xref: /linux/ipc/sem.c (revision df561f66)
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. */
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  *
221  * 2) queue.status: (SEM_BARRIER_2)
222  * Initialization is done while holding sem_lock(), so no further barrier is
223  * required.
224  * Setting it to a result code is a RELEASE, this is ensured by both a
225  * smp_store_release() (for case a) and while holding sem_lock()
226  * (for case b).
227  * The AQUIRE when reading the result code without holding sem_lock() is
228  * achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep().
229  * (case a above).
230  * Reading the result code while holding sem_lock() needs no further barriers,
231  * the locks inside sem_lock() enforce ordering (case b above)
232  *
233  * 3) current->state:
234  * current->state is set to TASK_INTERRUPTIBLE while holding sem_lock().
235  * The wakeup is handled using the wake_q infrastructure. wake_q wakeups may
236  * happen immediately after calling wake_q_add. As wake_q_add_safe() is called
237  * when holding sem_lock(), no further barriers are required.
238  *
239  * See also ipc/mqueue.c for more details on the covered races.
240  */
241 
242 #define sc_semmsl	sem_ctls[0]
243 #define sc_semmns	sem_ctls[1]
244 #define sc_semopm	sem_ctls[2]
245 #define sc_semmni	sem_ctls[3]
246 
sem_init_ns(struct ipc_namespace * ns)247 void sem_init_ns(struct ipc_namespace *ns)
248 {
249 	ns->sc_semmsl = SEMMSL;
250 	ns->sc_semmns = SEMMNS;
251 	ns->sc_semopm = SEMOPM;
252 	ns->sc_semmni = SEMMNI;
253 	ns->used_sems = 0;
254 	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
255 }
256 
257 #ifdef CONFIG_IPC_NS
sem_exit_ns(struct ipc_namespace * ns)258 void sem_exit_ns(struct ipc_namespace *ns)
259 {
260 	free_ipcs(ns, &sem_ids(ns), freeary);
261 	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
262 	rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht);
263 }
264 #endif
265 
sem_init(void)266 void __init sem_init(void)
267 {
268 	sem_init_ns(&init_ipc_ns);
269 	ipc_init_proc_interface("sysvipc/sem",
270 				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
271 				IPC_SEM_IDS, sysvipc_sem_proc_show);
272 }
273 
274 /**
275  * unmerge_queues - unmerge queues, if possible.
276  * @sma: semaphore array
277  *
278  * The function unmerges the wait queues if complex_count is 0.
279  * It must be called prior to dropping the global semaphore array lock.
280  */
unmerge_queues(struct sem_array * sma)281 static void unmerge_queues(struct sem_array *sma)
282 {
283 	struct sem_queue *q, *tq;
284 
285 	/* complex operations still around? */
286 	if (sma->complex_count)
287 		return;
288 	/*
289 	 * We will switch back to simple mode.
290 	 * Move all pending operation back into the per-semaphore
291 	 * queues.
292 	 */
293 	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
294 		struct sem *curr;
295 		curr = &sma->sems[q->sops[0].sem_num];
296 
297 		list_add_tail(&q->list, &curr->pending_alter);
298 	}
299 	INIT_LIST_HEAD(&sma->pending_alter);
300 }
301 
302 /**
303  * merge_queues - merge single semop queues into global queue
304  * @sma: semaphore array
305  *
306  * This function merges all per-semaphore queues into the global queue.
307  * It is necessary to achieve FIFO ordering for the pending single-sop
308  * operations when a multi-semop operation must sleep.
309  * Only the alter operations must be moved, the const operations can stay.
310  */
merge_queues(struct sem_array * sma)311 static void merge_queues(struct sem_array *sma)
312 {
313 	int i;
314 	for (i = 0; i < sma->sem_nsems; i++) {
315 		struct sem *sem = &sma->sems[i];
316 
317 		list_splice_init(&sem->pending_alter, &sma->pending_alter);
318 	}
319 }
320 
sem_rcu_free(struct rcu_head * head)321 static void sem_rcu_free(struct rcu_head *head)
322 {
323 	struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
324 	struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
325 
326 	security_sem_free(&sma->sem_perm);
327 	kvfree(sma);
328 }
329 
330 /*
331  * Enter the mode suitable for non-simple operations:
332  * Caller must own sem_perm.lock.
333  */
complexmode_enter(struct sem_array * sma)334 static void complexmode_enter(struct sem_array *sma)
335 {
336 	int i;
337 	struct sem *sem;
338 
339 	if (sma->use_global_lock > 0)  {
340 		/*
341 		 * We are already in global lock mode.
342 		 * Nothing to do, just reset the
343 		 * counter until we return to simple mode.
344 		 */
345 		sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
346 		return;
347 	}
348 	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
349 
350 	for (i = 0; i < sma->sem_nsems; i++) {
351 		sem = &sma->sems[i];
352 		spin_lock(&sem->lock);
353 		spin_unlock(&sem->lock);
354 	}
355 }
356 
357 /*
358  * Try to leave the mode that disallows simple operations:
359  * Caller must own sem_perm.lock.
360  */
complexmode_tryleave(struct sem_array * sma)361 static void complexmode_tryleave(struct sem_array *sma)
362 {
363 	if (sma->complex_count)  {
364 		/* Complex ops are sleeping.
365 		 * We must stay in complex mode
366 		 */
367 		return;
368 	}
369 	if (sma->use_global_lock == 1) {
370 
371 		/* See SEM_BARRIER_1 for purpose/pairing */
372 		smp_store_release(&sma->use_global_lock, 0);
373 	} else {
374 		sma->use_global_lock--;
375 	}
376 }
377 
378 #define SEM_GLOBAL_LOCK	(-1)
379 /*
380  * If the request contains only one semaphore operation, and there are
381  * no complex transactions pending, lock only the semaphore involved.
382  * Otherwise, lock the entire semaphore array, since we either have
383  * multiple semaphores in our own semops, or we need to look at
384  * semaphores from other pending complex operations.
385  */
sem_lock(struct sem_array * sma,struct sembuf * sops,int nsops)386 static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
387 			      int nsops)
388 {
389 	struct sem *sem;
390 	int idx;
391 
392 	if (nsops != 1) {
393 		/* Complex operation - acquire a full lock */
394 		ipc_lock_object(&sma->sem_perm);
395 
396 		/* Prevent parallel simple ops */
397 		complexmode_enter(sma);
398 		return SEM_GLOBAL_LOCK;
399 	}
400 
401 	/*
402 	 * Only one semaphore affected - try to optimize locking.
403 	 * Optimized locking is possible if no complex operation
404 	 * is either enqueued or processed right now.
405 	 *
406 	 * Both facts are tracked by use_global_mode.
407 	 */
408 	idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
409 	sem = &sma->sems[idx];
410 
411 	/*
412 	 * Initial check for use_global_lock. Just an optimization,
413 	 * no locking, no memory barrier.
414 	 */
415 	if (!sma->use_global_lock) {
416 		/*
417 		 * It appears that no complex operation is around.
418 		 * Acquire the per-semaphore lock.
419 		 */
420 		spin_lock(&sem->lock);
421 
422 		/* see SEM_BARRIER_1 for purpose/pairing */
423 		if (!smp_load_acquire(&sma->use_global_lock)) {
424 			/* fast path successful! */
425 			return sops->sem_num;
426 		}
427 		spin_unlock(&sem->lock);
428 	}
429 
430 	/* slow path: acquire the full lock */
431 	ipc_lock_object(&sma->sem_perm);
432 
433 	if (sma->use_global_lock == 0) {
434 		/*
435 		 * The use_global_lock mode ended while we waited for
436 		 * sma->sem_perm.lock. Thus we must switch to locking
437 		 * with sem->lock.
438 		 * Unlike in the fast path, there is no need to recheck
439 		 * sma->use_global_lock after we have acquired sem->lock:
440 		 * We own sma->sem_perm.lock, thus use_global_lock cannot
441 		 * change.
442 		 */
443 		spin_lock(&sem->lock);
444 
445 		ipc_unlock_object(&sma->sem_perm);
446 		return sops->sem_num;
447 	} else {
448 		/*
449 		 * Not a false alarm, thus continue to use the global lock
450 		 * mode. No need for complexmode_enter(), this was done by
451 		 * the caller that has set use_global_mode to non-zero.
452 		 */
453 		return SEM_GLOBAL_LOCK;
454 	}
455 }
456 
sem_unlock(struct sem_array * sma,int locknum)457 static inline void sem_unlock(struct sem_array *sma, int locknum)
458 {
459 	if (locknum == SEM_GLOBAL_LOCK) {
460 		unmerge_queues(sma);
461 		complexmode_tryleave(sma);
462 		ipc_unlock_object(&sma->sem_perm);
463 	} else {
464 		struct sem *sem = &sma->sems[locknum];
465 		spin_unlock(&sem->lock);
466 	}
467 }
468 
469 /*
470  * sem_lock_(check_) routines are called in the paths where the rwsem
471  * is not held.
472  *
473  * The caller holds the RCU read lock.
