbuf;
539 int id;
540
541 if(semid >= sem_ids.entries->size)
542 return -EINVAL;
543
544 memset(&tbuf,0,sizeof(tbuf));
545
546 sma = sem_lock(semid);
547 if(sma == NULL)
548 return -EINVAL;
549
550 err = -EACCES;
551 if (ipcperms (&sma->sem_perm, S_IRUGO))
552 goto out_unlock;
553
554 err = security_sem_semctl(sma, cmd);
555 if (err)
556 goto out_unlock;
557
558 id = sem_buildid(semid, sma->sem_perm.seq);
559
560 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
561 tbuf.sem_otime = sma->sem_otime;
562 tbuf.sem_ctime = sma->sem_ctime;
563 tbuf.sem_nsems = sma->sem_nsems;
564 sem_unlock(sma);
565 if (copy_semid_to_user (arg.buf, &tbuf, version))
566 return -EFAULT;
567 return id;
568 }
569 default:
570 return -EINVAL;
571 }
572 return err;
573 out_unlock:
574 sem_unlock(sma);
575 return err;
576 }
577
578 static int semctl_main(int semid, int semnum, int cmd, int version, union semun arg)
579 {
580 struct sem_array *sma;
581 struct sem* curr;
582 int err;
583 ushort fast_sem_io[SEMMSL_FAST];
584 ushort* sem_io = fast_sem_io;
585 int nsems;
586
587 sma = sem_lock(semid);
588 if(sma==NULL)
589 return -EINVAL;
590
591 nsems = sma->sem_nsems;
592
593 err=-EIDRM;
594 if (sem_checkid(sma,semid))
595 goto out_unlock;
596
597 err = -EACCES;
598 if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
599 goto out_unlock;
600
601 err = security_sem_semctl(sma, cmd);
602 if (err)
603 goto out_unlock;
604
605 err = -EACCES;
606 switch (cmd) {
607 case GETALL:
608 {
609 ushort __user *array = arg.array;
610 int i;
611
612 if(nsems > SEMMSL_FAST) {
613 ipc_rcu_getref(sma);
614 sem_unlock(sma);
615
616 sem_io = ipc_alloc(sizeof(ushort)*nsems);
617 if(sem_io == NULL) {
618 ipc_lock_by_ptr(&sma->sem_perm);
619 ipc_rcu_putref(sma);
620 sem_unlock(sma);
621 return -ENOMEM;
622 }
623
624 ipc_lock_by_ptr(&sma->sem_perm);
625 ipc_rcu_putref(sma);
626 if (sma->sem_perm.deleted) {
627 sem_unlock(sma);
628 err = -EIDRM;
629 goto out_free;
630 }
631 }
632
633 for (i = 0; i < sma->sem_nsems; i++)
634 sem_io[i] = sma->sem_base[i].semval;
635 sem_unlock(sma);
636 err = 0;
637 if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
638 err = -EFAULT;
639 goto out_free;
640 }
641 case SETALL:
642 {
643 int i;
644 struct sem_undo *un;
645
646 ipc_rcu_getref(sma);
647 sem_unlock(sma);
648
649 if(nsems > SEMMSL_FAST) {
650 sem_io = ipc_alloc(sizeof(ushort)*nsems);
651 if(sem_io == NULL) {
652 ipc_lock_by_ptr(&sma->sem_perm);
653 ipc_rcu_putref(sma);
654 sem_unlock(sma);
655 return -ENOMEM;
656 }
657 }
658
659 if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
660 ipc_lock_by_ptr(&sma->sem_perm);
661 ipc_rcu_putref(sma);
662 sem_unlock(sma);
663 err = -EFAULT;
664 goto out_free;
665 }
666
667 for (i = 0; i < nsems; i++) {
668 if (sem_io[i] > SEMVMX) {
669 ipc_lock_by_ptr(&sma->sem_perm);
670 ipc_rcu_putref(sma);
671 sem_unlock(sma);
672 err = -ERANGE;
673 goto out_free;
674 }
675 }
676 ipc_lock_by_ptr(&sma->sem_perm);
677 ipc_rcu_putref(sma);
678 if (sma->sem_perm.deleted) {
679 sem_unlock(sma);
680 err = -EIDRM;
681 goto out_free;
682 }
683
684 for (i = 0; i < nsems; i++)
685 sma->sem_base[i].semval = sem_io[i];
686 for (un = sma->undo; un; un = un->id_next)
687 for (i = 0; i < nsems; i++)
688 un->semadj[i] = 0;
