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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/ipc/sem.c
3 * Copyright (C) 1992 Krishna Balasubramanian
4 * Copyright (C) 1995 Eric Schenk, Bruno Haible
5 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07006 * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
7 *
8 * SMP-threaded, sysctl's added
Christian Kujau624dffc2006-01-15 02:43:54 +01009 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
Linus Torvalds1da177e2005-04-16 15:20:36 -070010 * Enforced range limit on SEM_UNDO
Alan Cox046c6882009-01-05 14:06:29 +000011 * (c) 2001 Red Hat Inc
Linus Torvalds1da177e2005-04-16 15:20:36 -070012 * Lockless wakeup
13 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
Manfred Spraulc5cf6352010-05-26 14:43:43 -070014 * Further wakeup optimizations, documentation
15 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
Steve Grubb073115d2006-04-02 17:07:33 -040016 *
17 * support for audit of ipc object properties and permission changes
18 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
Kirill Korotaeve3893532006-10-02 02:18:22 -070019 *
20 * namespaces support
21 * OpenVZ, SWsoft Inc.
22 * Pavel Emelianov <xemul@openvz.org>
Manfred Spraulc5cf6352010-05-26 14:43:43 -070023 *
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.
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 */
75
Linus Torvalds1da177e2005-04-16 15:20:36 -070076#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>
Linus Torvalds1da177e2005-04-16 15:20:36 -070081#include <linux/security.h>
82#include <linux/syscalls.h>
83#include <linux/audit.h>
Randy.Dunlapc59ede72006-01-11 12:17:46 -080084#include <linux/capability.h>
Mike Waychison19b49462005-09-06 15:17:10 -070085#include <linux/seq_file.h>
Nadia Derbey3e148c72007-10-18 23:40:54 -070086#include <linux/rwsem.h>
Kirill Korotaeve3893532006-10-02 02:18:22 -070087#include <linux/nsproxy.h>
Pavel Emelyanovae5e1b22008-02-08 04:18:22 -080088#include <linux/ipc_namespace.h>
Ingo Molnar5f921ae2006-03-26 01:37:17 -080089
Linus Torvalds1da177e2005-04-16 15:20:36 -070090#include <asm/uaccess.h>
91#include "util.h"
92
Manfred Spraule57940d2011-11-02 13:38:54 -070093/* One semaphore structure for each semaphore in the system. */
94struct sem {
95 int semval; /* current value */
96 int sempid; /* pid of last operation */
97 struct list_head sem_pending; /* pending single-sop operations */
98};
99
100/* One queue for each sleeping process in the system. */
101struct sem_queue {
102 struct list_head simple_list; /* queue of pending operations */
103 struct list_head list; /* queue of pending operations */
104 struct task_struct *sleeper; /* this process */
105 struct sem_undo *undo; /* undo structure */
106 int pid; /* process id of requesting process */
107 int status; /* completion status of operation */
108 struct sembuf *sops; /* array of pending operations */
109 int nsops; /* number of operations */
110 int alter; /* does *sops alter the array? */
111};
112
113/* Each task has a list of undo requests. They are executed automatically
114 * when the process exits.
115 */
116struct sem_undo {
117 struct list_head list_proc; /* per-process list: *
118 * all undos from one process
119 * rcu protected */
120 struct rcu_head rcu; /* rcu struct for sem_undo */
121 struct sem_undo_list *ulp; /* back ptr to sem_undo_list */
122 struct list_head list_id; /* per semaphore array list:
123 * all undos for one array */
124 int semid; /* semaphore set identifier */
125 short *semadj; /* array of adjustments */
126 /* one per semaphore */
127};
128
129/* sem_undo_list controls shared access to the list of sem_undo structures
130 * that may be shared among all a CLONE_SYSVSEM task group.
131 */
132struct sem_undo_list {
133 atomic_t refcnt;
134 spinlock_t lock;
135 struct list_head list_proc;
136};
137
138
Pierre Peiffered2ddbf2008-02-08 04:18:57 -0800139#define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS])
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140
Kirill Korotaeve3893532006-10-02 02:18:22 -0700141#define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm)
Nadia Derbey1b531f22007-10-18 23:40:55 -0700142#define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700144static int newary(struct ipc_namespace *, struct ipc_params *);
Pierre Peiffer01b8b072008-02-08 04:18:57 -0800145static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146#ifdef CONFIG_PROC_FS
Mike Waychison19b49462005-09-06 15:17:10 -0700147static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148#endif
149
150#define SEMMSL_FAST 256 /* 512 bytes on stack */
151#define SEMOPM_FAST 64 /* ~ 372 bytes on stack */
152
153/*
154 * linked list protection:
155 * sem_undo.id_next,
156 * sem_array.sem_pending{,last},
157 * sem_array.sem_undo: sem_lock() for read/write
158 * sem_undo.proc_next: only "current" is allowed to read/write that field.
159 *
160 */
161
Kirill Korotaeve3893532006-10-02 02:18:22 -0700162#define sc_semmsl sem_ctls[0]
163#define sc_semmns sem_ctls[1]
164#define sc_semopm sem_ctls[2]
165#define sc_semmni sem_ctls[3]
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166
Pierre Peiffered2ddbf2008-02-08 04:18:57 -0800167void sem_init_ns(struct ipc_namespace *ns)
Kirill Korotaeve3893532006-10-02 02:18:22 -0700168{
Kirill Korotaeve3893532006-10-02 02:18:22 -0700169 ns->sc_semmsl = SEMMSL;
170 ns->sc_semmns = SEMMNS;
171 ns->sc_semopm = SEMOPM;
172 ns->sc_semmni = SEMMNI;
173 ns->used_sems = 0;
Pierre Peiffered2ddbf2008-02-08 04:18:57 -0800174 ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
Kirill Korotaeve3893532006-10-02 02:18:22 -0700175}
176
Pavel Emelyanovae5e1b22008-02-08 04:18:22 -0800177#ifdef CONFIG_IPC_NS
Kirill Korotaeve3893532006-10-02 02:18:22 -0700178void sem_exit_ns(struct ipc_namespace *ns)
179{
Pierre Peiffer01b8b072008-02-08 04:18:57 -0800180 free_ipcs(ns, &sem_ids(ns), freeary);
Serge E. Hallyn7d6feeb2009-12-15 16:47:27 -0800181 idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
Kirill Korotaeve3893532006-10-02 02:18:22 -0700182}
Pavel Emelyanovae5e1b22008-02-08 04:18:22 -0800183#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184
185void __init sem_init (void)
186{
Pierre Peiffered2ddbf2008-02-08 04:18:57 -0800187 sem_init_ns(&init_ipc_ns);
Mike Waychison19b49462005-09-06 15:17:10 -0700188 ipc_init_proc_interface("sysvipc/sem",
189 " key semid perms nsems uid gid cuid cgid otime ctime\n",
Kirill Korotaeve3893532006-10-02 02:18:22 -0700190 IPC_SEM_IDS, sysvipc_sem_proc_show);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700191}
192
Nadia Derbey3e148c72007-10-18 23:40:54 -0700193/*
Nadia Derbey3e148c72007-10-18 23:40:54 -0700194 * sem_lock_(check_) routines are called in the paths where the rw_mutex
195 * is not held.
196 */
Nadia Derbey023a5352007-10-18 23:40:51 -0700197static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
198{
Nadia Derbey03f02c72007-10-18 23:40:51 -0700199 struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);
200
Pierre Peifferb1ed88b2008-02-06 01:36:23 -0800201 if (IS_ERR(ipcp))
202 return (struct sem_array *)ipcp;
203
Nadia Derbey03f02c72007-10-18 23:40:51 -0700204 return container_of(ipcp, struct sem_array, sem_perm);
Nadia Derbey023a5352007-10-18 23:40:51 -0700205}
206
207static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
208 int id)
209{
Nadia Derbey03f02c72007-10-18 23:40:51 -0700210 struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);
211
Pierre Peifferb1ed88b2008-02-06 01:36:23 -0800212 if (IS_ERR(ipcp))
213 return (struct sem_array *)ipcp;
214
Nadia Derbey03f02c72007-10-18 23:40:51 -0700215 return container_of(ipcp, struct sem_array, sem_perm);
Nadia Derbey023a5352007-10-18 23:40:51 -0700216}
217
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700218static inline void sem_lock_and_putref(struct sem_array *sma)
219{
220 ipc_lock_by_ptr(&sma->sem_perm);
221 ipc_rcu_putref(sma);
222}
223
224static inline void sem_getref_and_unlock(struct sem_array *sma)
225{
226 ipc_rcu_getref(sma);
227 ipc_unlock(&(sma)->sem_perm);
228}
229
230static inline void sem_putref(struct sem_array *sma)
231{
232 ipc_lock_by_ptr(&sma->sem_perm);
233 ipc_rcu_putref(sma);
234 ipc_unlock(&(sma)->sem_perm);
235}
236
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700237static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
238{
239 ipc_rmid(&sem_ids(ns), &s->sem_perm);
240}
241
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242/*
243 * Lockless wakeup algorithm:
244 * Without the check/retry algorithm a lockless wakeup is possible:
245 * - queue.status is initialized to -EINTR before blocking.