474  */
sem_obtain_object(struct ipc_namespace * ns,int id)475 static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
476 {
477 	struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
478 
479 	if (IS_ERR(ipcp))
480 		return ERR_CAST(ipcp);
481 
482 	return container_of(ipcp, struct sem_array, sem_perm);
483 }
484 
sem_obtain_object_check(struct ipc_namespace * ns,int id)485 static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
486 							int id)
487 {
488 	struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
489 
490 	if (IS_ERR(ipcp))
491 		return ERR_CAST(ipcp);
492 
493 	return container_of(ipcp, struct sem_array, sem_perm);
494 }
495 
sem_lock_and_putref(struct sem_array * sma)496 static inline void sem_lock_and_putref(struct sem_array *sma)
497 {
498 	sem_lock(sma, NULL, -1);
499 	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
500 }
501 
sem_rmid(struct ipc_namespace * ns,struct sem_array * s)502 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
503 {
504 	ipc_rmid(&sem_ids(ns), &s->sem_perm);
505 }
506 
sem_alloc(size_t nsems)507 static struct sem_array *sem_alloc(size_t nsems)
508 {
509 	struct sem_array *sma;
510 
511 	if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
512 		return NULL;
513 
514 	sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL);
515 	if (unlikely(!sma))
516 		return NULL;
517 
518 	return sma;
519 }
520 
521 /**
522  * newary - Create a new semaphore set
523  * @ns: namespace
524  * @params: ptr to the structure that contains key, semflg and nsems
525  *
526  * Called with sem_ids.rwsem held (as a writer)
527  */
newary(struct ipc_namespace * ns,struct ipc_params * params)528 static int newary(struct ipc_namespace *ns, struct ipc_params *params)
529 {
530 	int retval;
531 	struct sem_array *sma;
532 	key_t key = params->key;
533 	int nsems = params->u.nsems;
534 	int semflg = params->flg;
535 	int i;
536 
537 	if (!nsems)
538 		return -EINVAL;
539 	if (ns->used_sems + nsems > ns->sc_semmns)
540 		return -ENOSPC;
541 
542 	sma = sem_alloc(nsems);
543 	if (!sma)
544 		return -ENOMEM;
545 
546 	sma->sem_perm.mode = (semflg & S_IRWXUGO);
547 	sma->sem_perm.key = key;
548 
549 	sma->sem_perm.security = NULL;
550 	retval = security_sem_alloc(&sma->sem_perm);
551 	if (retval) {
552 		kvfree(sma);
553 		return retval;
554 	}
555 
556 	for (i = 0; i < nsems; i++) {
557 		INIT_LIST_HEAD(&sma->sems[i].pending_alter);
558 		INIT_LIST_HEAD(&sma->sems[i].pending_const);
559 		spin_lock_init(&sma->sems[i].lock);
560 	}
561 
562 	sma->complex_count = 0;
563 	sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
564 	INIT_LIST_HEAD(&sma->pending_alter);
565 	INIT_LIST_HEAD(&sma->pending_const);
566 	INIT_LIST_HEAD(&sma->list_id);
567 	sma->sem_nsems = nsems;
568 	sma->sem_ctime = ktime_get_real_seconds();
569 
570 	/* ipc_addid() locks sma upon success. */
571 	retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
572 	if (retval < 0) {
573 		ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
574 		return retval;
575 	}
576 	ns->used_sems += nsems;
577 
578 	sem_unlock(sma, -1);
579 	rcu_read_unlock();
580 
581 	return sma->sem_perm.id;
582 }
583 
584 
585 /*
586  * Called with sem_ids.rwsem and ipcp locked.
587  */
sem_more_checks(struct kern_ipc_perm * ipcp,struct ipc_params * params)588 static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params)
589 {
590 	struct sem_array *sma;
591 
592 	sma = container_of(ipcp, struct sem_array, sem_perm);
593 	if (params->u.nsems > sma->sem_nsems)
594 		return -EINVAL;
595 
596 	return 0;
597 }
598 
ksys_semget(key_t key,int nsems,int semflg)599 long ksys_semget(key_t key, int nsems, int semflg)
600 {
601 	struct ipc_namespace *ns;
602 	static const struct ipc_ops sem_ops = {
603 		.getnew = newary,
604 		.associate = security_sem_associate,
605 		.more_checks = sem_more_checks,
606 	};
607 	struct ipc_params sem_params;
608 
609 	ns = current->nsproxy->ipc_ns;
610 
611 	if (nsems < 0 || nsems > ns->sc_semmsl)
612 		return -EINVAL;
613 
614 	sem_params.key = key;
615 	sem_params.flg = semflg;
616 	sem_params.u.nsems = nsems;
617 
618 	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
619 }
620 
SYSCALL_DEFINE3(semget,key_t,key,int,nsems,int,semflg)621 SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
622 {
623 	return ksys_semget(key, nsems, semflg);
624 }
625 
626 /**
627  * perform_atomic_semop[_slow] - Attempt to perform semaphore
628  *                               operations on a given array.
629  * @sma: semaphore array
630  * @q: struct sem_queue that describes the operation
631  *
632  * Caller blocking are as follows, based the value
633  * indicated by the semaphore operation (sem_op):
634  *
635  *  (1) >0 never blocks.
636  *  (2)  0 (wait-for-zero operation): semval is non-zero.
637  *  (3) <0 attempting to decrement semval to a value smaller than zero.
638  *
639  * Returns 0 if the operation was possible.
640  * Returns 1 if the operation is impossible, the caller must sleep.
641  * Returns <0 for error codes.
642  */
perform_atomic_semop_slow(struct sem_array * sma,struct sem_queue * q)643 static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
644 {
645 	int result, sem_op, nsops;
646 	struct pid *pid;
647 	struct sembuf *sop;
648 	struct sem *curr;
649 	struct sembuf *sops;
650 	struct sem_undo *un;
651 
652 	sops = q->sops;
653 	nsops = q->nsops;
654 	un = q->undo;
655 
656 	for (sop = sops; sop < sops + nsops; sop++) {
657 		int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
658 		curr = &sma->sems[idx];
659 		sem_op = sop->sem_op;
660 		result = curr->semval;
661 
662 		if (!sem_op && result)
663 			goto would_block;
664 
665 		result += sem_op;
666 		if (result < 0)
667 			goto would_block;
668 		if (result > SEMVMX)
669 			goto out_of_range;
670 
671 		if (sop->sem_flg & SEM_UNDO) {
672 			int undo = un->semadj[sop->sem_num] - sem_op;
673 			/* Exceeding the undo range is an error. */
674 			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
675 				goto out_of_range;
676 			un->semadj[sop->sem_num] = undo;
677 		}
678 
679 		curr->semval = result;
680 	}
681 
682 	sop--;
683 	pid = q->pid;
684 	while (sop >= sops) {
685 		ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid);
686 		sop--;
687 	}
688 
689 	return 0;
690 
691 out_of_range:
692 	result = -ERANGE;
693 	goto undo;
694 
695 would_block:
696 	q->blocking = sop;
697 
698 	if (sop->sem_flg & IPC_NOWAIT)
699 		result = -EAGAIN;
700 	else
701 		result = 1;
702 
703 undo:
704 	sop--;
705 	while (sop >= sops) {
706 		sem_op = sop->sem_op;
707 		sma->sems[sop->sem_num].semval -= sem_op;
708 		if (sop->sem_flg & SEM_UNDO)
709 			un->semadj[sop->sem_num] += sem_op;
710 		sop--;
711 	}
712 
713 	return result;
714 }
715 
perform_atomic_semop(struct sem_array * sma,struct sem_queue * q)716 static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
717 {
718 	int result, sem_op, nsops;
719 	struct sembuf *sop;
720 	struct sem *curr;
721 	struct sembuf *sops;
722 	struct sem_undo *un;
723 
724 	sops = q->sops;
725 	nsops = q->nsops;
726 	un = q->undo;
727 
728 	if (unlikely(q->dupsop))
729 		return perform_atomic_semop_slow(sma, q);
730 
731 	/*
732 	 * We scan the semaphore set twice, first to ensure that the entire
733 	 * operation can succeed, therefore avoiding any pointless writes
734 	 * to shared memory and having to undo such changes in order to block
735 	 * until the operations can go through.
736 	 */
737 	for (sop = sops; sop < sops + nsops; sop++) {
738 		int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
739 
740 		curr = &sma->sems[idx];
741 		sem_op = sop->sem_op;
742 		result = curr->semval;
743 
744 		if (!sem_op && result)
745 			goto would_block; /* wait-for-zero */
746 
747 		result += sem_op;
748 		if (result < 0)
749 			goto would_block;
750 
751 		if (result > SEMVMX)
752 			return -ERANGE;
753 
754 		if (sop->sem_flg & SEM_UNDO) {
755 			int undo = un->semadj[sop->sem_num] - sem_op;
756 
757 			/* Exceeding the undo range is an error. */
758 			if (undo < (-SEMAEM - 1) || undo > SEMAEM)
759 				return -ERANGE;
760 		}
761 	}
762 
763 	for (sop = sops; sop < sops + nsops; sop++) {
764 		curr = &sma->sems[sop->sem_num];
765 		sem_op = sop->sem_op;
766 		result = curr->semval;
767 
768 		if (sop->sem_flg & SEM_UNDO) {
769 			int undo = un->semadj[sop->sem_num] - sem_op;
770 
771 			un->semadj[sop->sem_num] = undo;
772 		}
773 		curr->semval += sem_op;
774 		ipc_update_pid(&curr->sempid, q->pid);
775 	}
776 
777 	return 0;
778 
779 would_block:
780 	q->blocking = sop;
781 	return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
782 }
783 
wake_up_sem_queue_prepare(struct sem_queue * q,int error,struct wake_q_head * wake_q)784 static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
785 					     struct wake_q_head *wake_q)
786 {
787 	get_task_struct(q->sleeper);
788 
789 	/* see SEM_BARRIER_2 for purpuse/pairing */
790 	smp_store_release(&q->status, error);
791 
792 	wake_q_add_safe(wake_q, q->sleeper);
793 }
794 
unlink_queue(struct sem_array * sma,struct sem_queue * q)795 static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
796 {
797 	list_del(&q->list);
798 	if (q->nsops > 1)
799 		sma->complex_count--;
800 }
801 
802 /** check_restart(sma, q)
803  * @sma: semaphore array
804  * @q: the operation that just completed
805  *
806  * update_queue is O(N^2) when it restarts scanning the whole queue of
807  * waiting operations. Therefore this function checks if the restart is
808  * really necessary. It is called after a previously waiting operation
809  * modified the array.
810  * Note that wait-for-zero operations are handled without restart.
811  */
check_restart(struct sem_array * sma,struct sem_queue * q)812 static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
813 {
814 	/* pending complex alter operations are too difficult to analyse */
815 	if (!list_empty(&sma->pending_alter))
816 		return 1;
817 
818 	/* we were a sleeping complex operation. Too difficult */
819 	if (q->nsops > 1)
820 		return 1;
821 
822 	/* It is impossible that someone waits for the new value:
823 	 * - complex operations always restart.
