Root/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_semncnt() and
51 * count_semzcnt()
52 * - the task that performs a successful semop() scans the list of all
53 * sleeping tasks and completes any pending operations that can be fulfilled.
54 * Semaphores are actively given to waiting tasks (necessary for FIFO).
55 * (see update_queue())
56 * - To improve the scalability, the actual wake-up calls are performed after
57 * dropping all locks. (see wake_up_sem_queue_prepare(),
58 * wake_up_sem_queue_do())
59 * - All work is done by the waker, the woken up task does not have to do
60 * anything - not even acquiring a lock or dropping a refcount.
61 * - A woken up task may not even touch the semaphore array anymore, it may
62 * have been destroyed already by a semctl(RMID).
63 * - The synchronizations between wake-ups due to a timeout/signal and a
64 * wake-up due to a completed semaphore operation is achieved by using an
65 * intermediate state (IN_WAKEUP).
66 * - UNDO values are stored in an array (one per process and per
67 * semaphore array, lazily allocated). For backwards compatibility, multiple
68 * modes for the UNDO variables are supported (per process, per thread)
69 * (see copy_semundo, CLONE_SYSVSEM)
70 * - There are two lists of the pending operations: a per-array list
71 * and per-semaphore list (stored in the array). This allows to achieve FIFO
72 * ordering without always scanning all pending operations.
73 * The worst-case behavior is nevertheless O(N^2) for N wakeups.
74 */
75
76#include <linux/slab.h>
77#include <linux/spinlock.h>
78#include <linux/init.h>
79#include <linux/proc_fs.h>
80#include <linux/time.h>
81#include <linux/security.h>
82#include <linux/syscalls.h>
83#include <linux/audit.h>
84#include <linux/capability.h>
85#include <linux/seq_file.h>
86#include <linux/rwsem.h>
87#include <linux/nsproxy.h>
88#include <linux/ipc_namespace.h>
89
90#include <asm/uaccess.h>
91#include "util.h"
92
93#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
94
95#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
96#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
97
98static int newary(struct ipc_namespace *, struct ipc_params *);
99static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
100#ifdef CONFIG_PROC_FS
101static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
102#endif
103
104#define SEMMSL_FAST 256 /* 512 bytes on stack */
105#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
106
107/*
108 * linked list protection:
109 * sem_undo.id_next,
110 * sem_array.sem_pending{,last},
111 * sem_array.sem_undo: sem_lock() for read/write
112 * sem_undo.proc_next: only "current" is allowed to read/write that field.
113 *
114 */
115
116#define sc_semmsl sem_ctls[0]
117#define sc_semmns sem_ctls[1]
118#define sc_semopm sem_ctls[2]
119#define sc_semmni sem_ctls[3]
120
121void sem_init_ns(struct ipc_namespace *ns)
122{
123    ns->sc_semmsl = SEMMSL;
124    ns->sc_semmns = SEMMNS;
125    ns->sc_semopm = SEMOPM;
126    ns->sc_semmni = SEMMNI;
127    ns->used_sems = 0;
128    ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
129}
130
131#ifdef CONFIG_IPC_NS
132void sem_exit_ns(struct ipc_namespace *ns)
133{
134    free_ipcs(ns, &sem_ids(ns), freeary);
135    idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
136}
137#endif
138
139void __init sem_init (void)
140{
141    sem_init_ns(&init_ipc_ns);
142    ipc_init_proc_interface("sysvipc/sem",
143                " key semid perms nsems uid gid cuid cgid otime ctime\n",
144                IPC_SEM_IDS, sysvipc_sem_proc_show);
145}
146
147/*
148 * sem_lock_(check_) routines are called in the paths where the rw_mutex
149 * is not held.
150 */
151static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
152{
153    struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
154
155    if (IS_ERR(ipcp))
156        return (struct sem_array *)ipcp;
157
158    return container_of(ipcp, struct sem_array, sem_perm);
159}
160
161static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
162                        int id)
163{
164    struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
165
166    if (IS_ERR(ipcp))
167        return (struct sem_array *)ipcp;
168
169    return container_of(ipcp, struct sem_array, sem_perm);
170}
171
172static inline void sem_lock_and_putref(struct sem_array *sma)
173{
174    ipc_lock_by_ptr(&sma->sem_perm);
175    ipc_rcu_putref(sma);
176}
177
178static inline void sem_getref_and_unlock(struct sem_array *sma)
179{
180    ipc_rcu_getref(sma);
181    ipc_unlock(&(sma)->sem_perm);
182}
183
184static inline void sem_putref(struct sem_array *sma)
185{
186    ipc_lock_by_ptr(&sma->sem_perm);
187    ipc_rcu_putref(sma);
188    ipc_unlock(&(sma)->sem_perm);
189}
190
191static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
192{
193    ipc_rmid(&sem_ids(ns), &s->sem_perm);
194}
195
196/*
197 * Lockless wakeup algorithm:
198 * Without the check/retry algorithm a lockless wakeup is possible:
199 * - queue.status is initialized to -EINTR before blocking.
200 * - wakeup is performed by
201 * * unlinking the queue entry from sma->sem_pending
202 * * setting queue.status to IN_WAKEUP
203 * This is the notification for the blocked thread that a
204 * result value is imminent.
205 * * call wake_up_process
206 * * set queue.status to the final value.
207 * - the previously blocked thread checks queue.status:
208 * * if it's IN_WAKEUP, then it must wait until the value changes
209 * * if it's not -EINTR, then the operation was completed by
210 * update_queue. semtimedop can return queue.status without
211 * performing any operation on the sem array.
212 * * otherwise it must acquire the spinlock and check what's up.
213 *
214 * The two-stage algorithm is necessary to protect against the following
215 * races:
216 * - if queue.status is set after wake_up_process, then the woken up idle
217 * thread could race forward and try (and fail) to acquire sma->lock
218 * before update_queue had a chance to set queue.status
219 * - if queue.status is written before wake_up_process and if the
220 * blocked process is woken up by a signal between writing
221 * queue.status and the wake_up_process, then the woken up
222 * process could return from semtimedop and die by calling
223 * sys_exit before wake_up_process is called. Then wake_up_process
224 * will oops, because the task structure is already invalid.
