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Linux/ipc/sem.c

  1 /*
  2  * linux/ipc/sem.c
  3  * Copyright (C) 1992 Krishna Balasubramanian
  4  * Copyright (C) 1995 Eric Schenk, Bruno Haible
  5  *
  6  * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
  7  *
  8  * SMP-threaded, sysctl's added
  9  * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
 10  * Enforced range limit on SEM_UNDO
 11  * (c) 2001 Red Hat Inc
 12  * Lockless wakeup
 13  * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
 14  * (c) 2016 Davidlohr Bueso <dave@stgolabs.net>
 15  * Further wakeup optimizations, documentation
 16  * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
 17  *
 18  * support for audit of ipc object properties and permission changes
 19  * Dustin Kirkland <dustin.kirkland@us.ibm.com>
 20  *
 21  * namespaces support
 22  * OpenVZ, SWsoft Inc.
 23  * Pavel Emelianov <xemul@openvz.org>
 24  *
 25  * Implementation notes: (May 2010)
 26  * This file implements System V semaphores.
 27  *
 28  * User space visible behavior:
 29  * - FIFO ordering for semop() operations (just FIFO, not starvation
 30  *   protection)
 31  * - multiple semaphore operations that alter the same semaphore in
 32  *   one semop() are handled.
 33  * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
 34  *   SETALL calls.
 35  * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
 36  * - undo adjustments at process exit are limited to 0..SEMVMX.
 37  * - namespace are supported.
 38  * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
 39  *   to /proc/sys/kernel/sem.
 40  * - statistics about the usage are reported in /proc/sysvipc/sem.
 41  *
 42  * Internals:
 43  * - scalability:
 44  *   - all global variables are read-mostly.
 45  *   - semop() calls and semctl(RMID) are synchronized by RCU.
 46  *   - most operations do write operations (actually: spin_lock calls) to
 47  *     the per-semaphore array structure.
 48  *   Thus: Perfect SMP scaling between independent semaphore arrays.
 49  *         If multiple semaphores in one array are used, then cache line
 50  *         trashing on the semaphore array spinlock will limit the scaling.
 51  * - semncnt and semzcnt are calculated on demand in count_semcnt()
 52  * - the task that performs a successful semop() scans the list of all
 53  *   sleeping tasks and completes any pending operations that can be fulfilled.
 54  *   Semaphores are actively given to waiting tasks (necessary for FIFO).
 55  *   (see update_queue())
 56  * - To improve the scalability, the actual wake-up calls are performed after
 57  *   dropping all locks. (see wake_up_sem_queue_prepare())
 58  * - All work is done by the waker, the woken up task does not have to do
 59  *   anything - not even acquiring a lock or dropping a refcount.
 60  * - A woken up task may not even touch the semaphore array anymore, it may
 61  *   have been destroyed already by a semctl(RMID).
 62  * - UNDO values are stored in an array (one per process and per
 63  *   semaphore array, lazily allocated). For backwards compatibility, multiple
 64  *   modes for the UNDO variables are supported (per process, per thread)
 65  *   (see copy_semundo, CLONE_SYSVSEM)
 66  * - There are two lists of the pending operations: a per-array list
 67  *   and per-semaphore list (stored in the array). This allows to achieve FIFO
 68  *   ordering without always scanning all pending operations.
 69  *   The worst-case behavior is nevertheless O(N^2) for N wakeups.
 70  */
 71 
 72 #include <linux/slab.h>
 73 #include <linux/spinlock.h>
 74 #include <linux/init.h>
 75 #include <linux/proc_fs.h>
 76 #include <linux/time.h>
 77 #include <linux/security.h>
 78 #include <linux/syscalls.h>
 79 #include <linux/audit.h>
 80 #include <linux/capability.h>
 81 #include <linux/seq_file.h>
 82 #include <linux/rwsem.h>
 83 #include <linux/nsproxy.h>
 84 #include <linux/ipc_namespace.h>
 85 
 86 #include <linux/uaccess.h>
 87 #include "util.h"
 88 
 89 /* One semaphore structure for each semaphore in the system. */
 90 struct sem {
 91         int     semval;         /* current value */
 92         /*
 93          * PID of the process that last modified the semaphore. For
 94          * Linux, specifically these are:
 95          *  - semop
 96          *  - semctl, via SETVAL and SETALL.
 97          *  - at task exit when performing undo adjustments (see exit_sem).
 98          */
 99         int     sempid;
100         spinlock_t      lock;   /* spinlock for fine-grained semtimedop */
101         struct list_head pending_alter; /* pending single-sop operations */
102                                         /* that alter the semaphore */
103         struct list_head pending_const; /* pending single-sop operations */
104                                         /* that do not alter the semaphore*/
105         time_t  sem_otime;      /* candidate for sem_otime */
106 } ____cacheline_aligned_in_smp;
107 
108 /* One queue for each sleeping process in the system. */
109 struct sem_queue {
110         struct list_head        list;    /* queue of pending operations */
111         struct task_struct      *sleeper; /* this process */
112         struct sem_undo         *undo;   /* undo structure */
113         int                     pid;     /* process id of requesting process */
114         int                     status;  /* completion status of operation */
115         struct sembuf           *sops;   /* array of pending operations */
116         struct sembuf           *blocking; /* the operation that blocked */
117         int                     nsops;   /* number of operations */
118         bool                    alter;   /* does *sops alter the array? */
119         bool                    dupsop;  /* sops on more than one sem_num */
120 };
121 
122 /* Each task has a list of undo requests. They are executed automatically
123  * when the process exits.
124  */
125 struct sem_undo {
126         struct list_head        list_proc;      /* per-process list: *
127                                                  * all undos from one process
128                                                  * rcu protected */
129         struct rcu_head         rcu;            /* rcu struct for sem_undo */
130         struct sem_undo_list    *ulp;           /* back ptr to sem_undo_list */
131         struct list_head        list_id;        /* per semaphore array list:
132                                                  * all undos for one array */
133         int                     semid;          /* semaphore set identifier */
134         short                   *semadj;        /* array of adjustments */
135                                                 /* one per semaphore */
136 };
137 
138 /* sem_undo_list controls shared access to the list of sem_undo structures
139  * that may be shared among all a CLONE_SYSVSEM task group.
140  */
141 struct sem_undo_list {
142         atomic_t                refcnt;
143         spinlock_t              lock;
144         struct list_head        list_proc;
145 };
146 
147 
148 #define sem_ids(ns)     ((ns)->ids[IPC_SEM_IDS])
149 
150 #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
151 
152 static int newary(struct ipc_namespace *, struct ipc_params *);
153 static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
154 #ifdef CONFIG_PROC_FS
155 static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
156 #endif
157 
158 #define SEMMSL_FAST     256 /* 512 bytes on stack */
159 #define SEMOPM_FAST     64  /* ~ 372 bytes on stack */
160 
161 /*
162  * Locking:
163  * a) global sem_lock() for read/write
164  *      sem_undo.id_next,
165  *      sem_array.complex_count,
166  *      sem_array.complex_mode
167  *      sem_array.pending{_alter,_const},
168  *      sem_array.sem_undo
169  *
170  * b) global or semaphore sem_lock() for read/write:
171  *      sem_array.sem_base[i].pending_{const,alter}:
172  *      sem_array.complex_mode (for read)
173  *
174  * c) special:
175  *      sem_undo_list.list_proc:
176  *      * undo_list->lock for write
177  *      * rcu for read
178  */
179 
180 #define sc_semmsl       sem_ctls[0]
181 #define sc_semmns       sem_ctls[1]
182 #define sc_semopm       sem_ctls[2]
183 #define sc_semmni       sem_ctls[3]
184 
185 void sem_init_ns(struct ipc_namespace *ns)
186 {
187         ns->sc_semmsl = SEMMSL;
188         ns->sc_semmns = SEMMNS;
189         ns->sc_semopm = SEMOPM;
190         ns->sc_semmni = SEMMNI;
191         ns->used_sems = 0;
192         ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
193 }
194 
195 #ifdef CONFIG_IPC_NS
196 void sem_exit_ns(struct ipc_namespace *ns)
197 {
198         free_ipcs(ns, &sem_ids(ns), freeary);
199         idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
200 }
201 #endif
202 
203 void __init sem_init(void)
204 {
205         sem_init_ns(&init_ipc_ns);
206         ipc_init_proc_interface("sysvipc/sem",
207                                 "       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
208                                 IPC_SEM_IDS, sysvipc_sem_proc_show);
209 }
210 
211 /**
212  * unmerge_queues - unmerge queues, if possible.
213  * @sma: semaphore array
214  *
215  * The function unmerges the wait queues if complex_count is 0.
216  * It must be called prior to dropping the global semaphore array lock.
217  */
218 static void unmerge_queues(struct sem_array *sma)
219 {
220         struct sem_queue *q, *tq;
221 
222         /* complex operations still around? */
223         if (sma->complex_count)
224                 return;
225         /*
226          * We will switch back to simple mode.
227          * Move all pending operation back into the per-semaphore
228          * queues.
