sem.c revision eae04d25
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * linux/ipc/sem.c
4 * Copyright (C) 1992 Krishna Balasubramanian
5 * Copyright (C) 1995 Eric Schenk, Bruno Haible
6 *
7 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
8 *
9 * SMP-threaded, sysctl's added
10 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
11 * Enforced range limit on SEM_UNDO
12 * (c) 2001 Red Hat Inc
13 * Lockless wakeup
14 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
15 * (c) 2016 Davidlohr Bueso <dave@stgolabs.net>
16 * Further wakeup optimizations, documentation
17 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
18 *
19 * support for audit of ipc object properties and permission changes
20 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
21 *
22 * namespaces support
23 * OpenVZ, SWsoft Inc.
24 * Pavel Emelianov <xemul@openvz.org>
25 *
26 * Implementation notes: (May 2010)
27 * This file implements System V semaphores.
28 *
29 * User space visible behavior:
30 * - FIFO ordering for semop() operations (just FIFO, not starvation
31 *   protection)
32 * - multiple semaphore operations that alter the same semaphore in
33 *   one semop() are handled.
34 * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
35 *   SETALL calls.
36 * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
37 * - undo adjustments at process exit are limited to 0..SEMVMX.
38 * - namespace are supported.
39 * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
40 *   to /proc/sys/kernel/sem.
41 * - statistics about the usage are reported in /proc/sysvipc/sem.
42 *
43 * Internals:
44 * - scalability:
45 *   - all global variables are read-mostly.
46 *   - semop() calls and semctl(RMID) are synchronized by RCU.
47 *   - most operations do write operations (actually: spin_lock calls) to
48 *     the per-semaphore array structure.
49 *   Thus: Perfect SMP scaling between independent semaphore arrays.
50 *         If multiple semaphores in one array are used, then cache line
51 *         trashing on the semaphore array spinlock will limit the scaling.
52 * - semncnt and semzcnt are calculated on demand in count_semcnt()
53 * - the task that performs a successful semop() scans the list of all
54 *   sleeping tasks and completes any pending operations that can be fulfilled.
55 *   Semaphores are actively given to waiting tasks (necessary for FIFO).
56 *   (see update_queue())
57 * - To improve the scalability, the actual wake-up calls are performed after
58 *   dropping all locks. (see wake_up_sem_queue_prepare())
59 * - All work is done by the waker, the woken up task does not have to do
60 *   anything - not even acquiring a lock or dropping a refcount.
61 * - A woken up task may not even touch the semaphore array anymore, it may
62 *   have been destroyed already by a semctl(RMID).
63 * - UNDO values are stored in an array (one per process and per
64 *   semaphore array, lazily allocated). For backwards compatibility, multiple
65 *   modes for the UNDO variables are supported (per process, per thread)
66 *   (see copy_semundo, CLONE_SYSVSEM)
67 * - There are two lists of the pending operations: a per-array list
68 *   and per-semaphore list (stored in the array). This allows to achieve FIFO
69 *   ordering without always scanning all pending operations.
70 *   The worst-case behavior is nevertheless O(N^2) for N wakeups.
71 */
72
73#include <linux/compat.h>
74#include <linux/slab.h>
75#include <linux/spinlock.h>
76#include <linux/init.h>
77#include <linux/proc_fs.h>
78#include <linux/time.h>
79#include <linux/security.h>
80#include <linux/syscalls.h>
81#include <linux/audit.h>
82#include <linux/capability.h>
83#include <linux/seq_file.h>
84#include <linux/rwsem.h>
85#include <linux/nsproxy.h>
86#include <linux/ipc_namespace.h>
87#include <linux/sched/wake_q.h>
88#include <linux/nospec.h>
89#include <linux/rhashtable.h>
90
91#include <linux/uaccess.h>
92#include "util.h"
93
94/* One semaphore structure for each semaphore in the system. */
95struct sem {
96	int	semval;		/* current value */
97	/*
98	 * PID of the process that last modified the semaphore. For
99	 * Linux, specifically these are:
100	 *  - semop
101	 *  - semctl, via SETVAL and SETALL.
102	 *  - at task exit when performing undo adjustments (see exit_sem).
103	 */
104	struct pid *sempid;
105	spinlock_t	lock;	/* spinlock for fine-grained semtimedop */
106	struct list_head pending_alter; /* pending single-sop operations */
107					/* that alter the semaphore */
108	struct list_head pending_const; /* pending single-sop operations */
109					/* that do not alter the semaphore*/
110	time64_t	 sem_otime;	/* candidate for sem_otime */
111} ____cacheline_aligned_in_smp;
112
113/* One sem_array data structure for each set of semaphores in the system. */
114struct sem_array {
115	struct kern_ipc_perm	sem_perm;	/* permissions .. see ipc.h */
116	time64_t		sem_ctime;	/* create/last semctl() time */
117	struct list_head	pending_alter;	/* pending operations */
118						/* that alter the array */
119	struct list_head	pending_const;	/* pending complex operations */
120						/* that do not alter semvals */
121	struct list_head	list_id;	/* undo requests on this array */
122	int			sem_nsems;	/* no. of semaphores in array */
123	int			complex_count;	/* pending complex operations */
124	unsigned int		use_global_lock;/* >0: global lock required */
125
126	struct sem		sems[];
127} __randomize_layout;
128
129/* One queue for each sleeping process in the system. */
130struct sem_queue {
131	struct list_head	list;	 /* queue of pending operations */
132	struct task_struct	*sleeper; /* this process */
133	struct sem_undo		*undo;	 /* undo structure */
134	struct pid		*pid;	 /* process id of requesting process */
135	int			status;	 /* completion status of operation */
136	struct sembuf		*sops;	 /* array of pending operations */
137	struct sembuf		*blocking; /* the operation that blocked */
138	int			nsops;	 /* number of operations */
139	bool			alter;	 /* does *sops alter the array? */
140	bool                    dupsop;	 /* sops on more than one sem_num */
141};
142
143/* Each task has a list of undo requests. They are executed automatically
144 * when the process exits.
145 */
146struct sem_undo {
147	struct list_head	list_proc;	/* per-process list: *
148						 * all undos from one process
149						 * rcu protected */
150	struct rcu_head		rcu;		/* rcu struct for sem_undo */
151	struct sem_undo_list	*ulp;		/* back ptr to sem_undo_list */
152	struct list_head	list_id;	/* per semaphore array list:
153						 * all undos for one array */
154	int			semid;		/* semaphore set identifier */
155	short			*semadj;	/* array of adjustments */
156						/* one per semaphore */
157};
158
159/* sem_undo_list controls shared access to the list of sem_undo structures
160 * that may be shared among all a CLONE_SYSVSEM task group.
161 */
162struct sem_undo_list {
163	refcount_t		refcnt;
164	spinlock_t		lock;
165	struct list_head	list_proc;
166};
167
168
169#define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
170
171static int newary(struct ipc_namespace *, struct ipc_params *);
172static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
173#ifdef CONFIG_PROC_FS
174static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
175#endif
176
177#define SEMMSL_FAST	256 /* 512 bytes on stack */
178#define SEMOPM_FAST	64  /* ~ 372 bytes on stack */
179
180/*
181 * Switching from the mode suitable for simple ops
182 * to the mode for complex ops is costly. Therefore:
183 * use some hysteresis
184 */
185#define USE_GLOBAL_LOCK_HYSTERESIS	10
186
187/*
188 * Locking:
189 * a) global sem_lock() for read/write
190 *	sem_undo.id_next,
191 *	sem_array.complex_count,
192 *	sem_array.pending{_alter,_const},
193 *	sem_array.sem_undo
194 *
195 * b) global or semaphore sem_lock() for read/write:
196 *	sem_array.sems[i].pending_{const,alter}:
197 *
198 * c) special:
199 *	sem_undo_list.list_proc:
200 *	* undo_list->lock for write
201 *	* rcu for read
202 *	use_global_lock:
203 *	* global sem_lock() for write
204 *	* either local or global sem_lock() for read.
205 *
206 * Memory ordering:
207 * Most ordering is enforced by using spin_lock() and spin_unlock().
208 * The special case is use_global_lock:
209 * Setting it from non-zero to 0 is a RELEASE, this is ensured by
210 * using smp_store_release().
211 * Testing if it is non-zero is an ACQUIRE, this is ensured by using
212 * smp_load_acquire().
213 * Setting it from 0 to non-zero must be ordered with regards to
214 * this smp_load_acquire(), this is guaranteed because the smp_load_acquire()
215 * is inside a spin_lock() and after a write from 0 to non-zero a
216 * spin_lock()+spin_unlock() is done.
217 */
218
219#define sc_semmsl	sem_ctls[0]
220#define sc_semmns	sem_ctls[1]
221#define sc_semopm	sem_ctls[2]
222#define sc_semmni	sem_ctls[3]
223
224void sem_init_ns(struct ipc_namespace *ns)
225{
226	ns->sc_semmsl = SEMMSL;
227	ns->sc_semmns = SEMMNS;
228	ns->sc_semopm = SEMOPM;
229	ns->sc_semmni = SEMMNI;
230	ns->used_sems = 0;
231	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
232}
233
234#ifdef CONFIG_IPC_NS
235void sem_exit_ns(struct ipc_namespace *ns)
236{
237	free_ipcs(ns, &sem_ids(ns), freeary);
238	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
239	rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht);
240}
241#endif
242
243void __init sem_init(void)
244{
245	sem_init_ns(&init_ipc_ns);
246	ipc_init_proc_interface("sysvipc/sem",
247				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
248				IPC_SEM_IDS, sysvipc_sem_proc_show);
249}
250
251/**
252 * unmerge_queues - unmerge queues, if possible.