824 	 * - wait-for-zero are handled seperately.
825 	 * - q is a previously sleeping simple operation that
826 	 *   altered the array. It must be a decrement, because
827 	 *   simple increments never sleep.
828 	 * - If there are older (higher priority) decrements
829 	 *   in the queue, then they have observed the original
830 	 *   semval value and couldn't proceed. The operation
831 	 *   decremented to value - thus they won't proceed either.
832 	 */
833 	return 0;
834 }
835 
836 /**
837  * wake_const_ops - wake up non-alter tasks
838  * @sma: semaphore array.
839  * @semnum: semaphore that was modified.
840  * @wake_q: lockless wake-queue head.
841  *
842  * wake_const_ops must be called after a semaphore in a semaphore array
843  * was set to 0. If complex const operations are pending, wake_const_ops must
844  * be called with semnum = -1, as well as with the number of each modified
845  * semaphore.
846  * The tasks that must be woken up are added to @wake_q. The return code
847  * is stored in q->pid.
848  * The function returns 1 if at least one operation was completed successfully.
849  */
wake_const_ops(struct sem_array * sma,int semnum,struct wake_q_head * wake_q)850 static int wake_const_ops(struct sem_array *sma, int semnum,
851 			  struct wake_q_head *wake_q)
852 {
853 	struct sem_queue *q, *tmp;
854 	struct list_head *pending_list;
855 	int semop_completed = 0;
856 
857 	if (semnum == -1)
858 		pending_list = &sma->pending_const;
859 	else
860 		pending_list = &sma->sems[semnum].pending_const;
861 
862 	list_for_each_entry_safe(q, tmp, pending_list, list) {
863 		int error = perform_atomic_semop(sma, q);
864 
865 		if (error > 0)
866 			continue;
867 		/* operation completed, remove from queue & wakeup */
868 		unlink_queue(sma, q);
869 
870 		wake_up_sem_queue_prepare(q, error, wake_q);
871 		if (error == 0)
872 			semop_completed = 1;
873 	}
874 
875 	return semop_completed;
876 }
877 
878 /**
879  * do_smart_wakeup_zero - wakeup all wait for zero tasks
880  * @sma: semaphore array
881  * @sops: operations that were performed
882  * @nsops: number of operations
883  * @wake_q: lockless wake-queue head
884  *
885  * Checks all required queue for wait-for-zero operations, based
886  * on the actual changes that were performed on the semaphore array.
887  * The function returns 1 if at least one operation was completed successfully.
888  */
do_smart_wakeup_zero(struct sem_array * sma,struct sembuf * sops,int nsops,struct wake_q_head * wake_q)889 static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
890 				int nsops, struct wake_q_head *wake_q)
891 {
892 	int i;
893 	int semop_completed = 0;
894 	int got_zero = 0;
895 
896 	/* first: the per-semaphore queues, if known */
897 	if (sops) {
898 		for (i = 0; i < nsops; i++) {
899 			int num = sops[i].sem_num;
900 
901 			if (sma->sems[num].semval == 0) {
902 				got_zero = 1;
903 				semop_completed |= wake_const_ops(sma, num, wake_q);
904 			}
905 		}
906 	} else {
907 		/*
908 		 * No sops means modified semaphores not known.
909 		 * Assume all were changed.
910 		 */
911 		for (i = 0; i < sma->sem_nsems; i++) {
912 			if (sma->sems[i].semval == 0) {
913 				got_zero = 1;
914 				semop_completed |= wake_const_ops(sma, i, wake_q);
915 			}
916 		}
917 	}
918 	/*
919 	 * If one of the modified semaphores got 0,
920 	 * then check the global queue, too.
921 	 */
922 	if (got_zero)
923 		semop_completed |= wake_const_ops(sma, -1, wake_q);
924 
925 	return semop_completed;
926 }
927 
928 
929 /**
930  * update_queue - look for tasks that can be completed.
931  * @sma: semaphore array.
932  * @semnum: semaphore that was modified.
933  * @wake_q: lockless wake-queue head.
934  *
935  * update_queue must be called after a semaphore in a semaphore array
936  * was modified. If multiple semaphores were modified, update_queue must
937  * be called with semnum = -1, as well as with the number of each modified
938  * semaphore.
939  * The tasks that must be woken up are added to @wake_q. The return code
940  * is stored in q->pid.
941  * The function internally checks if const operations can now succeed.
942  *
943  * The function return 1 if at least one semop was completed successfully.
944  */
update_queue(struct sem_array * sma,int semnum,struct wake_q_head * wake_q)945 static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
946 {
947 	struct sem_queue *q, *tmp;
948 	struct list_head *pending_list;
949 	int semop_completed = 0;
950 
951 	if (semnum == -1)
952 		pending_list = &sma->pending_alter;
953 	else
954 		pending_list = &sma->sems[semnum].pending_alter;
955 
956 again:
957 	list_for_each_entry_safe(q, tmp, pending_list, list) {
958 		int error, restart;
959 
960 		/* If we are scanning the single sop, per-semaphore list of
961 		 * one semaphore and that semaphore is 0, then it is not
962 		 * necessary to scan further: simple increments
963 		 * that affect only one entry succeed immediately and cannot
964 		 * be in the  per semaphore pending queue, and decrements
965 		 * cannot be successful if the value is already 0.
966 		 */
967 		if (semnum != -1 && sma->sems[semnum].semval == 0)
968 			break;
969 
970 		error = perform_atomic_semop(sma, q);
971 
972 		/* Does q->sleeper still need to sleep? */
973 		if (error > 0)
974 			continue;
975 
976 		unlink_queue(sma, q);
977 
978 		if (error) {
979 			restart = 0;
980 		} else {
981 			semop_completed = 1;
982 			do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
983 			restart = check_restart(sma, q);
984 		}
985 
986 		wake_up_sem_queue_prepare(q, error, wake_q);
987 		if (restart)
988 			goto again;
989 	}
990 	return semop_completed;
991 }
992 
993 /**
994  * set_semotime - set sem_otime
995  * @sma: semaphore array
996  * @sops: operations that modified the array, may be NULL
997  *
998  * sem_otime is replicated to avoid cache line trashing.
999  * This function sets one instance to the current time.
1000  */
set_semotime(struct sem_array * sma,struct sembuf * sops)1001 static void set_semotime(struct sem_array *sma, struct sembuf *sops)
1002 {
1003 	if (sops == NULL) {
1004 		sma->sems[0].sem_otime = ktime_get_real_seconds();
1005 	} else {
1006 		sma->sems[sops[0].sem_num].sem_otime =
1007 						ktime_get_real_seconds();
1008 	}
1009 }
1010 
1011 /**
1012  * do_smart_update - optimized update_queue
1013  * @sma: semaphore array
1014  * @sops: operations that were performed
1015  * @nsops: number of operations
1016  * @otime: force setting otime
1017  * @wake_q: lockless wake-queue head
1018  *
1019  * do_smart_update() does the required calls to update_queue and wakeup_zero,
1020  * based on the actual changes that were performed on the semaphore array.
1021  * Note that the function does not do the actual wake-up: the caller is
1022  * responsible for calling wake_up_q().
1023  * It is safe to perform this call after dropping all locks.
1024  */
do_smart_update(struct sem_array * sma,struct sembuf * sops,int nsops,int otime,struct wake_q_head * wake_q)1025 static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
1026 			    int otime, struct wake_q_head *wake_q)
1027 {
1028 	int i;
1029 
1030 	otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
1031 
1032 	if (!list_empty(&sma->pending_alter)) {
1033 		/* semaphore array uses the global queue - just process it. */
1034 		otime |= update_queue(sma, -1, wake_q);
1035 	} else {
1036 		if (!sops) {
1037 			/*
1038 			 * No sops, thus the modified semaphores are not
1039 			 * known. Check all.
1040 			 */
1041 			for (i = 0; i < sma->sem_nsems; i++)
1042 				otime |= update_queue(sma, i, wake_q);
1043 		} else {
1044 			/*
1045 			 * Check the semaphores that were increased:
1046 			 * - No complex ops, thus all sleeping ops are
1047 			 *   decrease.
1048 			 * - if we decreased the value, then any sleeping
1049 			 *   semaphore ops wont be able to run: If the
1050 			 *   previous value was too small, then the new
1051 			 *   value will be too small, too.
1052 			 */
1053 			for (i = 0; i < nsops; i++) {
1054 				if (sops[i].sem_op > 0) {
1055 					otime |= update_queue(sma,
1056 							      sops[i].sem_num, wake_q);
1057 				}
1058 			}
1059 		}
1060 	}
1061 	if (otime)
1062 		set_semotime(sma, sops);
1063 }
1064 
1065 /*
1066  * check_qop: Test if a queued operation sleeps on the semaphore semnum
1067  */
check_qop(struct sem_array * sma,int semnum,struct sem_queue * q,bool count_zero)1068 static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1069 			bool count_zero)
1070 {
1071 	struct sembuf *sop = q->blocking;
1072 
1073 	/*
1074 	 * Linux always (since 0.99.10) reported a task as sleeping on all
1075 	 * semaphores. This violates SUS, therefore it was changed to the
1076 	 * standard compliant behavior.
1077 	 * Give the administrators a chance to notice that an application
1078 	 * might misbehave because it relies on the Linux behavior.
1079 	 */
1080 	pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1081 			"The task %s (%d) triggered the difference, watch for misbehavior.\n",
1082 			current->comm, task_pid_nr(current));
1083 
1084 	if (sop->sem_num != semnum)
1085 		return 0;
1086 
1087 	if (count_zero && sop->sem_op == 0)
1088 		return 1;
1089 	if (!count_zero && sop->sem_op < 0)
1090 		return 1;
1091 
1092 	return 0;
1093 }
1094 
1095 /* The following counts are associated to each semaphore:
1096  *   semncnt        number of tasks waiting on semval being nonzero
1097  *   semzcnt        number of tasks waiting on semval being zero
1098  *
1099  * Per definition, a task waits only on the semaphore of the first semop
1100  * that cannot proceed, even if additional operation would block, too.
