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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  * Further wakeup optimizations, documentation
 15  * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
 16  *
 17  * support for audit of ipc object properties and permission changes
 18  * Dustin Kirkland <dustin.kirkland@us.ibm.com>
 19  *
 20  * namespaces support
 21  * OpenVZ, SWsoft Inc.
 22  * Pavel Emelianov <xemul@openvz.org>
 23  *
 24  * Implementation notes: (May 2010)
 25  * This file implements System V semaphores.
 26  *
 27  * User space visible behavior:
 28  * - FIFO ordering for semop() operations (just FIFO, not starvation
 29  *   protection)
 30  * - multiple semaphore operations that alter the same semaphore in
 31  *   one semop() are handled.
 32  * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
 33  *   SETALL calls.
 34  * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
 35  * - undo adjustments at process exit are limited to 0..SEMVMX.
 36  * - namespace are supported.
 37  * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtine by writing
 38  *   to /proc/sys/kernel/sem.
 39  * - statistics about the usage are reported in /proc/sysvipc/sem.
 40  *
 41  * Internals:
 42  * - scalability:
 43  *   - all global variables are read-mostly.
 44  *   - semop() calls and semctl(RMID) are synchronized by RCU.
 45  *   - most operations do write operations (actually: spin_lock calls) to
 46  *     the per-semaphore array structure.
 47  *   Thus: Perfect SMP scaling between independent semaphore arrays.
 48  *         If multiple semaphores in one array are used, then cache line
 49  *         trashing on the semaphore array spinlock will limit the scaling.
 50  * - semncnt and semzcnt are calculated on demand in count_semcnt()
 51  * - the task that performs a successful semop() scans the list of all
 52  *   sleeping tasks and completes any pending operations that can be fulfilled.
 53  *   Semaphores are actively given to waiting tasks (necessary for FIFO).
 54  *   (see update_queue())
 55  * - To improve the scalability, the actual wake-up calls are performed after
 56  *   dropping all locks. (see wake_up_sem_queue_prepare(),
 57  *   wake_up_sem_queue_do())
 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  * - The synchronizations between wake-ups due to a timeout/signal and a
 63  *   wake-up due to a completed semaphore operation is achieved by using an
 64  *   intermediate state (IN_WAKEUP).
 65  * - UNDO values are stored in an array (one per process and per
 66  *   semaphore array, lazily allocated). For backwards compatibility, multiple
 67  *   modes for the UNDO variables are supported (per process, per thread)
 68  *   (see copy_semundo, CLONE_SYSVSEM)
 69  * - There are two lists of the pending operations: a per-array list
 70  *   and per-semaphore list (stored in the array). This allows to achieve FIFO
 71  *   ordering without always scanning all pending operations.
 72  *   The worst-case behavior is nevertheless O(N^2) for N wakeups.
 73  */
 74 
 75 #include <linux/slab.h>
 76 #include <linux/spinlock.h>
 77 #include <linux/init.h>
 78 #include <linux/proc_fs.h>
 79 #include <linux/time.h>
 80 #include <linux/security.h>
 81 #include <linux/syscalls.h>
 82 #include <linux/audit.h>
 83 #include <linux/capability.h>
 84 #include <linux/seq_file.h>
 85 #include <linux/rwsem.h>
 86 #include <linux/nsproxy.h>
 87 #include <linux/ipc_namespace.h>
 88 
 89 #include <linux/uaccess.h>
 90 #include "util.h"
 91 
 92 /* One semaphore structure for each semaphore in the system. */
 93 struct sem {
 94         int     semval;         /* current value */
 95         int     sempid;         /* pid of last operation */
 96         spinlock_t      lock;   /* spinlock for fine-grained semtimedop */
 97         struct list_head pending_alter; /* pending single-sop operations */
 98                                         /* that alter the semaphore */
 99         struct list_head pending_const; /* pending single-sop operations */
100                                         /* that do not alter the semaphore*/
101         time_t  sem_otime;      /* candidate for sem_otime */
102 } ____cacheline_aligned_in_smp;
103 
104 /* One queue for each sleeping process in the system. */
105 struct sem_queue {
106         struct list_head        list;    /* queue of pending operations */
107         struct task_struct      *sleeper; /* this process */
108         struct sem_undo         *undo;   /* undo structure */
109         int                     pid;     /* process id of requesting process */
110         int                     status;  /* completion status of operation */
111         struct sembuf           *sops;   /* array of pending operations */
112         struct sembuf           *blocking; /* the operation that blocked */
113         int                     nsops;   /* number of operations */
114         int                     alter;   /* does *sops alter the array? */
115 };
116 
117 /* Each task has a list of undo requests. They are executed automatically
118  * when the process exits.
119  */
120 struct sem_undo {
121         struct list_head        list_proc;      /* per-process list: *
122                                                  * all undos from one process
123                                                  * rcu protected */
124         struct rcu_head         rcu;            /* rcu struct for sem_undo */
125         struct sem_undo_list    *ulp;           /* back ptr to sem_undo_list */
126         struct list_head        list_id;        /* per semaphore array list:
127                                                  * all undos for one array */
128         int                     semid;          /* semaphore set identifier */
129         short                   *semadj;        /* array of adjustments */
130                                                 /* one per semaphore */
131 };
132 
133 /* sem_undo_list controls shared access to the list of sem_undo structures
134  * that may be shared among all a CLONE_SYSVSEM task group.
135  */
136 struct sem_undo_list {
137         atomic_t                refcnt;
138         spinlock_t              lock;
139         struct list_head        list_proc;
140 };
141 
142 
143 #define sem_ids(ns)     ((ns)->ids[IPC_SEM_IDS])
144 
145 #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
146 
147 static int newary(struct ipc_namespace *, struct ipc_params *);
148 static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
149 #ifdef CONFIG_PROC_FS
150 static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
151 #endif
152 
153 #define SEMMSL_FAST     256 /* 512 bytes on stack */
154 #define SEMOPM_FAST     64  /* ~ 372 bytes on stack */
155 
156 /*
157  * Locking:
158  *      sem_undo.id_next,
159  *      sem_array.complex_count,
160  *      sem_array.pending{_alter,_cont},
161  *      sem_array.sem_undo: global sem_lock() for read/write
162  *      sem_undo.proc_next: only "current" is allowed to read/write that field.
163  *
164  *      sem_array.sem_base[i].pending_{const,alter}:
165  *              global or semaphore sem_lock() for read/write
166  */
167 
168 #define sc_semmsl       sem_ctls[0]
169 #define sc_semmns       sem_ctls[1]
170 #define sc_semopm       sem_ctls[2]
171 #define sc_semmni       sem_ctls[3]
172 
173 void sem_init_ns(struct ipc_namespace *ns)
174 {
175         ns->sc_semmsl = SEMMSL;
176         ns->sc_semmns = SEMMNS;
177         ns->sc_semopm = SEMOPM;
178         ns->sc_semmni = SEMMNI;
179         ns->used_sems = 0;
180         ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
181 }
182 
183 #ifdef CONFIG_IPC_NS
184 void sem_exit_ns(struct ipc_namespace *ns)
185 {
186         free_ipcs(ns, &sem_ids(ns), freeary);
187         idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
188 }
189 #endif
190 
191 void __init sem_init(void)
192 {
193         sem_init_ns(&init_ipc_ns);
194         ipc_init_proc_interface("sysvipc/sem",
195                                 "       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
196                                 IPC_SEM_IDS, sysvipc_sem_proc_show);
197 }
198 
199 /**
200  * unmerge_queues - unmerge queues, if possible.
201  * @sma: semaphore array
202  *
203  * The function unmerges the wait queues if complex_count is 0.
204  * It must be called prior to dropping the global semaphore array lock.
205  */
206 static void unmerge_queues(struct sem_array *sma)
207 {
208         struct sem_queue *q, *tq;
209 
210         /* complex operations still around? */
211         if (sma->complex_count)
212                 return;
213         /*
214          * We will switch back to simple mode.
215          * Move all pending operation back into the per-semaphore
216          * queues.
217          */
218         list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
219                 struct sem *curr;
220                 curr = &sma->sem_base[q->sops[0].sem_num];
221 
222                 list_add_tail(&q->list, &curr->pending_alter);
223         }
224         INIT_LIST_HEAD(&sma->pending_alter);
225 }
226 
227 /**
228  * merge_queues - merge single semop queues into global queue
229  * @sma: semaphore array
230  *
231  * This function merges all per-semaphore queues into the global queue.
232  * It is necessary to achieve FIFO ordering for the pending single-sop
233  * operations when a multi-semop operation must sleep.
234  * Only the alter operations must be moved, the const operations can stay.
235  */
236 static void merge_queues(struct sem_array *sma)
237 {
238         int i;
239         for (i = 0; i < sma->sem_nsems; i++) {
240                 struct sem *sem = sma->sem_base + i;
241 
242                 list_splice_init(&sem->pending_alter, &sma->pending_alter);
243         }
244 }
245 
246 static void sem_rcu_free(struct rcu_head *head)
247 {
248         struct ipc_rcu *p = container_of(head, struct ipc_rcu, rcu);
249         struct sem_array *sma = ipc_rcu_to_struct(p);
250 
251         security_sem_free(sma);
252         ipc_rcu_free(head);
253 }
254 
255 /*
256  * Wait until all currently ongoing simple ops have completed.