689 sma->sem_ctime = get_seconds();
690 /* maybe some queued-up processes were waiting for this */
691 update_queue(sma);
692 err = 0;
693 goto out_unlock;
694 }
695 case IPC_STAT:
696 {
697 struct semid64_ds tbuf;
698 memset(&tbuf,0,sizeof(tbuf));
699 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
700 tbuf.sem_otime = sma->sem_otime;
701 tbuf.sem_ctime = sma->sem_ctime;
702 tbuf.sem_nsems = sma->sem_nsems;
703 sem_unlock(sma);
704 if (copy_semid_to_user (arg.buf, &tbuf, version))
705 return -EFAULT;
706 return 0;
707 }
708 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
709 }
710 err = -EINVAL;
711 if(semnum < 0 || semnum >= nsems)
712 goto out_unlock;
713
714 curr = &sma->sem_base[semnum];
715
716 switch (cmd) {
717 case GETVAL:
718 err = curr->semval;
719 goto out_unlock;
720 case GETPID:
721 err = curr->sempid;
722 goto out_unlock;
723 case GETNCNT:
724 err = count_semncnt(sma,semnum);
725 goto out_unlock;
726 case GETZCNT:
727 err = count_semzcnt(sma,semnum);
728 goto out_unlock;
729 case SETVAL:
730 {
731 int val = arg.val;
732 struct sem_undo *un;
733 err = -ERANGE;
734 if (val > SEMVMX || val < 0)
735 goto out_unlock;
736
737 for (un = sma->undo; un; un = un->id_next)
738 un->semadj[semnum] = 0;
739 curr->semval = val;
740 curr->sempid = current->tgid;
741 sma->sem_ctime = get_seconds();
742 /* maybe some queued-up processes were waiting for this */
743 update_queue(sma);
744 err = 0;
745 goto out_unlock;
746 }
747 }
748 out_unlock:
749 sem_unlock(sma);
750 out_free:
751 if(sem_io != fast_sem_io)
752 ipc_free(sem_io, sizeof(ushort)*nsems);
753 return err;
754 }
755
756 struct sem_setbuf {
757 uid_t uid;
758 gid_t gid;
759 mode_t mode;
760 };
761
762 static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __user *buf, int version)
763 {
764 switch(version) {
765 case IPC_64:
766 {
767 struct semid64_ds tbuf;
768
769 if(copy_from_user(&tbuf, buf, sizeof(tbuf)))
770 return -EFAULT;
771
772 out->uid = tbuf.sem_perm.uid;
773 out->gid = tbuf.sem_perm.gid;
774 out->mode = tbuf.sem_perm.mode;
775
776 return 0;
777 }
778 case IPC_OLD:
779 {
780 struct semid_ds tbuf_old;
781
782 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
783 return -EFAULT;
784
785 out->uid = tbuf_old.sem_perm.uid;
786 out->gid = tbuf_old.sem_perm.gid;
787 out->mode = tbuf_old.sem_perm.mode;
788
789 return 0;
790 }
791 default:
792 return -EINVAL;
793 }
794 }
795
796 static int semctl_down(int semid, int semnum, int cmd, int version, union semun arg)
797 {
798 struct sem_array *sma;
799 int err;
800 struct sem_setbuf setbuf;
801 struct kern_ipc_perm *ipcp;
802
803 if(cmd == IPC_SET) {
804 if(copy_semid_from_user (&setbuf, arg.buf, version))
805 return -EFAULT;
806 }
807 sma = sem_lock(semid);
808 if(sma==NULL)
809 return -EINVAL;
810
811 if (sem_checkid(sma,semid)) {
812 err=-EIDRM;
813 goto out_unlock;
814 }
815 ipcp = &sma->sem_perm;
816
817 if (current->euid != ipcp->cuid &&
818 current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) {
819 err=-EPERM;
820 goto out_unlock;
821 }
822
823 err = security_sem_semctl(sma, cmd);
824 if (err)
825 goto out_unlock;
826
827 switch(cmd){
828 case IPC_RMID:
829 freeary(sma, semid);
830 err = 0;
831 break;
832 case IPC_SET:
833 ipcp->uid = setbuf.uid;
834 ipcp->gid = setbuf.gid;
835 ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
836 | (setbuf.mode & S_IRWXUGO);
837 sma->sem_ctime = get_seconds();
838 sem_unlock(sma);
839 err = 0;
840 break;
841 default:
842 sem_unlock(sma);
843 err = -EINVAL;
844 break;
845 }
846 return err;
847
848 out_unlock:
849 sem_unlock(sma);
850 return err;
851 }
852
853 asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
854 {
855 int err = -EINVAL;
856 int version;
857
858 if (semid < 0)
859 return -EINVAL;
860
861 version = ipc_parse_version(&cmd);
862
863 switch(cmd) {
864 case IPC_INFO:
865 case SEM_INFO:
866 case SEM_STAT:
867 err = semctl_nolock(semid,semnum,cmd,version,arg);
868 return err;
869 case GETALL:
870 case GETVAL:
871 case GETPID:
872 case GETNCNT:
873 case GETZCNT:
874 case IPC_STAT:
875 case SETVAL:
876 case SETALL:
877 err = semctl_main(semid,semnum,cmd,version,arg);
878 return err;
879 case IPC_RMID:
880 case IPC_SET:
881 down(&sem_ids.sem);
882 err = semctl_down(semid,semnum,cmd,version,arg);
883 up(&sem_ids.sem);
884 return err;
885 default:
886 return -EINVAL;
887 }
888 }
889
890 static inline void lock_semundo(void)
891 {
892 struct sem_undo_list *undo_list;
893
894 undo_list = current->sysvsem.undo_list;
895 if ((undo_list != NULL) && (atomic_read(&undo_list->refcnt) != 1))
896 spin_lock(&undo_list->lock);
897 }
898
899 /* This code has an interaction with copy_semundo().
900 * Consider; two tasks are sharing the undo_list. task1
901 * acquires the undo_list lock in lock_semundo(). If task2 now
902 * exits before task1 releases the lock (by calling
903 * unlock_semundo()), then task1 will never call spin_unlock().
904 * This leave the sem_undo_list in a locked state. If task1 now creats task3
905 * and once again shares the sem_undo_list, the sem_undo_list will still be
906 * locked, and future SEM_UNDO operations will deadlock. This case is
907 * dealt with in copy_semundo() by having it reinitialize the spin lock when
908 * the refcnt goes from 1 to 2.
909 */
910 static inline void unlock_semundo(void)
911 {
912 struct sem_undo_list *undo_list;
913
914 undo_list = current->sysvsem.undo_list;
915 if ((undo_list != NULL) && (atomic_read(&undo_list->refcnt) != 1))
916 spin_unlock(&undo_list->lock);
917 }
918
919
920 /* If the task doesn't already have a undo_list, then allocate one
921 * here. We guarantee there is only one thread using this undo list,
922 * and current is THE ONE
923 *
924 * If this allocation and assignment succeeds, but later
925 * portions of this code fail, there is no need to free the sem_undo_list.
926 * Just let it stay associated with the task, and it'll be freed later
927 * at exit time.
928 *
929 * This can block, so callers must hold no locks.
930 */
931 static inline int get_undo_list(struct sem_undo_list **undo_listp)
932 {
933 struct sem_undo_list *undo_list;
934 int size;
935
936 undo_list = current->sysvsem.undo_list;
937 if (!undo_list) {
938 size = sizeof(struct sem_undo_list);
939 undo_list = (struct sem_undo_list *) kmalloc(size, GFP_KERNEL);
940 if (undo_list == NULL)
941 return -ENOMEM;
942 memset(undo_list, 0, size);
943 /* don't initialize unodhd->lock here. It's done
944 * in copy_semundo() instead.
