| 1 | /* |
| 2 | * linux/ipc/sem.c |
| 3 | * Copyright (C) 1992 Krishna Balasubramanian |
| 4 | * Copyright (C) 1995 Eric Schenk, Bruno Haible |
| 5 | * |
| 6 | * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995): |
| 7 | * This code underwent a massive rewrite in order to solve some problems |
| 8 | * with the original code. In particular the original code failed to |
| 9 | * wake up processes that were waiting for semval to go to 0 if the |
| 10 | * value went to 0 and was then incremented rapidly enough. In solving |
| 11 | * this problem I have also modified the implementation so that it |
| 12 | * processes pending operations in a FIFO manner, thus give a guarantee |
| 13 | * that processes waiting for a lock on the semaphore won't starve |
| 14 | * unless another locking process fails to unlock. |
| 15 | * In addition the following two changes in behavior have been introduced: |
| 16 | * - The original implementation of semop returned the value |
| 17 | * last semaphore element examined on success. This does not |
| 18 | * match the manual page specifications, and effectively |
| 19 | * allows the user to read the semaphore even if they do not |
| 20 | * have read permissions. The implementation now returns 0 |
| 21 | * on success as stated in the manual page. |
| 22 | * - There is some confusion over whether the set of undo adjustments |
| 23 | * to be performed at exit should be done in an atomic manner. |
| 24 | * That is, if we are attempting to decrement the semval should we queue |
| 25 | * up and wait until we can do so legally? |
| 26 | * The original implementation attempted to do this. |
| 27 | * The current implementation does not do so. This is because I don't |
| 28 | * think it is the right thing (TM) to do, and because I couldn't |
| 29 | * see a clean way to get the old behavior with the new design. |
| 30 | * The POSIX standard and SVID should be consulted to determine |
| 31 | * what behavior is mandated. |
| 32 | * |
| 33 | * Further notes on refinement (Christoph Rohland, December 1998): |
| 34 | * - The POSIX standard says, that the undo adjustments simply should |
| 35 | * redo. So the current implementation is o.K. |
| 36 | * - The previous code had two flaws: |
| 37 | * 1) It actively gave the semaphore to the next waiting process |
| 38 | * sleeping on the semaphore. Since this process did not have the |
| 39 | * cpu this led to many unnecessary context switches and bad |
| 40 | * performance. Now we only check which process should be able to |
| 41 | * get the semaphore and if this process wants to reduce some |
| 42 | * semaphore value we simply wake it up without doing the |
| 43 | * operation. So it has to try to get it later. Thus e.g. the |
| 44 | * running process may reacquire the semaphore during the current |
| 45 | * time slice. If it only waits for zero or increases the semaphore, |
| 46 | * we do the operation in advance and wake it up. |
| 47 | * 2) It did not wake up all zero waiting processes. We try to do |
| 48 | * better but only get the semops right which only wait for zero or |
| 49 | * increase. If there are decrement operations in the operations |
| 50 | * array we do the same as before. |
| 51 | * |
| 52 | * With the incarnation of O(1) scheduler, it becomes unnecessary to perform |
| 53 | * check/retry algorithm for waking up blocked processes as the new scheduler |
| 54 | * is better at handling thread switch than the old one. |
| 55 | * |
| 56 | * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com> |
