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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Christian Kujau624dffc2006-01-15 02:43:54 +010059 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
Linus Torvalds1da177e2005-04-16 15:20:36 -070060 * 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>
Steve Grubb073115d2006-04-02 17:07:33 -040064 *
65 * support for audit of ipc object properties and permission changes
66 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
Kirill Korotaeve3893532006-10-02 02:18:22 -070067 *
68 * namespaces support
69 * OpenVZ, SWsoft Inc.
70 * Pavel Emelianov <xemul@openvz.org>
Linus Torvalds1da177e2005-04-16 15:20:36 -070071 */
72
Linus Torvalds1da177e2005-04-16 15:20:36 -070073#include <linux/slab.h>
74#include <linux/spinlock.h>
75#include <linux/init.h>
76#include <linux/proc_fs.h>
77#include <linux/time.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070078#include <linux/security.h>
79#include <linux/syscalls.h>
80#include <linux/audit.h>
Randy.Dunlapc59ede72006-01-11 12:17:46 -080081#include <linux/capability.h>
Mike Waychison19b49462005-09-06 15:17:10 -070082#include <linux/seq_file.h>
Nadia Derbey3e148c72007-10-18 23:40:54 -070083#include <linux/rwsem.h>
Kirill Korotaeve3893532006-10-02 02:18:22 -070084#include <linux/nsproxy.h>
Pavel Emelyanovae5e1b22008-02-08 04:18:22 -080085#include <linux/ipc_namespace.h>
Ingo Molnar5f921ae2006-03-26 01:37:17 -080086
Linus Torvalds1da177e2005-04-16 15:20:36 -070087#include <asm/uaccess.h>
88#include "util.h"
89
Pierre Peiffered2ddbf2008-02-08 04:18:57 -080090#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
Linus Torvalds1da177e2005-04-16 15:20:36 -070091
Kirill Korotaeve3893532006-10-02 02:18:22 -070092#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
Nadia Derbey1b531f22007-10-18 23:40:55 -070093#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
Linus Torvalds1da177e2005-04-16 15:20:36 -070094
Nadia Derbey7748dbf2007-10-18 23:40:49 -070095static int newary(struct ipc_namespace *, struct ipc_params *);
Pierre Peiffer01b8b072008-02-08 04:18:57 -080096static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
Linus Torvalds1da177e2005-04-16 15:20:36 -070097#ifdef CONFIG_PROC_FS
Mike Waychison19b49462005-09-06 15:17:10 -070098static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
Linus Torvalds1da177e2005-04-16 15:20:36 -070099#endif
100
101#define SEMMSL_FAST 256 /* 512 bytes on stack */
102#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
103
104/*
105 * linked list protection:
106 * sem_undo.id_next,
107 * sem_array.sem_pending{,last},
108 * sem_array.sem_undo: sem_lock() for read/write
109 * sem_undo.proc_next: only "current" is allowed to read/write that field.
110 *
111 */
112
Kirill Korotaeve3893532006-10-02 02:18:22 -0700113#define sc_semmsl sem_ctls[0]
114#define sc_semmns sem_ctls[1]
115#define sc_semopm sem_ctls[2]
116#define sc_semmni sem_ctls[3]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700117
Pierre Peiffered2ddbf2008-02-08 04:18:57 -0800118void sem_init_ns(struct ipc_namespace *ns)
Kirill Korotaeve3893532006-10-02 02:18:22 -0700119{
Kirill Korotaeve3893532006-10-02 02:18:22 -0700120 ns->sc_semmsl = SEMMSL;
121 ns->sc_semmns = SEMMNS;
122 ns->sc_semopm = SEMOPM;
123 ns->sc_semmni = SEMMNI;
124 ns->used_sems = 0;
Pierre Peiffered2ddbf2008-02-08 04:18:57 -0800125 ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
Kirill Korotaeve3893532006-10-02 02:18:22 -0700126}
127
Pavel Emelyanovae5e1b22008-02-08 04:18:22 -0800128#ifdef CONFIG_IPC_NS
Kirill Korotaeve3893532006-10-02 02:18:22 -0700129void sem_exit_ns(struct ipc_namespace *ns)
130{
Pierre Peiffer01b8b072008-02-08 04:18:57 -0800131 free_ipcs(ns, &sem_ids(ns), freeary);
Kirill Korotaeve3893532006-10-02 02:18:22 -0700132}
Pavel Emelyanovae5e1b22008-02-08 04:18:22 -0800133#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700134
135void __init sem_init (void)
136{
Pierre Peiffered2ddbf2008-02-08 04:18:57 -0800137 sem_init_ns(&init_ipc_ns);
Mike Waychison19b49462005-09-06 15:17:10 -0700138 ipc_init_proc_interface("sysvipc/sem",
139 " key semid perms nsems uid gid cuid cgid otime ctime\n",
Kirill Korotaeve3893532006-10-02 02:18:22 -0700140 IPC_SEM_IDS, sysvipc_sem_proc_show);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700141}
142
Nadia Derbey3e148c72007-10-18 23:40:54 -0700143/*
Nadia Derbey3e148c72007-10-18 23:40:54 -0700144 * sem_lock_(check_) routines are called in the paths where the rw_mutex
145 * is not held.
146 */
Nadia Derbey023a5352007-10-18 23:40:51 -0700147static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
148{
Nadia Derbey03f02c72007-10-18 23:40:51 -0700149 struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
150
Pierre Peifferb1ed88b2008-02-06 01:36:23 -0800151 if (IS_ERR(ipcp))
152 return (struct sem_array *)ipcp;
153
Nadia Derbey03f02c72007-10-18 23:40:51 -0700154 return container_of(ipcp, struct sem_array, sem_perm);
Nadia Derbey023a5352007-10-18 23:40:51 -0700155}
156
157static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
158 int id)
159{
Nadia Derbey03f02c72007-10-18 23:40:51 -0700160 struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
161
Pierre Peifferb1ed88b2008-02-06 01:36:23 -0800162 if (IS_ERR(ipcp))
163 return (struct sem_array *)ipcp;
164
Nadia Derbey03f02c72007-10-18 23:40:51 -0700165 return container_of(ipcp, struct sem_array, sem_perm);
Nadia Derbey023a5352007-10-18 23:40:51 -0700166}
167
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700168static inline void sem_lock_and_putref(struct sem_array *sma)
169{
170 ipc_lock_by_ptr(&sma->sem_perm);
171 ipc_rcu_putref(sma);
172}
173
174static inline void sem_getref_and_unlock(struct sem_array *sma)
175{
176 ipc_rcu_getref(sma);
177 ipc_unlock(&(sma)->sem_perm);
178}
179
180static inline void sem_putref(struct sem_array *sma)
181{
182 ipc_lock_by_ptr(&sma->sem_perm);
183 ipc_rcu_putref(sma);
184 ipc_unlock(&(sma)->sem_perm);
185}
186
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700187static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
188{
189 ipc_rmid(&sem_ids(ns), &s->sem_perm);
190}
191
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192/*
193 * Lockless wakeup algorithm:
194 * Without the check/retry algorithm a lockless wakeup is possible:
195 * - queue.status is initialized to -EINTR before blocking.