257  * Caller must own sem_perm.lock.
258  * New simple ops cannot start, because simple ops first check
259  * that sem_perm.lock is free.
260  * that a) sem_perm.lock is free and b) complex_count is 0.
261  */
262 static void sem_wait_array(struct sem_array *sma)
263 {
264         int i;
265         struct sem *sem;
266 
267         if (sma->complex_count)  {
268                 /* The thread that increased sma->complex_count waited on
269                  * all sem->lock locks. Thus we don't need to wait again.
270                  */
271                 return;
272         }
273 
274         for (i = 0; i < sma->sem_nsems; i++) {
275                 sem = sma->sem_base + i;
276                 spin_unlock_wait(&sem->lock);
277         }
278 }
279 
280 /*
281  * If the request contains only one semaphore operation, and there are
282  * no complex transactions pending, lock only the semaphore involved.
283  * Otherwise, lock the entire semaphore array, since we either have
284  * multiple semaphores in our own semops, or we need to look at
285  * semaphores from other pending complex operations.
286  */
287 static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
288                               int nsops)
289 {
290         struct sem *sem;
291 
292         if (nsops != 1) {
293                 /* Complex operation - acquire a full lock */
294                 ipc_lock_object(&sma->sem_perm);
295 
296                 /* And wait until all simple ops that are processed
297                  * right now have dropped their locks.
298                  */
299                 sem_wait_array(sma);
300                 return -1;
301         }
302 
303         /*
304          * Only one semaphore affected - try to optimize locking.
305          * The rules are:
306          * - optimized locking is possible if no complex operation
307          *   is either enqueued or processed right now.
308          * - The test for enqueued complex ops is simple:
309          *      sma->complex_count != 0
310          * - Testing for complex ops that are processed right now is
311          *   a bit more difficult. Complex ops acquire the full lock
312          *   and first wait that the running simple ops have completed.
313          *   (see above)
314          *   Thus: If we own a simple lock and the global lock is free
315          *      and complex_count is now 0, then it will stay 0 and
316          *      thus just locking sem->lock is sufficient.
317          */
318         sem = sma->sem_base + sops->sem_num;
319 
320         if (sma->complex_count == 0) {
321                 /*
322                  * It appears that no complex operation is around.
323                  * Acquire the per-semaphore lock.
324                  */
325                 spin_lock(&sem->lock);
326 
327                 /* Then check that the global lock is free */
328                 if (!spin_is_locked(&sma->sem_perm.lock)) {
329                         /* spin_is_locked() is not a memory barrier */
330                         smp_mb();
331 
332                         /* Now repeat the test of complex_count:
333                          * It can't change anymore until we drop sem->lock.
334                          * Thus: if is now 0, then it will stay 0.
335                          */
336                         if (sma->complex_count == 0) {
337                                 /* fast path successful! */
338                                 return sops->sem_num;
339                         }
340                 }
341                 spin_unlock(&sem->lock);
342         }
343 
344         /* slow path: acquire the full lock */
345         ipc_lock_object(&sma->sem_perm);
346 
347         if (sma->complex_count == 0) {
348                 /* False alarm:
349                  * There is no complex operation, thus we can switch
350                  * back to the fast path.
351                  */
352                 spin_lock(&sem->lock);
353                 ipc_unlock_object(&sma->sem_perm);
354                 return sops->sem_num;
355         } else {
356                 /* Not a false alarm, thus complete the sequence for a
357                  * full lock.
358                  */
359                 sem_wait_array(sma);
360                 return -1;
361         }
362 }
363 
364 static inline void sem_unlock(struct sem_array *sma, int locknum)
365 {
366         if (locknum == -1) {
367                 unmerge_queues(sma);
368                 ipc_unlock_object(&sma->sem_perm);
369         } else {
370                 struct sem *sem = sma->sem_base + locknum;
371                 spin_unlock(&sem->lock);
372         }
373 }
374 
375 /*
376  * sem_lock_(check_) routines are called in the paths where the rwsem
377  * is not held.
378  *
379  * The caller holds the RCU read lock.
380  */
381 static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
382                         int id, struct sembuf *sops, int nsops, int *locknum)
383 {
384         struct kern_ipc_perm *ipcp;
385         struct sem_array *sma;
386 
387         ipcp = ipc_obtain_object(&sem_ids(ns), id);
388         if (IS_ERR(ipcp))
389                 return ERR_CAST(ipcp);
390 
391         sma = container_of(ipcp, struct sem_array, sem_perm);
392         *locknum = sem_lock(sma, sops, nsops);
393 
394         /* ipc_rmid() may have already freed the ID while sem_lock
395          * was spinning: verify that the structure is still valid
396          */
397         if (ipc_valid_object(ipcp))
398                 return container_of(ipcp, struct sem_array, sem_perm);
399 
400         sem_unlock(sma, *locknum);
401         return ERR_PTR(-EINVAL);
402 }
403 
404 static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
405 {
406         struct kern_ipc_perm *ipcp = ipc_obtain_object(&sem_ids(ns), id);
407 
408         if (IS_ERR(ipcp))
409                 return ERR_CAST(ipcp);
410 
411         return container_of(ipcp, struct sem_array, sem_perm);
412 }
413 
414 static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
415                                                         int id)
416 {
417         struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
418 
419         if (IS_ERR(ipcp))
420                 return ERR_CAST(ipcp);
421 
422         return container_of(ipcp, struct sem_array, sem_perm);
423 }
424 
425 static inline void sem_lock_and_putref(struct sem_array *sma)
426 {
427         sem_lock(sma, NULL, -1);
428         ipc_rcu_putref(sma, ipc_rcu_free);
429 }
430 
431 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
432 {
433         ipc_rmid(&sem_ids(ns), &s->sem_perm);
434 }
435 
436 /*
437  * Lockless wakeup algorithm:
438  * Without the check/retry algorithm a lockless wakeup is possible:
439  * - queue.status is initialized to -EINTR before blocking.
440  * - wakeup is performed by
441  *      * unlinking the queue entry from the pending list
442  *      * setting queue.status to IN_WAKEUP
443  *        This is the notification for the blocked thread that a
444  *        result value is imminent.
445  *      * call wake_up_process
446  *      * set queue.status to the final value.
447  * - the previously blocked thread checks queue.status:
448  *      * if it's IN_WAKEUP, then it must wait until the value changes
449  *      * if it's not -EINTR, then the operation was completed by
450  *        update_queue. semtimedop can return queue.status without
451  *        performing any operation on the sem array.
452  *      * otherwise it must acquire the spinlock and check what's up.
453  *
454  * The two-stage algorithm is necessary to protect against the following
455  * races:
456  * - if queue.status is set after wake_up_process, then the woken up idle
457  *   thread could race forward and try (and fail) to acquire sma->lock
458  *   before update_queue had a chance to set queue.status
459  * - if queue.status is written before wake_up_process and if the
460  *   blocked process is woken up by a signal between writing
461  *   queue.status and the wake_up_process, then the woken up
462  *   process could return from semtimedop and die by calling
463  *   sys_exit before wake_up_process is called. Then wake_up_process
464  *   will oops, because the task structure is already invalid.
465  *   (yes, this happened on s390 with sysv msg).
466  *
467  */
468 #define IN_WAKEUP       1
469 
470 /**
471  * newary - Create a new semaphore set
472  * @ns: namespace
473  * @params: ptr to the structure that contains key, semflg and nsems
474  *
475  * Called with sem_ids.rwsem held (as a writer)
476  */
477 static int newary(struct ipc_namespace *ns, struct ipc_params *params)
478 {
479         int id;
480         int retval;
481         struct sem_array *sma;
482         int size;
483         key_t key = params->key;
484         int nsems = params->u.nsems;
485         int semflg = params->flg;
486         int i;
487 
488         if (!nsems)
489                 return -EINVAL;
490         if (ns->used_sems + nsems > ns->sc_semmns)
491                 return -ENOSPC;
492 
493         size = sizeof(*sma) + nsems * sizeof(struct sem);
494         sma = ipc_rcu_alloc(size);
495         if (!sma)
496                 return -ENOMEM;
497 
498         memset(sma, 0, size);
499 
500         sma->sem_perm.mode = (semflg & S_IRWXUGO);
501         sma->sem_perm.key = key;
502 
503         sma->sem_perm.security = NULL;
504         retval = security_sem_alloc(sma);
505         if (retval) {
506                 ipc_rcu_putref(sma, ipc_rcu_free);
507                 return retval;
508         }
509 
510         id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
511         if (id < 0) {
512                 ipc_rcu_putref(sma, sem_rcu_free);
513                 return id;
514         }
515         ns->used_sems += nsems;
516 
517         sma->sem_base = (struct sem *) &sma[1];
518 
519         for (i = 0; i < nsems; i++) {
520                 INIT_LIST_HEAD(&sma->sem_base[i].pending_alter);
521                 INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
522                 spin_lock_init(&sma->sem_base[i].lock);
523         }
524 
525         sma->complex_count = 0;
526         INIT_LIST_HEAD(&sma->pending_alter);
527         INIT_LIST_HEAD(&sma->pending_const);
528         INIT_LIST_HEAD(&sma->list_id);
529         sma->sem_nsems = nsems;
530         sma->sem_ctime = get_seconds();
531         sem_unlock(sma, -1);
532         rcu_read_unlock();
533 
534         return sma->sem_perm.id;
535 }
536 
537 
538 /*
539  * Called with sem_ids.rwsem and ipcp locked.