1101  */
count_semcnt(struct sem_array * sma,ushort semnum,bool count_zero)1102 static int count_semcnt(struct sem_array *sma, ushort semnum,
1103 			bool count_zero)
1104 {
1105 	struct list_head *l;
1106 	struct sem_queue *q;
1107 	int semcnt;
1108 
1109 	semcnt = 0;
1110 	/* First: check the simple operations. They are easy to evaluate */
1111 	if (count_zero)
1112 		l = &sma->sems[semnum].pending_const;
1113 	else
1114 		l = &sma->sems[semnum].pending_alter;
1115 
1116 	list_for_each_entry(q, l, list) {
1117 		/* all task on a per-semaphore list sleep on exactly
1118 		 * that semaphore
1119 		 */
1120 		semcnt++;
1121 	}
1122 
1123 	/* Then: check the complex operations. */
1124 	list_for_each_entry(q, &sma->pending_alter, list) {
1125 		semcnt += check_qop(sma, semnum, q, count_zero);
1126 	}
1127 	if (count_zero) {
1128 		list_for_each_entry(q, &sma->pending_const, list) {
1129 			semcnt += check_qop(sma, semnum, q, count_zero);
1130 		}
1131 	}
1132 	return semcnt;
1133 }
1134 
1135 /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1136  * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1137  * remains locked on exit.
1138  */
freeary(struct ipc_namespace * ns,struct kern_ipc_perm * ipcp)1139 static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1140 {
1141 	struct sem_undo *un, *tu;
1142 	struct sem_queue *q, *tq;
1143 	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1144 	int i;
1145 	DEFINE_WAKE_Q(wake_q);
1146 
1147 	/* Free the existing undo structures for this semaphore set.  */
1148 	ipc_assert_locked_object(&sma->sem_perm);
1149 	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1150 		list_del(&un->list_id);
1151 		spin_lock(&un->ulp->lock);
1152 		un->semid = -1;
1153 		list_del_rcu(&un->list_proc);
1154 		spin_unlock(&un->ulp->lock);
1155 		kfree_rcu(un, rcu);
1156 	}
1157 
1158 	/* Wake up all pending processes and let them fail with EIDRM. */
1159 	list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1160 		unlink_queue(sma, q);
1161 		wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1162 	}
1163 
1164 	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1165 		unlink_queue(sma, q);
1166 		wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1167 	}
1168 	for (i = 0; i < sma->sem_nsems; i++) {
1169 		struct sem *sem = &sma->sems[i];
1170 		list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1171 			unlink_queue(sma, q);
1172 			wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1173 		}
1174 		list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1175 			unlink_queue(sma, q);
1176 			wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1177 		}
1178 		ipc_update_pid(&sem->sempid, NULL);
1179 	}
1180 
1181 	/* Remove the semaphore set from the IDR */
1182 	sem_rmid(ns, sma);
1183 	sem_unlock(sma, -1);
1184 	rcu_read_unlock();
1185 
1186 	wake_up_q(&wake_q);
1187 	ns->used_sems -= sma->sem_nsems;
1188 	ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1189 }
1190 
copy_semid_to_user(void __user * buf,struct semid64_ds * in,int version)1191 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1192 {
1193 	switch (version) {
1194 	case IPC_64:
1195 		return copy_to_user(buf, in, sizeof(*in));
1196 	case IPC_OLD:
1197 	    {
1198 		struct semid_ds out;
1199 
1200 		memset(&out, 0, sizeof(out));
1201 
1202 		ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1203 
1204 		out.sem_otime	= in->sem_otime;
1205 		out.sem_ctime	= in->sem_ctime;
1206 		out.sem_nsems	= in->sem_nsems;
1207 
1208 		return copy_to_user(buf, &out, sizeof(out));
1209 	    }
1210 	default:
1211 		return -EINVAL;
1212 	}
1213 }
1214 
get_semotime(struct sem_array * sma)1215 static time64_t get_semotime(struct sem_array *sma)
1216 {
1217 	int i;
1218 	time64_t res;
1219 
1220 	res = sma->sems[0].sem_otime;
1221 	for (i = 1; i < sma->sem_nsems; i++) {
1222 		time64_t to = sma->sems[i].sem_otime;
1223 
1224 		if (to > res)
1225 			res = to;
1226 	}
1227 	return res;
1228 }
1229 
semctl_stat(struct ipc_namespace * ns,int semid,int cmd,struct semid64_ds * semid64)1230 static int semctl_stat(struct ipc_namespace *ns, int semid,
1231 			 int cmd, struct semid64_ds *semid64)
1232 {
1233 	struct sem_array *sma;
1234 	time64_t semotime;
1235 	int err;
1236 
1237 	memset(semid64, 0, sizeof(*semid64));
1238 
1239 	rcu_read_lock();
1240 	if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) {
1241 		sma = sem_obtain_object(ns, semid);
1242 		if (IS_ERR(sma)) {
1243 			err = PTR_ERR(sma);
1244 			goto out_unlock;
1245 		}
1246 	} else { /* IPC_STAT */
1247 		sma = sem_obtain_object_check(ns, semid);
1248 		if (IS_ERR(sma)) {
1249 			err = PTR_ERR(sma);
1250 			goto out_unlock;
1251 		}
1252 	}
1253 
1254 	/* see comment for SHM_STAT_ANY */
1255 	if (cmd == SEM_STAT_ANY)
1256 		audit_ipc_obj(&sma->sem_perm);
1257 	else {
1258 		err = -EACCES;
1259 		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1260 			goto out_unlock;
1261 	}
1262 
1263 	err = security_sem_semctl(&sma->sem_perm, cmd);
1264 	if (err)
1265 		goto out_unlock;
1266 
1267 	ipc_lock_object(&sma->sem_perm);
1268 
1269 	if (!ipc_valid_object(&sma->sem_perm)) {
1270 		ipc_unlock_object(&sma->sem_perm);
1271 		err = -EIDRM;
1272 		goto out_unlock;
1273 	}
1274 
1275 	kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
1276 	semotime = get_semotime(sma);
1277 	semid64->sem_otime = semotime;
1278 	semid64->sem_ctime = sma->sem_ctime;
1279 #ifndef CONFIG_64BIT
1280 	semid64->sem_otime_high = semotime >> 32;
1281 	semid64->sem_ctime_high = sma->sem_ctime >> 32;
1282 #endif
1283 	semid64->sem_nsems = sma->sem_nsems;
1284 
1285 	if (cmd == IPC_STAT) {
1286 		/*
1287 		 * As defined in SUS:
1288 		 * Return 0 on success
1289 		 */
1290 		err = 0;
1291 	} else {
1292 		/*
1293 		 * SEM_STAT and SEM_STAT_ANY (both Linux specific)
1294 		 * Return the full id, including the sequence number
1295 		 */
1296 		err = sma->sem_perm.id;
1297 	}
1298 	ipc_unlock_object(&sma->sem_perm);
1299 out_unlock:
1300 	rcu_read_unlock();
1301 	return err;
1302 }
1303 
semctl_info(struct ipc_namespace * ns,int semid,int cmd,void __user * p)1304 static int semctl_info(struct ipc_namespace *ns, int semid,
1305 			 int cmd, void __user *p)
1306 {
1307 	struct seminfo seminfo;
1308 	int max_idx;
1309 	int err;
1310 
1311 	err = security_sem_semctl(NULL, cmd);
1312 	if (err)
1313 		return err;
1314 
1315 	memset(&seminfo, 0, sizeof(seminfo));
1316 	seminfo.semmni = ns->sc_semmni;
1317 	seminfo.semmns = ns->sc_semmns;
1318 	seminfo.semmsl = ns->sc_semmsl;
1319 	seminfo.semopm = ns->sc_semopm;
1320 	seminfo.semvmx = SEMVMX;
1321 	seminfo.semmnu = SEMMNU;
1322 	seminfo.semmap = SEMMAP;
1323 	seminfo.semume = SEMUME;
1324 	down_read(&sem_ids(ns).rwsem);
1325 	if (cmd == SEM_INFO) {
1326 		seminfo.semusz = sem_ids(ns).in_use;
1327 		seminfo.semaem = ns->used_sems;
1328 	} else {
1329 		seminfo.semusz = SEMUSZ;
1330 		seminfo.semaem = SEMAEM;
1331 	}
1332 	max_idx = ipc_get_maxidx(&sem_ids(ns));
1333 	up_read(&sem_ids(ns).rwsem);
1334 	if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1335 		return -EFAULT;