196 * - wakeup is performed by
197 * * unlinking the queue entry from sma->sem_pending
198 * * setting queue.status to IN_WAKEUP
199 * This is the notification for the blocked thread that a
200 * result value is imminent.
201 * * call wake_up_process
202 * * set queue.status to the final value.
203 * - the previously blocked thread checks queue.status:
204 * * if it's IN_WAKEUP, then it must wait until the value changes
205 * * if it's not -EINTR, then the operation was completed by
206 * update_queue. semtimedop can return queue.status without
Ingo Molnar5f921ae2006-03-26 01:37:17 -0800207 * performing any operation on the sem array.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208 * * otherwise it must acquire the spinlock and check what's up.
209 *
210 * The two-stage algorithm is necessary to protect against the following
211 * races:
212 * - if queue.status is set after wake_up_process, then the woken up idle
213 * thread could race forward and try (and fail) to acquire sma->lock
214 * before update_queue had a chance to set queue.status
215 * - if queue.status is written before wake_up_process and if the
216 * blocked process is woken up by a signal between writing
217 * queue.status and the wake_up_process, then the woken up
218 * process could return from semtimedop and die by calling
219 * sys_exit before wake_up_process is called. Then wake_up_process
220 * will oops, because the task structure is already invalid.
221 * (yes, this happened on s390 with sysv msg).
222 *
223 */
224#define IN_WAKEUP 1
225
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700226/**
227 * newary - Create a new semaphore set
228 * @ns: namespace
229 * @params: ptr to the structure that contains key, semflg and nsems
230 *
Nadia Derbey3e148c72007-10-18 23:40:54 -0700231 * Called with sem_ids.rw_mutex held (as a writer)
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700232 */
233
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700234static int newary(struct ipc_namespace *ns, struct ipc_params *params)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235{
236 int id;
237 int retval;
238 struct sem_array *sma;
239 int size;
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700240 key_t key = params->key;
241 int nsems = params->u.nsems;
242 int semflg = params->flg;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700243
244 if (!nsems)
245 return -EINVAL;
Kirill Korotaeve3893532006-10-02 02:18:22 -0700246 if (ns->used_sems + nsems > ns->sc_semmns)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247 return -ENOSPC;
248
249 size = sizeof (*sma) + nsems * sizeof (struct sem);
250 sma = ipc_rcu_alloc(size);
251 if (!sma) {
252 return -ENOMEM;
253 }
254 memset (sma, 0, size);
255
256 sma->sem_perm.mode = (semflg & S_IRWXUGO);
257 sma->sem_perm.key = key;
258
259 sma->sem_perm.security = NULL;
260 retval = security_sem_alloc(sma);
261 if (retval) {
262 ipc_rcu_putref(sma);
263 return retval;
264 }
265
Kirill Korotaeve3893532006-10-02 02:18:22 -0700266 id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
Pierre Peiffer283bb7f2007-10-18 23:40:57 -0700267 if (id < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268 security_sem_free(sma);
269 ipc_rcu_putref(sma);
Pierre Peiffer283bb7f2007-10-18 23:40:57 -0700270 return id;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271 }
Kirill Korotaeve3893532006-10-02 02:18:22 -0700272 ns->used_sems += nsems;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700273
274 sma->sem_base = (struct sem *) &sma[1];
Manfred Spraula1193f82008-07-25 01:48:06 -0700275 INIT_LIST_HEAD(&sma->sem_pending);
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700276 INIT_LIST_HEAD(&sma->list_id);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277 sma->sem_nsems = nsems;
278 sma->sem_ctime = get_seconds();
279 sem_unlock(sma);
280
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700281 return sma->sem_perm.id;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282}
283
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700284
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700285/*
Nadia Derbey3e148c72007-10-18 23:40:54 -0700286 * Called with sem_ids.rw_mutex and ipcp locked.
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700287 */
Nadia Derbey03f02c72007-10-18 23:40:51 -0700288static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289{
Nadia Derbey03f02c72007-10-18 23:40:51 -0700290 struct sem_array *sma;
291
292 sma = container_of(ipcp, struct sem_array, sem_perm);
293 return security_sem_associate(sma, semflg);
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700294}
295
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700296/*
Nadia Derbey3e148c72007-10-18 23:40:54 -0700297 * Called with sem_ids.rw_mutex and ipcp locked.
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700298 */
Nadia Derbey03f02c72007-10-18 23:40:51 -0700299static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
300 struct ipc_params *params)
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700301{
Nadia Derbey03f02c72007-10-18 23:40:51 -0700302 struct sem_array *sma;
303
304 sma = container_of(ipcp, struct sem_array, sem_perm);
305 if (params->u.nsems > sma->sem_nsems)
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700306 return -EINVAL;
307
308 return 0;
309}
310
311asmlinkage long sys_semget(key_t key, int nsems, int semflg)
312{
Kirill Korotaeve3893532006-10-02 02:18:22 -0700313 struct ipc_namespace *ns;
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700314 struct ipc_ops sem_ops;
315 struct ipc_params sem_params;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316
Kirill Korotaeve3893532006-10-02 02:18:22 -0700317 ns = current->nsproxy->ipc_ns;
318
319 if (nsems < 0 || nsems > ns->sc_semmsl)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 return -EINVAL;
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700321
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700322 sem_ops.getnew = newary;
323 sem_ops.associate = sem_security;
324 sem_ops.more_checks = sem_more_checks;
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700325
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700326 sem_params.key = key;
327 sem_params.flg = semflg;
328 sem_params.u.nsems = nsems;
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700329
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700330 return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700331}
332
Linus Torvalds1da177e2005-04-16 15:20:36 -0700333/*
334 * Determine whether a sequence of semaphore operations would succeed
335 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
336 */
337
338static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
339 int nsops, struct sem_undo *un, int pid)
340{
341 int result, sem_op;
342 struct sembuf *sop;
343 struct sem * curr;
344
345 for (sop = sops; sop < sops + nsops; sop++) {
346 curr = sma->sem_base + sop->sem_num;
347 sem_op = sop->sem_op;
348 result = curr->semval;
349
350 if (!sem_op && result)
351 goto would_block;
352
353 result += sem_op;
354 if (result < 0)
355 goto would_block;
356 if (result > SEMVMX)
357 goto out_of_range;
358 if (sop->sem_flg & SEM_UNDO) {
359 int undo = un->semadj[sop->sem_num] - sem_op;
360 /*
361 * Exceeding the undo range is an error.