253 * @sma: semaphore array
254 *
255 * The function unmerges the wait queues if complex_count is 0.
256 * It must be called prior to dropping the global semaphore array lock.
257 */
258static void unmerge_queues(struct sem_array *sma)
259{
260	struct sem_queue *q, *tq;
261
262	/* complex operations still around? */
263	if (sma->complex_count)
264		return;
265	/*
266	 * We will switch back to simple mode.
267	 * Move all pending operation back into the per-semaphore
268	 * queues.
269	 */
270	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
271		struct sem *curr;
272		curr = &sma->sems[q->sops[0].sem_num];
273
274		list_add_tail(&q->list, &curr->pending_alter);
275	}
276	INIT_LIST_HEAD(&sma->pending_alter);
277}
278
279/**
280 * merge_queues - merge single semop queues into global queue
281 * @sma: semaphore array
282 *
283 * This function merges all per-semaphore queues into the global queue.
284 * It is necessary to achieve FIFO ordering for the pending single-sop
285 * operations when a multi-semop operation must sleep.
286 * Only the alter operations must be moved, the const operations can stay.
287 */
288static void merge_queues(struct sem_array *sma)
289{
290	int i;
291	for (i = 0; i < sma->sem_nsems; i++) {
292		struct sem *sem = &sma->sems[i];
293
294		list_splice_init(&sem->pending_alter, &sma->pending_alter);
295	}
296}
297
298static void sem_rcu_free(struct rcu_head *head)
299{
300	struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
301	struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
302
303	security_sem_free(&sma->sem_perm);
304	kvfree(sma);
305}
306
307/*
308 * Enter the mode suitable for non-simple operations:
309 * Caller must own sem_perm.lock.
310 */
311static void complexmode_enter(struct sem_array *sma)
312{
313	int i;
314	struct sem *sem;
315
316	if (sma->use_global_lock > 0)  {
317		/*
318		 * We are already in global lock mode.
319		 * Nothing to do, just reset the
320		 * counter until we return to simple mode.
321		 */
322		sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
323		return;
324	}
325	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
326
327	for (i = 0; i < sma->sem_nsems; i++) {
328		sem = &sma->sems[i];
329		spin_lock(&sem->lock);
330		spin_unlock(&sem->lock);
331	}
332}
333
334/*
335 * Try to leave the mode that disallows simple operations:
336 * Caller must own sem_perm.lock.
337 */
338static void complexmode_tryleave(struct sem_array *sma)
339{
340	if (sma->complex_count)  {
341		/* Complex ops are sleeping.
342		 * We must stay in complex mode
343		 */
344		return;
345	}
346	if (sma->use_global_lock == 1) {
347		/*
348		 * Immediately after setting use_global_lock to 0,
349		 * a simple op can start. Thus: all memory writes
350		 * performed by the current operation must be visible
351		 * before we set use_global_lock to 0.
352		 */
353		smp_store_release(&sma->use_global_lock, 0);
354	} else {
355		sma->use_global_lock--;
356	}
357}
358
359#define SEM_GLOBAL_LOCK	(-1)
360/*
361 * If the request contains only one semaphore operation, and there are
362 * no complex transactions pending, lock only the semaphore involved.
363 * Otherwise, lock the entire semaphore array, since we either have
364 * multiple semaphores in our own semops, or we need to look at
365 * semaphores from other pending complex operations.
366 */
367static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
368			      int nsops)
369{
370	struct sem *sem;
371	int idx;
372
373	if (nsops != 1) {
374		/* Complex operation - acquire a full lock */
375		ipc_lock_object(&sma->sem_perm);
376
377		/* Prevent parallel simple ops */
378		complexmode_enter(sma);
379		return SEM_GLOBAL_LOCK;
380	}
381
382	/*
383	 * Only one semaphore affected - try to optimize locking.
384	 * Optimized locking is possible if no complex operation
385	 * is either enqueued or processed right now.
386	 *
387	 * Both facts are tracked by use_global_mode.
388	 */
389	idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
390	sem = &sma->sems[idx];
391
392	/*
393	 * Initial check for use_global_lock. Just an optimization,
394	 * no locking, no memory barrier.
395	 */
396	if (!sma->use_global_lock) {
397		/*
398		 * It appears that no complex operation is around.
399		 * Acquire the per-semaphore lock.
400		 */
401		spin_lock(&sem->lock);
402
403		/* pairs with smp_store_release() */
404		if (!smp_load_acquire(&sma->use_global_lock)) {
405			/* fast path successful! */
406			return sops->sem_num;
407		}
408		spin_unlock(&sem->lock);
409	}
410
411	/* slow path: acquire the full lock */
412	ipc_lock_object(&sma->sem_perm);
413
414	if (sma->use_global_lock == 0) {
415		/*
416		 * The use_global_lock mode ended while we waited for
417		 * sma->sem_perm.lock. Thus we must switch to locking
418		 * with sem->lock.
419		 * Unlike in the fast path, there is no need to recheck
420		 * sma->use_global_lock after we have acquired sem->lock:
421		 * We own sma->sem_perm.lock, thus use_global_lock cannot
422		 * change.
423		 */
424		spin_lock(&sem->lock);
425
426		ipc_unlock_object(&sma->sem_perm);
427		return sops->sem_num;
428	} else {
429		/*
430		 * Not a false alarm, thus continue to use the global lock
431		 * mode. No need for complexmode_enter(), this was done by
432		 * the caller that has set use_global_mode to non-zero.
433		 */
434		return SEM_GLOBAL_LOCK;
435	}
436}
437
438static inline void sem_unlock(struct sem_array *sma, int locknum)
439{
440	if (locknum == SEM_GLOBAL_LOCK) {
441		unmerge_queues(sma);
442		complexmode_tryleave(sma);
443		ipc_unlock_object(&sma->sem_perm);
444	} else {
445		struct sem *sem = &sma->sems[locknum];
446		spin_unlock(&sem->lock);
447	}
448}
449
450/*
451 * sem_lock_(check_) routines are called in the paths where the rwsem
452 * is not held.
453 *
454 * The caller holds the RCU read lock.
455 */
456static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
457{
458	struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
459
460	if (IS_ERR(ipcp))
461		return ERR_CAST(ipcp);
462
463	return container_of(ipcp, struct sem_array, sem_perm);
464}
465
466static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
467							int id)
468{
469	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
470
471	if (IS_ERR(ipcp))
472		return ERR_CAST(ipcp);
473
474	return container_of(ipcp, struct sem_array, sem_perm);
475}
476
477static inline void sem_lock_and_putref(struct sem_array *sma)
478{
479	sem_lock(sma, NULL, -1);
480	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
481}
482
483static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
484{
485	ipc_rmid(&sem_ids(ns), &s->sem_perm);
486}
487
488static struct sem_array *sem_alloc(size_t nsems)
489{
490	struct sem_array *sma;
491	size_t size;
492
493	if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
494		return NULL;
495
496	size = sizeof(*sma) + nsems * sizeof(sma->sems[0]);
497	sma = kvmalloc(size, GFP_KERNEL);
498	if (unlikely(!sma))
499		return NULL;
500
501	memset(sma, 0, size);
502
503	return sma;
504}
505
506/**
507 * newary - Create a new semaphore set
508 * @ns: namespace
509 * @params: ptr to the structure that contains key, semflg and nsems
510 *
511 * Called with sem_ids.rwsem held (as a writer)
512 */
513static int newary(struct ipc_namespace *ns, struct ipc_params *params)
514{
515	int retval;
516	struct sem_array *sma;
517	key_t key = params->key;
518	int nsems = params->u.nsems;
519	int semflg = params->flg;
520	int i;
521
522	if (!nsems)
523		return -EINVAL;
524	if (ns->used_sems + nsems > ns->sc_semmns)
525		return -ENOSPC;
526
527	sma = sem_alloc(nsems);
528	if (!sma)
529		return -ENOMEM;
530
531	sma->sem_perm.mode = (semflg & S_IRWXUGO);
532	sma->sem_perm.key = key;
533
534	sma->sem_perm.security = NULL;
535	retval = security_sem_alloc(&sma->sem_perm);
536	if (retval) {
537		kvfree(sma);
538		return retval;
539	}
540
541	for (i = 0; i < nsems; i++) {
542		INIT_LIST_HEAD(&sma->sems[i].pending_alter);
543		INIT_LIST_HEAD(&sma->sems[i].pending_const);
544		spin_lock_init(&sma->sems[i].lock);
545	}
546
547	sma->complex_count = 0;
548	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
549	INIT_LIST_HEAD(&sma->pending_alter);
550	INIT_LIST_HEAD(&sma->pending_const);
551	INIT_LIST_HEAD(&sma->list_id);
552	sma->sem_nsems = nsems;
553	sma->sem_ctime = ktime_get_real_seconds();
554
555	/* ipc_addid() locks sma upon success. */
556	retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
557	if (retval < 0) {
558		ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
559		return retval;
560	}
561	ns->used_sems += nsems;
562
563	sem_unlock(sma, -1);
564	rcu_read_unlock();
565
566	return sma->sem_perm.id;
567}
568
569
570/*
571 * Called with sem_ids.rwsem and ipcp locked.