1336 	return (max_idx < 0) ? 0 : max_idx;
1337 }
1338 
semctl_setval(struct ipc_namespace * ns,int semid,int semnum,int val)1339 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1340 		int val)
1341 {
1342 	struct sem_undo *un;
1343 	struct sem_array *sma;
1344 	struct sem *curr;
1345 	int err;
1346 	DEFINE_WAKE_Q(wake_q);
1347 
1348 	if (val > SEMVMX || val < 0)
1349 		return -ERANGE;
1350 
1351 	rcu_read_lock();
1352 	sma = sem_obtain_object_check(ns, semid);
1353 	if (IS_ERR(sma)) {
1354 		rcu_read_unlock();
1355 		return PTR_ERR(sma);
1356 	}
1357 
1358 	if (semnum < 0 || semnum >= sma->sem_nsems) {
1359 		rcu_read_unlock();
1360 		return -EINVAL;
1361 	}
1362 
1363 
1364 	if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1365 		rcu_read_unlock();
1366 		return -EACCES;
1367 	}
1368 
1369 	err = security_sem_semctl(&sma->sem_perm, SETVAL);
1370 	if (err) {
1371 		rcu_read_unlock();
1372 		return -EACCES;
1373 	}
1374 
1375 	sem_lock(sma, NULL, -1);
1376 
1377 	if (!ipc_valid_object(&sma->sem_perm)) {
1378 		sem_unlock(sma, -1);
1379 		rcu_read_unlock();
1380 		return -EIDRM;
1381 	}
1382 
1383 	semnum = array_index_nospec(semnum, sma->sem_nsems);
1384 	curr = &sma->sems[semnum];
1385 
1386 	ipc_assert_locked_object(&sma->sem_perm);
1387 	list_for_each_entry(un, &sma->list_id, list_id)
1388 		un->semadj[semnum] = 0;
1389 
1390 	curr->semval = val;
1391 	ipc_update_pid(&curr->sempid, task_tgid(current));
1392 	sma->sem_ctime = ktime_get_real_seconds();
1393 	/* maybe some queued-up processes were waiting for this */
1394 	do_smart_update(sma, NULL, 0, 0, &wake_q);
1395 	sem_unlock(sma, -1);
1396 	rcu_read_unlock();
1397 	wake_up_q(&wake_q);
1398 	return 0;
1399 }
1400 
semctl_main(struct ipc_namespace * ns,int semid,int semnum,int cmd,void __user * p)1401 static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1402 		int cmd, void __user *p)
1403 {
1404 	struct sem_array *sma;
1405 	struct sem *curr;
1406 	int err, nsems;
1407 	ushort fast_sem_io[SEMMSL_FAST];
1408 	ushort *sem_io = fast_sem_io;
1409 	DEFINE_WAKE_Q(wake_q);
1410 
1411 	rcu_read_lock();
1412 	sma = sem_obtain_object_check(ns, semid);
1413 	if (IS_ERR(sma)) {
1414 		rcu_read_unlock();
1415 		return PTR_ERR(sma);
1416 	}
1417 
1418 	nsems = sma->sem_nsems;
1419 
1420 	err = -EACCES;
1421 	if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1422 		goto out_rcu_wakeup;
1423 
1424 	err = security_sem_semctl(&sma->sem_perm, cmd);
1425 	if (err)
1426 		goto out_rcu_wakeup;
1427 
1428 	err = -EACCES;
1429 	switch (cmd) {
1430 	case GETALL:
1431 	{
1432 		ushort __user *array = p;
1433 		int i;
1434 
1435 		sem_lock(sma, NULL, -1);
1436 		if (!ipc_valid_object(&sma->sem_perm)) {
1437 			err = -EIDRM;
1438 			goto out_unlock;
1439 		}
1440 		if (nsems > SEMMSL_FAST) {
1441 			if (!ipc_rcu_getref(&sma->sem_perm)) {
1442 				err = -EIDRM;
1443 				goto out_unlock;
1444 			}
1445 			sem_unlock(sma, -1);
1446 			rcu_read_unlock();
1447 			sem_io = kvmalloc_array(nsems, sizeof(ushort),
1448 						GFP_KERNEL);
1449 			if (sem_io == NULL) {
1450 				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1451 				return -ENOMEM;
1452 			}
1453 
1454 			rcu_read_lock();
1455 			sem_lock_and_putref(sma);
1456 			if (!ipc_valid_object(&sma->sem_perm)) {
1457 				err = -EIDRM;
1458 				goto out_unlock;
1459 			}
1460 		}
1461 		for (i = 0; i < sma->sem_nsems; i++)
1462 			sem_io[i] = sma->sems[i].semval;
1463 		sem_unlock(sma, -1);
1464 		rcu_read_unlock();
1465 		err = 0;
1466 		if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1467 			err = -EFAULT;
1468 		goto out_free;
1469 	}
1470 	case SETALL:
1471 	{
1472 		int i;
1473 		struct sem_undo *un;
1474 
1475 		if (!ipc_rcu_getref(&sma->sem_perm)) {
1476 			err = -EIDRM;
1477 			goto out_rcu_wakeup;
1478 		}
1479 		rcu_read_unlock();
1480 
1481 		if (nsems > SEMMSL_FAST) {
1482 			sem_io = kvmalloc_array(nsems, sizeof(ushort),
1483 						GFP_KERNEL);
1484 			if (sem_io == NULL) {
1485 				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1486 				return -ENOMEM;
1487 			}
1488 		}
1489 
1490 		if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1491 			ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1492 			err = -EFAULT;
1493 			goto out_free;
1494 		}
1495 
1496 		for (i = 0; i < nsems; i++) {
1497 			if (sem_io[i] > SEMVMX) {
1498 				ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1499 				err = -ERANGE;
1500 				goto out_free;
1501 			}
1502 		}
1503 		rcu_read_lock();
1504 		sem_lock_and_putref(sma);
1505 		if (!ipc_valid_object(&sma->sem_perm)) {
1506 			err = -EIDRM;
1507 			goto out_unlock;
1508 		}
1509 
1510 		for (i = 0; i < nsems; i++) {
1511 			sma->sems[i].semval = sem_io[i];
1512 			ipc_update_pid(&sma->sems[i].sempid, task_tgid(current));
1513 		}
1514 
1515 		ipc_assert_locked_object(&sma->sem_perm);
1516 		list_for_each_entry(un, &sma->list_id, list_id) {
1517 			for (i = 0; i < nsems; i++)
1518 				un->semadj[i] = 0;
1519 		}
1520 		sma->sem_ctime = ktime_get_real_seconds();
1521 		/* maybe some queued-up processes were waiting for this */
1522 		do_smart_update(sma, NULL, 0, 0, &wake_q);
1523 		err = 0;
1524 		goto out_unlock;
1525 	}
1526 	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1527 	}
1528 	err = -EINVAL;
1529 	if (semnum < 0 || semnum >= nsems)
1530 		goto out_rcu_wakeup;
1531 
1532 	sem_lock(sma, NULL, -1);
1533 	if (!ipc_valid_object(&sma->sem_perm)) {
1534 		err = -EIDRM;
1535 		goto out_unlock;
1536 	}
1537 
1538 	semnum = array_index_nospec(semnum, nsems);
1539 	curr = &sma->sems[semnum];
1540 
1541 	switch (cmd) {
1542 	case GETVAL:
1543 		err = curr->semval;
1544 		goto out_unlock;
1545 	case GETPID:
1546 		err = pid_vnr(curr->sempid);
1547 		goto out_unlock;
1548 	case GETNCNT:
1549 		err = count_semcnt(sma, semnum, 0);
1550 		goto out_unlock;
1551 	case GETZCNT:
1552 		err = count_semcnt(sma, semnum, 1);
1553 		goto out_unlock;
1554 	}
1555 
1556 out_unlock:
1557 	sem_unlock(sma, -1);
1558 out_rcu_wakeup:
1559 	rcu_read_unlock();
1560 	wake_up_q(&wake_q);
1561 out_free:
1562 	if (sem_io != fast_sem_io)
1563 		kvfree(sem_io);
1564 	return err;
1565 }
1566 
1567 static inline unsigned long
copy_semid_from_user(struct semid64_ds * out,void __user * buf,int version)1568 copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1569 {
1570 	switch (version) {
1571 	case IPC_64:
1572 		if (copy_from_user(out, buf, sizeof(*out)))
1573 			return -EFAULT;
1574 		return 0;
1575 	case IPC_OLD:
1576 	    {
1577 		struct semid_ds tbuf_old;
1578 
1579 		if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1580 			return -EFAULT;
1581 
1582 		out->sem_perm.uid	= tbuf_old.sem_perm.uid;
1583 		out->sem_perm.gid	= tbuf_old.sem_perm.gid;
1584 		out->sem_perm.mode	= tbuf_old.sem_perm.mode;
1585 
1586 		return 0;
1587 	    }
1588 	default:
1589 		return -EINVAL;
1590 	}
1591 }
1592 
1593 /*
1594  * This function handles some semctl commands which require the rwsem
1595  * to be held in write mode.
1596  * NOTE: no locks must be held, the rwsem is taken inside this function.