362 */
363 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
364 goto out_of_range;
365 }
366 curr->semval = result;
367 }
368
369 sop--;
370 while (sop >= sops) {
371 sma->sem_base[sop->sem_num].sempid = pid;
372 if (sop->sem_flg & SEM_UNDO)
373 un->semadj[sop->sem_num] -= sop->sem_op;
374 sop--;
375 }
376
377 sma->sem_otime = get_seconds();
378 return 0;
379
380out_of_range:
381 result = -ERANGE;
382 goto undo;
383
384would_block:
385 if (sop->sem_flg & IPC_NOWAIT)
386 result = -EAGAIN;
387 else
388 result = 1;
389
390undo:
391 sop--;
392 while (sop >= sops) {
393 sma->sem_base[sop->sem_num].semval -= sop->sem_op;
394 sop--;
395 }
396
397 return result;
398}
399
400/* Go through the pending queue for the indicated semaphore
401 * looking for tasks that can be completed.
402 */
403static void update_queue (struct sem_array * sma)
404{
405 int error;
406 struct sem_queue * q;
407
Manfred Spraula1193f82008-07-25 01:48:06 -0700408 q = list_entry(sma->sem_pending.next, struct sem_queue, list);
409 while (&q->list != &sma->sem_pending) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700410 error = try_atomic_semop(sma, q->sops, q->nsops,
411 q->undo, q->pid);
412
413 /* Does q->sleeper still need to sleep? */
414 if (error <= 0) {
415 struct sem_queue *n;
Manfred Spraula1193f82008-07-25 01:48:06 -0700416
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 /*
418 * Continue scanning. The next operation
419 * that must be checked depends on the type of the
420 * completed operation:
421 * - if the operation modified the array, then
422 * restart from the head of the queue and
423 * check for threads that might be waiting
424 * for semaphore values to become 0.
425 * - if the operation didn't modify the array,
426 * then just continue.
Manfred Spraula1193f82008-07-25 01:48:06 -0700427 * The order of list_del() and reading ->next
428 * is crucial: In the former case, the list_del()
429 * must be done first [because we might be the
430 * first entry in ->sem_pending], in the latter
431 * case the list_del() must be done last
432 * [because the list is invalid after the list_del()]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433 */
Manfred Spraula1193f82008-07-25 01:48:06 -0700434 if (q->alter) {
435 list_del(&q->list);
436 n = list_entry(sma->sem_pending.next,
437 struct sem_queue, list);
438 } else {
439 n = list_entry(q->list.next, struct sem_queue,
440 list);
441 list_del(&q->list);
442 }
443
444 /* wake up the waiting thread */
445 q->status = IN_WAKEUP;
446
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447 wake_up_process(q->sleeper);
448 /* hands-off: q will disappear immediately after
449 * writing q->status.
450 */
Linus Torvalds1224b372005-12-24 12:19:38 -0800451 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700452 q->status = error;
453 q = n;
454 } else {
Manfred Spraula1193f82008-07-25 01:48:06 -0700455 q = list_entry(q->list.next, struct sem_queue, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700456 }
457 }
458}
459
460/* The following counts are associated to each semaphore:
461 * semncnt number of tasks waiting on semval being nonzero
462 * semzcnt number of tasks waiting on semval being zero
463 * This model assumes that a task waits on exactly one semaphore.
464 * Since semaphore operations are to be performed atomically, tasks actually
465 * wait on a whole sequence of semaphores simultaneously.
466 * The counts we return here are a rough approximation, but still
467 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
468 */
469static int count_semncnt (struct sem_array * sma, ushort semnum)
470{
471 int semncnt;
472 struct sem_queue * q;
473
474 semncnt = 0;
Manfred Spraula1193f82008-07-25 01:48:06 -0700475 list_for_each_entry(q, &sma->sem_pending, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700476 struct sembuf * sops = q->sops;
477 int nsops = q->nsops;
478 int i;
479 for (i = 0; i < nsops; i++)
480 if (sops[i].sem_num == semnum
481 && (sops[i].sem_op < 0)
482 && !(sops[i].sem_flg & IPC_NOWAIT))
483 semncnt++;
484 }
485 return semncnt;
486}
Manfred Spraula1193f82008-07-25 01:48:06 -0700487
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488static int count_semzcnt (struct sem_array * sma, ushort semnum)
489{
490 int semzcnt;
491 struct sem_queue * q;
492
493 semzcnt = 0;
Manfred Spraula1193f82008-07-25 01:48:06 -0700494 list_for_each_entry(q, &sma->sem_pending, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700495 struct sembuf * sops = q->sops;
496 int nsops = q->nsops;
497 int i;
498 for (i = 0; i < nsops; i++)
499 if (sops[i].sem_num == semnum
500 && (sops[i].sem_op == 0)
501 && !(sops[i].sem_flg & IPC_NOWAIT))
502 semzcnt++;
503 }
504 return semzcnt;
505}
506
Manfred Spraul380af1b2008-07-25 01:48:06 -0700507void free_un(struct rcu_head *head)
508{
509 struct sem_undo *un = container_of(head, struct sem_undo, rcu);
510 kfree(un);
511}
512
Nadia Derbey3e148c72007-10-18 23:40:54 -0700513/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
514 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
515 * remains locked on exit.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700516 */
Pierre Peiffer01b8b072008-02-08 04:18:57 -0800517static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518{
Manfred Spraul380af1b2008-07-25 01:48:06 -0700519 struct sem_undo *un, *tu;
520 struct sem_queue *q, *tq;
Pierre Peiffer01b8b072008-02-08 04:18:57 -0800521 struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522
Manfred Spraul380af1b2008-07-25 01:48:06 -0700523 /* Free the existing undo structures for this semaphore set. */
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700524 assert_spin_locked(&sma->sem_perm.lock);
Manfred Spraul380af1b2008-07-25 01:48:06 -0700525 list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
526 list_del(&un->list_id);
527 spin_lock(&un->ulp->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700528 un->semid = -1;
Manfred Spraul380af1b2008-07-25 01:48:06 -0700529 list_del_rcu(&un->list_proc);
530 spin_unlock(&un->ulp->lock);
531 call_rcu(&un->rcu, free_un);
532 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700533
534 /* Wake up all pending processes and let them fail with EIDRM. */
Manfred Spraul380af1b2008-07-25 01:48:06 -0700535 list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
Manfred Spraula1193f82008-07-25 01:48:06 -0700536 list_del(&q->list);
537
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538 q->status = IN_WAKEUP;
539 wake_up_process(q->sleeper); /* doesn't sleep */
Manfred Spraul6003a932005-12-23 23:57:41 +0100540 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700541 q->status = -EIDRM; /* hands-off q */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700542 }
543
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700544 /* Remove the semaphore set from the IDR */
