sem.c revision ade9f91b
1/*
2 * linux/ipc/sem.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
5 *
6 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
7 *
8 * SMP-threaded, sysctl's added
9 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
10 * Enforced range limit on SEM_UNDO
11 * (c) 2001 Red Hat Inc
12 * Lockless wakeup
13 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
14 * (c) 2016 Davidlohr Bueso <dave@stgolabs.net>
15 * Further wakeup optimizations, documentation
16 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
17 *
18 * support for audit of ipc object properties and permission changes
19 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
20 *
21 * namespaces support
22 * OpenVZ, SWsoft Inc.
23 * Pavel Emelianov <xemul@openvz.org>
24 *
25 * Implementation notes: (May 2010)
26 * This file implements System V semaphores.
27 *
28 * User space visible behavior:
29 * - FIFO ordering for semop() operations (just FIFO, not starvation
30 *   protection)
31 * - multiple semaphore operations that alter the same semaphore in
32 *   one semop() are handled.
33 * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
34 *   SETALL calls.
35 * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
36 * - undo adjustments at process exit are limited to 0..SEMVMX.
37 * - namespace are supported.
38 * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
39 *   to /proc/sys/kernel/sem.
40 * - statistics about the usage are reported in /proc/sysvipc/sem.
41 *
42 * Internals:
43 * - scalability:
44 *   - all global variables are read-mostly.
45 *   - semop() calls and semctl(RMID) are synchronized by RCU.
46 *   - most operations do write operations (actually: spin_lock calls) to
47 *     the per-semaphore array structure.
48 *   Thus: Perfect SMP scaling between independent semaphore arrays.
49 *         If multiple semaphores in one array are used, then cache line
50 *         trashing on the semaphore array spinlock will limit the scaling.
51 * - semncnt and semzcnt are calculated on demand in count_semcnt()
52 * - the task that performs a successful semop() scans the list of all
53 *   sleeping tasks and completes any pending operations that can be fulfilled.
54 *   Semaphores are actively given to waiting tasks (necessary for FIFO).
55 *   (see update_queue())
56 * - To improve the scalability, the actual wake-up calls are performed after
57 *   dropping all locks. (see wake_up_sem_queue_prepare())
58 * - All work is done by the waker, the woken up task does not have to do
59 *   anything - not even acquiring a lock or dropping a refcount.
60 * - A woken up task may not even touch the semaphore array anymore, it may
61 *   have been destroyed already by a semctl(RMID).
62 * - UNDO values are stored in an array (one per process and per
63 *   semaphore array, lazily allocated). For backwards compatibility, multiple
64 *   modes for the UNDO variables are supported (per process, per thread)
65 *   (see copy_semundo, CLONE_SYSVSEM)
66 * - There are two lists of the pending operations: a per-array list
67 *   and per-semaphore list (stored in the array). This allows to achieve FIFO
68 *   ordering without always scanning all pending operations.
69 *   The worst-case behavior is nevertheless O(N^2) for N wakeups.
70 */
71
72#include <linux/slab.h>
73#include <linux/spinlock.h>
74#include <linux/init.h>
75#include <linux/proc_fs.h>
76#include <linux/time.h>
77#include <linux/security.h>
78#include <linux/syscalls.h>
79#include <linux/audit.h>
80#include <linux/capability.h>
81#include <linux/seq_file.h>
82#include <linux/rwsem.h>
83#include <linux/nsproxy.h>
84#include <linux/ipc_namespace.h>
85#include <linux/sched/wake_q.h>
86
87#include <linux/uaccess.h>
88#include "util.h"
89
90
91/* One queue for each sleeping process in the system. */
92struct sem_queue {
93	struct list_head	list;	 /* queue of pending operations */
94	struct task_struct	*sleeper; /* this process */
95	struct sem_undo		*undo;	 /* undo structure */
96	int			pid;	 /* process id of requesting process */
97	int			status;	 /* completion status of operation */
98	struct sembuf		*sops;	 /* array of pending operations */
99	struct sembuf		*blocking; /* the operation that blocked */
100	int			nsops;	 /* number of operations */
101	bool			alter;	 /* does *sops alter the array? */
102	bool                    dupsop;	 /* sops on more than one sem_num */
103};
104
105/* Each task has a list of undo requests. They are executed automatically
106 * when the process exits.
107 */
108struct sem_undo {
109	struct list_head	list_proc;	/* per-process list: *
110						 * all undos from one process
111						 * rcu protected */
112	struct rcu_head		rcu;		/* rcu struct for sem_undo */
113	struct sem_undo_list	*ulp;		/* back ptr to sem_undo_list */
114	struct list_head	list_id;	/* per semaphore array list:
115						 * all undos for one array */
116	int			semid;		/* semaphore set identifier */
117	short			*semadj;	/* array of adjustments */
118						/* one per semaphore */
119};
120
121/* sem_undo_list controls shared access to the list of sem_undo structures
122 * that may be shared among all a CLONE_SYSVSEM task group.
123 */
124struct sem_undo_list {
125	atomic_t		refcnt;
126	spinlock_t		lock;
127	struct list_head	list_proc;
128};
129
130
131#define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
132
133#define sem_checkid(sma, semid)	ipc_checkid(&sma->sem_perm, semid)
134
135static int newary(struct ipc_namespace *, struct ipc_params *);
136static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
137#ifdef CONFIG_PROC_FS
138static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
139#endif
140
141#define SEMMSL_FAST	256 /* 512 bytes on stack */
142#define SEMOPM_FAST	64  /* ~ 372 bytes on stack */
143
144/*
145 * Switching from the mode suitable for simple ops
146 * to the mode for complex ops is costly. Therefore:
147 * use some hysteresis
148 */
149#define USE_GLOBAL_LOCK_HYSTERESIS	10
150
151/*
152 * Locking:
153 * a) global sem_lock() for read/write
154 *	sem_undo.id_next,
155 *	sem_array.complex_count,
156 *	sem_array.pending{_alter,_const},
157 *	sem_array.sem_undo
158 *
159 * b) global or semaphore sem_lock() for read/write:
160 *	sem_array.sems[i].pending_{const,alter}:
161 *
162 * c) special:
163 *	sem_undo_list.list_proc:
164 *	* undo_list->lock for write
165 *	* rcu for read
166 *	use_global_lock:
167 *	* global sem_lock() for write
168 *	* either local or global sem_lock() for read.
169 *
170 * Memory ordering:
171 * Most ordering is enforced by using spin_lock() and spin_unlock().
172 * The special case is use_global_lock:
173 * Setting it from non-zero to 0 is a RELEASE, this is ensured by
174 * using smp_store_release().
175 * Testing if it is non-zero is an ACQUIRE, this is ensured by using
176 * smp_load_acquire().
177 * Setting it from 0 to non-zero must be ordered with regards to
178 * this smp_load_acquire(), this is guaranteed because the smp_load_acquire()
179 * is inside a spin_lock() and after a write from 0 to non-zero a
180 * spin_lock()+spin_unlock() is done.
181 */
182
183#define sc_semmsl	sem_ctls[0]
184#define sc_semmns	sem_ctls[1]
185#define sc_semopm	sem_ctls[2]
186#define sc_semmni	sem_ctls[3]
187
188void sem_init_ns(struct ipc_namespace *ns)
189{
190	ns->sc_semmsl = SEMMSL;
191	ns->sc_semmns = SEMMNS;
192	ns->sc_semopm = SEMOPM;
193	ns->sc_semmni = SEMMNI;
194	ns->used_sems = 0;
195	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
196}
197
198#ifdef CONFIG_IPC_NS
199void sem_exit_ns(struct ipc_namespace *ns)
200{
201	free_ipcs(ns, &sem_ids(ns), freeary);
202	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
203}
204#endif
205
206void __init sem_init(void)
207{
208	sem_init_ns(&init_ipc_ns);
209	ipc_init_proc_interface("sysvipc/sem",
210				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
211				IPC_SEM_IDS, sysvipc_sem_proc_show);
212}
213
214/**
215 * unmerge_queues - unmerge queues, if possible.
216 * @sma: semaphore array
217 *
218 * The function unmerges the wait queues if complex_count is 0.
219 * It must be called prior to dropping the global semaphore array lock.
220 */
221static void unmerge_queues(struct sem_array *sma)
222{
223	struct sem_queue *q, *tq;
224
225	/* complex operations still around? */
226	if (sma->complex_count)
227		return;
228	/*
229	 * We will switch back to simple mode.
230	 * Move all pending operation back into the per-semaphore
231	 * queues.
