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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                         /*
330                          * The ipc object lock check must be visible on all
331                          * cores before rechecking the complex count.  Otherwise
332                          * we can race with  another thread that does:
333                          *      complex_count++;
334                          *      spin_unlock(sem_perm.lock);
335                          */
336                         smp_rmb();
337 
338                         /*
339                          * Now repeat the test of complex_count:
340                          * It can't change anymore until we drop sem->lock.
341                          * Thus: if is now 0, then it will stay 0.
342                          */
343                         if (sma->complex_count == 0) {
344                                 /* fast path successful! */
345                                 return sops->sem_num;
346                         }
347                 }
348                 spin_unlock(&sem->lock);
349         }
350 
351         /* slow path: acquire the full lock */
352         ipc_lock_object(&sma->sem_perm);
353 
354         if (sma->complex_count == 0) {
355                 /* False alarm:
356                  * There is no complex operation, thus we can switch
357                  * back to the fast path.
358                  */
359                 spin_lock(&sem->lock);
360                 ipc_unlock_object(&sma->sem_perm);
361                 return sops->sem_num;
362         } else {
363                 /* Not a false alarm, thus complete the sequence for a
364                  * full lock.
365                  */
366                 sem_wait_array(sma);
367                 return -1;
368         }
369 }
370 
371 static inline void sem_unlock(struct sem_array *sma, int locknum)
372 {
373         if (locknum == -1) {
374                 unmerge_queues(sma);
375                 ipc_unlock_object(&sma->sem_perm);
376         } else {
377                 struct sem *sem = sma->sem_base + locknum;
378                 spin_unlock(&sem->lock);
379         }
380 }
381 
382 /*
383  * sem_lock_(check_) routines are called in the paths where the rwsem
384  * is not held.
385  *
386  * The caller holds the RCU read lock.
387  */
388 static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
389                         int id, struct sembuf *sops, int nsops, int *locknum)
390 {
391         struct kern_ipc_perm *ipcp;
392         struct sem_array *sma;
393 
394         ipcp = ipc_obtain_object(&sem_ids(ns), id);
395         if (IS_ERR(ipcp))
396                 return ERR_CAST(ipcp);
397 
398         sma = container_of(ipcp, struct sem_array, sem_perm);
399         *locknum = sem_lock(sma, sops, nsops);
400 
401         /* ipc_rmid() may have already freed the ID while sem_lock
402          * was spinning: verify that the structure is still valid
403          */
404         if (ipc_valid_object(ipcp))
405                 return container_of(ipcp, struct sem_array, sem_perm);
406 
407         sem_unlock(sma, *locknum);
408         return ERR_PTR(-EINVAL);
409 }
410 
411 static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
412 {
413         struct kern_ipc_perm *ipcp = ipc_obtain_object(&sem_ids(ns), id);
414 
415         if (IS_ERR(ipcp))
416                 return ERR_CAST(ipcp);
417 
418         return container_of(ipcp, struct sem_array, sem_perm);
419 }
420 
421 static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
422                                                         int id)
423 {
424         struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
425 
426         if (IS_ERR(ipcp))
427                 return ERR_CAST(ipcp);
428 
429         return container_of(ipcp, struct sem_array, sem_perm);
430 }
431 
432 static inline void sem_lock_and_putref(struct sem_array *sma)
433 {
434         sem_lock(sma, NULL, -1);
435         ipc_rcu_putref(sma, ipc_rcu_free);
436 }
437 
438 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
439 {
440         ipc_rmid(&sem_ids(ns), &s->sem_perm);
441 }
442 
443 /*
444  * Lockless wakeup algorithm:
445  * Without the check/retry algorithm a lockless wakeup is possible:
446  * - queue.status is initialized to -EINTR before blocking.
447  * - wakeup is performed by
448  *      * unlinking the queue entry from the pending list
449  *      * setting queue.status to IN_WAKEUP
450  *        This is the notification for the blocked thread that a
451  *        result value is imminent.
452  *      * call wake_up_process
453  *      * set queue.status to the final value.
454  * - the previously blocked thread checks queue.status:
455  *      * if it's IN_WAKEUP, then it must wait until the value changes
456  *      * if it's not -EINTR, then the operation was completed by
457  *        update_queue. semtimedop can return queue.status without
458  *        performing any operation on the sem array.
459  *      * otherwise it must acquire the spinlock and check what's up.
460  *
461  * The two-stage algorithm is necessary to protect against the following
462  * races:
463  * - if queue.status is set after wake_up_process, then the woken up idle
464  *   thread could race forward and try (and fail) to acquire sma->lock
465  *   before update_queue had a chance to set queue.status
466  * - if queue.status is written before wake_up_process and if the
467  *   blocked process is woken up by a signal between writing
468  *   queue.status and the wake_up_process, then the woken up
469  *   process could return from semtimedop and die by calling
470  *   sys_exit before wake_up_process is called. Then wake_up_process
471  *   will oops, because the task structure is already invalid.
472  *   (yes, this happened on s390 with sysv msg).
473  *
474  */
475 #define IN_WAKEUP       1
476 
477 /**
478  * newary - Create a new semaphore set
479  * @ns: namespace
480  * @params: ptr to the structure that contains key, semflg and nsems
481  *
482  * Called with sem_ids.rwsem held (as a writer)
483  */
484 static int newary(struct ipc_namespace *ns, struct ipc_params *params)
485 {
486         int id;
487         int retval;
488         struct sem_array *sma;
489         int size;
490         key_t key = params->key;
491         int nsems = params->u.nsems;
492         int semflg = params->flg;
493         int i;
494 
495         if (!nsems)
496                 return -EINVAL;
497         if (ns->used_sems + nsems > ns->sc_semmns)
498                 return -ENOSPC;
499 
500         size = sizeof(*sma) + nsems * sizeof(struct sem);
501         sma = ipc_rcu_alloc(size);
502         if (!sma)
503                 return -ENOMEM;
504 
505         memset(sma, 0, size);
506 
507         sma->sem_perm.mode = (semflg & S_IRWXUGO);
508         sma->sem_perm.key = key;
509 
510         sma->sem_perm.security = NULL;
511         retval = security_sem_alloc(sma);
512         if (retval) {
513                 ipc_rcu_putref(sma, ipc_rcu_free);
514                 return retval;
515         }
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 
532         id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
533         if (id < 0) {
534                 ipc_rcu_putref(sma, sem_rcu_free);
535                 return id;
536         }
537         ns->used_sems += nsems;
538 
539         sem_unlock(sma, -1);
540         rcu_read_unlock();
541 
542         return sma->sem_perm.id;
543 }
544 
545 
546 /*
547  * Called with sem_ids.rwsem and ipcp locked.
548  */
549 static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
550 {
551         struct sem_array *sma;
552 
553         sma = container_of(ipcp, struct sem_array, sem_perm);
554         return security_sem_associate(sma, semflg);
555 }
556 
557 /*
558  * Called with sem_ids.rwsem and ipcp locked.
559  */
560 static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
561                                 struct ipc_params *params)
562 {
563         struct sem_array *sma;
564 
565         sma = container_of(ipcp, struct sem_array, sem_perm);
566         if (params->u.nsems > sma->sem_nsems)
567                 return -EINVAL;
568 
569         return 0;
570 }
571 
572 SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
573 {
574         struct ipc_namespace *ns;
575         static const struct ipc_ops sem_ops = {
576                 .getnew = newary,
577                 .associate = sem_security,
578                 .more_checks = sem_more_checks,
579         };
580         struct ipc_params sem_params;
581 
582         ns = current->nsproxy->ipc_ns;
583 
584         if (nsems < 0 || nsems > ns->sc_semmsl)
585                 return -EINVAL;
586 
587         sem_params.key = key;
588         sem_params.flg = semflg;
589         sem_params.u.nsems = nsems;
590 
591         return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
592 }
593 
594 /**
595  * perform_atomic_semop - Perform (if possible) a semaphore operation
596  * @sma: semaphore array
597  * @q: struct sem_queue that describes the operation
598  *
599  * Returns 0 if the operation was possible.