225 * (yes, this happened on s390 with sysv msg).
226 *
227 */
228#define IN_WAKEUP 1
229
230/**
231 * newary - Create a new semaphore set
232 * @ns: namespace
233 * @params: ptr to the structure that contains key, semflg and nsems
234 *
235 * Called with sem_ids.rw_mutex held (as a writer)
236 */
237
238static int newary(struct ipc_namespace *ns, struct ipc_params *params)
239{
240    int id;
241    int retval;
242    struct sem_array *sma;
243    int size;
244    key_t key = params->key;
245    int nsems = params->u.nsems;
246    int semflg = params->flg;
247    int i;
248
249    if (!nsems)
250        return -EINVAL;
251    if (ns->used_sems + nsems > ns->sc_semmns)
252        return -ENOSPC;
253
254    size = sizeof (*sma) + nsems * sizeof (struct sem);
255    sma = ipc_rcu_alloc(size);
256    if (!sma) {
257        return -ENOMEM;
258    }
259    memset (sma, 0, size);
260
261    sma->sem_perm.mode = (semflg & S_IRWXUGO);
262    sma->sem_perm.key = key;
263
264    sma->sem_perm.security = NULL;
265    retval = security_sem_alloc(sma);
266    if (retval) {
267        ipc_rcu_putref(sma);
268        return retval;
269    }
270
271    id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
272    if (id < 0) {
273        security_sem_free(sma);
274        ipc_rcu_putref(sma);
275        return id;
276    }
277    ns->used_sems += nsems;
278
279    sma->sem_base = (struct sem *) &sma[1];
280
281    for (i = 0; i < nsems; i++)
282        INIT_LIST_HEAD(&sma->sem_base[i].sem_pending);
283
284    sma->complex_count = 0;
285    INIT_LIST_HEAD(&sma->sem_pending);
286    INIT_LIST_HEAD(&sma->list_id);
287    sma->sem_nsems = nsems;
288    sma->sem_ctime = get_seconds();
289    sem_unlock(sma);
290
291    return sma->sem_perm.id;
292}
293
294
295/*
296 * Called with sem_ids.rw_mutex and ipcp locked.
297 */
298static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
299{
300    struct sem_array *sma;
301
302    sma = container_of(ipcp, struct sem_array, sem_perm);
303    return security_sem_associate(sma, semflg);
304}
305
306/*
307 * Called with sem_ids.rw_mutex and ipcp locked.
308 */
309static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
310                struct ipc_params *params)
311{
312    struct sem_array *sma;
313
314    sma = container_of(ipcp, struct sem_array, sem_perm);
315    if (params->u.nsems > sma->sem_nsems)
316        return -EINVAL;
317
318    return 0;
319}
320
321SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
322{
323    struct ipc_namespace *ns;
324    struct ipc_ops sem_ops;
325    struct ipc_params sem_params;
326
327    ns = current->nsproxy->ipc_ns;
328
329    if (nsems < 0 || nsems > ns->sc_semmsl)
330        return -EINVAL;
331
332    sem_ops.getnew = newary;
333    sem_ops.associate = sem_security;
334    sem_ops.more_checks = sem_more_checks;
335
336    sem_params.key = key;
337    sem_params.flg = semflg;
338    sem_params.u.nsems = nsems;
339
340    return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
341}
342
343/*
344 * Determine whether a sequence of semaphore operations would succeed
345 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
346 */
347
348static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
349                 int nsops, struct sem_undo *un, int pid)
350{
351    int result, sem_op;
352    struct sembuf *sop;
353    struct sem * curr;
354
355    for (sop = sops; sop < sops + nsops; sop++) {
356        curr = sma->sem_base + sop->sem_num;
357        sem_op = sop->sem_op;
358        result = curr->semval;
359  
360        if (!sem_op && result)
361            goto would_block;
362
363        result += sem_op;
364        if (result < 0)
365            goto would_block;
366        if (result > SEMVMX)
367            goto out_of_range;
368        if (sop->sem_flg & SEM_UNDO) {
369            int undo = un->semadj[sop->sem_num] - sem_op;
370            /*
371              * Exceeding the undo range is an error.
372             */
373            if (undo < (-SEMAEM - 1) || undo > SEMAEM)
374                goto out_of_range;
375        }
376        curr->semval = result;
377    }
378
379    sop--;
380    while (sop >= sops) {
381        sma->sem_base[sop->sem_num].sempid = pid;
382        if (sop->sem_flg & SEM_UNDO)
383            un->semadj[sop->sem_num] -= sop->sem_op;
384        sop--;
385    }
386    
387    return 0;
388
389out_of_range:
390    result = -ERANGE;
391    goto undo;
392
393would_block:
394    if (sop->sem_flg & IPC_NOWAIT)
395        result = -EAGAIN;
396    else
397        result = 1;
398
399undo:
400    sop--;
401    while (sop >= sops) {
402        sma->sem_base[sop->sem_num].semval -= sop->sem_op;
403        sop--;
404    }
405
406    return result;
407}
408
409/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
410 * @q: queue entry that must be signaled
411 * @error: Error value for the signal
412 *
413 * Prepare the wake-up of the queue entry q.
414 */
415static void wake_up_sem_queue_prepare(struct list_head *pt,
416                struct sem_queue *q, int error)
417{
418    if (list_empty(pt)) {
419        /*
420         * Hold preempt off so that we don't get preempted and have the
421         * wakee busy-wait until we're scheduled back on.
422         */
423        preempt_disable();
424    }
425    q->status = IN_WAKEUP;
426    q->pid = error;
427
428    list_add_tail(&q->simple_list, pt);
429}
430
431/**
432 * wake_up_sem_queue_do(pt) - do the actual wake-up
433 * @pt: list of tasks to be woken up
434 *
435 * Do the actual wake-up.
436 * The function is called without any locks held, thus the semaphore array
437 * could be destroyed already and the tasks can disappear as soon as the
438 * status is set to the actual return code.