232	 */
233	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
234		struct sem *curr;
235		curr = &sma->sems[q->sops[0].sem_num];
236
237		list_add_tail(&q->list, &curr->pending_alter);
238	}
239	INIT_LIST_HEAD(&sma->pending_alter);
240}
241
242/**
243 * merge_queues - merge single semop queues into global queue
244 * @sma: semaphore array
245 *
246 * This function merges all per-semaphore queues into the global queue.
247 * It is necessary to achieve FIFO ordering for the pending single-sop
248 * operations when a multi-semop operation must sleep.
249 * Only the alter operations must be moved, the const operations can stay.
250 */
251static void merge_queues(struct sem_array *sma)
252{
253	int i;
254	for (i = 0; i < sma->sem_nsems; i++) {
255		struct sem *sem = &sma->sems[i];
256
257		list_splice_init(&sem->pending_alter, &sma->pending_alter);
258	}
259}
260
261static void sem_rcu_free(struct rcu_head *head)
262{
263	struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
264	struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
265
266	security_sem_free(sma);
267	kvfree(sma);
268}
269
270/*
271 * Enter the mode suitable for non-simple operations:
272 * Caller must own sem_perm.lock.
273 */
274static void complexmode_enter(struct sem_array *sma)
275{
276	int i;
277	struct sem *sem;
278
279	if (sma->use_global_lock > 0)  {
280		/*
281		 * We are already in global lock mode.
282		 * Nothing to do, just reset the
283		 * counter until we return to simple mode.
284		 */
285		sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
286		return;
287	}
288	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
289
290	for (i = 0; i < sma->sem_nsems; i++) {
291		sem = &sma->sems[i];
292		spin_lock(&sem->lock);
293		spin_unlock(&sem->lock);
294	}
295}
296
297/*
298 * Try to leave the mode that disallows simple operations:
299 * Caller must own sem_perm.lock.
300 */
301static void complexmode_tryleave(struct sem_array *sma)
302{
303	if (sma->complex_count)  {
304		/* Complex ops are sleeping.
305		 * We must stay in complex mode
306		 */
307		return;
308	}
309	if (sma->use_global_lock == 1) {
310		/*
311		 * Immediately after setting use_global_lock to 0,
312		 * a simple op can start. Thus: all memory writes
313		 * performed by the current operation must be visible
314		 * before we set use_global_lock to 0.
315		 */
316		smp_store_release(&sma->use_global_lock, 0);
317	} else {
318		sma->use_global_lock--;
319	}
320}
321
322#define SEM_GLOBAL_LOCK	(-1)
323/*
324 * If the request contains only one semaphore operation, and there are
325 * no complex transactions pending, lock only the semaphore involved.
326 * Otherwise, lock the entire semaphore array, since we either have
327 * multiple semaphores in our own semops, or we need to look at
328 * semaphores from other pending complex operations.
329 */
330static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
331			      int nsops)
332{
333	struct sem *sem;
334
335	if (nsops != 1) {
336		/* Complex operation - acquire a full lock */
337		ipc_lock_object(&sma->sem_perm);
338
339		/* Prevent parallel simple ops */
340		complexmode_enter(sma);
341		return SEM_GLOBAL_LOCK;
342	}
343
344	/*
345	 * Only one semaphore affected - try to optimize locking.
346	 * Optimized locking is possible if no complex operation
347	 * is either enqueued or processed right now.
348	 *
349	 * Both facts are tracked by use_global_mode.
350	 */
351	sem = &sma->sems[sops->sem_num];
352
353	/*
354	 * Initial check for use_global_lock. Just an optimization,
355	 * no locking, no memory barrier.
356	 */
357	if (!sma->use_global_lock) {
358		/*
359		 * It appears that no complex operation is around.
360		 * Acquire the per-semaphore lock.
361		 */
362		spin_lock(&sem->lock);
363
364		/* pairs with smp_store_release() */
365		if (!smp_load_acquire(&sma->use_global_lock)) {
366			/* fast path successful! */
367			return sops->sem_num;
368		}
369		spin_unlock(&sem->lock);
370	}
371
372	/* slow path: acquire the full lock */
373	ipc_lock_object(&sma->sem_perm);
374
375	if (sma->use_global_lock == 0) {
376		/*
377		 * The use_global_lock mode ended while we waited for
378		 * sma->sem_perm.lock. Thus we must switch to locking
379		 * with sem->lock.
380		 * Unlike in the fast path, there is no need to recheck
381		 * sma->use_global_lock after we have acquired sem->lock:
382		 * We own sma->sem_perm.lock, thus use_global_lock cannot
383		 * change.
384		 */
385		spin_lock(&sem->lock);
386
387		ipc_unlock_object(&sma->sem_perm);
388		return sops->sem_num;
389	} else {
390		/*
391		 * Not a false alarm, thus continue to use the global lock
392		 * mode. No need for complexmode_enter(), this was done by
393		 * the caller that has set use_global_mode to non-zero.
394		 */
395		return SEM_GLOBAL_LOCK;
396	}
397}
398
399static inline void sem_unlock(struct sem_array *sma, int locknum)
400{
401	if (locknum == SEM_GLOBAL_LOCK) {
402		unmerge_queues(sma);
403		complexmode_tryleave(sma);
404		ipc_unlock_object(&sma->sem_perm);
405	} else {
406		struct sem *sem = &sma->sems[locknum];
407		spin_unlock(&sem->lock);
408	}
409}
410
411/*
412 * sem_lock_(check_) routines are called in the paths where the rwsem
413 * is not held.
414 *
415 * The caller holds the RCU read lock.
416 */
417static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
418{
419	struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
420
421	if (IS_ERR(ipcp))
422		return ERR_CAST(ipcp);
423
424	return container_of(ipcp, struct sem_array, sem_perm);
425}
426
427static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
428							int id)
429{
430	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
431
432	if (IS_ERR(ipcp))
433		return ERR_CAST(ipcp);
434
435	return container_of(ipcp, struct sem_array, sem_perm);
436}
437
438static inline void sem_lock_and_putref(struct sem_array *sma)
439{
440	sem_lock(sma, NULL, -1);
441	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
442}
443
444static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
445{
446	ipc_rmid(&sem_ids(ns), &s->sem_perm);
447}
448
449static struct sem_array *sem_alloc(size_t nsems)
450{
451	struct sem_array *sma;
452	size_t size;
453
454	if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
455		return NULL;
456
457	size = sizeof(*sma) + nsems * sizeof(sma->sems[0]);
458	sma = kvmalloc(size, GFP_KERNEL);
459	if (unlikely(!sma))
460		return NULL;
461
462	memset(sma, 0, size);
463
464	return sma;
465}
466
467/**
468 * newary - Create a new semaphore set
469 * @ns: namespace
470 * @params: ptr to the structure that contains key, semflg and nsems
471 *
472 * Called with sem_ids.rwsem held (as a writer)
473 */
474static int newary(struct ipc_namespace *ns, struct ipc_params *params)
475{
476	int retval;
477	struct sem_array *sma;
478	key_t key = params->key;
479	int nsems = params->u.nsems;
480	int semflg = params->flg;
481	int i;
482
483	if (!nsems)
484		return -EINVAL;
485	if (ns->used_sems + nsems > ns->sc_semmns)
486		return -ENOSPC;
487
488	sma = sem_alloc(nsems);
489	if (!sma)
490		return -ENOMEM;
491
492	sma->sem_perm.mode = (semflg & S_IRWXUGO);
493	sma->sem_perm.key = key;
494
495	sma->sem_perm.security = NULL;
496	retval = security_sem_alloc(sma);
497	if (retval) {
498		kvfree(sma);
499		return retval;
500	}
501
502	for (i = 0; i < nsems; i++) {
503		INIT_LIST_HEAD(&sma->sems[i].pending_alter);
504		INIT_LIST_HEAD(&sma->sems[i].pending_const);
505		spin_lock_init(&sma->sems[i].lock);
506	}
507
508	sma->complex_count = 0;
509	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
510	INIT_LIST_HEAD(&sma->pending_alter);
511	INIT_LIST_HEAD(&sma->pending_const);
512	INIT_LIST_HEAD(&sma->list_id);
513	sma->sem_nsems = nsems;
514	sma->sem_ctime = get_seconds();
515
516	retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
517	if (retval < 0) {
518		call_rcu(&sma->sem_perm.rcu, sem_rcu_free);
519		return retval;
520	}
521	ns->used_sems += nsems;
522
523	sem_unlock(sma, -1);
524	rcu_read_unlock();
525
526	return sma->sem_perm.id;
527}
528
529
530/*
531 * Called with sem_ids.rwsem and ipcp locked.