545 sem_rmid(ns, sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700546 sem_unlock(sma);
547
Kirill Korotaeve3893532006-10-02 02:18:22 -0700548 ns->used_sems -= sma->sem_nsems;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700549 security_sem_free(sma);
550 ipc_rcu_putref(sma);
551}
552
553static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
554{
555 switch(version) {
556 case IPC_64:
557 return copy_to_user(buf, in, sizeof(*in));
558 case IPC_OLD:
559 {
560 struct semid_ds out;
561
562 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
563
564 out.sem_otime = in->sem_otime;
565 out.sem_ctime = in->sem_ctime;
566 out.sem_nsems = in->sem_nsems;
567
568 return copy_to_user(buf, &out, sizeof(out));
569 }
570 default:
571 return -EINVAL;
572 }
573}
574
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -0800575static int semctl_nolock(struct ipc_namespace *ns, int semid,
576 int cmd, int version, union semun arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700577{
578 int err = -EINVAL;
579 struct sem_array *sma;
580
581 switch(cmd) {
582 case IPC_INFO:
583 case SEM_INFO:
584 {
585 struct seminfo seminfo;
586 int max_id;
587
588 err = security_sem_semctl(NULL, cmd);
589 if (err)
590 return err;
591
592 memset(&seminfo,0,sizeof(seminfo));
Kirill Korotaeve3893532006-10-02 02:18:22 -0700593 seminfo.semmni = ns->sc_semmni;
594 seminfo.semmns = ns->sc_semmns;
595 seminfo.semmsl = ns->sc_semmsl;
596 seminfo.semopm = ns->sc_semopm;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597 seminfo.semvmx = SEMVMX;
598 seminfo.semmnu = SEMMNU;
599 seminfo.semmap = SEMMAP;
600 seminfo.semume = SEMUME;
Nadia Derbey3e148c72007-10-18 23:40:54 -0700601 down_read(&sem_ids(ns).rw_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602 if (cmd == SEM_INFO) {
Kirill Korotaeve3893532006-10-02 02:18:22 -0700603 seminfo.semusz = sem_ids(ns).in_use;
604 seminfo.semaem = ns->used_sems;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700605 } else {
606 seminfo.semusz = SEMUSZ;
607 seminfo.semaem = SEMAEM;
608 }
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700609 max_id = ipc_get_maxid(&sem_ids(ns));
Nadia Derbey3e148c72007-10-18 23:40:54 -0700610 up_read(&sem_ids(ns).rw_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700611 if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
612 return -EFAULT;
613 return (max_id < 0) ? 0: max_id;
614 }
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -0800615 case IPC_STAT:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700616 case SEM_STAT:
617 {
618 struct semid64_ds tbuf;
619 int id;
620
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -0800621 if (cmd == SEM_STAT) {
622 sma = sem_lock(ns, semid);
623 if (IS_ERR(sma))
624 return PTR_ERR(sma);
625 id = sma->sem_perm.id;
626 } else {
627 sma = sem_lock_check(ns, semid);
628 if (IS_ERR(sma))
629 return PTR_ERR(sma);
630 id = 0;
631 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700632
633 err = -EACCES;
634 if (ipcperms (&sma->sem_perm, S_IRUGO))
635 goto out_unlock;
636
637 err = security_sem_semctl(sma, cmd);
638 if (err)
639 goto out_unlock;
640
Nadia Derbey023a5352007-10-18 23:40:51 -0700641 memset(&tbuf, 0, sizeof(tbuf));
642
Linus Torvalds1da177e2005-04-16 15:20:36 -0700643 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
644 tbuf.sem_otime = sma->sem_otime;
645 tbuf.sem_ctime = sma->sem_ctime;
646 tbuf.sem_nsems = sma->sem_nsems;
647 sem_unlock(sma);
648 if (copy_semid_to_user (arg.buf, &tbuf, version))
649 return -EFAULT;
650 return id;
651 }
652 default:
653 return -EINVAL;
654 }
655 return err;
656out_unlock:
657 sem_unlock(sma);
658 return err;
659}
660
Kirill Korotaeve3893532006-10-02 02:18:22 -0700661static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
662 int cmd, int version, union semun arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700663{
664 struct sem_array *sma;
665 struct sem* curr;
666 int err;
667 ushort fast_sem_io[SEMMSL_FAST];
668 ushort* sem_io = fast_sem_io;
669 int nsems;
670
Nadia Derbey023a5352007-10-18 23:40:51 -0700671 sma = sem_lock_check(ns, semid);
672 if (IS_ERR(sma))
673 return PTR_ERR(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674
675 nsems = sma->sem_nsems;
676
Linus Torvalds1da177e2005-04-16 15:20:36 -0700677 err = -EACCES;
678 if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
679 goto out_unlock;
680
681 err = security_sem_semctl(sma, cmd);
682 if (err)
683 goto out_unlock;
684
685 err = -EACCES;
686 switch (cmd) {
687 case GETALL:
688 {
689 ushort __user *array = arg.array;
690 int i;
691
692 if(nsems > SEMMSL_FAST) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700693 sem_getref_and_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694
695 sem_io = ipc_alloc(sizeof(ushort)*nsems);
696 if(sem_io == NULL) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700697 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 return -ENOMEM;
699 }
700
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700701 sem_lock_and_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700702 if (sma->sem_perm.deleted) {
703 sem_unlock(sma);
704 err = -EIDRM;
705 goto out_free;
706 }
707 }
708
709 for (i = 0; i < sma->sem_nsems; i++)
710 sem_io[i] = sma->sem_base[i].semval;
711 sem_unlock(sma);
712 err = 0;
713 if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
714 err = -EFAULT;
715 goto out_free;
716 }
717 case SETALL:
718 {
719 int i;
720 struct sem_undo *un;
721
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700722 sem_getref_and_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700723
724 if(nsems > SEMMSL_FAST) {
725 sem_io = ipc_alloc(sizeof(ushort)*nsems);
726 if(sem_io == NULL) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700727 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700728 return -ENOMEM;
729 }
730 }
731
732 if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700733 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700734 err = -EFAULT;
735 goto out_free;
736 }
737
738 for (i = 0; i < nsems; i++) {
739 if (sem_io[i] > SEMVMX) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700740 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700741 err = -ERANGE;
742 goto out_free;
743 }
744 }
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700745 sem_lock_and_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700746 if (sma->sem_perm.deleted) {
747 sem_unlock(sma);
748 err = -EIDRM;
749 goto out_free;
750 }
751
752 for (i = 0; i < nsems; i++)
753 sma->sem_base[i].semval = sem_io[i];
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700754
755 assert_spin_locked(&sma->sem_perm.lock);
756 list_for_each_entry(un, &sma->list_id, list_id) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 for (i = 0; i < nsems; i++)
758 un->semadj[i] = 0;