572 */
573static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
574				struct ipc_params *params)
575{
576	struct sem_array *sma;
577
578	sma = container_of(ipcp, struct sem_array, sem_perm);
579	if (params->u.nsems > sma->sem_nsems)
580		return -EINVAL;
581
582	return 0;
583}
584
585long ksys_semget(key_t key, int nsems, int semflg)
586{
587	struct ipc_namespace *ns;
588	static const struct ipc_ops sem_ops = {
589		.getnew = newary,
590		.associate = security_sem_associate,
591		.more_checks = sem_more_checks,
592	};
593	struct ipc_params sem_params;
594
595	ns = current->nsproxy->ipc_ns;
596
597	if (nsems < 0 || nsems > ns->sc_semmsl)
598		return -EINVAL;
599
600	sem_params.key = key;
601	sem_params.flg = semflg;
602	sem_params.u.nsems = nsems;
603
604	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
605}
606
607SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
608{
609	return ksys_semget(key, nsems, semflg);
610}
611
612/**
613 * perform_atomic_semop[_slow] - Attempt to perform semaphore
614 *                               operations on a given array.
615 * @sma: semaphore array
616 * @q: struct sem_queue that describes the operation
617 *
618 * Caller blocking are as follows, based the value
619 * indicated by the semaphore operation (sem_op):
620 *
621 *  (1) >0 never blocks.
622 *  (2)  0 (wait-for-zero operation): semval is non-zero.
623 *  (3) <0 attempting to decrement semval to a value smaller than zero.
624 *
625 * Returns 0 if the operation was possible.
626 * Returns 1 if the operation is impossible, the caller must sleep.
627 * Returns <0 for error codes.
628 */
629static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
630{
631	int result, sem_op, nsops;
632	struct pid *pid;
633	struct sembuf *sop;
634	struct sem *curr;
635	struct sembuf *sops;
636	struct sem_undo *un;
637
638	sops = q->sops;
639	nsops = q->nsops;
640	un = q->undo;
641
642	for (sop = sops; sop < sops + nsops; sop++) {
643		int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
644		curr = &sma->sems[idx];
645		sem_op = sop->sem_op;
646		result = curr->semval;
647
648		if (!sem_op && result)
649			goto would_block;
650
651		result += sem_op;
652		if (result < 0)
653			goto would_block;
654		if (result > SEMVMX)
655			goto out_of_range;
656
657		if (sop->sem_flg & SEM_UNDO) {
658			int undo = un->semadj[sop->sem_num] - sem_op;
659			/* Exceeding the undo range is an error. */
660			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
661				goto out_of_range;
662			un->semadj[sop->sem_num] = undo;
663		}
664
665		curr->semval = result;
666	}
667
668	sop--;
669	pid = q->pid;
670	while (sop >= sops) {
671		ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid);
672		sop--;
673	}
674
675	return 0;
676
677out_of_range:
678	result = -ERANGE;
679	goto undo;
680
681would_block:
682	q->blocking = sop;
683
684	if (sop->sem_flg & IPC_NOWAIT)
685		result = -EAGAIN;
686	else
687		result = 1;
688
689undo:
690	sop--;
691	while (sop >= sops) {
692		sem_op = sop->sem_op;
693		sma->sems[sop->sem_num].semval -= sem_op;
694		if (sop->sem_flg & SEM_UNDO)
695			un->semadj[sop->sem_num] += sem_op;
696		sop--;
697	}
698
699	return result;
700}
701
702static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
703{
704	int result, sem_op, nsops;
705	struct sembuf *sop;
706	struct sem *curr;
707	struct sembuf *sops;
708	struct sem_undo *un;
709
710	sops = q->sops;
711	nsops = q->nsops;
712	un = q->undo;
713
714	if (unlikely(q->dupsop))
715		return perform_atomic_semop_slow(sma, q);
716
717	/*
718	 * We scan the semaphore set twice, first to ensure that the entire
719	 * operation can succeed, therefore avoiding any pointless writes
720	 * to shared memory and having to undo such changes in order to block
721	 * until the operations can go through.
722	 */
723	for (sop = sops; sop < sops + nsops; sop++) {
724		int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
725
726		curr = &sma->sems[idx];
727		sem_op = sop->sem_op;
728		result = curr->semval;
729
730		if (!sem_op && result)
731			goto would_block; /* wait-for-zero */
732
733		result += sem_op;
734		if (result < 0)
735			goto would_block;
736
737		if (result > SEMVMX)
738			return -ERANGE;
739
740		if (sop->sem_flg & SEM_UNDO) {
741			int undo = un->semadj[sop->sem_num] - sem_op;
742
743			/* Exceeding the undo range is an error. */
744			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
745				return -ERANGE;
746		}
747	}
748
749	for (sop = sops; sop < sops + nsops; sop++) {
750		curr = &sma->sems[sop->sem_num];
751		sem_op = sop->sem_op;
752		result = curr->semval;
753
754		if (sop->sem_flg & SEM_UNDO) {
755			int undo = un->semadj[sop->sem_num] - sem_op;
756
757			un->semadj[sop->sem_num] = undo;
758		}
759		curr->semval += sem_op;
760		ipc_update_pid(&curr->sempid, q->pid);
761	}
762
763	return 0;
764
765would_block:
766	q->blocking = sop;
767	return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
768}
769
770static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
771					     struct wake_q_head *wake_q)
772{
773	wake_q_add(wake_q, q->sleeper);
774	/*
775	 * Rely on the above implicit barrier, such that we can
776	 * ensure that we hold reference to the task before setting
777	 * q->status. Otherwise we could race with do_exit if the
778	 * task is awoken by an external event before calling
779	 * wake_up_process().
780	 */
781	WRITE_ONCE(q->status, error);
782}
783
784static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
785{
786	list_del(&q->list);
787	if (q->nsops > 1)
788		sma->complex_count--;
789}
790
791/** check_restart(sma, q)
792 * @sma: semaphore array
793 * @q: the operation that just completed
794 *
795 * update_queue is O(N^2) when it restarts scanning the whole queue of
796 * waiting operations. Therefore this function checks if the restart is
797 * really necessary. It is called after a previously waiting operation
798 * modified the array.
799 * Note that wait-for-zero operations are handled without restart.
800 */
801static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
802{
803	/* pending complex alter operations are too difficult to analyse */
804	if (!list_empty(&sma->pending_alter))
805		return 1;
806
807	/* we were a sleeping complex operation. Too difficult */
808	if (q->nsops > 1)
809		return 1;
810
811	/* It is impossible that someone waits for the new value:
812	 * - complex operations always restart.
813	 * - wait-for-zero are handled seperately.
814	 * - q is a previously sleeping simple operation that
815	 *   altered the array. It must be a decrement, because
816	 *   simple increments never sleep.
817	 * - If there are older (higher priority) decrements
818	 *   in the queue, then they have observed the original
819	 *   semval value and couldn't proceed. The operation
820	 *   decremented to value - thus they won't proceed either.
821	 */
822	return 0;
823}
824
825/**
826 * wake_const_ops - wake up non-alter tasks
827 * @sma: semaphore array.
828 * @semnum: semaphore that was modified.
829 * @wake_q: lockless wake-queue head.
830 *
831 * wake_const_ops must be called after a semaphore in a semaphore array
832 * was set to 0. If complex const operations are pending, wake_const_ops must
833 * be called with semnum = -1, as well as with the number of each modified
834 * semaphore.
835 * The tasks that must be woken up are added to @wake_q. The return code
836 * is stored in q->pid.
837 * The function returns 1 if at least one operation was completed successfully.
838 */
839static int wake_const_ops(struct sem_array *sma, int semnum,
840			  struct wake_q_head *wake_q)
841{
842	struct sem_queue *q, *tmp;
843	struct list_head *pending_list;
844	int semop_completed = 0;
845
846	if (semnum == -1)
847		pending_list = &sma->pending_const;
848	else
849		pending_list = &sma->sems[semnum].pending_const;
850
851	list_for_each_entry_safe(q, tmp, pending_list, list) {
852		int error = perform_atomic_semop(sma, q);
853
854		if (error > 0)
855			continue;
856		/* operation completed, remove from queue & wakeup */
857		unlink_queue(sma, q);
858
859		wake_up_sem_queue_prepare(q, error, wake_q);
860		if (error == 0)
861			semop_completed = 1;
862	}
863
864	return semop_completed;
865}
866
867/**
868 * do_smart_wakeup_zero - wakeup all wait for zero tasks
869 * @sma: semaphore array
870 * @sops: operations that were performed
871 * @nsops: number of operations
872 * @wake_q: lockless wake-queue head
873 *
874 * Checks all required queue for wait-for-zero operations, based
875 * on the actual changes that were performed on the semaphore array.
876 * The function returns 1 if at least one operation was completed successfully.
877 */
878static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
879				int nsops, struct wake_q_head *wake_q)
880{
881	int i;
882	int semop_completed = 0;
883	int got_zero = 0;
884
885	/* first: the per-semaphore queues, if known */
886	if (sops) {
887		for (i = 0; i < nsops; i++) {
888			int num = sops[i].sem_num;
889
890			if (sma->sems[num].semval == 0) {
891				got_zero = 1;
892				semop_completed |= wake_const_ops(sma, num, wake_q);
893			}
894		}
895	} else {
896		/*
897		 * No sops means modified semaphores not known.
898		 * Assume all were changed.
899		 */
900		for (i = 0; i < sma->sem_nsems; i++) {
901			if (sma->sems[i].semval == 0) {
902				got_zero = 1;
903				semop_completed |= wake_const_ops(sma, i, wake_q);
904			}
905		}
906	}
907	/*
908	 * If one of the modified semaphores got 0,
909	 * then check the global queue, too.
910	 */
911	if (got_zero)
912		semop_completed |= wake_const_ops(sma, -1, wake_q);
913
914	return semop_completed;
915}
916
917
918/**
919 * update_queue - look for tasks that can be completed.
920 * @sma: semaphore array.
921 * @semnum: semaphore that was modified.
922 * @wake_q: lockless wake-queue head.
923 *
924 * update_queue must be called after a semaphore in a semaphore array
925 * was modified. If multiple semaphores were modified, update_queue must
926 * be called with semnum = -1, as well as with the number of each modified
927 * semaphore.
