linux - ipc/sem.c

2484 lines · 63.1 KiB

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 <[email protected]>
8	*
9	* SMP-threaded, sysctl's added
10	* (c) 1999 Manfred Spraul <[email protected]>
11	* Enforced range limit on SEM_UNDO
12	* (c) 2001 Red Hat Inc
13	* Lockless wakeup
14	* (c) 2003 Manfred Spraul <[email protected]>
15	* (c) 2016 Davidlohr Bueso <[email protected]>
16	* Further wakeup optimizations, documentation
17	* (c) 2010 Manfred Spraul <[email protected]>
18	*
19	* support for audit of ipc object properties and permission changes
20	* Dustin Kirkland <[email protected]>
21	*
22	* namespaces support
23	* OpenVZ, SWsoft Inc.
24	* Pavel Emelianov <[email protected]>
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 runtime 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. */
95	struct 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. */
114	struct 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. */
130	struct 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	*/
146	struct 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	*/
162	struct 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
171	static int newary(struct ipc_namespace , struct ipc_params );
172	static void freeary(struct ipc_namespace , struct kern_ipc_perm );
173	#ifdef CONFIG_PROC_FS
174	static 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	*
209	* Exceptions:
210	* 1) use_global_lock: (SEM_BARRIER_1)
211	* Setting it from non-zero to 0 is a RELEASE, this is ensured by
212	* using smp_store_release(): Immediately after setting it to 0,
213	* a simple op can start.
214	* Testing if it is non-zero is an ACQUIRE, this is ensured by using
215	* smp_load_acquire().
216	* Setting it from 0 to non-zero must be ordered with regards to
217	* this smp_load_acquire(), this is guaranteed because the smp_load_acquire()
218	* is inside a spin_lock() and after a write from 0 to non-zero a
219	* spin_lock()+spin_unlock() is done.
220	* To prevent the compiler/cpu temporarily writing 0 to use_global_lock,
221	* READ_ONCE()/WRITE_ONCE() is used.
222	*
223	* 2) queue.status: (SEM_BARRIER_2)
224	* Initialization is done while holding sem_lock(), so no further barrier is
225	* required.
226	* Setting it to a result code is a RELEASE, this is ensured by both a
227	* smp_store_release() (for case a) and while holding sem_lock()
228	* (for case b).
229	* The ACQUIRE when reading the result code without holding sem_lock() is
230	* achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep().
231	* (case a above).
232	* Reading the result code while holding sem_lock() needs no further barriers,
233	* the locks inside sem_lock() enforce ordering (case b above)
234	*
235	* 3) current->state:
236	* current->state is set to TASK_INTERRUPTIBLE while holding sem_lock().
237	* The wakeup is handled using the wake_q infrastructure. wake_q wakeups may
238	* happen immediately after calling wake_q_add. As wake_q_add_safe() is called
239	* when holding sem_lock(), no further barriers are required.
240	*
241	* See also ipc/mqueue.c for more details on the covered races.
242	*/
243
244	#define sc_semmsl sem_ctls[0]
245	#define sc_semmns sem_ctls[1]
246	#define sc_semopm sem_ctls[2]
247	#define sc_semmni sem_ctls[3]
248
249	void sem_init_ns(struct ipc_namespace *ns)
250	{
251	ns->sc_semmsl = SEMMSL;
252	ns->sc_semmns = SEMMNS;
253	ns->sc_semopm = SEMOPM;
254	ns->sc_semmni = SEMMNI;
255	ns->used_sems = 0;
256	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
257	}
258
259	#ifdef CONFIG_IPC_NS
260	void sem_exit_ns(struct ipc_namespace *ns)
261	{
262	free_ipcs(ns, &sem_ids(ns), freeary);
263	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
264	rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht);
265	}
266	#endif
267
268	void __init sem_init(void)
269	{
270	sem_init_ns(&init_ipc_ns);
271	ipc_init_proc_interface("sysvipc/sem",
272	" key semid perms nsems uid gid cuid cgid otime ctime\n",
273	IPC_SEM_IDS, sysvipc_sem_proc_show);
274	}
275
276	/**
277	* unmerge_queues - unmerge queues, if possible.
278	* @sma: semaphore array
279	*
280	* The function unmerges the wait queues if complex_count is 0.
281	* It must be called prior to dropping the global semaphore array lock.
282	*/
283	static void unmerge_queues(struct sem_array *sma)
284	{
285	struct sem_queue q, tq;
286
287	/* complex operations still around? */
288	if (sma->complex_count)
289	return;
290	/*
291	* We will switch back to simple mode.
292	* Move all pending operation back into the per-semaphore
293	* queues.
294	*/
295	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
296	struct sem *curr;
297	curr = &sma->sems[q->sops[0].sem_num];
298
299	list_add_tail(&q->list, &curr->pending_alter);
300	}
301	INIT_LIST_HEAD(&sma->pending_alter);
302	}
303
304	/**
305	* merge_queues - merge single semop queues into global queue
306	* @sma: semaphore array
307	*
308	* This function merges all per-semaphore queues into the global queue.
309	* It is necessary to achieve FIFO ordering for the pending single-sop
310	* operations when a multi-semop operation must sleep.
311	* Only the alter operations must be moved, the const operations can stay.
312	*/
313	static void merge_queues(struct sem_array *sma)
314	{
315	int i;
316	for (i = 0; i < sma->sem_nsems; i++) {
317	struct sem *sem = &sma->sems[i];
318
319	list_splice_init(&sem->pending_alter, &sma->pending_alter);
320	}
321	}
322
323	static void sem_rcu_free(struct rcu_head *head)
324	{
325	struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
326	struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
327
328	security_sem_free(&sma->sem_perm);
329	kvfree(sma);
330	}
331
332	/*
333	* Enter the mode suitable for non-simple operations:
334	* Caller must own sem_perm.lock.
335	*/
336	static void complexmode_enter(struct sem_array *sma)
337	{
338	int i;
339	struct sem *sem;
340
341	if (sma->use_global_lock > 0) {
342	/*
343	* We are already in global lock mode.
344	* Nothing to do, just reset the
345	* counter until we return to simple mode.
346	*/
347	WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS);
348	return;
349	}
350	WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS);
351
352	for (i = 0; i < sma->sem_nsems; i++) {
353	sem = &sma->sems[i];
354	spin_lock(&sem->lock);
355	spin_unlock(&sem->lock);
356	}
357	}
358
359	/*
360	* Try to leave the mode that disallows simple operations:
361	* Caller must own sem_perm.lock.
362	*/
363	static void complexmode_tryleave(struct sem_array *sma)
364	{
365	if (sma->complex_count) {
366	/* Complex ops are sleeping.
367	* We must stay in complex mode
368	*/
369	return;
370	}
371	if (sma->use_global_lock == 1) {
372
373	/* See SEM_BARRIER_1 for purpose/pairing */
374	smp_store_release(&sma->use_global_lock, 0);
375	} else {
376	WRITE_ONCE(sma->use_global_lock,
377	sma->use_global_lock-1);
378	}
379	}
380
381	#define SEM_GLOBAL_LOCK (-1)
382	/*
383	* If the request contains only one semaphore operation, and there are
384	* no complex transactions pending, lock only the semaphore involved.
385	* Otherwise, lock the entire semaphore array, since we either have
386	* multiple semaphores in our own semops, or we need to look at
387	* semaphores from other pending complex operations.
388	*/
389	static inline int sem_lock(struct sem_array sma, struct sembuf sops,
390	int nsops)
391	{
392	struct sem *sem;
393	int idx;
394
395	if (nsops != 1) {
396	/* Complex operation - acquire a full lock */
397	ipc_lock_object(&sma->sem_perm);
398
399	/* Prevent parallel simple ops */
400	complexmode_enter(sma);
401	return SEM_GLOBAL_LOCK;
402	}
403
404	/*
405	* Only one semaphore affected - try to optimize locking.
406	* Optimized locking is possible if no complex operation
407	* is either enqueued or processed right now.
408	*
409	* Both facts are tracked by use_global_mode.
410	*/
411	idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
412	sem = &sma->sems[idx];
413
414	/*
415	* Initial check for use_global_lock. Just an optimization,
416	* no locking, no memory barrier.
417	*/
418	if (!READ_ONCE(sma->use_global_lock)) {
419	/*
420	* It appears that no complex operation is around.
421	* Acquire the per-semaphore lock.
422	*/
423	spin_lock(&sem->lock);
424
425	/* see SEM_BARRIER_1 for purpose/pairing */
426	if (!smp_load_acquire(&sma->use_global_lock)) {
427	/* fast path successful! */
428	return sops->sem_num;
429	}
430	spin_unlock(&sem->lock);
431	}
432
433	/* slow path: acquire the full lock */
434	ipc_lock_object(&sma->sem_perm);
435
436	if (sma->use_global_lock == 0) {
437	/*
438	* The use_global_lock mode ended while we waited for
439	* sma->sem_perm.lock. Thus we must switch to locking
440	* with sem->lock.
441	* Unlike in the fast path, there is no need to recheck
442	* sma->use_global_lock after we have acquired sem->lock:
443	* We own sma->sem_perm.lock, thus use_global_lock cannot
444	* change.
445	*/
446	spin_lock(&sem->lock);
447
448	ipc_unlock_object(&sma->sem_perm);
449	return sops->sem_num;
450	} else {
451	/*
452	* Not a false alarm, thus continue to use the global lock
453	* mode. No need for complexmode_enter(), this was done by
454	* the caller that has set use_global_mode to non-zero.