540  */
541 static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
542 {
543         struct sem_array *sma;
544 
545         sma = container_of(ipcp, struct sem_array, sem_perm);
546         return security_sem_associate(sma, semflg);
547 }
548 
549 /*
550  * Called with sem_ids.rwsem and ipcp locked.
551  */
552 static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
553                                 struct ipc_params *params)
554 {
555         struct sem_array *sma;
556 
557         sma = container_of(ipcp, struct sem_array, sem_perm);
558         if (params->u.nsems > sma->sem_nsems)
559                 return -EINVAL;
560 
561         return 0;
562 }
563 
564 SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
565 {
566         struct ipc_namespace *ns;
567         static const struct ipc_ops sem_ops = {
568                 .getnew = newary,
569                 .associate = sem_security,
570                 .more_checks = sem_more_checks,
571         };
572         struct ipc_params sem_params;
573 
574         ns = current->nsproxy->ipc_ns;
575 
576         if (nsems < 0 || nsems > ns->sc_semmsl)
577                 return -EINVAL;
578 
579         sem_params.key = key;
580         sem_params.flg = semflg;
581         sem_params.u.nsems = nsems;
582 
583         return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
584 }
585 
586 /**
587  * perform_atomic_semop - Perform (if possible) a semaphore operation
588  * @sma: semaphore array
589  * @q: struct sem_queue that describes the operation
590  *
591  * Returns 0 if the operation was possible.
592  * Returns 1 if the operation is impossible, the caller must sleep.
593  * Negative values are error codes.
594  */
595 static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
596 {
597         int result, sem_op, nsops, pid;
598         struct sembuf *sop;
599         struct sem *curr;
600         struct sembuf *sops;
601         struct sem_undo *un;
602 
603         sops = q->sops;
604         nsops = q->nsops;
605         un = q->undo;
606 
607         for (sop = sops; sop < sops + nsops; sop++) {
608                 curr = sma->sem_base + sop->sem_num;
609                 sem_op = sop->sem_op;
610                 result = curr->semval;
611 
612                 if (!sem_op && result)
613                         goto would_block;
614 
615                 result += sem_op;
616                 if (result < 0)
617                         goto would_block;
618                 if (result > SEMVMX)
619                         goto out_of_range;
620 
621                 if (sop->sem_flg & SEM_UNDO) {
622                         int undo = un->semadj[sop->sem_num] - sem_op;
623                         /* Exceeding the undo range is an error. */
624                         if (undo < (-SEMAEM - 1) || undo > SEMAEM)
625                                 goto out_of_range;
626                         un->semadj[sop->sem_num] = undo;
627                 }
628 
629                 curr->semval = result;
630         }
631 
632         sop--;
633         pid = q->pid;
634         while (sop >= sops) {
635                 sma->sem_base[sop->sem_num].sempid = pid;
636                 sop--;
637         }
638 
639         return 0;
640 
641 out_of_range:
642         result = -ERANGE;
643         goto undo;
644 
645 would_block:
646         q->blocking = sop;
647 
648         if (sop->sem_flg & IPC_NOWAIT)
649                 result = -EAGAIN;
650         else
651                 result = 1;
652 
653 undo:
654         sop--;
655         while (sop >= sops) {
656                 sem_op = sop->sem_op;
657                 sma->sem_base[sop->sem_num].semval -= sem_op;
658                 if (sop->sem_flg & SEM_UNDO)
659                         un->semadj[sop->sem_num] += sem_op;
660                 sop--;
661         }
662 
663         return result;
664 }
665 
666 /** wake_up_sem_queue_prepare(q, error): Prepare wake-up
667  * @q: queue entry that must be signaled
668  * @error: Error value for the signal
669  *
670  * Prepare the wake-up of the queue entry q.
671  */
672 static void wake_up_sem_queue_prepare(struct list_head *pt,
673                                 struct sem_queue *q, int error)
674 {
675         if (list_empty(pt)) {
676                 /*
677                  * Hold preempt off so that we don't get preempted and have the
678                  * wakee busy-wait until we're scheduled back on.
679                  */
680                 preempt_disable();
681         }
682         q->status = IN_WAKEUP;
683         q->pid = error;
684 
685         list_add_tail(&q->list, pt);
686 }
687 
688 /**
689  * wake_up_sem_queue_do - do the actual wake-up
690  * @pt: list of tasks to be woken up
691  *
692  * Do the actual wake-up.
693  * The function is called without any locks held, thus the semaphore array
694  * could be destroyed already and the tasks can disappear as soon as the
695  * status is set to the actual return code.
696  */
697 static void wake_up_sem_queue_do(struct list_head *pt)
698 {
699         struct sem_queue *q, *t;
700         int did_something;
701 
702         did_something = !list_empty(pt);
703         list_for_each_entry_safe(q, t, pt, list) {
704                 wake_up_process(q->sleeper);
705                 /* q can disappear immediately after writing q->status. */
706                 smp_wmb();
707                 q->status = q->pid;
708         }
709         if (did_something)
710                 preempt_enable();
711 }
712 
713 static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
714 {
715         list_del(&q->list);
716         if (q->nsops > 1)
717                 sma->complex_count--;
718 }
719 
720 /** check_restart(sma, q)
721  * @sma: semaphore array
722  * @q: the operation that just completed
723  *
724  * update_queue is O(N^2) when it restarts scanning the whole queue of
725  * waiting operations. Therefore this function checks if the restart is
726  * really necessary. It is called after a previously waiting operation
727  * modified the array.
728  * Note that wait-for-zero operations are handled without restart.
729  */
730 static int check_restart(struct sem_array *sma, struct sem_queue *q)
731 {
732         /* pending complex alter operations are too difficult to analyse */
733         if (!list_empty(&sma->pending_alter))
734                 return 1;
735 
736         /* we were a sleeping complex operation. Too difficult */
737         if (q->nsops > 1)
738                 return 1;
739 
740         /* It is impossible that someone waits for the new value:
741          * - complex operations always restart.
742          * - wait-for-zero are handled seperately.
743          * - q is a previously sleeping simple operation that
744          *   altered the array. It must be a decrement, because
745          *   simple increments never sleep.
746          * - If there are older (higher priority) decrements
747          *   in the queue, then they have observed the original
748          *   semval value and couldn't proceed. The operation
749          *   decremented to value - thus they won't proceed either.
750          */
751         return 0;
752 }
753 
754 /**
755  * wake_const_ops - wake up non-alter tasks
756  * @sma: semaphore array.
757  * @semnum: semaphore that was modified.
758  * @pt: list head for the tasks that must be woken up.
759  *
760  * wake_const_ops must be called after a semaphore in a semaphore array
761  * was set to 0. If complex const operations are pending, wake_const_ops must
762  * be called with semnum = -1, as well as with the number of each modified
763  * semaphore.
764  * The tasks that must be woken up are added to @pt. The return code
765  * is stored in q->pid.
766  * The function returns 1 if at least one operation was completed successfully.
767  */
768 static int wake_const_ops(struct sem_array *sma, int semnum,
769                                 struct list_head *pt)
770 {
771         struct sem_queue *q;
772         struct list_head *walk;
773         struct list_head *pending_list;
774         int semop_completed = 0;
775 
776         if (semnum == -1)
777                 pending_list = &sma->pending_const;
778         else
779                 pending_list = &sma->sem_base[semnum].pending_const;
780 
781         walk = pending_list->next;
782         while (walk != pending_list) {
783                 int error;
784 
785                 q = container_of(walk, struct sem_queue, list);
786                 walk = walk->next;
787 
788                 error = perform_atomic_semop(sma, q);
789 
790                 if (error <= 0) {
791                         /* operation completed, remove from queue & wakeup */
792 
793                         unlink_queue(sma, q);
794 
795                         wake_up_sem_queue_prepare(pt, q, error);
796                         if (error == 0)
797                                 semop_completed = 1;
798                 }
799         }
800         return semop_completed;
801 }
802 
803 /**
804  * do_smart_wakeup_zero - wakeup all wait for zero tasks
805  * @sma: semaphore array
806  * @sops: operations that were performed
807  * @nsops: number of operations
808  * @pt: list head of the tasks that must be woken up.
809  *
810  * Checks all required queue for wait-for-zero operations, based
811  * on the actual changes that were performed on the semaphore array.
812  * The function returns 1 if at least one operation was completed successfully.