928 * The tasks that must be woken up are added to @wake_q. The return code
929 * is stored in q->pid.
930 * The function internally checks if const operations can now succeed.
931 *
932 * The function return 1 if at least one semop was completed successfully.
933 */
934static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
935{
936	struct sem_queue *q, *tmp;
937	struct list_head *pending_list;
938	int semop_completed = 0;
939
940	if (semnum == -1)
941		pending_list = &sma->pending_alter;
942	else
943		pending_list = &sma->sems[semnum].pending_alter;
944
945again:
946	list_for_each_entry_safe(q, tmp, pending_list, list) {
947		int error, restart;
948
949		/* If we are scanning the single sop, per-semaphore list of
950		 * one semaphore and that semaphore is 0, then it is not
951		 * necessary to scan further: simple increments
952		 * that affect only one entry succeed immediately and cannot
953		 * be in the  per semaphore pending queue, and decrements
954		 * cannot be successful if the value is already 0.
955		 */
956		if (semnum != -1 && sma->sems[semnum].semval == 0)
957			break;
958
959		error = perform_atomic_semop(sma, q);
960
961		/* Does q->sleeper still need to sleep? */
962		if (error > 0)
963			continue;
964
965		unlink_queue(sma, q);
966
967		if (error) {
968			restart = 0;
969		} else {
970			semop_completed = 1;
971			do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
972			restart = check_restart(sma, q);
973		}
974
975		wake_up_sem_queue_prepare(q, error, wake_q);
976		if (restart)
977			goto again;
978	}
979	return semop_completed;
980}
981
982/**
983 * set_semotime - set sem_otime
984 * @sma: semaphore array
985 * @sops: operations that modified the array, may be NULL
986 *
987 * sem_otime is replicated to avoid cache line trashing.
988 * This function sets one instance to the current time.
989 */
990static void set_semotime(struct sem_array *sma, struct sembuf *sops)
991{
992	if (sops == NULL) {
993		sma->sems[0].sem_otime = ktime_get_real_seconds();
994	} else {
995		sma->sems[sops[0].sem_num].sem_otime =
996						ktime_get_real_seconds();
997	}
998}
999
1000/**
1001 * do_smart_update - optimized update_queue
1002 * @sma: semaphore array
1003 * @sops: operations that were performed
1004 * @nsops: number of operations
1005 * @otime: force setting otime
1006 * @wake_q: lockless wake-queue head
1007 *
1008 * do_smart_update() does the required calls to update_queue and wakeup_zero,
1009 * based on the actual changes that were performed on the semaphore array.
1010 * Note that the function does not do the actual wake-up: the caller is
1011 * responsible for calling wake_up_q().
1012 * It is safe to perform this call after dropping all locks.
1013 */
1014static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
1015			    int otime, struct wake_q_head *wake_q)
1016{
1017	int i;
1018
1019	otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
1020
1021	if (!list_empty(&sma->pending_alter)) {
1022		/* semaphore array uses the global queue - just process it. */
1023		otime |= update_queue(sma, -1, wake_q);
1024	} else {
1025		if (!sops) {
1026			/*
1027			 * No sops, thus the modified semaphores are not
1028			 * known. Check all.
1029			 */
1030			for (i = 0; i < sma->sem_nsems; i++)
1031				otime |= update_queue(sma, i, wake_q);
1032		} else {
1033			/*
1034			 * Check the semaphores that were increased:
1035			 * - No complex ops, thus all sleeping ops are
1036			 *   decrease.
1037			 * - if we decreased the value, then any sleeping
1038			 *   semaphore ops wont be able to run: If the
1039			 *   previous value was too small, then the new
1040			 *   value will be too small, too.
1041			 */
1042			for (i = 0; i < nsops; i++) {
1043				if (sops[i].sem_op > 0) {
1044					otime |= update_queue(sma,
1045							      sops[i].sem_num, wake_q);
1046				}
1047			}
1048		}
1049	}
1050	if (otime)
1051		set_semotime(sma, sops);
1052}
1053
1054/*
1055 * check_qop: Test if a queued operation sleeps on the semaphore semnum
1056 */
1057static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1058			bool count_zero)
1059{
1060	struct sembuf *sop = q->blocking;
1061
1062	/*
1063	 * Linux always (since 0.99.10) reported a task as sleeping on all
1064	 * semaphores. This violates SUS, therefore it was changed to the
1065	 * standard compliant behavior.
1066	 * Give the administrators a chance to notice that an application
1067	 * might misbehave because it relies on the Linux behavior.
1068	 */
1069	pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1070			"The task %s (%d) triggered the difference, watch for misbehavior.\n",
1071			current->comm, task_pid_nr(current));
1072
1073	if (sop->sem_num != semnum)
1074		return 0;
1075
1076	if (count_zero && sop->sem_op == 0)
1077		return 1;
1078	if (!count_zero && sop->sem_op < 0)
1079		return 1;
1080
1081	return 0;
1082}
1083
1084/* The following counts are associated to each semaphore:
1085 *   semncnt        number of tasks waiting on semval being nonzero
1086 *   semzcnt        number of tasks waiting on semval being zero
1087 *
1088 * Per definition, a task waits only on the semaphore of the first semop
1089 * that cannot proceed, even if additional operation would block, too.
1090 */
1091static int count_semcnt(struct sem_array *sma, ushort semnum,
1092			bool count_zero)
1093{
1094	struct list_head *l;
1095	struct sem_queue *q;
1096	int semcnt;
1097
1098	semcnt = 0;
1099	/* First: check the simple operations. They are easy to evaluate */
1100	if (count_zero)
1101		l = &sma->sems[semnum].pending_const;
1102	else
1103		l = &sma->sems[semnum].pending_alter;
1104
1105	list_for_each_entry(q, l, list) {
1106		/* all task on a per-semaphore list sleep on exactly
1107		 * that semaphore
1108		 */
1109		semcnt++;
1110	}
1111
1112	/* Then: check the complex operations. */
1113	list_for_each_entry(q, &sma->pending_alter, list) {
1114		semcnt += check_qop(sma, semnum, q, count_zero);
1115	}
1116	if (count_zero) {
1117		list_for_each_entry(q, &sma->pending_const, list) {
1118			semcnt += check_qop(sma, semnum, q, count_zero);
1119		}
1120	}
1121	return semcnt;
1122}
1123
1124/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1125 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1126 * remains locked on exit.
1127 */
1128static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1129{
1130	struct sem_undo *un, *tu;
1131	struct sem_queue *q, *tq;
1132	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1133	int i;
1134	DEFINE_WAKE_Q(wake_q);
1135
1136	/* Free the existing undo structures for this semaphore set.  */
1137	ipc_assert_locked_object(&sma->sem_perm);
1138	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1139		list_del(&un->list_id);
1140		spin_lock(&un->ulp->lock);
1141		un->semid = -1;
1142		list_del_rcu(&un->list_proc);
1143		spin_unlock(&un->ulp->lock);
1144		kfree_rcu(un, rcu);
1145	}
1146
1147	/* Wake up all pending processes and let them fail with EIDRM. */
1148	list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1149		unlink_queue(sma, q);
1150		wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1151	}
1152
1153	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1154		unlink_queue(sma, q);
1155		wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1156	}
1157	for (i = 0; i < sma->sem_nsems; i++) {
1158		struct sem *sem = &sma->sems[i];
1159		list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1160			unlink_queue(sma, q);
1161			wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1162		}
1163		list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1164			unlink_queue(sma, q);
1165			wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1166		}
1167		ipc_update_pid(&sem->sempid, NULL);
1168	}
1169
1170	/* Remove the semaphore set from the IDR */
1171	sem_rmid(ns, sma);
1172	sem_unlock(sma, -1);
1173	rcu_read_unlock();
1174
1175	wake_up_q(&wake_q);
1176	ns->used_sems -= sma->sem_nsems;
1177	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1178}
1179
1180static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1181{
1182	switch (version) {
1183	case IPC_64:
1184		return copy_to_user(buf, in, sizeof(*in));
1185	case IPC_OLD:
1186	    {
1187		struct semid_ds out;
1188
1189		memset(&out, 0, sizeof(out));
1190
1191		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1192
1193		out.sem_otime	= in->sem_otime;
1194		out.sem_ctime	= in->sem_ctime;
1195		out.sem_nsems	= in->sem_nsems;
1196
1197		return copy_to_user(buf, &out, sizeof(out));
1198	    }
1199	default:
1200		return -EINVAL;
1201	}
1202}
1203
1204static time64_t get_semotime(struct sem_array *sma)
1205{
1206	int i;
1207	time64_t res;
1208
1209	res = sma->sems[0].sem_otime;
1210	for (i = 1; i < sma->sem_nsems; i++) {
1211		time64_t to = sma->sems[i].sem_otime;
1212
1213		if (to > res)
1214			res = to;
1215	}
1216	return res;
1217}
1218
1219static int semctl_stat(struct ipc_namespace *ns, int semid,
1220			 int cmd, struct semid64_ds *semid64)
1221{
1222	struct sem_array *sma;
1223	time64_t semotime;
1224	int err;
1225