455	*/
456	return SEM_GLOBAL_LOCK;
457	}
458	}
459
460	static inline void sem_unlock(struct sem_array *sma, int locknum)
461	{
462	if (locknum == SEM_GLOBAL_LOCK) {
463	unmerge_queues(sma);
464	complexmode_tryleave(sma);
465	ipc_unlock_object(&sma->sem_perm);
466	} else {
467	struct sem *sem = &sma->sems[locknum];
468	spin_unlock(&sem->lock);
469	}
470	}
471
472	/*
473	* sem_lock_(check_) routines are called in the paths where the rwsem
474	* is not held.
475	*
476	* The caller holds the RCU read lock.
477	*/
478	static inline struct sem_array sem_obtain_object(struct ipc_namespace ns, int id)
479	{
480	struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
481
482	if (IS_ERR(ipcp))
483	return ERR_CAST(ipcp);
484
485	return container_of(ipcp, struct sem_array, sem_perm);
486	}
487
488	static inline struct sem_array sem_obtain_object_check(struct ipc_namespace ns,
489	int id)
490	{
491	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
492
493	if (IS_ERR(ipcp))
494	return ERR_CAST(ipcp);
495
496	return container_of(ipcp, struct sem_array, sem_perm);
497	}
498
499	static inline void sem_lock_and_putref(struct sem_array *sma)
500	{
501	sem_lock(sma, NULL, -1);
502	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
503	}
504
505	static inline void sem_rmid(struct ipc_namespace ns, struct sem_array s)
506	{
507	ipc_rmid(&sem_ids(ns), &s->sem_perm);
508	}
509
510	static struct sem_array *sem_alloc(size_t nsems)
511	{
512	struct sem_array *sma;
513
514	if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
515	return NULL;
516
517	sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL_ACCOUNT);
518	if (unlikely(!sma))
519	return NULL;
520
521	return sma;
522	}
523
524	/**
525	* newary - Create a new semaphore set
526	* @ns: namespace
527	* @params: ptr to the structure that contains key, semflg and nsems
528	*
529	* Called with sem_ids.rwsem held (as a writer)
530	*/
531	static int newary(struct ipc_namespace ns, struct ipc_params params)
532	{
533	int retval;
534	struct sem_array *sma;
535	key_t key = params->key;
536	int nsems = params->u.nsems;
537	int semflg = params->flg;
538	int i;
539
540	if (!nsems)
541	return -EINVAL;
542	if (ns->used_sems + nsems > ns->sc_semmns)
543	return -ENOSPC;
544
545	sma = sem_alloc(nsems);
546	if (!sma)
547	return -ENOMEM;
548
549	sma->sem_perm.mode = (semflg & S_IRWXUGO);
550	sma->sem_perm.key = key;
551
552	sma->sem_perm.security = NULL;
553	retval = security_sem_alloc(&sma->sem_perm);
554	if (retval) {
555	kvfree(sma);
556	return retval;
557	}
558
559	for (i = 0; i < nsems; i++) {
560	INIT_LIST_HEAD(&sma->sems[i].pending_alter);
561	INIT_LIST_HEAD(&sma->sems[i].pending_const);
562	spin_lock_init(&sma->sems[i].lock);
563	}
564
565	sma->complex_count = 0;
566	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
567	INIT_LIST_HEAD(&sma->pending_alter);
568	INIT_LIST_HEAD(&sma->pending_const);
569	INIT_LIST_HEAD(&sma->list_id);
570	sma->sem_nsems = nsems;
571	sma->sem_ctime = ktime_get_real_seconds();
572
573	/* ipc_addid() locks sma upon success. */
574	retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
575	if (retval < 0) {
576	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
577	return retval;
578	}
579	ns->used_sems += nsems;
580
581	sem_unlock(sma, -1);
582	rcu_read_unlock();
583
584	return sma->sem_perm.id;
585	}
586
587
588	/*
589	* Called with sem_ids.rwsem and ipcp locked.
590	*/
591	static int sem_more_checks(struct kern_ipc_perm ipcp, struct ipc_params params)
592	{
593	struct sem_array *sma;
594
595	sma = container_of(ipcp, struct sem_array, sem_perm);
596	if (params->u.nsems > sma->sem_nsems)
597	return -EINVAL;
598
599	return 0;
600	}
601
602	long ksys_semget(key_t key, int nsems, int semflg)
603	{
604	struct ipc_namespace *ns;
605	static const struct ipc_ops sem_ops = {
606	.getnew = newary,
607	.associate = security_sem_associate,
608	.more_checks = sem_more_checks,
609	};
610	struct ipc_params sem_params;
611
612	ns = current->nsproxy->ipc_ns;
613
614	if (nsems < 0 \|\| nsems > ns->sc_semmsl)
615	return -EINVAL;
616
617	sem_params.key = key;
618	sem_params.flg = semflg;
619	sem_params.u.nsems = nsems;
620
621	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
622	}
623
624	SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
625	{
626	return ksys_semget(key, nsems, semflg);
627	}
628
629	/**
630	* perform_atomic_semop[_slow] - Attempt to perform semaphore
631	* operations on a given array.
632	* @sma: semaphore array
633	* @q: struct sem_queue that describes the operation
634	*
635	* Caller blocking are as follows, based the value
636	* indicated by the semaphore operation (sem_op):
637	*
638	* (1) >0 never blocks.
639	* (2) 0 (wait-for-zero operation): semval is non-zero.
640	* (3) <0 attempting to decrement semval to a value smaller than zero.
641	*
642	* Returns 0 if the operation was possible.
643	* Returns 1 if the operation is impossible, the caller must sleep.
644	* Returns <0 for error codes.
645	*/
646	static int perform_atomic_semop_slow(struct sem_array sma, struct sem_queue q)
647	{
648	int result, sem_op, nsops;
649	struct pid *pid;
650	struct sembuf *sop;
651	struct sem *curr;
652	struct sembuf *sops;
653	struct sem_undo *un;
654
655	sops = q->sops;
656	nsops = q->nsops;
657	un = q->undo;
658
659	for (sop = sops; sop < sops + nsops; sop++) {
660	int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
661	curr = &sma->sems[idx];
662	sem_op = sop->sem_op;
663	result = curr->semval;
664
665	if (!sem_op && result)
666	goto would_block;
667
668	result += sem_op;
669	if (result < 0)
670	goto would_block;
671	if (result > SEMVMX)
672	goto out_of_range;
673
674	if (sop->sem_flg & SEM_UNDO) {
675	int undo = un->semadj[sop->sem_num] - sem_op;
676	/* Exceeding the undo range is an error. */
677	if (undo < (-SEMAEM - 1) \|\| undo > SEMAEM)
678	goto out_of_range;
679	un->semadj[sop->sem_num] = undo;
680	}
681
682	curr->semval = result;
683	}
684
685	sop--;
686	pid = q->pid;
687	while (sop >= sops) {
688	ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid);
689	sop--;
690	}
691
692	return 0;
693
694	out_of_range:
695	result = -ERANGE;
696	goto undo;
697
698	would_block:
699	q->blocking = sop;
700
701	if (sop->sem_flg & IPC_NOWAIT)
702	result = -EAGAIN;
703	else
704	result = 1;
705
706	undo:
707	sop--;
708	while (sop >= sops) {
709	sem_op = sop->sem_op;
710	sma->sems[sop->sem_num].semval -= sem_op;
711	if (sop->sem_flg & SEM_UNDO)
712	un->semadj[sop->sem_num] += sem_op;
713	sop--;
714	}
715
716	return result;
717	}
718
719	static int perform_atomic_semop(struct sem_array sma, struct sem_queue q)
720	{
721	int result, sem_op, nsops;
722	struct sembuf *sop;
723	struct sem *curr;
724	struct sembuf *sops;
725	struct sem_undo *un;
726
727	sops = q->sops;
728	nsops = q->nsops;
729	un = q->undo;
730
731	if (unlikely(q->dupsop))
732	return perform_atomic_semop_slow(sma, q);
733
734	/*
735	* We scan the semaphore set twice, first to ensure that the entire
736	* operation can succeed, therefore avoiding any pointless writes
737	* to shared memory and having to undo such changes in order to block
738	* until the operations can go through.
739	*/
740	for (sop = sops; sop < sops + nsops; sop++) {
741	int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
742
743	curr = &sma->sems[idx];
744	sem_op = sop->sem_op;
745	result = curr->semval;
746
747	if (!sem_op && result)
748	goto would_block; /* wait-for-zero */
749
750	result += sem_op;
751	if (result < 0)
752	goto would_block;
753
754	if (result > SEMVMX)
755	return -ERANGE;
756
757	if (sop->sem_flg & SEM_UNDO) {
758	int undo = un->semadj[sop->sem_num] - sem_op;
759
760	/* Exceeding the undo range is an error. */
761	if (undo < (-SEMAEM - 1) \|\| undo > SEMAEM)
762	return -ERANGE;
763	}
764	}
765
766	for (sop = sops; sop < sops + nsops; sop++) {
767	curr = &sma->sems[sop->sem_num];
768	sem_op = sop->sem_op;
769
770	if (sop->sem_flg & SEM_UNDO) {
771	int undo = un->semadj[sop->sem_num] - sem_op;
772
773	un->semadj[sop->sem_num] = undo;
774	}
775	curr->semval += sem_op;
776	ipc_update_pid(&curr->sempid, q->pid);
777	}
778
779	return 0;
780
781	would_block:
782	q->blocking = sop;
783	return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
784	}
785
786	static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
787	struct wake_q_head *wake_q)
788	{
789	struct task_struct *sleeper;
790
791	sleeper = get_task_struct(q->sleeper);
792
793	/* see SEM_BARRIER_2 for purpose/pairing */
794	smp_store_release(&q->status, error);
795
796	wake_q_add_safe(wake_q, sleeper);
797	}
798
799	static void unlink_queue(struct sem_array sma, struct sem_queue q)
800	{
801	list_del(&q->list);
802	if (q->nsops > 1)
803	sma->complex_count--;
804	}
805
806	/** check_restart(sma, q)
807	* @sma: semaphore array
808	* @q: the operation that just completed
809	*
810	* update_queue is O(N^2) when it restarts scanning the whole queue of
811	* waiting operations. Therefore this function checks if the restart is
812	* really necessary. It is called after a previously waiting operation
813	* modified the array.