813  */
814 static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
815                                         int nsops, struct list_head *pt)
816 {
817         int i;
818         int semop_completed = 0;
819         int got_zero = 0;
820 
821         /* first: the per-semaphore queues, if known */
822         if (sops) {
823                 for (i = 0; i < nsops; i++) {
824                         int num = sops[i].sem_num;
825 
826                         if (sma->sem_base[num].semval == 0) {
827                                 got_zero = 1;
828                                 semop_completed |= wake_const_ops(sma, num, pt);
829                         }
830                 }
831         } else {
832                 /*
833                  * No sops means modified semaphores not known.
834                  * Assume all were changed.
835                  */
836                 for (i = 0; i < sma->sem_nsems; i++) {
837                         if (sma->sem_base[i].semval == 0) {
838                                 got_zero = 1;
839                                 semop_completed |= wake_const_ops(sma, i, pt);
840                         }
841                 }
842         }
843         /*
844          * If one of the modified semaphores got 0,
845          * then check the global queue, too.
846          */
847         if (got_zero)
848                 semop_completed |= wake_const_ops(sma, -1, pt);
849 
850         return semop_completed;
851 }
852 
853 
854 /**
855  * update_queue - look for tasks that can be completed.
856  * @sma: semaphore array.
857  * @semnum: semaphore that was modified.
858  * @pt: list head for the tasks that must be woken up.
859  *
860  * update_queue must be called after a semaphore in a semaphore array
861  * was modified. If multiple semaphores were modified, update_queue must
862  * be called with semnum = -1, as well as with the number of each modified
863  * semaphore.
864  * The tasks that must be woken up are added to @pt. The return code
865  * is stored in q->pid.
866  * The function internally checks if const operations can now succeed.
867  *
868  * The function return 1 if at least one semop was completed successfully.
869  */
870 static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
871 {
872         struct sem_queue *q;
873         struct list_head *walk;
874         struct list_head *pending_list;
875         int semop_completed = 0;
876 
877         if (semnum == -1)
878                 pending_list = &sma->pending_alter;
879         else
880                 pending_list = &sma->sem_base[semnum].pending_alter;
881 
882 again:
883         walk = pending_list->next;
884         while (walk != pending_list) {
885                 int error, restart;
886 
887                 q = container_of(walk, struct sem_queue, list);
888                 walk = walk->next;
889 
890                 /* If we are scanning the single sop, per-semaphore list of
891                  * one semaphore and that semaphore is 0, then it is not
892                  * necessary to scan further: simple increments
893                  * that affect only one entry succeed immediately and cannot
894                  * be in the  per semaphore pending queue, and decrements
895                  * cannot be successful if the value is already 0.
896                  */
897                 if (semnum != -1 && sma->sem_base[semnum].semval == 0)
898                         break;
899 
900                 error = perform_atomic_semop(sma, q);
901 
902                 /* Does q->sleeper still need to sleep? */
903                 if (error > 0)
904                         continue;
905 
906                 unlink_queue(sma, q);
907 
908                 if (error) {
909                         restart = 0;
910                 } else {
911                         semop_completed = 1;
912                         do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
913                         restart = check_restart(sma, q);
914                 }
915 
916                 wake_up_sem_queue_prepare(pt, q, error);
917                 if (restart)
918                         goto again;
919         }
920         return semop_completed;
921 }
922 
923 /**
924  * set_semotime - set sem_otime
925  * @sma: semaphore array
926  * @sops: operations that modified the array, may be NULL
927  *
928  * sem_otime is replicated to avoid cache line trashing.
929  * This function sets one instance to the current time.
930  */
931 static void set_semotime(struct sem_array *sma, struct sembuf *sops)
932 {
933         if (sops == NULL) {
934                 sma->sem_base[0].sem_otime = get_seconds();
935         } else {
936                 sma->sem_base[sops[0].sem_num].sem_otime =
937                                                         get_seconds();
938         }
939 }
940 
941 /**
942  * do_smart_update - optimized update_queue
943  * @sma: semaphore array
944  * @sops: operations that were performed
945  * @nsops: number of operations
946  * @otime: force setting otime
947  * @pt: list head of the tasks that must be woken up.
948  *
949  * do_smart_update() does the required calls to update_queue and wakeup_zero,
950  * based on the actual changes that were performed on the semaphore array.
951  * Note that the function does not do the actual wake-up: the caller is
952  * responsible for calling wake_up_sem_queue_do(@pt).
953  * It is safe to perform this call after dropping all locks.
954  */
955 static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
956                         int otime, struct list_head *pt)
957 {
958         int i;
959 
960         otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
961 
962         if (!list_empty(&sma->pending_alter)) {
963                 /* semaphore array uses the global queue - just process it. */
964                 otime |= update_queue(sma, -1, pt);
965         } else {
966                 if (!sops) {
967                         /*
968                          * No sops, thus the modified semaphores are not
969                          * known. Check all.
970                          */
971                         for (i = 0; i < sma->sem_nsems; i++)
972                                 otime |= update_queue(sma, i, pt);
973                 } else {
974                         /*
975                          * Check the semaphores that were increased:
976                          * - No complex ops, thus all sleeping ops are
977                          *   decrease.
978                          * - if we decreased the value, then any sleeping
979                          *   semaphore ops wont be able to run: If the
980                          *   previous value was too small, then the new
981                          *   value will be too small, too.
982                          */
983                         for (i = 0; i < nsops; i++) {
984                                 if (sops[i].sem_op > 0) {
985                                         otime |= update_queue(sma,
986                                                         sops[i].sem_num, pt);
987                                 }
988                         }
989                 }
990         }
991         if (otime)
992                 set_semotime(sma, sops);
993 }
994 
995 /*
996  * check_qop: Test if a queued operation sleeps on the semaphore semnum
997  */
998 static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
999                         bool count_zero)
1000 {
1001         struct sembuf *sop = q->blocking;
1002 
1003         /*
1004          * Linux always (since 0.99.10) reported a task as sleeping on all
1005          * semaphores. This violates SUS, therefore it was changed to the
1006          * standard compliant behavior.
1007          * Give the administrators a chance to notice that an application
1008          * might misbehave because it relies on the Linux behavior.
1009          */
1010         pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1011                         "The task %s (%d) triggered the difference, watch for misbehavior.\n",
1012                         current->comm, task_pid_nr(current));
1013 
1014         if (sop->sem_num != semnum)
1015                 return 0;
1016 
1017         if (count_zero && sop->sem_op == 0)
1018                 return 1;
1019         if (!count_zero && sop->sem_op < 0)
1020                 return 1;
1021 
1022         return 0;
1023 }
1024 
1025 /* The following counts are associated to each semaphore:
1026  *   semncnt        number of tasks waiting on semval being nonzero
1027  *   semzcnt        number of tasks waiting on semval being zero
1028  *
1029  * Per definition, a task waits only on the semaphore of the first semop
1030  * that cannot proceed, even if additional operation would block, too.
1031  */
1032 static int count_semcnt(struct sem_array *sma, ushort semnum,
1033                         bool count_zero)
1034 {
1035         struct list_head *l;
1036         struct sem_queue *q;
1037         int semcnt;
1038 
1039         semcnt = 0;
1040         /* First: check the simple operations. They are easy to evaluate */
1041         if (count_zero)
1042                 l = &sma->sem_base[semnum].pending_const;
1043         else
1044                 l = &sma->sem_base[semnum].pending_alter;
1045 
1046         list_for_each_entry(q, l, list) {
1047                 /* all task on a per-semaphore list sleep on exactly
1048                  * that semaphore
1049                  */
1050                 semcnt++;
1051         }
1052 
1053         /* Then: check the complex operations. */
1054         list_for_each_entry(q, &sma->pending_alter, list) {
1055                 semcnt += check_qop(sma, semnum, q, count_zero);
1056         }
1057         if (count_zero) {
1058                 list_for_each_entry(q, &sma->pending_const, list) {
1059                         semcnt += check_qop(sma, semnum, q, count_zero);
1060                 }
1061         }
1062         return semcnt;
1063 }
1064 
1065 /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1066  * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1067  * remains locked on exit.