1226	memset(semid64, 0, sizeof(*semid64));
1227
1228	rcu_read_lock();
1229	if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) {
1230		sma = sem_obtain_object(ns, semid);
1231		if (IS_ERR(sma)) {
1232			err = PTR_ERR(sma);
1233			goto out_unlock;
1234		}
1235	} else { /* IPC_STAT */
1236		sma = sem_obtain_object_check(ns, semid);
1237		if (IS_ERR(sma)) {
1238			err = PTR_ERR(sma);
1239			goto out_unlock;
1240		}
1241	}
1242
1243	/* see comment for SHM_STAT_ANY */
1244	if (cmd == SEM_STAT_ANY)
1245		audit_ipc_obj(&sma->sem_perm);
1246	else {
1247		err = -EACCES;
1248		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1249			goto out_unlock;
1250	}
1251
1252	err = security_sem_semctl(&sma->sem_perm, cmd);
1253	if (err)
1254		goto out_unlock;
1255
1256	ipc_lock_object(&sma->sem_perm);
1257
1258	if (!ipc_valid_object(&sma->sem_perm)) {
1259		ipc_unlock_object(&sma->sem_perm);
1260		err = -EIDRM;
1261		goto out_unlock;
1262	}
1263
1264	kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
1265	semotime = get_semotime(sma);
1266	semid64->sem_otime = semotime;
1267	semid64->sem_ctime = sma->sem_ctime;
1268#ifndef CONFIG_64BIT
1269	semid64->sem_otime_high = semotime >> 32;
1270	semid64->sem_ctime_high = sma->sem_ctime >> 32;
1271#endif
1272	semid64->sem_nsems = sma->sem_nsems;
1273
1274	if (cmd == IPC_STAT) {
1275		/*
1276		 * As defined in SUS:
1277		 * Return 0 on success
1278		 */
1279		err = 0;
1280	} else {
1281		/*
1282		 * SEM_STAT and SEM_STAT_ANY (both Linux specific)
1283		 * Return the full id, including the sequence number
1284		 */
1285		err = sma->sem_perm.id;
1286	}
1287	ipc_unlock_object(&sma->sem_perm);
1288out_unlock:
1289	rcu_read_unlock();
1290	return err;
1291}
1292
1293static int semctl_info(struct ipc_namespace *ns, int semid,
1294			 int cmd, void __user *p)
1295{
1296	struct seminfo seminfo;
1297	int max_id;
1298	int err;
1299
1300	err = security_sem_semctl(NULL, cmd);
1301	if (err)
1302		return err;
1303
1304	memset(&seminfo, 0, sizeof(seminfo));
1305	seminfo.semmni = ns->sc_semmni;
1306	seminfo.semmns = ns->sc_semmns;
1307	seminfo.semmsl = ns->sc_semmsl;
1308	seminfo.semopm = ns->sc_semopm;
1309	seminfo.semvmx = SEMVMX;
1310	seminfo.semmnu = SEMMNU;
1311	seminfo.semmap = SEMMAP;
1312	seminfo.semume = SEMUME;
1313	down_read(&sem_ids(ns).rwsem);
1314	if (cmd == SEM_INFO) {
1315		seminfo.semusz = sem_ids(ns).in_use;
1316		seminfo.semaem = ns->used_sems;
1317	} else {
1318		seminfo.semusz = SEMUSZ;
1319		seminfo.semaem = SEMAEM;
1320	}
1321	max_id = ipc_get_maxid(&sem_ids(ns));
1322	up_read(&sem_ids(ns).rwsem);
1323	if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1324		return -EFAULT;
1325	return (max_id < 0) ? 0 : max_id;
1326}
1327
1328static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1329		int val)
1330{
1331	struct sem_undo *un;
1332	struct sem_array *sma;
1333	struct sem *curr;
1334	int err;
1335	DEFINE_WAKE_Q(wake_q);
1336
1337	if (val > SEMVMX || val < 0)
1338		return -ERANGE;
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	if (semnum < 0 || semnum >= sma->sem_nsems) {
1348		rcu_read_unlock();
1349		return -EINVAL;
1350	}
1351
1352
1353	if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1354		rcu_read_unlock();
1355		return -EACCES;
1356	}
1357
1358	err = security_sem_semctl(&sma->sem_perm, SETVAL);
1359	if (err) {
1360		rcu_read_unlock();
1361		return -EACCES;
1362	}
1363
1364	sem_lock(sma, NULL, -1);
1365
1366	if (!ipc_valid_object(&sma->sem_perm)) {
1367		sem_unlock(sma, -1);
1368		rcu_read_unlock();
1369		return -EIDRM;
1370	}
1371
1372	semnum = array_index_nospec(semnum, sma->sem_nsems);
1373	curr = &sma->sems[semnum];
1374
1375	ipc_assert_locked_object(&sma->sem_perm);
1376	list_for_each_entry(un, &sma->list_id, list_id)
1377		un->semadj[semnum] = 0;
1378
1379	curr->semval = val;
1380	ipc_update_pid(&curr->sempid, task_tgid(current));
1381	sma->sem_ctime = ktime_get_real_seconds();
1382	/* maybe some queued-up processes were waiting for this */
1383	do_smart_update(sma, NULL, 0, 0, &wake_q);
1384	sem_unlock(sma, -1);
1385	rcu_read_unlock();
1386	wake_up_q(&wake_q);
1387	return 0;
1388}
1389
1390static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1391		int cmd, void __user *p)
1392{
1393	struct sem_array *sma;
1394	struct sem *curr;
1395	int err, nsems;
1396	ushort fast_sem_io[SEMMSL_FAST];
1397	ushort *sem_io = fast_sem_io;
1398	DEFINE_WAKE_Q(wake_q);
1399
1400	rcu_read_lock();
1401	sma = sem_obtain_object_check(ns, semid);
1402	if (IS_ERR(sma)) {
1403		rcu_read_unlock();
1404		return PTR_ERR(sma);
1405	}
1406
1407	nsems = sma->sem_nsems;
1408
1409	err = -EACCES;
1410	if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1411		goto out_rcu_wakeup;
1412
1413	err = security_sem_semctl(&sma->sem_perm, cmd);
1414	if (err)
1415		goto out_rcu_wakeup;
1416
1417	err = -EACCES;
1418	switch (cmd) {
1419	case GETALL:
1420	{
1421		ushort __user *array = p;
1422		int i;
1423
1424		sem_lock(sma, NULL, -1);
1425		if (!ipc_valid_object(&sma->sem_perm)) {
1426			err = -EIDRM;
1427			goto out_unlock;
1428		}
1429		if (nsems > SEMMSL_FAST) {
1430			if (!ipc_rcu_getref(&sma->sem_perm)) {
1431				err = -EIDRM;
1432				goto out_unlock;
1433			}
1434			sem_unlock(sma, -1);
1435			rcu_read_unlock();
1436			sem_io = kvmalloc_array(nsems, sizeof(ushort),
1437						GFP_KERNEL);
1438			if (sem_io == NULL) {
1439				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1440				return -ENOMEM;
1441			}
1442
1443			rcu_read_lock();
1444			sem_lock_and_putref(sma);
1445			if (!ipc_valid_object(&sma->sem_perm)) {
1446				err = -EIDRM;
1447				goto out_unlock;
1448			}
1449		}
1450		for (i = 0; i < sma->sem_nsems; i++)
1451			sem_io[i] = sma->sems[i].semval;
1452		sem_unlock(sma, -1);
1453		rcu_read_unlock();
1454		err = 0;
1455		if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1456			err = -EFAULT;
1457		goto out_free;
1458	}
1459	case SETALL:
1460	{
1461		int i;
1462		struct sem_undo *un;
1463
1464		if (!ipc_rcu_getref(&sma->sem_perm)) {
1465			err = -EIDRM;
1466			goto out_rcu_wakeup;
1467		}
1468		rcu_read_unlock();
1469
1470		if (nsems > SEMMSL_FAST) {
1471			sem_io = kvmalloc_array(nsems, sizeof(ushort),
1472						GFP_KERNEL);
1473			if (sem_io == NULL) {
1474				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1475				return -ENOMEM;
1476			}
1477		}
1478
1479		if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1480			ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1481			err = -EFAULT;
1482			goto out_free;
1483		}
1484
1485		for (i = 0; i < nsems; i++) {
1486			if (sem_io[i] > SEMVMX) {
1487				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1488				err = -ERANGE;
1489				goto out_free;
1490			}
1491		}
1492		rcu_read_lock();
1493		sem_lock_and_putref(sma);
1494		if (!ipc_valid_object(&sma->sem_perm)) {
1495			err = -EIDRM;
1496			goto out_unlock;
1497		}
1498
1499		for (i = 0; i < nsems; i++) {
1500			sma->sems[i].semval = sem_io[i];
1501			ipc_update_pid(&sma->sems[i].sempid, task_tgid(current));
1502		}
1503
1504		ipc_assert_locked_object(&sma->sem_perm);
1505		list_for_each_entry(un, &sma->list_id, list_id) {
1506			for (i = 0; i < nsems; i++)
1507				un->semadj[i] = 0;
1508		}
1509		sma->sem_ctime = ktime_get_real_seconds();
1510		/* maybe some queued-up processes were waiting for this */
1511		do_smart_update(sma, NULL, 0, 0, &wake_q);
1512		err = 0;
1513		goto out_unlock;
1514	}
1515	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1516	}
1517	err = -EINVAL;
1518	if (semnum < 0 || semnum >= nsems)
1519		goto out_rcu_wakeup;
1520
1521	sem_lock(sma, NULL, -1);
1522	if (!ipc_valid_object(&sma->sem_perm)) {
1523		err = -EIDRM;
1524		goto out_unlock;
1525	}
1526
1527	semnum = array_index_nospec(semnum, nsems);
1528	curr = &sma->sems[semnum];
1529
1530	switch (cmd) {
1531	case GETVAL:
1532		err = curr->semval;
1533		goto out_unlock;
1534	case GETPID:
1535		err = pid_vnr(curr->sempid);
1536		goto out_unlock;
1537	case GETNCNT:
1538		err = count_semcnt(sma, semnum, 0);
1539		goto out_unlock;
1540	case GETZCNT:
1541		err = count_semcnt(sma, semnum, 1);
1542		goto out_unlock;
1543	}
1544
1545out_unlock:
1546	sem_unlock(sma, -1);
1547out_rcu_wakeup:
1548	rcu_read_unlock();
1549	wake_up_q(&wake_q);
1550out_free:
1551	if (sem_io != fast_sem_io)
1552		kvfree(sem_io);
1553	return err;
1554}
1555
1556static inline unsigned long
1557copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1558{
1559	switch (version) {
1560	case IPC_64:
1561		if (copy_from_user(out, buf, sizeof(*out)))
1562			return -EFAULT;
1563		return 0;
1564	case IPC_OLD:
1565	    {
1566		struct semid_ds tbuf_old;
1567
1568		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1569			return -EFAULT;
1570
1571		out->sem_perm.uid	= tbuf_old.sem_perm.uid;
1572		out->sem_perm.gid	= tbuf_old.sem_perm.gid;
1573		out->sem_perm.mode	= tbuf_old.sem_perm.mode;
1574
1575		return 0;
1576	    }
1577	default:
1578		return -EINVAL;
1579	}
1580}
1581
1582/*
1583 * This function handles some semctl commands which require the rwsem
1584 * to be held in write mode.