814	* Note that wait-for-zero operations are handled without restart.
815	*/
816	static inline int check_restart(struct sem_array sma, struct sem_queue q)
817	{
818	/* pending complex alter operations are too difficult to analyse */
819	if (!list_empty(&sma->pending_alter))
820	return 1;
821
822	/* we were a sleeping complex operation. Too difficult */
823	if (q->nsops > 1)
824	return 1;
825
826	/* It is impossible that someone waits for the new value:
827	* - complex operations always restart.
828	* - wait-for-zero are handled separately.
829	* - q is a previously sleeping simple operation that
830	* altered the array. It must be a decrement, because
831	* simple increments never sleep.
832	* - If there are older (higher priority) decrements
833	* in the queue, then they have observed the original
834	* semval value and couldn't proceed. The operation
835	* decremented to value - thus they won't proceed either.
836	*/
837	return 0;
838	}
839
840	/**
841	* wake_const_ops - wake up non-alter tasks
842	* @sma: semaphore array.
843	* @semnum: semaphore that was modified.
844	* @wake_q: lockless wake-queue head.
845	*
846	* wake_const_ops must be called after a semaphore in a semaphore array
847	* was set to 0. If complex const operations are pending, wake_const_ops must
848	* be called with semnum = -1, as well as with the number of each modified
849	* semaphore.
850	* The tasks that must be woken up are added to @wake_q. The return code
851	* is stored in q->pid.
852	* The function returns 1 if at least one operation was completed successfully.
853	*/
854	static int wake_const_ops(struct sem_array *sma, int semnum,
855	struct wake_q_head *wake_q)
856	{
857	struct sem_queue q, tmp;
858	struct list_head *pending_list;
859	int semop_completed = 0;
860
861	if (semnum == -1)
862	pending_list = &sma->pending_const;
863	else
864	pending_list = &sma->sems[semnum].pending_const;
865
866	list_for_each_entry_safe(q, tmp, pending_list, list) {
867	int error = perform_atomic_semop(sma, q);
868
869	if (error > 0)
870	continue;
871	/* operation completed, remove from queue & wakeup */
872	unlink_queue(sma, q);
873
874	wake_up_sem_queue_prepare(q, error, wake_q);
875	if (error == 0)
876	semop_completed = 1;
877	}
878
879	return semop_completed;
880	}
881
882	/**
883	* do_smart_wakeup_zero - wakeup all wait for zero tasks
884	* @sma: semaphore array
885	* @sops: operations that were performed
886	* @nsops: number of operations
887	* @wake_q: lockless wake-queue head
888	*
889	* Checks all required queue for wait-for-zero operations, based
890	* on the actual changes that were performed on the semaphore array.
891	* The function returns 1 if at least one operation was completed successfully.
892	*/
893	static int do_smart_wakeup_zero(struct sem_array sma, struct sembuf sops,
894	int nsops, struct wake_q_head *wake_q)
895	{
896	int i;
897	int semop_completed = 0;
898	int got_zero = 0;
899
900	/* first: the per-semaphore queues, if known */
901	if (sops) {
902	for (i = 0; i < nsops; i++) {
903	int num = sops[i].sem_num;
904
905	if (sma->sems[num].semval == 0) {
906	got_zero = 1;
907	semop_completed \|= wake_const_ops(sma, num, wake_q);
908	}
909	}
910	} else {
911	/*
912	* No sops means modified semaphores not known.
913	* Assume all were changed.
914	*/
915	for (i = 0; i < sma->sem_nsems; i++) {
916	if (sma->sems[i].semval == 0) {
917	got_zero = 1;
918	semop_completed \|= wake_const_ops(sma, i, wake_q);
919	}
920	}
921	}
922	/*
923	* If one of the modified semaphores got 0,
924	* then check the global queue, too.
925	*/
926	if (got_zero)
927	semop_completed \|= wake_const_ops(sma, -1, wake_q);
928
929	return semop_completed;
930	}
931
932
933	/**
934	* update_queue - look for tasks that can be completed.
935	* @sma: semaphore array.
936	* @semnum: semaphore that was modified.
937	* @wake_q: lockless wake-queue head.
938	*
939	* update_queue must be called after a semaphore in a semaphore array
940	* was modified. If multiple semaphores were modified, update_queue must
941	* be called with semnum = -1, as well as with the number of each modified
942	* semaphore.
943	* The tasks that must be woken up are added to @wake_q. The return code
944	* is stored in q->pid.
945	* The function internally checks if const operations can now succeed.
946	*
947	* The function return 1 if at least one semop was completed successfully.
948	*/
949	static int update_queue(struct sem_array sma, int semnum, struct wake_q_head wake_q)
950	{
951	struct sem_queue q, tmp;
952	struct list_head *pending_list;
953	int semop_completed = 0;
954
955	if (semnum == -1)
956	pending_list = &sma->pending_alter;
957	else
958	pending_list = &sma->sems[semnum].pending_alter;
959
960	again:
961	list_for_each_entry_safe(q, tmp, pending_list, list) {
962	int error, restart;
963
964	/* If we are scanning the single sop, per-semaphore list of
965	* one semaphore and that semaphore is 0, then it is not
966	* necessary to scan further: simple increments
967	* that affect only one entry succeed immediately and cannot
968	* be in the per semaphore pending queue, and decrements
969	* cannot be successful if the value is already 0.
970	*/
971	if (semnum != -1 && sma->sems[semnum].semval == 0)
972	break;
973
974	error = perform_atomic_semop(sma, q);
975
976	/* Does q->sleeper still need to sleep? */
977	if (error > 0)
978	continue;
979
980	unlink_queue(sma, q);
981
982	if (error) {
983	restart = 0;
984	} else {
985	semop_completed = 1;
986	do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
987	restart = check_restart(sma, q);
988	}
989
990	wake_up_sem_queue_prepare(q, error, wake_q);
991	if (restart)
992	goto again;
993	}
994	return semop_completed;
995	}
996
997	/**
998	* set_semotime - set sem_otime
999	* @sma: semaphore array
1000	* @sops: operations that modified the array, may be NULL
1001	*
1002	* sem_otime is replicated to avoid cache line trashing.
1003	* This function sets one instance to the current time.
1004	*/
1005	static void set_semotime(struct sem_array sma, struct sembuf sops)
1006	{
1007	if (sops == NULL) {
1008	sma->sems[0].sem_otime = ktime_get_real_seconds();
1009	} else {
1010	sma->sems[sops[0].sem_num].sem_otime =
1011	ktime_get_real_seconds();
1012	}
1013	}
1014
1015	/**
1016	* do_smart_update - optimized update_queue
1017	* @sma: semaphore array
1018	* @sops: operations that were performed
1019	* @nsops: number of operations
1020	* @otime: force setting otime
1021	* @wake_q: lockless wake-queue head
1022	*
1023	* do_smart_update() does the required calls to update_queue and wakeup_zero,
1024	* based on the actual changes that were performed on the semaphore array.
1025	* Note that the function does not do the actual wake-up: the caller is
1026	* responsible for calling wake_up_q().
1027	* It is safe to perform this call after dropping all locks.
1028	*/
1029	static void do_smart_update(struct sem_array sma, struct sembuf sops, int nsops,
1030	int otime, struct wake_q_head *wake_q)
1031	{
1032	int i;
1033
1034	otime \|= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
1035
1036	if (!list_empty(&sma->pending_alter)) {
1037	/* semaphore array uses the global queue - just process it. */
1038	otime \|= update_queue(sma, -1, wake_q);
1039	} else {
1040	if (!sops) {
1041	/*
1042	* No sops, thus the modified semaphores are not
1043	* known. Check all.
1044	*/
1045	for (i = 0; i < sma->sem_nsems; i++)
1046	otime \|= update_queue(sma, i, wake_q);
1047	} else {
1048	/*
1049	* Check the semaphores that were increased:
1050	* - No complex ops, thus all sleeping ops are
1051	* decrease.
1052	* - if we decreased the value, then any sleeping
1053	* semaphore ops won't be able to run: If the
1054	* previous value was too small, then the new
1055	* value will be too small, too.
