sem.c revision 2e094abf
1/*
2 * linux/ipc/sem.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
5 *
6 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
7 *
8 * SMP-threaded, sysctl's added
9 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
10 * Enforced range limit on SEM_UNDO
11 * (c) 2001 Red Hat Inc
12 * Lockless wakeup
13 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
14 * Further wakeup optimizations, documentation
15 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
16 *
17 * support for audit of ipc object properties and permission changes
18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
19 *
20 * namespaces support
21 * OpenVZ, SWsoft Inc.
22 * Pavel Emelianov <xemul@openvz.org>
23 *
24 * Implementation notes: (May 2010)
25 * This file implements System V semaphores.
26 *
27 * User space visible behavior:
28 * - FIFO ordering for semop() operations (just FIFO, not starvation
29 *   protection)
30 * - multiple semaphore operations that alter the same semaphore in
31 *   one semop() are handled.
32 * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
33 *   SETALL calls.
34 * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
35 * - undo adjustments at process exit are limited to 0..SEMVMX.
36 * - namespace are supported.
37 * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
38 *   to /proc/sys/kernel/sem.
39 * - statistics about the usage are reported in /proc/sysvipc/sem.
40 *
41 * Internals:
42 * - scalability:
43 *   - all global variables are read-mostly.
44 *   - semop() calls and semctl(RMID) are synchronized by RCU.
45 *   - most operations do write operations (actually: spin_lock calls) to
46 *     the per-semaphore array structure.
47 *   Thus: Perfect SMP scaling between independent semaphore arrays.
48 *         If multiple semaphores in one array are used, then cache line
49 *         trashing on the semaphore array spinlock will limit the scaling.
50 * - semncnt and semzcnt are calculated on demand in count_semcnt()
51 * - the task that performs a successful semop() scans the list of all
52 *   sleeping tasks and completes any pending operations that can be fulfilled.
53 *   Semaphores are actively given to waiting tasks (necessary for FIFO).
54 *   (see update_queue())
55 * - To improve the scalability, the actual wake-up calls are performed after
56 *   dropping all locks. (see wake_up_sem_queue_prepare(),
57 *   wake_up_sem_queue_do())
58 * - All work is done by the waker, the woken up task does not have to do
59 *   anything - not even acquiring a lock or dropping a refcount.
60 * - A woken up task may not even touch the semaphore array anymore, it may
61 *   have been destroyed already by a semctl(RMID).
62 * - The synchronizations between wake-ups due to a timeout/signal and a
63 *   wake-up due to a completed semaphore operation is achieved by using an
64 *   intermediate state (IN_WAKEUP).
65 * - UNDO values are stored in an array (one per process and per
66 *   semaphore array, lazily allocated). For backwards compatibility, multiple
67 *   modes for the UNDO variables are supported (per process, per thread)
68 *   (see copy_semundo, CLONE_SYSVSEM)
69 * - There are two lists of the pending operations: a per-array list
70 *   and per-semaphore list (stored in the array). This allows to achieve FIFO
71 *   ordering without always scanning all pending operations.
72 *   The worst-case behavior is nevertheless O(N^2) for N wakeups.
73 */
74
75#include <linux/slab.h>
76#include <linux/spinlock.h>
77#include <linux/init.h>
78#include <linux/proc_fs.h>
79#include <linux/time.h>
80#include <linux/security.h>
81#include <linux/syscalls.h>
82#include <linux/audit.h>
83#include <linux/capability.h>
84#include <linux/seq_file.h>
85#include <linux/rwsem.h>
86#include <linux/nsproxy.h>
87#include <linux/ipc_namespace.h>
88
89#include <linux/uaccess.h>
90#include "util.h"
91
92/* One semaphore structure for each semaphore in the system. */
93struct sem {
94	int	semval;		/* current value */
95	int	sempid;		/* pid of last operation */
96	spinlock_t	lock;	/* spinlock for fine-grained semtimedop */
97	struct list_head pending_alter; /* pending single-sop operations */
98					/* that alter the semaphore */
99	struct list_head pending_const; /* pending single-sop operations */
100					/* that do not alter the semaphore*/
101	time_t	sem_otime;	/* candidate for sem_otime */
102} ____cacheline_aligned_in_smp;
103
104/* One queue for each sleeping process in the system. */
105struct sem_queue {
106	struct list_head	list;	 /* queue of pending operations */
107	struct task_struct	*sleeper; /* this process */
108	struct sem_undo		*undo;	 /* undo structure */
109	int			pid;	 /* process id of requesting process */
110	int			status;	 /* completion status of operation */
111	struct sembuf		*sops;	 /* array of pending operations */
112	struct sembuf		*blocking; /* the operation that blocked */
113	int			nsops;	 /* number of operations */
114	int			alter;	 /* does *sops alter the array? */
115};
116
117/* Each task has a list of undo requests. They are executed automatically
118 * when the process exits.
119 */
120struct sem_undo {
121	struct list_head	list_proc;	/* per-process list: *
122						 * all undos from one process
123						 * rcu protected */
124	struct rcu_head		rcu;		/* rcu struct for sem_undo */
125	struct sem_undo_list	*ulp;		/* back ptr to sem_undo_list */
126	struct list_head	list_id;	/* per semaphore array list:
127						 * all undos for one array */
128	int			semid;		/* semaphore set identifier */
129	short			*semadj;	/* array of adjustments */
130						/* one per semaphore */
131};
132
133/* sem_undo_list controls shared access to the list of sem_undo structures
134 * that may be shared among all a CLONE_SYSVSEM task group.
135 */
136struct sem_undo_list {
137	atomic_t		refcnt;
138	spinlock_t		lock;
139	struct list_head	list_proc;
140};
141
142
143#define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
144
145#define sem_checkid(sma, semid)	ipc_checkid(&sma->sem_perm, semid)
146
147static int newary(struct ipc_namespace *, struct ipc_params *);
148static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
149#ifdef CONFIG_PROC_FS
150static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
151#endif
152
153#define SEMMSL_FAST	256 /* 512 bytes on stack */
154#define SEMOPM_FAST	64  /* ~ 372 bytes on stack */
155
156/*
157 * Locking:
158 *	sem_undo.id_next,
159 *	sem_array.complex_count,
160 *	sem_array.pending{_alter,_cont},
161 *	sem_array.sem_undo: global sem_lock() for read/write
162 *	sem_undo.proc_next: only "current" is allowed to read/write that field.
163 *
164 *	sem_array.sem_base[i].pending_{const,alter}:
165 *		global or semaphore sem_lock() for read/write
166 */
167
168#define sc_semmsl	sem_ctls[0]
169#define sc_semmns	sem_ctls[1]
170#define sc_semopm	sem_ctls[2]
171#define sc_semmni	sem_ctls[3]
172
173void sem_init_ns(struct ipc_namespace *ns)
174{
175	ns->sc_semmsl = SEMMSL;
176	ns->sc_semmns = SEMMNS;
177	ns->sc_semopm = SEMOPM;
178	ns->sc_semmni = SEMMNI;
179	ns->used_sems = 0;
180	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
181}
182
183#ifdef CONFIG_IPC_NS
184void sem_exit_ns(struct ipc_namespace *ns)
185{
186	free_ipcs(ns, &sem_ids(ns), freeary);
187	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
188}
189#endif
190
191void __init sem_init(void)
192{
193	sem_init_ns(&init_ipc_ns);
194	ipc_init_proc_interface("sysvipc/sem",
195				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
196				IPC_SEM_IDS, sysvipc_sem_proc_show);
197}
198
199/**
200 * unmerge_queues - unmerge queues, if possible.
201 * @sma: semaphore array
202 *
203 * The function unmerges the wait queues if complex_count is 0.
204 * It must be called prior to dropping the global semaphore array lock.
205 */
206static void unmerge_queues(struct sem_array *sma)
207{
208	struct sem_queue *q, *tq;
209
210	/* complex operations still around? */
211	if (sma->complex_count)
212		return;
213	/*
214	 * We will switch back to simple mode.
215	 * Move all pending operation back into the per-semaphore
216	 * queues.
217	 */
218	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
219		struct sem *curr;
220		curr = &sma->sem_base[q->sops[0].sem_num];
221
222		list_add_tail(&q->list, &curr->pending_alter);
223	}
224	INIT_LIST_HEAD(&sma->pending_alter);
225}
226
227/**
228 * merge_queues - merge single semop queues into global queue
229 * @sma: semaphore array
230 *
231 * This function merges all per-semaphore queues into the global queue.
232 * It is necessary to achieve FIFO ordering for the pending single-sop
233 * operations when a multi-semop operation must sleep.
234 * Only the alter operations must be moved, the const operations can stay.