1585 * NOTE: no locks must be held, the rwsem is taken inside this function.
1586 */
1587static int semctl_down(struct ipc_namespace *ns, int semid,
1588		       int cmd, struct semid64_ds *semid64)
1589{
1590	struct sem_array *sma;
1591	int err;
1592	struct kern_ipc_perm *ipcp;
1593
1594	down_write(&sem_ids(ns).rwsem);
1595	rcu_read_lock();
1596
1597	ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
1598				      &semid64->sem_perm, 0);
1599	if (IS_ERR(ipcp)) {
1600		err = PTR_ERR(ipcp);
1601		goto out_unlock1;
1602	}
1603
1604	sma = container_of(ipcp, struct sem_array, sem_perm);
1605
1606	err = security_sem_semctl(&sma->sem_perm, cmd);
1607	if (err)
1608		goto out_unlock1;
1609
1610	switch (cmd) {
1611	case IPC_RMID:
1612		sem_lock(sma, NULL, -1);
1613		/* freeary unlocks the ipc object and rcu */
1614		freeary(ns, ipcp);
1615		goto out_up;
1616	case IPC_SET:
1617		sem_lock(sma, NULL, -1);
1618		err = ipc_update_perm(&semid64->sem_perm, ipcp);
1619		if (err)
1620			goto out_unlock0;
1621		sma->sem_ctime = ktime_get_real_seconds();
1622		break;
1623	default:
1624		err = -EINVAL;
1625		goto out_unlock1;
1626	}
1627
1628out_unlock0:
1629	sem_unlock(sma, -1);
1630out_unlock1:
1631	rcu_read_unlock();
1632out_up:
1633	up_write(&sem_ids(ns).rwsem);
1634	return err;
1635}
1636
1637long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg)
1638{
1639	int version;
1640	struct ipc_namespace *ns;
1641	void __user *p = (void __user *)arg;
1642	struct semid64_ds semid64;
1643	int err;
1644
1645	if (semid < 0)
1646		return -EINVAL;
1647
1648	version = ipc_parse_version(&cmd);
1649	ns = current->nsproxy->ipc_ns;
1650
1651	switch (cmd) {
1652	case IPC_INFO:
1653	case SEM_INFO:
1654		return semctl_info(ns, semid, cmd, p);
1655	case IPC_STAT:
1656	case SEM_STAT:
1657	case SEM_STAT_ANY:
1658		err = semctl_stat(ns, semid, cmd, &semid64);
1659		if (err < 0)
1660			return err;
1661		if (copy_semid_to_user(p, &semid64, version))
1662			err = -EFAULT;
1663		return err;
1664	case GETALL:
1665	case GETVAL:
1666	case GETPID:
1667	case GETNCNT:
1668	case GETZCNT:
1669	case SETALL:
1670		return semctl_main(ns, semid, semnum, cmd, p);
1671	case SETVAL: {
1672		int val;
1673#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1674		/* big-endian 64bit */
1675		val = arg >> 32;
1676#else
1677		/* 32bit or little-endian 64bit */
1678		val = arg;
1679#endif
1680		return semctl_setval(ns, semid, semnum, val);
1681	}
1682	case IPC_SET:
1683		if (copy_semid_from_user(&semid64, p, version))
1684			return -EFAULT;
1685	case IPC_RMID:
1686		return semctl_down(ns, semid, cmd, &semid64);
1687	default:
1688		return -EINVAL;
1689	}
1690}
1691
1692SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1693{
1694	return ksys_semctl(semid, semnum, cmd, arg);
1695}
1696
1697#ifdef CONFIG_COMPAT
1698
1699struct compat_semid_ds {
1700	struct compat_ipc_perm sem_perm;
1701	compat_time_t sem_otime;
1702	compat_time_t sem_ctime;
1703	compat_uptr_t sem_base;
1704	compat_uptr_t sem_pending;
1705	compat_uptr_t sem_pending_last;
1706	compat_uptr_t undo;
1707	unsigned short sem_nsems;
1708};
1709
1710static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf,
1711					int version)
1712{
1713	memset(out, 0, sizeof(*out));
1714	if (version == IPC_64) {
1715		struct compat_semid64_ds __user *p = buf;
1716		return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm);
1717	} else {
1718		struct compat_semid_ds __user *p = buf;
1719		return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm);
1720	}
1721}
1722
1723static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in,
1724					int version)
1725{
1726	if (version == IPC_64) {
1727		struct compat_semid64_ds v;
1728		memset(&v, 0, sizeof(v));
1729		to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm);
1730		v.sem_otime	 = lower_32_bits(in->sem_otime);
1731		v.sem_otime_high = upper_32_bits(in->sem_otime);
1732		v.sem_ctime	 = lower_32_bits(in->sem_ctime);
1733		v.sem_ctime_high = upper_32_bits(in->sem_ctime);
1734		v.sem_nsems = in->sem_nsems;
1735		return copy_to_user(buf, &v, sizeof(v));
1736	} else {
1737		struct compat_semid_ds v;
1738		memset(&v, 0, sizeof(v));
1739		to_compat_ipc_perm(&v.sem_perm, &in->sem_perm);
1740		v.sem_otime = in->sem_otime;
1741		v.sem_ctime = in->sem_ctime;
1742		v.sem_nsems = in->sem_nsems;
1743		return copy_to_user(buf, &v, sizeof(v));
1744	}
1745}
1746
1747long compat_ksys_semctl(int semid, int semnum, int cmd, int arg)
1748{
1749	void __user *p = compat_ptr(arg);
1750	struct ipc_namespace *ns;
1751	struct semid64_ds semid64;
1752	int version = compat_ipc_parse_version(&cmd);
1753	int err;
1754
1755	ns = current->nsproxy->ipc_ns;
1756
1757	if (semid < 0)
1758		return -EINVAL;
1759
1760	switch (cmd & (~IPC_64)) {
1761	case IPC_INFO:
1762	case SEM_INFO:
1763		return semctl_info(ns, semid, cmd, p);
1764	case IPC_STAT:
1765	case SEM_STAT:
1766	case SEM_STAT_ANY:
1767		err = semctl_stat(ns, semid, cmd, &semid64);
1768		if (err < 0)
1769			return err;
1770		if (copy_compat_semid_to_user(p, &semid64, version))
1771			err = -EFAULT;
1772		return err;
1773	case GETVAL:
1774	case GETPID:
1775	case GETNCNT:
1776	case GETZCNT:
1777	case GETALL:
1778	case SETALL:
1779		return semctl_main(ns, semid, semnum, cmd, p);
1780	case SETVAL:
1781		return semctl_setval(ns, semid, semnum, arg);
1782	case IPC_SET:
1783		if (copy_compat_semid_from_user(&semid64, p, version))
1784			return -EFAULT;
1785		/* fallthru */
1786	case IPC_RMID:
1787		return semctl_down(ns, semid, cmd, &semid64);
1788	default:
1789		return -EINVAL;
1790	}
1791}
1792
1793COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
1794{
1795	return compat_ksys_semctl(semid, semnum, cmd, arg);
1796}
1797#endif
1798
1799/* If the task doesn't already have a undo_list, then allocate one
1800 * here.  We guarantee there is only one thread using this undo list,
1801 * and current is THE ONE
1802 *
1803 * If this allocation and assignment succeeds, but later
1804 * portions of this code fail, there is no need to free the sem_undo_list.
1805 * Just let it stay associated with the task, and it'll be freed later
1806 * at exit time.
1807 *
1808 * This can block, so callers must hold no locks.
1809 */
1810static inline int get_undo_list(struct sem_undo_list **undo_listp)
1811{
1812	struct sem_undo_list *undo_list;
1813
1814	undo_list = current->sysvsem.undo_list;
1815	if (!undo_list) {
1816		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1817		if (undo_list == NULL)
1818			return -ENOMEM;
1819		spin_lock_init(&undo_list->lock);
1820		refcount_set(&undo_list->refcnt, 1);
1821		INIT_LIST_HEAD(&undo_list->list_proc);
1822
1823		current->sysvsem.undo_list = undo_list;
1824	}
1825	*undo_listp = undo_list;
1826	return 0;
1827}
1828
1829static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1830{
1831	struct sem_undo *un;
1832
1833	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1834		if (un->semid == semid)
1835			return un;
1836	}
1837	return NULL;
1838}
1839
1840static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1841{
1842	struct sem_undo *un;
1843
1844	assert_spin_locked(&ulp->lock);
1845
1846	un = __lookup_undo(ulp, semid);
1847	if (un) {
1848		list_del_rcu(&un->list_proc);
1849		list_add_rcu(&un->list_proc, &ulp->list_proc);
1850	}
1851	return un;
1852}
1853
1854/**
1855 * find_alloc_undo - lookup (and if not present create) undo array
1856 * @ns: namespace
1857 * @semid: semaphore array id
1858 *
1859 * The function looks up (and if not present creates) the undo structure.