439 */
440static void wake_up_sem_queue_do(struct list_head *pt)
441{
442    struct sem_queue *q, *t;
443    int did_something;
444
445    did_something = !list_empty(pt);
446    list_for_each_entry_safe(q, t, pt, simple_list) {
447        wake_up_process(q->sleeper);
448        /* q can disappear immediately after writing q->status. */
449        smp_wmb();
450        q->status = q->pid;
451    }
452    if (did_something)
453        preempt_enable();
454}
455
456static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
457{
458    list_del(&q->list);
459    if (q->nsops == 1)
460        list_del(&q->simple_list);
461    else
462        sma->complex_count--;
463}
464
465/** check_restart(sma, q)
466 * @sma: semaphore array
467 * @q: the operation that just completed
468 *
469 * update_queue is O(N^2) when it restarts scanning the whole queue of
470 * waiting operations. Therefore this function checks if the restart is
471 * really necessary. It is called after a previously waiting operation
472 * was completed.
473 */
474static int check_restart(struct sem_array *sma, struct sem_queue *q)
475{
476    struct sem *curr;
477    struct sem_queue *h;
478
479    /* if the operation didn't modify the array, then no restart */
480    if (q->alter == 0)
481        return 0;
482
483    /* pending complex operations are too difficult to analyse */
484    if (sma->complex_count)
485        return 1;
486
487    /* we were a sleeping complex operation. Too difficult */
488    if (q->nsops > 1)
489        return 1;
490
491    curr = sma->sem_base + q->sops[0].sem_num;
492
493    /* No-one waits on this queue */
494    if (list_empty(&curr->sem_pending))
495        return 0;
496
497    /* the new semaphore value */
498    if (curr->semval) {
499        /* It is impossible that someone waits for the new value:
500         * - q is a previously sleeping simple operation that
501         * altered the array. It must be a decrement, because
502         * simple increments never sleep.
503         * - The value is not 0, thus wait-for-zero won't proceed.
504         * - If there are older (higher priority) decrements
505         * in the queue, then they have observed the original
506         * semval value and couldn't proceed. The operation
507         * decremented to value - thus they won't proceed either.
508         */
509        BUG_ON(q->sops[0].sem_op >= 0);
510        return 0;
511    }
512    /*
513     * semval is 0. Check if there are wait-for-zero semops.
514     * They must be the first entries in the per-semaphore simple queue
515     */
516    h = list_first_entry(&curr->sem_pending, struct sem_queue, simple_list);
517    BUG_ON(h->nsops != 1);
518    BUG_ON(h->sops[0].sem_num != q->sops[0].sem_num);
519
520    /* Yes, there is a wait-for-zero semop. Restart */
521    if (h->sops[0].sem_op == 0)
522        return 1;
523
524    /* Again - no-one is waiting for the new value. */
525    return 0;
526}
527
528
529/**
530 * update_queue(sma, semnum): Look for tasks that can be completed.
531 * @sma: semaphore array.
532 * @semnum: semaphore that was modified.
533 * @pt: list head for the tasks that must be woken up.
534 *
535 * update_queue must be called after a semaphore in a semaphore array
536 * was modified. If multiple semaphore were modified, then @semnum
537 * must be set to -1.
538 * The tasks that must be woken up are added to @pt. The return code
539 * is stored in q->pid.
540 * The function return 1 if at least one semop was completed successfully.
541 */
542static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
543{
544    struct sem_queue *q;
545    struct list_head *walk;
546    struct list_head *pending_list;
547    int offset;
548    int semop_completed = 0;
549
550    /* if there are complex operations around, then knowing the semaphore
551     * that was modified doesn't help us. Assume that multiple semaphores
552     * were modified.
553     */
554    if (sma->complex_count)
555        semnum = -1;
556
557    if (semnum == -1) {
558        pending_list = &sma->sem_pending;
559        offset = offsetof(struct sem_queue, list);
560    } else {
561        pending_list = &sma->sem_base[semnum].sem_pending;
562        offset = offsetof(struct sem_queue, simple_list);
563    }
564
565again:
566    walk = pending_list->next;
567    while (walk != pending_list) {
568        int error, restart;
569
570        q = (struct sem_queue *)((char *)walk - offset);
571        walk = walk->next;
572
573        /* If we are scanning the single sop, per-semaphore list of
574         * one semaphore and that semaphore is 0, then it is not
575         * necessary to scan the "alter" entries: simple increments
576         * that affect only one entry succeed immediately and cannot
577         * be in the per semaphore pending queue, and decrements
578         * cannot be successful if the value is already 0.
579         */
580        if (semnum != -1 && sma->sem_base[semnum].semval == 0 &&
581                q->alter)
582            break;
583
584        error = try_atomic_semop(sma, q->sops, q->nsops,
585                     q->undo, q->pid);
586
587        /* Does q->sleeper still need to sleep? */
588        if (error > 0)
589            continue;
590
591        unlink_queue(sma, q);
592
593        if (error) {
594            restart = 0;
595        } else {
596            semop_completed = 1;
597            restart = check_restart(sma, q);
598        }
599
600        wake_up_sem_queue_prepare(pt, q, error);
601        if (restart)
602            goto again;
603    }
604    return semop_completed;
605}
606
607/**
608 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
609 * @sma: semaphore array
610 * @sops: operations that were performed
611 * @nsops: number of operations
612 * @otime: force setting otime
613 * @pt: list head of the tasks that must be woken up.
614 *
615 * do_smart_update() does the required called to update_queue, based on the
616 * actual changes that were performed on the semaphore array.
617 * Note that the function does not do the actual wake-up: the caller is
618 * responsible for calling wake_up_sem_queue_do(@pt).
619 * It is safe to perform this call after dropping all locks.
620 */
621static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
622            int otime, struct list_head *pt)
623{
624    int i;
625
626    if (sma->complex_count || sops == NULL) {
627        if (update_queue(sma, -1, pt))
628            otime = 1;
629        goto done;
630    }
631
632    for (i = 0; i < nsops; i++) {
633        if (sops[i].sem_op > 0 ||
634            (sops[i].sem_op < 0 &&
635                sma->sem_base[sops[i].sem_num].semval == 0))
636            if (update_queue(sma, sops[i].sem_num, pt))
637                otime = 1;
638    }
639done:
640    if (otime)
641        sma->sem_otime = get_seconds();
642}
643
644
645/* The following counts are associated to each semaphore:
646 * semncnt number of tasks waiting on semval being nonzero
647 * semzcnt number of tasks waiting on semval being zero
648 * This model assumes that a task waits on exactly one semaphore.