235 */
236static void merge_queues(struct sem_array *sma)
237{
238	int i;
239	for (i = 0; i < sma->sem_nsems; i++) {
240		struct sem *sem = sma->sem_base + i;
241
242		list_splice_init(&sem->pending_alter, &sma->pending_alter);
243	}
244}
245
246static void sem_rcu_free(struct rcu_head *head)
247{
248	struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
249	struct sem_array *sma = ipc_rcu_to_struct(p);
250
251	security_sem_free(sma);
252	ipc_rcu_free(head);
253}
254
255/*
256 * Wait until all currently ongoing simple ops have completed.
257 * Caller must own sem_perm.lock.
258 * New simple ops cannot start, because simple ops first check
259 * that sem_perm.lock is free.
260 * that a) sem_perm.lock is free and b) complex_count is 0.
261 */
262static void sem_wait_array(struct sem_array *sma)
263{
264	int i;
265	struct sem *sem;
266
267	if (sma->complex_count)  {
268		/* The thread that increased sma->complex_count waited on
269		 * all sem->lock locks. Thus we don't need to wait again.
270		 */
271		return;
272	}
273
274	for (i = 0; i < sma->sem_nsems; i++) {
275		sem = sma->sem_base + i;
276		spin_unlock_wait(&sem->lock);
277	}
278}
279
280/*
281 * If the request contains only one semaphore operation, and there are
282 * no complex transactions pending, lock only the semaphore involved.
283 * Otherwise, lock the entire semaphore array, since we either have
284 * multiple semaphores in our own semops, or we need to look at
285 * semaphores from other pending complex operations.
286 */
287static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
288			      int nsops)
289{
290	struct sem *sem;
291
292	if (nsops != 1) {
293		/* Complex operation - acquire a full lock */
294		ipc_lock_object(&sma->sem_perm);
295
296		/* And wait until all simple ops that are processed
297		 * right now have dropped their locks.
298		 */
299		sem_wait_array(sma);
300		return -1;
301	}
302
303	/*
304	 * Only one semaphore affected - try to optimize locking.
305	 * The rules are:
306	 * - optimized locking is possible if no complex operation
307	 *   is either enqueued or processed right now.
308	 * - The test for enqueued complex ops is simple:
309	 *      sma->complex_count != 0
310	 * - Testing for complex ops that are processed right now is
311	 *   a bit more difficult. Complex ops acquire the full lock
312	 *   and first wait that the running simple ops have completed.
313	 *   (see above)
314	 *   Thus: If we own a simple lock and the global lock is free
315	 *	and complex_count is now 0, then it will stay 0 and
316	 *	thus just locking sem->lock is sufficient.
317	 */
318	sem = sma->sem_base + sops->sem_num;
319
320	if (sma->complex_count == 0) {
321		/*
322		 * It appears that no complex operation is around.
323		 * Acquire the per-semaphore lock.
324		 */
325		spin_lock(&sem->lock);
326
327		/* Then check that the global lock is free */
328		if (!spin_is_locked(&sma->sem_perm.lock)) {
329			/*
330			 * The ipc object lock check must be visible on all
331			 * cores before rechecking the complex count.  Otherwise
332			 * we can race with  another thread that does:
333			 *	complex_count++;
334			 *	spin_unlock(sem_perm.lock);
335			 */
336			smp_rmb();
337
338			/*
339			 * Now repeat the test of complex_count:
340			 * It can't change anymore until we drop sem->lock.
341			 * Thus: if is now 0, then it will stay 0.
342			 */
343			if (sma->complex_count == 0) {
344				/* fast path successful! */
345				return sops->sem_num;
346			}
347		}
348		spin_unlock(&sem->lock);
349	}
350
351	/* slow path: acquire the full lock */
352	ipc_lock_object(&sma->sem_perm);
353
354	if (sma->complex_count == 0) {
355		/* False alarm:
356		 * There is no complex operation, thus we can switch
357		 * back to the fast path.
358		 */
359		spin_lock(&sem->lock);
360		ipc_unlock_object(&sma->sem_perm);
361		return sops->sem_num;
362	} else {
363		/* Not a false alarm, thus complete the sequence for a
364		 * full lock.
365		 */
366		sem_wait_array(sma);
367		return -1;
368	}
369}
370
371static inline void sem_unlock(struct sem_array *sma, int locknum)
372{
373	if (locknum == -1) {
374		unmerge_queues(sma);
375		ipc_unlock_object(&sma->sem_perm);
376	} else {
377		struct sem *sem = sma->sem_base + locknum;
378		spin_unlock(&sem->lock);
379	}
380}
381
382/*
383 * sem_lock_(check_) routines are called in the paths where the rwsem
384 * is not held.
385 *
386 * The caller holds the RCU read lock.
387 */
388static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
389			int id, struct sembuf *sops, int nsops, int *locknum)
390{
391	struct kern_ipc_perm *ipcp;
392	struct sem_array *sma;
393
394	ipcp = ipc_obtain_object(&sem_ids(ns), id);
395	if (IS_ERR(ipcp))
396		return ERR_CAST(ipcp);
397
398	sma = container_of(ipcp, struct sem_array, sem_perm);
399	*locknum = sem_lock(sma, sops, nsops);
400
401	/* ipc_rmid() may have already freed the ID while sem_lock
402	 * was spinning: verify that the structure is still valid
403	 */
404	if (ipc_valid_object(ipcp))
405		return container_of(ipcp, struct sem_array, sem_perm);
406
407	sem_unlock(sma, *locknum);
408	return ERR_PTR(-EINVAL);
409}
410
411static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
412{
413	struct kern_ipc_perm *ipcp = ipc_obtain_object(&sem_ids(ns), id);
414
415	if (IS_ERR(ipcp))
416		return ERR_CAST(ipcp);
417
418	return container_of(ipcp, struct sem_array, sem_perm);
419}
420
421static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
422							int id)
423{
424	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
425
426	if (IS_ERR(ipcp))
427		return ERR_CAST(ipcp);
428
429	return container_of(ipcp, struct sem_array, sem_perm);
430}
431
432static inline void sem_lock_and_putref(struct sem_array *sma)
433{
434	sem_lock(sma, NULL, -1);
435	ipc_rcu_putref(sma, ipc_rcu_free);
436}
437
438static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
439{
440	ipc_rmid(&sem_ids(ns), &s->sem_perm);
441}
442
443/*
444 * Lockless wakeup algorithm:
445 * Without the check/retry algorithm a lockless wakeup is possible:
446 * - queue.status is initialized to -EINTR before blocking.
447 * - wakeup is performed by
448 *	* unlinking the queue entry from the pending list
449 *	* setting queue.status to IN_WAKEUP
450 *	  This is the notification for the blocked thread that a
451 *	  result value is imminent.
452 *	* call wake_up_process
453 *	* set queue.status to the final value.
454 * - the previously blocked thread checks queue.status:
455 *	* if it's IN_WAKEUP, then it must wait until the value changes
456 *	* if it's not -EINTR, then the operation was completed by
457 *	  update_queue. semtimedop can return queue.status without
458 *	  performing any operation on the sem array.
459 *	* otherwise it must acquire the spinlock and check what's up.
460 *
461 * The two-stage algorithm is necessary to protect against the following
462 * races:
463 * - if queue.status is set after wake_up_process, then the woken up idle
464 *   thread could race forward and try (and fail) to acquire sma->lock
465 *   before update_queue had a chance to set queue.status
466 * - if queue.status is written before wake_up_process and if the
467 *   blocked process is woken up by a signal between writing
468 *   queue.status and the wake_up_process, then the woken up
469 *   process could return from semtimedop and die by calling
470 *   sys_exit before wake_up_process is called. Then wake_up_process
471 *   will oops, because the task structure is already invalid.
472 *   (yes, this happened on s390 with sysv msg).