| 57 | * |
| 58 | * SMP-threaded, sysctl's added |
| 59 | * (c) 1999 Manfred Spraul <manfred@colorfullife.com> |
| 60 | * Enforced range limit on SEM_UNDO |
| 61 | * (c) 2001 Red Hat Inc |
| 62 | * Lockless wakeup |
| 63 | * (c) 2003 Manfred Spraul <manfred@colorfullife.com> |
| 64 | * |
| 65 | * support for audit of ipc object properties and permission changes |
| 66 | * Dustin Kirkland <dustin.kirkland@us.ibm.com> |
| 67 | * |
| 68 | * namespaces support |
| 69 | * OpenVZ, SWsoft Inc. |
| 70 | * Pavel Emelianov <xemul@openvz.org> |
| 71 | */ |
| 72 | |
| 73 | #include <linux/slab.h> |
| 74 | #include <linux/spinlock.h> |
| 75 | #include <linux/init.h> |
| 76 | #include <linux/proc_fs.h> |
| 77 | #include <linux/time.h> |
| 78 | #include <linux/security.h> |
| 79 | #include <linux/syscalls.h> |
| 80 | #include <linux/audit.h> |
| 81 | #include <linux/capability.h> |
| 82 | #include <linux/seq_file.h> |
| 83 | #include <linux/rwsem.h> |
| 84 | #include <linux/nsproxy.h> |
| 85 | #include <linux/ipc_namespace.h> |
| 86 | |
| 87 | #include <asm/uaccess.h> |
| 88 | #include "util.h" |
| 89 | |
| 90 | #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS]) |
| 91 | |
| 92 | #define sem_unlock(sma) ipc_unlock(&(sma)->sem_perm) |
| 93 | #define sem_checkid(sma, semid) ipc_checkid(&sma->sem_perm, semid) |
| 94 | |
| 95 | static int newary(struct ipc_namespace *, struct ipc_params *); |
| 96 | static void freeary(struct ipc_namespace *, struct kern_ipc_perm *); |
| 97 | #ifdef CONFIG_PROC_FS |
| 98 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it); |
| 99 | #endif |
| 100 | |
| 101 | #define SEMMSL_FAST 256 /* 512 bytes on stack */ |
| 102 | #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ |
| 103 | |
| 104 | /* |
| 105 | * linked list protection: |
| 106 | * sem_undo.id_next, |
| 107 | * sem_array.sem_pending{,last}, |
| 108 | * sem_array.sem_undo: sem_lock() for read/write |
| 109 | * sem_undo.proc_next: only "current" is allowed to read/write that field. |
| 110 | * |
| 111 | */ |
| 112 | |
| 113 | #define sc_semmsl sem_ctls[0] |
| 114 | #define sc_semmns sem_ctls[1] |
| 115 | #define sc_semopm sem_ctls[2] |
| 116 | #define sc_semmni sem_ctls[3] |
| 117 | |
| 118 | void sem_init_ns(struct ipc_namespace *ns) |
| 119 | { |
| 120 | ns->sc_semmsl = SEMMSL; |
| 121 | ns->sc_semmns = SEMMNS; |
| 122 | ns->sc_semopm = SEMOPM; |
| 123 | ns->sc_semmni = SEMMNI; |
| 124 | ns->used_sems = 0; |
| 125 | ipc_init_ids(&ns->ids[IPC_SEM_IDS]); |
| 126 | } |
| 127 | |
| 128 | #ifdef CONFIG_IPC_NS |
| 129 | void sem_exit_ns(struct ipc_namespace *ns) |
| 130 | { |
| 131 | free_ipcs(ns, &sem_ids(ns), freeary); |
| 132 | } |
| 133 | #endif |
| 134 | |
| 135 | void __init sem_init (void) |
| 136 | { |
| 137 | sem_init_ns(&init_ipc_ns); |
| 138 | ipc_init_proc_interface("sysvipc/sem", |
| 139 | " key semid perms nsems uid gid cuid cgid otime ctime\n", |
| 140 | IPC_SEM_IDS, sysvipc_sem_proc_show); |
| 141 | } |
| 142 | |
| 143 | /* |
| 144 | * sem_lock_(check_) routines are called in the paths where the rw_mutex |
| 145 | * is not held. |
| 146 | */ |
| 147 | static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id) |
| 148 | { |
| 149 | struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id); |
| 150 | |
| 151 | if (IS_ERR(ipcp)) |
| 152 | return (struct sem_array *)ipcp; |
| 153 | |
| 154 | return container_of(ipcp, struct sem_array, sem_perm); |
| 155 | } |
| 156 | |
| 157 | static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns, |
| 158 | int id) |
| 159 | { |