229          */
230         list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
231                 struct sem *curr;
232                 curr = &sma->sem_base[q->sops[0].sem_num];
233 
234                 list_add_tail(&q->list, &curr->pending_alter);
235         }
236         INIT_LIST_HEAD(&sma->pending_alter);
237 }
238 
239 /**
240  * merge_queues - merge single semop queues into global queue
241  * @sma: semaphore array
242  *
243  * This function merges all per-semaphore queues into the global queue.
244  * It is necessary to achieve FIFO ordering for the pending single-sop
245  * operations when a multi-semop operation must sleep.
246  * Only the alter operations must be moved, the const operations can stay.
247  */
248 static void merge_queues(struct sem_array *sma)
249 {
250         int i;
251         for (i = 0; i < sma->sem_nsems; i++) {
252                 struct sem *sem = sma->sem_base + i;
253 
254                 list_splice_init(&sem->pending_alter, &sma->pending_alter);
255         }
256 }
257 
258 static void sem_rcu_free(struct rcu_head *head)
259 {
260         struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
261         struct sem_array *sma = ipc_rcu_to_struct(p);
262 
263         security_sem_free(sma);
264         ipc_rcu_free(head);
265 }
266 
267 /*
268  * Enter the mode suitable for non-simple operations:
269  * Caller must own sem_perm.lock.
270  */
271 static void complexmode_enter(struct sem_array *sma)
272 {
273         int i;
274         struct sem *sem;
275 
276         if (sma->complex_mode)  {
277                 /* We are already in complex_mode. Nothing to do */
278                 return;
279         }
280 
281         /* We need a full barrier after seting complex_mode:
282          * The write to complex_mode must be visible
283          * before we read the first sem->lock spinlock state.
284          */
285         smp_store_mb(sma->complex_mode, true);
286 
287         for (i = 0; i < sma->sem_nsems; i++) {
288                 sem = sma->sem_base + i;
289                 spin_unlock_wait(&sem->lock);
290         }
291         /*
292          * spin_unlock_wait() is not a memory barriers, it is only a
293          * control barrier. The code must pair with spin_unlock(&sem->lock),
294          * thus just the control barrier is insufficient.
295          *
296          * smp_rmb() is sufficient, as writes cannot pass the control barrier.
297          */
298         smp_rmb();
299 }
300 
301 /*
302  * Try to leave the mode that disallows simple operations:
303  * Caller must own sem_perm.lock.
304  */
305 static void complexmode_tryleave(struct sem_array *sma)
306 {
307         if (sma->complex_count)  {
308                 /* Complex ops are sleeping.
309                  * We must stay in complex mode
310                  */
311                 return;
312         }
313         /*
314          * Immediately after setting complex_mode to false,
315          * a simple op can start. Thus: all memory writes
316          * performed by the current operation must be visible
317          * before we set complex_mode to false.
318          */
319         smp_store_release(&sma->complex_mode, false);
320 }
321 
322 #define SEM_GLOBAL_LOCK (-1)
323 /*
324  * If the request contains only one semaphore operation, and there are
325  * no complex transactions pending, lock only the semaphore involved.
326  * Otherwise, lock the entire semaphore array, since we either have
327  * multiple semaphores in our own semops, or we need to look at
328  * semaphores from other pending complex operations.
329  */
330 static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
331                               int nsops)
332 {
333         struct sem *sem;
334 
335         if (nsops != 1) {
336                 /* Complex operation - acquire a full lock */
337                 ipc_lock_object(&sma->sem_perm);
338 
339                 /* Prevent parallel simple ops */
340                 complexmode_enter(sma);
341                 return SEM_GLOBAL_LOCK;
342         }
343 
344         /*
345          * Only one semaphore affected - try to optimize locking.
346          * Optimized locking is possible if no complex operation
347          * is either enqueued or processed right now.
348          *
349          * Both facts are tracked by complex_mode.
350          */
351         sem = sma->sem_base + sops->sem_num;
352 
353         /*
354          * Initial check for complex_mode. Just an optimization,
355          * no locking, no memory barrier.
356          */
357         if (!sma->complex_mode) {
358                 /*
359                  * It appears that no complex operation is around.
360                  * Acquire the per-semaphore lock.
361                  */
362                 spin_lock(&sem->lock);
363 
364                 /*
365                  * See 51d7d5205d33
366                  * ("powerpc: Add smp_mb() to arch_spin_is_locked()"):
367                  * A full barrier is required: the write of sem->lock
368                  * must be visible before the read is executed
369                  */
370                 smp_mb();
371 
372                 if (!smp_load_acquire(&sma->complex_mode)) {
373                         /* fast path successful! */
374                         return sops->sem_num;
375                 }
376                 spin_unlock(&sem->lock);
377         }
378 
379         /* slow path: acquire the full lock */
380         ipc_lock_object(&sma->sem_perm);
381 
382         if (sma->complex_count == 0) {
383                 /* False alarm:
384                  * There is no complex operation, thus we can switch
385                  * back to the fast path.
386                  */
387                 spin_lock(&sem->lock);
388                 ipc_unlock_object(&sma->sem_perm);
389                 return sops->sem_num;
390         } else {
391                 /* Not a false alarm, thus complete the sequence for a
392                  * full lock.
393                  */
394                 complexmode_enter(sma);
395                 return SEM_GLOBAL_LOCK;
396         }
397 }
398 
399 static inline void sem_unlock(struct sem_array *sma, int locknum)
400 {
401         if (locknum == SEM_GLOBAL_LOCK) {
402                 unmerge_queues(sma);
403                 complexmode_tryleave(sma);
404                 ipc_unlock_object(&sma->sem_perm);
405         } else {
406                 struct sem *sem = sma->sem_base + locknum;
407                 spin_unlock(&sem->lock);
408         }
409 }
410 
411 /*
412  * sem_lock_(check_) routines are called in the paths where the rwsem
413  * is not held.
414  *
415  * The caller holds the RCU read lock.
416  */
417 static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
418 {
419         struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
420 
421         if (IS_ERR(ipcp))
422                 return ERR_CAST(ipcp);
423 
424         return container_of(ipcp, struct sem_array, sem_perm);
425 }
426 
427 static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
428                                                         int id)
429 {
430         struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
431 
432         if (IS_ERR(ipcp))
433                 return ERR_CAST(ipcp);
434 
435         return container_of(ipcp, struct sem_array, sem_perm);
436 }
437 
438 static inline void sem_lock_and_putref(struct sem_array *sma)
439 {
440         sem_lock(sma, NULL, -1);
441         ipc_rcu_putref(sma, sem_rcu_free);
442 }
443 
444 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
445 {
446         ipc_rmid(&sem_ids(ns), &s->sem_perm);
447 }
448 
449 /**
450  * newary - Create a new semaphore set
451  * @ns: namespace
452  * @params: ptr to the structure that contains key, semflg and nsems
453  *
454  * Called with sem_ids.rwsem held (as a writer)
455  */
456 static int newary(struct ipc_namespace *ns, struct ipc_params *params)
457 {
458         int id;
459         int retval;
460         struct sem_array *sma;
461         int size;
462         key_t key = params->key;
463         int nsems = params->u.nsems;
464         int semflg = params->flg;
465         int i;
466 
467         if (!nsems)
468                 return -EINVAL;
469         if (ns->used_sems + nsems > ns->sc_semmns)
470                 return -ENOSPC;
471 
472         size = sizeof(*sma) + nsems * sizeof(struct sem);
473         sma = ipc_rcu_alloc(size);
474         if (!sma)
475                 return -ENOMEM;
476 
477         memset(sma, 0, size);
478 
479         sma->sem_perm.mode = (semflg & S_IRWXUGO);
480         sma->sem_perm.key = key;
481 
482         sma->sem_perm.security = NULL;
483         retval = security_sem_alloc(sma);
484         if (retval) {
485                 ipc_rcu_putref(sma, ipc_rcu_free);
486                 return retval;
487         }
488 
489         sma->sem_base = (struct sem *) &sma[1];
490 
491         for (i = 0; i < nsems; i++) {
492                 INIT_LIST_HEAD(&sma->sem_base[i].pending_alter);
493                 INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
494                 spin_lock_init(&sma->sem_base[i].lock);
495         }
496 
497         sma->complex_count = 0;
498         sma->complex_mode = true; /* dropped by sem_unlock below */
499         INIT_LIST_HEAD(&sma->pending_alter);
500         INIT_LIST_HEAD(&sma->pending_const);
501         INIT_LIST_HEAD(&sma->list_id);
502         sma->sem_nsems = nsems;
503         sma->sem_ctime = get_seconds();
504 
505         id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
506         if (id < 0) {
507                 ipc_rcu_putref(sma, sem_rcu_free);
508                 return id;
509         }
510         ns->used_sems += nsems;
511 
512         sem_unlock(sma, -1);
513         rcu_read_unlock();
514 
515         return sma->sem_perm.id;
516 }
517 
518 
519 /*
520  * Called with sem_ids.rwsem and ipcp locked.
521  */
522 static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
523 {
524         struct sem_array *sma;
525 
526         sma = container_of(ipcp, struct sem_array, sem_perm);
527         return security_sem_associate(sma, semflg);
528 }
529 
530 /*
531  * Called with sem_ids.rwsem and ipcp locked.