246 * - wakeup is performed by
247 * * unlinking the queue entry from sma->sem_pending
248 * * setting queue.status to IN_WAKEUP
249 * This is the notification for the blocked thread that a
250 * result value is imminent.
251 * * call wake_up_process
252 * * set queue.status to the final value.
253 * - the previously blocked thread checks queue.status:
254 * * if it's IN_WAKEUP, then it must wait until the value changes
255 * * if it's not -EINTR, then the operation was completed by
256 * update_queue. semtimedop can return queue.status without
Ingo Molnar5f921ae2006-03-26 01:37:17 -0800257 * performing any operation on the sem array.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258 * * otherwise it must acquire the spinlock and check what's up.
259 *
260 * The two-stage algorithm is necessary to protect against the following
261 * races:
262 * - if queue.status is set after wake_up_process, then the woken up idle
263 * thread could race forward and try (and fail) to acquire sma->lock
264 * before update_queue had a chance to set queue.status
265 * - if queue.status is written before wake_up_process and if the
266 * blocked process is woken up by a signal between writing
267 * queue.status and the wake_up_process, then the woken up
268 * process could return from semtimedop and die by calling
269 * sys_exit before wake_up_process is called. Then wake_up_process
270 * will oops, because the task structure is already invalid.
271 * (yes, this happened on s390 with sysv msg).
272 *
273 */
274#define IN_WAKEUP 1
275
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700276/**
277 * newary - Create a new semaphore set
278 * @ns: namespace
279 * @params: ptr to the structure that contains key, semflg and nsems
280 *
Nadia Derbey3e148c72007-10-18 23:40:54 -0700281 * Called with sem_ids.rw_mutex held (as a writer)
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700282 */
283
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700284static int newary(struct ipc_namespace *ns, struct ipc_params *params)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285{
286 int id;
287 int retval;
288 struct sem_array *sma;
289 int size;
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700290 key_t key = params->key;
291 int nsems = params->u.nsems;
292 int semflg = params->flg;
Manfred Spraulb97e8202009-12-15 16:47:32 -0800293 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294
295 if (!nsems)
296 return -EINVAL;
Kirill Korotaeve3893532006-10-02 02:18:22 -0700297 if (ns->used_sems + nsems > ns->sc_semmns)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700298 return -ENOSPC;
299
300 size = sizeof (*sma) + nsems * sizeof (struct sem);
301 sma = ipc_rcu_alloc(size);
302 if (!sma) {
303 return -ENOMEM;
304 }
305 memset (sma, 0, size);
306
307 sma->sem_perm.mode = (semflg & S_IRWXUGO);
308 sma->sem_perm.key = key;
309
310 sma->sem_perm.security = NULL;
311 retval = security_sem_alloc(sma);
312 if (retval) {
313 ipc_rcu_putref(sma);
314 return retval;
315 }
316
Kirill Korotaeve3893532006-10-02 02:18:22 -0700317 id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
Pierre Peiffer283bb7f2007-10-18 23:40:57 -0700318 if (id < 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700319 security_sem_free(sma);
320 ipc_rcu_putref(sma);
Pierre Peiffer283bb7f2007-10-18 23:40:57 -0700321 return id;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322 }
Kirill Korotaeve3893532006-10-02 02:18:22 -0700323 ns->used_sems += nsems;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700324
325 sma->sem_base = (struct sem *) &sma[1];
Manfred Spraulb97e8202009-12-15 16:47:32 -0800326
327 for (i = 0; i < nsems; i++)
328 INIT_LIST_HEAD(&sma->sem_base[i].sem_pending);
329
330 sma->complex_count = 0;
Manfred Spraula1193f82008-07-25 01:48:06 -0700331 INIT_LIST_HEAD(&sma->sem_pending);
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700332 INIT_LIST_HEAD(&sma->list_id);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700333 sma->sem_nsems = nsems;
334 sma->sem_ctime = get_seconds();
335 sem_unlock(sma);
336
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700337 return sma->sem_perm.id;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700338}
339
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700340
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700341/*
Nadia Derbey3e148c72007-10-18 23:40:54 -0700342 * Called with sem_ids.rw_mutex and ipcp locked.
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700343 */
Nadia Derbey03f02c72007-10-18 23:40:51 -0700344static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700345{
Nadia Derbey03f02c72007-10-18 23:40:51 -0700346 struct sem_array *sma;
347
348 sma = container_of(ipcp, struct sem_array, sem_perm);
349 return security_sem_associate(sma, semflg);
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700350}
351
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700352/*
Nadia Derbey3e148c72007-10-18 23:40:54 -0700353 * Called with sem_ids.rw_mutex and ipcp locked.
Nadia Derbeyf4566f02007-10-18 23:40:53 -0700354 */
Nadia Derbey03f02c72007-10-18 23:40:51 -0700355static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
356 struct ipc_params *params)
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700357{
Nadia Derbey03f02c72007-10-18 23:40:51 -0700358 struct sem_array *sma;
359
360 sma = container_of(ipcp, struct sem_array, sem_perm);
361 if (params->u.nsems > sma->sem_nsems)
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700362 return -EINVAL;
363
364 return 0;
365}
366
Heiko Carstensd5460c92009-01-14 14:14:27 +0100367SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700368{
Kirill Korotaeve3893532006-10-02 02:18:22 -0700369 struct ipc_namespace *ns;
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700370 struct ipc_ops sem_ops;
371 struct ipc_params sem_params;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372
Kirill Korotaeve3893532006-10-02 02:18:22 -0700373 ns = current->nsproxy->ipc_ns;
374
375 if (nsems < 0 || nsems > ns->sc_semmsl)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 return -EINVAL;
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700377
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700378 sem_ops.getnew = newary;
379 sem_ops.associate = sem_security;
380 sem_ops.more_checks = sem_more_checks;
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700381
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700382 sem_params.key = key;
383 sem_params.flg = semflg;
384 sem_params.u.nsems = nsems;
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700385
Nadia Derbey7748dbf2007-10-18 23:40:49 -0700386 return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387}
388
Linus Torvalds1da177e2005-04-16 15:20:36 -0700389/*
390 * Determine whether a sequence of semaphore operations would succeed
391 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
392 */
393
394static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
395 int nsops, struct sem_undo *un, int pid)
396{
397 int result, sem_op;
398 struct sembuf *sop;
399 struct sem * curr;
400
401 for (sop = sops; sop < sops + nsops; sop++) {
402 curr = sma->sem_base + sop->sem_num;
403 sem_op = sop->sem_op;
404 result = curr->semval;
405
406 if (!sem_op && result)
407 goto would_block;
408
409 result += sem_op;
410 if (result < 0)
411 goto would_block;
412 if (result > SEMVMX)
413 goto out_of_range;
414 if (sop->sem_flg & SEM_UNDO) {
415 int undo = un->semadj[sop->sem_num] - sem_op;
416 /*
417 * Exceeding the undo range is an error.
418 */
419 if (undo < (-SEMAEM - 1) || undo > SEMAEM)
420 goto out_of_range;
421 }
422 curr->semval = result;
423 }
424
425 sop--;
426 while (sop >= sops) {
427 sma->sem_base[sop->sem_num].sempid = pid;
428 if (sop->sem_flg & SEM_UNDO)
429 un->semadj[sop->sem_num] -= sop->sem_op;
430 sop--;
431 }
432
Linus Torvalds1da177e2005-04-16 15:20:36 -0700433 return 0;
434
435out_of_range:
436 result = -ERANGE;
437 goto undo;
438
439would_block:
440 if (sop->sem_flg & IPC_NOWAIT)
441 result = -EAGAIN;
442 else
443 result = 1;
444
445undo:
446 sop--;
447 while (sop >= sops) {
448 sma->sem_base[sop->sem_num].semval -= sop->sem_op;
449 sop--;
450 }
451
452 return result;
453}
454
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700455/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
456 * @q: queue entry that must be signaled
457 * @error: Error value for the signal
458 *
459 * Prepare the wake-up of the queue entry q.