| 160 | struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id); |
| 161 | |
| 162 | if (IS_ERR(ipcp)) |
| 163 | return (struct sem_array *)ipcp; |
| 164 | |
| 165 | return container_of(ipcp, struct sem_array, sem_perm); |
| 166 | } |
| 167 | |
| 168 | static inline void sem_lock_and_putref(struct sem_array *sma) |
| 169 | { |
| 170 | ipc_lock_by_ptr(&sma->sem_perm); |
| 171 | ipc_rcu_putref(sma); |
| 172 | } |
| 173 | |
| 174 | static inline void sem_getref_and_unlock(struct sem_array *sma) |
| 175 | { |
| 176 | ipc_rcu_getref(sma); |
| 177 | ipc_unlock(&(sma)->sem_perm); |
| 178 | } |
| 179 | |
| 180 | static inline void sem_putref(struct sem_array *sma) |
| 181 | { |
| 182 | ipc_lock_by_ptr(&sma->sem_perm); |
| 183 | ipc_rcu_putref(sma); |
| 184 | ipc_unlock(&(sma)->sem_perm); |
| 185 | } |
| 186 | |
| 187 | static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) |
| 188 | { |
| 189 | ipc_rmid(&sem_ids(ns), &s->sem_perm); |
| 190 | } |
| 191 | |
| 192 | /* |
| 193 | * Lockless wakeup algorithm: |
| 194 | * Without the check/retry algorithm a lockless wakeup is possible: |
| 195 | * - queue.status is initialized to -EINTR before blocking. |
| 196 | * - wakeup is performed by |
| 197 | * * unlinking the queue entry from sma->sem_pending |
| 198 | * * setting queue.status to IN_WAKEUP |
| 199 | * This is the notification for the blocked thread that a |
| 200 | * result value is imminent. |
| 201 | * * call wake_up_process |
| 202 | * * set queue.status to the final value. |
| 203 | * - the previously blocked thread checks queue.status: |
| 204 | * * if it's IN_WAKEUP, then it must wait until the value changes |
| 205 | * * if it's not -EINTR, then the operation was completed by |
| 206 | * update_queue. semtimedop can return queue.status without |
| 207 | * performing any operation on the sem array. |
| 208 | * * otherwise it must acquire the spinlock and check what's up. |
| 209 | * |
| 210 | * The two-stage algorithm is necessary to protect against the following |
| 211 | * races: |
| 212 | * - if queue.status is set after wake_up_process, then the woken up idle |
| 213 | * thread could race forward and try (and fail) to acquire sma->lock |
| 214 | * before update_queue had a chance to set queue.status |
| 215 | * - if queue.status is written before wake_up_process and if the |
| 216 | * blocked process is woken up by a signal between writing |
| 217 | * queue.status and the wake_up_process, then the woken up |
| 218 | * process could return from semtimedop and die by calling |
| 219 | * sys_exit before wake_up_process is called. Then wake_up_process |
| 220 | * will oops, because the task structure is already invalid. |
| 221 | * (yes, this happened on s390 with sysv msg). |
| 222 | * |
| 223 | */ |
| 224 | #define IN_WAKEUP 1 |
| 225 | |
| 226 | /** |
| 227 | * newary - Create a new semaphore set |
| 228 | * @ns: namespace |
| 229 | * @params: ptr to the structure that contains key, semflg and nsems |
| 230 | * |
| 231 | * Called with sem_ids.rw_mutex held (as a writer) |
| 232 | */ |
| 233 | |
| 234 | static int newary(struct ipc_namespace *ns, struct ipc_params *params) |
| 235 | { |
| 236 | int id; |
| 237 | int retval; |
| 238 | struct sem_array *sma; |
| 239 | int size; |
| 240 | key_t key = params->key; |
| 241 | int nsems = params->u.nsems; |
| 242 | int semflg = params->flg; |
| 243 | |
| 244 | if (!nsems) |
| 245 | return -EINVAL; |
| 246 | if (ns->used_sems + nsems > ns->sc_semmns) |
| 247 | return -ENOSPC; |
| 248 | |
| 249 | size = sizeof (*sma) + nsems * sizeof (struct sem); |