1597  */
semctl_down(struct ipc_namespace * ns,int semid,int cmd,struct semid64_ds * semid64)1598 static int semctl_down(struct ipc_namespace *ns, int semid,
1599 		       int cmd, struct semid64_ds *semid64)
1600 {
1601 	struct sem_array *sma;
1602 	int err;
1603 	struct kern_ipc_perm *ipcp;
1604 
1605 	down_write(&sem_ids(ns).rwsem);
1606 	rcu_read_lock();
1607 
1608 	ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
1609 				      &semid64->sem_perm, 0);
1610 	if (IS_ERR(ipcp)) {
1611 		err = PTR_ERR(ipcp);
1612 		goto out_unlock1;
1613 	}
1614 
1615 	sma = container_of(ipcp, struct sem_array, sem_perm);
1616 
1617 	err = security_sem_semctl(&sma->sem_perm, cmd);
1618 	if (err)
1619 		goto out_unlock1;
1620 
1621 	switch (cmd) {
1622 	case IPC_RMID:
1623 		sem_lock(sma, NULL, -1);
1624 		/* freeary unlocks the ipc object and rcu */
1625 		freeary(ns, ipcp);
1626 		goto out_up;
1627 	case IPC_SET:
1628 		sem_lock(sma, NULL, -1);
1629 		err = ipc_update_perm(&semid64->sem_perm, ipcp);
1630 		if (err)
1631 			goto out_unlock0;
1632 		sma->sem_ctime = ktime_get_real_seconds();
1633 		break;
1634 	default:
1635 		err = -EINVAL;
1636 		goto out_unlock1;
1637 	}
1638 
1639 out_unlock0:
1640 	sem_unlock(sma, -1);
1641 out_unlock1:
1642 	rcu_read_unlock();
1643 out_up:
1644 	up_write(&sem_ids(ns).rwsem);
1645 	return err;
1646 }
1647 
ksys_semctl(int semid,int semnum,int cmd,unsigned long arg,int version)1648 static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version)
1649 {
1650 	struct ipc_namespace *ns;
1651 	void __user *p = (void __user *)arg;
1652 	struct semid64_ds semid64;
1653 	int err;
1654 
1655 	if (semid < 0)
1656 		return -EINVAL;
1657 
1658 	ns = current->nsproxy->ipc_ns;
1659 
1660 	switch (cmd) {
1661 	case IPC_INFO:
1662 	case SEM_INFO:
1663 		return semctl_info(ns, semid, cmd, p);
1664 	case IPC_STAT:
1665 	case SEM_STAT:
1666 	case SEM_STAT_ANY:
1667 		err = semctl_stat(ns, semid, cmd, &semid64);
1668 		if (err < 0)
1669 			return err;
1670 		if (copy_semid_to_user(p, &semid64, version))
1671 			err = -EFAULT;
1672 		return err;
1673 	case GETALL:
1674 	case GETVAL:
1675 	case GETPID:
1676 	case GETNCNT:
1677 	case GETZCNT:
1678 	case SETALL:
1679 		return semctl_main(ns, semid, semnum, cmd, p);
1680 	case SETVAL: {
1681 		int val;
1682 #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1683 		/* big-endian 64bit */
1684 		val = arg >> 32;
1685 #else
1686 		/* 32bit or little-endian 64bit */
1687 		val = arg;
1688 #endif
1689 		return semctl_setval(ns, semid, semnum, val);
1690 	}
1691 	case IPC_SET:
1692 		if (copy_semid_from_user(&semid64, p, version))
1693 			return -EFAULT;
1694 		fallthrough;
1695 	case IPC_RMID:
1696 		return semctl_down(ns, semid, cmd, &semid64);
1697 	default:
1698 		return -EINVAL;
1699 	}
1700 }
1701 
SYSCALL_DEFINE4(semctl,int,semid,int,semnum,int,cmd,unsigned long,arg)1702 SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1703 {
1704 	return ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1705 }
1706 
1707 #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
ksys_old_semctl(int semid,int semnum,int cmd,unsigned long arg)1708 long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg)
1709 {
1710 	int version = ipc_parse_version(&cmd);
1711 
1712 	return ksys_semctl(semid, semnum, cmd, arg, version);
1713 }
1714 
SYSCALL_DEFINE4(old_semctl,int,semid,int,semnum,int,cmd,unsigned long,arg)1715 SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1716 {
1717 	return ksys_old_semctl(semid, semnum, cmd, arg);
1718 }
1719 #endif
1720 
1721 #ifdef CONFIG_COMPAT
1722 
1723 struct compat_semid_ds {
1724 	struct compat_ipc_perm sem_perm;
1725 	old_time32_t sem_otime;
1726 	old_time32_t sem_ctime;
1727 	compat_uptr_t sem_base;
1728 	compat_uptr_t sem_pending;
1729 	compat_uptr_t sem_pending_last;
1730 	compat_uptr_t undo;
1731 	unsigned short sem_nsems;
1732 };
1733 
copy_compat_semid_from_user(struct semid64_ds * out,void __user * buf,int version)1734 static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf,
1735 					int version)
1736 {
1737 	memset(out, 0, sizeof(*out));
1738 	if (version == IPC_64) {
1739 		struct compat_semid64_ds __user *p = buf;
1740 		return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm);
1741 	} else {
1742 		struct compat_semid_ds __user *p = buf;
1743 		return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm);
1744 	}
1745 }
1746 
copy_compat_semid_to_user(void __user * buf,struct semid64_ds * in,int version)1747 static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in,
1748 					int version)
1749 {
1750 	if (version == IPC_64) {
1751 		struct compat_semid64_ds v;
1752 		memset(&v, 0, sizeof(v));
1753 		to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm);
1754 		v.sem_otime	 = lower_32_bits(in->sem_otime);
1755 		v.sem_otime_high = upper_32_bits(in->sem_otime);
1756 		v.sem_ctime	 = lower_32_bits(in->sem_ctime);
1757 		v.sem_ctime_high = upper_32_bits(in->sem_ctime);
1758 		v.sem_nsems = in->sem_nsems;
1759 		return copy_to_user(buf, &v, sizeof(v));
1760 	} else {
1761 		struct compat_semid_ds v;
1762 		memset(&v, 0, sizeof(v));
1763 		to_compat_ipc_perm(&v.sem_perm, &in->sem_perm);
1764 		v.sem_otime = in->sem_otime;
1765 		v.sem_ctime = in->sem_ctime;
1766 		v.sem_nsems = in->sem_nsems;
1767 		return copy_to_user(buf, &v, sizeof(v));
1768 	}
1769 }
1770 
compat_ksys_semctl(int semid,int semnum,int cmd,int arg,int version)1771 static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version)
1772 {
1773 	void __user *p = compat_ptr(arg);
1774 	struct ipc_namespace *ns;
1775 	struct semid64_ds semid64;
1776 	int err;
1777 
1778 	ns = current->nsproxy->ipc_ns;
1779 
1780 	if (semid < 0)
1781 		return -EINVAL;
1782 
1783 	switch (cmd & (~IPC_64)) {
1784 	case IPC_INFO:
1785 	case SEM_INFO:
1786 		return semctl_info(ns, semid, cmd, p);
1787 	case IPC_STAT:
1788 	case SEM_STAT:
1789 	case SEM_STAT_ANY:
1790 		err = semctl_stat(ns, semid, cmd, &semid64);
1791 		if (err < 0)
1792 			return err;
1793 		if (copy_compat_semid_to_user(p, &semid64, version))
1794 			err = -EFAULT;
1795 		return err;
1796 	case GETVAL:
1797 	case GETPID:
1798 	case GETNCNT:
1799 	case GETZCNT:
1800 	case GETALL:
1801 	case SETALL:
1802 		return semctl_main(ns, semid, semnum, cmd, p);
1803 	case SETVAL:
1804 		return semctl_setval(ns, semid, semnum, arg);
1805 	case IPC_SET:
1806 		if (copy_compat_semid_from_user(&semid64, p, version))
1807 			return -EFAULT;
1808 		fallthrough;
1809 	case IPC_RMID:
1810 		return semctl_down(ns, semid, cmd, &semid64);
1811 	default:
1812 		return -EINVAL;
1813 	}
1814 }
1815 
COMPAT_SYSCALL_DEFINE4(semctl,int,semid,int,semnum,int,cmd,int,arg)1816 COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
1817 {
1818 	return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1819 }
1820 
1821 #ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
compat_ksys_old_semctl(int semid,int semnum,int cmd,int arg)1822 long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg)
1823 {
1824 	int version = compat_ipc_parse_version(&cmd);
1825 
1826 	return compat_ksys_semctl(semid, semnum, cmd, arg, version);
1827 }
1828 
COMPAT_SYSCALL_DEFINE4(old_semctl,int,semid,int,semnum,int,cmd,int,arg)1829 COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg)
1830 {
1831 	return compat_ksys_old_semctl(semid, semnum, cmd, arg);
1832 }
1833 #endif
1834 #endif
1835 
1836 /* If the task doesn't already have a undo_list, then allocate one
1837  * here.  We guarantee there is only one thread using this undo list,
1838  * and current is THE ONE
1839  *
1840  * If this allocation and assignment succeeds, but later
1841  * portions of this code fail, there is no need to free the sem_undo_list.
1842  * Just let it stay associated with the task, and it'll be freed later
1843  * at exit time.
1844  *
1845  * This can block, so callers must hold no locks.
1846  */
get_undo_list(struct sem_undo_list ** undo_listp)1847 static inline int get_undo_list(struct sem_undo_list **undo_listp)
1848 {
1849 	struct sem_undo_list *undo_list;
1850 
1851 	undo_list = current->sysvsem.undo_list;
1852 	if (!undo_list) {
1853 		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1854 		if (undo_list == NULL)
1855 			return -ENOMEM;
1856 		spin_lock_init(&undo_list->lock);
1857 		refcount_set(&undo_list->refcnt, 1);
1858 		INIT_LIST_HEAD(&undo_list->list_proc);
1859 
1860 		current->sysvsem.undo_list = undo_list;
1861 	}
1862 	*undo_listp = undo_list;
1863 	return 0;
1864 }
1865 
__lookup_undo(struct sem_undo_list * ulp,int semid)1866 static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1867 {
1868 	struct sem_undo *un;
1869 
1870 	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc,
1871 				spin_is_locked(&ulp->lock)) {
1872 		if (un->semid == semid)
1873 			return un;
1874 	}
1875 	return NULL;
1876 }
1877 
lookup_undo(struct sem_undo_list * ulp,int semid)1878 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1879 {
1880 	struct sem_undo *un;
1881 
1882 	assert_spin_locked(&ulp->lock);
1883 
1884 	un = __lookup_undo(ulp, semid);
1885 	if (un) {
1886 		list_del_rcu(&un->list_proc);
1887 		list_add_rcu(&un->list_proc, &ulp->list_proc);
1888 	}
1889 	return un;
1890 }
1891 
1892 /**
1893  * find_alloc_undo - lookup (and if not present create) undo array
1894  * @ns: namespace
1895  * @semid: semaphore array id
1896  *
1897  * The function looks up (and if not present creates) the undo structure.
1898  * The size of the undo structure depends on the size of the semaphore
1899  * array, thus the alloc path is not that straightforward.
1900  * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1901  * performs a rcu_read_lock().
1902  */
find_alloc_undo(struct ipc_namespace * ns,int semid)1903 static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1904 {
1905 	struct sem_array *sma;
1906 	struct sem_undo_list *ulp;
1907 	struct sem_undo *un, *new;
1908 	int nsems, error;
1909 
1910 	error = get_undo_list(&ulp);
1911 	if (error)
1912 		return ERR_PTR(error);
1913 
1914 	rcu_read_lock();
1915 	spin_lock(&ulp->lock);
1916 	un = lookup_undo(ulp, semid);
1917 	spin_unlock(&ulp->lock);
1918 	if (likely(un != NULL))
1919 		goto out;
1920 
1921 	/* no undo structure around - allocate one. */
1922 	/* step 1: figure out the size of the semaphore array */
1923 	sma = sem_obtain_object_check(ns, semid);
1924 	if (IS_ERR(sma)) {
1925 		rcu_read_unlock();
1926 		return ERR_CAST(sma);
1927 	}
1928 
1929 	nsems = sma->sem_nsems;
1930 	if (!ipc_rcu_getref(&sma->sem_perm)) {
1931 		rcu_read_unlock();
1932 		un = ERR_PTR(-EIDRM);
1933 		goto out;
1934 	}
1935 	rcu_read_unlock();
1936 
1937 	/* step 2: allocate new undo structure */
1938 	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1939 	if (!new) {
1940 		ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1941 		return ERR_PTR(-ENOMEM);
1942 	}
1943 
1944 	/* step 3: Acquire the lock on semaphore array */
1945 	rcu_read_lock();
1946 	sem_lock_and_putref(sma);
1947 	if (!ipc_valid_object(&sma->sem_perm)) {
1948 		sem_unlock(sma, -1);
1949 		rcu_read_unlock();
1950 		kfree(new);
1951 		un = ERR_PTR(-EIDRM);
1952 		goto out;
1953 	}
1954 	spin_lock(&ulp->lock);
1955 
1956 	/*
1957 	 * step 4: check for races: did someone else allocate the undo struct?