600  * Returns 1 if the operation is impossible, the caller must sleep.
601  * Negative values are error codes.
602  */
603 static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
604 {
605         int result, sem_op, nsops, pid;
606         struct sembuf *sop;
607         struct sem *curr;
608         struct sembuf *sops;
609         struct sem_undo *un;
610 
611         sops = q->sops;
612         nsops = q->nsops;
613         un = q->undo;
614 
615         for (sop = sops; sop < sops + nsops; sop++) {
616                 curr = sma->sem_base + sop->sem_num;
617                 sem_op = sop->sem_op;
618                 result = curr->semval;
619 
620                 if (!sem_op && result)
621                         goto would_block;
622 
623                 result += sem_op;
624                 if (result < 0)
625                         goto would_block;
626                 if (result > SEMVMX)
627                         goto out_of_range;
628 
629                 if (sop->sem_flg & SEM_UNDO) {
630                         int undo = un->semadj[sop->sem_num] - sem_op;
631                         /* Exceeding the undo range is an error. */
632                         if (undo < (-SEMAEM - 1) || undo > SEMAEM)
633                                 goto out_of_range;
634                         un->semadj[sop->sem_num] = undo;
635                 }
636 
637                 curr->semval = result;
638         }
639 
640         sop--;
641         pid = q->pid;
642         while (sop >= sops) {
643                 sma->sem_base[sop->sem_num].sempid = pid;
644                 sop--;
645         }
646 
647         return 0;
648 
649 out_of_range:
650         result = -ERANGE;
651         goto undo;
652 
653 would_block:
654         q->blocking = sop;
655 
656         if (sop->sem_flg & IPC_NOWAIT)
657                 result = -EAGAIN;
658         else
659                 result = 1;
660 
661 undo:
662         sop--;
663         while (sop >= sops) {
664                 sem_op = sop->sem_op;
665                 sma->sem_base[sop->sem_num].semval -= sem_op;
666                 if (sop->sem_flg & SEM_UNDO)
667                         un->semadj[sop->sem_num] += sem_op;
668                 sop--;
669         }
670 
671         return result;
672 }
673 
674 /** wake_up_sem_queue_prepare(q, error): Prepare wake-up
675  * @q: queue entry that must be signaled
676  * @error: Error value for the signal
677  *
678  * Prepare the wake-up of the queue entry q.
679  */
680 static void wake_up_sem_queue_prepare(struct list_head *pt,
681                                 struct sem_queue *q, int error)
682 {
683         if (list_empty(pt)) {
684                 /*
685                  * Hold preempt off so that we don't get preempted and have the
686                  * wakee busy-wait until we're scheduled back on.
687                  */
688                 preempt_disable();
689         }
690         q->status = IN_WAKEUP;
691         q->pid = error;
692 
693         list_add_tail(&q->list, pt);
694 }
695 
696 /**
697  * wake_up_sem_queue_do - do the actual wake-up
698  * @pt: list of tasks to be woken up
699  *
700  * Do the actual wake-up.
701  * The function is called without any locks held, thus the semaphore array
702  * could be destroyed already and the tasks can disappear as soon as the
703  * status is set to the actual return code.
704  */
705 static void wake_up_sem_queue_do(struct list_head *pt)
706 {
707         struct sem_queue *q, *t;
708         int did_something;
709 
710         did_something = !list_empty(pt);
711         list_for_each_entry_safe(q, t, pt, list) {
712                 wake_up_process(q->sleeper);
713                 /* q can disappear immediately after writing q->status. */
714                 smp_wmb();
715                 q->status = q->pid;
716         }
717         if (did_something)
718                 preempt_enable();
719 }
720 
721 static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
722 {
723         list_del(&q->list);
724         if (q->nsops > 1)
725                 sma->complex_count--;
726 }
727 
728 /** check_restart(sma, q)
729  * @sma: semaphore array
730  * @q: the operation that just completed
731  *
732  * update_queue is O(N^2) when it restarts scanning the whole queue of
733  * waiting operations. Therefore this function checks if the restart is
734  * really necessary. It is called after a previously waiting operation
735  * modified the array.
736  * Note that wait-for-zero operations are handled without restart.
737  */
738 static int check_restart(struct sem_array *sma, struct sem_queue *q)
739 {
740         /* pending complex alter operations are too difficult to analyse */
741         if (!list_empty(&sma->pending_alter))
742                 return 1;
743 
744         /* we were a sleeping complex operation. Too difficult */
745         if (q->nsops > 1)
746                 return 1;
747 
748         /* It is impossible that someone waits for the new value:
749          * - complex operations always restart.
750          * - wait-for-zero are handled seperately.
751          * - q is a previously sleeping simple operation that
752          *   altered the array. It must be a decrement, because
753          *   simple increments never sleep.
754          * - If there are older (higher priority) decrements
755          *   in the queue, then they have observed the original
756          *   semval value and couldn't proceed. The operation
757          *   decremented to value - thus they won't proceed either.
758          */
759         return 0;
760 }
761 
762 /**
763  * wake_const_ops - wake up non-alter tasks
764  * @sma: semaphore array.
765  * @semnum: semaphore that was modified.
766  * @pt: list head for the tasks that must be woken up.
767  *
768  * wake_const_ops must be called after a semaphore in a semaphore array
769  * was set to 0. If complex const operations are pending, wake_const_ops must
770  * be called with semnum = -1, as well as with the number of each modified
771  * semaphore.
772  * The tasks that must be woken up are added to @pt. The return code
773  * is stored in q->pid.
774  * The function returns 1 if at least one operation was completed successfully.
775  */
776 static int wake_const_ops(struct sem_array *sma, int semnum,
777                                 struct list_head *pt)
778 {
779         struct sem_queue *q;
780         struct list_head *walk;
781         struct list_head *pending_list;
782         int semop_completed = 0;
783 
784         if (semnum == -1)
785                 pending_list = &sma->pending_const;
786         else
787                 pending_list = &sma->sem_base[semnum].pending_const;
788 
789         walk = pending_list->next;
790         while (walk != pending_list) {
791                 int error;
792 
793                 q = container_of(walk, struct sem_queue, list);
794                 walk = walk->next;
795 
796                 error = perform_atomic_semop(sma, q);
797 
798                 if (error <= 0) {
799                         /* operation completed, remove from queue & wakeup */
800 
801                         unlink_queue(sma, q);
802 
803                         wake_up_sem_queue_prepare(pt, q, error);
804                         if (error == 0)
805                                 semop_completed = 1;
806                 }
807         }
808         return semop_completed;
809 }
810 
811 /**
812  * do_smart_wakeup_zero - wakeup all wait for zero tasks
813  * @sma: semaphore array
814  * @sops: operations that were performed
815  * @nsops: number of operations
816  * @pt: list head of the tasks that must be woken up.
817  *
818  * Checks all required queue for wait-for-zero operations, based
819  * on the actual changes that were performed on the semaphore array.
820  * The function returns 1 if at least one operation was completed successfully.