Nick Piggind4212092009-12-15 16:47:30 -0800460 */
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700461static void wake_up_sem_queue_prepare(struct list_head *pt,
462 struct sem_queue *q, int error)
Nick Piggind4212092009-12-15 16:47:30 -0800463{
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700464 if (list_empty(pt)) {
465 /*
466 * Hold preempt off so that we don't get preempted and have the
467 * wakee busy-wait until we're scheduled back on.
468 */
469 preempt_disable();
470 }
Nick Piggind4212092009-12-15 16:47:30 -0800471 q->status = IN_WAKEUP;
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700472 q->pid = error;
473
474 list_add_tail(&q->simple_list, pt);
475}
476
477/**
478 * wake_up_sem_queue_do(pt) - do the actual wake-up
479 * @pt: list of tasks to be woken up
480 *
481 * Do the actual wake-up.
482 * The function is called without any locks held, thus the semaphore array
483 * could be destroyed already and the tasks can disappear as soon as the
484 * status is set to the actual return code.
485 */
486static void wake_up_sem_queue_do(struct list_head *pt)
487{
488 struct sem_queue *q, *t;
489 int did_something;
490
491 did_something = !list_empty(pt);
492 list_for_each_entry_safe(q, t, pt, simple_list) {
493 wake_up_process(q->sleeper);
494 /* q can disappear immediately after writing q->status. */
495 smp_wmb();
496 q->status = q->pid;
497 }
498 if (did_something)
499 preempt_enable();
Nick Piggind4212092009-12-15 16:47:30 -0800500}
501
Manfred Spraulb97e8202009-12-15 16:47:32 -0800502static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
503{
504 list_del(&q->list);
505 if (q->nsops == 1)
506 list_del(&q->simple_list);
507 else
508 sma->complex_count--;
509}
510
Manfred Spraulfd5db422010-05-26 14:43:40 -0700511/** check_restart(sma, q)
512 * @sma: semaphore array
513 * @q: the operation that just completed
514 *
515 * update_queue is O(N^2) when it restarts scanning the whole queue of
516 * waiting operations. Therefore this function checks if the restart is
517 * really necessary. It is called after a previously waiting operation
518 * was completed.
519 */
520static int check_restart(struct sem_array *sma, struct sem_queue *q)
521{
522 struct sem *curr;
523 struct sem_queue *h;
524
525 /* if the operation didn't modify the array, then no restart */
526 if (q->alter == 0)
527 return 0;
528
529 /* pending complex operations are too difficult to analyse */
530 if (sma->complex_count)
531 return 1;
532
533 /* we were a sleeping complex operation. Too difficult */
534 if (q->nsops > 1)
535 return 1;
536
537 curr = sma->sem_base + q->sops[0].sem_num;
538
539 /* No-one waits on this queue */
540 if (list_empty(&curr->sem_pending))
541 return 0;
542
543 /* the new semaphore value */
544 if (curr->semval) {
545 /* It is impossible that someone waits for the new value:
546 * - q is a previously sleeping simple operation that
547 * altered the array. It must be a decrement, because
548 * simple increments never sleep.
549 * - The value is not 0, thus wait-for-zero won't proceed.
550 * - If there are older (higher priority) decrements
551 * in the queue, then they have observed the original
552 * semval value and couldn't proceed. The operation
553 * decremented to value - thus they won't proceed either.
554 */
555 BUG_ON(q->sops[0].sem_op >= 0);
556 return 0;
557 }
558 /*
559 * semval is 0. Check if there are wait-for-zero semops.
560 * They must be the first entries in the per-semaphore simple queue
561 */
562 h = list_first_entry(&curr->sem_pending, struct sem_queue, simple_list);
563 BUG_ON(h->nsops != 1);
564 BUG_ON(h->sops[0].sem_num != q->sops[0].sem_num);
565
566 /* Yes, there is a wait-for-zero semop. Restart */
567 if (h->sops[0].sem_op == 0)
568 return 1;
569
570 /* Again - no-one is waiting for the new value. */
571 return 0;
572}
573
Manfred Spraul636c6be2009-12-15 16:47:33 -0800574
575/**
576 * update_queue(sma, semnum): Look for tasks that can be completed.
577 * @sma: semaphore array.
578 * @semnum: semaphore that was modified.
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700579 * @pt: list head for the tasks that must be woken up.
Manfred Spraul636c6be2009-12-15 16:47:33 -0800580 *
581 * update_queue must be called after a semaphore in a semaphore array
582 * was modified. If multiple semaphore were modified, then @semnum
583 * must be set to -1.
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700584 * The tasks that must be woken up are added to @pt. The return code
585 * is stored in q->pid.
586 * The function return 1 if at least one semop was completed successfully.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700587 */
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700588static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589{
Manfred Spraul636c6be2009-12-15 16:47:33 -0800590 struct sem_queue *q;
591 struct list_head *walk;
592 struct list_head *pending_list;
593 int offset;
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700594 int semop_completed = 0;
Manfred Spraul636c6be2009-12-15 16:47:33 -0800595
596 /* if there are complex operations around, then knowing the semaphore
597 * that was modified doesn't help us. Assume that multiple semaphores
598 * were modified.
599 */
600 if (sma->complex_count)
601 semnum = -1;
602
603 if (semnum == -1) {
604 pending_list = &sma->sem_pending;
605 offset = offsetof(struct sem_queue, list);
606 } else {
607 pending_list = &sma->sem_base[semnum].sem_pending;
608 offset = offsetof(struct sem_queue, simple_list);
609 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700610
Nick Piggin9cad2002009-12-15 16:47:29 -0800611again:
Manfred Spraul636c6be2009-12-15 16:47:33 -0800612 walk = pending_list->next;
613 while (walk != pending_list) {
Manfred Spraulfd5db422010-05-26 14:43:40 -0700614 int error, restart;
Manfred Spraul636c6be2009-12-15 16:47:33 -0800615
616 q = (struct sem_queue *)((char *)walk - offset);
617 walk = walk->next;
Nick Piggin9cad2002009-12-15 16:47:29 -0800618
Manfred Sprauld987f8b22009-12-15 16:47:34 -0800619 /* If we are scanning the single sop, per-semaphore list of
620 * one semaphore and that semaphore is 0, then it is not
621 * necessary to scan the "alter" entries: simple increments
622 * that affect only one entry succeed immediately and cannot
623 * be in the per semaphore pending queue, and decrements
624 * cannot be successful if the value is already 0.
625 */
626 if (semnum != -1 && sma->sem_base[semnum].semval == 0 &&
627 q->alter)
628 break;
629
Linus Torvalds1da177e2005-04-16 15:20:36 -0700630 error = try_atomic_semop(sma, q->sops, q->nsops,
631 q->undo, q->pid);
632
633 /* Does q->sleeper still need to sleep? */
Nick Piggin9cad2002009-12-15 16:47:29 -0800634 if (error > 0)
635 continue;
Manfred Spraula1193f82008-07-25 01:48:06 -0700636
Manfred Spraulb97e8202009-12-15 16:47:32 -0800637 unlink_queue(sma, q);
Manfred Spraula1193f82008-07-25 01:48:06 -0700638
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700639 if (error) {
Manfred Spraulfd5db422010-05-26 14:43:40 -0700640 restart = 0;
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700641 } else {
642 semop_completed = 1;
Manfred Spraulfd5db422010-05-26 14:43:40 -0700643 restart = check_restart(sma, q);
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700644 }
Manfred Spraulfd5db422010-05-26 14:43:40 -0700645
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700646 wake_up_sem_queue_prepare(pt, q, error);
Manfred Spraulfd5db422010-05-26 14:43:40 -0700647 if (restart)
Nick Piggin9cad2002009-12-15 16:47:29 -0800648 goto again;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700649 }
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700650 return semop_completed;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700651}
652
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700653/**
654 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
Manfred Spraulfd5db422010-05-26 14:43:40 -0700655 * @sma: semaphore array
656 * @sops: operations that were performed
657 * @nsops: number of operations
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700658 * @otime: force setting otime
659 * @pt: list head of the tasks that must be woken up.