532 */
533static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
534{
535	struct sem_array *sma;
536
537	sma = container_of(ipcp, struct sem_array, sem_perm);
538	return security_sem_associate(sma, semflg);
539}
540
541/*
542 * Called with sem_ids.rwsem and ipcp locked.
543 */
544static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
545				struct ipc_params *params)
546{
547	struct sem_array *sma;
548
549	sma = container_of(ipcp, struct sem_array, sem_perm);
550	if (params->u.nsems > sma->sem_nsems)
551		return -EINVAL;
552
553	return 0;
554}
555
556SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
557{
558	struct ipc_namespace *ns;
559	static const struct ipc_ops sem_ops = {
560		.getnew = newary,
561		.associate = sem_security,
562		.more_checks = sem_more_checks,
563	};
564	struct ipc_params sem_params;
565
566	ns = current->nsproxy->ipc_ns;
567
568	if (nsems < 0 || nsems > ns->sc_semmsl)
569		return -EINVAL;
570
571	sem_params.key = key;
572	sem_params.flg = semflg;
573	sem_params.u.nsems = nsems;
574
575	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
576}
577
578/**
579 * perform_atomic_semop[_slow] - Attempt to perform semaphore
580 *                               operations on a given array.
581 * @sma: semaphore array
582 * @q: struct sem_queue that describes the operation
583 *
584 * Caller blocking are as follows, based the value
585 * indicated by the semaphore operation (sem_op):
586 *
587 *  (1) >0 never blocks.
588 *  (2)  0 (wait-for-zero operation): semval is non-zero.
589 *  (3) <0 attempting to decrement semval to a value smaller than zero.
590 *
591 * Returns 0 if the operation was possible.
592 * Returns 1 if the operation is impossible, the caller must sleep.
593 * Returns <0 for error codes.
594 */
595static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
596{
597	int result, sem_op, nsops, pid;
598	struct sembuf *sop;
599	struct sem *curr;
600	struct sembuf *sops;
601	struct sem_undo *un;
602
603	sops = q->sops;
604	nsops = q->nsops;
605	un = q->undo;
606
607	for (sop = sops; sop < sops + nsops; sop++) {
608		curr = &sma->sems[sop->sem_num];
609		sem_op = sop->sem_op;
610		result = curr->semval;
611
612		if (!sem_op && result)
613			goto would_block;
614
615		result += sem_op;
616		if (result < 0)
617			goto would_block;
618		if (result > SEMVMX)
619			goto out_of_range;
620
621		if (sop->sem_flg & SEM_UNDO) {
622			int undo = un->semadj[sop->sem_num] - sem_op;
623			/* Exceeding the undo range is an error. */
624			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
625				goto out_of_range;
626			un->semadj[sop->sem_num] = undo;
627		}
628
629		curr->semval = result;
630	}
631
632	sop--;
633	pid = q->pid;
634	while (sop >= sops) {
635		sma->sems[sop->sem_num].sempid = pid;
636		sop--;
637	}
638
639	return 0;
640
641out_of_range:
642	result = -ERANGE;
643	goto undo;
644
645would_block:
646	q->blocking = sop;
647
648	if (sop->sem_flg & IPC_NOWAIT)
649		result = -EAGAIN;
650	else
651		result = 1;
652
653undo:
654	sop--;
655	while (sop >= sops) {
656		sem_op = sop->sem_op;
657		sma->sems[sop->sem_num].semval -= sem_op;
658		if (sop->sem_flg & SEM_UNDO)
659			un->semadj[sop->sem_num] += sem_op;
660		sop--;
661	}
662
663	return result;
664}
665
666static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
667{
668	int result, sem_op, nsops;
669	struct sembuf *sop;
670	struct sem *curr;
671	struct sembuf *sops;
672	struct sem_undo *un;
673
674	sops = q->sops;
675	nsops = q->nsops;
676	un = q->undo;
677
678	if (unlikely(q->dupsop))
679		return perform_atomic_semop_slow(sma, q);
680
681	/*
682	 * We scan the semaphore set twice, first to ensure that the entire
683	 * operation can succeed, therefore avoiding any pointless writes
684	 * to shared memory and having to undo such changes in order to block
685	 * until the operations can go through.
686	 */
687	for (sop = sops; sop < sops + nsops; sop++) {
688		curr = &sma->sems[sop->sem_num];
689		sem_op = sop->sem_op;
690		result = curr->semval;
691
692		if (!sem_op && result)
693			goto would_block; /* wait-for-zero */
694
695		result += sem_op;
696		if (result < 0)
697			goto would_block;
698
699		if (result > SEMVMX)
700			return -ERANGE;
701
702		if (sop->sem_flg & SEM_UNDO) {
703			int undo = un->semadj[sop->sem_num] - sem_op;
704
705			/* Exceeding the undo range is an error. */
706			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
707				return -ERANGE;
708		}
709	}
710
711	for (sop = sops; sop < sops + nsops; sop++) {
712		curr = &sma->sems[sop->sem_num];
713		sem_op = sop->sem_op;
714		result = curr->semval;
715
716		if (sop->sem_flg & SEM_UNDO) {
717			int undo = un->semadj[sop->sem_num] - sem_op;
718
719			un->semadj[sop->sem_num] = undo;
720		}
721		curr->semval += sem_op;
722		curr->sempid = q->pid;
723	}
724
725	return 0;
726
727would_block:
728	q->blocking = sop;
729	return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
730}
731
732static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
733					     struct wake_q_head *wake_q)
734{
735	wake_q_add(wake_q, q->sleeper);
736	/*
737	 * Rely on the above implicit barrier, such that we can
738	 * ensure that we hold reference to the task before setting
739	 * q->status. Otherwise we could race with do_exit if the
740	 * task is awoken by an external event before calling
741	 * wake_up_process().
742	 */
743	WRITE_ONCE(q->status, error);
744}
745
746static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
747{
748	list_del(&q->list);
749	if (q->nsops > 1)
750		sma->complex_count--;
751}
752
753/** check_restart(sma, q)
754 * @sma: semaphore array
755 * @q: the operation that just completed
756 *
757 * update_queue is O(N^2) when it restarts scanning the whole queue of
758 * waiting operations. Therefore this function checks if the restart is
759 * really necessary. It is called after a previously waiting operation
760 * modified the array.
761 * Note that wait-for-zero operations are handled without restart.
762 */
763static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
764{
765	/* pending complex alter operations are too difficult to analyse */
766	if (!list_empty(&sma->pending_alter))
767		return 1;
768
769	/* we were a sleeping complex operation. Too difficult */
770	if (q->nsops > 1)
771		return 1;
772
773	/* It is impossible that someone waits for the new value:
774	 * - complex operations always restart.
775	 * - wait-for-zero are handled seperately.
776	 * - q is a previously sleeping simple operation that
777	 *   altered the array. It must be a decrement, because
778	 *   simple increments never sleep.
779	 * - If there are older (higher priority) decrements
780	 *   in the queue, then they have observed the original
781	 *   semval value and couldn't proceed. The operation
782	 *   decremented to value - thus they won't proceed either.
783	 */
784	return 0;
785}
786
787/**
788 * wake_const_ops - wake up non-alter tasks
789 * @sma: semaphore array.
790 * @semnum: semaphore that was modified.
791 * @wake_q: lockless wake-queue head.
792 *
793 * wake_const_ops must be called after a semaphore in a semaphore array
794 * was set to 0. If complex const operations are pending, wake_const_ops must
795 * be called with semnum = -1, as well as with the number of each modified
796 * semaphore.
797 * The tasks that must be woken up are added to @wake_q. The return code
798 * is stored in q->pid.
799 * The function returns 1 if at least one operation was completed successfully.
800 */
801static int wake_const_ops(struct sem_array *sma, int semnum,
802			  struct wake_q_head *wake_q)
803{
804	struct sem_queue *q, *tmp;
805	struct list_head *pending_list;
806	int semop_completed = 0;
807
808	if (semnum == -1)
809		pending_list = &sma->pending_const;
810	else
811		pending_list = &sma->sems[semnum].pending_const;
812
813	list_for_each_entry_safe(q, tmp, pending_list, list) {
814		int error = perform_atomic_semop(sma, q);
815
816		if (error > 0)
817			continue;
818		/* operation completed, remove from queue & wakeup */
819		unlink_queue(sma, q);
820
821		wake_up_sem_queue_prepare(q, error, wake_q);
822		if (error == 0)
823			semop_completed = 1;
824	}
825
826	return semop_completed;
827}
828
829/**
830 * do_smart_wakeup_zero - wakeup all wait for zero tasks
831 * @sma: semaphore array
832 * @sops: operations that were performed
833 * @nsops: number of operations
834 * @wake_q: lockless wake-queue head
835 *
836 * Checks all required queue for wait-for-zero operations, based
837 * on the actual changes that were performed on the semaphore array.