1068  */
1069 static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1070 {
1071         struct sem_undo *un, *tu;
1072         struct sem_queue *q, *tq;
1073         struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1074         struct list_head tasks;
1075         int i;
1076 
1077         /* Free the existing undo structures for this semaphore set.  */
1078         ipc_assert_locked_object(&sma->sem_perm);
1079         list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1080                 list_del(&un->list_id);
1081                 spin_lock(&un->ulp->lock);
1082                 un->semid = -1;
1083                 list_del_rcu(&un->list_proc);
1084                 spin_unlock(&un->ulp->lock);
1085                 kfree_rcu(un, rcu);
1086         }
1087 
1088         /* Wake up all pending processes and let them fail with EIDRM. */
1089         INIT_LIST_HEAD(&tasks);
1090         list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1091                 unlink_queue(sma, q);
1092                 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1093         }
1094 
1095         list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1096                 unlink_queue(sma, q);
1097                 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1098         }
1099         for (i = 0; i < sma->sem_nsems; i++) {
1100                 struct sem *sem = sma->sem_base + i;
1101                 list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1102                         unlink_queue(sma, q);
1103                         wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1104                 }
1105                 list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1106                         unlink_queue(sma, q);
1107                         wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1108                 }
1109         }
1110 
1111         /* Remove the semaphore set from the IDR */
1112         sem_rmid(ns, sma);
1113         sem_unlock(sma, -1);
1114         rcu_read_unlock();
1115 
1116         wake_up_sem_queue_do(&tasks);
1117         ns->used_sems -= sma->sem_nsems;
1118         ipc_rcu_putref(sma, sem_rcu_free);
1119 }
1120 
1121 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1122 {
1123         switch (version) {
1124         case IPC_64:
1125                 return copy_to_user(buf, in, sizeof(*in));
1126         case IPC_OLD:
1127             {
1128                 struct semid_ds out;
1129 
1130                 memset(&out, 0, sizeof(out));
1131 
1132                 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1133 
1134                 out.sem_otime   = in->sem_otime;
1135                 out.sem_ctime   = in->sem_ctime;
1136                 out.sem_nsems   = in->sem_nsems;
1137 
1138                 return copy_to_user(buf, &out, sizeof(out));
1139             }
1140         default:
1141                 return -EINVAL;
1142         }
1143 }
1144 
1145 static time_t get_semotime(struct sem_array *sma)
1146 {
1147         int i;
1148         time_t res;
1149 
1150         res = sma->sem_base[0].sem_otime;
1151         for (i = 1; i < sma->sem_nsems; i++) {
1152                 time_t to = sma->sem_base[i].sem_otime;
1153 
1154                 if (to > res)
1155                         res = to;
1156         }
1157         return res;
1158 }
1159 
1160 static int semctl_nolock(struct ipc_namespace *ns, int semid,
1161                          int cmd, int version, void __user *p)
1162 {
1163         int err;
1164         struct sem_array *sma;
1165 
1166         switch (cmd) {
1167         case IPC_INFO:
1168         case SEM_INFO:
1169         {
1170                 struct seminfo seminfo;
1171                 int max_id;
1172 
1173                 err = security_sem_semctl(NULL, cmd);
1174                 if (err)
1175                         return err;
1176 
1177                 memset(&seminfo, 0, sizeof(seminfo));
1178                 seminfo.semmni = ns->sc_semmni;
1179                 seminfo.semmns = ns->sc_semmns;
1180                 seminfo.semmsl = ns->sc_semmsl;
1181                 seminfo.semopm = ns->sc_semopm;
1182                 seminfo.semvmx = SEMVMX;
1183                 seminfo.semmnu = SEMMNU;
1184                 seminfo.semmap = SEMMAP;
1185                 seminfo.semume = SEMUME;
1186                 down_read(&sem_ids(ns).rwsem);
1187                 if (cmd == SEM_INFO) {
1188                         seminfo.semusz = sem_ids(ns).in_use;
1189                         seminfo.semaem = ns->used_sems;
1190                 } else {
1191                         seminfo.semusz = SEMUSZ;
1192                         seminfo.semaem = SEMAEM;
1193                 }
1194                 max_id = ipc_get_maxid(&sem_ids(ns));
1195                 up_read(&sem_ids(ns).rwsem);
1196                 if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1197                         return -EFAULT;
1198                 return (max_id < 0) ? 0 : max_id;
1199         }
1200         case IPC_STAT:
1201         case SEM_STAT:
1202         {
1203                 struct semid64_ds tbuf;
1204                 int id = 0;
1205 
1206                 memset(&tbuf, 0, sizeof(tbuf));
1207 
1208                 rcu_read_lock();
1209                 if (cmd == SEM_STAT) {
1210                         sma = sem_obtain_object(ns, semid);
1211                         if (IS_ERR(sma)) {
1212                                 err = PTR_ERR(sma);
1213                                 goto out_unlock;
1214                         }
1215                         id = sma->sem_perm.id;
1216                 } else {
1217                         sma = sem_obtain_object_check(ns, semid);
1218                         if (IS_ERR(sma)) {
1219                                 err = PTR_ERR(sma);
1220                                 goto out_unlock;
1221                         }
1222                 }
1223 
1224                 err = -EACCES;
1225                 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1226                         goto out_unlock;
1227 
1228                 err = security_sem_semctl(sma, cmd);
1229                 if (err)
1230                         goto out_unlock;
1231 
1232                 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1233                 tbuf.sem_otime = get_semotime(sma);
1234                 tbuf.sem_ctime = sma->sem_ctime;
1235                 tbuf.sem_nsems = sma->sem_nsems;
1236                 rcu_read_unlock();
1237                 if (copy_semid_to_user(p, &tbuf, version))
1238                         return -EFAULT;
1239                 return id;
1240         }
1241         default:
1242                 return -EINVAL;
1243         }
1244 out_unlock:
1245         rcu_read_unlock();
1246         return err;
1247 }
1248 
1249 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1250                 unsigned long arg)
1251 {
1252         struct sem_undo *un;
1253         struct sem_array *sma;
1254         struct sem *curr;
1255         int err;
1256         struct list_head tasks;
1257         int val;
1258 #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1259         /* big-endian 64bit */
1260         val = arg >> 32;
1261 #else
1262         /* 32bit or little-endian 64bit */
1263         val = arg;
1264 #endif
1265 
1266         if (val > SEMVMX || val < 0)
1267                 return -ERANGE;
1268 
1269         INIT_LIST_HEAD(&tasks);
1270 
1271         rcu_read_lock();
1272         sma = sem_obtain_object_check(ns, semid);
1273         if (IS_ERR(sma)) {
1274                 rcu_read_unlock();
1275                 return PTR_ERR(sma);
1276         }
1277 
1278         if (semnum < 0 || semnum >= sma->sem_nsems) {
1279                 rcu_read_unlock();
1280                 return -EINVAL;
1281         }
1282 
1283 
1284         if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1285                 rcu_read_unlock();
1286                 return -EACCES;
1287         }
1288 
1289         err = security_sem_semctl(sma, SETVAL);
1290         if (err) {
1291                 rcu_read_unlock();
1292                 return -EACCES;
1293         }
1294 
1295         sem_lock(sma, NULL, -1);
1296 
1297         if (!ipc_valid_object(&sma->sem_perm)) {
1298                 sem_unlock(sma, -1);
1299                 rcu_read_unlock();
1300                 return -EIDRM;
1301         }
1302 
1303         curr = &sma->sem_base[semnum];
1304 
1305         ipc_assert_locked_object(&sma->sem_perm);
1306         list_for_each_entry(un, &sma->list_id, list_id)
1307                 un->semadj[semnum] = 0;
1308 
1309         curr->semval = val;
1310         curr->sempid = task_tgid_vnr(current);
1311         sma->sem_ctime = get_seconds();
1312         /* maybe some queued-up processes were waiting for this */
1313         do_smart_update(sma, NULL, 0, 0, &tasks);
1314         sem_unlock(sma, -1);
1315         rcu_read_unlock();
1316         wake_up_sem_queue_do(&tasks);
1317         return 0;
1318 }
1319 
1320 static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1321                 int cmd, void __user *p)
1322 {
1323         struct sem_array *sma;
1324         struct sem *curr;
1325         int err, nsems;
1326         ushort fast_sem_io[SEMMSL_FAST];
1327         ushort *sem_io = fast_sem_io;
1328         struct list_head tasks;
1329 
1330         INIT_LIST_HEAD(&tasks);
1331 
1332         rcu_read_lock();
1333         sma = sem_obtain_object_check(ns, semid);
1334         if (IS_ERR(sma)) {
1335                 rcu_read_unlock();
1336                 return PTR_ERR(sma);
1337         }
1338 
1339         nsems = sma->sem_nsems;
1340 
1341         err = -EACCES;
1342         if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1343                 goto out_rcu_wakeup;
1344 
1345         err = security_sem_semctl(sma, cmd);
1346         if (err)
1347                 goto out_rcu_wakeup;
1348 
1349         err = -EACCES;
1350         switch (cmd) {
1351         case GETALL:
1352         {
1353                 ushort __user *array = p;
1354                 int i;
1355 
1356                 sem_lock(sma, NULL, -1);
1357                 if (!ipc_valid_object(&sma->sem_perm)) {
1358                         err = -EIDRM;
1359                         goto out_unlock;
1360                 }
1361                 if (nsems > SEMMSL_FAST) {
1362                         if (!ipc_rcu_getref(sma)) {
1363                                 err = -EIDRM;
1364                                 goto out_unlock;
1365                         }
1366                         sem_unlock(sma, -1);