1056	*/
1057	for (i = 0; i < nsops; i++) {
1058	if (sops[i].sem_op > 0) {
1059	otime \|= update_queue(sma,
1060	sops[i].sem_num, wake_q);
1061	}
1062	}
1063	}
1064	}
1065	if (otime)
1066	set_semotime(sma, sops);
1067	}
1068
1069	/*
1070	* check_qop: Test if a queued operation sleeps on the semaphore semnum
1071	*/
1072	static int check_qop(struct sem_array sma, int semnum, struct sem_queue q,
1073	bool count_zero)
1074	{
1075	struct sembuf *sop = q->blocking;
1076
1077	/*
1078	* Linux always (since 0.99.10) reported a task as sleeping on all
1079	* semaphores. This violates SUS, therefore it was changed to the
1080	* standard compliant behavior.
1081	* Give the administrators a chance to notice that an application
1082	* might misbehave because it relies on the Linux behavior.
1083	*/
1084	pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1085	"The task %s (%d) triggered the difference, watch for misbehavior.\n",
1086	current->comm, task_pid_nr(current));
1087
1088	if (sop->sem_num != semnum)
1089	return 0;
1090
1091	if (count_zero && sop->sem_op == 0)
1092	return 1;
1093	if (!count_zero && sop->sem_op < 0)
1094	return 1;
1095
1096	return 0;
1097	}
1098
1099	/* The following counts are associated to each semaphore:
1100	* semncnt number of tasks waiting on semval being nonzero
1101	* semzcnt number of tasks waiting on semval being zero
1102	*
1103	* Per definition, a task waits only on the semaphore of the first semop
1104	* that cannot proceed, even if additional operation would block, too.
1105	*/
1106	static int count_semcnt(struct sem_array *sma, ushort semnum,
1107	bool count_zero)
1108	{
1109	struct list_head *l;
1110	struct sem_queue *q;
1111	int semcnt;
1112
1113	semcnt = 0;
1114	/* First: check the simple operations. They are easy to evaluate */
1115	if (count_zero)
1116	l = &sma->sems[semnum].pending_const;
1117	else
1118	l = &sma->sems[semnum].pending_alter;
1119
1120	list_for_each_entry(q, l, list) {
1121	/* all task on a per-semaphore list sleep on exactly
1122	* that semaphore
1123	*/
1124	semcnt++;
1125	}
1126
1127	/* Then: check the complex operations. */
1128	list_for_each_entry(q, &sma->pending_alter, list) {
1129	semcnt += check_qop(sma, semnum, q, count_zero);
1130	}
1131	if (count_zero) {
1132	list_for_each_entry(q, &sma->pending_const, list) {
1133	semcnt += check_qop(sma, semnum, q, count_zero);
1134	}
1135	}
1136	return semcnt;
1137	}
1138
1139	/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1140	* as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1141	* remains locked on exit.
1142	*/
1143	static void freeary(struct ipc_namespace ns, struct kern_ipc_perm ipcp)
1144	{
1145	struct sem_undo un, tu;
1146	struct sem_queue q, tq;
1147	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1148	int i;
1149	DEFINE_WAKE_Q(wake_q);
1150
1151	/* Free the existing undo structures for this semaphore set. */
1152	ipc_assert_locked_object(&sma->sem_perm);
1153	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1154	list_del(&un->list_id);
1155	spin_lock(&un->ulp->lock);
1156	un->semid = -1;
1157	list_del_rcu(&un->list_proc);
1158	spin_unlock(&un->ulp->lock);
1159	kvfree_rcu(un, rcu);
1160	}
1161
1162	/* Wake up all pending processes and let them fail with EIDRM. */
1163	list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1164	unlink_queue(sma, q);
1165	wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1166	}
1167
1168	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1169	unlink_queue(sma, q);
1170	wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1171	}
1172	for (i = 0; i < sma->sem_nsems; i++) {
1173	struct sem *sem = &sma->sems[i];
1174	list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1175	unlink_queue(sma, q);
1176	wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1177	}
1178	list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1179	unlink_queue(sma, q);
1180	wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1181	}
1182	ipc_update_pid(&sem->sempid, NULL);
1183	}
1184
1185	/* Remove the semaphore set from the IDR */
1186	sem_rmid(ns, sma);
1187	sem_unlock(sma, -1);
1188	rcu_read_unlock();
1189
1190	wake_up_q(&wake_q);
1191	ns->used_sems -= sma->sem_nsems;
1192	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1193	}
1194
1195	static unsigned long copy_semid_to_user(void __user buf, struct semid64_ds in, int version)
1196	{
1197	switch (version) {
1198	case IPC_64:
1199	return copy_to_user(buf, in, sizeof(*in));
1200	case IPC_OLD:
1201	{
1202	struct semid_ds out;
1203
1204	memset(&out, 0, sizeof(out));
1205
1206	ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1207
1208	out.sem_otime = in->sem_otime;
1209	out.sem_ctime = in->sem_ctime;
1210	out.sem_nsems = in->sem_nsems;
1211
1212	return copy_to_user(buf, &out, sizeof(out));
1213	}
1214	default:
1215	return -EINVAL;
1216	}
1217	}
1218
1219	static time64_t get_semotime(struct sem_array *sma)
1220	{
1221	int i;
1222	time64_t res;
1223
1224	res = sma->sems[0].sem_otime;
1225	for (i = 1; i < sma->sem_nsems; i++) {
1226	time64_t to = sma->sems[i].sem_otime;
1227
1228	if (to > res)
1229	res = to;
1230	}
1231	return res;
1232	}
1233
1234	static int semctl_stat(struct ipc_namespace *ns, int semid,
1235	int cmd, struct semid64_ds *semid64)
1236	{
1237	struct sem_array *sma;
1238	time64_t semotime;
1239	int err;
1240
1241	memset(semid64, 0, sizeof(*semid64));
1242
1243	rcu_read_lock();
1244	if (cmd == SEM_STAT \|\| cmd == SEM_STAT_ANY) {
1245	sma = sem_obtain_object(ns, semid);
1246	if (IS_ERR(sma)) {
1247	err = PTR_ERR(sma);
1248	goto out_unlock;
1249	}
1250	} else { /* IPC_STAT */
1251	sma = sem_obtain_object_check(ns, semid);
1252	if (IS_ERR(sma)) {
1253	err = PTR_ERR(sma);
1254	goto out_unlock;
1255	}
1256	}
1257
1258	/* see comment for SHM_STAT_ANY */
1259	if (cmd == SEM_STAT_ANY)
1260	audit_ipc_obj(&sma->sem_perm);
1261	else {
1262	err = -EACCES;
1263	if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1264	goto out_unlock;
1265	}
1266
1267	err = security_sem_semctl(&sma->sem_perm, cmd);
1268	if (err)
1269	goto out_unlock;
1270
1271	ipc_lock_object(&sma->sem_perm);
1272
1273	if (!ipc_valid_object(&sma->sem_perm)) {
1274	ipc_unlock_object(&sma->sem_perm);
1275	err = -EIDRM;
1276	goto out_unlock;
1277	}
1278
1279	kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
1280	semotime = get_semotime(sma);
1281	semid64->sem_otime = semotime;
1282	semid64->sem_ctime = sma->sem_ctime;
1283	#ifndef CONFIG_64BIT
1284	semid64->sem_otime_high = semotime >> 32;
1285	semid64->sem_ctime_high = sma->sem_ctime >> 32;
1286	#endif
1287	semid64->sem_nsems = sma->sem_nsems;
1288
1289	if (cmd == IPC_STAT) {
1290	/*
1291	* As defined in SUS:
1292	* Return 0 on success
1293	*/
1294	err = 0;
1295	} else {
1296	/*
1297	* SEM_STAT and SEM_STAT_ANY (both Linux specific)
1298	* Return the full id, including the sequence number
1299	*/
1300	err = sma->sem_perm.id;
1301	}
1302	ipc_unlock_object(&sma->sem_perm);
1303	out_unlock:
1304	rcu_read_unlock();
1305	return err;
1306	}
1307
1308	static int semctl_info(struct ipc_namespace *ns, int semid,
1309	int cmd, void __user *p)
1310	{
1311	struct seminfo seminfo;
1312	int max_idx;
1313	int err;
1314