838 * The function returns 1 if at least one operation was completed successfully.
839 */
840static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
841				int nsops, struct wake_q_head *wake_q)
842{
843	int i;
844	int semop_completed = 0;
845	int got_zero = 0;
846
847	/* first: the per-semaphore queues, if known */
848	if (sops) {
849		for (i = 0; i < nsops; i++) {
850			int num = sops[i].sem_num;
851
852			if (sma->sems[num].semval == 0) {
853				got_zero = 1;
854				semop_completed |= wake_const_ops(sma, num, wake_q);
855			}
856		}
857	} else {
858		/*
859		 * No sops means modified semaphores not known.
860		 * Assume all were changed.
861		 */
862		for (i = 0; i < sma->sem_nsems; i++) {
863			if (sma->sems[i].semval == 0) {
864				got_zero = 1;
865				semop_completed |= wake_const_ops(sma, i, wake_q);
866			}
867		}
868	}
869	/*
870	 * If one of the modified semaphores got 0,
871	 * then check the global queue, too.
872	 */
873	if (got_zero)
874		semop_completed |= wake_const_ops(sma, -1, wake_q);
875
876	return semop_completed;
877}
878
879
880/**
881 * update_queue - look for tasks that can be completed.
882 * @sma: semaphore array.
883 * @semnum: semaphore that was modified.
884 * @wake_q: lockless wake-queue head.
885 *
886 * update_queue must be called after a semaphore in a semaphore array
887 * was modified. If multiple semaphores were modified, update_queue must
888 * be called with semnum = -1, as well as with the number of each modified
889 * semaphore.
890 * The tasks that must be woken up are added to @wake_q. The return code
891 * is stored in q->pid.
892 * The function internally checks if const operations can now succeed.
893 *
894 * The function return 1 if at least one semop was completed successfully.
895 */
896static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
897{
898	struct sem_queue *q, *tmp;
899	struct list_head *pending_list;
900	int semop_completed = 0;
901
902	if (semnum == -1)
903		pending_list = &sma->pending_alter;
904	else
905		pending_list = &sma->sems[semnum].pending_alter;
906
907again:
908	list_for_each_entry_safe(q, tmp, pending_list, list) {
909		int error, restart;
910
911		/* If we are scanning the single sop, per-semaphore list of
912		 * one semaphore and that semaphore is 0, then it is not
913		 * necessary to scan further: simple increments
914		 * that affect only one entry succeed immediately and cannot
915		 * be in the  per semaphore pending queue, and decrements
916		 * cannot be successful if the value is already 0.
917		 */
918		if (semnum != -1 && sma->sems[semnum].semval == 0)
919			break;
920
921		error = perform_atomic_semop(sma, q);
922
923		/* Does q->sleeper still need to sleep? */
924		if (error > 0)
925			continue;
926
927		unlink_queue(sma, q);
928
929		if (error) {
930			restart = 0;
931		} else {
932			semop_completed = 1;
933			do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
934			restart = check_restart(sma, q);
935		}
936
937		wake_up_sem_queue_prepare(q, error, wake_q);
938		if (restart)
939			goto again;
940	}
941	return semop_completed;
942}
943
944/**
945 * set_semotime - set sem_otime
946 * @sma: semaphore array
947 * @sops: operations that modified the array, may be NULL
948 *
949 * sem_otime is replicated to avoid cache line trashing.
950 * This function sets one instance to the current time.
951 */
952static void set_semotime(struct sem_array *sma, struct sembuf *sops)
953{
954	if (sops == NULL) {
955		sma->sems[0].sem_otime = get_seconds();
956	} else {
957		sma->sems[sops[0].sem_num].sem_otime =
958							get_seconds();
959	}
960}
961
962/**
963 * do_smart_update - optimized update_queue
964 * @sma: semaphore array
965 * @sops: operations that were performed
966 * @nsops: number of operations
967 * @otime: force setting otime
968 * @wake_q: lockless wake-queue head
969 *
970 * do_smart_update() does the required calls to update_queue and wakeup_zero,
971 * based on the actual changes that were performed on the semaphore array.
972 * Note that the function does not do the actual wake-up: the caller is
973 * responsible for calling wake_up_q().
974 * It is safe to perform this call after dropping all locks.
975 */
976static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
977			    int otime, struct wake_q_head *wake_q)
978{
979	int i;
980
981	otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
982
983	if (!list_empty(&sma->pending_alter)) {
984		/* semaphore array uses the global queue - just process it. */
985		otime |= update_queue(sma, -1, wake_q);
986	} else {
987		if (!sops) {
988			/*
989			 * No sops, thus the modified semaphores are not
990			 * known. Check all.
991			 */
992			for (i = 0; i < sma->sem_nsems; i++)
993				otime |= update_queue(sma, i, wake_q);
994		} else {
995			/*
996			 * Check the semaphores that were increased:
997			 * - No complex ops, thus all sleeping ops are
998			 *   decrease.
999			 * - if we decreased the value, then any sleeping
1000			 *   semaphore ops wont be able to run: If the
1001			 *   previous value was too small, then the new
1002			 *   value will be too small, too.
1003			 */
1004			for (i = 0; i < nsops; i++) {
1005				if (sops[i].sem_op > 0) {
1006					otime |= update_queue(sma,
1007							      sops[i].sem_num, wake_q);
1008				}
1009			}
1010		}
1011	}
1012	if (otime)
1013		set_semotime(sma, sops);
1014}
1015
1016/*
1017 * check_qop: Test if a queued operation sleeps on the semaphore semnum
1018 */
1019static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1020			bool count_zero)
1021{
1022	struct sembuf *sop = q->blocking;
1023
1024	/*
1025	 * Linux always (since 0.99.10) reported a task as sleeping on all
1026	 * semaphores. This violates SUS, therefore it was changed to the
1027	 * standard compliant behavior.
1028	 * Give the administrators a chance to notice that an application
1029	 * might misbehave because it relies on the Linux behavior.
1030	 */
1031	pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1032			"The task %s (%d) triggered the difference, watch for misbehavior.\n",
1033			current->comm, task_pid_nr(current));
1034
1035	if (sop->sem_num != semnum)
1036		return 0;
1037
1038	if (count_zero && sop->sem_op == 0)
1039		return 1;
1040	if (!count_zero && sop->sem_op < 0)
1041		return 1;
1042
1043	return 0;
1044}
1045
1046/* The following counts are associated to each semaphore:
1047 *   semncnt        number of tasks waiting on semval being nonzero
1048 *   semzcnt        number of tasks waiting on semval being zero
1049 *
1050 * Per definition, a task waits only on the semaphore of the first semop
1051 * that cannot proceed, even if additional operation would block, too.
1052 */
1053static int count_semcnt(struct sem_array *sma, ushort semnum,
1054			bool count_zero)
1055{
1056	struct list_head *l;
1057	struct sem_queue *q;
1058	int semcnt;
1059
1060	semcnt = 0;
1061	/* First: check the simple operations. They are easy to evaluate */
1062	if (count_zero)
1063		l = &sma->sems[semnum].pending_const;
1064	else
1065		l = &sma->sems[semnum].pending_alter;
1066
1067	list_for_each_entry(q, l, list) {
1068		/* all task on a per-semaphore list sleep on exactly
1069		 * that semaphore
1070		 */
1071		semcnt++;
1072	}
1073
1074	/* Then: check the complex operations. */
1075	list_for_each_entry(q, &sma->pending_alter, list) {
1076		semcnt += check_qop(sma, semnum, q, count_zero);
1077	}
1078	if (count_zero) {
1079		list_for_each_entry(q, &sma->pending_const, list) {
1080			semcnt += check_qop(sma, semnum, q, count_zero);
1081		}
1082	}
1083	return semcnt;
1084}
1085
1086/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1087 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1088 * remains locked on exit.