821  */
822 static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
823                                         int nsops, struct list_head *pt)
824 {
825         int i;
826         int semop_completed = 0;
827         int got_zero = 0;
828 
829         /* first: the per-semaphore queues, if known */
830         if (sops) {
831                 for (i = 0; i < nsops; i++) {
832                         int num = sops[i].sem_num;
833 
834                         if (sma->sem_base[num].semval == 0) {
835                                 got_zero = 1;
836                                 semop_completed |= wake_const_ops(sma, num, pt);
837                         }
838                 }
839         } else {
840                 /*
841                  * No sops means modified semaphores not known.
842                  * Assume all were changed.
843                  */
844                 for (i = 0; i < sma->sem_nsems; i++) {
845                         if (sma->sem_base[i].semval == 0) {
846                                 got_zero = 1;
847                                 semop_completed |= wake_const_ops(sma, i, pt);
848                         }
849                 }
850         }
851         /*
852          * If one of the modified semaphores got 0,
853          * then check the global queue, too.
854          */
855         if (got_zero)
856                 semop_completed |= wake_const_ops(sma, -1, pt);
857 
858         return semop_completed;
859 }
860 
861 
862 /**
863  * update_queue - look for tasks that can be completed.
864  * @sma: semaphore array.
865  * @semnum: semaphore that was modified.
866  * @pt: list head for the tasks that must be woken up.
867  *
868  * update_queue must be called after a semaphore in a semaphore array
869  * was modified. If multiple semaphores were modified, update_queue must
870  * be called with semnum = -1, as well as with the number of each modified
871  * semaphore.
872  * The tasks that must be woken up are added to @pt. The return code
873  * is stored in q->pid.
874  * The function internally checks if const operations can now succeed.
875  *
876  * The function return 1 if at least one semop was completed successfully.
877  */
878 static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
879 {
880         struct sem_queue *q;
881         struct list_head *walk;
882         struct list_head *pending_list;
883         int semop_completed = 0;
884 
885         if (semnum == -1)
886                 pending_list = &sma->pending_alter;
887         else
888                 pending_list = &sma->sem_base[semnum].pending_alter;
889 
890 again:
891         walk = pending_list->next;
892         while (walk != pending_list) {
893                 int error, restart;
894 
895                 q = container_of(walk, struct sem_queue, list);
896                 walk = walk->next;
897 
898                 /* If we are scanning the single sop, per-semaphore list of
899                  * one semaphore and that semaphore is 0, then it is not
900                  * necessary to scan further: simple increments
901                  * that affect only one entry succeed immediately and cannot
902                  * be in the  per semaphore pending queue, and decrements
903                  * cannot be successful if the value is already 0.
904                  */
905                 if (semnum != -1 && sma->sem_base[semnum].semval == 0)
906                         break;
907 
908                 error = perform_atomic_semop(sma, q);
909 
910                 /* Does q->sleeper still need to sleep? */
911                 if (error > 0)
912                         continue;
913 
914                 unlink_queue(sma, q);
915 
916                 if (error) {
917                         restart = 0;
918                 } else {
919                         semop_completed = 1;
920                         do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
921                         restart = check_restart(sma, q);
922                 }
923 
924                 wake_up_sem_queue_prepare(pt, q, error);
925                 if (restart)
926                         goto again;
927         }
928         return semop_completed;
929 }
930 
931 /**
932  * set_semotime - set sem_otime
933  * @sma: semaphore array
934  * @sops: operations that modified the array, may be NULL
935  *
936  * sem_otime is replicated to avoid cache line trashing.
937  * This function sets one instance to the current time.
938  */
939 static void set_semotime(struct sem_array *sma, struct sembuf *sops)
940 {
941         if (sops == NULL) {
942                 sma->sem_base[0].sem_otime = get_seconds();
943         } else {
944                 sma->sem_base[sops[0].sem_num].sem_otime =
945                                                         get_seconds();
946         }
947 }
948 
949 /**
950  * do_smart_update - optimized update_queue
951  * @sma: semaphore array
952  * @sops: operations that were performed
953  * @nsops: number of operations
954  * @otime: force setting otime
955  * @pt: list head of the tasks that must be woken up.
956  *
957  * do_smart_update() does the required calls to update_queue and wakeup_zero,
958  * based on the actual changes that were performed on the semaphore array.
959  * Note that the function does not do the actual wake-up: the caller is
960  * responsible for calling wake_up_sem_queue_do(@pt).
961  * It is safe to perform this call after dropping all locks.
962  */
963 static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
964                         int otime, struct list_head *pt)
965 {
966         int i;
967 
968         otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);
969 
970         if (!list_empty(&sma->pending_alter)) {
971                 /* semaphore array uses the global queue - just process it. */
972                 otime |= update_queue(sma, -1, pt);
973         } else {
974                 if (!sops) {
975                         /*
976                          * No sops, thus the modified semaphores are not
977                          * known. Check all.
978                          */
979                         for (i = 0; i < sma->sem_nsems; i++)
980                                 otime |= update_queue(sma, i, pt);
981                 } else {
982                         /*
983                          * Check the semaphores that were increased:
984                          * - No complex ops, thus all sleeping ops are
985                          *   decrease.
986                          * - if we decreased the value, then any sleeping
987                          *   semaphore ops wont be able to run: If the
988                          *   previous value was too small, then the new
989                          *   value will be too small, too.
990                          */
991                         for (i = 0; i < nsops; i++) {
992                                 if (sops[i].sem_op > 0) {
993                                         otime |= update_queue(sma,
994                                                         sops[i].sem_num, pt);
995                                 }
996                         }
997                 }
998         }
999         if (otime)
1000                 set_semotime(sma, sops);
1001 }
1002 
1003 /*
1004  * check_qop: Test if a queued operation sleeps on the semaphore semnum
1005  */
1006 static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1007                         bool count_zero)
1008 {
1009         struct sembuf *sop = q->blocking;
1010 
1011         /*
1012          * Linux always (since 0.99.10) reported a task as sleeping on all
1013          * semaphores. This violates SUS, therefore it was changed to the
1014          * standard compliant behavior.
1015          * Give the administrators a chance to notice that an application
1016          * might misbehave because it relies on the Linux behavior.
1017          */
1018         pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1019                         "The task %s (%d) triggered the difference, watch for misbehavior.\n",
1020                         current->comm, task_pid_nr(current));
1021 
1022         if (sop->sem_num != semnum)
1023                 return 0;
1024 
1025         if (count_zero && sop->sem_op == 0)
1026                 return 1;
1027         if (!count_zero && sop->sem_op < 0)
1028                 return 1;
1029 
1030         return 0;
1031 }
1032 
1033 /* The following counts are associated to each semaphore:
1034  *   semncnt        number of tasks waiting on semval being nonzero
1035  *   semzcnt        number of tasks waiting on semval being zero
1036  *
1037  * Per definition, a task waits only on the semaphore of the first semop
1038  * that cannot proceed, even if additional operation would block, too.
1039  */
1040 static int count_semcnt(struct sem_array *sma, ushort semnum,
1041                         bool count_zero)
1042 {
1043         struct list_head *l;
1044         struct sem_queue *q;
1045         int semcnt;
1046 
1047         semcnt = 0;
1048         /* First: check the simple operations. They are easy to evaluate */
1049         if (count_zero)
1050                 l = &sma->sem_base[semnum].pending_const;
1051         else
1052                 l = &sma->sem_base[semnum].pending_alter;
1053 
1054         list_for_each_entry(q, l, list) {
1055                 /* all task on a per-semaphore list sleep on exactly
1056                  * that semaphore
1057                  */
1058                 semcnt++;
1059         }
1060 
1061         /* Then: check the complex operations. */
1062         list_for_each_entry(q, &sma->pending_alter, list) {
1063                 semcnt += check_qop(sma, semnum, q, count_zero);
1064         }
1065         if (count_zero) {
1066                 list_for_each_entry(q, &sma->pending_const, list) {
1067                         semcnt += check_qop(sma, semnum, q, count_zero);
1068                 }
1069         }
1070         return semcnt;
1071 }
1072 
1073 /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1074  * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1075  * remains locked on exit.