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700759 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700760 sma->sem_ctime = get_seconds();
761 /* maybe some queued-up processes were waiting for this */
762 update_queue(sma);
763 err = 0;
764 goto out_unlock;
765 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700766 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
767 }
768 err = -EINVAL;
769 if(semnum < 0 || semnum >= nsems)
770 goto out_unlock;
771
772 curr = &sma->sem_base[semnum];
773
774 switch (cmd) {
775 case GETVAL:
776 err = curr->semval;
777 goto out_unlock;
778 case GETPID:
779 err = curr->sempid;
780 goto out_unlock;
781 case GETNCNT:
782 err = count_semncnt(sma,semnum);
783 goto out_unlock;
784 case GETZCNT:
785 err = count_semzcnt(sma,semnum);
786 goto out_unlock;
787 case SETVAL:
788 {
789 int val = arg.val;
790 struct sem_undo *un;
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700791
Linus Torvalds1da177e2005-04-16 15:20:36 -0700792 err = -ERANGE;
793 if (val > SEMVMX || val < 0)
794 goto out_unlock;
795
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700796 assert_spin_locked(&sma->sem_perm.lock);
797 list_for_each_entry(un, &sma->list_id, list_id)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700798 un->semadj[semnum] = 0;
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700799
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800 curr->semval = val;
Pavel Emelyanovb4888932007-10-18 23:40:14 -0700801 curr->sempid = task_tgid_vnr(current);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700802 sma->sem_ctime = get_seconds();
803 /* maybe some queued-up processes were waiting for this */
804 update_queue(sma);
805 err = 0;
806 goto out_unlock;
807 }
808 }
809out_unlock:
810 sem_unlock(sma);
811out_free:
812 if(sem_io != fast_sem_io)
813 ipc_free(sem_io, sizeof(ushort)*nsems);
814 return err;
815}
816
Pierre Peiffer016d7132008-04-29 01:00:50 -0700817static inline unsigned long
818copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700819{
820 switch(version) {
821 case IPC_64:
Pierre Peiffer016d7132008-04-29 01:00:50 -0700822 if (copy_from_user(out, buf, sizeof(*out)))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700823 return -EFAULT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700824 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700825 case IPC_OLD:
826 {
827 struct semid_ds tbuf_old;
828
829 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
830 return -EFAULT;
831
Pierre Peiffer016d7132008-04-29 01:00:50 -0700832 out->sem_perm.uid = tbuf_old.sem_perm.uid;
833 out->sem_perm.gid = tbuf_old.sem_perm.gid;
834 out->sem_perm.mode = tbuf_old.sem_perm.mode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700835
836 return 0;
837 }
838 default:
839 return -EINVAL;
840 }
841}
842
Pierre Peiffer522bb2a2008-04-29 01:00:49 -0700843/*
844 * This function handles some semctl commands which require the rw_mutex
845 * to be held in write mode.
846 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
847 */
Pierre Peiffer21a48262008-04-29 01:00:49 -0700848static int semctl_down(struct ipc_namespace *ns, int semid,
849 int cmd, int version, union semun arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700850{
851 struct sem_array *sma;
852 int err;
Pierre Peiffer016d7132008-04-29 01:00:50 -0700853 struct semid64_ds semid64;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700854 struct kern_ipc_perm *ipcp;
855
856 if(cmd == IPC_SET) {
Pierre Peiffer016d7132008-04-29 01:00:50 -0700857 if (copy_semid_from_user(&semid64, arg.buf, version))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700858 return -EFAULT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700859 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700860
Pierre Peiffera5f75e72008-04-29 01:00:54 -0700861 ipcp = ipcctl_pre_down(&sem_ids(ns), semid, cmd, &semid64.sem_perm, 0);
862 if (IS_ERR(ipcp))
863 return PTR_ERR(ipcp);
Steve Grubb073115d2006-04-02 17:07:33 -0400864
Pierre Peiffera5f75e72008-04-29 01:00:54 -0700865 sma = container_of(ipcp, struct sem_array, sem_perm);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700866
867 err = security_sem_semctl(sma, cmd);
868 if (err)
869 goto out_unlock;
870
871 switch(cmd){
872 case IPC_RMID:
Pierre Peiffer01b8b072008-02-08 04:18:57 -0800873 freeary(ns, ipcp);
Pierre Peiffer522bb2a2008-04-29 01:00:49 -0700874 goto out_up;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875 case IPC_SET:
Pierre Peiffer8f4a3802008-04-29 01:00:51 -0700876 ipc_update_perm(&semid64.sem_perm, ipcp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700877 sma->sem_ctime = get_seconds();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700878 break;
879 default:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700880 err = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700881 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700882
883out_unlock:
884 sem_unlock(sma);
Pierre Peiffer522bb2a2008-04-29 01:00:49 -0700885out_up:
886 up_write(&sem_ids(ns).rw_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700887 return err;
888}
889
890asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
891{
892 int err = -EINVAL;
893 int version;
Kirill Korotaeve3893532006-10-02 02:18:22 -0700894 struct ipc_namespace *ns;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700895
896 if (semid < 0)
897 return -EINVAL;
898
899 version = ipc_parse_version(&cmd);
Kirill Korotaeve3893532006-10-02 02:18:22 -0700900 ns = current->nsproxy->ipc_ns;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901
902 switch(cmd) {
903 case IPC_INFO:
904 case SEM_INFO:
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -0800905 case IPC_STAT:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700906 case SEM_STAT:
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -0800907 err = semctl_nolock(ns, semid, cmd, version, arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700908 return err;
909 case GETALL:
910 case GETVAL:
911 case GETPID:
912 case GETNCNT:
913 case GETZCNT:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700914 case SETVAL:
915 case SETALL:
Kirill Korotaeve3893532006-10-02 02:18:22 -0700916 err = semctl_main(ns,semid,semnum,cmd,version,arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700917 return err;
918 case IPC_RMID:
919 case IPC_SET:
Pierre Peiffer21a48262008-04-29 01:00:49 -0700920 err = semctl_down(ns, semid, cmd, version, arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700921 return err;
922 default:
923 return -EINVAL;
924 }
925}
926
Linus Torvalds1da177e2005-04-16 15:20:36 -0700927/* If the task doesn't already have a undo_list, then allocate one
928 * here. We guarantee there is only one thread using this undo list,
929 * and current is THE ONE
930 *
931 * If this allocation and assignment succeeds, but later
932 * portions of this code fail, there is no need to free the sem_undo_list.