1089 */
1090static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1091{
1092	struct sem_undo *un, *tu;
1093	struct sem_queue *q, *tq;
1094	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1095	int i;
1096	DEFINE_WAKE_Q(wake_q);
1097
1098	/* Free the existing undo structures for this semaphore set.  */
1099	ipc_assert_locked_object(&sma->sem_perm);
1100	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1101		list_del(&un->list_id);
1102		spin_lock(&un->ulp->lock);
1103		un->semid = -1;
1104		list_del_rcu(&un->list_proc);
1105		spin_unlock(&un->ulp->lock);
1106		kfree_rcu(un, rcu);
1107	}
1108
1109	/* Wake up all pending processes and let them fail with EIDRM. */
1110	list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1111		unlink_queue(sma, q);
1112		wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1113	}
1114
1115	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1116		unlink_queue(sma, q);
1117		wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1118	}
1119	for (i = 0; i < sma->sem_nsems; i++) {
1120		struct sem *sem = &sma->sems[i];
1121		list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1122			unlink_queue(sma, q);
1123			wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1124		}
1125		list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1126			unlink_queue(sma, q);
1127			wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1128		}
1129	}
1130
1131	/* Remove the semaphore set from the IDR */
1132	sem_rmid(ns, sma);
1133	sem_unlock(sma, -1);
1134	rcu_read_unlock();
1135
1136	wake_up_q(&wake_q);
1137	ns->used_sems -= sma->sem_nsems;
1138	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1139}
1140
1141static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1142{
1143	switch (version) {
1144	case IPC_64:
1145		return copy_to_user(buf, in, sizeof(*in));
1146	case IPC_OLD:
1147	    {
1148		struct semid_ds out;
1149
1150		memset(&out, 0, sizeof(out));
1151
1152		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1153
1154		out.sem_otime	= in->sem_otime;
1155		out.sem_ctime	= in->sem_ctime;
1156		out.sem_nsems	= in->sem_nsems;
1157
1158		return copy_to_user(buf, &out, sizeof(out));
1159	    }
1160	default:
1161		return -EINVAL;
1162	}
1163}
1164
1165static time_t get_semotime(struct sem_array *sma)
1166{
1167	int i;
1168	time_t res;
1169
1170	res = sma->sems[0].sem_otime;
1171	for (i = 1; i < sma->sem_nsems; i++) {
1172		time_t to = sma->sems[i].sem_otime;
1173
1174		if (to > res)
1175			res = to;
1176	}
1177	return res;
1178}
1179
1180static int semctl_nolock(struct ipc_namespace *ns, int semid,
1181			 int cmd, int version, void __user *p)
1182{
1183	int err;
1184	struct sem_array *sma;
1185
1186	switch (cmd) {
1187	case IPC_INFO:
1188	case SEM_INFO:
1189	{
1190		struct seminfo seminfo;
1191		int max_id;
1192
1193		err = security_sem_semctl(NULL, cmd);
1194		if (err)
1195			return err;
1196
1197		memset(&seminfo, 0, sizeof(seminfo));
1198		seminfo.semmni = ns->sc_semmni;
1199		seminfo.semmns = ns->sc_semmns;
1200		seminfo.semmsl = ns->sc_semmsl;
1201		seminfo.semopm = ns->sc_semopm;
1202		seminfo.semvmx = SEMVMX;
1203		seminfo.semmnu = SEMMNU;
1204		seminfo.semmap = SEMMAP;
1205		seminfo.semume = SEMUME;
1206		down_read(&sem_ids(ns).rwsem);
1207		if (cmd == SEM_INFO) {
1208			seminfo.semusz = sem_ids(ns).in_use;
1209			seminfo.semaem = ns->used_sems;
1210		} else {
1211			seminfo.semusz = SEMUSZ;
1212			seminfo.semaem = SEMAEM;
1213		}
1214		max_id = ipc_get_maxid(&sem_ids(ns));
1215		up_read(&sem_ids(ns).rwsem);
1216		if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1217			return -EFAULT;
1218		return (max_id < 0) ? 0 : max_id;
1219	}
1220	case IPC_STAT:
1221	case SEM_STAT:
1222	{
1223		struct semid64_ds tbuf;
1224		int id = 0;
1225
1226		memset(&tbuf, 0, sizeof(tbuf));
1227
1228		rcu_read_lock();
1229		if (cmd == SEM_STAT) {
1230			sma = sem_obtain_object(ns, semid);
1231			if (IS_ERR(sma)) {
1232				err = PTR_ERR(sma);
1233				goto out_unlock;
1234			}
1235			id = sma->sem_perm.id;
1236		} else {
1237			sma = sem_obtain_object_check(ns, semid);
1238			if (IS_ERR(sma)) {
1239				err = PTR_ERR(sma);
1240				goto out_unlock;
1241			}
1242		}
1243
1244		err = -EACCES;
1245		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1246			goto out_unlock;
1247
1248		err = security_sem_semctl(sma, cmd);
1249		if (err)
1250			goto out_unlock;
1251
1252		kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1253		tbuf.sem_otime = get_semotime(sma);
1254		tbuf.sem_ctime = sma->sem_ctime;
1255		tbuf.sem_nsems = sma->sem_nsems;
1256		rcu_read_unlock();
1257		if (copy_semid_to_user(p, &tbuf, version))
1258			return -EFAULT;
1259		return id;
1260	}
1261	default:
1262		return -EINVAL;
1263	}
1264out_unlock:
1265	rcu_read_unlock();
1266	return err;
1267}
1268
1269static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1270		unsigned long arg)
1271{
1272	struct sem_undo *un;
1273	struct sem_array *sma;
1274	struct sem *curr;
1275	int err, val;
1276	DEFINE_WAKE_Q(wake_q);
1277
1278#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1279	/* big-endian 64bit */
1280	val = arg >> 32;
1281#else
1282	/* 32bit or little-endian 64bit */
1283	val = arg;
1284#endif
1285
1286	if (val > SEMVMX || val < 0)
1287		return -ERANGE;
1288
1289	rcu_read_lock();
1290	sma = sem_obtain_object_check(ns, semid);
1291	if (IS_ERR(sma)) {
1292		rcu_read_unlock();
1293		return PTR_ERR(sma);
1294	}
1295
1296	if (semnum < 0 || semnum >= sma->sem_nsems) {
1297		rcu_read_unlock();
1298		return -EINVAL;
1299	}
1300
1301
1302	if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1303		rcu_read_unlock();
1304		return -EACCES;
1305	}
1306
1307	err = security_sem_semctl(sma, SETVAL);
1308	if (err) {
1309		rcu_read_unlock();
1310		return -EACCES;
1311	}
1312
1313	sem_lock(sma, NULL, -1);
1314
1315	if (!ipc_valid_object(&sma->sem_perm)) {
1316		sem_unlock(sma, -1);
1317		rcu_read_unlock();
1318		return -EIDRM;
1319	}
1320
1321	curr = &sma->sems[semnum];
1322
1323	ipc_assert_locked_object(&sma->sem_perm);
1324	list_for_each_entry(un, &sma->list_id, list_id)
1325		un->semadj[semnum] = 0;
1326
1327	curr->semval = val;
1328	curr->sempid = task_tgid_vnr(current);
1329	sma->sem_ctime = get_seconds();
1330	/* maybe some queued-up processes were waiting for this */
1331	do_smart_update(sma, NULL, 0, 0, &wake_q);
1332	sem_unlock(sma, -1);
1333	rcu_read_unlock();
1334	wake_up_q(&wake_q);
1335	return 0;
1336}
1337
1338static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1339		int cmd, void __user *p)
1340{
1341	struct sem_array *sma;
1342	struct sem *curr;
1343	int err, nsems;
1344	ushort fast_sem_io[SEMMSL_FAST];
1345	ushort *sem_io = fast_sem_io;
1346	DEFINE_WAKE_Q(wake_q);
1347
1348	rcu_read_lock();
1349	sma = sem_obtain_object_check(ns, semid);
1350	if (IS_ERR(sma)) {
1351		rcu_read_unlock();
1352		return PTR_ERR(sma);
1353	}
1354
1355	nsems = sma->sem_nsems;
1356
1357	err = -EACCES;
1358	if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1359		goto out_rcu_wakeup;
1360
1361	err = security_sem_semctl(sma, cmd);
1362	if (err)
1363		goto out_rcu_wakeup;
1364
1365	err = -EACCES;
1366	switch (cmd) {
1367	case GETALL:
1368	{
1369		ushort __user *array = p;
1370		int i;
1371
1372		sem_lock(sma, NULL, -1);
1373		if (!ipc_valid_object(&sma->sem_perm)) {
1374			err = -EIDRM;
1375			goto out_unlock;
1376		}
1377		if (nsems > SEMMSL_FAST) {
1378			if (!ipc_rcu_getref(&sma->sem_perm)) {
1379				err = -EIDRM;
1380				goto out_unlock;
1381			}
1382			sem_unlock(sma, -1);
1383			rcu_read_unlock();
1384			sem_io = kvmalloc_array(nsems, sizeof(ushort),
1385						GFP_KERNEL);
1386			if (sem_io == NULL) {