1315	err = security_sem_semctl(NULL, cmd);
1316	if (err)
1317	return err;
1318
1319	memset(&seminfo, 0, sizeof(seminfo));
1320	seminfo.semmni = ns->sc_semmni;
1321	seminfo.semmns = ns->sc_semmns;
1322	seminfo.semmsl = ns->sc_semmsl;
1323	seminfo.semopm = ns->sc_semopm;
1324	seminfo.semvmx = SEMVMX;
1325	seminfo.semmnu = SEMMNU;
1326	seminfo.semmap = SEMMAP;
1327	seminfo.semume = SEMUME;
1328	down_read(&sem_ids(ns).rwsem);
1329	if (cmd == SEM_INFO) {
1330	seminfo.semusz = sem_ids(ns).in_use;
1331	seminfo.semaem = ns->used_sems;
1332	} else {
1333	seminfo.semusz = SEMUSZ;
1334	seminfo.semaem = SEMAEM;
1335	}
1336	max_idx = ipc_get_maxidx(&sem_ids(ns));
1337	up_read(&sem_ids(ns).rwsem);
1338	if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1339	return -EFAULT;
1340	return (max_idx < 0) ? 0 : max_idx;
1341	}
1342
1343	static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1344	int val)
1345	{
1346	struct sem_undo *un;
1347	struct sem_array *sma;
1348	struct sem *curr;
1349	int err;
1350	DEFINE_WAKE_Q(wake_q);
1351
1352	if (val > SEMVMX \|\| val < 0)
1353	return -ERANGE;
1354
1355	rcu_read_lock();
1356	sma = sem_obtain_object_check(ns, semid);
1357	if (IS_ERR(sma)) {
1358	rcu_read_unlock();
1359	return PTR_ERR(sma);
1360	}
1361
1362	if (semnum < 0 \|\| semnum >= sma->sem_nsems) {
1363	rcu_read_unlock();
1364	return -EINVAL;
1365	}
1366
1367
1368	if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1369	rcu_read_unlock();
1370	return -EACCES;
1371	}
1372
1373	err = security_sem_semctl(&sma->sem_perm, SETVAL);
1374	if (err) {
1375	rcu_read_unlock();
1376	return -EACCES;
1377	}
1378
1379	sem_lock(sma, NULL, -1);
1380
1381	if (!ipc_valid_object(&sma->sem_perm)) {
1382	sem_unlock(sma, -1);
1383	rcu_read_unlock();
1384	return -EIDRM;
1385	}
1386
1387	semnum = array_index_nospec(semnum, sma->sem_nsems);
1388	curr = &sma->sems[semnum];
1389
1390	ipc_assert_locked_object(&sma->sem_perm);
1391	list_for_each_entry(un, &sma->list_id, list_id)
1392	un->semadj[semnum] = 0;
1393
1394	curr->semval = val;
1395	ipc_update_pid(&curr->sempid, task_tgid(current));
1396	sma->sem_ctime = ktime_get_real_seconds();
1397	/* maybe some queued-up processes were waiting for this */
1398	do_smart_update(sma, NULL, 0, 0, &wake_q);
1399	sem_unlock(sma, -1);
1400	rcu_read_unlock();
1401	wake_up_q(&wake_q);
1402	return 0;
1403	}
1404
1405	static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1406	int cmd, void __user *p)
1407	{
1408	struct sem_array *sma;
1409	struct sem *curr;
1410	int err, nsems;
1411	ushort fast_sem_io[SEMMSL_FAST];
1412	ushort *sem_io = fast_sem_io;
1413	DEFINE_WAKE_Q(wake_q);
1414
1415	rcu_read_lock();
1416	sma = sem_obtain_object_check(ns, semid);
1417	if (IS_ERR(sma)) {
1418	rcu_read_unlock();
1419	return PTR_ERR(sma);
1420	}
1421
1422	nsems = sma->sem_nsems;
1423
1424	err = -EACCES;
1425	if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1426	goto out_rcu_wakeup;
1427
1428	err = security_sem_semctl(&sma->sem_perm, cmd);
1429	if (err)
1430	goto out_rcu_wakeup;
1431
1432	switch (cmd) {
1433	case GETALL:
1434	{
1435	ushort __user *array = p;
1436	int i;
1437
1438	sem_lock(sma, NULL, -1);
1439	if (!ipc_valid_object(&sma->sem_perm)) {
1440	err = -EIDRM;
1441	goto out_unlock;
1442	}
1443	if (nsems > SEMMSL_FAST) {
1444	if (!ipc_rcu_getref(&sma->sem_perm)) {
1445	err = -EIDRM;
1446	goto out_unlock;
1447	}
1448	sem_unlock(sma, -1);
1449	rcu_read_unlock();
1450	sem_io = kvmalloc_array(nsems, sizeof(ushort),
1451	GFP_KERNEL);
1452	if (sem_io == NULL) {
1453	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1454	return -ENOMEM;
1455	}
1456
1457	rcu_read_lock();
1458	sem_lock_and_putref(sma);
1459	if (!ipc_valid_object(&sma->sem_perm)) {
1460	err = -EIDRM;
1461	goto out_unlock;
1462	}
1463	}
1464	for (i = 0; i < sma->sem_nsems; i++)
1465	sem_io[i] = sma->sems[i].semval;
1466	sem_unlock(sma, -1);
1467	rcu_read_unlock();
1468	err = 0;
1469	if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1470	err = -EFAULT;
1471	goto out_free;
1472	}
1473	case SETALL:
1474	{
1475	int i;
1476	struct sem_undo *un;
1477
1478	if (!ipc_rcu_getref(&sma->sem_perm)) {
1479	err = -EIDRM;
1480	goto out_rcu_wakeup;
1481	}
1482	rcu_read_unlock();
1483
1484	if (nsems > SEMMSL_FAST) {
1485	sem_io = kvmalloc_array(nsems, sizeof(ushort),
1486	GFP_KERNEL);
1487	if (sem_io == NULL) {
1488	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1489	return -ENOMEM;
1490	}
1491	}
1492
1493	if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1494	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1495	err = -EFAULT;
1496	goto out_free;
1497	}
1498
1499	for (i = 0; i < nsems; i++) {
1500	if (sem_io[i] > SEMVMX) {
1501	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1502	err = -ERANGE;
1503	goto out_free;
1504	}
1505	}
1506	rcu_read_lock();
1507	sem_lock_and_putref(sma);
1508	if (!ipc_valid_object(&sma->sem_perm)) {
1509	err = -EIDRM;
1510	goto out_unlock;
1511	}
1512
1513	for (i = 0; i < nsems; i++) {
1514	sma->sems[i].semval = sem_io[i];
1515	ipc_update_pid(&sma->sems[i].sempid, task_tgid(current));
1516	}
1517
1518	ipc_assert_locked_object(&sma->sem_perm);
1519	list_for_each_entry(un, &sma->list_id, list_id) {
1520	for (i = 0; i < nsems; i++)
1521	un->semadj[i] = 0;
1522	}
1523	sma->sem_ctime = ktime_get_real_seconds();
1524	/* maybe some queued-up processes were waiting for this */
1525	do_smart_update(sma, NULL, 0, 0, &wake_q);
1526	err = 0;
1527	goto out_unlock;
1528	}
1529	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1530	}
1531	err = -EINVAL;
1532	if (semnum < 0 \|\| semnum >= nsems)
1533	goto out_rcu_wakeup;
1534
1535	sem_lock(sma, NULL, -1);
1536	if (!ipc_valid_object(&sma->sem_perm)) {
1537	err = -EIDRM;
1538	goto out_unlock;
1539	}
1540
1541	semnum = array_index_nospec(semnum, nsems);
1542	curr = &sma->sems[semnum];
1543
1544	switch (cmd) {
1545	case GETVAL:
1546	err = curr->semval;
1547	goto out_unlock;
1548	case GETPID:
1549	err = pid_vnr(curr->sempid);
1550	goto out_unlock;
1551	case GETNCNT:
1552	err = count_semcnt(sma, semnum, 0);
1553	goto out_unlock;
1554	case GETZCNT:
1555	err = count_semcnt(sma, semnum, 1);
1556	goto out_unlock;
1557	}
1558
1559	out_unlock:
1560	sem_unlock(sma, -1);
1561	out_rcu_wakeup:
1562	rcu_read_unlock();
1563	wake_up_q(&wake_q);
1564	out_free:
1565	if (sem_io != fast_sem_io)
1566	kvfree(sem_io);
1567	return err;
1568	}
1569
1570	static inline unsigned long
1571	copy_semid_from_user(struct semid64_ds out, void __user buf, int version)
1572	{
1573	switch (version) {
1574	case IPC_64:
1575	if (copy_from_user(out, buf, sizeof(*out)))
1576	return -EFAULT;
1577	return 0;
1578	case IPC_OLD:
1579	{
1580	struct semid_ds tbuf_old;
1581
1582	if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1583	return -EFAULT;
1584
1585	out->sem_perm.uid = tbuf_old.sem_perm.uid;
1586	out->sem_perm.gid = tbuf_old.sem_perm.gid;
1587	out->sem_perm.mode = tbuf_old.sem_perm.mode;
1588
1589	return 0;
1590	}
1591	default:
1592	return -EINVAL;
1593	}
1594	}
1595
1596	/*
1597	* This function handles some semctl commands which require the rwsem
1598	* to be held in write mode.
1599	* NOTE: no locks must be held, the rwsem is taken inside this function.