933 * Just let it stay associated with the task, and it'll be freed later
934 * at exit time.
935 *
936 * This can block, so callers must hold no locks.
937 */
938static inline int get_undo_list(struct sem_undo_list **undo_listp)
939{
940 struct sem_undo_list *undo_list;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700941
942 undo_list = current->sysvsem.undo_list;
943 if (!undo_list) {
Matt Helsley2453a302006-10-02 02:18:25 -0700944 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700945 if (undo_list == NULL)
946 return -ENOMEM;
Ingo Molnar00a5dfd2005-08-05 23:05:27 +0200947 spin_lock_init(&undo_list->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700948 atomic_set(&undo_list->refcnt, 1);
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700949 INIT_LIST_HEAD(&undo_list->list_proc);
950
Linus Torvalds1da177e2005-04-16 15:20:36 -0700951 current->sysvsem.undo_list = undo_list;
952 }
953 *undo_listp = undo_list;
954 return 0;
955}
956
957static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
958{
Manfred Spraul380af1b2008-07-25 01:48:06 -0700959 struct sem_undo *walk;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960
Manfred Spraul380af1b2008-07-25 01:48:06 -0700961 list_for_each_entry_rcu(walk, &ulp->list_proc, list_proc) {
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700962 if (walk->semid == semid)
963 return walk;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700964 }
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700965 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700966}
967
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700968/**
969 * find_alloc_undo - Lookup (and if not present create) undo array
970 * @ns: namespace
971 * @semid: semaphore array id
972 *
973 * The function looks up (and if not present creates) the undo structure.
974 * The size of the undo structure depends on the size of the semaphore
975 * array, thus the alloc path is not that straightforward.
Manfred Spraul380af1b2008-07-25 01:48:06 -0700976 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
977 * performs a rcu_read_lock().
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700978 */
979static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700980{
981 struct sem_array *sma;
982 struct sem_undo_list *ulp;
983 struct sem_undo *un, *new;
984 int nsems;
985 int error;
986
987 error = get_undo_list(&ulp);
988 if (error)
989 return ERR_PTR(error);
990
Manfred Spraul380af1b2008-07-25 01:48:06 -0700991 rcu_read_lock();
Pierre Peifferc530c6a2007-10-18 23:40:55 -0700992 spin_lock(&ulp->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700993 un = lookup_undo(ulp, semid);
Pierre Peifferc530c6a2007-10-18 23:40:55 -0700994 spin_unlock(&ulp->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995 if (likely(un!=NULL))
996 goto out;
Manfred Spraul380af1b2008-07-25 01:48:06 -0700997 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700998
999 /* no undo structure around - allocate one. */
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001000 /* step 1: figure out the size of the semaphore array */
Nadia Derbey023a5352007-10-18 23:40:51 -07001001 sma = sem_lock_check(ns, semid);
1002 if (IS_ERR(sma))
1003 return ERR_PTR(PTR_ERR(sma));
1004
Linus Torvalds1da177e2005-04-16 15:20:36 -07001005 nsems = sma->sem_nsems;
Pierre Peiffer6ff37972008-04-29 01:00:46 -07001006 sem_getref_and_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001007
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001008 /* step 2: allocate new undo structure */
Burman Yan4668edc2006-12-06 20:38:51 -08001009 new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001010 if (!new) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -07001011 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001012 return ERR_PTR(-ENOMEM);
1013 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014
Manfred Spraul380af1b2008-07-25 01:48:06 -07001015 /* step 3: Acquire the lock on semaphore array */
Pierre Peiffer6ff37972008-04-29 01:00:46 -07001016 sem_lock_and_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017 if (sma->sem_perm.deleted) {
1018 sem_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001019 kfree(new);
1020 un = ERR_PTR(-EIDRM);
1021 goto out;
1022 }
Manfred Spraul380af1b2008-07-25 01:48:06 -07001023 spin_lock(&ulp->lock);
1024
1025 /*
1026 * step 4: check for races: did someone else allocate the undo struct?