Manfred Spraulfd5db422010-05-26 14:43:40 -0700660 *
661 * do_smart_update() does the required called to update_queue, based on the
662 * actual changes that were performed on the semaphore array.
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700663 * Note that the function does not do the actual wake-up: the caller is
664 * responsible for calling wake_up_sem_queue_do(@pt).
665 * It is safe to perform this call after dropping all locks.
Manfred Spraulfd5db422010-05-26 14:43:40 -0700666 */
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700667static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
668 int otime, struct list_head *pt)
Manfred Spraulfd5db422010-05-26 14:43:40 -0700669{
670 int i;
671
672 if (sma->complex_count || sops == NULL) {
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700673 if (update_queue(sma, -1, pt))
674 otime = 1;
675 goto done;
Manfred Spraulfd5db422010-05-26 14:43:40 -0700676 }
677
678 for (i = 0; i < nsops; i++) {
679 if (sops[i].sem_op > 0 ||
680 (sops[i].sem_op < 0 &&
681 sma->sem_base[sops[i].sem_num].semval == 0))
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700682 if (update_queue(sma, sops[i].sem_num, pt))
683 otime = 1;
Manfred Spraulfd5db422010-05-26 14:43:40 -0700684 }
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700685done:
686 if (otime)
687 sma->sem_otime = get_seconds();
Manfred Spraulfd5db422010-05-26 14:43:40 -0700688}
689
690
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691/* The following counts are associated to each semaphore:
692 * semncnt number of tasks waiting on semval being nonzero
693 * semzcnt number of tasks waiting on semval being zero
694 * This model assumes that a task waits on exactly one semaphore.
695 * Since semaphore operations are to be performed atomically, tasks actually
696 * wait on a whole sequence of semaphores simultaneously.
697 * The counts we return here are a rough approximation, but still
698 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
699 */
700static int count_semncnt (struct sem_array * sma, ushort semnum)
701{
702 int semncnt;
703 struct sem_queue * q;
704
705 semncnt = 0;
Manfred Spraula1193f82008-07-25 01:48:06 -0700706 list_for_each_entry(q, &sma->sem_pending, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700707 struct sembuf * sops = q->sops;
708 int nsops = q->nsops;
709 int i;
710 for (i = 0; i < nsops; i++)
711 if (sops[i].sem_num == semnum
712 && (sops[i].sem_op < 0)
713 && !(sops[i].sem_flg & IPC_NOWAIT))
714 semncnt++;
715 }
716 return semncnt;
717}
Manfred Spraula1193f82008-07-25 01:48:06 -0700718
Linus Torvalds1da177e2005-04-16 15:20:36 -0700719static int count_semzcnt (struct sem_array * sma, ushort semnum)
720{
721 int semzcnt;
722 struct sem_queue * q;
723
724 semzcnt = 0;
Manfred Spraula1193f82008-07-25 01:48:06 -0700725 list_for_each_entry(q, &sma->sem_pending, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700726 struct sembuf * sops = q->sops;
727 int nsops = q->nsops;
728 int i;
729 for (i = 0; i < nsops; i++)
730 if (sops[i].sem_num == semnum
731 && (sops[i].sem_op == 0)
732 && !(sops[i].sem_flg & IPC_NOWAIT))
733 semzcnt++;
734 }
735 return semzcnt;
736}
737
Nadia Derbey3e148c72007-10-18 23:40:54 -0700738/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
739 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
740 * remains locked on exit.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700741 */
Pierre Peiffer01b8b072008-02-08 04:18:57 -0800742static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700743{
Manfred Spraul380af1b2008-07-25 01:48:06 -0700744 struct sem_undo *un, *tu;
745 struct sem_queue *q, *tq;
Pierre Peiffer01b8b072008-02-08 04:18:57 -0800746 struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700747 struct list_head tasks;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748
Manfred Spraul380af1b2008-07-25 01:48:06 -0700749 /* Free the existing undo structures for this semaphore set. */
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700750 assert_spin_locked(&sma->sem_perm.lock);
Manfred Spraul380af1b2008-07-25 01:48:06 -0700751 list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
752 list_del(&un->list_id);
753 spin_lock(&un->ulp->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700754 un->semid = -1;
Manfred Spraul380af1b2008-07-25 01:48:06 -0700755 list_del_rcu(&un->list_proc);
756 spin_unlock(&un->ulp->lock);
Lai Jiangshan693a8b62011-03-18 12:09:35 +0800757 kfree_rcu(un, rcu);
Manfred Spraul380af1b2008-07-25 01:48:06 -0700758 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700759
760 /* Wake up all pending processes and let them fail with EIDRM. */
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700761 INIT_LIST_HEAD(&tasks);
Manfred Spraul380af1b2008-07-25 01:48:06 -0700762 list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
Manfred Spraulb97e8202009-12-15 16:47:32 -0800763 unlink_queue(sma, q);
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700764 wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700765 }
766
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700767 /* Remove the semaphore set from the IDR */
768 sem_rmid(ns, sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700769 sem_unlock(sma);
770
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700771 wake_up_sem_queue_do(&tasks);
Kirill Korotaeve3893532006-10-02 02:18:22 -0700772 ns->used_sems -= sma->sem_nsems;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773 security_sem_free(sma);
774 ipc_rcu_putref(sma);
775}
776
777static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
778{
779 switch(version) {
780 case IPC_64:
781 return copy_to_user(buf, in, sizeof(*in));
782 case IPC_OLD:
783 {
784 struct semid_ds out;
785
Dan Rosenberg982f7c22010-09-30 15:15:31 -0700786 memset(&out, 0, sizeof(out));
787
Linus Torvalds1da177e2005-04-16 15:20:36 -0700788 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
789
790 out.sem_otime = in->sem_otime;
791 out.sem_ctime = in->sem_ctime;
792 out.sem_nsems = in->sem_nsems;
793
794 return copy_to_user(buf, &out, sizeof(out));
795 }
796 default:
797 return -EINVAL;
798 }
799}
800
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -0800801static int semctl_nolock(struct ipc_namespace *ns, int semid,
802 int cmd, int version, union semun arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700803{
Amerigo Wange5cc9c72009-12-15 16:47:35 -0800804 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700805 struct sem_array *sma;
806
807 switch(cmd) {
808 case IPC_INFO:
809 case SEM_INFO:
810 {
811 struct seminfo seminfo;
812 int max_id;
813
814 err = security_sem_semctl(NULL, cmd);
815 if (err)
816 return err;
817
818 memset(&seminfo,0,sizeof(seminfo));
Kirill Korotaeve3893532006-10-02 02:18:22 -0700819 seminfo.semmni = ns->sc_semmni;
820 seminfo.semmns = ns->sc_semmns;
821 seminfo.semmsl = ns->sc_semmsl;
822 seminfo.semopm = ns->sc_semopm;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700823 seminfo.semvmx = SEMVMX;
824 seminfo.semmnu = SEMMNU;
825 seminfo.semmap = SEMMAP;
826 seminfo.semume = SEMUME;
Nadia Derbey3e148c72007-10-18 23:40:54 -0700827 down_read(&sem_ids(ns).rw_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700828 if (cmd == SEM_INFO) {
Kirill Korotaeve3893532006-10-02 02:18:22 -0700829 seminfo.semusz = sem_ids(ns).in_use;
830 seminfo.semaem = ns->used_sems;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700831 } else {
832 seminfo.semusz = SEMUSZ;
833 seminfo.semaem = SEMAEM;
834 }
Nadia Derbey7ca7e562007-10-18 23:40:48 -0700835 max_id = ipc_get_maxid(&sem_ids(ns));
Nadia Derbey3e148c72007-10-18 23:40:54 -0700836 up_read(&sem_ids(ns).rw_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700837 if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo)))
838 return -EFAULT;
839 return (max_id < 0) ? 0: max_id;
840 }
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -0800841 case IPC_STAT:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700842 case SEM_STAT:
843 {
844 struct semid64_ds tbuf;
845 int id;
846