1600	*/
1601	static int semctl_down(struct ipc_namespace *ns, int semid,
1602	int cmd, struct semid64_ds *semid64)
1603	{
1604	struct sem_array *sma;
1605	int err;
1606	struct kern_ipc_perm *ipcp;
1607
1608	down_write(&sem_ids(ns).rwsem);
1609	rcu_read_lock();
1610
1611	ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
1612	&semid64->sem_perm, 0);
1613	if (IS_ERR(ipcp)) {
1614	err = PTR_ERR(ipcp);
1615	goto out_unlock1;
1616	}
1617
1618	sma = container_of(ipcp, struct sem_array, sem_perm);
1619
1620	err = security_sem_semctl(&sma->sem_perm, cmd);
1621	if (err)
1622	goto out_unlock1;
1623
1624	switch (cmd) {
1625	case IPC_RMID:
1626	sem_lock(sma, NULL, -1);
1627	/* freeary unlocks the ipc object and rcu */
1628	freeary(ns, ipcp);
1629	goto out_up;
1630	case IPC_SET:
1631	sem_lock(sma, NULL, -1);
1632	err = ipc_update_perm(&semid64->sem_perm, ipcp);
1633	if (err)
1634	goto out_unlock0;
1635	sma->sem_ctime = ktime_get_real_seconds();
1636	break;
1637	default:
1638	err = -EINVAL;
1639	goto out_unlock1;
1640	}
1641
1642	out_unlock0:
1643	sem_unlock(sma, -1);
1644	out_unlock1:
1645	rcu_read_unlock();
1646	out_up:
1647	up_write(&sem_ids(ns).rwsem);
1648	return err;
1649	}
1650
1651	static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version)
1652	{
1653	struct ipc_namespace *ns;
1654	void __user p = (void __user )arg;
1655	struct semid64_ds semid64;
1656	int err;
1657
1658	if (semid < 0)
1659	return -EINVAL;
1660
1661	ns = current->nsproxy->ipc_ns;
1662
1663	switch (cmd) {
1664	case IPC_INFO:
1665	case SEM_INFO:
1666	return semctl_info(ns, semid, cmd, p);
1667	case IPC_STAT:
1668	case SEM_STAT:
1669	case SEM_STAT_ANY:
1670	err = semctl_stat(ns, semid, cmd, &semid64);
1671	if (err < 0)
1672	return err;
1673	if (copy_semid_to_user(p, &semid64, version))
1674	err = -EFAULT;
1675	return err;
1676	case GETALL:
1677	case GETVAL:
1678	case GETPID:
1679	case GETNCNT:
1680	case GETZCNT:
1681	case SETALL:
1682	return semctl_main(ns, semid, semnum, cmd, p);
1683	case SETVAL: {
1684	int val;
1685	#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1686	/* big-endian 64bit */
1687	val = arg >> 32;
1688	#else
1689	/* 32bit or little-endian 64bit */
1690	val = arg;
1691	#endif
1692	return semctl_setval(ns, semid, semnum, val);
1693	}
1694	case IPC_SET:
1695	if (copy_semid_from_user(&semid64, p, version))
1696	return -EFAULT;
1697	fallthrough;
1698	case IPC_RMID:
1699	return semctl_down(ns, semid, cmd, &semid64);
1700	default:
1701	return -EINVAL;
1702	}
1703	}
1704
1705	SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1706	{
1707	return ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1708	}
1709
1710	#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
1711	long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg)
1712	{
1713	int version = ipc_parse_version(&cmd);
1714
1715	return ksys_semctl(semid, semnum, cmd, arg, version);
1716	}
1717
1718	SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1719	{
1720	return ksys_old_semctl(semid, semnum, cmd, arg);
1721	}
1722	#endif
1723
1724	#ifdef CONFIG_COMPAT
1725
1726	struct compat_semid_ds {
1727	struct compat_ipc_perm sem_perm;
1728	old_time32_t sem_otime;
1729	old_time32_t sem_ctime;
1730	compat_uptr_t sem_base;
1731	compat_uptr_t sem_pending;
1732	compat_uptr_t sem_pending_last;
1733	compat_uptr_t undo;
1734	unsigned short sem_nsems;
1735	};
1736
1737	static int copy_compat_semid_from_user(struct semid64_ds out, void __user buf,
1738	int version)
1739	{
1740	memset(out, 0, sizeof(*out));
1741	if (version == IPC_64) {
1742	struct compat_semid64_ds __user *p = buf;
1743	return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm);
1744	} else {
1745	struct compat_semid_ds __user *p = buf;
1746	return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm);
1747	}
1748	}
1749
1750	static int copy_compat_semid_to_user(void __user buf, struct semid64_ds in,
1751	int version)
1752	{
1753	if (version == IPC_64) {
1754	struct compat_semid64_ds v;
1755	memset(&v, 0, sizeof(v));
1756	to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm);
1757	v.sem_otime = lower_32_bits(in->sem_otime);
1758	v.sem_otime_high = upper_32_bits(in->sem_otime);
1759	v.sem_ctime = lower_32_bits(in->sem_ctime);
1760	v.sem_ctime_high = upper_32_bits(in->sem_ctime);
1761	v.sem_nsems = in->sem_nsems;
1762	return copy_to_user(buf, &v, sizeof(v));
1763	} else {
1764	struct compat_semid_ds v;
1765	memset(&v, 0, sizeof(v));
1766	to_compat_ipc_perm(&v.sem_perm, &in->sem_perm);
1767	v.sem_otime = in->sem_otime;
1768	v.sem_ctime = in->sem_ctime;
1769	v.sem_nsems = in->sem_nsems;
1770	return copy_to_user(buf, &v, sizeof(v));
1771	}
1772	}
1773
1774	static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version)
1775	{
1776	void __user *p = compat_ptr(arg);
1777	struct ipc_namespace *ns;
1778	struct semid64_ds semid64;
1779	int err;
1780
1781	ns = current->nsproxy->ipc_ns;
1782
1783	if (semid < 0)
1784	return -EINVAL;
1785
1786	switch (cmd & (~IPC_64)) {
1787	case IPC_INFO:
1788	case SEM_INFO:
1789	return semctl_info(ns, semid, cmd, p);
1790	case IPC_STAT:
1791	case SEM_STAT:
1792	case SEM_STAT_ANY:
1793	err = semctl_stat(ns, semid, cmd, &semid64);
1794	if (err < 0)
1795	return err;
1796	if (copy_compat_semid_to_user(p, &semid64, version))
1797	err = -EFAULT;
1798	return err;
1799	case GETVAL:
1800	case GETPID:
1801	case GETNCNT:
1802	case GETZCNT:
1803	case GETALL:
1804	case SETALL:
1805	return semctl_main(ns, semid, semnum, cmd, p);
1806	case SETVAL:
1807	return semctl_setval(ns, semid, semnum, arg);
1808	case IPC_SET:
1809	if (copy_compat_semid_from_user(&semid64, p, version))
1810	return -EFAULT;
1811	fallthrough;
1812	case IPC_RMID:
1813	return semctl_down(ns, semid, cmd, &semid64);
1814	default:
1815	return -EINVAL;
1816	}
1817	}
1818
1819	COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
1820	{
1821	return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1822	}
1823
1824	#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
1825	long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg)
1826	{
1827	int version = compat_ipc_parse_version(&cmd);
1828
1829	return compat_ksys_semctl(semid, semnum, cmd, arg, version);
1830	}
1831
1832	COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg)
1833	{
1834	return compat_ksys_old_semctl(semid, semnum, cmd, arg);
1835	}
1836	#endif
1837	#endif
1838
1839	/* If the task doesn't already have a undo_list, then allocate one
1840	* here. We guarantee there is only one thread using this undo list,
1841	* and current is THE ONE
1842	*
1843	* If this allocation and assignment succeeds, but later
1844	* portions of this code fail, there is no need to free the sem_undo_list.
1845	* Just let it stay associated with the task, and it'll be freed later
1846	* at exit time.
1847	*
1848	* This can block, so callers must hold no locks.
1849	*/
1850	static inline int get_undo_list(struct sem_undo_list **undo_listp)
1851	{
1852	struct sem_undo_list *undo_list;
1853
1854	undo_list = current->sysvsem.undo_list;
1855	if (!undo_list) {
1856	undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL_ACCOUNT);
1857	if (undo_list == NULL)
1858	return -ENOMEM;
1859	spin_lock_init(&undo_list->lock);
1860	refcount_set(&undo_list->refcnt, 1);
1861	INIT_LIST_HEAD(&undo_list->list_proc);
1862
1863	current->sysvsem.undo_list = undo_list;
1864	}
1865	*undo_listp = undo_list;
1866	return 0;
1867	}
1868
1869	static struct sem_undo __lookup_undo(struct sem_undo_list ulp, int semid)
1870	{
1871	struct sem_undo *un;
1872
1873	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc,
1874	spin_is_locked(&ulp->lock)) {
1875	if (un->semid == semid)
1876	return un;
1877	}
1878	return NULL;
1879	}
1880
1881	static struct sem_undo lookup_undo(struct sem_undo_list ulp, int semid)
1882	{
1883	struct sem_undo *un;
1884
1885	assert_spin_locked(&ulp->lock);
1886
1887	un = __lookup_undo(ulp, semid);
1888	if (un) {
1889	list_del_rcu(&un->list_proc);
1890	list_add_rcu(&un->list_proc, &ulp->list_proc);
1891	}
1892	return un;
1893	}
1894
1895	/**
1896	* find_alloc_undo - lookup (and if not present create) undo array
1897	* @ns: namespace
1898	* @semid: semaphore array id
1899	*
1900	* The function looks up (and if not present creates) the undo structure.
1901	* The size of the undo structure depends on the size of the semaphore
1902	* array, thus the alloc path is not that straightforward.
1903	* Lifetime-rules: sem_undo is rcu-protected, on success, the function
1904	* performs a rcu_read_lock().