| 250 | sma = ipc_rcu_alloc(size); |
| 251 | if (!sma) { |
| 252 | return -ENOMEM; |
| 253 | } |
| 254 | memset (sma, 0, size); |
| 255 | |
| 256 | sma->sem_perm.mode = (semflg & S_IRWXUGO); |
| 257 | sma->sem_perm.key = key; |
| 258 | |
| 259 | sma->sem_perm.security = NULL; |
| 260 | retval = security_sem_alloc(sma); |
| 261 | if (retval) { |
| 262 | ipc_rcu_putref(sma); |
| 263 | return retval; |
| 264 | } |
| 265 | |
| 266 | id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); |
| 267 | if (id < 0) { |
| 268 | security_sem_free(sma); |
| 269 | ipc_rcu_putref(sma); |
| 270 | return id; |
| 271 | } |
| 272 | ns->used_sems += nsems; |
| 273 | |
| 274 | sma->sem_base = (struct sem *) &sma[1]; |
| 275 | INIT_LIST_HEAD(&sma->sem_pending); |
| 276 | INIT_LIST_HEAD(&sma->list_id); |
| 277 | sma->sem_nsems = nsems; |
| 278 | sma->sem_ctime = get_seconds(); |
| 279 | sem_unlock(sma); |
| 280 | |
| 281 | return sma->sem_perm.id; |
| 282 | } |
| 283 | |
| 284 | |
| 285 | /* |
| 286 | * Called with sem_ids.rw_mutex and ipcp locked. |
| 287 | */ |
| 288 | static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg) |
| 289 | { |
| 290 | struct sem_array *sma; |
| 291 | |
| 292 | sma = container_of(ipcp, struct sem_array, sem_perm); |
| 293 | return security_sem_associate(sma, semflg); |
| 294 | } |
| 295 | |
| 296 | /* |
| 297 | * Called with sem_ids.rw_mutex and ipcp locked. |
| 298 | */ |
| 299 | static inline int sem_more_checks(struct kern_ipc_perm *ipcp, |
| 300 | struct ipc_params *params) |
| 301 | { |
| 302 | struct sem_array *sma; |
| 303 | |
| 304 | sma = container_of(ipcp, struct sem_array, sem_perm); |
| 305 | if (params->u.nsems > sma->sem_nsems) |
| 306 | return -EINVAL; |
| 307 | |
| 308 | return 0; |
| 309 | } |
| 310 | |
| 311 | SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) |
| 312 | { |
| 313 | struct ipc_namespace *ns; |
| 314 | struct ipc_ops sem_ops; |
| 315 | struct ipc_params sem_params; |
| 316 | |
| 317 | ns = current->nsproxy->ipc_ns; |
| 318 | |
| 319 | if (nsems < 0 || nsems > ns->sc_semmsl) |
| 320 | return -EINVAL; |
| 321 | |
| 322 | sem_ops.getnew = newary; |
| 323 | sem_ops.associate = sem_security; |
| 324 | sem_ops.more_checks = sem_more_checks; |
| 325 | |
| 326 | sem_params.key = key; |
| 327 | sem_params.flg = semflg; |
| 328 | sem_params.u.nsems = nsems; |
| 329 | |
| 330 | return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); |
| 331 | } |
| 332 | |
| 333 | /* |
| 334 | * Determine whether a sequence of semaphore operations would succeed |
| 335 | * all at once. Return 0 if yes, 1 if need to sleep, else return error code. |
| 336 | */ |
| 337 | |
| 338 | static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops, |
| 339 | int nsops, struct sem_undo *un, int pid) |
| 340 | { |
| 341 | int result, sem_op; |
| 342 | struct sembuf *sop; |
| 343 | struct sem * curr; |
| 344 | |
| 345 | for (sop = sops; sop < sops + nsops; sop++) { |
| 346 | curr = sma->sem_base + sop->sem_num; |
| 347 | sem_op = sop->sem_op; |
| 348 | result = curr->semval; |
| 349 | |
| 350 | if (!sem_op && result) |
| 351 | goto would_block; |
| 352 | |
| 353 | result += sem_op; |
| 354 | if (result < 0) |
| 355 | goto would_block; |
| 356 | if (result > SEMVMX) |
| 357 | goto out_of_range; |
| 358 | if (sop->sem_flg & SEM_UNDO) { |
| 359 | int undo = un->semadj[sop->sem_num] - sem_op; |
| 360 | /* |
| 361 | * Exceeding the undo range is an error. |
| 362 | */ |
| 363 | if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