1387				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1388				return -ENOMEM;
1389			}
1390
1391			rcu_read_lock();
1392			sem_lock_and_putref(sma);
1393			if (!ipc_valid_object(&sma->sem_perm)) {
1394				err = -EIDRM;
1395				goto out_unlock;
1396			}
1397		}
1398		for (i = 0; i < sma->sem_nsems; i++)
1399			sem_io[i] = sma->sems[i].semval;
1400		sem_unlock(sma, -1);
1401		rcu_read_unlock();
1402		err = 0;
1403		if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1404			err = -EFAULT;
1405		goto out_free;
1406	}
1407	case SETALL:
1408	{
1409		int i;
1410		struct sem_undo *un;
1411
1412		if (!ipc_rcu_getref(&sma->sem_perm)) {
1413			err = -EIDRM;
1414			goto out_rcu_wakeup;
1415		}
1416		rcu_read_unlock();
1417
1418		if (nsems > SEMMSL_FAST) {
1419			sem_io = kvmalloc_array(nsems, sizeof(ushort),
1420						GFP_KERNEL);
1421			if (sem_io == NULL) {
1422				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1423				return -ENOMEM;
1424			}
1425		}
1426
1427		if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1428			ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1429			err = -EFAULT;
1430			goto out_free;
1431		}
1432
1433		for (i = 0; i < nsems; i++) {
1434			if (sem_io[i] > SEMVMX) {
1435				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1436				err = -ERANGE;
1437				goto out_free;
1438			}
1439		}
1440		rcu_read_lock();
1441		sem_lock_and_putref(sma);
1442		if (!ipc_valid_object(&sma->sem_perm)) {
1443			err = -EIDRM;
1444			goto out_unlock;
1445		}
1446
1447		for (i = 0; i < nsems; i++) {
1448			sma->sems[i].semval = sem_io[i];
1449			sma->sems[i].sempid = task_tgid_vnr(current);
1450		}
1451
1452		ipc_assert_locked_object(&sma->sem_perm);
1453		list_for_each_entry(un, &sma->list_id, list_id) {
1454			for (i = 0; i < nsems; i++)
1455				un->semadj[i] = 0;
1456		}
1457		sma->sem_ctime = get_seconds();
1458		/* maybe some queued-up processes were waiting for this */
1459		do_smart_update(sma, NULL, 0, 0, &wake_q);
1460		err = 0;
1461		goto out_unlock;
1462	}
1463	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1464	}
1465	err = -EINVAL;
1466	if (semnum < 0 || semnum >= nsems)
1467		goto out_rcu_wakeup;
1468
1469	sem_lock(sma, NULL, -1);
1470	if (!ipc_valid_object(&sma->sem_perm)) {
1471		err = -EIDRM;
1472		goto out_unlock;
1473	}
1474	curr = &sma->sems[semnum];
1475
1476	switch (cmd) {
1477	case GETVAL:
1478		err = curr->semval;
1479		goto out_unlock;
1480	case GETPID:
1481		err = curr->sempid;
1482		goto out_unlock;
1483	case GETNCNT:
1484		err = count_semcnt(sma, semnum, 0);
1485		goto out_unlock;
1486	case GETZCNT:
1487		err = count_semcnt(sma, semnum, 1);
1488		goto out_unlock;
1489	}
1490
1491out_unlock:
1492	sem_unlock(sma, -1);
1493out_rcu_wakeup:
1494	rcu_read_unlock();
1495	wake_up_q(&wake_q);
1496out_free:
1497	if (sem_io != fast_sem_io)
1498		kvfree(sem_io);
1499	return err;
1500}
1501
1502static inline unsigned long
1503copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1504{
1505	switch (version) {
1506	case IPC_64:
1507		if (copy_from_user(out, buf, sizeof(*out)))
1508			return -EFAULT;
1509		return 0;
1510	case IPC_OLD:
1511	    {
1512		struct semid_ds tbuf_old;
1513
1514		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1515			return -EFAULT;
1516
1517		out->sem_perm.uid	= tbuf_old.sem_perm.uid;
1518		out->sem_perm.gid	= tbuf_old.sem_perm.gid;
1519		out->sem_perm.mode	= tbuf_old.sem_perm.mode;
1520
1521		return 0;
1522	    }
1523	default:
1524		return -EINVAL;
1525	}
1526}
1527
1528/*
1529 * This function handles some semctl commands which require the rwsem
1530 * to be held in write mode.
1531 * NOTE: no locks must be held, the rwsem is taken inside this function.
1532 */
1533static int semctl_down(struct ipc_namespace *ns, int semid,
1534		       int cmd, int version, void __user *p)
1535{
1536	struct sem_array *sma;
1537	int err;
1538	struct semid64_ds semid64;
1539	struct kern_ipc_perm *ipcp;
1540
1541	if (cmd == IPC_SET) {
1542		if (copy_semid_from_user(&semid64, p, version))
1543			return -EFAULT;
1544	}
1545
1546	down_write(&sem_ids(ns).rwsem);
1547	rcu_read_lock();
1548
1549	ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1550				      &semid64.sem_perm, 0);
1551	if (IS_ERR(ipcp)) {
1552		err = PTR_ERR(ipcp);
1553		goto out_unlock1;
1554	}
1555
1556	sma = container_of(ipcp, struct sem_array, sem_perm);
1557
1558	err = security_sem_semctl(sma, cmd);
1559	if (err)
1560		goto out_unlock1;
1561
1562	switch (cmd) {
1563	case IPC_RMID:
1564		sem_lock(sma, NULL, -1);
1565		/* freeary unlocks the ipc object and rcu */
1566		freeary(ns, ipcp);
1567		goto out_up;
1568	case IPC_SET:
1569		sem_lock(sma, NULL, -1);
1570		err = ipc_update_perm(&semid64.sem_perm, ipcp);
1571		if (err)
1572			goto out_unlock0;
1573		sma->sem_ctime = get_seconds();
1574		break;
1575	default:
1576		err = -EINVAL;
1577		goto out_unlock1;
1578	}
1579
1580out_unlock0:
1581	sem_unlock(sma, -1);
1582out_unlock1:
1583	rcu_read_unlock();
1584out_up:
1585	up_write(&sem_ids(ns).rwsem);
1586	return err;
1587}
1588
1589SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1590{
1591	int version;
1592	struct ipc_namespace *ns;
1593	void __user *p = (void __user *)arg;
1594
1595	if (semid < 0)
1596		return -EINVAL;
1597
1598	version = ipc_parse_version(&cmd);
1599	ns = current->nsproxy->ipc_ns;
1600
1601	switch (cmd) {
1602	case IPC_INFO:
1603	case SEM_INFO:
1604	case IPC_STAT:
1605	case SEM_STAT:
1606		return semctl_nolock(ns, semid, cmd, version, p);
1607	case GETALL:
1608	case GETVAL:
1609	case GETPID:
1610	case GETNCNT:
1611	case GETZCNT:
1612	case SETALL:
1613		return semctl_main(ns, semid, semnum, cmd, p);
1614	case SETVAL:
1615		return semctl_setval(ns, semid, semnum, arg);
1616	case IPC_RMID:
1617	case IPC_SET:
1618		return semctl_down(ns, semid, cmd, version, p);
1619	default:
1620		return -EINVAL;
1621	}
1622}
1623
1624/* If the task doesn't already have a undo_list, then allocate one
1625 * here.  We guarantee there is only one thread using this undo list,
1626 * and current is THE ONE
1627 *
1628 * If this allocation and assignment succeeds, but later
1629 * portions of this code fail, there is no need to free the sem_undo_list.
1630 * Just let it stay associated with the task, and it'll be freed later
1631 * at exit time.
1632 *
1633 * This can block, so callers must hold no locks.
1634 */
1635static inline int get_undo_list(struct sem_undo_list **undo_listp)
1636{
1637	struct sem_undo_list *undo_list;
1638
1639	undo_list = current->sysvsem.undo_list;
1640	if (!undo_list) {
1641		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1642		if (undo_list == NULL)
1643			return -ENOMEM;
1644		spin_lock_init(&undo_list->lock);
1645		atomic_set(&undo_list->refcnt, 1);
1646		INIT_LIST_HEAD(&undo_list->list_proc);
1647
1648		current->sysvsem.undo_list = undo_list;
1649	}
1650	*undo_listp = undo_list;
1651	return 0;
1652}
1653
1654static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1655{
1656	struct sem_undo *un;
1657
1658	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1659		if (un->semid == semid)
1660			return un;
1661	}
1662	return NULL;
1663}
1664
1665static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1666{
1667	struct sem_undo *un;
1668
1669	assert_spin_locked(&ulp->lock);
1670
1671	un = __lookup_undo(ulp, semid);
1672	if (un) {
1673		list_del_rcu(&un->list_proc);
1674		list_add_rcu(&un->list_proc, &ulp->list_proc);
1675	}
1676	return un;
1677}
1678
1679/**
1680 * find_alloc_undo - lookup (and if not present create) undo array
1681 * @ns: namespace
1682 * @semid: semaphore array id
1683 *
1684 * The function looks up (and if not present creates) the undo structure.