1367                         rcu_read_unlock();
1368                         sem_io = ipc_alloc(sizeof(ushort)*nsems);
1369                         if (sem_io == NULL) {
1370                                 ipc_rcu_putref(sma, ipc_rcu_free);
1371                                 return -ENOMEM;
1372                         }
1373 
1374                         rcu_read_lock();
1375                         sem_lock_and_putref(sma);
1376                         if (!ipc_valid_object(&sma->sem_perm)) {
1377                                 err = -EIDRM;
1378                                 goto out_unlock;
1379                         }
1380                 }
1381                 for (i = 0; i < sma->sem_nsems; i++)
1382                         sem_io[i] = sma->sem_base[i].semval;
1383                 sem_unlock(sma, -1);
1384                 rcu_read_unlock();
1385                 err = 0;
1386                 if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1387                         err = -EFAULT;
1388                 goto out_free;
1389         }
1390         case SETALL:
1391         {
1392                 int i;
1393                 struct sem_undo *un;
1394 
1395                 if (!ipc_rcu_getref(sma)) {
1396                         err = -EIDRM;
1397                         goto out_rcu_wakeup;
1398                 }
1399                 rcu_read_unlock();
1400 
1401                 if (nsems > SEMMSL_FAST) {
1402                         sem_io = ipc_alloc(sizeof(ushort)*nsems);
1403                         if (sem_io == NULL) {
1404                                 ipc_rcu_putref(sma, ipc_rcu_free);
1405                                 return -ENOMEM;
1406                         }
1407                 }
1408 
1409                 if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1410                         ipc_rcu_putref(sma, ipc_rcu_free);
1411                         err = -EFAULT;
1412                         goto out_free;
1413                 }
1414 
1415                 for (i = 0; i < nsems; i++) {
1416                         if (sem_io[i] > SEMVMX) {
1417                                 ipc_rcu_putref(sma, ipc_rcu_free);
1418                                 err = -ERANGE;
1419                                 goto out_free;
1420                         }
1421                 }
1422                 rcu_read_lock();
1423                 sem_lock_and_putref(sma);
1424                 if (!ipc_valid_object(&sma->sem_perm)) {
1425                         err = -EIDRM;
1426                         goto out_unlock;
1427                 }
1428 
1429                 for (i = 0; i < nsems; i++)
1430                         sma->sem_base[i].semval = sem_io[i];
1431 
1432                 ipc_assert_locked_object(&sma->sem_perm);
1433                 list_for_each_entry(un, &sma->list_id, list_id) {
1434                         for (i = 0; i < nsems; i++)
1435                                 un->semadj[i] = 0;
1436                 }
1437                 sma->sem_ctime = get_seconds();
1438                 /* maybe some queued-up processes were waiting for this */
1439                 do_smart_update(sma, NULL, 0, 0, &tasks);
1440                 err = 0;
1441                 goto out_unlock;
1442         }
1443         /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1444         }
1445         err = -EINVAL;
1446         if (semnum < 0 || semnum >= nsems)
1447                 goto out_rcu_wakeup;
1448 
1449         sem_lock(sma, NULL, -1);
1450         if (!ipc_valid_object(&sma->sem_perm)) {
1451                 err = -EIDRM;
1452                 goto out_unlock;
1453         }
1454         curr = &sma->sem_base[semnum];
1455 
1456         switch (cmd) {
1457         case GETVAL:
1458                 err = curr->semval;
1459                 goto out_unlock;
1460         case GETPID:
1461                 err = curr->sempid;
1462                 goto out_unlock;
1463         case GETNCNT:
1464                 err = count_semcnt(sma, semnum, 0);
1465                 goto out_unlock;
1466         case GETZCNT:
1467                 err = count_semcnt(sma, semnum, 1);
1468                 goto out_unlock;
1469         }
1470 
1471 out_unlock:
1472         sem_unlock(sma, -1);
1473 out_rcu_wakeup:
1474         rcu_read_unlock();
1475         wake_up_sem_queue_do(&tasks);
1476 out_free:
1477         if (sem_io != fast_sem_io)
1478                 ipc_free(sem_io, sizeof(ushort)*nsems);
1479         return err;
1480 }
1481 
1482 static inline unsigned long
1483 copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1484 {
1485         switch (version) {
1486         case IPC_64:
1487                 if (copy_from_user(out, buf, sizeof(*out)))
1488                         return -EFAULT;
1489                 return 0;
1490         case IPC_OLD:
1491             {
1492                 struct semid_ds tbuf_old;
1493 
1494                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1495                         return -EFAULT;
1496 
1497                 out->sem_perm.uid       = tbuf_old.sem_perm.uid;
1498                 out->sem_perm.gid       = tbuf_old.sem_perm.gid;
1499                 out->sem_perm.mode      = tbuf_old.sem_perm.mode;
1500 
1501                 return 0;
1502             }
1503         default:
1504                 return -EINVAL;
1505         }
1506 }
1507 
1508 /*
1509  * This function handles some semctl commands which require the rwsem
1510  * to be held in write mode.
1511  * NOTE: no locks must be held, the rwsem is taken inside this function.
1512  */
1513 static int semctl_down(struct ipc_namespace *ns, int semid,
1514                        int cmd, int version, void __user *p)
1515 {
1516         struct sem_array *sma;
1517         int err;
1518         struct semid64_ds semid64;
1519         struct kern_ipc_perm *ipcp;
1520 
1521         if (cmd == IPC_SET) {
1522                 if (copy_semid_from_user(&semid64, p, version))
1523                         return -EFAULT;
1524         }
1525 
1526         down_write(&sem_ids(ns).rwsem);
1527         rcu_read_lock();
1528 
1529         ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1530                                       &semid64.sem_perm, 0);
1531         if (IS_ERR(ipcp)) {
1532                 err = PTR_ERR(ipcp);
1533                 goto out_unlock1;
1534         }
1535 
1536         sma = container_of(ipcp, struct sem_array, sem_perm);
1537 
1538         err = security_sem_semctl(sma, cmd);
1539         if (err)
1540                 goto out_unlock1;
1541 
1542         switch (cmd) {
1543         case IPC_RMID:
1544                 sem_lock(sma, NULL, -1);
1545                 /* freeary unlocks the ipc object and rcu */
1546                 freeary(ns, ipcp);
1547                 goto out_up;
1548         case IPC_SET:
1549                 sem_lock(sma, NULL, -1);
1550                 err = ipc_update_perm(&semid64.sem_perm, ipcp);
1551                 if (err)
1552                         goto out_unlock0;
1553                 sma->sem_ctime = get_seconds();
1554                 break;
1555         default:
1556                 err = -EINVAL;
1557                 goto out_unlock1;
1558         }
1559 
1560 out_unlock0:
1561         sem_unlock(sma, -1);
1562 out_unlock1:
1563         rcu_read_unlock();
1564 out_up:
1565         up_write(&sem_ids(ns).rwsem);
1566         return err;
1567 }
1568 
1569 SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1570 {
1571         int version;
1572         struct ipc_namespace *ns;
1573         void __user *p = (void __user *)arg;
1574 
1575         if (semid < 0)
1576                 return -EINVAL;
1577 
1578         version = ipc_parse_version(&cmd);
1579         ns = current->nsproxy->ipc_ns;
1580 
1581         switch (cmd) {
1582         case IPC_INFO:
1583         case SEM_INFO:
1584         case IPC_STAT:
1585         case SEM_STAT:
1586                 return semctl_nolock(ns, semid, cmd, version, p);
1587         case GETALL:
1588         case GETVAL:
1589         case GETPID:
1590         case GETNCNT:
1591         case GETZCNT:
1592         case SETALL:
1593                 return semctl_main(ns, semid, semnum, cmd, p);
1594         case SETVAL:
1595                 return semctl_setval(ns, semid, semnum, arg);
1596         case IPC_RMID:
1597         case IPC_SET:
1598                 return semctl_down(ns, semid, cmd, version, p);
1599         default:
1600                 return -EINVAL;
1601         }
1602 }
1603 
1604 /* If the task doesn't already have a undo_list, then allocate one
1605  * here.  We guarantee there is only one thread using this undo list,
1606  * and current is THE ONE
1607  *
1608  * If this allocation and assignment succeeds, but later
1609  * portions of this code fail, there is no need to free the sem_undo_list.
1610  * Just let it stay associated with the task, and it'll be freed later
1611  * at exit time.
1612  *
1613  * This can block, so callers must hold no locks.
1614  */
1615 static inline int get_undo_list(struct sem_undo_list **undo_listp)
1616 {
1617         struct sem_undo_list *undo_list;
1618 
1619         undo_list = current->sysvsem.undo_list;
1620         if (!undo_list) {
1621                 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1622                 if (undo_list == NULL)
1623                         return -ENOMEM;
1624                 spin_lock_init(&undo_list->lock);
1625                 atomic_set(&undo_list->refcnt, 1);
1626                 INIT_LIST_HEAD(&undo_list->list_proc);
1627 
1628                 current->sysvsem.undo_list = undo_list;
1629         }
1630         *undo_listp = undo_list;
1631         return 0;
1632 }
1633 
1634 static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1635 {
1636         struct sem_undo *un;
1637 
1638         list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1639                 if (un->semid == semid)
1640                         return un;
1641         }
1642         return NULL;
1643 }
1644 
1645 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1646 {
1647         struct sem_undo *un;
1648 
1649         assert_spin_locked(&ulp->lock);
1650 
1651         un = __lookup_undo(ulp, semid);
1652         if (un) {
1653                 list_del_rcu(&un->list_proc);
1654                 list_add_rcu(&un->list_proc, &ulp->list_proc);
1655         }
1656         return un;
1657 }
1658 
1659 /**
1660  * find_alloc_undo - lookup (and if not present create) undo array
1661  * @ns: namespace
1662  * @semid: semaphore array id
1663  *
1664  * The function looks up (and if not present creates) the undo structure.