1076  */
1077 static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1078 {
1079         struct sem_undo *un, *tu;
1080         struct sem_queue *q, *tq;
1081         struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1082         struct list_head tasks;
1083         int i;
1084 
1085         /* Free the existing undo structures for this semaphore set.  */
1086         ipc_assert_locked_object(&sma->sem_perm);
1087         list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1088                 list_del(&un->list_id);
1089                 spin_lock(&un->ulp->lock);
1090                 un->semid = -1;
1091                 list_del_rcu(&un->list_proc);
1092                 spin_unlock(&un->ulp->lock);
1093                 kfree_rcu(un, rcu);
1094         }
1095 
1096         /* Wake up all pending processes and let them fail with EIDRM. */
1097         INIT_LIST_HEAD(&tasks);
1098         list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1099                 unlink_queue(sma, q);
1100                 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1101         }
1102 
1103         list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1104                 unlink_queue(sma, q);
1105                 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1106         }
1107         for (i = 0; i < sma->sem_nsems; i++) {
1108                 struct sem *sem = sma->sem_base + i;
1109                 list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1110                         unlink_queue(sma, q);
1111                         wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1112                 }
1113                 list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1114                         unlink_queue(sma, q);
1115                         wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
1116                 }
1117         }
1118 
1119         /* Remove the semaphore set from the IDR */
1120         sem_rmid(ns, sma);
1121         sem_unlock(sma, -1);
1122         rcu_read_unlock();
1123 
1124         wake_up_sem_queue_do(&tasks);
1125         ns->used_sems -= sma->sem_nsems;
1126         ipc_rcu_putref(sma, sem_rcu_free);
1127 }
1128 
1129 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1130 {
1131         switch (version) {
1132         case IPC_64:
1133                 return copy_to_user(buf, in, sizeof(*in));
1134         case IPC_OLD:
1135             {
1136                 struct semid_ds out;
1137 
1138                 memset(&out, 0, sizeof(out));
1139 
1140                 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1141 
1142                 out.sem_otime   = in->sem_otime;
1143                 out.sem_ctime   = in->sem_ctime;
1144                 out.sem_nsems   = in->sem_nsems;
1145 
1146                 return copy_to_user(buf, &out, sizeof(out));
1147             }
1148         default:
1149                 return -EINVAL;
1150         }
1151 }
1152 
1153 static time_t get_semotime(struct sem_array *sma)
1154 {
1155         int i;
1156         time_t res;
1157 
1158         res = sma->sem_base[0].sem_otime;
1159         for (i = 1; i < sma->sem_nsems; i++) {
1160                 time_t to = sma->sem_base[i].sem_otime;
1161 
1162                 if (to > res)
1163                         res = to;
1164         }
1165         return res;
1166 }
1167 
1168 static int semctl_nolock(struct ipc_namespace *ns, int semid,
1169                          int cmd, int version, void __user *p)
1170 {
1171         int err;
1172         struct sem_array *sma;
1173 
1174         switch (cmd) {
1175         case IPC_INFO:
1176         case SEM_INFO:
1177         {
1178                 struct seminfo seminfo;
1179                 int max_id;
1180 
1181                 err = security_sem_semctl(NULL, cmd);
1182                 if (err)
1183                         return err;
1184 
1185                 memset(&seminfo, 0, sizeof(seminfo));
1186                 seminfo.semmni = ns->sc_semmni;
1187                 seminfo.semmns = ns->sc_semmns;
1188                 seminfo.semmsl = ns->sc_semmsl;
1189                 seminfo.semopm = ns->sc_semopm;
1190                 seminfo.semvmx = SEMVMX;
1191                 seminfo.semmnu = SEMMNU;
1192                 seminfo.semmap = SEMMAP;
1193                 seminfo.semume = SEMUME;
1194                 down_read(&sem_ids(ns).rwsem);
1195                 if (cmd == SEM_INFO) {
1196                         seminfo.semusz = sem_ids(ns).in_use;
1197                         seminfo.semaem = ns->used_sems;
1198                 } else {
1199                         seminfo.semusz = SEMUSZ;
1200                         seminfo.semaem = SEMAEM;
1201                 }
1202                 max_id = ipc_get_maxid(&sem_ids(ns));
1203                 up_read(&sem_ids(ns).rwsem);
1204                 if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1205                         return -EFAULT;
1206                 return (max_id < 0) ? 0 : max_id;
1207         }
1208         case IPC_STAT:
1209         case SEM_STAT:
1210         {
1211                 struct semid64_ds tbuf;
1212                 int id = 0;
1213 
1214                 memset(&tbuf, 0, sizeof(tbuf));
1215 
1216                 rcu_read_lock();
1217                 if (cmd == SEM_STAT) {
1218                         sma = sem_obtain_object(ns, semid);
1219                         if (IS_ERR(sma)) {
1220                                 err = PTR_ERR(sma);
1221                                 goto out_unlock;
1222                         }
1223                         id = sma->sem_perm.id;
1224                 } else {
1225                         sma = sem_obtain_object_check(ns, semid);
1226                         if (IS_ERR(sma)) {
1227                                 err = PTR_ERR(sma);
1228                                 goto out_unlock;
1229                         }
1230                 }
1231 
1232                 err = -EACCES;
1233                 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1234                         goto out_unlock;
1235 
1236                 err = security_sem_semctl(sma, cmd);
1237                 if (err)
1238                         goto out_unlock;
1239 
1240                 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1241                 tbuf.sem_otime = get_semotime(sma);
1242                 tbuf.sem_ctime = sma->sem_ctime;
1243                 tbuf.sem_nsems = sma->sem_nsems;
1244                 rcu_read_unlock();
1245                 if (copy_semid_to_user(p, &tbuf, version))
1246                         return -EFAULT;
1247                 return id;
1248         }
1249         default:
1250                 return -EINVAL;
1251         }
1252 out_unlock:
1253         rcu_read_unlock();
1254         return err;
1255 }
1256 
1257 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1258                 unsigned long arg)
1259 {
1260         struct sem_undo *un;
1261         struct sem_array *sma;
1262         struct sem *curr;
1263         int err;
1264         struct list_head tasks;
1265         int val;
1266 #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1267         /* big-endian 64bit */
1268         val = arg >> 32;
1269 #else
1270         /* 32bit or little-endian 64bit */
1271         val = arg;
1272 #endif
1273 
1274         if (val > SEMVMX || val < 0)
1275                 return -ERANGE;
1276 
1277         INIT_LIST_HEAD(&tasks);
1278 
1279         rcu_read_lock();
1280         sma = sem_obtain_object_check(ns, semid);
1281         if (IS_ERR(sma)) {
1282                 rcu_read_unlock();
1283                 return PTR_ERR(sma);
1284         }
1285 
1286         if (semnum < 0 || semnum >= sma->sem_nsems) {
1287                 rcu_read_unlock();
1288                 return -EINVAL;
1289         }
1290 
1291 
1292         if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1293                 rcu_read_unlock();
1294                 return -EACCES;
1295         }
1296 
1297         err = security_sem_semctl(sma, SETVAL);