532  */
533 static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
534                                 struct ipc_params *params)
535 {
536         struct sem_array *sma;
537 
538         sma = container_of(ipcp, struct sem_array, sem_perm);
539         if (params->u.nsems > sma->sem_nsems)
540                 return -EINVAL;
541 
542         return 0;
543 }
544 
545 SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
546 {
547         struct ipc_namespace *ns;
548         static const struct ipc_ops sem_ops = {
549                 .getnew = newary,
550                 .associate = sem_security,
551                 .more_checks = sem_more_checks,
552         };
553         struct ipc_params sem_params;
554 
555         ns = current->nsproxy->ipc_ns;
556 
557         if (nsems < 0 || nsems > ns->sc_semmsl)
558                 return -EINVAL;
559 
560         sem_params.key = key;
561         sem_params.flg = semflg;
562         sem_params.u.nsems = nsems;
563 
564         return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
565 }
566 
567 /**
568  * perform_atomic_semop[_slow] - Attempt to perform semaphore
569  *                               operations on a given array.
570  * @sma: semaphore array
571  * @q: struct sem_queue that describes the operation
572  *
573  * Caller blocking are as follows, based the value
574  * indicated by the semaphore operation (sem_op):
575  *
576  *  (1) >0 never blocks.
577  *  (2)  0 (wait-for-zero operation): semval is non-zero.
578  *  (3) <0 attempting to decrement semval to a value smaller than zero.
579  *
580  * Returns 0 if the operation was possible.
581  * Returns 1 if the operation is impossible, the caller must sleep.
582  * Returns <0 for error codes.
583  */
584 static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
585 {
586         int result, sem_op, nsops, pid;
587         struct sembuf *sop;
588         struct sem *curr;
589         struct sembuf *sops;
590         struct sem_undo *un;
591 
592         sops = q->sops;
593         nsops = q->nsops;
594         un = q->undo;
595 
596         for (sop = sops; sop < sops + nsops; sop++) {
597                 curr = sma->sem_base + sop->sem_num;
598                 sem_op = sop->sem_op;
599                 result = curr->semval;
600 
601                 if (!sem_op && result)
602                         goto would_block;
603 
604                 result += sem_op;
605                 if (result < 0)
606                         goto would_block;
607                 if (result > SEMVMX)
608                         goto out_of_range;
609 
610                 if (sop->sem_flg & SEM_UNDO) {
611                         int undo = un->semadj[sop->sem_num] - sem_op;
612                         /* Exceeding the undo range is an error. */
613                         if (undo < (-SEMAEM - 1) || undo > SEMAEM)
614                                 goto out_of_range;
615                         un->semadj[sop->sem_num] = undo;
616                 }
617 
618                 curr->semval = result;
619         }
620 
621         sop--;
622         pid = q->pid;
623         while (sop >= sops) {
624                 sma->sem_base[sop->sem_num].sempid = pid;
625                 sop--;
626         }
627 
628         return 0;
629 
630 out_of_range:
631         result = -ERANGE;
632         goto undo;
633 
634 would_block:
635         q->blocking = sop;
636 
637         if (sop->sem_flg & IPC_NOWAIT)
638                 result = -EAGAIN;
639         else
640                 result = 1;
641 
642 undo:
643         sop--;
644         while (sop >= sops) {
645                 sem_op = sop->sem_op;
646                 sma->sem_base[sop->sem_num].semval -= sem_op;
647                 if (sop->sem_flg & SEM_UNDO)
648                         un->semadj[sop->sem_num] += sem_op;
649                 sop--;
650         }
651 
652         return result;
653 }
654 
655 static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
656 {
657         int result, sem_op, nsops;
658         struct sembuf *sop;
659         struct sem *curr;
660         struct sembuf *sops;
661         struct sem_undo *un;
662 
663         sops = q->sops;
664         nsops = q->nsops;
665         un = q->undo;
666 
667         if (unlikely(q->dupsop))
668                 return perform_atomic_semop_slow(sma, q);
669 
670         /*
671          * We scan the semaphore set twice, first to ensure that the entire
672          * operation can succeed, therefore avoiding any pointless writes
673          * to shared memory and having to undo such changes in order to block
674          * until the operations can go through.
675          */
676         for (sop = sops; sop < sops + nsops; sop++) {
677                 curr = sma->sem_base + sop->sem_num;
678                 sem_op = sop->sem_op;
679                 result = curr->semval;
680 
681                 if (!sem_op && result)
682                         goto would_block; /* wait-for-zero */
683 
684                 result += sem_op;
685                 if (result < 0)
686                         goto would_block;
687 
688                 if (result > SEMVMX)
689                         return -ERANGE;
690 
691                 if (sop->sem_flg & SEM_UNDO) {
692                         int undo = un->semadj[sop->sem_num] - sem_op;
693 
694                         /* Exceeding the undo range is an error. */
695                         if (undo < (-SEMAEM - 1) || undo > SEMAEM)
696                                 return -ERANGE;
697                 }
698         }
699 
700         for (sop = sops; sop < sops + nsops; sop++) {
701                 curr = sma->sem_base + sop->sem_num;
702                 sem_op = sop->sem_op;
703                 result = curr->semval;
704 
705                 if (sop->sem_flg & SEM_UNDO) {
706                         int undo = un->semadj[sop->sem_num] - sem_op;
707 
708                         un->semadj[sop->sem_num] = undo;
709                 }
710                 curr->semval += sem_op;
711                 curr->sempid = q->pid;
712         }
713 
714         return 0;
715 
716 would_block:
717         q->blocking = sop;
718         return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
719 }
720 
721 static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
722                                              struct wake_q_head *wake_q)
723 {
724         wake_q_add(wake_q, q->sleeper);
725         /*
726          * Rely on the above implicit barrier, such that we can
727          * ensure that we hold reference to the task before setting
728          * q->status. Otherwise we could race with do_exit if the
729          * task is awoken by an external event before calling
730          * wake_up_process().
731          */
732         WRITE_ONCE(q->status, error);
733 }
734 
735 static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
736 {
737         list_del(&q->list);
738         if (q->nsops > 1)
739                 sma->complex_count--;
740 }
741 
742 /** check_restart(sma, q)
743  * @sma: semaphore array
744  * @q: the operation that just completed
745  *
746  * update_queue is O(N^2) when it restarts scanning the whole queue of
747  * waiting operations. Therefore this function checks if the restart is
748  * really necessary. It is called after a previously waiting operation
749  * modified the array.
750  * Note that wait-for-zero operations are handled without restart.
751  */
752 static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
753 {
754         /* pending complex alter operations are too difficult to analyse */
755         if (!list_empty(&sma->pending_alter))
756                 return 1;
757 
758         /* we were a sleeping complex operation. Too difficult */
759         if (q->nsops > 1)
760                 return 1;
761 
762         /* It is impossible that someone waits for the new value:
763          * - complex operations always restart.
764          * - wait-for-zero are handled seperately.
765          * - q is a previously sleeping simple operation that
766          *   altered the array. It must be a decrement, because
767          *   simple increments never sleep.
768          * - If there are older (higher priority) decrements
769          *   in the queue, then they have observed the original
770          *   semval value and couldn't proceed. The operation
771          *   decremented to value - thus they won't proceed either.
772          */
773         return 0;
774 }
775 
776 /**
777  * wake_const_ops - wake up non-alter tasks
778  * @sma: semaphore array.
779  * @semnum: semaphore that was modified.
780  * @wake_q: lockless wake-queue head.
781  *
782  * wake_const_ops must be called after a semaphore in a semaphore array
783  * was set to 0. If complex const operations are pending, wake_const_ops must
784  * be called with semnum = -1, as well as with the number of each modified
785  * semaphore.
786  * The tasks that must be woken up are added to @wake_q. The return code
787  * is stored in q->pid.
788  * The function returns 1 if at least one operation was completed successfully.
789  */
790 static int wake_const_ops(struct sem_array *sma, int semnum,
791                           struct wake_q_head *wake_q)
792 {
793         struct sem_queue *q, *tmp;
794         struct list_head *pending_list;
795         int semop_completed = 0;
796 
797         if (semnum == -1)
798                 pending_list = &sma->pending_const;
799         else
800                 pending_list = &sma->sem_base[semnum].pending_const;
801 
802         list_for_each_entry_safe(q, tmp, pending_list, list) {
803                 int error = perform_atomic_semop(sma, q);
804 
805                 if (error > 0)
806                         continue;
807                 /* operation completed, remove from queue & wakeup */
808                 unlink_queue(sma, q);
809 
810                 wake_up_sem_queue_prepare(q, error, wake_q);
811                 if (error == 0)
812                         semop_completed = 1;
813         }
814 
815         return semop_completed;
816 }
817 
818 /**
819  * do_smart_wakeup_zero - wakeup all wait for zero tasks
820  * @sma: semaphore array
821  * @sops: operations that were performed
822  * @nsops: number of operations
823  * @wake_q: lockless wake-queue head
824  *
825  * Checks all required queue for wait-for-zero operations, based
826  * on the actual changes that were performed on the semaphore array.
827  * The function returns 1 if at least one operation was completed successfully.
