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 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 
sem_init_ns(struct ipc_namespace * ns)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
sem_exit_ns(struct ipc_namespace * 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 
sem_init(void)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  */
unmerge_queues(struct sem_array * sma)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  */
merge_queues(struct sem_array * sma)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 
sem_rcu_free(struct rcu_head * head)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  */
complexmode_enter(struct sem_array * sma)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  */
complexmode_tryleave(struct sem_array * sma)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  */
sem_lock(struct sem_array * sma,struct sembuf * sops,int nsops)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 
sem_unlock(struct sem_array * sma,int locknum)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  */
sem_obtain_object(struct ipc_namespace * ns,int id)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 
sem_obtain_object_check(struct ipc_namespace * ns,int id)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 
sem_lock_and_putref(struct sem_array * sma)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 
sem_rmid(struct ipc_namespace * ns,struct sem_array * s)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 
sem_alloc(size_t nsems)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  */
newary(struct ipc_namespace * ns,struct ipc_params * params)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  */
sem_more_checks(struct kern_ipc_perm * ipcp,struct ipc_params * params)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 
ksys_semget(key_t key,int nsems,int semflg)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 
SYSCALL_DEFINE3(semget,key_t,key,int,nsems,int,semflg)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  */
perform_atomic_semop_slow(struct sem_array * sma,struct sem_queue * q)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 
perform_atomic_semop(struct sem_array * sma,struct sem_queue * q)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 
wake_up_sem_queue_prepare(struct sem_queue * q,int error,struct wake_q_head * wake_q)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 
unlink_queue(struct sem_array * sma,struct sem_queue * q)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  */
check_restart(struct sem_array * sma,struct sem_queue * q)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  */
wake_const_ops(struct sem_array * sma,int semnum,struct wake_q_head * wake_q)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  */
do_smart_wakeup_zero(struct sem_array * sma,struct sembuf * sops,int nsops,struct wake_q_head * wake_q)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  */
update_queue(struct sem_array * sma,int semnum,struct wake_q_head * wake_q)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  */
set_semotime(struct sem_array * sma,struct sembuf * sops)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  */
do_smart_update(struct sem_array * sma,struct sembuf * sops,int nsops,int otime,struct wake_q_head * wake_q)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  */
check_qop(struct sem_array * sma,int semnum,struct sem_queue * q,bool count_zero)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  */
count_semcnt(struct sem_array * sma,ushort semnum,bool count_zero)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  */
freeary(struct ipc_namespace * ns,struct kern_ipc_perm * ipcp)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 
copy_semid_to_user(void __user * buf,struct semid64_ds * in,int version)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 
get_semotime(struct sem_array * sma)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 
semctl_stat(struct ipc_namespace * ns,int semid,int cmd,struct semid64_ds * semid64)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 
semctl_info(struct ipc_namespace * ns,int semid,int cmd,void __user * p)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 
semctl_setval(struct ipc_namespace * ns,int semid,int semnum,int val)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 
semctl_main(struct ipc_namespace * ns,int semid,int semnum,int cmd,void __user * p)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
copy_semid_from_user(struct semid64_ds * out,void __user * buf,int version)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  */
semctl_down(struct ipc_namespace * ns,int semid,int cmd,struct semid64_ds * semid64)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 
ksys_semctl(int semid,int semnum,int cmd,unsigned long arg,int version)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 
SYSCALL_DEFINE4(semctl,int,semid,int,semnum,int,cmd,unsigned long,arg)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
ksys_old_semctl(int semid,int semnum,int cmd,unsigned long arg)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 
SYSCALL_DEFINE4(old_semctl,int,semid,int,semnum,int,cmd,unsigned long,arg)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 
copy_compat_semid_from_user(struct semid64_ds * out,void __user * buf,int version)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 
copy_compat_semid_to_user(void __user * buf,struct semid64_ds * in,int version)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 
compat_ksys_semctl(int semid,int semnum,int cmd,int arg,int version)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 
COMPAT_SYSCALL_DEFINE4(semctl,int,semid,int,semnum,int,cmd,int,arg)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
compat_ksys_old_semctl(int semid,int semnum,int cmd,int arg)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 
COMPAT_SYSCALL_DEFINE4(old_semctl,int,semid,int,semnum,int,cmd,int,arg)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  */
get_undo_list(struct sem_undo_list ** undo_listp)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 
__lookup_undo(struct sem_undo_list * ulp,int semid)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 
lookup_undo(struct sem_undo_list * ulp,int semid)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  */
find_alloc_undo(struct ipc_namespace * ns,int semid)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 
__do_semtimedop(int semid,struct sembuf * sops,unsigned nsops,const struct timespec64 * timeout,struct ipc_namespace * ns)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 
do_semtimedop(int semid,struct sembuf __user * tsops,unsigned nsops,const struct timespec64 * timeout)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 
ksys_semtimedop(int semid,struct sembuf __user * tsops,unsigned int nsops,const struct __kernel_timespec __user * timeout)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 
SYSCALL_DEFINE4(semtimedop,int,semid,struct sembuf __user *,tsops,unsigned int,nsops,const struct __kernel_timespec __user *,timeout)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
compat_ksys_semtimedop(int semid,struct sembuf __user * tsems,unsigned int nsops,const struct old_timespec32 __user * timeout)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 
SYSCALL_DEFINE4(semtimedop_time32,int,semid,struct sembuf __user *,tsems,unsigned int,nsops,const struct old_timespec32 __user *,timeout)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 
SYSCALL_DEFINE3(semop,int,semid,struct sembuf __user *,tsops,unsigned,nsops)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 
copy_semundo(unsigned long clone_flags,struct task_struct * tsk)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  */
exit_sem(struct task_struct * tsk)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 <manfred@colorfullife.com>
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
sysvipc_sem_proc_show(struct seq_file * s,void * it)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
2485