1298         if (err) {
1299                 rcu_read_unlock();
1300                 return -EACCES;
1301         }
1302 
1303         sem_lock(sma, NULL, -1);
1304 
1305         if (!ipc_valid_object(&sma->sem_perm)) {
1306                 sem_unlock(sma, -1);
1307                 rcu_read_unlock();
1308                 return -EIDRM;
1309         }
1310 
1311         curr = &sma->sem_base[semnum];
1312 
1313         ipc_assert_locked_object(&sma->sem_perm);
1314         list_for_each_entry(un, &sma->list_id, list_id)
1315                 un->semadj[semnum] = 0;
1316 
1317         curr->semval = val;
1318         curr->sempid = task_tgid_vnr(current);
1319         sma->sem_ctime = get_seconds();
1320         /* maybe some queued-up processes were waiting for this */
1321         do_smart_update(sma, NULL, 0, 0, &tasks);
1322         sem_unlock(sma, -1);
1323         rcu_read_unlock();
1324         wake_up_sem_queue_do(&tasks);
1325         return 0;
1326 }
1327 
1328 static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1329                 int cmd, void __user *p)
1330 {
1331         struct sem_array *sma;
1332         struct sem *curr;
1333         int err, nsems;
1334         ushort fast_sem_io[SEMMSL_FAST];
1335         ushort *sem_io = fast_sem_io;
1336         struct list_head tasks;
1337 
1338         INIT_LIST_HEAD(&tasks);
1339 
1340         rcu_read_lock();
1341         sma = sem_obtain_object_check(ns, semid);
1342         if (IS_ERR(sma)) {
1343                 rcu_read_unlock();
1344                 return PTR_ERR(sma);
1345         }
1346 
1347         nsems = sma->sem_nsems;
1348 
1349         err = -EACCES;
1350         if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1351                 goto out_rcu_wakeup;
1352 
1353         err = security_sem_semctl(sma, cmd);
1354         if (err)
1355                 goto out_rcu_wakeup;
1356 
1357         err = -EACCES;
1358         switch (cmd) {
1359         case GETALL:
1360         {
1361                 ushort __user *array = p;
1362                 int i;
1363 
1364                 sem_lock(sma, NULL, -1);
1365                 if (!ipc_valid_object(&sma->sem_perm)) {
1366                         err = -EIDRM;
1367                         goto out_unlock;
1368                 }
1369                 if (nsems > SEMMSL_FAST) {
1370                         if (!ipc_rcu_getref(sma)) {
1371                                 err = -EIDRM;
1372                                 goto out_unlock;
1373                         }
1374                         sem_unlock(sma, -1);
1375                         rcu_read_unlock();
1376                         sem_io = ipc_alloc(sizeof(ushort)*nsems);
1377                         if (sem_io == NULL) {
1378                                 ipc_rcu_putref(sma, ipc_rcu_free);
1379                                 return -ENOMEM;
1380                         }
1381 
1382                         rcu_read_lock();
1383                         sem_lock_and_putref(sma);
1384                         if (!ipc_valid_object(&sma->sem_perm)) {
1385                                 err = -EIDRM;
1386                                 goto out_unlock;
1387                         }
1388                 }
1389                 for (i = 0; i < sma->sem_nsems; i++)
1390                         sem_io[i] = sma->sem_base[i].semval;
1391                 sem_unlock(sma, -1);
1392                 rcu_read_unlock();
1393                 err = 0;
1394                 if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1395                         err = -EFAULT;
1396                 goto out_free;
1397         }
1398         case SETALL:
1399         {
1400                 int i;
1401                 struct sem_undo *un;
1402 
1403                 if (!ipc_rcu_getref(sma)) {
1404                         err = -EIDRM;
1405                         goto out_rcu_wakeup;
1406                 }
1407                 rcu_read_unlock();
1408 
1409                 if (nsems > SEMMSL_FAST) {
1410                         sem_io = ipc_alloc(sizeof(ushort)*nsems);
1411                         if (sem_io == NULL) {
1412                                 ipc_rcu_putref(sma, ipc_rcu_free);
1413                                 return -ENOMEM;
1414                         }
1415                 }
1416 
1417                 if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1418                         ipc_rcu_putref(sma, ipc_rcu_free);
1419                         err = -EFAULT;
1420                         goto out_free;
1421                 }
1422 
1423                 for (i = 0; i < nsems; i++) {
1424                         if (sem_io[i] > SEMVMX) {
1425                                 ipc_rcu_putref(sma, ipc_rcu_free);
1426                                 err = -ERANGE;
1427                                 goto out_free;
1428                         }
1429                 }
1430                 rcu_read_lock();
1431                 sem_lock_and_putref(sma);
1432                 if (!ipc_valid_object(&sma->sem_perm)) {
1433                         err = -EIDRM;
1434                         goto out_unlock;
1435                 }
1436 
1437                 for (i = 0; i < nsems; i++)
1438                         sma->sem_base[i].semval = sem_io[i];
1439 
1440                 ipc_assert_locked_object(&sma->sem_perm);
1441                 list_for_each_entry(un, &sma->list_id, list_id) {
1442                         for (i = 0; i < nsems; i++)
1443                                 un->semadj[i] = 0;
1444                 }
1445                 sma->sem_ctime = get_seconds();
1446                 /* maybe some queued-up processes were waiting for this */
1447                 do_smart_update(sma, NULL, 0, 0, &tasks);
1448                 err = 0;
1449                 goto out_unlock;
1450         }
1451         /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1452         }
1453         err = -EINVAL;
1454         if (semnum < 0 || semnum >= nsems)
1455                 goto out_rcu_wakeup;
1456 
1457         sem_lock(sma, NULL, -1);
1458         if (!ipc_valid_object(&sma->sem_perm)) {
1459                 err = -EIDRM;
1460                 goto out_unlock;
1461         }
1462         curr = &sma->sem_base[semnum];
1463 
1464         switch (cmd) {
1465         case GETVAL:
1466                 err = curr->semval;
1467                 goto out_unlock;
1468         case GETPID:
1469                 err = curr->sempid;
1470                 goto out_unlock;
1471         case GETNCNT:
1472                 err = count_semcnt(sma, semnum, 0);
1473                 goto out_unlock;
1474         case GETZCNT:
1475                 err = count_semcnt(sma, semnum, 1);
1476                 goto out_unlock;
1477         }
1478 
1479 out_unlock:
1480         sem_unlock(sma, -1);
1481 out_rcu_wakeup:
1482         rcu_read_unlock();
1483         wake_up_sem_queue_do(&tasks);
1484 out_free:
1485         if (sem_io != fast_sem_io)
1486                 ipc_free(sem_io, sizeof(ushort)*nsems);
1487         return err;
1488 }
1489 
1490 static inline unsigned long
1491 copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1492 {
1493         switch (version) {
1494         case IPC_64:
1495                 if (copy_from_user(out, buf, sizeof(*out)))
1496                         return -EFAULT;
1497                 return 0;
1498         case IPC_OLD:
1499             {
1500                 struct semid_ds tbuf_old;
1501 
1502                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1503                         return -EFAULT;
1504 
1505                 out->sem_perm.uid       = tbuf_old.sem_perm.uid;
1506                 out->sem_perm.gid       = tbuf_old.sem_perm.gid;
1507                 out->sem_perm.mode      = tbuf_old.sem_perm.mode;
1508 
1509                 return 0;
1510             }
1511         default:
1512                 return -EINVAL;
1513         }
1514 }
1515 
1516 /*
1517  * This function handles some semctl commands which require the rwsem
1518  * to be held in write mode.