1665  * The size of the undo structure depends on the size of the semaphore
1666  * array, thus the alloc path is not that straightforward.
1667  * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1668  * performs a rcu_read_lock().
1669  */
1670 static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1671 {
1672         struct sem_array *sma;
1673         struct sem_undo_list *ulp;
1674         struct sem_undo *un, *new;
1675         int nsems, error;
1676 
1677         error = get_undo_list(&ulp);
1678         if (error)
1679                 return ERR_PTR(error);
1680 
1681         rcu_read_lock();
1682         spin_lock(&ulp->lock);
1683         un = lookup_undo(ulp, semid);
1684         spin_unlock(&ulp->lock);
1685         if (likely(un != NULL))
1686                 goto out;
1687 
1688         /* no undo structure around - allocate one. */
1689         /* step 1: figure out the size of the semaphore array */
1690         sma = sem_obtain_object_check(ns, semid);
1691         if (IS_ERR(sma)) {
1692                 rcu_read_unlock();
1693                 return ERR_CAST(sma);
1694         }
1695 
1696         nsems = sma->sem_nsems;
1697         if (!ipc_rcu_getref(sma)) {
1698                 rcu_read_unlock();
1699                 un = ERR_PTR(-EIDRM);
1700                 goto out;
1701         }
1702         rcu_read_unlock();
1703 
1704         /* step 2: allocate new undo structure */
1705         new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1706         if (!new) {
1707                 ipc_rcu_putref(sma, ipc_rcu_free);
1708                 return ERR_PTR(-ENOMEM);
1709         }
1710 
1711         /* step 3: Acquire the lock on semaphore array */
1712         rcu_read_lock();
1713         sem_lock_and_putref(sma);
1714         if (!ipc_valid_object(&sma->sem_perm)) {
1715                 sem_unlock(sma, -1);
1716                 rcu_read_unlock();
1717                 kfree(new);
1718                 un = ERR_PTR(-EIDRM);
1719                 goto out;
1720         }
1721         spin_lock(&ulp->lock);
1722 
1723         /*
1724          * step 4: check for races: did someone else allocate the undo struct?
1725          */
1726         un = lookup_undo(ulp, semid);
1727         if (un) {
1728                 kfree(new);
1729                 goto success;
1730         }
1731         /* step 5: initialize & link new undo structure */
1732         new->semadj = (short *) &new[1];
1733         new->ulp = ulp;
1734         new->semid = semid;
1735         assert_spin_locked(&ulp->lock);
1736         list_add_rcu(&new->list_proc, &ulp->list_proc);
1737         ipc_assert_locked_object(&sma->sem_perm);
1738         list_add(&new->list_id, &sma->list_id);
1739         un = new;
1740 
1741 success:
1742         spin_unlock(&ulp->lock);
1743         sem_unlock(sma, -1);
1744 out:
1745         return un;
1746 }
1747 
1748 
1749 /**
1750  * get_queue_result - retrieve the result code from sem_queue
1751  * @q: Pointer to queue structure
1752  *
1753  * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1754  * q->status, then we must loop until the value is replaced with the final
1755  * value: This may happen if a task is woken up by an unrelated event (e.g.
1756  * signal) and in parallel the task is woken up by another task because it got
1757  * the requested semaphores.
1758  *
1759  * The function can be called with or without holding the semaphore spinlock.
1760  */
1761 static int get_queue_result(struct sem_queue *q)
1762 {
1763         int error;
1764 
1765         error = q->status;
1766         while (unlikely(error == IN_WAKEUP)) {
1767                 cpu_relax();
1768                 error = q->status;
1769         }
1770 
1771         return error;
1772 }
1773 
1774 SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1775                 unsigned, nsops, const struct timespec __user *, timeout)
1776 {
1777         int error = -EINVAL;
1778         struct sem_array *sma;
1779         struct sembuf fast_sops[SEMOPM_FAST];
1780         struct sembuf *sops = fast_sops, *sop;
1781         struct sem_undo *un;
1782         int undos = 0, alter = 0, max, locknum;
1783         struct sem_queue queue;
1784         unsigned long jiffies_left = 0;
1785         struct ipc_namespace *ns;
1786         struct list_head tasks;
1787 
1788         ns = current->nsproxy->ipc_ns;
1789 
1790         if (nsops < 1 || semid < 0)
1791                 return -EINVAL;
1792         if (nsops > ns->sc_semopm)
1793                 return -E2BIG;
1794         if (nsops > SEMOPM_FAST) {
1795                 sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
1796                 if (sops == NULL)
1797                         return -ENOMEM;
1798         }
1799         if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
1800                 error =  -EFAULT;
1801                 goto out_free;
1802         }
1803         if (timeout) {
1804                 struct timespec _timeout;
1805                 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1806                         error = -EFAULT;
1807                         goto out_free;
1808                 }
1809                 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1810                         _timeout.tv_nsec >= 1000000000L) {
1811                         error = -EINVAL;
1812                         goto out_free;
1813                 }
1814                 jiffies_left = timespec_to_jiffies(&_timeout);
1815         }
1816         max = 0;
1817         for (sop = sops; sop < sops + nsops; sop++) {
1818                 if (sop->sem_num >= max)
1819                         max = sop->sem_num;
1820                 if (sop->sem_flg & SEM_UNDO)
1821                         undos = 1;
1822                 if (sop->sem_op != 0)
1823                         alter = 1;
1824         }
1825 
1826         INIT_LIST_HEAD(&tasks);
1827 
1828         if (undos) {
1829                 /* On success, find_alloc_undo takes the rcu_read_lock */
1830                 un = find_alloc_undo(ns, semid);
1831                 if (IS_ERR(un)) {
1832                         error = PTR_ERR(un);
1833                         goto out_free;
1834                 }
1835         } else {
1836                 un = NULL;
1837                 rcu_read_lock();
1838         }
1839 
1840         sma = sem_obtain_object_check(ns, semid);
1841         if (IS_ERR(sma)) {
1842                 rcu_read_unlock();
1843                 error = PTR_ERR(sma);
1844                 goto out_free;
1845         }
1846 
1847         error = -EFBIG;
1848         if (max >= sma->sem_nsems)
1849                 goto out_rcu_wakeup;
1850 
1851         error = -EACCES;
1852         if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1853                 goto out_rcu_wakeup;
1854 
1855         error = security_sem_semop(sma, sops, nsops, alter);
1856         if (error)
1857                 goto out_rcu_wakeup;
1858 
1859         error = -EIDRM;
1860         locknum = sem_lock(sma, sops, nsops);
1861         /*
1862          * We eventually might perform the following check in a lockless
1863          * fashion, considering ipc_valid_object() locking constraints.
1864          * If nsops == 1 and there is no contention for sem_perm.lock, then
1865          * only a per-semaphore lock is held and it's OK to proceed with the
1866          * check below. More details on the fine grained locking scheme
1867          * entangled here and why it's RMID race safe on comments at sem_lock()
1868          */
1869         if (!ipc_valid_object(&sma->sem_perm))
1870                 goto out_unlock_free;
1871         /*
1872          * semid identifiers are not unique - find_alloc_undo may have
1873          * allocated an undo structure, it was invalidated by an RMID
1874          * and now a new array with received the same id. Check and fail.
1875          * This case can be detected checking un->semid. The existence of
1876          * "un" itself is guaranteed by rcu.
1877          */
1878         if (un && un->semid == -1)
1879                 goto out_unlock_free;
1880 
1881         queue.sops = sops;
1882         queue.nsops = nsops;
1883         queue.undo = un;
1884         queue.pid = task_tgid_vnr(current);
1885         queue.alter = alter;
1886 
1887         error = perform_atomic_semop(sma, &queue);
1888         if (error == 0) {
1889                 /* If the operation was successful, then do
1890                  * the required updates.
1891                  */
1892                 if (alter)
1893                         do_smart_update(sma, sops, nsops, 1, &tasks);
1894                 else
1895                         set_semotime(sma, sops);
1896         }
1897         if (error <= 0)
1898                 goto out_unlock_free;
1899 
1900         /* We need to sleep on this operation, so we put the current
1901          * task into the pending queue and go to sleep.