1905	*/
1906	static struct sem_undo find_alloc_undo(struct ipc_namespace ns, int semid)
1907	{
1908	struct sem_array *sma;
1909	struct sem_undo_list *ulp;
1910	struct sem_undo un, new;
1911	int nsems, error;
1912
1913	error = get_undo_list(&ulp);
1914	if (error)
1915	return ERR_PTR(error);
1916
1917	rcu_read_lock();
1918	spin_lock(&ulp->lock);
1919	un = lookup_undo(ulp, semid);
1920	spin_unlock(&ulp->lock);
1921	if (likely(un != NULL))
1922	goto out;
1923
1924	/* no undo structure around - allocate one. */
1925	/* step 1: figure out the size of the semaphore array */
1926	sma = sem_obtain_object_check(ns, semid);
1927	if (IS_ERR(sma)) {
1928	rcu_read_unlock();
1929	return ERR_CAST(sma);
1930	}
1931
1932	nsems = sma->sem_nsems;
1933	if (!ipc_rcu_getref(&sma->sem_perm)) {
1934	rcu_read_unlock();
1935	un = ERR_PTR(-EIDRM);
1936	goto out;
1937	}
1938	rcu_read_unlock();
1939
1940	/* step 2: allocate new undo structure */
1941	new = kvzalloc(struct_size(new, semadj, nsems), GFP_KERNEL_ACCOUNT);
1942	if (!new) {
1943	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1944	return ERR_PTR(-ENOMEM);
1945	}
1946
1947	/* step 3: Acquire the lock on semaphore array */
1948	rcu_read_lock();
1949	sem_lock_and_putref(sma);
1950	if (!ipc_valid_object(&sma->sem_perm)) {
1951	sem_unlock(sma, -1);
1952	rcu_read_unlock();
1953	kvfree(new);
1954	un = ERR_PTR(-EIDRM);
1955	goto out;
1956	}
1957	spin_lock(&ulp->lock);
1958
1959	/*
1960	* step 4: check for races: did someone else allocate the undo struct?
1961	*/
1962	un = lookup_undo(ulp, semid);
1963	if (un) {
1964	spin_unlock(&ulp->lock);
1965	kvfree(new);
1966	goto success;
1967	}
1968	/* step 5: initialize & link new undo structure */
1969	new->ulp = ulp;
1970	new->semid = semid;
1971	assert_spin_locked(&ulp->lock);
1972	list_add_rcu(&new->list_proc, &ulp->list_proc);
1973	ipc_assert_locked_object(&sma->sem_perm);
1974	list_add(&new->list_id, &sma->list_id);
1975	un = new;
1976	spin_unlock(&ulp->lock);
1977	success:
1978	sem_unlock(sma, -1);
1979	out:
1980	return un;
1981	}
1982
1983	long __do_semtimedop(int semid, struct sembuf *sops,
1984	unsigned nsops, const struct timespec64 *timeout,
1985	struct ipc_namespace *ns)
1986	{
1987	int error = -EINVAL;
1988	struct sem_array *sma;
1989	struct sembuf *sop;
1990	struct sem_undo *un;
1991	int max, locknum;
1992	bool undos = false, alter = false, dupsop = false;
1993	struct sem_queue queue;
1994	unsigned long dup = 0;
1995	ktime_t expires, *exp = NULL;
1996	bool timed_out = false;
1997
1998	if (nsops < 1 \|\| semid < 0)
1999	return -EINVAL;
2000	if (nsops > ns->sc_semopm)
2001	return -E2BIG;
2002
2003	if (timeout) {
2004	if (!timespec64_valid(timeout))
2005	return -EINVAL;
2006	expires = ktime_add_safe(ktime_get(),
2007	timespec64_to_ktime(*timeout));
2008	exp = &expires;
2009	}
2010
2011
2012	max = 0;
2013	for (sop = sops; sop < sops + nsops; sop++) {
2014	unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
2015
2016	if (sop->sem_num >= max)
2017	max = sop->sem_num;
2018	if (sop->sem_flg & SEM_UNDO)
2019	undos = true;
2020	if (dup & mask) {
2021	/*
2022	* There was a previous alter access that appears
2023	* to have accessed the same semaphore, thus use
2024	* the dupsop logic. "appears", because the detection
2025	* can only check % BITS_PER_LONG.
2026	*/
2027	dupsop = true;
2028	}
2029	if (sop->sem_op != 0) {
2030	alter = true;
2031	dup \|= mask;
2032	}
2033	}
2034
2035	if (undos) {
2036	/* On success, find_alloc_undo takes the rcu_read_lock */
2037	un = find_alloc_undo(ns, semid);
2038	if (IS_ERR(un)) {
2039	error = PTR_ERR(un);
2040	goto out;
2041	}
2042	} else {
2043	un = NULL;
2044	rcu_read_lock();
2045	}
2046
2047	sma = sem_obtain_object_check(ns, semid);
2048	if (IS_ERR(sma)) {
2049	rcu_read_unlock();
2050	error = PTR_ERR(sma);
2051	goto out;
2052	}
2053
2054	error = -EFBIG;
2055	if (max >= sma->sem_nsems) {
2056	rcu_read_unlock();
2057	goto out;
2058	}
2059
2060	error = -EACCES;
2061	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
2062	rcu_read_unlock();
2063	goto out;
2064	}
2065
2066	error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
2067	if (error) {
2068	rcu_read_unlock();
2069	goto out;
2070	}
2071
2072	error = -EIDRM;
2073	locknum = sem_lock(sma, sops, nsops);
2074	/*
2075	* We eventually might perform the following check in a lockless
2076	* fashion, considering ipc_valid_object() locking constraints.
2077	* If nsops == 1 and there is no contention for sem_perm.lock, then
2078	* only a per-semaphore lock is held and it's OK to proceed with the
2079	* check below. More details on the fine grained locking scheme
2080	* entangled here and why it's RMID race safe on comments at sem_lock()
2081	*/
2082	if (!ipc_valid_object(&sma->sem_perm))
2083	goto out_unlock;
2084	/*
2085	* semid identifiers are not unique - find_alloc_undo may have
2086	* allocated an undo structure, it was invalidated by an RMID
2087	* and now a new array with received the same id. Check and fail.
2088	* This case can be detected checking un->semid. The existence of
2089	* "un" itself is guaranteed by rcu.
2090	*/
2091	if (un && un->semid == -1)
2092	goto out_unlock;
2093
2094	queue.sops = sops;
2095	queue.nsops = nsops;
2096	queue.undo = un;
2097	queue.pid = task_tgid(current);
2098	queue.alter = alter;
2099	queue.dupsop = dupsop;
2100
2101	error = perform_atomic_semop(sma, &queue);
2102	if (error == 0) { /* non-blocking successful path */
2103	DEFINE_WAKE_Q(wake_q);
2104
2105	/*
2106	* If the operation was successful, then do
2107	* the required updates.
2108	*/
2109	if (alter)
2110	do_smart_update(sma, sops, nsops, 1, &wake_q);
2111	else
2112	set_semotime(sma, sops);
2113
2114	sem_unlock(sma, locknum);
2115	rcu_read_unlock();
2116	wake_up_q(&wake_q);
2117
2118	goto out;
2119	}
2120	if (error < 0) /* non-blocking error path */
2121	goto out_unlock;
2122
2123	/*
2124	* We need to sleep on this operation, so we put the current
2125	* task into the pending queue and go to sleep.
2126	*/
2127	if (nsops == 1) {
2128	struct sem *curr;
2129	int idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
2130	curr = &sma->sems[idx];
2131
2132	if (alter) {
2133	if (sma->complex_count) {
2134	list_add_tail(&queue.list,
2135	&sma->pending_alter);
2136	} else {
2137
2138	list_add_tail(&queue.list,
2139	&curr->pending_alter);
2140	}
2141	} else {
2142	list_add_tail(&queue.list, &curr->pending_const);
2143	}
2144	} else {
2145	if (!sma->complex_count)
2146	merge_queues(sma);
2147
2148	if (alter)
2149	list_add_tail(&queue.list, &sma->pending_alter);
2150	else
2151	list_add_tail(&queue.list, &sma->pending_const);
2152
2153	sma->complex_count++;
2154	}
2155
2156	do {
2157	/* memory ordering ensured by the lock in sem_lock() */
2158	WRITE_ONCE(queue.status, -EINTR);
2159	queue.sleeper = current;
2160
2161	/* memory ordering is ensured by the lock in sem_lock() */
2162	__set_current_state(TASK_INTERRUPTIBLE);
2163	sem_unlock(sma, locknum);
2164	rcu_read_unlock();
2165
2166	timed_out = !schedule_hrtimeout_range(exp,
2167	current->timer_slack_ns, HRTIMER_MODE_ABS);
2168
2169	/*
2170	* fastpath: the semop has completed, either successfully or
2171	* not, from the syscall pov, is quite irrelevant to us at this
2172	* point; we're done.
2173	*
2174	* We _do_ care, nonetheless, about being awoken by a signal or
2175	* spuriously. The queue.status is checked again in the
2176	* slowpath (aka after taking sem_lock), such that we can detect
2177	* scenarios where we were awakened externally, during the
2178	* window between wake_q_add() and wake_up_q().
2179	*/
2180	rcu_read_lock();
2181	error = READ_ONCE(queue.status);
2182	if (error != -EINTR) {
2183	/* see SEM_BARRIER_2 for purpose/pairing */
2184	smp_acquire__after_ctrl_dep();
2185	rcu_read_unlock();
2186	goto out;
2187	}
2188
2189	locknum = sem_lock(sma, sops, nsops);
2190
2191	if (!ipc_valid_object(&sma->sem_perm))
2192	goto out_unlock;
2193
2194	/*
2195	* No necessity for any barrier: We are protect by sem_lock()
2196	*/
2197	error = READ_ONCE(queue.status);
2198
2199	/*
2200	* If queue.status != -EINTR we are woken up by another process.
2201	* Leave without unlink_queue(), but with sem_unlock().
2202	*/
2203	if (error != -EINTR)
2204	goto out_unlock;
2205
2206	/*
2207	* If an interrupt occurred we have to clean up the queue.