1519  * NOTE: no locks must be held, the rwsem is taken inside this function.
1520  */
1521 static int semctl_down(struct ipc_namespace *ns, int semid,
1522                        int cmd, int version, void __user *p)
1523 {
1524         struct sem_array *sma;
1525         int err;
1526         struct semid64_ds semid64;
1527         struct kern_ipc_perm *ipcp;
1528 
1529         if (cmd == IPC_SET) {
1530                 if (copy_semid_from_user(&semid64, p, version))
1531                         return -EFAULT;
1532         }
1533 
1534         down_write(&sem_ids(ns).rwsem);
1535         rcu_read_lock();
1536 
1537         ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
1538                                       &semid64.sem_perm, 0);
1539         if (IS_ERR(ipcp)) {
1540                 err = PTR_ERR(ipcp);
1541                 goto out_unlock1;
1542         }
1543 
1544         sma = container_of(ipcp, struct sem_array, sem_perm);
1545 
1546         err = security_sem_semctl(sma, cmd);
1547         if (err)
1548                 goto out_unlock1;
1549 
1550         switch (cmd) {
1551         case IPC_RMID:
1552                 sem_lock(sma, NULL, -1);
1553                 /* freeary unlocks the ipc object and rcu */
1554                 freeary(ns, ipcp);
1555                 goto out_up;
1556         case IPC_SET:
1557                 sem_lock(sma, NULL, -1);
1558                 err = ipc_update_perm(&semid64.sem_perm, ipcp);
1559                 if (err)
1560                         goto out_unlock0;
1561                 sma->sem_ctime = get_seconds();
1562                 break;
1563         default:
1564                 err = -EINVAL;
1565                 goto out_unlock1;
1566         }
1567 
1568 out_unlock0:
1569         sem_unlock(sma, -1);
1570 out_unlock1:
1571         rcu_read_unlock();
1572 out_up:
1573         up_write(&sem_ids(ns).rwsem);
1574         return err;
1575 }
1576 
1577 SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1578 {
1579         int version;
1580         struct ipc_namespace *ns;
1581         void __user *p = (void __user *)arg;
1582 
1583         if (semid < 0)
1584                 return -EINVAL;
1585 
1586         version = ipc_parse_version(&cmd);
1587         ns = current->nsproxy->ipc_ns;
1588 
1589         switch (cmd) {
1590         case IPC_INFO:
1591         case SEM_INFO:
1592         case IPC_STAT:
1593         case SEM_STAT:
1594                 return semctl_nolock(ns, semid, cmd, version, p);
1595         case GETALL:
1596         case GETVAL:
1597         case GETPID:
1598         case GETNCNT:
1599         case GETZCNT:
1600         case SETALL:
1601                 return semctl_main(ns, semid, semnum, cmd, p);
1602         case SETVAL:
1603                 return semctl_setval(ns, semid, semnum, arg);
1604         case IPC_RMID:
1605         case IPC_SET:
1606                 return semctl_down(ns, semid, cmd, version, p);
1607         default:
1608                 return -EINVAL;
1609         }
1610 }
1611 
1612 /* If the task doesn't already have a undo_list, then allocate one
1613  * here.  We guarantee there is only one thread using this undo list,
1614  * and current is THE ONE
1615  *
1616  * If this allocation and assignment succeeds, but later
1617  * portions of this code fail, there is no need to free the sem_undo_list.
1618  * Just let it stay associated with the task, and it'll be freed later
1619  * at exit time.
1620  *
1621  * This can block, so callers must hold no locks.
1622  */
1623 static inline int get_undo_list(struct sem_undo_list **undo_listp)
1624 {
1625         struct sem_undo_list *undo_list;
1626 
1627         undo_list = current->sysvsem.undo_list;
1628         if (!undo_list) {
1629                 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1630                 if (undo_list == NULL)
1631                         return -ENOMEM;
1632                 spin_lock_init(&undo_list->lock);
1633                 atomic_set(&undo_list->refcnt, 1);
1634                 INIT_LIST_HEAD(&undo_list->list_proc);
1635 
1636                 current->sysvsem.undo_list = undo_list;
1637         }
1638         *undo_listp = undo_list;
1639         return 0;
1640 }
1641 
1642 static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1643 {
1644         struct sem_undo *un;
1645 
1646         list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1647                 if (un->semid == semid)
1648                         return un;
1649         }
1650         return NULL;
1651 }
1652 
1653 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1654 {
1655         struct sem_undo *un;
1656 
1657         assert_spin_locked(&ulp->lock);
1658 
1659         un = __lookup_undo(ulp, semid);
1660         if (un) {
1661                 list_del_rcu(&un->list_proc);
1662                 list_add_rcu(&un->list_proc, &ulp->list_proc);
1663         }
1664         return un;
1665 }
1666 
1667 /**
1668  * find_alloc_undo - lookup (and if not present create) undo array
1669  * @ns: namespace
1670  * @semid: semaphore array id
1671  *
1672  * The function looks up (and if not present creates) the undo structure.
1673  * The size of the undo structure depends on the size of the semaphore
1674  * array, thus the alloc path is not that straightforward.
1675  * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1676  * performs a rcu_read_lock().
1677  */
1678 static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1679 {
1680         struct sem_array *sma;
1681         struct sem_undo_list *ulp;
1682         struct sem_undo *un, *new;
1683         int nsems, error;
1684 
1685         error = get_undo_list(&ulp);
1686         if (error)
1687                 return ERR_PTR(error);
1688 
1689         rcu_read_lock();
1690         spin_lock(&ulp->lock);
1691         un = lookup_undo(ulp, semid);
1692         spin_unlock(&ulp->lock);
1693         if (likely(un != NULL))
1694                 goto out;
1695 
1696         /* no undo structure around - allocate one. */
1697         /* step 1: figure out the size of the semaphore array */
1698         sma = sem_obtain_object_check(ns, semid);
1699         if (IS_ERR(sma)) {
1700                 rcu_read_unlock();
1701                 return ERR_CAST(sma);
1702         }
1703 
1704         nsems = sma->sem_nsems;
1705         if (!ipc_rcu_getref(sma)) {
1706                 rcu_read_unlock();
1707                 un = ERR_PTR(-EIDRM);
1708                 goto out;
1709         }
1710         rcu_read_unlock();
1711 
1712         /* step 2: allocate new undo structure */
1713         new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1714         if (!new) {
1715                 ipc_rcu_putref(sma, ipc_rcu_free);
1716                 return ERR_PTR(-ENOMEM);
1717         }
1718 
1719         /* step 3: Acquire the lock on semaphore array */
1720         rcu_read_lock();
1721         sem_lock_and_putref(sma);
1722         if (!ipc_valid_object(&sma->sem_perm)) {
1723                 sem_unlock(sma, -1);
1724                 rcu_read_unlock();
1725                 kfree(new);
1726                 un = ERR_PTR(-EIDRM);
1727                 goto out;
1728         }
1729         spin_lock(&ulp->lock);
1730 
1731         /*
1732          * step 4: check for races: did someone else allocate the undo struct?