| 364 | goto out_of_range; |
| 365 | } |
| 366 | curr->semval = result; |
| 367 | } |
| 368 | |
| 369 | sop--; |
| 370 | while (sop >= sops) { |
| 371 | sma->sem_base[sop->sem_num].sempid = pid; |
| 372 | if (sop->sem_flg & SEM_UNDO) |
| 373 | un->semadj[sop->sem_num] -= sop->sem_op; |
| 374 | sop--; |
| 375 | } |
| 376 | |
| 377 | sma->sem_otime = get_seconds(); |
| 378 | return 0; |
| 379 | |
| 380 | out_of_range: |
| 381 | result = -ERANGE; |
| 382 | goto undo; |
| 383 | |
| 384 | would_block: |
| 385 | if (sop->sem_flg & IPC_NOWAIT) |
| 386 | result = -EAGAIN; |
| 387 | else |
| 388 | result = 1; |
| 389 | |
| 390 | undo: |
| 391 | sop--; |
| 392 | while (sop >= sops) { |
| 393 | sma->sem_base[sop->sem_num].semval -= sop->sem_op; |
| 394 | sop--; |
| 395 | } |
| 396 | |
| 397 | return result; |
| 398 | } |
| 399 | |
| 400 | /* Go through the pending queue for the indicated semaphore |
| 401 | * looking for tasks that can be completed. |
| 402 | */ |
| 403 | static void update_queue (struct sem_array * sma) |
| 404 | { |
| 405 | int error; |
| 406 | struct sem_queue * q; |
| 407 | |
| 408 | q = list_entry(sma->sem_pending.next, struct sem_queue, list); |
| 409 | while (&q->list != &sma->sem_pending) { |
| 410 | error = try_atomic_semop(sma, q->sops, q->nsops, |
| 411 | q->undo, q->pid); |
| 412 | |
| 413 | /* Does q->sleeper still need to sleep? */ |
| 414 | if (error <= 0) { |
| 415 | struct sem_queue *n; |
| 416 | |
| 417 | /* |
| 418 | * Continue scanning. The next operation |
| 419 | * that must be checked depends on the type of the |
| 420 | * completed operation: |
| 421 | * - if the operation modified the array, then |
| 422 | * restart from the head of the queue and |
| 423 | * check for threads that might be waiting |
| 424 | * for semaphore values to become 0. |
| 425 | * - if the operation didn't modify the array, |
| 426 | * then just continue. |
| 427 | * The order of list_del() and reading ->next |
| 428 | * is crucial: In the former case, the list_del() |
| 429 | * must be done first [because we might be the |
| 430 | * first entry in ->sem_pending], in the latter |
| 431 | * case the list_del() must be done last |
| 432 | * [because the list is invalid after the list_del()] |
| 433 | */ |
| 434 | if (q->alter) { |
| 435 | list_del(&q->list); |
| 436 | n = list_entry(sma->sem_pending.next, |
| 437 | struct sem_queue, list); |
| 438 | } else { |
| 439 | n = list_entry(q->list.next, struct sem_queue, |
| 440 | list); |
| 441 | list_del(&q->list); |
| 442 | } |
| 443 | |
| 444 | /* wake up the waiting thread */ |
| 445 | q->status = IN_WAKEUP; |
| 446 | |
| 447 | wake_up_process(q->sleeper); |
| 448 | /* hands-off: q will disappear immediately after |
| 449 | * writing q->status. |
| 450 | */ |
| 451 | smp_wmb(); |
| 452 | q->status = error; |
| 453 | q = n; |
| 454 | } else { |
| 455 | q = list_entry(q->list.next, struct sem_queue, list); |
| 456 | } |
| 457 | } |
| 458 | } |
| 459 | |
| 460 | /* The following counts are associated to each semaphore: |
| 461 | * semncnt number of tasks waiting on semval being nonzero |
| 462 | * semzcnt number of tasks waiting on semval being zero |
| 463 | * This model assumes that a task waits on exactly one semaphore. |
| 464 | * Since semaphore operations are to be performed atomically, tasks actually |
| 465 | * wait on a whole sequence of semaphores simultaneously. |
| 466 | * The counts we return here are a rough approximation, but still |
| 467 | * warrant that semncnt+semzcnt>0 if the task is on the pending queue. |