828  */
829 static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
830                                 int nsops, struct wake_q_head *wake_q)
831 {
832         int i;
833         int semop_completed = 0;
834         int got_zero = 0;
835 
836         /* first: the per-semaphore queues, if known */
837         if (sops) {
838                 for (i = 0; i < nsops; i++) {
839                         int num = sops[i].sem_num;
840 
841                         if (sma->sem_base[num].semval == 0) {
842                                 got_zero = 1;
843                                 semop_completed |= wake_const_ops(sma, num, wake_q);
844                         }
845                 }
846         } else {
847                 /*
848                  * No sops means modified semaphores not known.
849                  * Assume all were changed.
850                  */
851                 for (i = 0; i < sma->sem_nsems; i++) {
852                         if (sma->sem_base[i].semval == 0) {
853                                 got_zero = 1;
854                                 semop_completed |= wake_const_ops(sma, i, wake_q);
855                         }
856                 }
857         }
858         /*
859          * If one of the modified semaphores got 0,
860          * then check the global queue, too.
861          */
862         if (got_zero)
863                 semop_completed |= wake_const_ops(sma, -1, wake_q);
864 
865         return semop_completed;
866 }
867 
868 
869 /**
870  * update_queue - look for tasks that can be completed.
871  * @sma: semaphore array.
872  * @semnum: semaphore that was modified.
873  * @wake_q: lockless wake-queue head.
874  *
875  * update_queue must be called after a semaphore in a semaphore array
876  * was modified. If multiple semaphores were modified, update_queue must
877  * be called with semnum = -1, as well as with the number of each modified
878  * semaphore.
879  * The tasks that must be woken up are added to @wake_q. The return code
880  * is stored in q->pid.
881  * The function internally checks if const operations can now succeed.
882  *
883  * The function return 1 if at least one semop was completed successfully.
884  */
885 static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
886 {
887         struct sem_queue *q, *tmp;
888         struct list_head *pending_list;
889         int semop_completed = 0;
890 
891         if (semnum == -1)
892                 pending_list = &sma->pending_alter;
893         else
894                 pending_list = &sma->sem_base[semnum].pending_alter;
895 
896 again:
897         list_for_each_entry_safe(q, tmp, pending_list, list) {
898                 int error, restart;
899 
900                 /* If we are scanning the single sop, per-semaphore list of
901                  * one semaphore and that semaphore is 0, then it is not
902                  * necessary to scan further: simple increments
903                  * that affect only one entry succeed immediately and cannot
904                  * be in the  per semaphore pending queue, and decrements
905                  * cannot be successful if the value is already 0.
906                  */
907                 if (semnum != -1 && sma->sem_base[semnum].semval == 0)
908                         break;
909 
910                 error = perform_atomic_semop(sma, q);
911 
912                 /* Does q->sleeper still need to sleep? */
913                 if (error > 0)
914                         continue;
915 
916                 unlink_queue(sma, q);
917 
918                 if (error) {
919                         restart = 0;
920                 } else {
921                         semop_completed = 1;
922                         do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
923                         restart = check_restart(sma, q);
924                 }
925 
926                 wake_up_sem_queue_prepare(q, error, wake_q);
927                 if (restart)
928                         goto again;
929         }
930         return semop_completed;
931 }
932 
933 /**
934  * set_semotime - set sem_otime
935  * @sma: semaphore array
936  * @sops: operations that modified the array, may be NULL
937  *
938  * sem_otime is replicated to avoid cache line trashing.
939  * This function sets one instance to the current time.
940  */
941 static void set_semotime(struct sem_array *sma, struct sembuf *sops)
942 {
943         if (sops == NULL) {
944                 sma->sem_base[0].sem_otime = get_seconds();
945         } else {
946                 sma->sem_base[sops[0].sem_num].sem_otime =
947                                                         get_seconds();
948         }
949 }
950 
951 /**
952  * do_smart_update - optimized update_queue
953  * @sma: semaphore array
954  * @sops: operations that were performed
955  * @nsops: number of operations
956  * @otime: force setting otime
957  * @wake_q: lockless wake-queue head
958  *
959  * do_smart_update() does the required calls to update_queue and wakeup_zero,
960  * based on the actual changes that were performed on the semaphore array.
961  * Note that the function does not do the actual wake-up: the caller is
962  * responsible for calling wake_up_q().
963  * It is safe to perform this call after dropping all locks.
964  */
965 static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
966                             int otime, struct wake_q_head *wake_q)
967 {
968         int i;
969 
970         otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
971 
972         if (!list_empty(&sma->pending_alter)) {
973                 /* semaphore array uses the global queue - just process it. */
974                 otime |= update_queue(sma, -1, wake_q);
975         } else {
976                 if (!sops) {
977                         /*
978                          * No sops, thus the modified semaphores are not
979                          * known. Check all.
980                          */
981                         for (i = 0; i < sma->sem_nsems; i++)
982                                 otime |= update_queue(sma, i, wake_q);
983                 } else {
984                         /*
985                          * Check the semaphores that were increased:
986                          * - No complex ops, thus all sleeping ops are
987                          *   decrease.
988                          * - if we decreased the value, then any sleeping
989                          *   semaphore ops wont be able to run: If the
990                          *   previous value was too small, then the new
991                          *   value will be too small, too.
992                          */
993                         for (i = 0; i < nsops; i++) {
994                                 if (sops[i].sem_op > 0) {
995                                         otime |= update_queue(sma,
996                                                               sops[i].sem_num, wake_q);
997                                 }
998                         }
999                 }
1000         }
1001         if (otime)
1002                 set_semotime(sma, sops);
1003 }
1004 
1005 /*
1006  * check_qop: Test if a queued operation sleeps on the semaphore semnum
1007  */
1008 static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1009                         bool count_zero)
1010 {
1011         struct sembuf *sop = q->blocking;
1012 
1013         /*
1014          * Linux always (since 0.99.10) reported a task as sleeping on all
1015          * semaphores. This violates SUS, therefore it was changed to the
1016          * standard compliant behavior.
1017          * Give the administrators a chance to notice that an application
1018          * might misbehave because it relies on the Linux behavior.
1019          */
1020         pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1021                         "The task %s (%d) triggered the difference, watch for misbehavior.\n",
1022                         current->comm, task_pid_nr(current));
1023 
1024         if (sop->sem_num != semnum)
1025                 return 0;
1026 
1027         if (count_zero && sop->sem_op == 0)
1028                 return 1;
1029         if (!count_zero && sop->sem_op < 0)
1030                 return 1;
1031 
1032         return 0;
1033 }
1034 
1035 /* The following counts are associated to each semaphore:
1036  *   semncnt        number of tasks waiting on semval being nonzero
1037  *   semzcnt        number of tasks waiting on semval being zero
1038  *
1039  * Per definition, a task waits only on the semaphore of the first semop
1040  * that cannot proceed, even if additional operation would block, too.
1041  */
1042 static int count_semcnt(struct sem_array *sma, ushort semnum,
1043                         bool count_zero)
1044 {
1045         struct list_head *l;
1046         struct sem_queue *q;
1047         int semcnt;
1048 
1049         semcnt = 0;
1050         /* First: check the simple operations. They are easy to evaluate */
1051         if (count_zero)
1052                 l = &sma->sem_base[semnum].pending_const;
1053         else
1054                 l = &sma->sem_base[semnum].pending_alter;
1055 
1056         list_for_each_entry(q, l, list) {
1057                 /* all task on a per-semaphore list sleep on exactly
1058                  * that semaphore
1059                  */
1060                 semcnt++;
1061         }
1062 
1063         /* Then: check the complex operations. */
1064         list_for_each_entry(q, &sma->pending_alter, list) {
1065                 semcnt += check_qop(sma, semnum, q, count_zero);
1066         }
1067         if (count_zero) {
1068                 list_for_each_entry(q, &sma->pending_const, list) {
1069                         semcnt += check_qop(sma, semnum, q, count_zero);
1070                 }
1071         }
1072         return semcnt;
1073 }
1074 
1075 /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1076  * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1077  * remains locked on exit.