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -0800847 if (cmd == SEM_STAT) {
848 sma = sem_lock(ns, semid);
849 if (IS_ERR(sma))
850 return PTR_ERR(sma);
851 id = sma->sem_perm.id;
852 } else {
853 sma = sem_lock_check(ns, semid);
854 if (IS_ERR(sma))
855 return PTR_ERR(sma);
856 id = 0;
857 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700858
859 err = -EACCES;
Serge E. Hallynb0e77592011-03-23 16:43:24 -0700860 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700861 goto out_unlock;
862
863 err = security_sem_semctl(sma, cmd);
864 if (err)
865 goto out_unlock;
866
Nadia Derbey023a5352007-10-18 23:40:51 -0700867 memset(&tbuf, 0, sizeof(tbuf));
868
Linus Torvalds1da177e2005-04-16 15:20:36 -0700869 kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
870 tbuf.sem_otime = sma->sem_otime;
871 tbuf.sem_ctime = sma->sem_ctime;
872 tbuf.sem_nsems = sma->sem_nsems;
873 sem_unlock(sma);
874 if (copy_semid_to_user (arg.buf, &tbuf, version))
875 return -EFAULT;
876 return id;
877 }
878 default:
879 return -EINVAL;
880 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700881out_unlock:
882 sem_unlock(sma);
883 return err;
884}
885
Kirill Korotaeve3893532006-10-02 02:18:22 -0700886static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
887 int cmd, int version, union semun arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700888{
889 struct sem_array *sma;
890 struct sem* curr;
891 int err;
892 ushort fast_sem_io[SEMMSL_FAST];
893 ushort* sem_io = fast_sem_io;
894 int nsems;
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700895 struct list_head tasks;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700896
Nadia Derbey023a5352007-10-18 23:40:51 -0700897 sma = sem_lock_check(ns, semid);
898 if (IS_ERR(sma))
899 return PTR_ERR(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700900
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700901 INIT_LIST_HEAD(&tasks);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700902 nsems = sma->sem_nsems;
903
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904 err = -EACCES;
Serge E. Hallynb0e77592011-03-23 16:43:24 -0700905 if (ipcperms(ns, &sma->sem_perm,
906 (cmd == SETVAL || cmd == SETALL) ? S_IWUGO : S_IRUGO))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700907 goto out_unlock;
908
909 err = security_sem_semctl(sma, cmd);
910 if (err)
911 goto out_unlock;
912
913 err = -EACCES;
914 switch (cmd) {
915 case GETALL:
916 {
917 ushort __user *array = arg.array;
918 int i;
919
920 if(nsems > SEMMSL_FAST) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700921 sem_getref_and_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700922
923 sem_io = ipc_alloc(sizeof(ushort)*nsems);
924 if(sem_io == NULL) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700925 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700926 return -ENOMEM;
927 }
928
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700929 sem_lock_and_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700930 if (sma->sem_perm.deleted) {
931 sem_unlock(sma);
932 err = -EIDRM;
933 goto out_free;
934 }
935 }
936
937 for (i = 0; i < sma->sem_nsems; i++)
938 sem_io[i] = sma->sem_base[i].semval;
939 sem_unlock(sma);
940 err = 0;
941 if(copy_to_user(array, sem_io, nsems*sizeof(ushort)))
942 err = -EFAULT;
943 goto out_free;
944 }
945 case SETALL:
946 {
947 int i;
948 struct sem_undo *un;
949
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700950 sem_getref_and_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700951
952 if(nsems > SEMMSL_FAST) {
953 sem_io = ipc_alloc(sizeof(ushort)*nsems);
954 if(sem_io == NULL) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700955 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700956 return -ENOMEM;
957 }
958 }
959
960 if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700961 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700962 err = -EFAULT;
963 goto out_free;
964 }
965
966 for (i = 0; i < nsems; i++) {
967 if (sem_io[i] > SEMVMX) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700968 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700969 err = -ERANGE;
970 goto out_free;
971 }
972 }
Pierre Peiffer6ff37972008-04-29 01:00:46 -0700973 sem_lock_and_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974 if (sma->sem_perm.deleted) {
975 sem_unlock(sma);
976 err = -EIDRM;
977 goto out_free;
978 }
979
980 for (i = 0; i < nsems; i++)
981 sma->sem_base[i].semval = sem_io[i];
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700982
983 assert_spin_locked(&sma->sem_perm.lock);
984 list_for_each_entry(un, &sma->list_id, list_id) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700985 for (i = 0; i < nsems; i++)
986 un->semadj[i] = 0;
Manfred Spraul4daa28f2008-07-25 01:48:04 -0700987 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700988 sma->sem_ctime = get_seconds();
989 /* maybe some queued-up processes were waiting for this */
Manfred Spraul0a2b9d42010-05-26 14:43:41 -0700990 do_smart_update(sma, NULL, 0, 0, &tasks);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700991 err = 0;
992 goto out_unlock;
993 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700994 /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
995 }
996 err = -EINVAL;
997 if(semnum < 0 || semnum >= nsems)
998 goto out_unlock;
999
1000 curr = &sma->sem_base[semnum];
1001
1002 switch (cmd) {
1003 case GETVAL:
1004 err = curr->semval;
1005 goto out_unlock;
1006 case GETPID:
1007 err = curr->sempid;
1008 goto out_unlock;
1009 case GETNCNT:
1010 err = count_semncnt(sma,semnum);
1011 goto out_unlock;
1012 case GETZCNT:
1013 err = count_semzcnt(sma,semnum);
1014 goto out_unlock;
1015 case SETVAL:
1016 {
1017 int val = arg.val;
1018 struct sem_undo *un;
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001019
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 err = -ERANGE;
1021 if (val > SEMVMX || val < 0)
1022 goto out_unlock;
1023
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001024 assert_spin_locked(&sma->sem_perm.lock);
1025 list_for_each_entry(un, &sma->list_id, list_id)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026 un->semadj[semnum] = 0;
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001027
Linus Torvalds1da177e2005-04-16 15:20:36 -07001028 curr->semval = val;
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001029 curr->sempid = task_tgid_vnr(current);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001030 sma->sem_ctime = get_seconds();
1031 /* maybe some queued-up processes were waiting for this */
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001032 do_smart_update(sma, NULL, 0, 0, &tasks);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033 err = 0;
1034 goto out_unlock;
1035 }
1036 }
1037out_unlock:
1038 sem_unlock(sma);
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001039 wake_up_sem_queue_do(&tasks);
1040
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041out_free:
1042 if(sem_io != fast_sem_io)
1043 ipc_free(sem_io, sizeof(ushort)*nsems);
1044 return err;
1045}
1046
Pierre Peiffer016d7132008-04-29 01:00:50 -07001047static inline unsigned long
1048copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001049{
1050 switch(version) {
1051 case IPC_64:
Pierre Peiffer016d7132008-04-29 01:00:50 -07001052 if (copy_from_user(out, buf, sizeof(*out)))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053 return -EFAULT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055 case IPC_OLD:
1056 {
1057 struct semid_ds tbuf_old;
1058
1059 if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1060 return -EFAULT;
1061
Pierre Peiffer016d7132008-04-29 01:00:50 -07001062 out->sem_perm.uid = tbuf_old.sem_perm.uid;
1063 out->sem_perm.gid = tbuf_old.sem_perm.gid;
1064 out->sem_perm.mode = tbuf_old.sem_perm.mode;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065
1066 return 0;
1067 }
1068 default:
1069 return -EINVAL;
1070 }
1071}
1072
Pierre Peiffer522bb2a2008-04-29 01:00:49 -07001073/*
1074 * This function handles some semctl commands which require the rw_mutex
1075 * to be held in write mode.