649 * Since semaphore operations are to be performed atomically, tasks actually
650 * wait on a whole sequence of semaphores simultaneously.
651 * The counts we return here are a rough approximation, but still
652 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
653 */
654static int count_semncnt (struct sem_array * sma, ushort semnum)
655{
656    int semncnt;
657    struct sem_queue * q;
658
659    semncnt = 0;
660    list_for_each_entry(q, &sma->sem_pending, list) {
661        struct sembuf * sops = q->sops;
662        int nsops = q->nsops;
663        int i;
664        for (i = 0; i < nsops; i++)
665            if (sops[i].sem_num == semnum
666                && (sops[i].sem_op < 0)
667                && !(sops[i].sem_flg & IPC_NOWAIT))
668                semncnt++;
669    }
670    return semncnt;
671}
672
673static int count_semzcnt (struct sem_array * sma, ushort semnum)
674{
675    int semzcnt;
676    struct sem_queue * q;
677
678    semzcnt = 0;
679    list_for_each_entry(q, &sma->sem_pending, list) {
680        struct sembuf * sops = q->sops;
681        int nsops = q->nsops;
682        int i;
683        for (i = 0; i < nsops; i++)
684            if (sops[i].sem_num == semnum
685                && (sops[i].sem_op == 0)
686                && !(sops[i].sem_flg & IPC_NOWAIT))
687                semzcnt++;
688    }
689    return semzcnt;
690}
691
692static void free_un(struct rcu_head *head)
693{
694    struct sem_undo *un = container_of(head, struct sem_undo, rcu);
695    kfree(un);
696}
697
698/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
699 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
700 * remains locked on exit.
701 */
702static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
703{
704    struct sem_undo *un, *tu;
705    struct sem_queue *q, *tq;
706    struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
707    struct list_head tasks;
708
709    /* Free the existing undo structures for this semaphore set. */
710    assert_spin_locked(&sma->sem_perm.lock);
711    list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
712        list_del(&un->list_id);
713        spin_lock(&un->ulp->lock);
714        un->semid = -1;
715        list_del_rcu(&un->list_proc);
716        spin_unlock(&un->ulp->lock);
717        call_rcu(&un->rcu, free_un);
718    }
719
720    /* Wake up all pending processes and let them fail with EIDRM. */
721    INIT_LIST_HEAD(&tasks);
722    list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
723        unlink_queue(sma, q);
724        wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
725    }
726
727    /* Remove the semaphore set from the IDR */
728    sem_rmid(ns, sma);
729    sem_unlock(sma);
730
731    wake_up_sem_queue_do(&tasks);
732    ns->used_sems -= sma->sem_nsems;
733    security_sem_free(sma);
734    ipc_rcu_putref(sma);
735}
736
737static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
738{
739    switch(version) {
740    case IPC_64:
741        return copy_to_user(buf, in, sizeof(*in));
742    case IPC_OLD:
743        {
744        struct semid_ds out;
745
746        memset(&out, 0, sizeof(out));
747
748        ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
749
750        out.sem_otime = in->sem_otime;
751        out.sem_ctime = in->sem_ctime;
752        out.sem_nsems = in->sem_nsems;
753
754        return copy_to_user(buf, &out, sizeof(out));
755        }
756    default:
757        return -EINVAL;
758    }
759}
760
761static int semctl_nolock(struct ipc_namespace *ns, int semid,
762             int cmd, int version, union semun arg)
763{
764    int err;
765    struct sem_array *sma;
766
767    switch(cmd) {
768    case IPC_INFO:
769    case SEM_INFO:
770    {
771        struct seminfo seminfo;
772        int max_id;
773
774        err = security_sem_semctl(NULL, cmd);
775        if (err)
776            return err;
777        
778        memset(&seminfo,0,sizeof(seminfo));
779        seminfo.semmni = ns->sc_semmni;
780        seminfo.semmns = ns->sc_semmns;
781        seminfo.semmsl = ns->sc_semmsl;
782        seminfo.semopm = ns->sc_semopm;
783        seminfo.semvmx = SEMVMX;
784        seminfo.semmnu = SEMMNU;
785        seminfo.semmap = SEMMAP;
786        seminfo.semume = SEMUME;
787        down_read(&sem_ids(ns).rw_mutex);
788        if (cmd == SEM_INFO) {
789            seminfo.semusz = sem_ids(ns).in_use;
790            seminfo.semaem = ns->used_sems;
791        } else {
792            seminfo.semusz = SEMUSZ;
793            seminfo.semaem = SEMAEM;
794        }
795        max_id = ipc_get_maxid(&sem_ids(ns));
796        up_read(&sem_ids(ns).rw_mutex);
797        if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
798            return -EFAULT;
799        return (max_id < 0) ? 0: max_id;
800    }
801    case IPC_STAT:
802    case SEM_STAT:
803    {
804        struct semid64_ds tbuf;
805        int id;
806
807        if (cmd == SEM_STAT) {
808            sma = sem_lock(ns, semid);
809            if (IS_ERR(sma))
810                return PTR_ERR(sma);
811            id = sma->sem_perm.id;
812        } else {
813            sma = sem_lock_check(ns, semid);
814            if (IS_ERR(sma))
815                return PTR_ERR(sma);
816            id = 0;
817        }
818
819        err = -EACCES;
820        if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
821            goto out_unlock;
822
823        err = security_sem_semctl(sma, cmd);
824        if (err)
825            goto out_unlock;
826
827        memset(&tbuf, 0, sizeof(tbuf));
828
829        kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
830        tbuf.sem_otime = sma->sem_otime;
831        tbuf.sem_ctime = sma->sem_ctime;