1733          */
1734         un = lookup_undo(ulp, semid);
1735         if (un) {
1736                 kfree(new);
1737                 goto success;
1738         }
1739         /* step 5: initialize & link new undo structure */
1740         new->semadj = (short *) &new[1];
1741         new->ulp = ulp;
1742         new->semid = semid;
1743         assert_spin_locked(&ulp->lock);
1744         list_add_rcu(&new->list_proc, &ulp->list_proc);
1745         ipc_assert_locked_object(&sma->sem_perm);
1746         list_add(&new->list_id, &sma->list_id);
1747         un = new;
1748 
1749 success:
1750         spin_unlock(&ulp->lock);
1751         sem_unlock(sma, -1);
1752 out:
1753         return un;
1754 }
1755 
1756 
1757 /**
1758  * get_queue_result - retrieve the result code from sem_queue
1759  * @q: Pointer to queue structure
1760  *
1761  * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1762  * q->status, then we must loop until the value is replaced with the final
1763  * value: This may happen if a task is woken up by an unrelated event (e.g.
1764  * signal) and in parallel the task is woken up by another task because it got
1765  * the requested semaphores.
1766  *
1767  * The function can be called with or without holding the semaphore spinlock.
1768  */
1769 static int get_queue_result(struct sem_queue *q)
1770 {
1771         int error;
1772 
1773         error = q->status;
1774         while (unlikely(error == IN_WAKEUP)) {
1775                 cpu_relax();
1776                 error = q->status;
1777         }
1778 
1779         return error;
1780 }
1781 
1782 SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1783                 unsigned, nsops, const struct timespec __user *, timeout)
1784 {
1785         int error = -EINVAL;
1786         struct sem_array *sma;
1787         struct sembuf fast_sops[SEMOPM_FAST];
1788         struct sembuf *sops = fast_sops, *sop;
1789         struct sem_undo *un;
1790         int undos = 0, alter = 0, max, locknum;
1791         struct sem_queue queue;
1792         unsigned long jiffies_left = 0;
1793         struct ipc_namespace *ns;
1794         struct list_head tasks;
1795 
1796         ns = current->nsproxy->ipc_ns;
1797 
1798         if (nsops < 1 || semid < 0)
1799                 return -EINVAL;
1800         if (nsops > ns->sc_semopm)
1801                 return -E2BIG;
1802         if (nsops > SEMOPM_FAST) {
1803                 sops = kmalloc(sizeof(*sops)*nsops, GFP_KERNEL);
1804                 if (sops == NULL)
1805                         return -ENOMEM;
1806         }
1807         if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
1808                 error =  -EFAULT;
1809                 goto out_free;
1810         }
1811         if (timeout) {
1812                 struct timespec _timeout;
1813                 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1814                         error = -EFAULT;
1815                         goto out_free;
1816                 }
1817                 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1818                         _timeout.tv_nsec >= 1000000000L) {
1819                         error = -EINVAL;
1820                         goto out_free;
1821                 }
1822                 jiffies_left = timespec_to_jiffies(&_timeout);
1823         }
1824         max = 0;
1825         for (sop = sops; sop < sops + nsops; sop++) {
1826                 if (sop->sem_num >= max)
1827                         max = sop->sem_num;
1828                 if (sop->sem_flg & SEM_UNDO)
1829                         undos = 1;
1830                 if (sop->sem_op != 0)
1831                         alter = 1;
1832         }
1833 
1834         INIT_LIST_HEAD(&tasks);
1835 
1836         if (undos) {
1837                 /* On success, find_alloc_undo takes the rcu_read_lock */
1838                 un = find_alloc_undo(ns, semid);
1839                 if (IS_ERR(un)) {
1840                         error = PTR_ERR(un);
1841                         goto out_free;
1842                 }
1843         } else {
1844                 un = NULL;
1845                 rcu_read_lock();
1846         }
1847 
1848         sma = sem_obtain_object_check(ns, semid);
1849         if (IS_ERR(sma)) {
1850                 rcu_read_unlock();
1851                 error = PTR_ERR(sma);
1852                 goto out_free;
1853         }
1854 
1855         error = -EFBIG;
1856         if (max >= sma->sem_nsems)
1857                 goto out_rcu_wakeup;
1858 
1859         error = -EACCES;
1860         if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1861                 goto out_rcu_wakeup;
1862 
1863         error = security_sem_semop(sma, sops, nsops, alter);
1864         if (error)
1865                 goto out_rcu_wakeup;
1866 
1867         error = -EIDRM;
1868         locknum = sem_lock(sma, sops, nsops);
1869         /*
1870          * We eventually might perform the following check in a lockless
1871          * fashion, considering ipc_valid_object() locking constraints.
1872          * If nsops == 1 and there is no contention for sem_perm.lock, then
1873          * only a per-semaphore lock is held and it's OK to proceed with the
1874          * check below. More details on the fine grained locking scheme
1875          * entangled here and why it's RMID race safe on comments at sem_lock()
1876          */
1877         if (!ipc_valid_object(&sma->sem_perm))
1878                 goto out_unlock_free;
1879         /*
1880          * semid identifiers are not unique - find_alloc_undo may have
1881          * allocated an undo structure, it was invalidated by an RMID
1882          * and now a new array with received the same id. Check and fail.
1883          * This case can be detected checking un->semid. The existence of
1884          * "un" itself is guaranteed by rcu.
1885          */
1886         if (un && un->semid == -1)
1887                 goto out_unlock_free;
1888 
1889         queue.sops = sops;
1890         queue.nsops = nsops;
1891         queue.undo = un;
1892         queue.pid = task_tgid_vnr(current);
1893         queue.alter = alter;
1894 
1895         error = perform_atomic_semop(sma, &queue);
1896         if (error == 0) {
1897                 /* If the operation was successful, then do
1898                  * the required updates.
1899                  */
1900                 if (alter)
1901                         do_smart_update(sma, sops, nsops, 1, &tasks);
1902                 else
1903                         set_semotime(sma, sops);
1904         }
1905         if (error <= 0)
1906                 goto out_unlock_free;
1907 
1908         /* We need to sleep on this operation, so we put the current
1909          * task into the pending queue and go to sleep.
1910          */
1911 
1912         if (nsops == 1) {
1913                 struct sem *curr;
1914                 curr = &sma->sem_base[sops->sem_num];
1915 
1916                 if (alter) {
1917                         if (sma->complex_count) {
1918                                 list_add_tail(&queue.list,
1919                                                 &sma->pending_alter);
1920                         } else {
1921 
1922                                 list_add_tail(&queue.list,
1923                                                 &curr->pending_alter);
1924                         }
1925                 } else {
1926                         list_add_tail(&queue.list, &curr->pending_const);
1927                 }
1928         } else {
1929                 if (!sma->complex_count)
1930                         merge_queues(sma);
1931 
1932                 if (alter)
1933                         list_add_tail(&queue.list, &sma->pending_alter);
1934                 else
1935                         list_add_tail(&queue.list, &sma->pending_const);
1936 
1937                 sma->complex_count++;
1938         }
1939 
1940         queue.status = -EINTR;
1941         queue.sleeper = current;
1942 
1943 sleep_again:
1944         __set_current_state(TASK_INTERRUPTIBLE);
1945         sem_unlock(sma, locknum);
1946         rcu_read_unlock();
1947 
1948         if (timeout)
1949                 jiffies_left = schedule_timeout(jiffies_left);
1950         else
1951                 schedule();
1952 
1953         error = get_queue_result(&queue);
1954 
1955         if (error != -EINTR) {
1956                 /* fast path: update_queue already obtained all requested
1957                  * resources.
1958                  * Perform a smp_mb(): User space could assume that semop()
1959                  * is a memory barrier: Without the mb(), the cpu could
1960                  * speculatively read in user space stale data that was
1961                  * overwritten by the previous owner of the semaphore.
1962                  */
1963                 smp_mb();
1964 
1965                 goto out_free;
1966         }
1967 
1968         rcu_read_lock();
1969         sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1970 
1971         /*
1972          * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1973          */
1974         error = get_queue_result(&queue);
1975 
1976         /*
1977          * Array removed? If yes, leave without sem_unlock().