1902          */
1903 
1904         if (nsops == 1) {
1905                 struct sem *curr;
1906                 curr = &sma->sem_base[sops->sem_num];
1907 
1908                 if (alter) {
1909                         if (sma->complex_count) {
1910                                 list_add_tail(&queue.list,
1911                                                 &sma->pending_alter);
1912                         } else {
1913 
1914                                 list_add_tail(&queue.list,
1915                                                 &curr->pending_alter);
1916                         }
1917                 } else {
1918                         list_add_tail(&queue.list, &curr->pending_const);
1919                 }
1920         } else {
1921                 if (!sma->complex_count)
1922                         merge_queues(sma);
1923 
1924                 if (alter)
1925                         list_add_tail(&queue.list, &sma->pending_alter);
1926                 else
1927                         list_add_tail(&queue.list, &sma->pending_const);
1928 
1929                 sma->complex_count++;
1930         }
1931 
1932         queue.status = -EINTR;
1933         queue.sleeper = current;
1934 
1935 sleep_again:
1936         current->state = TASK_INTERRUPTIBLE;
1937         sem_unlock(sma, locknum);
1938         rcu_read_unlock();
1939 
1940         if (timeout)
1941                 jiffies_left = schedule_timeout(jiffies_left);
1942         else
1943                 schedule();
1944 
1945         error = get_queue_result(&queue);
1946 
1947         if (error != -EINTR) {
1948                 /* fast path: update_queue already obtained all requested
1949                  * resources.
1950                  * Perform a smp_mb(): User space could assume that semop()
1951                  * is a memory barrier: Without the mb(), the cpu could
1952                  * speculatively read in user space stale data that was
1953                  * overwritten by the previous owner of the semaphore.
1954                  */
1955                 smp_mb();
1956 
1957                 goto out_free;
1958         }
1959 
1960         rcu_read_lock();
1961         sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1962 
1963         /*
1964          * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1965          */
1966         error = get_queue_result(&queue);
1967 
1968         /*
1969          * Array removed? If yes, leave without sem_unlock().
1970          */
1971         if (IS_ERR(sma)) {
1972                 rcu_read_unlock();
1973                 goto out_free;
1974         }
1975 
1976 
1977         /*
1978          * If queue.status != -EINTR we are woken up by another process.
1979          * Leave without unlink_queue(), but with sem_unlock().
1980          */
1981         if (error != -EINTR)
1982                 goto out_unlock_free;
1983 
1984         /*
1985          * If an interrupt occurred we have to clean up the queue
1986          */
1987         if (timeout && jiffies_left == 0)
1988                 error = -EAGAIN;
1989 
1990         /*
1991          * If the wakeup was spurious, just retry
1992          */
1993         if (error == -EINTR && !signal_pending(current))
1994                 goto sleep_again;
1995 
1996         unlink_queue(sma, &queue);
1997 
1998 out_unlock_free:
1999         sem_unlock(sma, locknum);
2000 out_rcu_wakeup:
2001         rcu_read_unlock();
2002         wake_up_sem_queue_do(&tasks);
2003 out_free:
2004         if (sops != fast_sops)
2005                 kfree(sops);
2006         return error;
2007 }
2008 
2009 SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2010                 unsigned, nsops)
2011 {
2012         return sys_semtimedop(semid, tsops, nsops, NULL);
2013 }
2014 
2015 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2016  * parent and child tasks.
2017  */
2018 
2019 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2020 {
2021         struct sem_undo_list *undo_list;
2022         int error;
2023 
2024         if (clone_flags & CLONE_SYSVSEM) {
2025                 error = get_undo_list(&undo_list);
2026                 if (error)
2027                         return error;
2028                 atomic_inc(&undo_list->refcnt);
2029                 tsk->sysvsem.undo_list = undo_list;
2030         } else
2031                 tsk->sysvsem.undo_list = NULL;
2032 
2033         return 0;
2034 }
2035 
2036 /*
2037  * add semadj values to semaphores, free undo structures.
2038  * undo structures are not freed when semaphore arrays are destroyed
2039  * so some of them may be out of date.
2040  * IMPLEMENTATION NOTE: There is some confusion over whether the
2041  * set of adjustments that needs to be done should be done in an atomic
2042  * manner or not. That is, if we are attempting to decrement the semval
2043  * should we queue up and wait until we can do so legally?
2044  * The original implementation attempted to do this (queue and wait).
2045  * The current implementation does not do so. The POSIX standard
2046  * and SVID should be consulted to determine what behavior is mandated.
2047  */
2048 void exit_sem(struct task_struct *tsk)
2049 {
2050         struct sem_undo_list *ulp;
2051 
2052         ulp = tsk->sysvsem.undo_list;
2053         if (!ulp)
2054                 return;
2055         tsk->sysvsem.undo_list = NULL;
2056 
2057         if (!atomic_dec_and_test(&ulp->refcnt))
2058                 return;
2059 
2060         for (;;) {
2061                 struct sem_array *sma;
2062                 struct sem_undo *un;
2063                 struct list_head tasks;
2064                 int semid, i;
2065 
2066                 rcu_read_lock();
2067                 un = list_entry_rcu(ulp->list_proc.next,
2068                                     struct sem_undo, list_proc);
2069                 if (&un->list_proc == &ulp->list_proc)
2070                         semid = -1;
2071                  else
2072                         semid = un->semid;
2073 
2074                 if (semid == -1) {
2075                         rcu_read_unlock();
2076                         break;
2077                 }
2078 
2079                 sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
2080                 /* exit_sem raced with IPC_RMID, nothing to do */
2081                 if (IS_ERR(sma)) {
2082                         rcu_read_unlock();
2083                         continue;
2084                 }
2085 
2086                 sem_lock(sma, NULL, -1);
2087                 /* exit_sem raced with IPC_RMID, nothing to do */
2088                 if (!ipc_valid_object(&sma->sem_perm)) {
2089                         sem_unlock(sma, -1);
2090                         rcu_read_unlock();
2091                         continue;
2092                 }
2093                 un = __lookup_undo(ulp, semid);
2094                 if (un == NULL) {
2095                         /* exit_sem raced with IPC_RMID+semget() that created
2096                          * exactly the same semid. Nothing to do.
2097                          */
2098                         sem_unlock(sma, -1);
2099                         rcu_read_unlock();
2100                         continue;
2101                 }
2102 
2103                 /* remove un from the linked lists */
2104                 ipc_assert_locked_object(&sma->sem_perm);
2105                 list_del(&un->list_id);
2106 
2107                 spin_lock(&ulp->lock);
2108                 list_del_rcu(&un->list_proc);
2109                 spin_unlock(&ulp->lock);
2110 
2111                 /* perform adjustments registered in un */
2112                 for (i = 0; i < sma->sem_nsems; i++) {
2113                         struct sem *semaphore = &sma->sem_base[i];
2114                         if (un->semadj[i]) {
2115                                 semaphore->semval += un->semadj[i];
2116                                 /*
2117                                  * Range checks of the new semaphore value,
2118                                  * not defined by sus:
2119                                  * - Some unices ignore the undo entirely
2120                                  *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2121                                  * - some cap the value (e.g. FreeBSD caps
2122                                  *   at 0, but doesn't enforce SEMVMX)
2123                                  *
2124                                  * Linux caps the semaphore value, both at 0
2125                                  * and at SEMVMX.
2126                                  *
2127                                  *      Manfred <manfred@colorfullife.com>
2128                                  */
2129                                 if (semaphore->semval < 0)
2130                                         semaphore->semval = 0;
2131                                 if (semaphore->semval > SEMVMX)
2132                                         semaphore->semval = SEMVMX;
2133                                 semaphore->sempid = task_tgid_vnr(current);
2134                         }
2135                 }
2136                 /* maybe some queued-up processes were waiting for this */
2137                 INIT_LIST_HEAD(&tasks);
2138                 do_smart_update(sma, NULL, 0, 1, &tasks);
2139                 sem_unlock(sma, -1);
2140                 rcu_read_unlock();
2141                 wake_up_sem_queue_do(&tasks);
2142 
2143                 kfree_rcu(un, rcu);
2144         }
2145         kfree(ulp);
2146 }
2147 
2148 #ifdef CONFIG_PROC_FS
2149 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2150 {
2151         struct user_namespace *user_ns = seq_user_ns(s);
2152         struct sem_array *sma = it;
2153         time_t sem_otime;
2154 
2155         /*
2156          * The proc interface isn't aware of sem_lock(), it calls
2157          * ipc_lock_object() directly (in sysvipc_find_ipc).
2158          * In order to stay compatible with sem_lock(), we must wait until
2159          * all simple semop() calls have left their critical regions.
2160          */
2161         sem_wait_array(sma);
2162 
2163         sem_otime = get_semotime(sma);
2164 
2165         return seq_printf(s,
2166                           "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2167                           sma->sem_perm.key,
2168                           sma->sem_perm.id,
2169                           sma->sem_perm.mode,
2170                           sma->sem_nsems,
2171                           from_kuid_munged(user_ns, sma->sem_perm.uid),
2172                           from_kgid_munged(user_ns, sma->sem_perm.gid),
2173                           from_kuid_munged(user_ns, sma->sem_perm.cuid),
2174                           from_kgid_munged(user_ns, sma->sem_perm.cgid),
2175                           sem_otime,
2176                           sma->sem_ctime);
2177 }
2178 #endif
2179 

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