1860 * The size of the undo structure depends on the size of the semaphore
1861 * array, thus the alloc path is not that straightforward.
1862 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1863 * performs a rcu_read_lock().
1864 */
1865static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1866{
1867	struct sem_array *sma;
1868	struct sem_undo_list *ulp;
1869	struct sem_undo *un, *new;
1870	int nsems, error;
1871
1872	error = get_undo_list(&ulp);
1873	if (error)
1874		return ERR_PTR(error);
1875
1876	rcu_read_lock();
1877	spin_lock(&ulp->lock);
1878	un = lookup_undo(ulp, semid);
1879	spin_unlock(&ulp->lock);
1880	if (likely(un != NULL))
1881		goto out;
1882
1883	/* no undo structure around - allocate one. */
1884	/* step 1: figure out the size of the semaphore array */
1885	sma = sem_obtain_object_check(ns, semid);
1886	if (IS_ERR(sma)) {
1887		rcu_read_unlock();
1888		return ERR_CAST(sma);
1889	}
1890
1891	nsems = sma->sem_nsems;
1892	if (!ipc_rcu_getref(&sma->sem_perm)) {
1893		rcu_read_unlock();
1894		un = ERR_PTR(-EIDRM);
1895		goto out;
1896	}
1897	rcu_read_unlock();
1898
1899	/* step 2: allocate new undo structure */
1900	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1901	if (!new) {
1902		ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1903		return ERR_PTR(-ENOMEM);
1904	}
1905
1906	/* step 3: Acquire the lock on semaphore array */
1907	rcu_read_lock();
1908	sem_lock_and_putref(sma);
1909	if (!ipc_valid_object(&sma->sem_perm)) {
1910		sem_unlock(sma, -1);
1911		rcu_read_unlock();
1912		kfree(new);
1913		un = ERR_PTR(-EIDRM);
1914		goto out;
1915	}
1916	spin_lock(&ulp->lock);
1917
1918	/*
1919	 * step 4: check for races: did someone else allocate the undo struct?
1920	 */
1921	un = lookup_undo(ulp, semid);
1922	if (un) {
1923		kfree(new);
1924		goto success;
1925	}
1926	/* step 5: initialize & link new undo structure */
1927	new->semadj = (short *) &new[1];
1928	new->ulp = ulp;
1929	new->semid = semid;
1930	assert_spin_locked(&ulp->lock);
1931	list_add_rcu(&new->list_proc, &ulp->list_proc);
1932	ipc_assert_locked_object(&sma->sem_perm);
1933	list_add(&new->list_id, &sma->list_id);
1934	un = new;
1935
1936success:
1937	spin_unlock(&ulp->lock);
1938	sem_unlock(sma, -1);
1939out:
1940	return un;
1941}
1942
1943static long do_semtimedop(int semid, struct sembuf __user *tsops,
1944		unsigned nsops, const struct timespec64 *timeout)
1945{
1946	int error = -EINVAL;
1947	struct sem_array *sma;
1948	struct sembuf fast_sops[SEMOPM_FAST];
1949	struct sembuf *sops = fast_sops, *sop;
1950	struct sem_undo *un;
1951	int max, locknum;
1952	bool undos = false, alter = false, dupsop = false;
1953	struct sem_queue queue;
1954	unsigned long dup = 0, jiffies_left = 0;
1955	struct ipc_namespace *ns;
1956
1957	ns = current->nsproxy->ipc_ns;
1958
1959	if (nsops < 1 || semid < 0)
1960		return -EINVAL;
1961	if (nsops > ns->sc_semopm)
1962		return -E2BIG;
1963	if (nsops > SEMOPM_FAST) {
1964		sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
1965		if (sops == NULL)
1966			return -ENOMEM;
1967	}
1968
1969	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
1970		error =  -EFAULT;
1971		goto out_free;
1972	}
1973
1974	if (timeout) {
1975		if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 ||
1976			timeout->tv_nsec >= 1000000000L) {
1977			error = -EINVAL;
1978			goto out_free;
1979		}
1980		jiffies_left = timespec64_to_jiffies(timeout);
1981	}
1982
1983	max = 0;
1984	for (sop = sops; sop < sops + nsops; sop++) {
1985		unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
1986
1987		if (sop->sem_num >= max)
1988			max = sop->sem_num;
1989		if (sop->sem_flg & SEM_UNDO)
1990			undos = true;
1991		if (dup & mask) {
1992			/*
1993			 * There was a previous alter access that appears
1994			 * to have accessed the same semaphore, thus use
1995			 * the dupsop logic. "appears", because the detection
1996			 * can only check % BITS_PER_LONG.
1997			 */
1998			dupsop = true;
1999		}
2000		if (sop->sem_op != 0) {
2001			alter = true;
2002			dup |= mask;
2003		}
2004	}
2005
2006	if (undos) {
2007		/* On success, find_alloc_undo takes the rcu_read_lock */
2008		un = find_alloc_undo(ns, semid);
2009		if (IS_ERR(un)) {
2010			error = PTR_ERR(un);
2011			goto out_free;
2012		}
2013	} else {
2014		un = NULL;
2015		rcu_read_lock();
2016	}
2017
2018	sma = sem_obtain_object_check(ns, semid);
2019	if (IS_ERR(sma)) {
2020		rcu_read_unlock();
2021		error = PTR_ERR(sma);
2022		goto out_free;
2023	}
2024
2025	error = -EFBIG;
2026	if (max >= sma->sem_nsems) {
2027		rcu_read_unlock();
2028		goto out_free;
2029	}
2030
2031	error = -EACCES;
2032	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
2033		rcu_read_unlock();
2034		goto out_free;
2035	}
2036
2037	error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
2038	if (error) {
2039		rcu_read_unlock();
2040		goto out_free;
2041	}
2042
2043	error = -EIDRM;
2044	locknum = sem_lock(sma, sops, nsops);
2045	/*
2046	 * We eventually might perform the following check in a lockless
2047	 * fashion, considering ipc_valid_object() locking constraints.
2048	 * If nsops == 1 and there is no contention for sem_perm.lock, then
2049	 * only a per-semaphore lock is held and it's OK to proceed with the
2050	 * check below. More details on the fine grained locking scheme
2051	 * entangled here and why it's RMID race safe on comments at sem_lock()
2052	 */
2053	if (!ipc_valid_object(&sma->sem_perm))
2054		goto out_unlock_free;
2055	/*
2056	 * semid identifiers are not unique - find_alloc_undo may have
2057	 * allocated an undo structure, it was invalidated by an RMID
2058	 * and now a new array with received the same id. Check and fail.
2059	 * This case can be detected checking un->semid. The existence of
2060	 * "un" itself is guaranteed by rcu.
2061	 */
2062	if (un && un->semid == -1)
2063		goto out_unlock_free;
2064
2065	queue.sops = sops;
2066	queue.nsops = nsops;
2067	queue.undo = un;
2068	queue.pid = task_tgid(current);
2069	queue.alter = alter;
2070	queue.dupsop = dupsop;
2071
2072	error = perform_atomic_semop(sma, &queue);
2073	if (error == 0) { /* non-blocking succesfull path */
2074		DEFINE_WAKE_Q(wake_q);
2075
2076		/*
2077		 * If the operation was successful, then do
2078		 * the required updates.
2079		 */
2080		if (alter)
2081			do_smart_update(sma, sops, nsops, 1, &wake_q);
2082		else
2083			set_semotime(sma, sops);
2084
2085		sem_unlock(sma, locknum);
2086		rcu_read_unlock();
2087		wake_up_q(&wake_q);
2088
2089		goto out_free;
2090	}
2091	if (error < 0) /* non-blocking error path */
2092		goto out_unlock_free;
2093
2094	/*
2095	 * We need to sleep on this operation, so we put the current
2096	 * task into the pending queue and go to sleep.
2097	 */
2098	if (nsops == 1) {
2099		struct sem *curr;
2100		int idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
2101		curr = &sma->sems[idx];
2102
2103		if (alter) {
2104			if (sma->complex_count) {
2105				list_add_tail(&queue.list,
2106						&sma->pending_alter);
2107			} else {
2108
2109				list_add_tail(&queue.list,
2110						&curr->pending_alter);
2111			}
2112		} else {
2113			list_add_tail(&queue.list, &curr->pending_const);
2114		}
2115	} else {
2116		if (!sma->complex_count)
2117			merge_queues(sma);
2118
2119		if (alter)
2120			list_add_tail(&queue.list, &sma->pending_alter);
2121		else
2122			list_add_tail(&queue.list, &sma->pending_const);
2123
2124		sma->complex_count++;
2125	}
2126
2127	do {
2128		WRITE_ONCE(queue.status, -EINTR);
2129		queue.sleeper = current;
2130
2131		__set_current_state(TASK_INTERRUPTIBLE);
2132		sem_unlock(sma, locknum);
2133		rcu_read_unlock();
2134
2135		if (timeout)
2136			jiffies_left = schedule_timeout(jiffies_left);
2137		else
2138			schedule();
2139
2140		/*
2141		 * fastpath: the semop has completed, either successfully or
2142		 * not, from the syscall pov, is quite irrelevant to us at this
2143		 * point; we're done.
2144		 *
2145		 * We _do_ care, nonetheless, about being awoken by a signal or
2146		 * spuriously.  The queue.status is checked again in the
2147		 * slowpath (aka after taking sem_lock), such that we can detect
2148		 * scenarios where we were awakened externally, during the
2149		 * window between wake_q_add() and wake_up_q().