832        tbuf.sem_nsems = sma->sem_nsems;
833        sem_unlock(sma);
834        if (copy_semid_to_user (arg.buf, &tbuf, version))
835            return -EFAULT;
836        return id;
837    }
838    default:
839        return -EINVAL;
840    }
841out_unlock:
842    sem_unlock(sma);
843    return err;
844}
845
846static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
847        int cmd, int version, union semun arg)
848{
849    struct sem_array *sma;
850    struct sem* curr;
851    int err;
852    ushort fast_sem_io[SEMMSL_FAST];
853    ushort* sem_io = fast_sem_io;
854    int nsems;
855    struct list_head tasks;
856
857    sma = sem_lock_check(ns, semid);
858    if (IS_ERR(sma))
859        return PTR_ERR(sma);
860
861    INIT_LIST_HEAD(&tasks);
862    nsems = sma->sem_nsems;
863
864    err = -EACCES;
865    if (ipcperms(ns, &sma->sem_perm,
866            (cmd == SETVAL || cmd == SETALL) ? S_IWUGO : S_IRUGO))
867        goto out_unlock;
868
869    err = security_sem_semctl(sma, cmd);
870    if (err)
871        goto out_unlock;
872
873    err = -EACCES;
874    switch (cmd) {
875    case GETALL:
876    {
877        ushort __user *array = arg.array;
878        int i;
879
880        if(nsems > SEMMSL_FAST) {
881            sem_getref_and_unlock(sma);
882
883            sem_io = ipc_alloc(sizeof(ushort)*nsems);
884            if(sem_io == NULL) {
885                sem_putref(sma);
886                return -ENOMEM;
887            }
888
889            sem_lock_and_putref(sma);
890            if (sma->sem_perm.deleted) {
891                sem_unlock(sma);
892                err = -EIDRM;
893                goto out_free;
894            }
895        }
896
897        for (i = 0; i < sma->sem_nsems; i++)
898            sem_io[i] = sma->sem_base[i].semval;
899        sem_unlock(sma);
900        err = 0;
901        if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
902            err = -EFAULT;
903        goto out_free;
904    }
905    case SETALL:
906    {
907        int i;
908        struct sem_undo *un;
909
910        sem_getref_and_unlock(sma);
911
912        if(nsems > SEMMSL_FAST) {
913            sem_io = ipc_alloc(sizeof(ushort)*nsems);
914            if(sem_io == NULL) {
915                sem_putref(sma);
916                return -ENOMEM;
917            }
918        }
919
920        if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
921            sem_putref(sma);
922            err = -EFAULT;
923            goto out_free;
924        }
925
926        for (i = 0; i < nsems; i++) {
927            if (sem_io[i] > SEMVMX) {
928                sem_putref(sma);
929                err = -ERANGE;
930                goto out_free;
931            }
932        }
933        sem_lock_and_putref(sma);
934        if (sma->sem_perm.deleted) {
935            sem_unlock(sma);
936            err = -EIDRM;
937            goto out_free;
938        }
939
940        for (i = 0; i < nsems; i++)
941            sma->sem_base[i].semval = sem_io[i];
942
943        assert_spin_locked(&sma->sem_perm.lock);
944        list_for_each_entry(un, &sma->list_id, list_id) {
945            for (i = 0; i < nsems; i++)
946                un->semadj[i] = 0;
947        }
948        sma->sem_ctime = get_seconds();
949        /* maybe some queued-up processes were waiting for this */
950        do_smart_update(sma, NULL, 0, 0, &tasks);
951        err = 0;
952        goto out_unlock;
953    }
954    /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
955    }
956    err = -EINVAL;
957    if(semnum < 0 || semnum >= nsems)
958        goto out_unlock;
959
960    curr = &sma->sem_base[semnum];
961
962    switch (cmd) {
963    case GETVAL:
964        err = curr->semval;
965        goto out_unlock;
966    case GETPID:
967        err = curr->sempid;
968        goto out_unlock;
969    case GETNCNT:
970        err = count_semncnt(sma,semnum);
971        goto out_unlock;
972    case GETZCNT:
973        err = count_semzcnt(sma,semnum);
974        goto out_unlock;
975    case SETVAL:
976    {
977        int val = arg.val;
978        struct sem_undo *un;
979
980        err = -ERANGE;
981        if (val > SEMVMX || val < 0)
982            goto out_unlock;
983
984        assert_spin_locked(&sma->sem_perm.lock);
985        list_for_each_entry(un, &sma->list_id, list_id)
986            un->semadj[semnum] = 0;
987
988        curr->semval = val;
989        curr->sempid = task_tgid_vnr(current);
990        sma->sem_ctime = get_seconds();
991        /* maybe some queued-up processes were waiting for this */
992        do_smart_update(sma, NULL, 0, 0, &tasks);
993        err = 0;
994        goto out_unlock;
995    }
996    }
997out_unlock:
998    sem_unlock(sma);
999    wake_up_sem_queue_do(&tasks);
1000
1001out_free:
1002    if(sem_io != fast_sem_io)
1003        ipc_free(sem_io, sizeof(ushort)*nsems);
1004    return err;
1005}
1006
1007static inline unsigned long
1008copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1009{
1010    switch(version) {
1011    case IPC_64:
1012        if (copy_from_user(out, buf, sizeof(*out)))
1013            return -EFAULT;
1014        return 0;
1015    case IPC_OLD:
1016        {
1017        struct semid_ds tbuf_old;
1018
1019        if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1020            return -EFAULT;
1021
1022        out->sem_perm.uid = tbuf_old.sem_perm.uid;
1023        out->sem_perm.gid = tbuf_old.sem_perm.gid;
1024        out->sem_perm.mode = tbuf_old.sem_perm.mode;
1025
1026        return 0;
1027        }
1028    default:
1029        return -EINVAL;
1030    }
1031}
1032
1033/*
1034 * This function handles some semctl commands which require the rw_mutex
1035 * to be held in write mode.