| 468 | */ |
| 469 | static int count_semncnt (struct sem_array * sma, ushort semnum) |
| 470 | { |
| 471 | int semncnt; |
| 472 | struct sem_queue * q; |
| 473 | |
| 474 | semncnt = 0; |
| 475 | list_for_each_entry(q, &sma->sem_pending, list) { |
| 476 | struct sembuf * sops = q->sops; |
| 477 | int nsops = q->nsops; |
| 478 | int i; |
| 479 | for (i = 0; i < nsops; i++) |
| 480 | if (sops[i].sem_num == semnum |
| 481 | && (sops[i].sem_op < 0) |
| 482 | && !(sops[i].sem_flg & IPC_NOWAIT)) |
| 483 | semncnt++; |
| 484 | } |
| 485 | return semncnt; |
| 486 | } |
| 487 | |
| 488 | static int count_semzcnt (struct sem_array * sma, ushort semnum) |
| 489 | { |
| 490 | int semzcnt; |
| 491 | struct sem_queue * q; |
| 492 | |
| 493 | semzcnt = 0; |
| 494 | list_for_each_entry(q, &sma->sem_pending, list) { |
| 495 | struct sembuf * sops = q->sops; |
| 496 | int nsops = q->nsops; |
| 497 | int i; |
| 498 | for (i = 0; i < nsops; i++) |
| 499 | if (sops[i].sem_num == semnum |
| 500 | && (sops[i].sem_op == 0) |
| 501 | && !(sops[i].sem_flg & IPC_NOWAIT)) |
| 502 | semzcnt++; |
| 503 | } |
| 504 | return semzcnt; |
| 505 | } |
| 506 | |
| 507 | static void free_un(struct rcu_head *head) |
| 508 | { |
| 509 | struct sem_undo *un = container_of(head, struct sem_undo, rcu); |
| 510 | kfree(un); |
| 511 | } |
| 512 | |
| 513 | /* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked |
| 514 | * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex |
| 515 | * remains locked on exit. |
| 516 | */ |
| 517 | static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) |
| 518 | { |
| 519 | struct sem_undo *un, *tu; |
| 520 | struct sem_queue *q, *tq; |
| 521 | struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
| 522 | |
| 523 | /* Free the existing undo structures for this semaphore set. */ |
| 524 | assert_spin_locked(&sma->sem_perm.lock); |
| 525 | list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { |
| 526 | list_del(&un->list_id); |
| 527 | spin_lock(&un->ulp->lock); |
| 528 | un->semid = -1; |
| 529 | list_del_rcu(&un->list_proc); |
| 530 | spin_unlock(&un->ulp->lock); |
| 531 | call_rcu(&un->rcu, free_un); |
| 532 | } |
| 533 | |
| 534 | /* Wake up all pending processes and let them fail with EIDRM. */ |
| 535 | list_for_each_entry_safe(q, tq, &sma->sem_pending, list) { |
| 536 | list_del(&q->list); |
| 537 | |
| 538 | q->status = IN_WAKEUP; |
| 539 | wake_up_process(q->sleeper); /* doesn't sleep */ |
| 540 | smp_wmb(); |
| 541 | q->status = -EIDRM; /* hands-off q */ |
| 542 | } |
| 543 | |
| 544 | /* Remove the semaphore set from the IDR */ |
| 545 | sem_rmid(ns, sma); |
| 546 | sem_unlock(sma); |
| 547 | |
| 548 | ns->used_sems -= sma->sem_nsems; |
| 549 | security_sem_free(sma); |
| 550 | ipc_rcu_putref(sma); |
| 551 | } |
| 552 | |
| 553 | static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) |
| 554 | { |
| 555 | switch(version) { |
| 556 | case IPC_64: |
| 557 | return copy_to_user(buf, in, sizeof(*in)); |
| 558 | case IPC_OLD: |
| 559 | { |
| 560 | struct semid_ds out; |
| 561 | |
| 562 | ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); |
| 563 | |
| 564 | out.sem_otime = in->sem_otime; |
| 565 | out.sem_ctime = in->sem_ctime; |
| 566 | out.sem_nsems = in->sem_nsems; |
| 567 | |
| 568 | return copy_to_user(buf, &out, sizeof(out)); |
| 569 | } |
| 570 | default: |
| 571 | return -EINVAL; |
| 572 | } |
| 573 | } |
| 574 | |
| 575 | static int semctl_nolock(struct ipc_namespace *ns, int semid, |
| 576 | int cmd, int version, union semun arg) |
| 577 | { |