1078  */
1079 static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1080 {
1081         struct sem_undo *un, *tu;
1082         struct sem_queue *q, *tq;
1083         struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1084         int i;
1085         DEFINE_WAKE_Q(wake_q);
1086 
1087         /* Free the existing undo structures for this semaphore set.  */
1088         ipc_assert_locked_object(&sma->sem_perm);
1089         list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1090                 list_del(&un->list_id);
1091                 spin_lock(&un->ulp->lock);
1092                 un->semid = -1;
1093                 list_del_rcu(&un->list_proc);
1094                 spin_unlock(&un->ulp->lock);
1095                 kfree_rcu(un, rcu);
1096         }
1097 
1098         /* Wake up all pending processes and let them fail with EIDRM. */
1099         list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1100                 unlink_queue(sma, q);
1101                 wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1102         }
1103 
1104         list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1105                 unlink_queue(sma, q);
1106                 wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1107         }
1108         for (i = 0; i < sma->sem_nsems; i++) {
1109                 struct sem *sem = sma->sem_base + i;
1110                 list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1111                         unlink_queue(sma, q);
1112                         wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1113                 }
1114                 list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1115                         unlink_queue(sma, q);
1116                         wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1117                 }
1118         }
1119 
1120         /* Remove the semaphore set from the IDR */
1121         sem_rmid(ns, sma);
1122         sem_unlock(sma, -1);
1123         rcu_read_unlock();
1124 
1125         wake_up_q(&wake_q);
1126         ns->used_sems -= sma->sem_nsems;
1127         ipc_rcu_putref(sma, sem_rcu_free);
1128 }
1129 
1130 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1131 {
1132         switch (version) {
1133         case IPC_64:
1134                 return copy_to_user(buf, in, sizeof(*in));
1135         case IPC_OLD:
1136             {
1137                 struct semid_ds out;
1138 
1139                 memset(&out, 0, sizeof(out));
1140 
1141                 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1142 
1143                 out.sem_otime   = in->sem_otime;
1144                 out.sem_ctime   = in->sem_ctime;
1145                 out.sem_nsems   = in->sem_nsems;
1146 
1147                 return copy_to_user(buf, &out, sizeof(out));
1148             }
1149         default:
1150                 return -EINVAL;
1151         }
1152 }
1153 
1154 static time_t get_semotime(struct sem_array *sma)
1155 {
1156         int i;
1157         time_t res;
1158 
1159         res = sma->sem_base[0].sem_otime;
1160         for (i = 1; i < sma->sem_nsems; i++) {
1161                 time_t to = sma->sem_base[i].sem_otime;
1162 
1163                 if (to > res)
1164                         res = to;
1165         }
1166         return res;
1167 }
1168 
1169 static int semctl_nolock(struct ipc_namespace *ns, int semid,
1170                          int cmd, int version, void __user *p)
1171 {
1172         int err;
1173         struct sem_array *sma;
1174 
1175         switch (cmd) {
1176         case IPC_INFO:
1177         case SEM_INFO:
1178         {
1179                 struct seminfo seminfo;
1180                 int max_id;
1181 
1182                 err = security_sem_semctl(NULL, cmd);
1183                 if (err)
1184                         return err;
1185 
1186                 memset(&seminfo, 0, sizeof(seminfo));
1187                 seminfo.semmni = ns->sc_semmni;
1188                 seminfo.semmns = ns->sc_semmns;
1189                 seminfo.semmsl = ns->sc_semmsl;
1190                 seminfo.semopm = ns->sc_semopm;
1191                 seminfo.semvmx = SEMVMX;
1192                 seminfo.semmnu = SEMMNU;
1193                 seminfo.semmap = SEMMAP;
1194                 seminfo.semume = SEMUME;
1195                 down_read(&sem_ids(ns).rwsem);
1196                 if (cmd == SEM_INFO) {
1197                         seminfo.semusz = sem_ids(ns).in_use;
1198                         seminfo.semaem = ns->used_sems;
1199                 } else {
1200                         seminfo.semusz = SEMUSZ;
1201                         seminfo.semaem = SEMAEM;
1202                 }
1203                 max_id = ipc_get_maxid(&sem_ids(ns));
1204                 up_read(&sem_ids(ns).rwsem);
1205                 if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1206                         return -EFAULT;
1207                 return (max_id < 0) ? 0 : max_id;
1208         }
1209         case IPC_STAT:
1210         case SEM_STAT:
1211         {
1212                 struct semid64_ds tbuf;
1213                 int id = 0;
1214 
1215                 memset(&tbuf, 0, sizeof(tbuf));
1216 
1217                 rcu_read_lock();
1218                 if (cmd == SEM_STAT) {
1219                         sma = sem_obtain_object(ns, semid);
1220                         if (IS_ERR(sma)) {
1221                                 err = PTR_ERR(sma);
1222                                 goto out_unlock;
1223                         }
1224                         id = sma->sem_perm.id;
1225                 } else {
1226                         sma = sem_obtain_object_check(ns, semid);
1227                         if (IS_ERR(sma)) {
1228                                 err = PTR_ERR(sma);
1229                                 goto out_unlock;
1230                         }
1231                 }
1232 
1233                 err = -EACCES;
1234                 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1235                         goto out_unlock;
1236 
1237                 err = security_sem_semctl(sma, cmd);
1238                 if (err)
1239                         goto out_unlock;
1240 
1241                 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1242                 tbuf.sem_otime = get_semotime(sma);
1243                 tbuf.sem_ctime = sma->sem_ctime;
1244                 tbuf.sem_nsems = sma->sem_nsems;
1245                 rcu_read_unlock();
1246                 if (copy_semid_to_user(p, &tbuf, version))
1247                         return -EFAULT;
1248                 return id;
1249         }
1250         default:
1251                 return -EINVAL;
1252         }
1253 out_unlock:
1254         rcu_read_unlock();
1255         return err;
1256 }
1257 
1258 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1259                 unsigned long arg)
1260 {
1261         struct sem_undo *un;
1262         struct sem_array *sma;
1263         struct sem *curr;
1264         int err, val;
1265         DEFINE_WAKE_Q(wake_q);
1266 
1267 #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1268         /* big-endian 64bit */
1269         val = arg >> 32;
1270 #else
1271         /* 32bit or little-endian 64bit */
1272         val = arg;
1273 #endif
1274 
1275         if (val > SEMVMX || val < 0)
1276                 return -ERANGE;
1277 
1278         rcu_read_lock();
1279         sma = sem_obtain_object_check(ns, semid);
1280         if (IS_ERR(sma)) {
1281                 rcu_read_unlock();
1282                 return PTR_ERR(sma);
1283         }
1284 
1285         if (semnum < 0 || semnum >= sma->sem_nsems) {
1286                 rcu_read_unlock();
1287                 return -EINVAL;
1288         }
1289 
1290 
1291         if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1292                 rcu_read_unlock();
1293                 return -EACCES;
1294         }
1295 
1296         err = security_sem_semctl(sma, SETVAL);
1297         if (err) {
1298                 rcu_read_unlock();
1299                 return -EACCES;
1300         }
1301 
1302         sem_lock(sma, NULL, -1);
1303 
1304         if (!ipc_valid_object(&sma->sem_perm)) {
1305                 sem_unlock(sma, -1);
1306                 rcu_read_unlock();
1307                 return -EIDRM;
1308         }
1309 
1310         curr = &sma->sem_base[semnum];
1311 
1312         ipc_assert_locked_object(&sma->sem_perm);
1313         list_for_each_entry(un, &sma->list_id, list_id)
1314                 un->semadj[semnum] = 0;
1315 
1316         curr->semval = val;
1317         curr->sempid = task_tgid_vnr(current);
1318         sma->sem_ctime = get_seconds();
1319         /* maybe some queued-up processes were waiting for this */
1320         do_smart_update(sma, NULL, 0, 0, &wake_q);
1321         sem_unlock(sma, -1);
1322         rcu_read_unlock();
1323         wake_up_q(&wake_q);
1324         return 0;
1325 }
1326 
1327 static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1328                 int cmd, void __user *p)
1329 {
1330         struct sem_array *sma;
1331         struct sem *curr;
1332         int err, nsems;
1333         ushort fast_sem_io[SEMMSL_FAST];
1334         ushort *sem_io = fast_sem_io;
1335         DEFINE_WAKE_Q(wake_q);
1336 
1337         rcu_read_lock();
1338         sma = sem_obtain_object_check(ns, semid);
1339         if (IS_ERR(sma)) {
1340                 rcu_read_unlock();
1341                 return PTR_ERR(sma);
1342         }
1343 
1344         nsems = sma->sem_nsems;
1345 
1346         err = -EACCES;
1347         if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1348                 goto out_rcu_wakeup;
1349 
1350         err = security_sem_semctl(sma, cmd);
1351         if (err)
1352                 goto out_rcu_wakeup;
1353 
1354         err = -EACCES;
1355         switch (cmd) {
1356         case GETALL:
1357         {
1358                 ushort __user *array = p;
1359                 int i;
1360 
1361                 sem_lock(sma, NULL, -1);
1362                 if (!ipc_valid_object(&sma->sem_perm)) {
1363                         err = -EIDRM;
1364                         goto out_unlock;
1365                 }
1366                 if (nsems > SEMMSL_FAST) {
1367                         if (!ipc_rcu_getref(sma)) {
1368                                 err = -EIDRM;
1369                                 goto out_unlock;
1370                         }
1371                         sem_unlock(sma, -1);
1372                         rcu_read_unlock();
1373                         sem_io = ipc_alloc(sizeof(ushort)*nsems);
1374                         if (sem_io == NULL) {