473 *
474 */
475#define IN_WAKEUP	1
476
477/**
478 * newary - Create a new semaphore set
479 * @ns: namespace
480 * @params: ptr to the structure that contains key, semflg and nsems
481 *
482 * Called with sem_ids.rwsem held (as a writer)
483 */
484static int newary(struct ipc_namespace *ns, struct ipc_params *params)
485{
486	int id;
487	int retval;
488	struct sem_array *sma;
489	int size;
490	key_t key = params->key;
491	int nsems = params->u.nsems;
492	int semflg = params->flg;
493	int i;
494
495	if (!nsems)
496		return -EINVAL;
497	if (ns->used_sems + nsems > ns->sc_semmns)
498		return -ENOSPC;
499
500	size = sizeof(*sma) + nsems * sizeof(struct sem);
501	sma = ipc_rcu_alloc(size);
502	if (!sma)
503		return -ENOMEM;
504
505	memset(sma, 0, size);
506
507	sma->sem_perm.mode = (semflg & S_IRWXUGO);
508	sma->sem_perm.key = key;
509
510	sma->sem_perm.security = NULL;
511	retval = security_sem_alloc(sma);
512	if (retval) {
513		ipc_rcu_putref(sma, ipc_rcu_free);
514		return retval;
515	}
516
517	sma->sem_base = (struct sem *) &sma[1];
518
519	for (i = 0; i < nsems; i++) {
520		INIT_LIST_HEAD(&sma->sem_base[i].pending_alter);
521		INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
522		spin_lock_init(&sma->sem_base[i].lock);
523	}
524
525	sma->complex_count = 0;
526	INIT_LIST_HEAD(&sma->pending_alter);
527	INIT_LIST_HEAD(&sma->pending_const);
528	INIT_LIST_HEAD(&sma->list_id);
529	sma->sem_nsems = nsems;
530	sma->sem_ctime = get_seconds();
531
532	id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
533	if (id < 0) {
534		ipc_rcu_putref(sma, sem_rcu_free);
535		return id;
536	}
537	ns->used_sems += nsems;
538
539	sem_unlock(sma, -1);
540	rcu_read_unlock();
541
542	return sma->sem_perm.id;
543}
544
545
546/*
547 * Called with sem_ids.rwsem and ipcp locked.
548 */
549static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
550{
551	struct sem_array *sma;
552
553	sma = container_of(ipcp, struct sem_array, sem_perm);
554	return security_sem_associate(sma, semflg);
555}
556
557/*
558 * Called with sem_ids.rwsem and ipcp locked.
559 */
560static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
561				struct ipc_params *params)
562{
563	struct sem_array *sma;
564
565	sma = container_of(ipcp, struct sem_array, sem_perm);
566	if (params->u.nsems > sma->sem_nsems)
567		return -EINVAL;
568
569	return 0;
570}
571
572SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
573{
574	struct ipc_namespace *ns;
575	static const struct ipc_ops sem_ops = {
576		.getnew = newary,
577		.associate = sem_security,
578		.more_checks = sem_more_checks,
579	};
580	struct ipc_params sem_params;
581
582	ns = current->nsproxy->ipc_ns;
583
584	if (nsems < 0 || nsems > ns->sc_semmsl)
585		return -EINVAL;
586
587	sem_params.key = key;
588	sem_params.flg = semflg;
589	sem_params.u.nsems = nsems;
590
591	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
592}
593
594/**
595 * perform_atomic_semop - Perform (if possible) a semaphore operation
596 * @sma: semaphore array
597 * @q: struct sem_queue that describes the operation
598 *
599 * Returns 0 if the operation was possible.
600 * Returns 1 if the operation is impossible, the caller must sleep.
601 * Negative values are error codes.
602 */
603static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
604{
605	int result, sem_op, nsops, pid;
606	struct sembuf *sop;
607	struct sem *curr;
608	struct sembuf *sops;
609	struct sem_undo *un;
610
611	sops = q->sops;
612	nsops = q->nsops;
613	un = q->undo;
614
615	for (sop = sops; sop < sops + nsops; sop++) {
616		curr = sma->sem_base + sop->sem_num;
617		sem_op = sop->sem_op;
618		result = curr->semval;
619
620		if (!sem_op && result)
621			goto would_block;
622
623		result += sem_op;
624		if (result < 0)
625			goto would_block;
626		if (result > SEMVMX)
627			goto out_of_range;
628
629		if (sop->sem_flg & SEM_UNDO) {
630			int undo = un->semadj[sop->sem_num] - sem_op;
631			/* Exceeding the undo range is an error. */
632			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
633				goto out_of_range;
634			un->semadj[sop->sem_num] = undo;
635		}
636
637		curr->semval = result;
638	}
639
640	sop--;
641	pid = q->pid;
642	while (sop >= sops) {
643		sma->sem_base[sop->sem_num].sempid = pid;
644		sop--;
645	}
646
647	return 0;
648
649out_of_range:
650	result = -ERANGE;
651	goto undo;
652
653would_block:
654	q->blocking = sop;
655
656	if (sop->sem_flg & IPC_NOWAIT)
657		result = -EAGAIN;
658	else
659		result = 1;
660
661undo:
662	sop--;
663	while (sop >= sops) {
664		sem_op = sop->sem_op;
665		sma->sem_base[sop->sem_num].semval -= sem_op;
666		if (sop->sem_flg & SEM_UNDO)
667			un->semadj[sop->sem_num] += sem_op;
668		sop--;
669	}
670
671	return result;
672}
673
674/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
675 * @q: queue entry that must be signaled
676 * @error: Error value for the signal
677 *
678 * Prepare the wake-up of the queue entry q.
679 */
680static void wake_up_sem_queue_prepare(struct list_head *pt,
681				struct sem_queue *q, int error)
682{
683	if (list_empty(pt)) {
684		/*
685		 * Hold preempt off so that we don't get preempted and have the
686		 * wakee busy-wait until we're scheduled back on.
687		 */
688		preempt_disable();
689	}
690	q->status = IN_WAKEUP;
691	q->pid = error;
692
693	list_add_tail(&q->list, pt);
694}
695
696/**
697 * wake_up_sem_queue_do - do the actual wake-up
698 * @pt: list of tasks to be woken up
699 *
700 * Do the actual wake-up.
701 * The function is called without any locks held, thus the semaphore array
702 * could be destroyed already and the tasks can disappear as soon as the
703 * status is set to the actual return code.
704 */
705static void wake_up_sem_queue_do(struct list_head *pt)
706{
707	struct sem_queue *q, *t;
708	int did_something;
709
710	did_something = !list_empty(pt);
711	list_for_each_entry_safe(q, t, pt, list) {
712		wake_up_process(q->sleeper);
713		/* q can disappear immediately after writing q->status. */
714		smp_wmb();
715		q->status = q->pid;
716	}
717	if (did_something)
718		preempt_enable();
719}
720
721static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
722{
723	list_del(&q->list);
724	if (q->nsops > 1)
725		sma->complex_count--;
726}
727
728/** check_restart(sma, q)
729 * @sma: semaphore array
730 * @q: the operation that just completed
731 *
732 * update_queue is O(N^2) when it restarts scanning the whole queue of
733 * waiting operations. Therefore this function checks if the restart is
734 * really necessary. It is called after a previously waiting operation
735 * modified the array.
736 * Note that wait-for-zero operations are handled without restart.
737 */
738static int check_restart(struct sem_array *sma, struct sem_queue *q)
739{
740	/* pending complex alter operations are too difficult to analyse */
741	if (!list_empty(&sma->pending_alter))
742		return 1;
743
744	/* we were a sleeping complex operation. Too difficult */
745	if (q->nsops > 1)
746		return 1;
747
748	/* It is impossible that someone waits for the new value:
749	 * - complex operations always restart.
750	 * - wait-for-zero are handled seperately.
751	 * - q is a previously sleeping simple operation that
752	 *   altered the array. It must be a decrement, because
753	 *   simple increments never sleep.
754	 * - If there are older (higher priority) decrements
755	 *   in the queue, then they have observed the original
756	 *   semval value and couldn't proceed. The operation
757	 *   decremented to value - thus they won't proceed either.
758	 */
759	return 0;
760}
761
762/**
763 * wake_const_ops - wake up non-alter tasks
764 * @sma: semaphore array.
765 * @semnum: semaphore that was modified.
766 * @pt: list head for the tasks that must be woken up.
767 *
768 * wake_const_ops must be called after a semaphore in a semaphore array
769 * was set to 0. If complex const operations are pending, wake_const_ops must
770 * be called with semnum = -1, as well as with the number of each modified
771 * semaphore.
772 * The tasks that must be woken up are added to @pt. The return code
773 * is stored in q->pid.
774 * The function returns 1 if at least one operation was completed successfully.
775 */
776static int wake_const_ops(struct sem_array *sma, int semnum,
777				struct list_head *pt)
778{
779	struct sem_queue *q;
780	struct list_head *walk;
781	struct list_head *pending_list;
782	int semop_completed = 0;
783
784	if (semnum == -1)
785		pending_list = &sma->pending_const;
786	else
787		pending_list = &sma->sem_base[semnum].pending_const;
788
789	walk = pending_list->next;
790	while (walk != pending_list) {
791		int error;
792
793		q = container_of(walk, struct sem_queue, list);
794		walk = walk->next;
795
796		error = perform_atomic_semop(sma, q);
797
798		if (error <= 0) {
799			/* operation completed, remove from queue & wakeup */
800
801			unlink_queue(sma, q);
802
803			wake_up_sem_queue_prepare(pt, q, error);
804			if (error == 0)
805				semop_completed = 1;
806		}
807	}
808	return semop_completed;
809}
810
811/**
812 * do_smart_wakeup_zero - wakeup all wait for zero tasks
813 * @sma: semaphore array
814 * @sops: operations that were performed
815 * @nsops: number of operations
816 * @pt: list head of the tasks that must be woken up.