| 578 | int err = -EINVAL; |
| 579 | struct sem_array *sma; |
| 580 | |
| 581 | switch(cmd) { |
| 582 | case IPC_INFO: |
| 583 | case SEM_INFO: |
| 584 | { |
| 585 | struct seminfo seminfo; |
| 586 | int max_id; |
| 587 | |
| 588 | err = security_sem_semctl(NULL, cmd); |
| 589 | if (err) |
| 590 | return err; |
| 591 | |
| 592 | memset(&seminfo,0,sizeof(seminfo)); |
| 593 | seminfo.semmni = ns->sc_semmni; |
| 594 | seminfo.semmns = ns->sc_semmns; |
| 595 | seminfo.semmsl = ns->sc_semmsl; |
| 596 | seminfo.semopm = ns->sc_semopm; |
| 597 | seminfo.semvmx = SEMVMX; |
| 598 | seminfo.semmnu = SEMMNU; |
| 599 | seminfo.semmap = SEMMAP; |
| 600 | seminfo.semume = SEMUME; |
| 601 | down_read(&sem_ids(ns).rw_mutex); |
| 602 | if (cmd == SEM_INFO) { |
| 603 | seminfo.semusz = sem_ids(ns).in_use; |
| 604 | seminfo.semaem = ns->used_sems; |
| 605 | } else { |
| 606 | seminfo.semusz = SEMUSZ; |
| 607 | seminfo.semaem = SEMAEM; |
| 608 | } |
| 609 | max_id = ipc_get_maxid(&sem_ids(ns)); |
| 610 | up_read(&sem_ids(ns).rw_mutex); |
| 611 | if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo))) |
| 612 | return -EFAULT; |
| 613 | return (max_id < 0) ? 0: max_id; |
| 614 | } |
| 615 | case IPC_STAT: |
| 616 | case SEM_STAT: |
| 617 | { |
| 618 | struct semid64_ds tbuf; |
| 619 | int id; |
| 620 | |
| 621 | if (cmd == SEM_STAT) { |
| 622 | sma = sem_lock(ns, semid); |
| 623 | if (IS_ERR(sma)) |
| 624 | return PTR_ERR(sma); |
| 625 | id = sma->sem_perm.id; |
| 626 | } else { |
| 627 | sma = sem_lock_check(ns, semid); |
| 628 | if (IS_ERR(sma)) |
| 629 | return PTR_ERR(sma); |
| 630 | id = 0; |
| 631 | } |
| 632 | |
| 633 | err = -EACCES; |
| 634 | if (ipcperms (&sma->sem_perm, S_IRUGO)) |
| 635 | goto out_unlock; |
| 636 | |
| 637 | err = security_sem_semctl(sma, cmd); |
| 638 | if (err) |
| 639 | goto out_unlock; |
| 640 | |
| 641 | memset(&tbuf, 0, sizeof(tbuf)); |
| 642 | |
| 643 | kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm); |
| 644 | tbuf.sem_otime = sma->sem_otime; |
| 645 | tbuf.sem_ctime = sma->sem_ctime; |
| 646 | tbuf.sem_nsems = sma->sem_nsems; |
| 647 | sem_unlock(sma); |
| 648 | if (copy_semid_to_user (arg.buf, &tbuf, version)) |
| 649 | return -EFAULT; |
| 650 | return id; |
| 651 | } |
| 652 | default: |
| 653 | return -EINVAL; |
| 654 | } |
| 655 | return err; |
| 656 | out_unlock: |
| 657 | sem_unlock(sma); |
| 658 | return err; |
| 659 | } |
| 660 | |
| 661 | static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, |
| 662 | int cmd, int version, union semun arg) |
| 663 | { |
| 664 | struct sem_array *sma; |
| 665 | struct sem* curr; |
| 666 | int err; |
| 667 | ushort fast_sem_io[SEMMSL_FAST]; |
| 668 | ushort* sem_io = fast_sem_io; |
| 669 | int nsems; |
| 670 | |
| 671 | sma = sem_lock_check(ns, semid); |
| 672 | if (IS_ERR(sma)) |
| 673 | return PTR_ERR(sma); |
| 674 | |
| 675 | nsems = sma->sem_nsems; |
| 676 | |
| 677 | err = -EACCES; |
| 678 | if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO)) |
| 679 | goto out_unlock; |
| 680 | |
| 681 | err = security_sem_semctl(sma, cmd); |
| 682 | if (err) |
| 683 | goto out_unlock; |
| 684 | |
| 685 | err = -EACCES; |
| 686 | switch (cmd) { |
| 687 | case GETALL: |
| 688 | { |
| 689 | ushort __user *array = arg.array; |
| 690 | int i; |
| 691 | |
| 692 | if(nsems > SEMMSL_FAST) { |
| 693 | sem_getref_and_unlock(sma); |
| 694 | |
| 695 | sem_io = ipc_alloc(sizeof(ushort)*nsems); |
| 696 | if(sem_io == NULL) { |
| 697 | sem_putref(sma); |
| 698 | return -ENOMEM; |
| 699 | } |
| 700 | |