1375                                 ipc_rcu_putref(sma, sem_rcu_free);
1376                                 return -ENOMEM;
1377                         }
1378 
1379                         rcu_read_lock();
1380                         sem_lock_and_putref(sma);
1381                         if (!ipc_valid_object(&sma->sem_perm)) {
1382                                 err = -EIDRM;
1383                                 goto out_unlock;
1384                         }
1385                 }
1386                 for (i = 0; i < sma->sem_nsems; i++)
1387                         sem_io[i] = sma->sem_base[i].semval;
1388                 sem_unlock(sma, -1);
1389                 rcu_read_unlock();
1390                 err = 0;
1391                 if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1392                         err = -EFAULT;
1393                 goto out_free;
1394         }
1395         case SETALL:
1396         {
1397                 int i;
1398                 struct sem_undo *un;
1399 
1400                 if (!ipc_rcu_getref(sma)) {
1401                         err = -EIDRM;
1402                         goto out_rcu_wakeup;
1403                 }
1404                 rcu_read_unlock();
1405 
1406                 if (nsems > SEMMSL_FAST) {
1407                         sem_io = ipc_alloc(sizeof(ushort)*nsems);
1408                         if (sem_io == NULL) {
1409                                 ipc_rcu_putref(sma, sem_rcu_free);
1410                                 return -ENOMEM;
1411                         }
1412                 }
1413 
1414                 if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1415                         ipc_rcu_putref(sma, sem_rcu_free);
1416                         err = -EFAULT;
1417                         goto out_free;
1418                 }
1419 
1420                 for (i = 0; i < nsems; i++) {
1421                         if (sem_io[i] > SEMVMX) {
1422                                 ipc_rcu_putref(sma, sem_rcu_free);
1423                                 err = -ERANGE;
1424                                 goto out_free;
1425                         }
1426                 }
1427                 rcu_read_lock();
1428                 sem_lock_and_putref(sma);
1429                 if (!ipc_valid_object(&sma->sem_perm)) {
1430                         err = -EIDRM;
1431                         goto out_unlock;
1432                 }
1433 
1434                 for (i = 0; i < nsems; i++) {
1435                         sma->sem_base[i].semval = sem_io[i];
1436                         sma->sem_base[i].sempid = task_tgid_vnr(current);
1437                 }
1438 
1439                 ipc_assert_locked_object(&sma->sem_perm);
1440                 list_for_each_entry(un, &sma->list_id, list_id) {
1441                         for (i = 0; i < nsems; i++)
1442                                 un->semadj[i] = 0;
1443                 }
1444                 sma->sem_ctime = get_seconds();
1445                 /* maybe some queued-up processes were waiting for this */
1446                 do_smart_update(sma, NULL, 0, 0, &wake_q);
1447                 err = 0;
1448                 goto out_unlock;
1449         }
1450         /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1451         }
1452         err = -EINVAL;
1453         if (semnum < 0 || semnum >= nsems)
1454                 goto out_rcu_wakeup;
1455 
1456         sem_lock(sma, NULL, -1);
1457         if (!ipc_valid_object(&sma->sem_perm)) {
1458                 err = -EIDRM;
1459                 goto out_unlock;
1460         }
1461         curr = &sma->sem_base[semnum];
1462 
1463         switch (cmd) {
1464         case GETVAL:
1465                 err = curr->semval;
1466                 goto out_unlock;
1467         case GETPID:
1468                 err = curr->sempid;
1469                 goto out_unlock;
1470         case GETNCNT:
1471                 err = count_semcnt(sma, semnum, 0);
1472                 goto out_unlock;
1473         case GETZCNT:
1474                 err = count_semcnt(sma, semnum, 1);
1475                 goto out_unlock;
1476         }
1477 
1478 out_unlock:
1479         sem_unlock(sma, -1);
1480 out_rcu_wakeup:
1481         rcu_read_unlock();
1482         wake_up_q(&wake_q);
1483 out_free:
1484         if (sem_io != fast_sem_io)
1485                 ipc_free(sem_io);
1486         return err;
1487 }
1488 
1489 static inline unsigned long
1490 copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1491 {
1492         switch (version) {
1493         case IPC_64:
1494                 if (copy_from_user(out, buf, sizeof(*out)))
1495                         return -EFAULT;
1496                 return 0;
1497         case IPC_OLD:
1498             {
1499                 struct semid_ds tbuf_old;
1500 
1501                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1502                         return -EFAULT;
1503 
1504                 out->sem_perm.uid       = tbuf_old.sem_perm.uid;
1505                 out->sem_perm.gid       = tbuf_old.sem_perm.gid;
1506                 out->sem_perm.mode      = tbuf_old.sem_perm.mode;
1507 
1508                 return 0;
1509             }
1510         default:
1511                 return -EINVAL;
1512         }
1513 }
1514 
1515 /*
1516  * This function handles some semctl commands which require the rwsem
1517  * to be held in write mode.
1518  * NOTE: no locks must be held, the rwsem is taken inside this function.
1519  */
1520 static int semctl_down(struct ipc_namespace *ns, int semid,
1521                        int cmd, int version, void __user *p)
1522 {
1523         struct sem_array *sma;
1524         int err;
1525         struct semid64_ds semid64;
1526         struct kern_ipc_perm *ipcp;
1527 
1528         if (cmd == IPC_SET) {
1529                 if (copy_semid_from_user(&semid64, p, version))
1530                         return -EFAULT;
1531         }
1532 
1533         down_write(&sem_ids(ns).rwsem);
1534         rcu_read_lock();
1535 
1536         ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1537                                       &semid64.sem_perm, 0);
1538         if (IS_ERR(ipcp)) {
1539                 err = PTR_ERR(ipcp);
1540                 goto out_unlock1;
1541         }
1542 
1543         sma = container_of(ipcp, struct sem_array, sem_perm);
1544 
1545         err = security_sem_semctl(sma, cmd);
1546         if (err)
1547                 goto out_unlock1;
1548 
1549         switch (cmd) {
1550         case IPC_RMID:
1551                 sem_lock(sma, NULL, -1);
1552                 /* freeary unlocks the ipc object and rcu */
1553                 freeary(ns, ipcp);
1554                 goto out_up;
1555         case IPC_SET:
1556                 sem_lock(sma, NULL, -1);
1557                 err = ipc_update_perm(&semid64.sem_perm, ipcp);
1558                 if (err)
1559                         goto out_unlock0;
1560                 sma->sem_ctime = get_seconds();
1561                 break;
1562         default:
1563                 err = -EINVAL;
1564                 goto out_unlock1;
1565         }
1566 
1567 out_unlock0:
1568         sem_unlock(sma, -1);
1569 out_unlock1:
1570         rcu_read_unlock();
1571 out_up:
1572         up_write(&sem_ids(ns).rwsem);
1573         return err;
1574 }
1575 
1576 SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1577 {
1578         int version;
1579         struct ipc_namespace *ns;
1580         void __user *p = (void __user *)arg;
1581 
1582         if (semid < 0)
1583                 return -EINVAL;
1584 
1585         version = ipc_parse_version(&cmd);
1586         ns = current->nsproxy->ipc_ns;
1587 
1588         switch (cmd) {
1589         case IPC_INFO:
1590         case SEM_INFO:
1591         case IPC_STAT:
1592         case SEM_STAT:
1593                 return semctl_nolock(ns, semid, cmd, version, p);
1594         case GETALL:
1595         case GETVAL:
1596         case GETPID:
1597         case GETNCNT:
1598         case GETZCNT:
1599         case SETALL:
1600                 return semctl_main(ns, semid, semnum, cmd, p);
1601         case SETVAL:
1602                 return semctl_setval(ns, semid, semnum, arg);
1603         case IPC_RMID:
1604         case IPC_SET:
1605                 return semctl_down(ns, semid, cmd, version, p);
1606         default:
1607                 return -EINVAL;
1608         }
1609 }
1610 
1611 /* If the task doesn't already have a undo_list, then allocate one
1612  * here.  We guarantee there is only one thread using this undo list,
1613  * and current is THE ONE
1614  *
1615  * If this allocation and assignment succeeds, but later
1616  * portions of this code fail, there is no need to free the sem_undo_list.
1617  * Just let it stay associated with the task, and it'll be freed later
1618  * at exit time.
1619  *
1620  * This can block, so callers must hold no locks.
1621  */
1622 static inline int get_undo_list(struct sem_undo_list **undo_listp)
1623 {
1624         struct sem_undo_list *undo_list;
1625 
1626         undo_list = current->sysvsem.undo_list;
1627         if (!undo_list) {
1628                 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1629                 if (undo_list == NULL)
1630                         return -ENOMEM;
1631                 spin_lock_init(&undo_list->lock);
1632                 atomic_set(&undo_list->refcnt, 1);
1633                 INIT_LIST_HEAD(&undo_list->list_proc);
1634 
1635                 current->sysvsem.undo_list = undo_list;
1636         }
1637         *undo_listp = undo_list;
1638         return 0;
1639 }
1640 
1641 static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1642 {
1643         struct sem_undo *un;
1644 
1645         list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1646                 if (un->semid == semid)
1647                         return un;
1648         }
1649         return NULL;
1650 }
1651 
1652 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1653 {
1654         struct sem_undo *un;
1655 
1656         assert_spin_locked(&ulp->lock);
1657 
1658         un = __lookup_undo(ulp, semid);
1659         if (un) {
1660                 list_del_rcu(&un->list_proc);
1661                 list_add_rcu(&un->list_proc, &ulp->list_proc);
1662         }
1663         return un;
1664 }
1665 
1666 /**
1667  * find_alloc_undo - lookup (and if not present create) undo array
1668  * @ns: namespace
1669  * @semid: semaphore array id
1670  *
1671  * The function looks up (and if not present creates) the undo structure.
1672  * The size of the undo structure depends on the size of the semaphore
1673  * array, thus the alloc path is not that straightforward.