2150		 */
2151		error = READ_ONCE(queue.status);
2152		if (error != -EINTR) {
2153			/*
2154			 * User space could assume that semop() is a memory
2155			 * barrier: Without the mb(), the cpu could
2156			 * speculatively read in userspace stale data that was
2157			 * overwritten by the previous owner of the semaphore.
2158			 */
2159			smp_mb();
2160			goto out_free;
2161		}
2162
2163		rcu_read_lock();
2164		locknum = sem_lock(sma, sops, nsops);
2165
2166		if (!ipc_valid_object(&sma->sem_perm))
2167			goto out_unlock_free;
2168
2169		error = READ_ONCE(queue.status);
2170
2171		/*
2172		 * If queue.status != -EINTR we are woken up by another process.
2173		 * Leave without unlink_queue(), but with sem_unlock().
2174		 */
2175		if (error != -EINTR)
2176			goto out_unlock_free;
2177
2178		/*
2179		 * If an interrupt occurred we have to clean up the queue.
2180		 */
2181		if (timeout && jiffies_left == 0)
2182			error = -EAGAIN;
2183	} while (error == -EINTR && !signal_pending(current)); /* spurious */
2184
2185	unlink_queue(sma, &queue);
2186
2187out_unlock_free:
2188	sem_unlock(sma, locknum);
2189	rcu_read_unlock();
2190out_free:
2191	if (sops != fast_sops)
2192		kvfree(sops);
2193	return error;
2194}
2195
2196long ksys_semtimedop(int semid, struct sembuf __user *tsops,
2197		     unsigned int nsops, const struct __kernel_timespec __user *timeout)
2198{
2199	if (timeout) {
2200		struct timespec64 ts;
2201		if (get_timespec64(&ts, timeout))
2202			return -EFAULT;
2203		return do_semtimedop(semid, tsops, nsops, &ts);
2204	}
2205	return do_semtimedop(semid, tsops, nsops, NULL);
2206}
2207
2208SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
2209		unsigned int, nsops, const struct __kernel_timespec __user *, timeout)
2210{
2211	return ksys_semtimedop(semid, tsops, nsops, timeout);
2212}
2213
2214#ifdef CONFIG_COMPAT_32BIT_TIME
2215long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
2216			    unsigned int nsops,
2217			    const struct compat_timespec __user *timeout)
2218{
2219	if (timeout) {
2220		struct timespec64 ts;
2221		if (compat_get_timespec64(&ts, timeout))
2222			return -EFAULT;
2223		return do_semtimedop(semid, tsems, nsops, &ts);
2224	}
2225	return do_semtimedop(semid, tsems, nsops, NULL);
2226}
2227
2228COMPAT_SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsems,
2229		       unsigned int, nsops,
2230		       const struct compat_timespec __user *, timeout)
2231{
2232	return compat_ksys_semtimedop(semid, tsems, nsops, timeout);
2233}
2234#endif
2235
2236SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2237		unsigned, nsops)
2238{
2239	return do_semtimedop(semid, tsops, nsops, NULL);
2240}
2241
2242/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2243 * parent and child tasks.
2244 */
2245
2246int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2247{
2248	struct sem_undo_list *undo_list;
2249	int error;
2250
2251	if (clone_flags & CLONE_SYSVSEM) {
2252		error = get_undo_list(&undo_list);
2253		if (error)
2254			return error;
2255		refcount_inc(&undo_list->refcnt);
2256		tsk->sysvsem.undo_list = undo_list;
2257	} else
2258		tsk->sysvsem.undo_list = NULL;
2259
2260	return 0;
2261}
2262
2263/*
2264 * add semadj values to semaphores, free undo structures.
2265 * undo structures are not freed when semaphore arrays are destroyed
2266 * so some of them may be out of date.
2267 * IMPLEMENTATION NOTE: There is some confusion over whether the
2268 * set of adjustments that needs to be done should be done in an atomic
2269 * manner or not. That is, if we are attempting to decrement the semval
2270 * should we queue up and wait until we can do so legally?
2271 * The original implementation attempted to do this (queue and wait).
2272 * The current implementation does not do so. The POSIX standard
2273 * and SVID should be consulted to determine what behavior is mandated.
2274 */
2275void exit_sem(struct task_struct *tsk)
2276{
2277	struct sem_undo_list *ulp;
2278
2279	ulp = tsk->sysvsem.undo_list;
2280	if (!ulp)
2281		return;
2282	tsk->sysvsem.undo_list = NULL;
2283
2284	if (!refcount_dec_and_test(&ulp->refcnt))
2285		return;
2286
2287	for (;;) {
2288		struct sem_array *sma;
2289		struct sem_undo *un;
2290		int semid, i;
2291		DEFINE_WAKE_Q(wake_q);
2292
2293		cond_resched();
2294
2295		rcu_read_lock();
2296		un = list_entry_rcu(ulp->list_proc.next,
2297				    struct sem_undo, list_proc);
2298		if (&un->list_proc == &ulp->list_proc) {
2299			/*
2300			 * We must wait for freeary() before freeing this ulp,
2301			 * in case we raced with last sem_undo. There is a small
2302			 * possibility where we exit while freeary() didn't
2303			 * finish unlocking sem_undo_list.
2304			 */
2305			spin_lock(&ulp->lock);
2306			spin_unlock(&ulp->lock);
2307			rcu_read_unlock();
2308			break;
2309		}
2310		spin_lock(&ulp->lock);
2311		semid = un->semid;
2312		spin_unlock(&ulp->lock);
2313
2314		/* exit_sem raced with IPC_RMID, nothing to do */
2315		if (semid == -1) {
2316			rcu_read_unlock();
2317			continue;
2318		}
2319
2320		sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2321		/* exit_sem raced with IPC_RMID, nothing to do */
2322		if (IS_ERR(sma)) {
2323			rcu_read_unlock();
2324			continue;
2325		}
2326
2327		sem_lock(sma, NULL, -1);
2328		/* exit_sem raced with IPC_RMID, nothing to do */
2329		if (!ipc_valid_object(&sma->sem_perm)) {
2330			sem_unlock(sma, -1);
2331			rcu_read_unlock();
2332			continue;
2333		}
2334		un = __lookup_undo(ulp, semid);
2335		if (un == NULL) {
2336			/* exit_sem raced with IPC_RMID+semget() that created
2337			 * exactly the same semid. Nothing to do.
2338			 */
2339			sem_unlock(sma, -1);
2340			rcu_read_unlock();
2341			continue;
2342		}
2343
2344		/* remove un from the linked lists */
2345		ipc_assert_locked_object(&sma->sem_perm);
2346		list_del(&un->list_id);
2347
2348		/* we are the last process using this ulp, acquiring ulp->lock
2349		 * isn't required. Besides that, we are also protected against
2350		 * IPC_RMID as we hold sma->sem_perm lock now
2351		 */
2352		list_del_rcu(&un->list_proc);
2353
2354		/* perform adjustments registered in un */
2355		for (i = 0; i < sma->sem_nsems; i++) {
2356			struct sem *semaphore = &sma->sems[i];
2357			if (un->semadj[i]) {
2358				semaphore->semval += un->semadj[i];
2359				/*
2360				 * Range checks of the new semaphore value,
2361				 * not defined by sus:
2362				 * - Some unices ignore the undo entirely
2363				 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2364				 * - some cap the value (e.g. FreeBSD caps
2365				 *   at 0, but doesn't enforce SEMVMX)
2366				 *
2367				 * Linux caps the semaphore value, both at 0
2368				 * and at SEMVMX.
2369				 *
2370				 *	Manfred <manfred@colorfullife.com>
2371				 */
2372				if (semaphore->semval < 0)
2373					semaphore->semval = 0;
2374				if (semaphore->semval > SEMVMX)
2375					semaphore->semval = SEMVMX;
2376				ipc_update_pid(&semaphore->sempid, task_tgid(current));
2377			}
2378		}
2379		/* maybe some queued-up processes were waiting for this */
2380		do_smart_update(sma, NULL, 0, 1, &wake_q);
2381		sem_unlock(sma, -1);
2382		rcu_read_unlock();
2383		wake_up_q(&wake_q);
2384
2385		kfree_rcu(un, rcu);
2386	}
2387	kfree(ulp);
2388}
2389
2390#ifdef CONFIG_PROC_FS
2391static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2392{
2393	struct user_namespace *user_ns = seq_user_ns(s);
2394	struct kern_ipc_perm *ipcp = it;
2395	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
2396	time64_t sem_otime;
2397
2398	/*
2399	 * The proc interface isn't aware of sem_lock(), it calls
2400	 * ipc_lock_object() directly (in sysvipc_find_ipc).
2401	 * In order to stay compatible with sem_lock(), we must
2402	 * enter / leave complex_mode.
2403	 */
2404	complexmode_enter(sma);
2405
2406	sem_otime = get_semotime(sma);
2407
2408	seq_printf(s,
2409		   "%10d %10d  %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
2410		   sma->sem_perm.key,
2411		   sma->sem_perm.id,
2412		   sma->sem_perm.mode,
2413		   sma->sem_nsems,
2414		   from_kuid_munged(user_ns, sma->sem_perm.uid),
2415		   from_kgid_munged(user_ns, sma->sem_perm.gid),
2416		   from_kuid_munged(user_ns, sma->sem_perm.cuid),
2417		   from_kgid_munged(user_ns, sma->sem_perm.cgid),
2418		   sem_otime,
2419		   sma->sem_ctime);
2420
2421	complexmode_tryleave(sma);
2422
2423	return 0;
2424}
2425#endif
2426