945 */
946 atomic_set(&undo_list->refcnt, 1);
947 current->sysvsem.undo_list = undo_list;
948 }
949 *undo_listp = undo_list;
950 return 0;
951 }
952
953 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
954 {
955 struct sem_undo **last, *un;
956
957 last = &ulp->proc_list;
958 un = *last;
959 while(un != NULL) {
960 if(un->semid==semid)
961 break;
962 if(un->semid==-1) {
963 *last=un->proc_next;
964 kfree(un);
965 } else {
966 last=&un->proc_next;
967 }
968 un=*last;
969 }
970 return un;
971 }
972
973 static struct sem_undo *find_undo(int semid)
974 {
975 struct sem_array *sma;
976 struct sem_undo_list *ulp;
977 struct sem_undo *un, *new;
978 int nsems;
979 int error;
980
981 error = get_undo_list(&ulp);
982 if (error)
983 return ERR_PTR(error);
984
985 lock_semundo();
986 un = lookup_undo(ulp, semid);
987 unlock_semundo();
988 if (likely(un!=NULL))
989 goto out;
990
991 /* no undo structure around - allocate one. */
992 sma = sem_lock(semid);
993 un = ERR_PTR(-EINVAL);
994 if(sma==NULL)
995 goto out;
996 un = ERR_PTR(-EIDRM);
997 if (sem_checkid(sma,semid)) {
998 sem_unlock(sma);
999 goto out;
1000 }
1001 nsems = sma->sem_nsems;
1002 ipc_rcu_getref(sma);
1003 sem_unlock(sma);
1004
1005 new = (struct sem_undo *) kmalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1006 if (!new) {
1007 ipc_lock_by_ptr(&sma->sem_perm);
1008 ipc_rcu_putref(sma);
1009 sem_unlock(sma);
1010 return ERR_PTR(-ENOMEM);
1011 }
1012 memset(new, 0, sizeof(struct sem_undo) + sizeof(short)*nsems);
1013 new->semadj = (short *) &new[1];
1014 new->semid = semid;
1015
1016 lock_semundo();
1017 un = lookup_undo(ulp, semid);
1018 if (un) {
1019 unlock_semundo();
1020 kfree(new);
1021 ipc_lock_by_ptr(&sma->sem_perm);
1022 ipc_rcu_putref(sma);
1023 sem_unlock(sma);
1024 goto out;
1025 }
1026 ipc_lock_by_ptr(&sma->sem_perm);
1027 ipc_rcu_putref(sma);
1028 if (sma->sem_perm.deleted) {
1029 sem_unlock(sma);
1030 unlock_semundo();
1031 kfree(new);
1032 un = ERR_PTR(-EIDRM);
1033 goto out;
1034 }
1035 new->proc_next = ulp->proc_list;
1036 ulp->proc_list = new;
1037 new->id_next = sma->undo;
1038 sma->undo = new;
1039 sem_unlock(sma);
1040 un = new;
1041 unlock_semundo();
1042 out:
1043 return un;
1044 }
1045
1046 asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
1047 unsigned nsops, const struct timespec __user *timeout)
1048 {
1049 int error = -EINVAL;
1050 struct sem_array *sma;
1051 struct sembuf fast_sops[SEMOPM_FAST];
1052 struct sembuf* sops = fast_sops, *sop;
1053 struct sem_undo *un;
1054 int undos = 0, decrease = 0, alter = 0, max;
1055 struct sem_queue queue;
1056 unsigned long jiffies_left = 0;
1057
1058 if (nsops < 1 || semid < 0)
1059 return -EINVAL;
1060 if (nsops > sc_semopm)
1061 return -E2BIG;
1062 if(nsops > SEMOPM_FAST) {
1063 sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1064 if(sops==NULL)
1065 return -ENOMEM;
1066 }
1067 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1068 error=-EFAULT;
1069 goto out_free;
1070 }
1071 if (timeout) {
1072 struct timespec _timeout;
1073 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1074 error = -EFAULT;
1075 goto out_free;
1076 }
1077 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1078 _timeout.tv_nsec >= 1000000000L) {
1079 error = -EINVAL;
1080 goto out_free;
1081 }
1082 jiffies_left = timespec_to_jiffies(&_timeout);
1083 }
1084 max = 0;
1085 for (sop = sops; sop < sops + nsops; sop++) {
1086 if (sop->sem_num >= max)
1087 max = sop->sem_num;
1088 if (sop->sem_flg & SEM_UNDO)
1089 undos++;
1090 if (sop->sem_op < 0)
1091 decrease = 1;
1092 if (sop->sem_op > 0)
1093 alter = 1;
1094 }
1095 alter |= decrease;
1096
1097 retry_undos:
1098 if (undos) {
1099 un = find_undo(semid);
1100 if (IS_ERR(un)) {
1101 error = PTR_ERR(un);
1102 goto out_free;
1103 }
1104 } else
1105 un = NULL;
1106
1107 sma = sem_lock(semid);
1108 error=-EINVAL;
1109 if(sma==NULL)
1110 goto out_free;
1111 error = -EIDRM;
1112 if (sem_checkid(sma,semid))
1113 goto out_unlock_free;
1114 /*
1115 * semid identifies are not unique - find_undo may have
1116 * allocated an undo structure, it was invalidated by an RMID
1117 * and now a new array with received the same id. Check and retry.