817 *
818 * Checks all required queue for wait-for-zero operations, based
819 * on the actual changes that were performed on the semaphore array.
820 * The function returns 1 if at least one operation was completed successfully.
821 */
822static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
823					int nsops, struct list_head *pt)
824{
825	int i;
826	int semop_completed = 0;
827	int got_zero = 0;
828
829	/* first: the per-semaphore queues, if known */
830	if (sops) {
831		for (i = 0; i < nsops; i++) {
832			int num = sops[i].sem_num;
833
834			if (sma->sem_base[num].semval == 0) {
835				got_zero = 1;
836				semop_completed |= wake_const_ops(sma, num, pt);
837			}
838		}
839	} else {
840		/*
841		 * No sops means modified semaphores not known.
842		 * Assume all were changed.
843		 */
844		for (i = 0; i < sma->sem_nsems; i++) {
845			if (sma->sem_base[i].semval == 0) {
846				got_zero = 1;
847				semop_completed |= wake_const_ops(sma, i, pt);
848			}
849		}
850	}
851	/*
852	 * If one of the modified semaphores got 0,
853	 * then check the global queue, too.
854	 */
855	if (got_zero)
856		semop_completed |= wake_const_ops(sma, -1, pt);
857
858	return semop_completed;
859}
860
861
862/**
863 * update_queue - look for tasks that can be completed.
864 * @sma: semaphore array.
865 * @semnum: semaphore that was modified.
866 * @pt: list head for the tasks that must be woken up.
867 *
868 * update_queue must be called after a semaphore in a semaphore array
869 * was modified. If multiple semaphores were modified, update_queue must
870 * be called with semnum = -1, as well as with the number of each modified
871 * semaphore.
872 * The tasks that must be woken up are added to @pt. The return code
873 * is stored in q->pid.
874 * The function internally checks if const operations can now succeed.
875 *
876 * The function return 1 if at least one semop was completed successfully.
877 */
878static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
879{
880	struct sem_queue *q;
881	struct list_head *walk;
882	struct list_head *pending_list;
883	int semop_completed = 0;
884
885	if (semnum == -1)
886		pending_list = &sma->pending_alter;
887	else
888		pending_list = &sma->sem_base[semnum].pending_alter;
889
890again:
891	walk = pending_list->next;
892	while (walk != pending_list) {
893		int error, restart;
894
895		q = container_of(walk, struct sem_queue, list);
896		walk = walk->next;
897
898		/* If we are scanning the single sop, per-semaphore list of
899		 * one semaphore and that semaphore is 0, then it is not
900		 * necessary to scan further: simple increments
901		 * that affect only one entry succeed immediately and cannot
902		 * be in the  per semaphore pending queue, and decrements
903		 * cannot be successful if the value is already 0.
904		 */
905		if (semnum != -1 && sma->sem_base[semnum].semval == 0)
906			break;
907
908		error = perform_atomic_semop(sma, q);
909
910		/* Does q->sleeper still need to sleep? */
911		if (error > 0)
912			continue;
913
914		unlink_queue(sma, q);
915
916		if (error) {
917			restart = 0;
918		} else {
919			semop_completed = 1;
920			do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
921			restart = check_restart(sma, q);
922		}
923
924		wake_up_sem_queue_prepare(pt, q, error);
925		if (restart)
926			goto again;
927	}
928	return semop_completed;
929}
930
931/**
932 * set_semotime - set sem_otime
933 * @sma: semaphore array
934 * @sops: operations that modified the array, may be NULL
935 *
936 * sem_otime is replicated to avoid cache line trashing.
937 * This function sets one instance to the current time.
938 */
939static void set_semotime(struct sem_array *sma, struct sembuf *sops)
940{
941	if (sops == NULL) {
942		sma->sem_base[0].sem_otime = get_seconds();
943	} else {
944		sma->sem_base[sops[0].sem_num].sem_otime =
945							get_seconds();
946	}
947}
948
949/**
950 * do_smart_update - optimized update_queue
951 * @sma: semaphore array
952 * @sops: operations that were performed
953 * @nsops: number of operations
954 * @otime: force setting otime
955 * @pt: list head of the tasks that must be woken up.
956 *
957 * do_smart_update() does the required calls to update_queue and wakeup_zero,
958 * based on the actual changes that were performed on the semaphore array.
959 * Note that the function does not do the actual wake-up: the caller is
960 * responsible for calling wake_up_sem_queue_do(@pt).
961 * It is safe to perform this call after dropping all locks.
962 */
963static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
964			int otime, struct list_head *pt)
965{
966	int i;
967
968	otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
969
970	if (!list_empty(&sma->pending_alter)) {
971		/* semaphore array uses the global queue - just process it. */
972		otime |= update_queue(sma, -1, pt);
973	} else {
974		if (!sops) {
975			/*
976			 * No sops, thus the modified semaphores are not
977			 * known. Check all.
978			 */
979			for (i = 0; i < sma->sem_nsems; i++)
980				otime |= update_queue(sma, i, pt);
981		} else {
982			/*
983			 * Check the semaphores that were increased:
984			 * - No complex ops, thus all sleeping ops are
985			 *   decrease.
986			 * - if we decreased the value, then any sleeping
987			 *   semaphore ops wont be able to run: If the
988			 *   previous value was too small, then the new
989			 *   value will be too small, too.
990			 */
991			for (i = 0; i < nsops; i++) {
992				if (sops[i].sem_op > 0) {
993					otime |= update_queue(sma,
994							sops[i].sem_num, pt);
995				}
996			}
997		}
998	}
999	if (otime)
1000		set_semotime(sma, sops);
1001}
1002
1003/*
1004 * check_qop: Test if a queued operation sleeps on the semaphore semnum
1005 */
1006static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1007			bool count_zero)
1008{
1009	struct sembuf *sop = q->blocking;
1010
1011	/*
1012	 * Linux always (since 0.99.10) reported a task as sleeping on all
1013	 * semaphores. This violates SUS, therefore it was changed to the
1014	 * standard compliant behavior.
1015	 * Give the administrators a chance to notice that an application
1016	 * might misbehave because it relies on the Linux behavior.
1017	 */
1018	pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1019			"The task %s (%d) triggered the difference, watch for misbehavior.\n",
1020			current->comm, task_pid_nr(current));
1021
1022	if (sop->sem_num != semnum)
1023		return 0;
1024
1025	if (count_zero && sop->sem_op == 0)
1026		return 1;
1027	if (!count_zero && sop->sem_op < 0)
1028		return 1;
1029
1030	return 0;
1031}
1032
1033/* The following counts are associated to each semaphore:
1034 *   semncnt        number of tasks waiting on semval being nonzero
1035 *   semzcnt        number of tasks waiting on semval being zero
1036 *
1037 * Per definition, a task waits only on the semaphore of the first semop
1038 * that cannot proceed, even if additional operation would block, too.
1039 */
1040static int count_semcnt(struct sem_array *sma, ushort semnum,
1041			bool count_zero)
1042{
1043	struct list_head *l;
1044	struct sem_queue *q;
1045	int semcnt;
1046
1047	semcnt = 0;
1048	/* First: check the simple operations. They are easy to evaluate */
1049	if (count_zero)
1050		l = &sma->sem_base[semnum].pending_const;
1051	else
1052		l = &sma->sem_base[semnum].pending_alter;
1053
1054	list_for_each_entry(q, l, list) {
1055		/* all task on a per-semaphore list sleep on exactly
1056		 * that semaphore
1057		 */
1058		semcnt++;
1059	}
1060
1061	/* Then: check the complex operations. */
1062	list_for_each_entry(q, &sma->pending_alter, list) {
1063		semcnt += check_qop(sma, semnum, q, count_zero);
1064	}
1065	if (count_zero) {
1066		list_for_each_entry(q, &sma->pending_const, list) {
1067			semcnt += check_qop(sma, semnum, q, count_zero);
1068		}
1069	}
1070	return semcnt;
1071}
1072
1073/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1074 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1075 * remains locked on exit.