1685 * The size of the undo structure depends on the size of the semaphore
1686 * array, thus the alloc path is not that straightforward.
1687 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1688 * performs a rcu_read_lock().
1689 */
1690static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1691{
1692	struct sem_array *sma;
1693	struct sem_undo_list *ulp;
1694	struct sem_undo *un, *new;
1695	int nsems, error;
1696
1697	error = get_undo_list(&ulp);
1698	if (error)
1699		return ERR_PTR(error);
1700
1701	rcu_read_lock();
1702	spin_lock(&ulp->lock);
1703	un = lookup_undo(ulp, semid);
1704	spin_unlock(&ulp->lock);
1705	if (likely(un != NULL))
1706		goto out;
1707
1708	/* no undo structure around - allocate one. */
1709	/* step 1: figure out the size of the semaphore array */
1710	sma = sem_obtain_object_check(ns, semid);
1711	if (IS_ERR(sma)) {
1712		rcu_read_unlock();
1713		return ERR_CAST(sma);
1714	}
1715
1716	nsems = sma->sem_nsems;
1717	if (!ipc_rcu_getref(&sma->sem_perm)) {
1718		rcu_read_unlock();
1719		un = ERR_PTR(-EIDRM);
1720		goto out;
1721	}
1722	rcu_read_unlock();
1723
1724	/* step 2: allocate new undo structure */
1725	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1726	if (!new) {
1727		ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1728		return ERR_PTR(-ENOMEM);
1729	}
1730
1731	/* step 3: Acquire the lock on semaphore array */
1732	rcu_read_lock();
1733	sem_lock_and_putref(sma);
1734	if (!ipc_valid_object(&sma->sem_perm)) {
1735		sem_unlock(sma, -1);
1736		rcu_read_unlock();
1737		kfree(new);
1738		un = ERR_PTR(-EIDRM);
1739		goto out;
1740	}
1741	spin_lock(&ulp->lock);
1742
1743	/*
1744	 * step 4: check for races: did someone else allocate the undo struct?
1745	 */
1746	un = lookup_undo(ulp, semid);
1747	if (un) {
1748		kfree(new);
1749		goto success;
1750	}
1751	/* step 5: initialize & link new undo structure */
1752	new->semadj = (short *) &new[1];
1753	new->ulp = ulp;
1754	new->semid = semid;
1755	assert_spin_locked(&ulp->lock);
1756	list_add_rcu(&new->list_proc, &ulp->list_proc);
1757	ipc_assert_locked_object(&sma->sem_perm);
1758	list_add(&new->list_id, &sma->list_id);
1759	un = new;
1760
1761success:
1762	spin_unlock(&ulp->lock);
1763	sem_unlock(sma, -1);
1764out:
1765	return un;
1766}
1767
1768SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1769		unsigned, nsops, const struct timespec __user *, timeout)
1770{
1771	int error = -EINVAL;
1772	struct sem_array *sma;
1773	struct sembuf fast_sops[SEMOPM_FAST];
1774	struct sembuf *sops = fast_sops, *sop;
1775	struct sem_undo *un;
1776	int max, locknum;
1777	bool undos = false, alter = false, dupsop = false;
1778	struct sem_queue queue;
1779	unsigned long dup = 0, jiffies_left = 0;
1780	struct ipc_namespace *ns;
1781
1782	ns = current->nsproxy->ipc_ns;
1783
1784	if (nsops < 1 || semid < 0)
1785		return -EINVAL;
1786	if (nsops > ns->sc_semopm)
1787		return -E2BIG;
1788	if (nsops > SEMOPM_FAST) {
1789		sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
1790		if (sops == NULL)
1791			return -ENOMEM;
1792	}
1793
1794	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
1795		error =  -EFAULT;
1796		goto out_free;
1797	}
1798
1799	if (timeout) {
1800		struct timespec _timeout;
1801		if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1802			error = -EFAULT;
1803			goto out_free;
1804		}
1805		if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1806			_timeout.tv_nsec >= 1000000000L) {
1807			error = -EINVAL;
1808			goto out_free;
1809		}
1810		jiffies_left = timespec_to_jiffies(&_timeout);
1811	}
1812
1813	max = 0;
1814	for (sop = sops; sop < sops + nsops; sop++) {
1815		unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
1816
1817		if (sop->sem_num >= max)
1818			max = sop->sem_num;
1819		if (sop->sem_flg & SEM_UNDO)
1820			undos = true;
1821		if (dup & mask) {
1822			/*
1823			 * There was a previous alter access that appears
1824			 * to have accessed the same semaphore, thus use
1825			 * the dupsop logic. "appears", because the detection
1826			 * can only check % BITS_PER_LONG.
1827			 */
1828			dupsop = true;
1829		}
1830		if (sop->sem_op != 0) {
1831			alter = true;
1832			dup |= mask;
1833		}
1834	}
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		rcu_read_unlock();
1858		goto out_free;
1859	}
1860
1861	error = -EACCES;
1862	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
1863		rcu_read_unlock();
1864		goto out_free;
1865	}
1866
1867	error = security_sem_semop(sma, sops, nsops, alter);
1868	if (error) {
1869		rcu_read_unlock();
1870		goto out_free;
1871	}
1872
1873	error = -EIDRM;
1874	locknum = sem_lock(sma, sops, nsops);
1875	/*
1876	 * We eventually might perform the following check in a lockless
1877	 * fashion, considering ipc_valid_object() locking constraints.
1878	 * If nsops == 1 and there is no contention for sem_perm.lock, then
1879	 * only a per-semaphore lock is held and it's OK to proceed with the
1880	 * check below. More details on the fine grained locking scheme
1881	 * entangled here and why it's RMID race safe on comments at sem_lock()
1882	 */
1883	if (!ipc_valid_object(&sma->sem_perm))
1884		goto out_unlock_free;
1885	/*
1886	 * semid identifiers are not unique - find_alloc_undo may have
1887	 * allocated an undo structure, it was invalidated by an RMID
1888	 * and now a new array with received the same id. Check and fail.
1889	 * This case can be detected checking un->semid. The existence of
1890	 * "un" itself is guaranteed by rcu.
1891	 */
1892	if (un && un->semid == -1)
1893		goto out_unlock_free;
1894
1895	queue.sops = sops;
1896	queue.nsops = nsops;
1897	queue.undo = un;
1898	queue.pid = task_tgid_vnr(current);
1899	queue.alter = alter;
1900	queue.dupsop = dupsop;
1901
1902	error = perform_atomic_semop(sma, &queue);
1903	if (error == 0) { /* non-blocking succesfull path */
1904		DEFINE_WAKE_Q(wake_q);
1905
1906		/*
1907		 * If the operation was successful, then do
1908		 * the required updates.
1909		 */
1910		if (alter)
1911			do_smart_update(sma, sops, nsops, 1, &wake_q);
1912		else
1913			set_semotime(sma, sops);
1914
1915		sem_unlock(sma, locknum);
1916		rcu_read_unlock();
1917		wake_up_q(&wake_q);
1918
1919		goto out_free;
1920	}
1921	if (error < 0) /* non-blocking error path */
1922		goto out_unlock_free;
1923
1924	/*
1925	 * We need to sleep on this operation, so we put the current
1926	 * task into the pending queue and go to sleep.
1927	 */
1928	if (nsops == 1) {
1929		struct sem *curr;
1930		curr = &sma->sems[sops->sem_num];
1931
1932		if (alter) {
1933			if (sma->complex_count) {
1934				list_add_tail(&queue.list,
1935						&sma->pending_alter);
1936			} else {
1937
1938				list_add_tail(&queue.list,
1939						&curr->pending_alter);
1940			}
1941		} else {
1942			list_add_tail(&queue.list, &curr->pending_const);
1943		}
1944	} else {
1945		if (!sma->complex_count)
1946			merge_queues(sma);
1947
1948		if (alter)
1949			list_add_tail(&queue.list, &sma->pending_alter);
1950		else
1951			list_add_tail(&queue.list, &sma->pending_const);
1952
1953		sma->complex_count++;
1954	}
1955
1956	do {
1957		queue.status = -EINTR;
1958		queue.sleeper = current;
1959
1960		__set_current_state(TASK_INTERRUPTIBLE);
1961		sem_unlock(sma, locknum);
1962		rcu_read_unlock();
1963
1964		if (timeout)
1965			jiffies_left = schedule_timeout(jiffies_left);
1966		else
1967			schedule();
1968
1969		/*
1970		 * fastpath: the semop has completed, either successfully or
1971		 * not, from the syscall pov, is quite irrelevant to us at this
1972		 * point; we're done.