1036 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
1037 */
1038static int semctl_down(struct ipc_namespace *ns, int semid,
1039               int cmd, int version, union semun arg)
1040{
1041    struct sem_array *sma;
1042    int err;
1043    struct semid64_ds semid64;
1044    struct kern_ipc_perm *ipcp;
1045
1046    if(cmd == IPC_SET) {
1047        if (copy_semid_from_user(&semid64, arg.buf, version))
1048            return -EFAULT;
1049    }
1050
1051    ipcp = ipcctl_pre_down(ns, &sem_ids(ns), semid, cmd,
1052                   &semid64.sem_perm, 0);
1053    if (IS_ERR(ipcp))
1054        return PTR_ERR(ipcp);
1055
1056    sma = container_of(ipcp, struct sem_array, sem_perm);
1057
1058    err = security_sem_semctl(sma, cmd);
1059    if (err)
1060        goto out_unlock;
1061
1062    switch(cmd){
1063    case IPC_RMID:
1064        freeary(ns, ipcp);
1065        goto out_up;
1066    case IPC_SET:
1067        ipc_update_perm(&semid64.sem_perm, ipcp);
1068        sma->sem_ctime = get_seconds();
1069        break;
1070    default:
1071        err = -EINVAL;
1072    }
1073
1074out_unlock:
1075    sem_unlock(sma);
1076out_up:
1077    up_write(&sem_ids(ns).rw_mutex);
1078    return err;
1079}
1080
1081SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg)
1082{
1083    int err = -EINVAL;
1084    int version;
1085    struct ipc_namespace *ns;
1086
1087    if (semid < 0)
1088        return -EINVAL;
1089
1090    version = ipc_parse_version(&cmd);
1091    ns = current->nsproxy->ipc_ns;
1092
1093    switch(cmd) {
1094    case IPC_INFO:
1095    case SEM_INFO:
1096    case IPC_STAT:
1097    case SEM_STAT:
1098        err = semctl_nolock(ns, semid, cmd, version, arg);
1099        return err;
1100    case GETALL:
1101    case GETVAL:
1102    case GETPID:
1103    case GETNCNT:
1104    case GETZCNT:
1105    case SETVAL:
1106    case SETALL:
1107        err = semctl_main(ns,semid,semnum,cmd,version,arg);
1108        return err;
1109    case IPC_RMID:
1110    case IPC_SET:
1111        err = semctl_down(ns, semid, cmd, version, arg);
1112        return err;
1113    default:
1114        return -EINVAL;
1115    }
1116}
1117#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1118asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
1119{
1120    return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg);
1121}
1122SYSCALL_ALIAS(sys_semctl, SyS_semctl);
1123#endif
1124
1125/* If the task doesn't already have a undo_list, then allocate one
1126 * here. We guarantee there is only one thread using this undo list,
1127 * and current is THE ONE
1128 *
1129 * If this allocation and assignment succeeds, but later
1130 * portions of this code fail, there is no need to free the sem_undo_list.
1131 * Just let it stay associated with the task, and it'll be freed later
1132 * at exit time.
1133 *
1134 * This can block, so callers must hold no locks.
1135 */
1136static inline int get_undo_list(struct sem_undo_list **undo_listp)
1137{
1138    struct sem_undo_list *undo_list;
1139
1140    undo_list = current->sysvsem.undo_list;
1141    if (!undo_list) {
1142        undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1143        if (undo_list == NULL)
1144            return -ENOMEM;
1145        spin_lock_init(&undo_list->lock);
1146        atomic_set(&undo_list->refcnt, 1);
1147        INIT_LIST_HEAD(&undo_list->list_proc);
1148
1149        current->sysvsem.undo_list = undo_list;
1150    }
1151    *undo_listp = undo_list;
1152    return 0;
1153}
1154
1155static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1156{
1157    struct sem_undo *un;
1158
1159    list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1160        if (un->semid == semid)
1161            return un;
1162    }
1163    return NULL;
1164}
1165
1166static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1167{
1168    struct sem_undo *un;
1169
1170      assert_spin_locked(&ulp->lock);
1171
1172    un = __lookup_undo(ulp, semid);
1173    if (un) {
1174        list_del_rcu(&un->list_proc);
1175        list_add_rcu(&un->list_proc, &ulp->list_proc);
1176    }
1177    return un;
1178}
1179
1180/**
1181 * find_alloc_undo - Lookup (and if not present create) undo array
1182 * @ns: namespace
1183 * @semid: semaphore array id
1184 *
1185 * The function looks up (and if not present creates) the undo structure.
1186 * The size of the undo structure depends on the size of the semaphore
1187 * array, thus the alloc path is not that straightforward.
1188 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1189 * performs a rcu_read_lock().
1190 */
1191static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1192{
1193    struct sem_array *sma;
1194    struct sem_undo_list *ulp;
1195    struct sem_undo *un, *new;
1196    int nsems;
1197    int error;
1198
1199    error = get_undo_list(&ulp);
1200    if (error)
1201        return ERR_PTR(error);
1202
1203    rcu_read_lock();
1204    spin_lock(&ulp->lock);
1205    un = lookup_undo(ulp, semid);
1206    spin_unlock(&ulp->lock);
1207    if (likely(un!=NULL))
1208        goto out;
1209    rcu_read_unlock();
1210
1211    /* no undo structure around - allocate one. */
1212    /* step 1: figure out the size of the semaphore array */
1213    sma = sem_lock_check(ns, semid);
1214    if (IS_ERR(sma))
1215        return ERR_CAST(sma);
1216
1217    nsems = sma->sem_nsems;
1218    sem_getref_and_unlock(sma);
1219
1220    /* step 2: allocate new undo structure */
1221    new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1222    if (!new) {
1223        sem_putref(sma);
1224        return ERR_PTR(-ENOMEM);
1225    }
1226
1227    /* step 3: Acquire the lock on semaphore array */
1228    sem_lock_and_putref(sma);
1229    if (sma->sem_perm.deleted) {
1230        sem_unlock(sma);
1231        kfree(new);
1232        un = ERR_PTR(-EIDRM);
1233        goto out;
1234    }
1235    spin_lock(&ulp->lock);
1236
1237    /*
1238     * step 4: check for races: did someone else allocate the undo struct?