1076 */
1077static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1078{
1079	struct sem_undo *un, *tu;
1080	struct sem_queue *q, *tq;
1081	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1082	struct list_head tasks;
1083	int i;
1084
1085	/* Free the existing undo structures for this semaphore set.  */
1086	ipc_assert_locked_object(&sma->sem_perm);
1087	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1088		list_del(&un->list_id);
1089		spin_lock(&un->ulp->lock);
1090		un->semid = -1;
1091		list_del_rcu(&un->list_proc);
1092		spin_unlock(&un->ulp->lock);
1093		kfree_rcu(un, rcu);
1094	}
1095
1096	/* Wake up all pending processes and let them fail with EIDRM. */
1097	INIT_LIST_HEAD(&tasks);
1098	list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1099		unlink_queue(sma, q);
1100		wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1101	}
1102
1103	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1104		unlink_queue(sma, q);
1105		wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1106	}
1107	for (i = 0; i < sma->sem_nsems; i++) {
1108		struct sem *sem = sma->sem_base + i;
1109		list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1110			unlink_queue(sma, q);
1111			wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1112		}
1113		list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1114			unlink_queue(sma, q);
1115			wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1116		}
1117	}
1118
1119	/* Remove the semaphore set from the IDR */
1120	sem_rmid(ns, sma);
1121	sem_unlock(sma, -1);
1122	rcu_read_unlock();
1123
1124	wake_up_sem_queue_do(&tasks);
1125	ns->used_sems -= sma->sem_nsems;
1126	ipc_rcu_putref(sma, sem_rcu_free);
1127}
1128
1129static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1130{
1131	switch (version) {
1132	case IPC_64:
1133		return copy_to_user(buf, in, sizeof(*in));
1134	case IPC_OLD:
1135	    {
1136		struct semid_ds out;
1137
1138		memset(&out, 0, sizeof(out));
1139
1140		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1141
1142		out.sem_otime	= in->sem_otime;
1143		out.sem_ctime	= in->sem_ctime;
1144		out.sem_nsems	= in->sem_nsems;
1145
1146		return copy_to_user(buf, &out, sizeof(out));
1147	    }
1148	default:
1149		return -EINVAL;
1150	}
1151}
1152
1153static time_t get_semotime(struct sem_array *sma)
1154{
1155	int i;
1156	time_t res;
1157
1158	res = sma->sem_base[0].sem_otime;
1159	for (i = 1; i < sma->sem_nsems; i++) {
1160		time_t to = sma->sem_base[i].sem_otime;
1161
1162		if (to > res)
1163			res = to;
1164	}
1165	return res;
1166}
1167
1168static int semctl_nolock(struct ipc_namespace *ns, int semid,
1169			 int cmd, int version, void __user *p)
1170{
1171	int err;
1172	struct sem_array *sma;
1173
1174	switch (cmd) {
1175	case IPC_INFO:
1176	case SEM_INFO:
1177	{
1178		struct seminfo seminfo;
1179		int max_id;
1180
1181		err = security_sem_semctl(NULL, cmd);
1182		if (err)
1183			return err;
1184
1185		memset(&seminfo, 0, sizeof(seminfo));
1186		seminfo.semmni = ns->sc_semmni;
1187		seminfo.semmns = ns->sc_semmns;
1188		seminfo.semmsl = ns->sc_semmsl;
1189		seminfo.semopm = ns->sc_semopm;
1190		seminfo.semvmx = SEMVMX;
1191		seminfo.semmnu = SEMMNU;
1192		seminfo.semmap = SEMMAP;
1193		seminfo.semume = SEMUME;
1194		down_read(&sem_ids(ns).rwsem);
1195		if (cmd == SEM_INFO) {
1196			seminfo.semusz = sem_ids(ns).in_use;
1197			seminfo.semaem = ns->used_sems;
1198		} else {
1199			seminfo.semusz = SEMUSZ;
1200			seminfo.semaem = SEMAEM;
1201		}
1202		max_id = ipc_get_maxid(&sem_ids(ns));
1203		up_read(&sem_ids(ns).rwsem);
1204		if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1205			return -EFAULT;
1206		return (max_id < 0) ? 0 : max_id;
1207	}
1208	case IPC_STAT:
1209	case SEM_STAT:
1210	{
1211		struct semid64_ds tbuf;
1212		int id = 0;
1213
1214		memset(&tbuf, 0, sizeof(tbuf));
1215
1216		rcu_read_lock();
1217		if (cmd == SEM_STAT) {
1218			sma = sem_obtain_object(ns, semid);
1219			if (IS_ERR(sma)) {
1220				err = PTR_ERR(sma);
1221				goto out_unlock;
1222			}
1223			id = sma->sem_perm.id;
1224		} else {
1225			sma = sem_obtain_object_check(ns, semid);
1226			if (IS_ERR(sma)) {
1227				err = PTR_ERR(sma);
1228				goto out_unlock;
1229			}
1230		}
1231
1232		err = -EACCES;
1233		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1234			goto out_unlock;
1235
1236		err = security_sem_semctl(sma, cmd);
1237		if (err)
1238			goto out_unlock;
1239
1240		kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1241		tbuf.sem_otime = get_semotime(sma);
1242		tbuf.sem_ctime = sma->sem_ctime;
1243		tbuf.sem_nsems = sma->sem_nsems;
1244		rcu_read_unlock();
1245		if (copy_semid_to_user(p, &tbuf, version))
1246			return -EFAULT;
1247		return id;
1248	}
1249	default:
1250		return -EINVAL;
1251	}
1252out_unlock:
1253	rcu_read_unlock();
1254	return err;
1255}
1256
1257static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1258		unsigned long arg)
1259{
1260	struct sem_undo *un;
1261	struct sem_array *sma;
1262	struct sem *curr;
1263	int err;
1264	struct list_head tasks;
1265	int val;
1266#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1267	/* big-endian 64bit */
1268	val = arg >> 32;
1269#else
1270	/* 32bit or little-endian 64bit */
1271	val = arg;
1272#endif
1273
1274	if (val > SEMVMX || val < 0)
1275		return -ERANGE;
1276
1277	INIT_LIST_HEAD(&tasks);
1278
1279	rcu_read_lock();
1280	sma = sem_obtain_object_check(ns, semid);
1281	if (IS_ERR(sma)) {
1282		rcu_read_unlock();
1283		return PTR_ERR(sma);
1284	}
1285
1286	if (semnum < 0 || semnum >= sma->sem_nsems) {
1287		rcu_read_unlock();
1288		return -EINVAL;
1289	}
1290
1291
1292	if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1293		rcu_read_unlock();
1294		return -EACCES;
1295	}
1296
1297	err = security_sem_semctl(sma, SETVAL);
1298	if (err) {
1299		rcu_read_unlock();
1300		return -EACCES;
1301	}
1302
1303	sem_lock(sma, NULL, -1);
1304
1305	if (!ipc_valid_object(&sma->sem_perm)) {
1306		sem_unlock(sma, -1);
1307		rcu_read_unlock();
1308		return -EIDRM;
1309	}
1310
1311	curr = &sma->sem_base[semnum];
1312
1313	ipc_assert_locked_object(&sma->sem_perm);
1314	list_for_each_entry(un, &sma->list_id, list_id)
1315		un->semadj[semnum] = 0;
1316
1317	curr->semval = val;
1318	curr->sempid = task_tgid_vnr(current);
1319	sma->sem_ctime = get_seconds();
1320	/* maybe some queued-up processes were waiting for this */
1321	do_smart_update(sma, NULL, 0, 0, &tasks);
1322	sem_unlock(sma, -1);
1323	rcu_read_unlock();
1324	wake_up_sem_queue_do(&tasks);
1325	return 0;
1326}
1327
1328static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1329		int cmd, void __user *p)
1330{
1331	struct sem_array *sma;
1332	struct sem *curr;
1333	int err, nsems;
1334	ushort fast_sem_io[SEMMSL_FAST];
1335	ushort *sem_io = fast_sem_io;
1336	struct list_head tasks;
1337
1338	INIT_LIST_HEAD(&tasks);
1339
1340	rcu_read_lock();
1341	sma = sem_obtain_object_check(ns, semid);
1342	if (IS_ERR(sma)) {
1343		rcu_read_unlock();
1344		return PTR_ERR(sma);
1345	}
1346
1347	nsems = sma->sem_nsems;
1348
1349	err = -EACCES;
1350	if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1351		goto out_rcu_wakeup;
1352
1353	err = security_sem_semctl(sma, cmd);
1354	if (err)
1355		goto out_rcu_wakeup;
1356
1357	err = -EACCES;
1358	switch (cmd) {
1359	case GETALL:
1360	{
1361		ushort __user *array = p;
1362		int i;
1363
1364		sem_lock(sma, NULL, -1);
1365		if (!ipc_valid_object(&sma->sem_perm)) {
1366			err = -EIDRM;
1367			goto out_unlock;
1368		}
1369		if (nsems > SEMMSL_FAST) {
1370			if (!ipc_rcu_getref(sma)) {
1371				err = -EIDRM;
1372				goto out_unlock;
1373			}
1374			sem_unlock(sma, -1);