1076 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
1077 */
Pierre Peiffer21a48262008-04-29 01:00:49 -07001078static int semctl_down(struct ipc_namespace *ns, int semid,
1079 int cmd, int version, union semun arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001080{
1081 struct sem_array *sma;
1082 int err;
Pierre Peiffer016d7132008-04-29 01:00:50 -07001083 struct semid64_ds semid64;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001084 struct kern_ipc_perm *ipcp;
1085
1086 if(cmd == IPC_SET) {
Pierre Peiffer016d7132008-04-29 01:00:50 -07001087 if (copy_semid_from_user(&semid64, arg.buf, version))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001088 return -EFAULT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001089 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001090
Serge E. Hallynb0e77592011-03-23 16:43:24 -07001091 ipcp = ipcctl_pre_down(ns, &sem_ids(ns), semid, cmd,
1092 &semid64.sem_perm, 0);
Pierre Peiffera5f75e72008-04-29 01:00:54 -07001093 if (IS_ERR(ipcp))
1094 return PTR_ERR(ipcp);
Steve Grubb073115d2006-04-02 17:07:33 -04001095
Pierre Peiffera5f75e72008-04-29 01:00:54 -07001096 sma = container_of(ipcp, struct sem_array, sem_perm);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001097
1098 err = security_sem_semctl(sma, cmd);
1099 if (err)
1100 goto out_unlock;
1101
1102 switch(cmd){
1103 case IPC_RMID:
Pierre Peiffer01b8b072008-02-08 04:18:57 -08001104 freeary(ns, ipcp);
Pierre Peiffer522bb2a2008-04-29 01:00:49 -07001105 goto out_up;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106 case IPC_SET:
Pierre Peiffer8f4a3802008-04-29 01:00:51 -07001107 ipc_update_perm(&semid64.sem_perm, ipcp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001108 sma->sem_ctime = get_seconds();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001109 break;
1110 default:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111 err = -EINVAL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001112 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001113
1114out_unlock:
1115 sem_unlock(sma);
Pierre Peiffer522bb2a2008-04-29 01:00:49 -07001116out_up:
1117 up_write(&sem_ids(ns).rw_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001118 return err;
1119}
1120
Heiko Carstens6673e0c2009-01-14 14:14:02 +01001121SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001122{
1123 int err = -EINVAL;
1124 int version;
Kirill Korotaeve3893532006-10-02 02:18:22 -07001125 struct ipc_namespace *ns;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126
1127 if (semid < 0)
1128 return -EINVAL;
1129
1130 version = ipc_parse_version(&cmd);
Kirill Korotaeve3893532006-10-02 02:18:22 -07001131 ns = current->nsproxy->ipc_ns;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132
1133 switch(cmd) {
1134 case IPC_INFO:
1135 case SEM_INFO:
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -08001136 case IPC_STAT:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001137 case SEM_STAT:
Pierre Peiffer4b9fcb02008-02-08 04:18:56 -08001138 err = semctl_nolock(ns, semid, cmd, version, arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001139 return err;
1140 case GETALL:
1141 case GETVAL:
1142 case GETPID:
1143 case GETNCNT:
1144 case GETZCNT:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 case SETVAL:
1146 case SETALL:
Kirill Korotaeve3893532006-10-02 02:18:22 -07001147 err = semctl_main(ns,semid,semnum,cmd,version,arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148 return err;
1149 case IPC_RMID:
1150 case IPC_SET:
Pierre Peiffer21a48262008-04-29 01:00:49 -07001151 err = semctl_down(ns, semid, cmd, version, arg);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001152 return err;
1153 default:
1154 return -EINVAL;
1155 }
1156}
Heiko Carstens6673e0c2009-01-14 14:14:02 +01001157#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
1158asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg)
1159{
1160 return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg);
1161}
1162SYSCALL_ALIAS(sys_semctl, SyS_semctl);
1163#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -07001164
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165/* If the task doesn't already have a undo_list, then allocate one
1166 * here. We guarantee there is only one thread using this undo list,
1167 * and current is THE ONE
1168 *
1169 * If this allocation and assignment succeeds, but later
1170 * portions of this code fail, there is no need to free the sem_undo_list.
1171 * Just let it stay associated with the task, and it'll be freed later
1172 * at exit time.
1173 *
1174 * This can block, so callers must hold no locks.
1175 */
1176static inline int get_undo_list(struct sem_undo_list **undo_listp)
1177{
1178 struct sem_undo_list *undo_list;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001179
1180 undo_list = current->sysvsem.undo_list;
1181 if (!undo_list) {
Matt Helsley2453a302006-10-02 02:18:25 -07001182 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001183 if (undo_list == NULL)
1184 return -ENOMEM;
Ingo Molnar00a5dfd2005-08-05 23:05:27 +02001185 spin_lock_init(&undo_list->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001186 atomic_set(&undo_list->refcnt, 1);
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001187 INIT_LIST_HEAD(&undo_list->list_proc);
1188
Linus Torvalds1da177e2005-04-16 15:20:36 -07001189 current->sysvsem.undo_list = undo_list;
1190 }
1191 *undo_listp = undo_list;
1192 return 0;
1193}
1194
Nick Pigginbf17bb72009-12-15 16:47:28 -08001195static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001196{
Nick Pigginbf17bb72009-12-15 16:47:28 -08001197 struct sem_undo *un;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001198
Nick Pigginbf17bb72009-12-15 16:47:28 -08001199 list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
1200 if (un->semid == semid)
1201 return un;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001202 }
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001203 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204}
1205
Nick Pigginbf17bb72009-12-15 16:47:28 -08001206static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1207{
1208 struct sem_undo *un;
1209
1210 assert_spin_locked(&ulp->lock);
1211
1212 un = __lookup_undo(ulp, semid);
1213 if (un) {
1214 list_del_rcu(&un->list_proc);
1215 list_add_rcu(&un->list_proc, &ulp->list_proc);
1216 }
1217 return un;
1218}
1219
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001220/**
1221 * find_alloc_undo - Lookup (and if not present create) undo array
1222 * @ns: namespace
1223 * @semid: semaphore array id
1224 *
1225 * The function looks up (and if not present creates) the undo structure.
1226 * The size of the undo structure depends on the size of the semaphore
1227 * array, thus the alloc path is not that straightforward.
Manfred Spraul380af1b2008-07-25 01:48:06 -07001228 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1229 * performs a rcu_read_lock().
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001230 */
1231static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001232{
1233 struct sem_array *sma;
1234 struct sem_undo_list *ulp;
1235 struct sem_undo *un, *new;
1236 int nsems;
1237 int error;
1238
1239 error = get_undo_list(&ulp);
1240 if (error)
1241 return ERR_PTR(error);
1242
Manfred Spraul380af1b2008-07-25 01:48:06 -07001243 rcu_read_lock();
Pierre Peifferc530c6a2007-10-18 23:40:55 -07001244 spin_lock(&ulp->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001245 un = lookup_undo(ulp, semid);
Pierre Peifferc530c6a2007-10-18 23:40:55 -07001246 spin_unlock(&ulp->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001247 if (likely(un!=NULL))
1248 goto out;
Manfred Spraul380af1b2008-07-25 01:48:06 -07001249 rcu_read_unlock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001250
1251 /* no undo structure around - allocate one. */
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001252 /* step 1: figure out the size of the semaphore array */
Nadia Derbey023a5352007-10-18 23:40:51 -07001253 sma = sem_lock_check(ns, semid);
1254 if (IS_ERR(sma))
Julia Lawall4de85cd2010-05-26 14:43:44 -07001255 return ERR_CAST(sma);
Nadia Derbey023a5352007-10-18 23:40:51 -07001256
Linus Torvalds1da177e2005-04-16 15:20:36 -07001257 nsems = sma->sem_nsems;
Pierre Peiffer6ff37972008-04-29 01:00:46 -07001258 sem_getref_and_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001260 /* step 2: allocate new undo structure */
Burman Yan4668edc2006-12-06 20:38:51 -08001261 new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001262 if (!new) {
Pierre Peiffer6ff37972008-04-29 01:00:46 -07001263 sem_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001264 return ERR_PTR(-ENOMEM);
1265 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266
Manfred Spraul380af1b2008-07-25 01:48:06 -07001267 /* step 3: Acquire the lock on semaphore array */
Pierre Peiffer6ff37972008-04-29 01:00:46 -07001268 sem_lock_and_putref(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001269 if (sma->sem_perm.deleted) {
1270 sem_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271 kfree(new);
1272 un = ERR_PTR(-EIDRM);
1273 goto out;
1274 }
Manfred Spraul380af1b2008-07-25 01:48:06 -07001275 spin_lock(&ulp->lock);
1276
1277 /*
1278 * step 4: check for races: did someone else allocate the undo struct?
1279 */
1280 un = lookup_undo(ulp, semid);
1281 if (un) {
1282 kfree(new);
1283 goto success;
1284 }
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001285 /* step 5: initialize & link new undo structure */
1286 new->semadj = (short *) &new[1];
Manfred Spraul380af1b2008-07-25 01:48:06 -07001287 new->ulp = ulp;
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001288 new->semid = semid;
1289 assert_spin_locked(&ulp->lock);
Manfred Spraul380af1b2008-07-25 01:48:06 -07001290 list_add_rcu(&new->list_proc, &ulp->list_proc);
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001291 assert_spin_locked(&sma->sem_perm.lock);
1292 list_add(&new->list_id, &sma->list_id);
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001293 un = new;
Manfred Spraul380af1b2008-07-25 01:48:06 -07001294
1295success:
1296 spin_unlock(&ulp->lock);
1297 rcu_read_lock();
1298 sem_unlock(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001299out:
1300 return un;
1301}
1302
Manfred Spraulc61284e2010-07-20 13:24:23 -07001303
1304/**
1305 * get_queue_result - Retrieve the result code from sem_queue
1306 * @q: Pointer to queue structure
1307 *
1308 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
1309 * q->status, then we must loop until the value is replaced with the final
1310 * value: This may happen if a task is woken up by an unrelated event (e.g.