1958 	 */
1959 	un = lookup_undo(ulp, semid);
1960 	if (un) {
1961 		kfree(new);
1962 		goto success;
1963 	}
1964 	/* step 5: initialize & link new undo structure */
1965 	new->semadj = (short *) &new[1];
1966 	new->ulp = ulp;
1967 	new->semid = semid;
1968 	assert_spin_locked(&ulp->lock);
1969 	list_add_rcu(&new->list_proc, &ulp->list_proc);
1970 	ipc_assert_locked_object(&sma->sem_perm);
1971 	list_add(&new->list_id, &sma->list_id);
1972 	un = new;
1973 
1974 success:
1975 	spin_unlock(&ulp->lock);
1976 	sem_unlock(sma, -1);
1977 out:
1978 	return un;
1979 }
1980 
do_semtimedop(int semid,struct sembuf __user * tsops,unsigned nsops,const struct timespec64 * timeout)1981 static long do_semtimedop(int semid, struct sembuf __user *tsops,
1982 		unsigned nsops, const struct timespec64 *timeout)
1983 {
1984 	int error = -EINVAL;
1985 	struct sem_array *sma;
1986 	struct sembuf fast_sops[SEMOPM_FAST];
1987 	struct sembuf *sops = fast_sops, *sop;
1988 	struct sem_undo *un;
1989 	int max, locknum;
1990 	bool undos = false, alter = false, dupsop = false;
1991 	struct sem_queue queue;
1992 	unsigned long dup = 0, jiffies_left = 0;
1993 	struct ipc_namespace *ns;
1994 
1995 	ns = current->nsproxy->ipc_ns;
1996 
1997 	if (nsops < 1 || semid < 0)
1998 		return -EINVAL;
1999 	if (nsops > ns->sc_semopm)
2000 		return -E2BIG;
2001 	if (nsops > SEMOPM_FAST) {
2002 		sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
2003 		if (sops == NULL)
2004 			return -ENOMEM;
2005 	}
2006 
2007 	if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
2008 		error =  -EFAULT;
2009 		goto out_free;
2010 	}
2011 
2012 	if (timeout) {
2013 		if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 ||
2014 			timeout->tv_nsec >= 1000000000L) {
2015 			error = -EINVAL;
2016 			goto out_free;
2017 		}
2018 		jiffies_left = timespec64_to_jiffies(timeout);
2019 	}
2020 
2021 	max = 0;
2022 	for (sop = sops; sop < sops + nsops; sop++) {
2023 		unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
2024 
2025 		if (sop->sem_num >= max)
2026 			max = sop->sem_num;
2027 		if (sop->sem_flg & SEM_UNDO)
2028 			undos = true;
2029 		if (dup & mask) {
2030 			/*
2031 			 * There was a previous alter access that appears
2032 			 * to have accessed the same semaphore, thus use
2033 			 * the dupsop logic. "appears", because the detection
2034 			 * can only check % BITS_PER_LONG.
2035 			 */
2036 			dupsop = true;
2037 		}
2038 		if (sop->sem_op != 0) {
2039 			alter = true;
2040 			dup |= mask;
2041 		}
2042 	}
2043 
2044 	if (undos) {
2045 		/* On success, find_alloc_undo takes the rcu_read_lock */
2046 		un = find_alloc_undo(ns, semid);
2047 		if (IS_ERR(un)) {
2048 			error = PTR_ERR(un);
2049 			goto out_free;
2050 		}
2051 	} else {
2052 		un = NULL;
2053 		rcu_read_lock();
2054 	}
2055 
2056 	sma = sem_obtain_object_check(ns, semid);
2057 	if (IS_ERR(sma)) {
2058 		rcu_read_unlock();
2059 		error = PTR_ERR(sma);
2060 		goto out_free;
2061 	}
2062 
2063 	error = -EFBIG;
2064 	if (max >= sma->sem_nsems) {
2065 		rcu_read_unlock();
2066 		goto out_free;
2067 	}
2068 
2069 	error = -EACCES;
2070 	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
2071 		rcu_read_unlock();
2072 		goto out_free;
2073 	}
2074 
2075 	error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
2076 	if (error) {
2077 		rcu_read_unlock();
2078 		goto out_free;
2079 	}
2080 
2081 	error = -EIDRM;
2082 	locknum = sem_lock(sma, sops, nsops);
2083 	/*
2084 	 * We eventually might perform the following check in a lockless
2085 	 * fashion, considering ipc_valid_object() locking constraints.
2086 	 * If nsops == 1 and there is no contention for sem_perm.lock, then
2087 	 * only a per-semaphore lock is held and it's OK to proceed with the
2088 	 * check below. More details on the fine grained locking scheme
2089 	 * entangled here and why it's RMID race safe on comments at sem_lock()
2090 	 */
2091 	if (!ipc_valid_object(&sma->sem_perm))
2092 		goto out_unlock_free;
2093 	/*
2094 	 * semid identifiers are not unique - find_alloc_undo may have
2095 	 * allocated an undo structure, it was invalidated by an RMID
2096 	 * and now a new array with received the same id. Check and fail.
2097 	 * This case can be detected checking un->semid. The existence of
2098 	 * "un" itself is guaranteed by rcu.
2099 	 */
2100 	if (un && un->semid == -1)
2101 		goto out_unlock_free;
2102 
2103 	queue.sops = sops;
2104 	queue.nsops = nsops;
2105 	queue.undo = un;
2106 	queue.pid = task_tgid(current);
2107 	queue.alter = alter;
2108 	queue.dupsop = dupsop;
2109 
2110 	error = perform_atomic_semop(sma, &queue);
2111 	if (error == 0) { /* non-blocking succesfull path */
2112 		DEFINE_WAKE_Q(wake_q);
2113 
2114 		/*
2115 		 * If the operation was successful, then do
2116 		 * the required updates.
2117 		 */
2118 		if (alter)
2119 			do_smart_update(sma, sops, nsops, 1, &wake_q);
2120 		else
2121 			set_semotime(sma, sops);
2122 
2123 		sem_unlock(sma, locknum);
2124 		rcu_read_unlock();
2125 		wake_up_q(&wake_q);
2126 
2127 		goto out_free;
2128 	}
2129 	if (error < 0) /* non-blocking error path */
2130 		goto out_unlock_free;
2131 
2132 	/*
2133 	 * We need to sleep on this operation, so we put the current
2134 	 * task into the pending queue and go to sleep.
2135 	 */
2136 	if (nsops == 1) {
2137 		struct sem *curr;
2138 		int idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
2139 		curr = &sma->sems[idx];
2140 
2141 		if (alter) {
2142 			if (sma->complex_count) {
2143 				list_add_tail(&queue.list,
2144 						&sma->pending_alter);
2145 			} else {
2146 
2147 				list_add_tail(&queue.list,
2148 						&curr->pending_alter);
2149 			}
2150 		} else {
2151 			list_add_tail(&queue.list, &curr->pending_const);
2152 		}
2153 	} else {
2154 		if (!sma->complex_count)
2155 			merge_queues(sma);
2156 
2157 		if (alter)
2158 			list_add_tail(&queue.list, &sma->pending_alter);
2159 		else
2160 			list_add_tail(&queue.list, &sma->pending_const);
2161 
2162 		sma->complex_count++;
2163 	}
2164 
2165 	do {
2166 		/* memory ordering ensured by the lock in sem_lock() */
2167 		WRITE_ONCE(queue.status, -EINTR);
2168 		queue.sleeper = current;
2169 
2170 		/* memory ordering is ensured by the lock in sem_lock() */
2171 		__set_current_state(TASK_INTERRUPTIBLE);
2172 		sem_unlock(sma, locknum);
2173 		rcu_read_unlock();
2174 
2175 		if (timeout)
2176 			jiffies_left = schedule_timeout(jiffies_left);
2177 		else
2178 			schedule();
2179 
2180 		/*
2181 		 * fastpath: the semop has completed, either successfully or
2182 		 * not, from the syscall pov, is quite irrelevant to us at this
2183 		 * point; we're done.
2184 		 *
2185 		 * We _do_ care, nonetheless, about being awoken by a signal or
2186 		 * spuriously.  The queue.status is checked again in the
2187 		 * slowpath (aka after taking sem_lock), such that we can detect
2188 		 * scenarios where we were awakened externally, during the
2189 		 * window between wake_q_add() and wake_up_q().
2190 		 */
2191 		error = READ_ONCE(queue.status);
2192 		if (error != -EINTR) {
2193 			/* see SEM_BARRIER_2 for purpose/pairing */
2194 			smp_acquire__after_ctrl_dep();
2195 			goto out_free;
2196 		}
2197 
2198 		rcu_read_lock();
2199 		locknum = sem_lock(sma, sops, nsops);
2200 
2201 		if (!ipc_valid_object(&sma->sem_perm))
2202 			goto out_unlock_free;
2203 
2204 		/*
2205 		 * No necessity for any barrier: We are protect by sem_lock()
2206 		 */
2207 		error = READ_ONCE(queue.status);
2208 
2209 		/*
2210 		 * If queue.status != -EINTR we are woken up by another process.
2211 		 * Leave without unlink_queue(), but with sem_unlock().