1239     */
1240    un = lookup_undo(ulp, semid);
1241    if (un) {
1242        kfree(new);
1243        goto success;
1244    }
1245    /* step 5: initialize & link new undo structure */
1246    new->semadj = (short *) &new[1];
1247    new->ulp = ulp;
1248    new->semid = semid;
1249    assert_spin_locked(&ulp->lock);
1250    list_add_rcu(&new->list_proc, &ulp->list_proc);
1251    assert_spin_locked(&sma->sem_perm.lock);
1252    list_add(&new->list_id, &sma->list_id);
1253    un = new;
1254
1255success:
1256    spin_unlock(&ulp->lock);
1257    rcu_read_lock();
1258    sem_unlock(sma);
1259out:
1260    return un;
1261}
1262
1263
1264/**
1265 * get_queue_result - Retrieve the result code from sem_queue
1266 * @q: Pointer to queue structure
1267 *
1268 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1269 * q->status, then we must loop until the value is replaced with the final
1270 * value: This may happen if a task is woken up by an unrelated event (e.g.
1271 * signal) and in parallel the task is woken up by another task because it got
1272 * the requested semaphores.
1273 *
1274 * The function can be called with or without holding the semaphore spinlock.
1275 */
1276static int get_queue_result(struct sem_queue *q)
1277{
1278    int error;
1279
1280    error = q->status;
1281    while (unlikely(error == IN_WAKEUP)) {
1282        cpu_relax();
1283        error = q->status;
1284    }
1285
1286    return error;
1287}
1288
1289
1290SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1291        unsigned, nsops, const struct timespec __user *, timeout)
1292{
1293    int error = -EINVAL;
1294    struct sem_array *sma;
1295    struct sembuf fast_sops[SEMOPM_FAST];
1296    struct sembuf* sops = fast_sops, *sop;
1297    struct sem_undo *un;
1298    int undos = 0, alter = 0, max;
1299    struct sem_queue queue;
1300    unsigned long jiffies_left = 0;
1301    struct ipc_namespace *ns;
1302    struct list_head tasks;
1303
1304    ns = current->nsproxy->ipc_ns;
1305
1306    if (nsops < 1 || semid < 0)
1307        return -EINVAL;
1308    if (nsops > ns->sc_semopm)
1309        return -E2BIG;
1310    if(nsops > SEMOPM_FAST) {
1311        sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1312        if(sops==NULL)
1313            return -ENOMEM;
1314    }
1315    if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1316        error=-EFAULT;
1317        goto out_free;
1318    }
1319    if (timeout) {
1320        struct timespec _timeout;
1321        if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1322            error = -EFAULT;
1323            goto out_free;
1324        }
1325        if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1326            _timeout.tv_nsec >= 1000000000L) {
1327            error = -EINVAL;
1328            goto out_free;
1329        }
1330        jiffies_left = timespec_to_jiffies(&_timeout);
1331    }
1332    max = 0;
1333    for (sop = sops; sop < sops + nsops; sop++) {
1334        if (sop->sem_num >= max)
1335            max = sop->sem_num;
1336        if (sop->sem_flg & SEM_UNDO)
1337            undos = 1;
1338        if (sop->sem_op != 0)
1339            alter = 1;
1340    }
1341
1342    if (undos) {
1343        un = find_alloc_undo(ns, semid);
1344        if (IS_ERR(un)) {
1345            error = PTR_ERR(un);
1346            goto out_free;
1347        }
1348    } else
1349        un = NULL;
1350
1351    INIT_LIST_HEAD(&tasks);
1352
1353    sma = sem_lock_check(ns, semid);
1354    if (IS_ERR(sma)) {
1355        if (un)
1356            rcu_read_unlock();
1357        error = PTR_ERR(sma);
1358        goto out_free;
1359    }
1360
1361    /*
1362     * semid identifiers are not unique - find_alloc_undo may have
1363     * allocated an undo structure, it was invalidated by an RMID
1364     * and now a new array with received the same id. Check and fail.
1365     * This case can be detected checking un->semid. The existence of
1366     * "un" itself is guaranteed by rcu.
1367     */
1368    error = -EIDRM;
1369    if (un) {
1370        if (un->semid == -1) {
1371            rcu_read_unlock();
1372            goto out_unlock_free;
1373        } else {
1374            /*
1375             * rcu lock can be released, "un" cannot disappear:
1376             * - sem_lock is acquired, thus IPC_RMID is
1377             * impossible.
1378             * - exit_sem is impossible, it always operates on
1379             * current (or a dead task).
1380             */
1381
1382            rcu_read_unlock();
1383        }
1384    }
1385
1386    error = -EFBIG;
1387    if (max >= sma->sem_nsems)
1388        goto out_unlock_free;
1389
1390    error = -EACCES;
1391    if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
1392        goto out_unlock_free;
1393
1394    error = security_sem_semop(sma, sops, nsops, alter);
1395    if (error)
1396        goto out_unlock_free;
1397
1398    error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
1399    if (error <= 0) {
1400        if (alter && error == 0)
1401            do_smart_update(sma, sops, nsops, 1, &tasks);
1402
1403        goto out_unlock_free;
1404    }
1405
1406    /* We need to sleep on this operation, so we put the current
1407     * task into the pending queue and go to sleep.
1408     */
1409        
1410    queue.sops = sops;
1411    queue.nsops = nsops;
1412    queue.undo = un;
1413    queue.pid = task_tgid_vnr(current);
1414    queue.alter = alter;
1415    if (alter)
1416        list_add_tail(&queue.list, &sma->sem_pending);
1417    else
1418        list_add(&queue.list, &sma->sem_pending);
1419
1420    if (nsops == 1) {
1421        struct sem *curr;
1422        curr = &sma->sem_base[sops->sem_num];
1423
1424        if (alter)
1425            list_add_tail(&queue.simple_list, &curr->sem_pending);
1426        else
1427            list_add(&queue.simple_list, &curr->sem_pending);
1428    } else {
1429        INIT_LIST_HEAD(&queue.simple_list);
1430        sma->complex_count++;
1431    }
1432
1433    queue.status = -EINTR;
1434    queue.sleeper = current;
1435    current->state = TASK_INTERRUPTIBLE;
1436    sem_unlock(sma);
1437
1438    if (timeout)
1439        jiffies_left = schedule_timeout(jiffies_left);
1440    else
1441        schedule();
1442
1443    error = get_queue_result(&queue);
1444
1445    if (error != -EINTR) {
1446        /* fast path: update_queue already obtained all requested
1447         * resources.