1375			rcu_read_unlock();
1376			sem_io = ipc_alloc(sizeof(ushort)*nsems);
1377			if (sem_io == NULL) {
1378				ipc_rcu_putref(sma, ipc_rcu_free);
1379				return -ENOMEM;
1380			}
1381
1382			rcu_read_lock();
1383			sem_lock_and_putref(sma);
1384			if (!ipc_valid_object(&sma->sem_perm)) {
1385				err = -EIDRM;
1386				goto out_unlock;
1387			}
1388		}
1389		for (i = 0; i < sma->sem_nsems; i++)
1390			sem_io[i] = sma->sem_base[i].semval;
1391		sem_unlock(sma, -1);
1392		rcu_read_unlock();
1393		err = 0;
1394		if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1395			err = -EFAULT;
1396		goto out_free;
1397	}
1398	case SETALL:
1399	{
1400		int i;
1401		struct sem_undo *un;
1402
1403		if (!ipc_rcu_getref(sma)) {
1404			err = -EIDRM;
1405			goto out_rcu_wakeup;
1406		}
1407		rcu_read_unlock();
1408
1409		if (nsems > SEMMSL_FAST) {
1410			sem_io = ipc_alloc(sizeof(ushort)*nsems);
1411			if (sem_io == NULL) {
1412				ipc_rcu_putref(sma, ipc_rcu_free);
1413				return -ENOMEM;
1414			}
1415		}
1416
1417		if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1418			ipc_rcu_putref(sma, ipc_rcu_free);
1419			err = -EFAULT;
1420			goto out_free;
1421		}
1422
1423		for (i = 0; i < nsems; i++) {
1424			if (sem_io[i] > SEMVMX) {
1425				ipc_rcu_putref(sma, ipc_rcu_free);
1426				err = -ERANGE;
1427				goto out_free;
1428			}
1429		}
1430		rcu_read_lock();
1431		sem_lock_and_putref(sma);
1432		if (!ipc_valid_object(&sma->sem_perm)) {
1433			err = -EIDRM;
1434			goto out_unlock;
1435		}
1436
1437		for (i = 0; i < nsems; i++)
1438			sma->sem_base[i].semval = sem_io[i];
1439
1440		ipc_assert_locked_object(&sma->sem_perm);
1441		list_for_each_entry(un, &sma->list_id, list_id) {
1442			for (i = 0; i < nsems; i++)
1443				un->semadj[i] = 0;
1444		}
1445		sma->sem_ctime = get_seconds();
1446		/* maybe some queued-up processes were waiting for this */
1447		do_smart_update(sma, NULL, 0, 0, &tasks);
1448		err = 0;
1449		goto out_unlock;
1450	}
1451	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1452	}
1453	err = -EINVAL;
1454	if (semnum < 0 || semnum >= nsems)
1455		goto out_rcu_wakeup;
1456
1457	sem_lock(sma, NULL, -1);
1458	if (!ipc_valid_object(&sma->sem_perm)) {
1459		err = -EIDRM;
1460		goto out_unlock;
1461	}
1462	curr = &sma->sem_base[semnum];
1463
1464	switch (cmd) {
1465	case GETVAL:
1466		err = curr->semval;
1467		goto out_unlock;
1468	case GETPID:
1469		err = curr->sempid;
1470		goto out_unlock;
1471	case GETNCNT:
1472		err = count_semcnt(sma, semnum, 0);
1473		goto out_unlock;
1474	case GETZCNT:
1475		err = count_semcnt(sma, semnum, 1);
1476		goto out_unlock;
1477	}
1478
1479out_unlock:
1480	sem_unlock(sma, -1);
1481out_rcu_wakeup:
1482	rcu_read_unlock();
1483	wake_up_sem_queue_do(&tasks);
1484out_free:
1485	if (sem_io != fast_sem_io)
1486		ipc_free(sem_io, sizeof(ushort)*nsems);
1487	return err;
1488}
1489
1490static inline unsigned long
1491copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1492{
1493	switch (version) {
1494	case IPC_64:
1495		if (copy_from_user(out, buf, sizeof(*out)))
1496			return -EFAULT;
1497		return 0;
1498	case IPC_OLD:
1499	    {
1500		struct semid_ds tbuf_old;
1501
1502		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1503			return -EFAULT;
1504
1505		out->sem_perm.uid	= tbuf_old.sem_perm.uid;
1506		out->sem_perm.gid	= tbuf_old.sem_perm.gid;
1507		out->sem_perm.mode	= tbuf_old.sem_perm.mode;
1508
1509		return 0;
1510	    }
1511	default:
1512		return -EINVAL;
1513	}
1514}
1515
1516/*
1517 * This function handles some semctl commands which require the rwsem
1518 * to be held in write mode.
1519 * NOTE: no locks must be held, the rwsem is taken inside this function.
1520 */
1521static int semctl_down(struct ipc_namespace *ns, int semid,
1522		       int cmd, int version, void __user *p)
1523{
1524	struct sem_array *sma;
1525	int err;
1526	struct semid64_ds semid64;
1527	struct kern_ipc_perm *ipcp;
1528
1529	if (cmd == IPC_SET) {
1530		if (copy_semid_from_user(&semid64, p, version))
1531			return -EFAULT;
1532	}
1533
1534	down_write(&sem_ids(ns).rwsem);
1535	rcu_read_lock();
1536
1537	ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1538				      &semid64.sem_perm, 0);
1539	if (IS_ERR(ipcp)) {
1540		err = PTR_ERR(ipcp);
1541		goto out_unlock1;
1542	}
1543
1544	sma = container_of(ipcp, struct sem_array, sem_perm);
1545
1546	err = security_sem_semctl(sma, cmd);
1547	if (err)
1548		goto out_unlock1;
1549
1550	switch (cmd) {
1551	case IPC_RMID:
1552		sem_lock(sma, NULL, -1);
1553		/* freeary unlocks the ipc object and rcu */
1554		freeary(ns, ipcp);
1555		goto out_up;
1556	case IPC_SET:
1557		sem_lock(sma, NULL, -1);
1558		err = ipc_update_perm(&semid64.sem_perm, ipcp);
1559		if (err)
1560			goto out_unlock0;
1561		sma->sem_ctime = get_seconds();
1562		break;
1563	default:
1564		err = -EINVAL;
1565		goto out_unlock1;
1566	}
1567
1568out_unlock0:
1569	sem_unlock(sma, -1);
1570out_unlock1:
1571	rcu_read_unlock();
1572out_up:
1573	up_write(&sem_ids(ns).rwsem);
1574	return err;
1575}
1576
1577SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1578{
1579	int version;
1580	struct ipc_namespace *ns;
1581	void __user *p = (void __user *)arg;
1582
1583	if (semid < 0)
1584		return -EINVAL;
1585
1586	version = ipc_parse_version(&cmd);
1587	ns = current->nsproxy->ipc_ns;
1588
1589	switch (cmd) {
1590	case IPC_INFO:
1591	case SEM_INFO:
1592	case IPC_STAT:
1593	case SEM_STAT:
1594		return semctl_nolock(ns, semid, cmd, version, p);
1595	case GETALL:
1596	case GETVAL:
1597	case GETPID:
1598	case GETNCNT:
1599	case GETZCNT:
1600	case SETALL:
1601		return semctl_main(ns, semid, semnum, cmd, p);
1602	case SETVAL:
1603		return semctl_setval(ns, semid, semnum, arg);
1604	case IPC_RMID:
1605	case IPC_SET:
1606		return semctl_down(ns, semid, cmd, version, p);
1607	default:
1608		return -EINVAL;
1609	}
1610}
1611
1612/* If the task doesn't already have a undo_list, then allocate one
1613 * here.  We guarantee there is only one thread using this undo list,
1614 * and current is THE ONE
1615 *
1616 * If this allocation and assignment succeeds, but later
1617 * portions of this code fail, there is no need to free the sem_undo_list.
1618 * Just let it stay associated with the task, and it'll be freed later
1619 * at exit time.
1620 *
1621 * This can block, so callers must hold no locks.
1622 */
1623static inline int get_undo_list(struct sem_undo_list **undo_listp)
1624{
1625	struct sem_undo_list *undo_list;
1626
1627	undo_list = current->sysvsem.undo_list;
1628	if (!undo_list) {
1629		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1630		if (undo_list == NULL)
1631			return -ENOMEM;
1632		spin_lock_init(&undo_list->lock);
1633		atomic_set(&undo_list->refcnt, 1);
1634		INIT_LIST_HEAD(&undo_list->list_proc);
1635
1636		current->sysvsem.undo_list = undo_list;
1637	}
1638	*undo_listp = undo_list;
1639	return 0;
1640}
1641
1642static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1643{
1644	struct sem_undo *un;
1645
1646	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1647		if (un->semid == semid)
1648			return un;
1649	}
1650	return NULL;
1651}
1652
1653static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1654{
1655	struct sem_undo *un;
1656
1657	assert_spin_locked(&ulp->lock);
1658
1659	un = __lookup_undo(ulp, semid);
1660	if (un) {
1661		list_del_rcu(&un->list_proc);
1662		list_add_rcu(&un->list_proc, &ulp->list_proc);
1663	}
1664	return un;
1665}
1666
1667/**
1668 * find_alloc_undo - lookup (and if not present create) undo array
1669 * @ns: namespace
1670 * @semid: semaphore array id
1671 *
1672 * The function looks up (and if not present creates) the undo structure.