1973		 *
1974		 * We _do_ care, nonetheless, about being awoken by a signal or
1975		 * spuriously.  The queue.status is checked again in the
1976		 * slowpath (aka after taking sem_lock), such that we can detect
1977		 * scenarios where we were awakened externally, during the
1978		 * window between wake_q_add() and wake_up_q().
1979		 */
1980		error = READ_ONCE(queue.status);
1981		if (error != -EINTR) {
1982			/*
1983			 * User space could assume that semop() is a memory
1984			 * barrier: Without the mb(), the cpu could
1985			 * speculatively read in userspace stale data that was
1986			 * overwritten by the previous owner of the semaphore.
1987			 */
1988			smp_mb();
1989			goto out_free;
1990		}
1991
1992		rcu_read_lock();
1993		locknum = sem_lock(sma, sops, nsops);
1994
1995		if (!ipc_valid_object(&sma->sem_perm))
1996			goto out_unlock_free;
1997
1998		error = READ_ONCE(queue.status);
1999
2000		/*
2001		 * If queue.status != -EINTR we are woken up by another process.
2002		 * Leave without unlink_queue(), but with sem_unlock().
2003		 */
2004		if (error != -EINTR)
2005			goto out_unlock_free;
2006
2007		/*
2008		 * If an interrupt occurred we have to clean up the queue.
2009		 */
2010		if (timeout && jiffies_left == 0)
2011			error = -EAGAIN;
2012	} while (error == -EINTR && !signal_pending(current)); /* spurious */
2013
2014	unlink_queue(sma, &queue);
2015
2016out_unlock_free:
2017	sem_unlock(sma, locknum);
2018	rcu_read_unlock();
2019out_free:
2020	if (sops != fast_sops)
2021		kfree(sops);
2022	return error;
2023}
2024
2025SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2026		unsigned, nsops)
2027{
2028	return sys_semtimedop(semid, tsops, nsops, NULL);
2029}
2030
2031/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2032 * parent and child tasks.
2033 */
2034
2035int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2036{
2037	struct sem_undo_list *undo_list;
2038	int error;
2039
2040	if (clone_flags & CLONE_SYSVSEM) {
2041		error = get_undo_list(&undo_list);
2042		if (error)
2043			return error;
2044		atomic_inc(&undo_list->refcnt);
2045		tsk->sysvsem.undo_list = undo_list;
2046	} else
2047		tsk->sysvsem.undo_list = NULL;
2048
2049	return 0;
2050}
2051
2052/*
2053 * add semadj values to semaphores, free undo structures.
2054 * undo structures are not freed when semaphore arrays are destroyed
2055 * so some of them may be out of date.
2056 * IMPLEMENTATION NOTE: There is some confusion over whether the
2057 * set of adjustments that needs to be done should be done in an atomic
2058 * manner or not. That is, if we are attempting to decrement the semval
2059 * should we queue up and wait until we can do so legally?
2060 * The original implementation attempted to do this (queue and wait).
2061 * The current implementation does not do so. The POSIX standard
2062 * and SVID should be consulted to determine what behavior is mandated.
2063 */
2064void exit_sem(struct task_struct *tsk)
2065{
2066	struct sem_undo_list *ulp;
2067
2068	ulp = tsk->sysvsem.undo_list;
2069	if (!ulp)
2070		return;
2071	tsk->sysvsem.undo_list = NULL;
2072
2073	if (!atomic_dec_and_test(&ulp->refcnt))
2074		return;
2075
2076	for (;;) {
2077		struct sem_array *sma;
2078		struct sem_undo *un;
2079		int semid, i;
2080		DEFINE_WAKE_Q(wake_q);
2081
2082		cond_resched();
2083
2084		rcu_read_lock();
2085		un = list_entry_rcu(ulp->list_proc.next,
2086				    struct sem_undo, list_proc);
2087		if (&un->list_proc == &ulp->list_proc) {
2088			/*
2089			 * We must wait for freeary() before freeing this ulp,
2090			 * in case we raced with last sem_undo. There is a small
2091			 * possibility where we exit while freeary() didn't
2092			 * finish unlocking sem_undo_list.
2093			 */
2094			spin_unlock_wait(&ulp->lock);
2095			rcu_read_unlock();
2096			break;
2097		}
2098		spin_lock(&ulp->lock);
2099		semid = un->semid;
2100		spin_unlock(&ulp->lock);
2101
2102		/* exit_sem raced with IPC_RMID, nothing to do */
2103		if (semid == -1) {
2104			rcu_read_unlock();
2105			continue;
2106		}
2107
2108		sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2109		/* exit_sem raced with IPC_RMID, nothing to do */
2110		if (IS_ERR(sma)) {
2111			rcu_read_unlock();
2112			continue;
2113		}
2114
2115		sem_lock(sma, NULL, -1);
2116		/* exit_sem raced with IPC_RMID, nothing to do */
2117		if (!ipc_valid_object(&sma->sem_perm)) {
2118			sem_unlock(sma, -1);
2119			rcu_read_unlock();
2120			continue;
2121		}
2122		un = __lookup_undo(ulp, semid);
2123		if (un == NULL) {
2124			/* exit_sem raced with IPC_RMID+semget() that created
2125			 * exactly the same semid. Nothing to do.
2126			 */
2127			sem_unlock(sma, -1);
2128			rcu_read_unlock();
2129			continue;
2130		}
2131
2132		/* remove un from the linked lists */
2133		ipc_assert_locked_object(&sma->sem_perm);
2134		list_del(&un->list_id);
2135
2136		/* we are the last process using this ulp, acquiring ulp->lock
2137		 * isn't required. Besides that, we are also protected against
2138		 * IPC_RMID as we hold sma->sem_perm lock now
2139		 */
2140		list_del_rcu(&un->list_proc);
2141
2142		/* perform adjustments registered in un */
2143		for (i = 0; i < sma->sem_nsems; i++) {
2144			struct sem *semaphore = &sma->sems[i];
2145			if (un->semadj[i]) {
2146				semaphore->semval += un->semadj[i];
2147				/*
2148				 * Range checks of the new semaphore value,
2149				 * not defined by sus:
2150				 * - Some unices ignore the undo entirely
2151				 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2152				 * - some cap the value (e.g. FreeBSD caps
2153				 *   at 0, but doesn't enforce SEMVMX)
2154				 *
2155				 * Linux caps the semaphore value, both at 0
2156				 * and at SEMVMX.
2157				 *
2158				 *	Manfred <manfred@colorfullife.com>
2159				 */
2160				if (semaphore->semval < 0)
2161					semaphore->semval = 0;
2162				if (semaphore->semval > SEMVMX)
2163					semaphore->semval = SEMVMX;
2164				semaphore->sempid = task_tgid_vnr(current);
2165			}
2166		}
2167		/* maybe some queued-up processes were waiting for this */
2168		do_smart_update(sma, NULL, 0, 1, &wake_q);
2169		sem_unlock(sma, -1);
2170		rcu_read_unlock();
2171		wake_up_q(&wake_q);
2172
2173		kfree_rcu(un, rcu);
2174	}
2175	kfree(ulp);
2176}
2177
2178#ifdef CONFIG_PROC_FS
2179static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2180{
2181	struct user_namespace *user_ns = seq_user_ns(s);
2182	struct kern_ipc_perm *ipcp = it;
2183	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
2184	time_t sem_otime;
2185
2186	/*
2187	 * The proc interface isn't aware of sem_lock(), it calls
2188	 * ipc_lock_object() directly (in sysvipc_find_ipc).
2189	 * In order to stay compatible with sem_lock(), we must
2190	 * enter / leave complex_mode.
2191	 */
2192	complexmode_enter(sma);
2193
2194	sem_otime = get_semotime(sma);
2195
2196	seq_printf(s,
2197		   "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2198		   sma->sem_perm.key,
2199		   sma->sem_perm.id,
2200		   sma->sem_perm.mode,
2201		   sma->sem_nsems,
2202		   from_kuid_munged(user_ns, sma->sem_perm.uid),
2203		   from_kgid_munged(user_ns, sma->sem_perm.gid),
2204		   from_kuid_munged(user_ns, sma->sem_perm.cuid),
2205		   from_kgid_munged(user_ns, sma->sem_perm.cgid),
2206		   sem_otime,
2207		   sma->sem_ctime);
2208
2209	complexmode_tryleave(sma);
2210
2211	return 0;
2212}
2213#endif
2214