1448         * Perform a smp_mb(): User space could assume that semop()
1449         * is a memory barrier: Without the mb(), the cpu could
1450         * speculatively read in user space stale data that was
1451         * overwritten by the previous owner of the semaphore.
1452         */
1453        smp_mb();
1454
1455        goto out_free;
1456    }
1457
1458    sma = sem_lock(ns, semid);
1459    if (IS_ERR(sma)) {
1460        error = -EIDRM;
1461        goto out_free;
1462    }
1463
1464    error = get_queue_result(&queue);
1465
1466    /*
1467     * If queue.status != -EINTR we are woken up by another process
1468     */
1469
1470    if (error != -EINTR) {
1471        goto out_unlock_free;
1472    }
1473
1474    /*
1475     * If an interrupt occurred we have to clean up the queue
1476     */
1477    if (timeout && jiffies_left == 0)
1478        error = -EAGAIN;
1479    unlink_queue(sma, &queue);
1480
1481out_unlock_free:
1482    sem_unlock(sma);
1483
1484    wake_up_sem_queue_do(&tasks);
1485out_free:
1486    if(sops != fast_sops)
1487        kfree(sops);
1488    return error;
1489}
1490
1491SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
1492        unsigned, nsops)
1493{
1494    return sys_semtimedop(semid, tsops, nsops, NULL);
1495}
1496
1497/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1498 * parent and child tasks.
1499 */
1500
1501int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1502{
1503    struct sem_undo_list *undo_list;
1504    int error;
1505
1506    if (clone_flags & CLONE_SYSVSEM) {
1507        error = get_undo_list(&undo_list);
1508        if (error)
1509            return error;
1510        atomic_inc(&undo_list->refcnt);
1511        tsk->sysvsem.undo_list = undo_list;
1512    } else
1513        tsk->sysvsem.undo_list = NULL;
1514
1515    return 0;
1516}
1517
1518/*
1519 * add semadj values to semaphores, free undo structures.
1520 * undo structures are not freed when semaphore arrays are destroyed
1521 * so some of them may be out of date.
1522 * IMPLEMENTATION NOTE: There is some confusion over whether the
1523 * set of adjustments that needs to be done should be done in an atomic
1524 * manner or not. That is, if we are attempting to decrement the semval
1525 * should we queue up and wait until we can do so legally?
1526 * The original implementation attempted to do this (queue and wait).
1527 * The current implementation does not do so. The POSIX standard
1528 * and SVID should be consulted to determine what behavior is mandated.
1529 */
1530void exit_sem(struct task_struct *tsk)
1531{
1532    struct sem_undo_list *ulp;
1533
1534    ulp = tsk->sysvsem.undo_list;
1535    if (!ulp)
1536        return;
1537    tsk->sysvsem.undo_list = NULL;
1538
1539    if (!atomic_dec_and_test(&ulp->refcnt))
1540        return;
1541
1542    for (;;) {
1543        struct sem_array *sma;
1544        struct sem_undo *un;
1545        struct list_head tasks;
1546        int semid;
1547        int i;
1548
1549        rcu_read_lock();
1550        un = list_entry_rcu(ulp->list_proc.next,
1551                    struct sem_undo, list_proc);
1552        if (&un->list_proc == &ulp->list_proc)
1553            semid = -1;
1554         else
1555            semid = un->semid;
1556        rcu_read_unlock();
1557
1558        if (semid == -1)
1559            break;
1560
1561        sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);
1562
1563        /* exit_sem raced with IPC_RMID, nothing to do */
1564        if (IS_ERR(sma))
1565            continue;
1566
1567        un = __lookup_undo(ulp, semid);
1568        if (un == NULL) {
1569            /* exit_sem raced with IPC_RMID+semget() that created
1570             * exactly the same semid. Nothing to do.
1571             */
1572            sem_unlock(sma);
1573            continue;
1574        }
1575
1576        /* remove un from the linked lists */
1577        assert_spin_locked(&sma->sem_perm.lock);
1578        list_del(&un->list_id);
1579
1580        spin_lock(&ulp->lock);
1581        list_del_rcu(&un->list_proc);
1582        spin_unlock(&ulp->lock);
1583
1584        /* perform adjustments registered in un */
1585        for (i = 0; i < sma->sem_nsems; i++) {
1586            struct sem * semaphore = &sma->sem_base[i];
1587            if (un->semadj[i]) {
1588                semaphore->semval += un->semadj[i];
1589                /*
1590                 * Range checks of the new semaphore value,
1591                 * not defined by sus:
1592                 * - Some unices ignore the undo entirely
1593                 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1594                 * - some cap the value (e.g. FreeBSD caps
1595                 * at 0, but doesn't enforce SEMVMX)
1596                 *
1597                 * Linux caps the semaphore value, both at 0
1598                 * and at SEMVMX.
1599                 *
1600                 * Manfred <manfred@colorfullife.com>
1601                 */
1602                if (semaphore->semval < 0)
1603                    semaphore->semval = 0;
1604                if (semaphore->semval > SEMVMX)
1605                    semaphore->semval = SEMVMX;
1606                semaphore->sempid = task_tgid_vnr(current);
1607            }
1608        }
1609        /* maybe some queued-up processes were waiting for this */
1610        INIT_LIST_HEAD(&tasks);
1611        do_smart_update(sma, NULL, 0, 1, &tasks);
1612        sem_unlock(sma);
1613        wake_up_sem_queue_do(&tasks);
1614
1615        call_rcu(&un->rcu, free_un);
1616    }
1617    kfree(ulp);
1618}
1619
1620#ifdef CONFIG_PROC_FS
1621static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
1622{
1623    struct sem_array *sma = it;
1624
1625    return seq_printf(s,
1626              "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
1627              sma->sem_perm.key,
1628              sma->sem_perm.id,
1629              sma->sem_perm.mode,
1630              sma->sem_nsems,
1631              sma->sem_perm.uid,
1632              sma->sem_perm.gid,
1633              sma->sem_perm.cuid,
1634              sma->sem_perm.cgid,
1635              sma->sem_otime,
1636              sma->sem_ctime);
1637}
1638#endif
1639

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