1673 * The size of the undo structure depends on the size of the semaphore
1674 * array, thus the alloc path is not that straightforward.
1675 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1676 * performs a rcu_read_lock().
1677 */
1678static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1679{
1680	struct sem_array *sma;
1681	struct sem_undo_list *ulp;
1682	struct sem_undo *un, *new;
1683	int nsems, error;
1684
1685	error = get_undo_list(&ulp);
1686	if (error)
1687		return ERR_PTR(error);
1688
1689	rcu_read_lock();
1690	spin_lock(&ulp->lock);
1691	un = lookup_undo(ulp, semid);
1692	spin_unlock(&ulp->lock);
1693	if (likely(un != NULL))
1694		goto out;
1695
1696	/* no undo structure around - allocate one. */
1697	/* step 1: figure out the size of the semaphore array */
1698	sma = sem_obtain_object_check(ns, semid);
1699	if (IS_ERR(sma)) {
1700		rcu_read_unlock();
1701		return ERR_CAST(sma);
1702	}
1703
1704	nsems = sma->sem_nsems;
1705	if (!ipc_rcu_getref(sma)) {
1706		rcu_read_unlock();
1707		un = ERR_PTR(-EIDRM);
1708		goto out;
1709	}
1710	rcu_read_unlock();
1711
1712	/* step 2: allocate new undo structure */
1713	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1714	if (!new) {
1715		ipc_rcu_putref(sma, ipc_rcu_free);
1716		return ERR_PTR(-ENOMEM);
1717	}
1718
1719	/* step 3: Acquire the lock on semaphore array */
1720	rcu_read_lock();
1721	sem_lock_and_putref(sma);
1722	if (!ipc_valid_object(&sma->sem_perm)) {
1723		sem_unlock(sma, -1);
1724		rcu_read_unlock();
1725		kfree(new);
1726		un = ERR_PTR(-EIDRM);
1727		goto out;
1728	}
1729	spin_lock(&ulp->lock);
1730
1731	/*
1732	 * step 4: check for races: did someone else allocate the undo struct?
1733	 */
1734	un = lookup_undo(ulp, semid);
1735	if (un) {
1736		kfree(new);
1737		goto success;
1738	}
1739	/* step 5: initialize & link new undo structure */
1740	new->semadj = (short *) &new[1];
1741	new->ulp = ulp;
1742	new->semid = semid;
1743	assert_spin_locked(&ulp->lock);
1744	list_add_rcu(&new->list_proc, &ulp->list_proc);
1745	ipc_assert_locked_object(&sma->sem_perm);
1746	list_add(&new->list_id, &sma->list_id);
1747	un = new;
1748
1749success:
1750	spin_unlock(&ulp->lock);
1751	sem_unlock(sma, -1);
1752out:
1753	return un;
1754}
1755
1756
1757/**
1758 * get_queue_result - retrieve the result code from sem_queue
1759 * @q: Pointer to queue structure
1760 *
1761 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1762 * q->status, then we must loop until the value is replaced with the final
1763 * value: This may happen if a task is woken up by an unrelated event (e.g.
1764 * signal) and in parallel the task is woken up by another task because it got
1765 * the requested semaphores.
1766 *
1767 * The function can be called with or without holding the semaphore spinlock.
1768 */
1769static int get_queue_result(struct sem_queue *q)
1770{
1771	int error;
1772
1773	error = q->status;
1774	while (unlikely(error == IN_WAKEUP)) {
1775		cpu_relax();
1776		error = q->status;
1777	}
1778
1779	return error;
1780}
1781
1782SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1783		unsigned, nsops, const struct timespec __user *, timeout)
1784{
1785	int error = -EINVAL;
1786	struct sem_array *sma;
1787	struct sembuf fast_sops[SEMOPM_FAST];
1788	struct sembuf *sops = fast_sops, *sop;
1789	struct sem_undo *un;
1790	int undos = 0, alter = 0, max, locknum;
1791	struct sem_queue queue;
1792	unsigned long jiffies_left = 0;
1793	struct ipc_namespace *ns;
1794	struct list_head tasks;
1795
1796	ns = current->nsproxy->ipc_ns;
1797
1798	if (nsops < 1 || semid < 0)
1799		return -EINVAL;
1800	if (nsops > ns->sc_semopm)
1801		return -E2BIG;
1802	if (nsops > SEMOPM_FAST) {
1803		sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
1804		if (sops == NULL)
1805			return -ENOMEM;
1806	}
1807	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
1808		error =  -EFAULT;
1809		goto out_free;
1810	}
1811	if (timeout) {
1812		struct timespec _timeout;
1813		if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1814			error = -EFAULT;
1815			goto out_free;
1816		}
1817		if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1818			_timeout.tv_nsec >= 1000000000L) {
1819			error = -EINVAL;
1820			goto out_free;
1821		}
1822		jiffies_left = timespec_to_jiffies(&_timeout);
1823	}
1824	max = 0;
1825	for (sop = sops; sop < sops + nsops; sop++) {
1826		if (sop->sem_num >= max)
1827			max = sop->sem_num;
1828		if (sop->sem_flg & SEM_UNDO)
1829			undos = 1;
1830		if (sop->sem_op != 0)
1831			alter = 1;
1832	}
1833
1834	INIT_LIST_HEAD(&tasks);
1835
1836	if (undos) {
1837		/* On success, find_alloc_undo takes the rcu_read_lock */
1838		un = find_alloc_undo(ns, semid);
1839		if (IS_ERR(un)) {
1840			error = PTR_ERR(un);
1841			goto out_free;
1842		}
1843	} else {
1844		un = NULL;
1845		rcu_read_lock();
1846	}
1847
1848	sma = sem_obtain_object_check(ns, semid);
1849	if (IS_ERR(sma)) {
1850		rcu_read_unlock();
1851		error = PTR_ERR(sma);
1852		goto out_free;
1853	}
1854
1855	error = -EFBIG;
1856	if (max >= sma->sem_nsems)
1857		goto out_rcu_wakeup;
1858
1859	error = -EACCES;
1860	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1861		goto out_rcu_wakeup;
1862
1863	error = security_sem_semop(sma, sops, nsops, alter);
1864	if (error)
1865		goto out_rcu_wakeup;
1866
1867	error = -EIDRM;
1868	locknum = sem_lock(sma, sops, nsops);
1869	/*
1870	 * We eventually might perform the following check in a lockless
1871	 * fashion, considering ipc_valid_object() locking constraints.
1872	 * If nsops == 1 and there is no contention for sem_perm.lock, then
1873	 * only a per-semaphore lock is held and it's OK to proceed with the
1874	 * check below. More details on the fine grained locking scheme
1875	 * entangled here and why it's RMID race safe on comments at sem_lock()
1876	 */
1877	if (!ipc_valid_object(&sma->sem_perm))
1878		goto out_unlock_free;
1879	/*
1880	 * semid identifiers are not unique - find_alloc_undo may have
1881	 * allocated an undo structure, it was invalidated by an RMID
1882	 * and now a new array with received the same id. Check and fail.
1883	 * This case can be detected checking un->semid. The existence of
1884	 * "un" itself is guaranteed by rcu.
1885	 */
1886	if (un && un->semid == -1)
1887		goto out_unlock_free;
1888
1889	queue.sops = sops;
1890	queue.nsops = nsops;
1891	queue.undo = un;
1892	queue.pid = task_tgid_vnr(current);
1893	queue.alter = alter;
1894
1895	error = perform_atomic_semop(sma, &queue);
1896	if (error == 0) {
1897		/* If the operation was successful, then do
1898		 * the required updates.
1899		 */
1900		if (alter)
1901			do_smart_update(sma, sops, nsops, 1, &tasks);
1902		else
1903			set_semotime(sma, sops);
1904	}
1905	if (error <= 0)
1906		goto out_unlock_free;
1907
1908	/* We need to sleep on this operation, so we put the current
1909	 * task into the pending queue and go to sleep.