1311 * signal) and in parallel the task is woken up by another task because it got
1312 * the requested semaphores.
1313 *
1314 * The function can be called with or without holding the semaphore spinlock.
1315 */
1316static int get_queue_result(struct sem_queue *q)
1317{
1318 int error;
1319
1320 error = q->status;
1321 while (unlikely(error == IN_WAKEUP)) {
1322 cpu_relax();
1323 error = q->status;
1324 }
1325
1326 return error;
1327}
1328
1329
Heiko Carstensd5460c92009-01-14 14:14:27 +01001330SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
1331 unsigned, nsops, const struct timespec __user *, timeout)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001332{
1333 int error = -EINVAL;
1334 struct sem_array *sma;
1335 struct sembuf fast_sops[SEMOPM_FAST];
1336 struct sembuf* sops = fast_sops, *sop;
1337 struct sem_undo *un;
Manfred Spraulb78755a2005-06-23 00:10:06 -07001338 int undos = 0, alter = 0, max;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001339 struct sem_queue queue;
1340 unsigned long jiffies_left = 0;
Kirill Korotaeve3893532006-10-02 02:18:22 -07001341 struct ipc_namespace *ns;
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001342 struct list_head tasks;
Kirill Korotaeve3893532006-10-02 02:18:22 -07001343
1344 ns = current->nsproxy->ipc_ns;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345
1346 if (nsops < 1 || semid < 0)
1347 return -EINVAL;
Kirill Korotaeve3893532006-10-02 02:18:22 -07001348 if (nsops > ns->sc_semopm)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349 return -E2BIG;
1350 if(nsops > SEMOPM_FAST) {
1351 sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
1352 if(sops==NULL)
1353 return -ENOMEM;
1354 }
1355 if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
1356 error=-EFAULT;
1357 goto out_free;
1358 }
1359 if (timeout) {
1360 struct timespec _timeout;
1361 if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
1362 error = -EFAULT;
1363 goto out_free;
1364 }
1365 if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
1366 _timeout.tv_nsec >= 1000000000L) {
1367 error = -EINVAL;
1368 goto out_free;
1369 }
1370 jiffies_left = timespec_to_jiffies(&_timeout);
1371 }
1372 max = 0;
1373 for (sop = sops; sop < sops + nsops; sop++) {
1374 if (sop->sem_num >= max)
1375 max = sop->sem_num;
1376 if (sop->sem_flg & SEM_UNDO)
Manfred Spraulb78755a2005-06-23 00:10:06 -07001377 undos = 1;
1378 if (sop->sem_op != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379 alter = 1;
1380 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001381
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382 if (undos) {
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001383 un = find_alloc_undo(ns, semid);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001384 if (IS_ERR(un)) {
1385 error = PTR_ERR(un);
1386 goto out_free;
1387 }
1388 } else
1389 un = NULL;
1390
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001391 INIT_LIST_HEAD(&tasks);
1392
Nadia Derbey023a5352007-10-18 23:40:51 -07001393 sma = sem_lock_check(ns, semid);
1394 if (IS_ERR(sma)) {
Manfred Spraul380af1b2008-07-25 01:48:06 -07001395 if (un)
1396 rcu_read_unlock();
Nadia Derbey023a5352007-10-18 23:40:51 -07001397 error = PTR_ERR(sma);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001398 goto out_free;
Nadia Derbey023a5352007-10-18 23:40:51 -07001399 }
1400
Linus Torvalds1da177e2005-04-16 15:20:36 -07001401 /*
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001402 * semid identifiers are not unique - find_alloc_undo may have
Linus Torvalds1da177e2005-04-16 15:20:36 -07001403 * allocated an undo structure, it was invalidated by an RMID
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001404 * and now a new array with received the same id. Check and fail.
Lucas De Marchi25985ed2011-03-30 22:57:33 -03001405 * This case can be detected checking un->semid. The existence of
Manfred Spraul380af1b2008-07-25 01:48:06 -07001406 * "un" itself is guaranteed by rcu.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407 */
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001408 error = -EIDRM;
Manfred Spraul380af1b2008-07-25 01:48:06 -07001409 if (un) {
1410 if (un->semid == -1) {
1411 rcu_read_unlock();
1412 goto out_unlock_free;
1413 } else {
1414 /*
1415 * rcu lock can be released, "un" cannot disappear:
1416 * - sem_lock is acquired, thus IPC_RMID is
1417 * impossible.
1418 * - exit_sem is impossible, it always operates on
1419 * current (or a dead task).
1420 */
1421
1422 rcu_read_unlock();
1423 }
1424 }
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001425
Linus Torvalds1da177e2005-04-16 15:20:36 -07001426 error = -EFBIG;
1427 if (max >= sma->sem_nsems)
1428 goto out_unlock_free;
1429
1430 error = -EACCES;
Serge E. Hallynb0e77592011-03-23 16:43:24 -07001431 if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001432 goto out_unlock_free;
1433
1434 error = security_sem_semop(sma, sops, nsops, alter);
1435 if (error)
1436 goto out_unlock_free;
1437
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001438 error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001439 if (error <= 0) {
1440 if (alter && error == 0)
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001441 do_smart_update(sma, sops, nsops, 1, &tasks);
Manfred Spraul636c6be2009-12-15 16:47:33 -08001442
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443 goto out_unlock_free;
1444 }
1445
1446 /* We need to sleep on this operation, so we put the current
1447 * task into the pending queue and go to sleep.
1448 */
1449
Linus Torvalds1da177e2005-04-16 15:20:36 -07001450 queue.sops = sops;
1451 queue.nsops = nsops;
1452 queue.undo = un;
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001453 queue.pid = task_tgid_vnr(current);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001454 queue.alter = alter;
1455 if (alter)
Manfred Spraula1193f82008-07-25 01:48:06 -07001456 list_add_tail(&queue.list, &sma->sem_pending);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001457 else
Manfred Spraula1193f82008-07-25 01:48:06 -07001458 list_add(&queue.list, &sma->sem_pending);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001459
Manfred Spraulb97e8202009-12-15 16:47:32 -08001460 if (nsops == 1) {
1461 struct sem *curr;
1462 curr = &sma->sem_base[sops->sem_num];
1463
1464 if (alter)
1465 list_add_tail(&queue.simple_list, &curr->sem_pending);
1466 else
1467 list_add(&queue.simple_list, &curr->sem_pending);
1468 } else {
1469 INIT_LIST_HEAD(&queue.simple_list);
1470 sma->complex_count++;
1471 }
1472
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 queue.status = -EINTR;
1474 queue.sleeper = current;
Manfred Spraul0b0577f2011-11-02 13:38:52 -07001475
1476sleep_again:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001477 current->state = TASK_INTERRUPTIBLE;
1478 sem_unlock(sma);
1479
1480 if (timeout)
1481 jiffies_left = schedule_timeout(jiffies_left);
1482 else
1483 schedule();
1484
Manfred Spraulc61284e2010-07-20 13:24:23 -07001485 error = get_queue_result(&queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001486
1487 if (error != -EINTR) {
1488 /* fast path: update_queue already obtained all requested
Manfred Spraulc61284e2010-07-20 13:24:23 -07001489 * resources.
1490 * Perform a smp_mb(): User space could assume that semop()
1491 * is a memory barrier: Without the mb(), the cpu could
1492 * speculatively read in user space stale data that was
1493 * overwritten by the previous owner of the semaphore.
1494 */
1495 smp_mb();
1496
Linus Torvalds1da177e2005-04-16 15:20:36 -07001497 goto out_free;
1498 }
1499
Kirill Korotaeve3893532006-10-02 02:18:22 -07001500 sma = sem_lock(ns, semid);
Manfred Sprauld694ad62011-07-25 17:11:47 -07001501
1502 /*
1503 * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
1504 */
1505 error = get_queue_result(&queue);
1506
1507 /*
1508 * Array removed? If yes, leave without sem_unlock().