1674  * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1675  * performs a rcu_read_lock().
1676  */
1677 static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1678 {
1679         struct sem_array *sma;
1680         struct sem_undo_list *ulp;
1681         struct sem_undo *un, *new;
1682         int nsems, error;
1683 
1684         error = get_undo_list(&ulp);
1685         if (error)
1686                 return ERR_PTR(error);
1687 
1688         rcu_read_lock();
1689         spin_lock(&ulp->lock);
1690         un = lookup_undo(ulp, semid);
1691         spin_unlock(&ulp->lock);
1692         if (likely(un != NULL))
1693                 goto out;
1694 
1695         /* no undo structure around - allocate one. */
1696         /* step 1: figure out the size of the semaphore array */
1697         sma = sem_obtain_object_check(ns, semid);
1698         if (IS_ERR(sma)) {
1699                 rcu_read_unlock();
1700                 return ERR_CAST(sma);
1701         }
1702 
1703         nsems = sma->sem_nsems;
1704         if (!ipc_rcu_getref(sma)) {
1705                 rcu_read_unlock();
1706                 un = ERR_PTR(-EIDRM);
1707                 goto out;
1708         }
1709         rcu_read_unlock();
1710 
1711         /* step 2: allocate new undo structure */
1712         new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1713         if (!new) {
1714                 ipc_rcu_putref(sma, sem_rcu_free);
1715                 return ERR_PTR(-ENOMEM);
1716         }
1717 
1718         /* step 3: Acquire the lock on semaphore array */
1719         rcu_read_lock();
1720         sem_lock_and_putref(sma);
1721         if (!ipc_valid_object(&sma->sem_perm)) {
1722                 sem_unlock(sma, -1);
1723                 rcu_read_unlock();
1724                 kfree(new);
1725                 un = ERR_PTR(-EIDRM);
1726                 goto out;
1727         }
1728         spin_lock(&ulp->lock);
1729 
1730         /*
1731          * step 4: check for races: did someone else allocate the undo struct?
1732          */
1733         un = lookup_undo(ulp, semid);
1734         if (un) {
1735                 kfree(new);
1736                 goto success;
1737         }
1738         /* step 5: initialize & link new undo structure */
1739         new->semadj = (short *) &new[1];
1740         new->ulp = ulp;
1741         new->semid = semid;
1742         assert_spin_locked(&ulp->lock);
1743         list_add_rcu(&new->list_proc, &ulp->list_proc);
1744         ipc_assert_locked_object(&sma->sem_perm);
1745         list_add(&new->list_id, &sma->list_id);
1746         un = new;
1747 
1748 success:
1749         spin_unlock(&ulp->lock);
1750         sem_unlock(sma, -1);
1751 out:
1752         return un;
1753 }
1754 
1755 SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1756                 unsigned, nsops, const struct timespec __user *, timeout)
1757 {
1758         int error = -EINVAL;
1759         struct sem_array *sma;
1760         struct sembuf fast_sops[SEMOPM_FAST];
1761         struct sembuf *sops = fast_sops, *sop;
1762         struct sem_undo *un;
1763         int max, locknum;
1764         bool undos = false, alter = false, dupsop = false;
1765         struct sem_queue queue;
1766         unsigned long dup = 0, jiffies_left = 0;
1767         struct ipc_namespace *ns;
1768 
1769         ns = current->nsproxy->ipc_ns;
1770 
1771         if (nsops < 1 || semid < 0)
1772                 return -EINVAL;
1773         if (nsops > ns->sc_semopm)
1774                 return -E2BIG;
1775         if (nsops > SEMOPM_FAST) {
1776                 sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
1777                 if (sops == NULL)
1778                         return -ENOMEM;
1779         }
1780 
1781         if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
1782                 error =  -EFAULT;
1783                 goto out_free;
1784         }
1785 
1786         if (timeout) {
1787                 struct timespec _timeout;
1788                 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1789                         error = -EFAULT;
1790                         goto out_free;
1791                 }
1792                 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1793                         _timeout.tv_nsec >= 1000000000L) {
1794                         error = -EINVAL;
1795                         goto out_free;
1796                 }
1797                 jiffies_left = timespec_to_jiffies(&_timeout);
1798         }
1799 
1800         max = 0;
1801         for (sop = sops; sop < sops + nsops; sop++) {
1802                 unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
1803 
1804                 if (sop->sem_num >= max)
1805                         max = sop->sem_num;
1806                 if (sop->sem_flg & SEM_UNDO)
1807                         undos = true;
1808                 if (dup & mask) {
1809                         /*
1810                          * There was a previous alter access that appears
1811                          * to have accessed the same semaphore, thus use
1812                          * the dupsop logic. "appears", because the detection
1813                          * can only check % BITS_PER_LONG.
1814                          */
1815                         dupsop = true;
1816                 }
1817                 if (sop->sem_op != 0) {
1818                         alter = true;
1819                         dup |= mask;
1820                 }
1821         }
1822 
1823         if (undos) {
1824                 /* On success, find_alloc_undo takes the rcu_read_lock */
1825                 un = find_alloc_undo(ns, semid);
1826                 if (IS_ERR(un)) {
1827                         error = PTR_ERR(un);
1828                         goto out_free;
1829                 }
1830         } else {
1831                 un = NULL;
1832                 rcu_read_lock();
1833         }
1834 
1835         sma = sem_obtain_object_check(ns, semid);
1836         if (IS_ERR(sma)) {
1837                 rcu_read_unlock();
1838                 error = PTR_ERR(sma);
1839                 goto out_free;
1840         }
1841 
1842         error = -EFBIG;
1843         if (max >= sma->sem_nsems) {
1844                 rcu_read_unlock();
1845                 goto out_free;
1846         }
1847 
1848         error = -EACCES;
1849         if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
1850                 rcu_read_unlock();
1851                 goto out_free;
1852         }
1853 
1854         error = security_sem_semop(sma, sops, nsops, alter);
1855         if (error) {
1856                 rcu_read_unlock();
1857                 goto out_free;
1858         }
1859 
1860         error = -EIDRM;
1861         locknum = sem_lock(sma, sops, nsops);
1862         /*
1863          * We eventually might perform the following check in a lockless
1864          * fashion, considering ipc_valid_object() locking constraints.
1865          * If nsops == 1 and there is no contention for sem_perm.lock, then
1866          * only a per-semaphore lock is held and it's OK to proceed with the
1867          * check below. More details on the fine grained locking scheme
1868          * entangled here and why it's RMID race safe on comments at sem_lock()
1869          */
1870         if (!ipc_valid_object(&sma->sem_perm))
1871                 goto out_unlock_free;
1872         /*
1873          * semid identifiers are not unique - find_alloc_undo may have
1874          * allocated an undo structure, it was invalidated by an RMID
1875          * and now a new array with received the same id. Check and fail.
1876          * This case can be detected checking un->semid. The existence of
1877          * "un" itself is guaranteed by rcu.
1878          */
1879         if (un && un->semid == -1)
1880                 goto out_unlock_free;
1881 
1882         queue.sops = sops;
1883         queue.nsops = nsops;
1884         queue.undo = un;
1885         queue.pid = task_tgid_vnr(current);
1886         queue.alter = alter;
1887         queue.dupsop = dupsop;
1888 
1889         error = perform_atomic_semop(sma, &queue);
1890         if (error == 0) { /* non-blocking succesfull path */
1891                 DEFINE_WAKE_Q(wake_q);
1892 
1893                 /*
1894                  * If the operation was successful, then do
1895                  * the required updates.
1896                  */
1897                 if (alter)
1898                         do_smart_update(sma, sops, nsops, 1, &wake_q);
1899                 else
1900                         set_semotime(sma, sops);
1901 
1902                 sem_unlock(sma, locknum);
1903                 rcu_read_unlock();
1904                 wake_up_q(&wake_q);
1905 
1906                 goto out_free;
1907         }
1908         if (error < 0) /* non-blocking error path */
1909                 goto out_unlock_free;
1910 
1911         /*
1912          * We need to sleep on this operation, so we put the current
1913          * task into the pending queue and go to sleep.
1914          */
1915         if (nsops == 1) {
1916                 struct sem *curr;
1917                 curr = &sma->sem_base[sops->sem_num];
1918 
1919                 if (alter) {
1920                         if (sma->complex_count) {
1921                                 list_add_tail(&queue.list,
1922                                                 &sma->pending_alter);
1923                         } else {
1924 
1925                                 list_add_tail(&queue.list,
1926                                                 &curr->pending_alter);
1927                         }
1928                 } else {
1929                         list_add_tail(&queue.list, &curr->pending_const);
1930                 }
1931         } else {
1932                 if (!sma->complex_count)
1933                         merge_queues(sma);
1934 
1935                 if (alter)
1936                         list_add_tail(&queue.list, &sma->pending_alter);
1937                 else
1938                         list_add_tail(&queue.list, &sma->pending_const);
1939 
1940                 sma->complex_count++;
1941         }
1942 
1943         do {
1944                 queue.status = -EINTR;
1945                 queue.sleeper = current;
1946 
1947                 __set_current_state(TASK_INTERRUPTIBLE);
1948                 sem_unlock(sma, locknum);
1949                 rcu_read_unlock();
1950 
1951                 if (timeout)
1952                         jiffies_left = schedule_timeout(jiffies_left);
1953                 else
1954                         schedule();
1955 
1956                 /*
1957                  * fastpath: the semop has completed, either successfully or
1958                  * not, from the syscall pov, is quite irrelevant to us at this
1959                  * point; we're done.