1978          */
1979         if (IS_ERR(sma)) {
1980                 rcu_read_unlock();
1981                 goto out_free;
1982         }
1983 
1984 
1985         /*
1986          * If queue.status != -EINTR we are woken up by another process.
1987          * Leave without unlink_queue(), but with sem_unlock().
1988          */
1989         if (error != -EINTR)
1990                 goto out_unlock_free;
1991 
1992         /*
1993          * If an interrupt occurred we have to clean up the queue
1994          */
1995         if (timeout && jiffies_left == 0)
1996                 error = -EAGAIN;
1997 
1998         /*
1999          * If the wakeup was spurious, just retry
2000          */
2001         if (error == -EINTR && !signal_pending(current))
2002                 goto sleep_again;
2003 
2004         unlink_queue(sma, &queue);
2005 
2006 out_unlock_free:
2007         sem_unlock(sma, locknum);
2008 out_rcu_wakeup:
2009         rcu_read_unlock();
2010         wake_up_sem_queue_do(&tasks);
2011 out_free:
2012         if (sops != fast_sops)
2013                 kfree(sops);
2014         return error;
2015 }
2016 
2017 SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2018                 unsigned, nsops)
2019 {
2020         return sys_semtimedop(semid, tsops, nsops, NULL);
2021 }
2022 
2023 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2024  * parent and child tasks.
2025  */
2026 
2027 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2028 {
2029         struct sem_undo_list *undo_list;
2030         int error;
2031 
2032         if (clone_flags & CLONE_SYSVSEM) {
2033                 error = get_undo_list(&undo_list);
2034                 if (error)
2035                         return error;
2036                 atomic_inc(&undo_list->refcnt);
2037                 tsk->sysvsem.undo_list = undo_list;
2038         } else
2039                 tsk->sysvsem.undo_list = NULL;
2040 
2041         return 0;
2042 }
2043 
2044 /*
2045  * add semadj values to semaphores, free undo structures.
2046  * undo structures are not freed when semaphore arrays are destroyed
2047  * so some of them may be out of date.
2048  * IMPLEMENTATION NOTE: There is some confusion over whether the
2049  * set of adjustments that needs to be done should be done in an atomic
2050  * manner or not. That is, if we are attempting to decrement the semval
2051  * should we queue up and wait until we can do so legally?
2052  * The original implementation attempted to do this (queue and wait).
2053  * The current implementation does not do so. The POSIX standard
2054  * and SVID should be consulted to determine what behavior is mandated.
2055  */
2056 void exit_sem(struct task_struct *tsk)
2057 {
2058         struct sem_undo_list *ulp;
2059 
2060         ulp = tsk->sysvsem.undo_list;
2061         if (!ulp)
2062                 return;
2063         tsk->sysvsem.undo_list = NULL;
2064 
2065         if (!atomic_dec_and_test(&ulp->refcnt))
2066                 return;
2067 
2068         for (;;) {
2069                 struct sem_array *sma;
2070                 struct sem_undo *un;
2071                 struct list_head tasks;
2072                 int semid, i;
2073 
2074                 rcu_read_lock();
2075                 un = list_entry_rcu(ulp->list_proc.next,
2076                                     struct sem_undo, list_proc);
2077                 if (&un->list_proc == &ulp->list_proc)
2078                         semid = -1;
2079                  else
2080                         semid = un->semid;
2081 
2082                 if (semid == -1) {
2083                         rcu_read_unlock();
2084                         break;
2085                 }
2086 
2087                 sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
2088                 /* exit_sem raced with IPC_RMID, nothing to do */
2089                 if (IS_ERR(sma)) {
2090                         rcu_read_unlock();
2091                         continue;
2092                 }
2093 
2094                 sem_lock(sma, NULL, -1);
2095                 /* exit_sem raced with IPC_RMID, nothing to do */
2096                 if (!ipc_valid_object(&sma->sem_perm)) {
2097                         sem_unlock(sma, -1);
2098                         rcu_read_unlock();
2099                         continue;
2100                 }
2101                 un = __lookup_undo(ulp, semid);
2102                 if (un == NULL) {
2103                         /* exit_sem raced with IPC_RMID+semget() that created
2104                          * exactly the same semid. Nothing to do.
2105                          */
2106                         sem_unlock(sma, -1);
2107                         rcu_read_unlock();
2108                         continue;
2109                 }
2110 
2111                 /* remove un from the linked lists */
2112                 ipc_assert_locked_object(&sma->sem_perm);
2113                 list_del(&un->list_id);
2114 
2115                 spin_lock(&ulp->lock);
2116                 list_del_rcu(&un->list_proc);
2117                 spin_unlock(&ulp->lock);
2118 
2119                 /* perform adjustments registered in un */
2120                 for (i = 0; i < sma->sem_nsems; i++) {
2121                         struct sem *semaphore = &sma->sem_base[i];
2122                         if (un->semadj[i]) {
2123                                 semaphore->semval += un->semadj[i];
2124                                 /*
2125                                  * Range checks of the new semaphore value,
2126                                  * not defined by sus:
2127                                  * - Some unices ignore the undo entirely
2128                                  *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2129                                  * - some cap the value (e.g. FreeBSD caps
2130                                  *   at 0, but doesn't enforce SEMVMX)
2131                                  *
2132                                  * Linux caps the semaphore value, both at 0
2133                                  * and at SEMVMX.
2134                                  *
2135                                  *      Manfred <manfred@colorfullife.com>
2136                                  */
2137                                 if (semaphore->semval < 0)
2138                                         semaphore->semval = 0;
2139                                 if (semaphore->semval > SEMVMX)
2140                                         semaphore->semval = SEMVMX;
2141                                 semaphore->sempid = task_tgid_vnr(current);
2142                         }
2143                 }
2144                 /* maybe some queued-up processes were waiting for this */
2145                 INIT_LIST_HEAD(&tasks);
2146                 do_smart_update(sma, NULL, 0, 1, &tasks);
2147                 sem_unlock(sma, -1);
2148                 rcu_read_unlock();
2149                 wake_up_sem_queue_do(&tasks);
2150 
2151                 kfree_rcu(un, rcu);
2152         }
2153         kfree(ulp);
2154 }
2155 
2156 #ifdef CONFIG_PROC_FS
2157 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2158 {
2159         struct user_namespace *user_ns = seq_user_ns(s);
2160         struct sem_array *sma = it;
2161         time_t sem_otime;
2162 
2163         /*
2164          * The proc interface isn't aware of sem_lock(), it calls
2165          * ipc_lock_object() directly (in sysvipc_find_ipc).
2166          * In order to stay compatible with sem_lock(), we must wait until
2167          * all simple semop() calls have left their critical regions.
2168          */
2169         sem_wait_array(sma);
2170 
2171         sem_otime = get_semotime(sma);
2172 
2173         return seq_printf(s,
2174                           "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2175                           sma->sem_perm.key,
2176                           sma->sem_perm.id,
2177                           sma->sem_perm.mode,
2178                           sma->sem_nsems,
2179                           from_kuid_munged(user_ns, sma->sem_perm.uid),
2180                           from_kgid_munged(user_ns, sma->sem_perm.gid),
2181                           from_kuid_munged(user_ns, sma->sem_perm.cuid),
2182                           from_kgid_munged(user_ns, sma->sem_perm.cgid),
2183                           sem_otime,
2184                           sma->sem_ctime);
2185 }
2186 #endif
2187 

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