1509 */
Nadia Derbey023a5352007-10-18 23:40:51 -07001510 if (IS_ERR(sma)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001511 goto out_free;
1512 }
1513
Manfred Spraulc61284e2010-07-20 13:24:23 -07001514
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515 /*
Manfred Sprauld694ad62011-07-25 17:11:47 -07001516 * If queue.status != -EINTR we are woken up by another process.
1517 * Leave without unlink_queue(), but with sem_unlock().
Linus Torvalds1da177e2005-04-16 15:20:36 -07001518 */
Manfred Spraulc61284e2010-07-20 13:24:23 -07001519
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520 if (error != -EINTR) {
1521 goto out_unlock_free;
1522 }
1523
1524 /*
1525 * If an interrupt occurred we have to clean up the queue
1526 */
1527 if (timeout && jiffies_left == 0)
1528 error = -EAGAIN;
Manfred Spraul0b0577f2011-11-02 13:38:52 -07001529
1530 /*
1531 * If the wakeup was spurious, just retry
1532 */
1533 if (error == -EINTR && !signal_pending(current))
1534 goto sleep_again;
1535
Manfred Spraulb97e8202009-12-15 16:47:32 -08001536 unlink_queue(sma, &queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001537
1538out_unlock_free:
1539 sem_unlock(sma);
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001540
1541 wake_up_sem_queue_do(&tasks);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001542out_free:
1543 if(sops != fast_sops)
1544 kfree(sops);
1545 return error;
1546}
1547
Heiko Carstensd5460c92009-01-14 14:14:27 +01001548SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
1549 unsigned, nsops)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001550{
1551 return sys_semtimedop(semid, tsops, nsops, NULL);
1552}
1553
1554/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
1555 * parent and child tasks.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556 */
1557
1558int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
1559{
1560 struct sem_undo_list *undo_list;
1561 int error;
1562
1563 if (clone_flags & CLONE_SYSVSEM) {
1564 error = get_undo_list(&undo_list);
1565 if (error)
1566 return error;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001567 atomic_inc(&undo_list->refcnt);
1568 tsk->sysvsem.undo_list = undo_list;
1569 } else
1570 tsk->sysvsem.undo_list = NULL;
1571
1572 return 0;
1573}
1574
1575/*
1576 * add semadj values to semaphores, free undo structures.
1577 * undo structures are not freed when semaphore arrays are destroyed
1578 * so some of them may be out of date.
1579 * IMPLEMENTATION NOTE: There is some confusion over whether the
1580 * set of adjustments that needs to be done should be done in an atomic
1581 * manner or not. That is, if we are attempting to decrement the semval
1582 * should we queue up and wait until we can do so legally?
1583 * The original implementation attempted to do this (queue and wait).
1584 * The current implementation does not do so. The POSIX standard
1585 * and SVID should be consulted to determine what behavior is mandated.
1586 */
1587void exit_sem(struct task_struct *tsk)
1588{
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001589 struct sem_undo_list *ulp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001590
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001591 ulp = tsk->sysvsem.undo_list;
1592 if (!ulp)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001593 return;
Manfred Spraul9edff4a2008-04-29 01:00:57 -07001594 tsk->sysvsem.undo_list = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001596 if (!atomic_dec_and_test(&ulp->refcnt))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001597 return;
1598
Manfred Spraul380af1b2008-07-25 01:48:06 -07001599 for (;;) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001600 struct sem_array *sma;
Manfred Spraul380af1b2008-07-25 01:48:06 -07001601 struct sem_undo *un;
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001602 struct list_head tasks;
Manfred Spraul380af1b2008-07-25 01:48:06 -07001603 int semid;
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001604 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001605
Manfred Spraul380af1b2008-07-25 01:48:06 -07001606 rcu_read_lock();
Jiri Pirko05725f72009-04-14 20:17:16 +02001607 un = list_entry_rcu(ulp->list_proc.next,
1608 struct sem_undo, list_proc);
Manfred Spraul380af1b2008-07-25 01:48:06 -07001609 if (&un->list_proc == &ulp->list_proc)
1610 semid = -1;
1611 else
1612 semid = un->semid;
1613 rcu_read_unlock();
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001614
Manfred Spraul380af1b2008-07-25 01:48:06 -07001615 if (semid == -1)
1616 break;
1617
1618 sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid);
1619
1620 /* exit_sem raced with IPC_RMID, nothing to do */
Nadia Derbey023a5352007-10-18 23:40:51 -07001621 if (IS_ERR(sma))
Manfred Spraul380af1b2008-07-25 01:48:06 -07001622 continue;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001623
Nick Pigginbf17bb72009-12-15 16:47:28 -08001624 un = __lookup_undo(ulp, semid);
Manfred Spraul380af1b2008-07-25 01:48:06 -07001625 if (un == NULL) {
1626 /* exit_sem raced with IPC_RMID+semget() that created
1627 * exactly the same semid. Nothing to do.
1628 */
1629 sem_unlock(sma);
1630 continue;
1631 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001632
Manfred Spraul380af1b2008-07-25 01:48:06 -07001633 /* remove un from the linked lists */
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001634 assert_spin_locked(&sma->sem_perm.lock);
1635 list_del(&un->list_id);
1636
Manfred Spraul380af1b2008-07-25 01:48:06 -07001637 spin_lock(&ulp->lock);
1638 list_del_rcu(&un->list_proc);
1639 spin_unlock(&ulp->lock);
1640
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001641 /* perform adjustments registered in un */
1642 for (i = 0; i < sma->sem_nsems; i++) {
Ingo Molnar5f921ae2006-03-26 01:37:17 -08001643 struct sem * semaphore = &sma->sem_base[i];
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001644 if (un->semadj[i]) {
1645 semaphore->semval += un->semadj[i];
Linus Torvalds1da177e2005-04-16 15:20:36 -07001646 /*
1647 * Range checks of the new semaphore value,
1648 * not defined by sus:
1649 * - Some unices ignore the undo entirely
1650 * (e.g. HP UX 11i 11.22, Tru64 V5.1)
1651 * - some cap the value (e.g. FreeBSD caps
1652 * at 0, but doesn't enforce SEMVMX)
1653 *
1654 * Linux caps the semaphore value, both at 0
1655 * and at SEMVMX.
1656 *
1657 * Manfred <manfred@colorfullife.com>
1658 */
Ingo Molnar5f921ae2006-03-26 01:37:17 -08001659 if (semaphore->semval < 0)
1660 semaphore->semval = 0;
1661 if (semaphore->semval > SEMVMX)
1662 semaphore->semval = SEMVMX;
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001663 semaphore->sempid = task_tgid_vnr(current);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001664 }
1665 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001666 /* maybe some queued-up processes were waiting for this */
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001667 INIT_LIST_HEAD(&tasks);
1668 do_smart_update(sma, NULL, 0, 1, &tasks);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669 sem_unlock(sma);
Manfred Spraul0a2b9d42010-05-26 14:43:41 -07001670 wake_up_sem_queue_do(&tasks);
Manfred Spraul380af1b2008-07-25 01:48:06 -07001671
Lai Jiangshan693a8b62011-03-18 12:09:35 +08001672 kfree_rcu(un, rcu);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001673 }
Manfred Spraul4daa28f2008-07-25 01:48:04 -07001674 kfree(ulp);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001675}
1676
1677#ifdef CONFIG_PROC_FS
Mike Waychison19b49462005-09-06 15:17:10 -07001678static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001679{
Mike Waychison19b49462005-09-06 15:17:10 -07001680 struct sem_array *sma = it;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681
Mike Waychison19b49462005-09-06 15:17:10 -07001682 return seq_printf(s,
Manfred Spraulb97e8202009-12-15 16:47:32 -08001683 "%10d %10d %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
Mike Waychison19b49462005-09-06 15:17:10 -07001684 sma->sem_perm.key,
Nadia Derbey7ca7e562007-10-18 23:40:48 -07001685 sma->sem_perm.id,
Mike Waychison19b49462005-09-06 15:17:10 -07001686 sma->sem_perm.mode,
1687 sma->sem_nsems,
1688 sma->sem_perm.uid,
1689 sma->sem_perm.gid,
1690 sma->sem_perm.cuid,
1691 sma->sem_perm.cgid,
1692 sma->sem_otime,
1693 sma->sem_ctime);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001694}
1695#endif