1027 */
1028 un = lookup_undo(ulp, semid);
1029 if (un) {
1030 kfree(new);
1031 goto success;
1032 }
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001033 /* step 5: initialize & link new undo structure */
1034 new->semadj = (short *) &new[1];
Manfred Spraul380af1b2008-07-25 01:48:06 -07001035 new->ulp = ulp;
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001036 new->semid = semid;
1037 assert_spin_locked(&ulp->lock);
Manfred Spraul380af1b2008-07-25 01:48:06 -07001038 list_add_rcu(&new->list_proc, &ulp->list_proc);
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001039 assert_spin_locked(&sma->sem_perm.lock);
1040 list_add(&new->list_id, &sma->list_id);
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001041 un = new;
Manfred Spraul380af1b2008-07-25 01:48:06 -07001042
1043success:
1044 spin_unlock(&ulp->lock);
1045 rcu_read_lock();
1046 sem_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001047out:
1048 return un;
1049}
1050
1051asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
1052 unsigned nsops, const struct timespec __user *timeout)
1053{
1054 int error = -EINVAL;
1055 struct sem_array *sma;
1056 struct sembuf fast_sops[SEMOPM_FAST];
1057 struct sembuf* sops = fast_sops, *sop;
1058 struct sem_undo *un;
Manfred Spraulb78755a2005-06-23 00:10:06 -07001059 int undos = 0, alter = 0, max;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060 struct sem_queue queue;
1061 unsigned long jiffies_left = 0;
Kirill Korotaeve3893532006-10-02 02:18:22 -07001062 struct ipc_namespace *ns;
1063
1064 ns = current->nsproxy->ipc_ns;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065
1066 if (nsops < 1 || semid < 0)
1067 return -EINVAL;
Kirill Korotaeve3893532006-10-02 02:18:22 -07001068 if (nsops > ns->sc_semopm)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069 return -E2BIG;
1070 if(nsops > SEMOPM_FAST) {
1071 sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1072 if(sops==NULL)
1073 return -ENOMEM;
1074 }
1075 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1076 error=-EFAULT;
1077 goto out_free;
1078 }
1079 if (timeout) {
1080 struct timespec _timeout;
1081 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1082 error = -EFAULT;
1083 goto out_free;
1084 }
1085 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1086 _timeout.tv_nsec >= 1000000000L) {
1087 error = -EINVAL;
1088 goto out_free;
1089 }
1090 jiffies_left = timespec_to_jiffies(&_timeout);
1091 }
1092 max = 0;
1093 for (sop = sops; sop < sops + nsops; sop++) {
1094 if (sop->sem_num >= max)
1095 max = sop->sem_num;
1096 if (sop->sem_flg & SEM_UNDO)
Manfred Spraulb78755a2005-06-23 00:10:06 -07001097 undos = 1;
1098 if (sop->sem_op != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001099 alter = 1;
1100 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102 if (undos) {
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001103 un = find_alloc_undo(ns, semid);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001104 if (IS_ERR(un)) {
1105 error = PTR_ERR(un);
1106 goto out_free;
1107 }
1108 } else
1109 un = NULL;
1110
Nadia Derbey023a5352007-10-18 23:40:51 -07001111 sma = sem_lock_check(ns, semid);
1112 if (IS_ERR(sma)) {
Manfred Spraul380af1b2008-07-25 01:48:06 -07001113 if (un)
1114 rcu_read_unlock();
Nadia Derbey023a5352007-10-18 23:40:51 -07001115 error = PTR_ERR(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001116 goto out_free;
Nadia Derbey023a5352007-10-18 23:40:51 -07001117 }
1118
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119 /*
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001120 * semid identifiers are not unique - find_alloc_undo may have
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121 * allocated an undo structure, it was invalidated by an RMID
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001122 * and now a new array with received the same id. Check and fail.
Manfred Spraul380af1b2008-07-25 01:48:06 -07001123 * This case can be detected checking un->semid. The existance of
1124 * "un" itself is guaranteed by rcu.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001125 */
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001126 error = -EIDRM;
Manfred Spraul380af1b2008-07-25 01:48:06 -07001127 if (un) {
1128 if (un->semid == -1) {
1129 rcu_read_unlock();
1130 goto out_unlock_free;
1131 } else {
1132 /*
1133 * rcu lock can be released, "un" cannot disappear:
1134 * - sem_lock is acquired, thus IPC_RMID is
1135 * impossible.
1136 * - exit_sem is impossible, it always operates on
1137 * current (or a dead task).
1138 */
1139
1140 rcu_read_unlock();
1141 }
1142 }
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001143
Linus Torvalds1da177e2005-04-16 15:20:36 -07001144 error = -EFBIG;
1145 if (max >= sma->sem_nsems)
1146 goto out_unlock_free;
1147
1148 error = -EACCES;
1149 if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1150 goto out_unlock_free;
1151
1152 error = security_sem_semop(sma, sops, nsops, alter);
1153 if (error)
1154 goto out_unlock_free;
1155
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001156 error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001157 if (error <= 0) {
1158 if (alter && error == 0)
1159 update_queue (sma);
1160 goto out_unlock_free;
1161 }
1162
1163 /* We need to sleep on this operation, so we put the current
1164 * task into the pending queue and go to sleep.
1165 */
1166
Linus Torvalds1da177e2005-04-16 15:20:36 -07001167 queue.sops = sops;
1168 queue.nsops = nsops;
1169 queue.undo = un;
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001170 queue.pid = task_tgid_vnr(current);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001171 queue.alter = alter;
1172 if (alter)
Manfred Spraula1193f82008-07-25 01:48:06 -07001173 list_add_tail(&queue.list, &sma->sem_pending);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001174 else
Manfred Spraula1193f82008-07-25 01:48:06 -07001175 list_add(&queue.list, &sma->sem_pending);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001176
1177 queue.status = -EINTR;
1178 queue.sleeper = current;
1179 current->state = TASK_INTERRUPTIBLE;
1180 sem_unlock(sma);
1181
1182 if (timeout)
1183 jiffies_left = schedule_timeout(jiffies_left);
1184 else
1185 schedule();
1186
1187 error = queue.status;
1188 while(unlikely(error == IN_WAKEUP)) {
1189 cpu_relax();
1190 error = queue.status;
1191 }
1192
1193 if (error != -EINTR) {
1194 /* fast path: update_queue already obtained all requested
1195 * resources */
1196 goto out_free;
1197 }
1198
Kirill Korotaeve3893532006-10-02 02:18:22 -07001199 sma = sem_lock(ns, semid);
Nadia Derbey023a5352007-10-18 23:40:51 -07001200 if (IS_ERR(sma)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001201 error = -EIDRM;
1202 goto out_free;
1203 }
1204
1205 /*
1206 * If queue.status != -EINTR we are woken up by another process
1207 */
1208 error = queue.status;
1209 if (error != -EINTR) {
1210 goto out_unlock_free;
1211 }
1212
1213 /*
1214 * If an interrupt occurred we have to clean up the queue
1215 */
1216 if (timeout && jiffies_left == 0)
1217 error = -EAGAIN;
Manfred Spraula1193f82008-07-25 01:48:06 -07001218 list_del(&queue.list);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001219 goto out_unlock_free;
1220
1221out_unlock_free:
1222 sem_unlock(sma);
1223out_free:
1224 if(sops != fast_sops)
1225 kfree(sops);
1226 return error;
1227}
1228
1229asmlinkage long sys_semop (int semid, struct sembuf __user *tsops, unsigned nsops)
1230{
1231 return sys_semtimedop(semid, tsops, nsops, NULL);
1232}
1233
1234/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1235 * parent and child tasks.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236 */
1237
1238int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1239{
1240 struct sem_undo_list *undo_list;
1241 int error;
1242
1243 if (clone_flags & CLONE_SYSVSEM) {
1244 error = get_undo_list(&undo_list);
1245 if (error)
1246 return error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247 atomic_inc(&undo_list->refcnt);
1248 tsk->sysvsem.undo_list = undo_list;
1249 } else
1250 tsk->sysvsem.undo_list = NULL;
1251
1252 return 0;
1253}
1254
1255/*
1256 * add semadj values to semaphores, free undo structures.