1960                  *
1961                  * We _do_ care, nonetheless, about being awoken by a signal or
1962                  * spuriously.  The queue.status is checked again in the
1963                  * slowpath (aka after taking sem_lock), such that we can detect
1964                  * scenarios where we were awakened externally, during the
1965                  * window between wake_q_add() and wake_up_q().
1966                  */
1967                 error = READ_ONCE(queue.status);
1968                 if (error != -EINTR) {
1969                         /*
1970                          * User space could assume that semop() is a memory
1971                          * barrier: Without the mb(), the cpu could
1972                          * speculatively read in userspace stale data that was
1973                          * overwritten by the previous owner of the semaphore.
1974                          */
1975                         smp_mb();
1976                         goto out_free;
1977                 }
1978 
1979                 rcu_read_lock();
1980                 locknum = sem_lock(sma, sops, nsops);
1981 
1982                 if (!ipc_valid_object(&sma->sem_perm))
1983                         goto out_unlock_free;
1984 
1985                 error = READ_ONCE(queue.status);
1986 
1987                 /*
1988                  * If queue.status != -EINTR we are woken up by another process.
1989                  * Leave without unlink_queue(), but with sem_unlock().
1990                  */
1991                 if (error != -EINTR)
1992                         goto out_unlock_free;
1993 
1994                 /*
1995                  * If an interrupt occurred we have to clean up the queue.
1996                  */
1997                 if (timeout && jiffies_left == 0)
1998                         error = -EAGAIN;
1999         } while (error == -EINTR && !signal_pending(current)); /* spurious */
2000 
2001         unlink_queue(sma, &queue);
2002 
2003 out_unlock_free:
2004         sem_unlock(sma, locknum);
2005         rcu_read_unlock();
2006 out_free:
2007         if (sops != fast_sops)
2008                 kfree(sops);
2009         return error;
2010 }
2011 
2012 SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2013                 unsigned, nsops)
2014 {
2015         return sys_semtimedop(semid, tsops, nsops, NULL);
2016 }
2017 
2018 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2019  * parent and child tasks.
2020  */
2021 
2022 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2023 {
2024         struct sem_undo_list *undo_list;
2025         int error;
2026 
2027         if (clone_flags & CLONE_SYSVSEM) {
2028                 error = get_undo_list(&undo_list);
2029                 if (error)
2030                         return error;
2031                 atomic_inc(&undo_list->refcnt);
2032                 tsk->sysvsem.undo_list = undo_list;
2033         } else
2034                 tsk->sysvsem.undo_list = NULL;
2035 
2036         return 0;
2037 }
2038 
2039 /*
2040  * add semadj values to semaphores, free undo structures.
2041  * undo structures are not freed when semaphore arrays are destroyed
2042  * so some of them may be out of date.
2043  * IMPLEMENTATION NOTE: There is some confusion over whether the
2044  * set of adjustments that needs to be done should be done in an atomic
2045  * manner or not. That is, if we are attempting to decrement the semval
2046  * should we queue up and wait until we can do so legally?
2047  * The original implementation attempted to do this (queue and wait).
2048  * The current implementation does not do so. The POSIX standard
2049  * and SVID should be consulted to determine what behavior is mandated.
2050  */
2051 void exit_sem(struct task_struct *tsk)
2052 {
2053         struct sem_undo_list *ulp;
2054 
2055         ulp = tsk->sysvsem.undo_list;
2056         if (!ulp)
2057                 return;
2058         tsk->sysvsem.undo_list = NULL;
2059 
2060         if (!atomic_dec_and_test(&ulp->refcnt))
2061                 return;
2062 
2063         for (;;) {
2064                 struct sem_array *sma;
2065                 struct sem_undo *un;
2066                 int semid, i;
2067                 DEFINE_WAKE_Q(wake_q);
2068 
2069                 cond_resched();
2070 
2071                 rcu_read_lock();
2072                 un = list_entry_rcu(ulp->list_proc.next,
2073                                     struct sem_undo, list_proc);
2074                 if (&un->list_proc == &ulp->list_proc) {
2075                         /*
2076                          * We must wait for freeary() before freeing this ulp,
2077                          * in case we raced with last sem_undo. There is a small
2078                          * possibility where we exit while freeary() didn't
2079                          * finish unlocking sem_undo_list.
2080                          */
2081                         spin_unlock_wait(&ulp->lock);
2082                         rcu_read_unlock();
2083                         break;
2084                 }
2085                 spin_lock(&ulp->lock);
2086                 semid = un->semid;
2087                 spin_unlock(&ulp->lock);
2088 
2089                 /* exit_sem raced with IPC_RMID, nothing to do */
2090                 if (semid == -1) {
2091                         rcu_read_unlock();
2092                         continue;
2093                 }
2094 
2095                 sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2096                 /* exit_sem raced with IPC_RMID, nothing to do */
2097                 if (IS_ERR(sma)) {
2098                         rcu_read_unlock();
2099                         continue;
2100                 }
2101 
2102                 sem_lock(sma, NULL, -1);
2103                 /* exit_sem raced with IPC_RMID, nothing to do */
2104                 if (!ipc_valid_object(&sma->sem_perm)) {
2105                         sem_unlock(sma, -1);
2106                         rcu_read_unlock();
2107                         continue;
2108                 }
2109                 un = __lookup_undo(ulp, semid);
2110                 if (un == NULL) {
2111                         /* exit_sem raced with IPC_RMID+semget() that created
2112                          * exactly the same semid. Nothing to do.
2113                          */
2114                         sem_unlock(sma, -1);
2115                         rcu_read_unlock();
2116                         continue;
2117                 }
2118 
2119                 /* remove un from the linked lists */
2120                 ipc_assert_locked_object(&sma->sem_perm);
2121                 list_del(&un->list_id);
2122 
2123                 /* we are the last process using this ulp, acquiring ulp->lock
2124                  * isn't required. Besides that, we are also protected against
2125                  * IPC_RMID as we hold sma->sem_perm lock now
2126                  */
2127                 list_del_rcu(&un->list_proc);
2128 
2129                 /* perform adjustments registered in un */
2130                 for (i = 0; i < sma->sem_nsems; i++) {
2131                         struct sem *semaphore = &sma->sem_base[i];
2132                         if (un->semadj[i]) {
2133                                 semaphore->semval += un->semadj[i];
2134                                 /*
2135                                  * Range checks of the new semaphore value,
2136                                  * not defined by sus:
2137                                  * - Some unices ignore the undo entirely
2138                                  *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2139                                  * - some cap the value (e.g. FreeBSD caps
2140                                  *   at 0, but doesn't enforce SEMVMX)
2141                                  *
2142                                  * Linux caps the semaphore value, both at 0
2143                                  * and at SEMVMX.
2144                                  *
2145                                  *      Manfred <manfred@colorfullife.com>
2146                                  */
2147                                 if (semaphore->semval < 0)
2148                                         semaphore->semval = 0;
2149                                 if (semaphore->semval > SEMVMX)
2150                                         semaphore->semval = SEMVMX;
2151                                 semaphore->sempid = task_tgid_vnr(current);
2152                         }
2153                 }
2154                 /* maybe some queued-up processes were waiting for this */
2155                 do_smart_update(sma, NULL, 0, 1, &wake_q);
2156                 sem_unlock(sma, -1);
2157                 rcu_read_unlock();
2158                 wake_up_q(&wake_q);
2159 
2160                 kfree_rcu(un, rcu);
2161         }
2162         kfree(ulp);
2163 }
2164 
2165 #ifdef CONFIG_PROC_FS
2166 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2167 {
2168         struct user_namespace *user_ns = seq_user_ns(s);
2169         struct sem_array *sma = it;
2170         time_t sem_otime;
2171 
2172         /*
2173          * The proc interface isn't aware of sem_lock(), it calls
2174          * ipc_lock_object() directly (in sysvipc_find_ipc).
2175          * In order to stay compatible with sem_lock(), we must
2176          * enter / leave complex_mode.
2177          */
2178         complexmode_enter(sma);
2179 
2180         sem_otime = get_semotime(sma);
2181 
2182         seq_printf(s,
2183                    "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2184                    sma->sem_perm.key,
2185                    sma->sem_perm.id,
2186                    sma->sem_perm.mode,
2187                    sma->sem_nsems,
2188                    from_kuid_munged(user_ns, sma->sem_perm.uid),
2189                    from_kgid_munged(user_ns, sma->sem_perm.gid),
2190                    from_kuid_munged(user_ns, sma->sem_perm.cuid),
2191                    from_kgid_munged(user_ns, sma->sem_perm.cgid),
2192                    sem_otime,
2193                    sma->sem_ctime);
2194 
2195         complexmode_tryleave(sma);
2196 
2197         return 0;
2198 }
2199 #endif
2200 

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