2212 		 */
2213 		if (error != -EINTR)
2214 			goto out_unlock_free;
2215 
2216 		/*
2217 		 * If an interrupt occurred we have to clean up the queue.
2218 		 */
2219 		if (timeout && jiffies_left == 0)
2220 			error = -EAGAIN;
2221 	} while (error == -EINTR && !signal_pending(current)); /* spurious */
2222 
2223 	unlink_queue(sma, &queue);
2224 
2225 out_unlock_free:
2226 	sem_unlock(sma, locknum);
2227 	rcu_read_unlock();
2228 out_free:
2229 	if (sops != fast_sops)
2230 		kvfree(sops);
2231 	return error;
2232 }
2233 
ksys_semtimedop(int semid,struct sembuf __user * tsops,unsigned int nsops,const struct __kernel_timespec __user * timeout)2234 long ksys_semtimedop(int semid, struct sembuf __user *tsops,
2235 		     unsigned int nsops, const struct __kernel_timespec __user *timeout)
2236 {
2237 	if (timeout) {
2238 		struct timespec64 ts;
2239 		if (get_timespec64(&ts, timeout))
2240 			return -EFAULT;
2241 		return do_semtimedop(semid, tsops, nsops, &ts);
2242 	}
2243 	return do_semtimedop(semid, tsops, nsops, NULL);
2244 }
2245 
SYSCALL_DEFINE4(semtimedop,int,semid,struct sembuf __user *,tsops,unsigned int,nsops,const struct __kernel_timespec __user *,timeout)2246 SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
2247 		unsigned int, nsops, const struct __kernel_timespec __user *, timeout)
2248 {
2249 	return ksys_semtimedop(semid, tsops, nsops, timeout);
2250 }
2251 
2252 #ifdef CONFIG_COMPAT_32BIT_TIME
compat_ksys_semtimedop(int semid,struct sembuf __user * tsems,unsigned int nsops,const struct old_timespec32 __user * timeout)2253 long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
2254 			    unsigned int nsops,
2255 			    const struct old_timespec32 __user *timeout)
2256 {
2257 	if (timeout) {
2258 		struct timespec64 ts;
2259 		if (get_old_timespec32(&ts, timeout))
2260 			return -EFAULT;
2261 		return do_semtimedop(semid, tsems, nsops, &ts);
2262 	}
2263 	return do_semtimedop(semid, tsems, nsops, NULL);
2264 }
2265 
SYSCALL_DEFINE4(semtimedop_time32,int,semid,struct sembuf __user *,tsems,unsigned int,nsops,const struct old_timespec32 __user *,timeout)2266 SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems,
2267 		       unsigned int, nsops,
2268 		       const struct old_timespec32 __user *, timeout)
2269 {
2270 	return compat_ksys_semtimedop(semid, tsems, nsops, timeout);
2271 }
2272 #endif
2273 
SYSCALL_DEFINE3(semop,int,semid,struct sembuf __user *,tsops,unsigned,nsops)2274 SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2275 		unsigned, nsops)
2276 {
2277 	return do_semtimedop(semid, tsops, nsops, NULL);
2278 }
2279 
2280 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2281  * parent and child tasks.
2282  */
2283 
copy_semundo(unsigned long clone_flags,struct task_struct * tsk)2284 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2285 {
2286 	struct sem_undo_list *undo_list;
2287 	int error;
2288 
2289 	if (clone_flags & CLONE_SYSVSEM) {
2290 		error = get_undo_list(&undo_list);
2291 		if (error)
2292 			return error;
2293 		refcount_inc(&undo_list->refcnt);
2294 		tsk->sysvsem.undo_list = undo_list;
2295 	} else
2296 		tsk->sysvsem.undo_list = NULL;
2297 
2298 	return 0;
2299 }
2300 
2301 /*
2302  * add semadj values to semaphores, free undo structures.
2303  * undo structures are not freed when semaphore arrays are destroyed
2304  * so some of them may be out of date.
2305  * IMPLEMENTATION NOTE: There is some confusion over whether the
2306  * set of adjustments that needs to be done should be done in an atomic
2307  * manner or not. That is, if we are attempting to decrement the semval
2308  * should we queue up and wait until we can do so legally?
2309  * The original implementation attempted to do this (queue and wait).
2310  * The current implementation does not do so. The POSIX standard
2311  * and SVID should be consulted to determine what behavior is mandated.
2312  */
exit_sem(struct task_struct * tsk)2313 void exit_sem(struct task_struct *tsk)
2314 {
2315 	struct sem_undo_list *ulp;
2316 
2317 	ulp = tsk->sysvsem.undo_list;
2318 	if (!ulp)
2319 		return;
2320 	tsk->sysvsem.undo_list = NULL;
2321 
2322 	if (!refcount_dec_and_test(&ulp->refcnt))
2323 		return;
2324 
2325 	for (;;) {
2326 		struct sem_array *sma;
2327 		struct sem_undo *un;
2328 		int semid, i;
2329 		DEFINE_WAKE_Q(wake_q);
2330 
2331 		cond_resched();
2332 
2333 		rcu_read_lock();
2334 		un = list_entry_rcu(ulp->list_proc.next,
2335 				    struct sem_undo, list_proc);
2336 		if (&un->list_proc == &ulp->list_proc) {
2337 			/*
2338 			 * We must wait for freeary() before freeing this ulp,
2339 			 * in case we raced with last sem_undo. There is a small
2340 			 * possibility where we exit while freeary() didn't
2341 			 * finish unlocking sem_undo_list.
2342 			 */
2343 			spin_lock(&ulp->lock);
2344 			spin_unlock(&ulp->lock);
2345 			rcu_read_unlock();
2346 			break;
2347 		}
2348 		spin_lock(&ulp->lock);
2349 		semid = un->semid;
2350 		spin_unlock(&ulp->lock);
2351 
2352 		/* exit_sem raced with IPC_RMID, nothing to do */
2353 		if (semid == -1) {
2354 			rcu_read_unlock();
2355 			continue;
2356 		}
2357 
2358 		sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2359 		/* exit_sem raced with IPC_RMID, nothing to do */
2360 		if (IS_ERR(sma)) {
2361 			rcu_read_unlock();
2362 			continue;
2363 		}
2364 
2365 		sem_lock(sma, NULL, -1);
2366 		/* exit_sem raced with IPC_RMID, nothing to do */
2367 		if (!ipc_valid_object(&sma->sem_perm)) {
2368 			sem_unlock(sma, -1);
2369 			rcu_read_unlock();
2370 			continue;
2371 		}
2372 		un = __lookup_undo(ulp, semid);
2373 		if (un == NULL) {
2374 			/* exit_sem raced with IPC_RMID+semget() that created
2375 			 * exactly the same semid. Nothing to do.
2376 			 */
2377 			sem_unlock(sma, -1);
2378 			rcu_read_unlock();
2379 			continue;
2380 		}
2381 
2382 		/* remove un from the linked lists */
2383 		ipc_assert_locked_object(&sma->sem_perm);
2384 		list_del(&un->list_id);
2385 
2386 		spin_lock(&ulp->lock);
2387 		list_del_rcu(&un->list_proc);
2388 		spin_unlock(&ulp->lock);
2389 
2390 		/* perform adjustments registered in un */
2391 		for (i = 0; i < sma->sem_nsems; i++) {
2392 			struct sem *semaphore = &sma->sems[i];
2393 			if (un->semadj[i]) {
2394 				semaphore->semval += un->semadj[i];
2395 				/*
2396 				 * Range checks of the new semaphore value,
2397 				 * not defined by sus:
2398 				 * - Some unices ignore the undo entirely
2399 				 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2400 				 * - some cap the value (e.g. FreeBSD caps
2401 				 *   at 0, but doesn't enforce SEMVMX)
2402 				 *
2403 				 * Linux caps the semaphore value, both at 0
2404 				 * and at SEMVMX.
2405 				 *
2406 				 *	Manfred <manfred@colorfullife.com>
2407 				 */
2408 				if (semaphore->semval < 0)
2409 					semaphore->semval = 0;
2410 				if (semaphore->semval > SEMVMX)
2411 					semaphore->semval = SEMVMX;
2412 				ipc_update_pid(&semaphore->sempid, task_tgid(current));
2413 			}
2414 		}
2415 		/* maybe some queued-up processes were waiting for this */
2416 		do_smart_update(sma, NULL, 0, 1, &wake_q);
2417 		sem_unlock(sma, -1);
2418 		rcu_read_unlock();
2419 		wake_up_q(&wake_q);
2420 
2421 		kfree_rcu(un, rcu);
2422 	}
2423 	kfree(ulp);
2424 }
2425 
2426 #ifdef CONFIG_PROC_FS
sysvipc_sem_proc_show(struct seq_file * s,void * it)2427 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2428 {
2429 	struct user_namespace *user_ns = seq_user_ns(s);
2430 	struct kern_ipc_perm *ipcp = it;
2431 	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
2432 	time64_t sem_otime;
2433 
2434 	/*
2435 	 * The proc interface isn't aware of sem_lock(), it calls
2436 	 * ipc_lock_object() directly (in sysvipc_find_ipc).
2437 	 * In order to stay compatible with sem_lock(), we must
2438 	 * enter / leave complex_mode.
2439 	 */
2440 	complexmode_enter(sma);
2441 
2442 	sem_otime = get_semotime(sma);
2443 
2444 	seq_printf(s,
2445 		   "%10d %10d  %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
2446 		   sma->sem_perm.key,
2447 		   sma->sem_perm.id,
2448 		   sma->sem_perm.mode,
2449 		   sma->sem_nsems,
2450 		   from_kuid_munged(user_ns, sma->sem_perm.uid),
2451 		   from_kgid_munged(user_ns, sma->sem_perm.gid),
2452 		   from_kuid_munged(user_ns, sma->sem_perm.cuid),
2453 		   from_kgid_munged(user_ns, sma->sem_perm.cgid),
2454 		   sem_otime,
2455 		   sma->sem_ctime);
2456 
2457 	complexmode_tryleave(sma);
2458 
2459 	return 0;
2460 }
2461 #endif
2462