1910	 */
1911
1912	if (nsops == 1) {
1913		struct sem *curr;
1914		curr = &sma->sem_base[sops->sem_num];
1915
1916		if (alter) {
1917			if (sma->complex_count) {
1918				list_add_tail(&queue.list,
1919						&sma->pending_alter);
1920			} else {
1921
1922				list_add_tail(&queue.list,
1923						&curr->pending_alter);
1924			}
1925		} else {
1926			list_add_tail(&queue.list, &curr->pending_const);
1927		}
1928	} else {
1929		if (!sma->complex_count)
1930			merge_queues(sma);
1931
1932		if (alter)
1933			list_add_tail(&queue.list, &sma->pending_alter);
1934		else
1935			list_add_tail(&queue.list, &sma->pending_const);
1936
1937		sma->complex_count++;
1938	}
1939
1940	queue.status = -EINTR;
1941	queue.sleeper = current;
1942
1943sleep_again:
1944	current->state = TASK_INTERRUPTIBLE;
1945	sem_unlock(sma, locknum);
1946	rcu_read_unlock();
1947
1948	if (timeout)
1949		jiffies_left = schedule_timeout(jiffies_left);
1950	else
1951		schedule();
1952
1953	error = get_queue_result(&queue);
1954
1955	if (error != -EINTR) {
1956		/* fast path: update_queue already obtained all requested
1957		 * resources.
1958		 * Perform a smp_mb(): User space could assume that semop()
1959		 * is a memory barrier: Without the mb(), the cpu could
1960		 * speculatively read in user space stale data that was
1961		 * overwritten by the previous owner of the semaphore.
1962		 */
1963		smp_mb();
1964
1965		goto out_free;
1966	}
1967
1968	rcu_read_lock();
1969	sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1970
1971	/*
1972	 * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1973	 */
1974	error = get_queue_result(&queue);
1975
1976	/*
1977	 * Array removed? If yes, leave without sem_unlock().
1978	 */
1979	if (IS_ERR(sma)) {
1980		rcu_read_unlock();
1981		goto out_free;
1982	}
1983
1984
1985	/*
1986	 * If queue.status != -EINTR we are woken up by another process.
1987	 * Leave without unlink_queue(), but with sem_unlock().
1988	 */
1989	if (error != -EINTR)
1990		goto out_unlock_free;
1991
1992	/*
1993	 * If an interrupt occurred we have to clean up the queue
1994	 */
1995	if (timeout && jiffies_left == 0)
1996		error = -EAGAIN;
1997
1998	/*
1999	 * If the wakeup was spurious, just retry
2000	 */
2001	if (error == -EINTR && !signal_pending(current))
2002		goto sleep_again;
2003
2004	unlink_queue(sma, &queue);
2005
2006out_unlock_free:
2007	sem_unlock(sma, locknum);
2008out_rcu_wakeup:
2009	rcu_read_unlock();
2010	wake_up_sem_queue_do(&tasks);
2011out_free:
2012	if (sops != fast_sops)
2013		kfree(sops);
2014	return error;
2015}
2016
2017SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2018		unsigned, nsops)
2019{
2020	return sys_semtimedop(semid, tsops, nsops, NULL);
2021}
2022
2023/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2024 * parent and child tasks.
2025 */
2026
2027int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2028{
2029	struct sem_undo_list *undo_list;
2030	int error;
2031
2032	if (clone_flags & CLONE_SYSVSEM) {
2033		error = get_undo_list(&undo_list);
2034		if (error)
2035			return error;
2036		atomic_inc(&undo_list->refcnt);
2037		tsk->sysvsem.undo_list = undo_list;
2038	} else
2039		tsk->sysvsem.undo_list = NULL;
2040
2041	return 0;
2042}
2043
2044/*
2045 * add semadj values to semaphores, free undo structures.
2046 * undo structures are not freed when semaphore arrays are destroyed
2047 * so some of them may be out of date.
2048 * IMPLEMENTATION NOTE: There is some confusion over whether the
2049 * set of adjustments that needs to be done should be done in an atomic
2050 * manner or not. That is, if we are attempting to decrement the semval
2051 * should we queue up and wait until we can do so legally?
2052 * The original implementation attempted to do this (queue and wait).
2053 * The current implementation does not do so. The POSIX standard
2054 * and SVID should be consulted to determine what behavior is mandated.
2055 */
2056void exit_sem(struct task_struct *tsk)
2057{
2058	struct sem_undo_list *ulp;
2059
2060	ulp = tsk->sysvsem.undo_list;
2061	if (!ulp)
2062		return;
2063	tsk->sysvsem.undo_list = NULL;
2064
2065	if (!atomic_dec_and_test(&ulp->refcnt))
2066		return;
2067
2068	for (;;) {
2069		struct sem_array *sma;
2070		struct sem_undo *un;
2071		struct list_head tasks;
2072		int semid, i;
2073
2074		rcu_read_lock();
2075		un = list_entry_rcu(ulp->list_proc.next,
2076				    struct sem_undo, list_proc);
2077		if (&un->list_proc == &ulp->list_proc)
2078			semid = -1;
2079		 else
2080			semid = un->semid;
2081
2082		if (semid == -1) {
2083			rcu_read_unlock();
2084			break;
2085		}
2086
2087		sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
2088		/* exit_sem raced with IPC_RMID, nothing to do */
2089		if (IS_ERR(sma)) {
2090			rcu_read_unlock();
2091			continue;
2092		}
2093
2094		sem_lock(sma, NULL, -1);
2095		/* exit_sem raced with IPC_RMID, nothing to do */
2096		if (!ipc_valid_object(&sma->sem_perm)) {
2097			sem_unlock(sma, -1);
2098			rcu_read_unlock();
2099			continue;
2100		}
2101		un = __lookup_undo(ulp, semid);
2102		if (un == NULL) {
2103			/* exit_sem raced with IPC_RMID+semget() that created
2104			 * exactly the same semid. Nothing to do.
2105			 */
2106			sem_unlock(sma, -1);
2107			rcu_read_unlock();
2108			continue;
2109		}
2110
2111		/* remove un from the linked lists */
2112		ipc_assert_locked_object(&sma->sem_perm);
2113		list_del(&un->list_id);
2114
2115		spin_lock(&ulp->lock);
2116		list_del_rcu(&un->list_proc);
2117		spin_unlock(&ulp->lock);
2118
2119		/* perform adjustments registered in un */
2120		for (i = 0; i < sma->sem_nsems; i++) {
2121			struct sem *semaphore = &sma->sem_base[i];
2122			if (un->semadj[i]) {
2123				semaphore->semval += un->semadj[i];
2124				/*
2125				 * Range checks of the new semaphore value,
2126				 * not defined by sus:
2127				 * - Some unices ignore the undo entirely
2128				 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2129				 * - some cap the value (e.g. FreeBSD caps
2130				 *   at 0, but doesn't enforce SEMVMX)
2131				 *
2132				 * Linux caps the semaphore value, both at 0
2133				 * and at SEMVMX.
2134				 *
2135				 *	Manfred <manfred@colorfullife.com>
2136				 */
2137				if (semaphore->semval < 0)
2138					semaphore->semval = 0;
2139				if (semaphore->semval > SEMVMX)
2140					semaphore->semval = SEMVMX;
2141				semaphore->sempid = task_tgid_vnr(current);
2142			}
2143		}
2144		/* maybe some queued-up processes were waiting for this */
2145		INIT_LIST_HEAD(&tasks);
2146		do_smart_update(sma, NULL, 0, 1, &tasks);
2147		sem_unlock(sma, -1);
2148		rcu_read_unlock();
2149		wake_up_sem_queue_do(&tasks);
2150
2151		kfree_rcu(un, rcu);
2152	}
2153	kfree(ulp);
2154}
2155
2156#ifdef CONFIG_PROC_FS
2157static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2158{
2159	struct user_namespace *user_ns = seq_user_ns(s);
2160	struct sem_array *sma = it;
2161	time_t sem_otime;
2162
2163	/*
2164	 * The proc interface isn't aware of sem_lock(), it calls
2165	 * ipc_lock_object() directly (in sysvipc_find_ipc).
2166	 * In order to stay compatible with sem_lock(), we must wait until
2167	 * all simple semop() calls have left their critical regions.
2168	 */
2169	sem_wait_array(sma);
2170
2171	sem_otime = get_semotime(sma);
2172
2173	return seq_printf(s,
2174			  "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2175			  sma->sem_perm.key,
2176			  sma->sem_perm.id,
2177			  sma->sem_perm.mode,
2178			  sma->sem_nsems,
2179			  from_kuid_munged(user_ns, sma->sem_perm.uid),
2180			  from_kgid_munged(user_ns, sma->sem_perm.gid),
2181			  from_kuid_munged(user_ns, sma->sem_perm.cuid),
2182			  from_kgid_munged(user_ns, sma->sem_perm.cgid),
2183			  sem_otime,
2184			  sma->sem_ctime);
2185}
2186#endif
2187