1118 */
1119 if (un && un->semid == -1) {
1120 sem_unlock(sma);
1121 goto retry_undos;
1122 }
1123 error = -EFBIG;
1124 if (max >= sma->sem_nsems)
1125 goto out_unlock_free;
1126
1127 error = -EACCES;
1128 if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1129 goto out_unlock_free;
1130
1131 error = security_sem_semop(sma, sops, nsops, alter);
1132 if (error)
1133 goto out_unlock_free;
1134
1135 error = try_atomic_semop (sma, sops, nsops, un, current->tgid);
1136 if (error <= 0) {
1137 if (alter && error == 0)
1138 update_queue (sma);
1139 goto out_unlock_free;
1140 }
1141
1142 /* We need to sleep on this operation, so we put the current
1143 * task into the pending queue and go to sleep.
1144 */
1145
1146 queue.sma = sma;
1147 queue.sops = sops;
1148 queue.nsops = nsops;
1149 queue.undo = un;
1150 queue.pid = current->tgid;
1151 queue.id = semid;
1152 queue.alter = alter;
1153 if (alter)
1154 append_to_queue(sma ,&queue);
1155 else
1156 prepend_to_queue(sma ,&queue);
1157
1158 queue.status = -EINTR;
1159 queue.sleeper = current;
1160 current->state = TASK_INTERRUPTIBLE;
1161 sem_unlock(sma);
1162
1163 if (timeout)
1164 jiffies_left = schedule_timeout(jiffies_left);
1165 else
1166 schedule();
1167
1168 error = queue.status;
1169 while(unlikely(error == IN_WAKEUP)) {
1170 cpu_relax();
1171 error = queue.status;
1172 }
1173
1174 if (error != -EINTR) {
1175 /* fast path: update_queue already obtained all requested
1176 * resources */
1177 goto out_free;
1178 }
1179
1180 sma = sem_lock(semid);
1181 if(sma==NULL) {
1182 if(queue.prev != NULL)
1183 BUG();
1184 error = -EIDRM;
1185 goto out_free;
1186 }
1187
1188 /*
1189 * If queue.status != -EINTR we are woken up by another process
1190 */
1191 error = queue.status;
1192 if (error != -EINTR) {
1193 goto out_unlock_free;
1194 }
1195
1196 /*
1197 * If an interrupt occurred we have to clean up the queue
1198 */
1199 if (timeout && jiffies_left == 0)
1200 error = -EAGAIN;
1201 remove_from_queue(sma,&queue);
1202 goto out_unlock_free;
1203
1204 out_unlock_free:
1205 sem_unlock(sma);
1206 out_free:
1207 if(sops != fast_sops)
1208 kfree(sops);
1209 return error;
1210 }
1211
1212 asmlinkage long sys_semop (int semid, struct sembuf __user *tsops, unsigned nsops)
1213 {
1214 return sys_semtimedop(semid, tsops, nsops, NULL);
1215 }
1216
1217 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1218 * parent and child tasks.
1219 *
1220 * See the notes above unlock_semundo() regarding the spin_lock_init()
1221 * in this code. Initialize the undo_list->lock here instead of get_undo_list()
1222 * because of the reasoning in the comment above unlock_semundo.
1223 */
1224
1225 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1226 {
1227 struct sem_undo_list *undo_list;
1228 int error;
1229
1230 if (clone_flags & CLONE_SYSVSEM) {
1231 error = get_undo_list(&undo_list);
1232 if (error)
1233 return error;
1234 if (atomic_read(&undo_list->refcnt) == 1)
1235 spin_lock_init(&undo_list->lock);
1236 atomic_inc(&undo_list->refcnt);
1237 tsk->sysvsem.undo_list = undo_list;
1238 } else
1239 tsk->sysvsem.undo_list = NULL;
1240
1241 return 0;
1242 }
1243
1244 /*
1245 * add semadj values to semaphores, free undo structures.
1246 * undo structures are not freed when semaphore arrays are destroyed
1247 * so some of them may be out of date.
1248 * IMPLEMENTATION NOTE: There is some confusion over whether the
1249 * set of adjustments that needs to be done should be done in an atomic
1250 * manner or not. That is, if we are attempting to decrement the semval
1251 * should we queue up and wait until we can do so legally?
1252 * The original implementation attempted to do this (queue and wait).