2208	*/
2209	if (timed_out)
2210	error = -EAGAIN;
2211	} while (error == -EINTR && !signal_pending(current)); /* spurious */
2212
2213	unlink_queue(sma, &queue);
2214
2215	out_unlock:
2216	sem_unlock(sma, locknum);
2217	rcu_read_unlock();
2218	out:
2219	return error;
2220	}
2221
2222	static long do_semtimedop(int semid, struct sembuf __user *tsops,
2223	unsigned nsops, const struct timespec64 *timeout)
2224	{
2225	struct sembuf fast_sops[SEMOPM_FAST];
2226	struct sembuf *sops = fast_sops;
2227	struct ipc_namespace *ns;
2228	int ret;
2229
2230	ns = current->nsproxy->ipc_ns;
2231	if (nsops > ns->sc_semopm)
2232	return -E2BIG;
2233	if (nsops < 1)
2234	return -EINVAL;
2235
2236	if (nsops > SEMOPM_FAST) {
2237	sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
2238	if (sops == NULL)
2239	return -ENOMEM;
2240	}
2241
2242	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
2243	ret = -EFAULT;
2244	goto out_free;
2245	}
2246
2247	ret = __do_semtimedop(semid, sops, nsops, timeout, ns);
2248
2249	out_free:
2250	if (sops != fast_sops)
2251	kvfree(sops);
2252
2253	return ret;
2254	}
2255
2256	long ksys_semtimedop(int semid, struct sembuf __user *tsops,
2257	unsigned int nsops, const struct __kernel_timespec __user *timeout)
2258	{
2259	if (timeout) {
2260	struct timespec64 ts;
2261	if (get_timespec64(&ts, timeout))
2262	return -EFAULT;
2263	return do_semtimedop(semid, tsops, nsops, &ts);
2264	}
2265	return do_semtimedop(semid, tsops, nsops, NULL);
2266	}
2267
2268	SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
2269	unsigned int, nsops, const struct __kernel_timespec __user *, timeout)
2270	{
2271	return ksys_semtimedop(semid, tsops, nsops, timeout);
2272	}
2273
2274	#ifdef CONFIG_COMPAT_32BIT_TIME
2275	long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
2276	unsigned int nsops,
2277	const struct old_timespec32 __user *timeout)
2278	{
2279	if (timeout) {
2280	struct timespec64 ts;
2281	if (get_old_timespec32(&ts, timeout))
2282	return -EFAULT;
2283	return do_semtimedop(semid, tsems, nsops, &ts);
2284	}
2285	return do_semtimedop(semid, tsems, nsops, NULL);
2286	}
2287
2288	SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems,
2289	unsigned int, nsops,
2290	const struct old_timespec32 __user *, timeout)
2291	{
2292	return compat_ksys_semtimedop(semid, tsems, nsops, timeout);
2293	}
2294	#endif
2295
2296	SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2297	unsigned, nsops)
2298	{
2299	return do_semtimedop(semid, tsops, nsops, NULL);
2300	}
2301
2302	/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2303	* parent and child tasks.
2304	*/
2305
2306	int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2307	{
2308	struct sem_undo_list *undo_list;
2309	int error;
2310
2311	if (clone_flags & CLONE_SYSVSEM) {
2312	error = get_undo_list(&undo_list);
2313	if (error)
2314	return error;
2315	refcount_inc(&undo_list->refcnt);
2316	tsk->sysvsem.undo_list = undo_list;
2317	} else
2318	tsk->sysvsem.undo_list = NULL;
2319
2320	return 0;
2321	}
2322
2323	/*
2324	* add semadj values to semaphores, free undo structures.
2325	* undo structures are not freed when semaphore arrays are destroyed
2326	* so some of them may be out of date.
2327	* IMPLEMENTATION NOTE: There is some confusion over whether the
2328	* set of adjustments that needs to be done should be done in an atomic
2329	* manner or not. That is, if we are attempting to decrement the semval
2330	* should we queue up and wait until we can do so legally?
2331	* The original implementation attempted to do this (queue and wait).
2332	* The current implementation does not do so. The POSIX standard
2333	* and SVID should be consulted to determine what behavior is mandated.
2334	*/
2335	void exit_sem(struct task_struct *tsk)
2336	{
2337	struct sem_undo_list *ulp;
2338
2339	ulp = tsk->sysvsem.undo_list;
2340	if (!ulp)
2341	return;
2342	tsk->sysvsem.undo_list = NULL;
2343
2344	if (!refcount_dec_and_test(&ulp->refcnt))
2345	return;
2346
2347	for (;;) {
2348	struct sem_array *sma;
2349	struct sem_undo *un;
2350	int semid, i;
2351	DEFINE_WAKE_Q(wake_q);
2352
2353	cond_resched();
2354
2355	rcu_read_lock();
2356	un = list_entry_rcu(ulp->list_proc.next,
2357	struct sem_undo, list_proc);
2358	if (&un->list_proc == &ulp->list_proc) {
2359	/*
2360	* We must wait for freeary() before freeing this ulp,
2361	* in case we raced with last sem_undo. There is a small
2362	* possibility where we exit while freeary() didn't
2363	* finish unlocking sem_undo_list.
2364	*/
2365	spin_lock(&ulp->lock);
2366	spin_unlock(&ulp->lock);
2367	rcu_read_unlock();
2368	break;
2369	}
2370	spin_lock(&ulp->lock);
2371	semid = un->semid;
2372	spin_unlock(&ulp->lock);
2373
2374	/* exit_sem raced with IPC_RMID, nothing to do */
2375	if (semid == -1) {
2376	rcu_read_unlock();
2377	continue;
2378	}
2379
2380	sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2381	/* exit_sem raced with IPC_RMID, nothing to do */
2382	if (IS_ERR(sma)) {
2383	rcu_read_unlock();
2384	continue;
2385	}
2386
2387	sem_lock(sma, NULL, -1);
2388	/* exit_sem raced with IPC_RMID, nothing to do */
2389	if (!ipc_valid_object(&sma->sem_perm)) {
2390	sem_unlock(sma, -1);
2391	rcu_read_unlock();
2392	continue;
2393	}
2394	un = __lookup_undo(ulp, semid);
2395	if (un == NULL) {
2396	/* exit_sem raced with IPC_RMID+semget() that created
2397	* exactly the same semid. Nothing to do.
2398	*/
2399	sem_unlock(sma, -1);
2400	rcu_read_unlock();
2401	continue;
2402	}
2403
2404	/* remove un from the linked lists */
2405	ipc_assert_locked_object(&sma->sem_perm);
2406	list_del(&un->list_id);
2407
2408	spin_lock(&ulp->lock);
2409	list_del_rcu(&un->list_proc);
2410	spin_unlock(&ulp->lock);
2411
2412	/* perform adjustments registered in un */
2413	for (i = 0; i < sma->sem_nsems; i++) {
2414	struct sem *semaphore = &sma->sems[i];
2415	if (un->semadj[i]) {
2416	semaphore->semval += un->semadj[i];
2417	/*
2418	* Range checks of the new semaphore value,
2419	* not defined by sus:
2420	* - Some unices ignore the undo entirely
2421	* (e.g. HP UX 11i 11.22, Tru64 V5.1)
2422	* - some cap the value (e.g. FreeBSD caps
2423	* at 0, but doesn't enforce SEMVMX)
2424	*
2425	* Linux caps the semaphore value, both at 0
2426	* and at SEMVMX.
2427	*
2428	* Manfred <[email protected]>
2429	*/
2430	if (semaphore->semval < 0)
2431	semaphore->semval = 0;
2432	if (semaphore->semval > SEMVMX)
2433	semaphore->semval = SEMVMX;
2434	ipc_update_pid(&semaphore->sempid, task_tgid(current));
2435	}
2436	}
2437	/* maybe some queued-up processes were waiting for this */
2438	do_smart_update(sma, NULL, 0, 1, &wake_q);
2439	sem_unlock(sma, -1);
2440	rcu_read_unlock();
2441	wake_up_q(&wake_q);
2442
2443	kvfree_rcu(un, rcu);
2444	}
2445	kfree(ulp);
2446	}
2447
2448	#ifdef CONFIG_PROC_FS
2449	static int sysvipc_sem_proc_show(struct seq_file s, void it)
2450	{
2451	struct user_namespace *user_ns = seq_user_ns(s);
2452	struct kern_ipc_perm *ipcp = it;
2453	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
2454	time64_t sem_otime;
2455
2456	/*
2457	* The proc interface isn't aware of sem_lock(), it calls
2458	* ipc_lock_object(), i.e. spin_lock(&sma->sem_perm.lock).
2459	* (in sysvipc_find_ipc)
2460	* In order to stay compatible with sem_lock(), we must
2461	* enter / leave complex_mode.
2462	*/
2463	complexmode_enter(sma);
2464
2465	sem_otime = get_semotime(sma);
2466
2467	seq_printf(s,
2468	"%10d %10d %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
2469	sma->sem_perm.key,
2470	sma->sem_perm.id,
2471	sma->sem_perm.mode,
2472	sma->sem_nsems,
2473	from_kuid_munged(user_ns, sma->sem_perm.uid),
2474	from_kgid_munged(user_ns, sma->sem_perm.gid),
2475	from_kuid_munged(user_ns, sma->sem_perm.cuid),
2476	from_kgid_munged(user_ns, sma->sem_perm.cgid),
2477	sem_otime,
2478	sma->sem_ctime);
2479
2480	complexmode_tryleave(sma);
2481
2482	return 0;
2483	}
2484	#endif