1257 * undo structures are not freed when semaphore arrays are destroyed
1258 * so some of them may be out of date.
1259 * IMPLEMENTATION NOTE: There is some confusion over whether the
1260 * set of adjustments that needs to be done should be done in an atomic
1261 * manner or not. That is, if we are attempting to decrement the semval
1262 * should we queue up and wait until we can do so legally?
1263 * The original implementation attempted to do this (queue and wait).
1264 * The current implementation does not do so. The POSIX standard
1265 * and SVID should be consulted to determine what behavior is mandated.
1266 */
1267void exit_sem(struct task_struct *tsk)
1268{
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001269 struct sem_undo_list *ulp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001270
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001271 ulp = tsk->sysvsem.undo_list;
1272 if (!ulp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273 return;
Manfred Spraul9edff4a2008-04-29 01:00:57 -07001274 tsk->sysvsem.undo_list = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001275
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001276 if (!atomic_dec_and_test(&ulp->refcnt))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001277 return;
1278
Manfred Spraul380af1b2008-07-25 01:48:06 -07001279 for (;;) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001280 struct sem_array *sma;
Manfred Spraul380af1b2008-07-25 01:48:06 -07001281 struct sem_undo *un;
1282 int semid;
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001283 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001284
Manfred Spraul380af1b2008-07-25 01:48:06 -07001285 rcu_read_lock();
1286 un = list_entry(rcu_dereference(ulp->list_proc.next),
1287 struct sem_undo, list_proc);
1288 if (&un->list_proc == &ulp->list_proc)
1289 semid = -1;
1290 else
1291 semid = un->semid;
1292 rcu_read_unlock();
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001293
Manfred Spraul380af1b2008-07-25 01:48:06 -07001294 if (semid == -1)
1295 break;
1296
1297 sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);
1298
1299 /* exit_sem raced with IPC_RMID, nothing to do */
Nadia Derbey023a5352007-10-18 23:40:51 -07001300 if (IS_ERR(sma))
Manfred Spraul380af1b2008-07-25 01:48:06 -07001301 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001302
Manfred Spraul380af1b2008-07-25 01:48:06 -07001303 un = lookup_undo(ulp, semid);
1304 if (un == NULL) {
1305 /* exit_sem raced with IPC_RMID+semget() that created
1306 * exactly the same semid. Nothing to do.
1307 */
1308 sem_unlock(sma);
1309 continue;
1310 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001311
Manfred Spraul380af1b2008-07-25 01:48:06 -07001312 /* remove un from the linked lists */
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001313 assert_spin_locked(&sma->sem_perm.lock);
1314 list_del(&un->list_id);
1315
Manfred Spraul380af1b2008-07-25 01:48:06 -07001316 spin_lock(&ulp->lock);
1317 list_del_rcu(&un->list_proc);
1318 spin_unlock(&ulp->lock);
1319
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001320 /* perform adjustments registered in un */
1321 for (i = 0; i < sma->sem_nsems; i++) {
Ingo Molnar5f921ae2006-03-26 01:37:17 -08001322 struct sem * semaphore = &sma->sem_base[i];
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001323 if (un->semadj[i]) {
1324 semaphore->semval += un->semadj[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325 /*
1326 * Range checks of the new semaphore value,
1327 * not defined by sus:
1328 * - Some unices ignore the undo entirely
1329 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1330 * - some cap the value (e.g. FreeBSD caps
1331 * at 0, but doesn't enforce SEMVMX)
1332 *
1333 * Linux caps the semaphore value, both at 0
1334 * and at SEMVMX.
1335 *
1336 * Manfred <manfred@colorfullife.com>
1337 */
Ingo Molnar5f921ae2006-03-26 01:37:17 -08001338 if (semaphore->semval < 0)
1339 semaphore->semval = 0;
1340 if (semaphore->semval > SEMVMX)
1341 semaphore->semval = SEMVMX;
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001342 semaphore->sempid = task_tgid_vnr(current);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343 }
1344 }
1345 sma->sem_otime = get_seconds();
1346 /* maybe some queued-up processes were waiting for this */
1347 update_queue(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348 sem_unlock(sma);
Manfred Spraul380af1b2008-07-25 01:48:06 -07001349
1350 call_rcu(&un->rcu, free_un);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351 }
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001352 kfree(ulp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353}
1354
1355#ifdef CONFIG_PROC_FS
Mike Waychison19b49462005-09-06 15:17:10 -07001356static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001357{
Mike Waychison19b49462005-09-06 15:17:10 -07001358 struct sem_array *sma = it;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001359
Mike Waychison19b49462005-09-06 15:17:10 -07001360 return seq_printf(s,
1361 "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
1362 sma->sem_perm.key,
Nadia Derbey7ca7e562007-10-18 23:40:48 -07001363 sma->sem_perm.id,
Mike Waychison19b49462005-09-06 15:17:10 -07001364 sma->sem_perm.mode,
1365 sma->sem_nsems,
1366 sma->sem_perm.uid,
1367 sma->sem_perm.gid,
1368 sma->sem_perm.cuid,
1369 sma->sem_perm.cgid,
1370 sma->sem_otime,
1371 sma->sem_ctime);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001372}
1373#endif