1253 * The current implementation does not do so. The POSIX standard
1254 * and SVID should be consulted to determine what behavior is mandated.
1255 */
1256 void exit_sem(struct task_struct *tsk)
1257 {
1258 struct sem_undo_list *undo_list;
1259 struct sem_undo *u, **up;
1260
1261 undo_list = tsk->sysvsem.undo_list;
1262 if (!undo_list)
1263 return;
1264
1265 if (!atomic_dec_and_test(&undo_list->refcnt))
1266 return;
1267
1268 /* There's no need to hold the semundo list lock, as current
1269 * is the last task exiting for this undo list.
1270 */
1271 for (up = &undo_list->proc_list; (u = *up); *up = u->proc_next, kfree(u)) {
1272 struct sem_array *sma;
1273 int nsems, i;
1274 struct sem_undo *un, **unp;
1275 int semid;
1276
1277 semid = u->semid;
1278
1279 if(semid == -1)
1280 continue;
1281 sma = sem_lock(semid);
1282 if (sma == NULL)
1283 continue;
1284
1285 if (u->semid == -1)
1286 goto next_entry;
1287
1288 BUG_ON(sem_checkid(sma,u->semid));
1289
1290 /* remove u from the sma->undo list */
1291 for (unp = &sma->undo; (un = *unp); unp = &un->id_next) {
1292 if (u == un)
1293 goto found;
1294 }
1295 printk ("exit_sem undo list error id=%d\n", u->semid);
1296 goto next_entry;
1297 found:
1298 *unp = un->id_next;
1299 /* perform adjustments registered in u */
1300 nsems = sma->sem_nsems;
1301 for (i = 0; i < nsems; i++) {
1302 struct sem * sem = &sma->sem_base[i];
1303 if (u->semadj[i]) {
1304 sem->semval += u->semadj[i];
1305 /*
1306 * Range checks of the new semaphore value,
1307 * not defined by sus:
1308 * - Some unices ignore the undo entirely
1309 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1310 * - some cap the value (e.g. FreeBSD caps
1311 * at 0, but doesn't enforce SEMVMX)
1312 *
1313 * Linux caps the semaphore value, both at 0
1314 * and at SEMVMX.
1315 *
1316 * Manfred <manfred@colorfullife.com>
1317 */
1318 if (sem->semval < 0)
1319 sem->semval = 0;
1320 if (sem->semval > SEMVMX)
1321 sem->semval = SEMVMX;
1322 sem->sempid = current->tgid;
1323 }
1324 }
1325 sma->sem_otime = get_seconds();
1326 /* maybe some queued-up processes were waiting for this */
1327 update_queue(sma);
1328 next_entry:
1329 sem_unlock(sma);
1330 }
1331 kfree(undo_list);
1332 }
1333
1334 #ifdef CONFIG_PROC_FS
1335 static int sysvipc_sem_read_proc(char *buffer, char **start, off_t offset, int length, int *eof, void *data)
1336 {
1337 off_t pos = 0;
1338 off_t begin = 0;
1339 int i, len = 0;
1340
1341 len += sprintf(buffer, " key semid perms nsems uid gid cuid cgid otime ctime\n");
1342 down(&sem_ids.sem);
1343
1344 for(i = 0; i <= sem_ids.max_id; i++) {
1345 struct sem_array *sma;
1346 sma = sem_lock(i);
1347 if(sma) {
1348 len += sprintf(buffer + len, "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
1349 sma->sem_perm.key,
1350 sem_buildid(i,sma->sem_perm.seq),
1351 sma->sem_perm.mode,
1352 sma->sem_nsems,
1353 sma->sem_perm.uid,
1354 sma->sem_perm.gid,
1355 sma->sem_perm.cuid,
1356 sma->sem_perm.cgid,
1357 sma->sem_otime,
1358 sma->sem_ctime);
1359 sem_unlock(sma);
1360
1361 pos += len;
1362 if(pos < offset) {
1363 len = 0;
1364 begin = pos;
1365 }
1366 if(pos > offset + length)
1367 goto done;
1368 }
1369 }
1370 *eof = 1;
1371 done:
1372 up(&sem_ids.sem);
1373 *start = buffer + (offset - begin);
1374 len -= (offset - begin);
1375 if(len > length)
1376 len = length;
1377 if(len < 0)
1378 len = 0;
1379 return len;
1380 }
1381 #endif
1382
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