| 701 | sem_lock_and_putref(sma); |
| 702 | if (sma->sem_perm.deleted) { |
| 703 | sem_unlock(sma); |
| 704 | err = -EIDRM; |
| 705 | goto out_free; |
| 706 | } |
| 707 | } |
| 708 | |
| 709 | for (i = 0; i < sma->sem_nsems; i++) |
| 710 | sem_io[i] = sma->sem_base[i].semval; |
| 711 | sem_unlock(sma); |
| 712 | err = 0; |
| 713 | if(copy_to_user(array, sem_io, nsems*sizeof(ushort))) |
| 714 | err = -EFAULT; |
| 715 | goto out_free; |
| 716 | } |
| 717 | case SETALL: |
| 718 | { |
| 719 | int i; |
| 720 | struct sem_undo *un; |
| 721 | |
| 722 | sem_getref_and_unlock(sma); |
| 723 | |
| 724 | if(nsems > SEMMSL_FAST) { |
| 725 | sem_io = ipc_alloc(sizeof(ushort)*nsems); |
| 726 | if(sem_io == NULL) { |
| 727 | sem_putref(sma); |
| 728 | return -ENOMEM; |
| 729 | } |
| 730 | } |
| 731 | |
| 732 | if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) { |
| 733 | sem_putref(sma); |
| 734 | err = -EFAULT; |
| 735 | goto out_free; |
| 736 | } |
| 737 | |
| 738 | for (i = 0; i < nsems; i++) { |
| 739 | if (sem_io[i] > SEMVMX) { |
| 740 | sem_putref(sma); |
| 741 | err = -ERANGE; |
| 742 | goto out_free; |
| 743 | } |
| 744 | } |
| 745 | sem_lock_and_putref(sma); |
| 746 | if (sma->sem_perm.deleted) { |
| 747 | sem_unlock(sma); |
| 748 | err = -EIDRM; |
| 749 | goto out_free; |
| 750 | } |
| 751 | |
| 752 | for (i = 0; i < nsems; i++) |
| 753 | sma->sem_base[i].semval = sem_io[i]; |
| 754 | |
| 755 | assert_spin_locked(&sma->sem_perm.lock); |
| 756 | list_for_each_entry(un, &sma->list_id, list_id) { |
| 757 | for (i = 0; i < nsems; i++) |
| 758 | un->semadj[i] = 0; |
| 759 | } |
| 760 | sma->sem_ctime = get_seconds(); |
| 761 | /* maybe some queued-up processes were waiting for this */ |
| 762 | update_queue(sma); |
| 763 | err = 0; |
| 764 | goto out_unlock; |
| 765 | } |
| 766 | /* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */ |
| 767 | } |
| 768 | err = -EINVAL; |
| 769 | if(semnum < 0 || semnum >= nsems) |
| 770 | goto out_unlock; |
| 771 | |
| 772 | curr = &sma->sem_base[semnum]; |
| 773 | |
| 774 | switch (cmd) { |
| 775 | case GETVAL: |
| 776 | err = curr->semval; |
| 777 | goto out_unlock; |
| 778 | case GETPID: |
| 779 | err = curr->sempid; |
| 780 | goto out_unlock; |
| 781 | case GETNCNT: |
| 782 | err = count_semncnt(sma,semnum); |
| 783 | goto out_unlock; |
| 784 | case GETZCNT: |
| 785 | err = count_semzcnt(sma,semnum); |
| 786 | goto out_unlock; |
| 787 | case SETVAL: |
| 788 | { |
| 789 | int val = arg.val; |
| 790 | struct sem_undo *un; |
| 791 | |
| 792 | err = -ERANGE; |
| 793 | if (val > SEMVMX || val < 0) |
| 794 | goto out_unlock; |
| 795 | |
| 796 | assert_spin_locked(&sma->sem_perm.lock); |
| 797 | list_for_each_entry(un, &sma->list_id, list_id) |
| 798 | un->semadj[semnum] = 0; |
| 799 | |
| 800 | curr->semval = val; |
| 801 | curr->sempid = task_tgid_vnr(current); |
| 802 | sma->sem_ctime = get_seconds(); |
| 803 | /* maybe some queued-up processes were waiting for this */ |
| 804 | update_queue(sma); |
| 805 | err = 0; |
| 806 | goto out_unlock; |
| 807 | } |
| 808 | } |
| 809 | out_unlock: |
| 810 | sem_unlock(sma); |
| 811 | out_free: |
| 812 | if(sem_io != fast_sem_io) |
| 813 | ipc_free(sem_io, sizeof(ushort)*nsems); |
| 814 | return err; |
| 815 | } |
| 816 | |
| 817 | static inline unsigned long |
| 818 | copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) |
| 819 | { |
| 820 | switch(version) { |
| 821 | case IPC_64: |
| 822 | if (copy_from_user(out, buf, sizeof(*out))) |
| 823 | return -EFAULT; |
| 824 | return 0; |
| 825 | case IPC_OLD: |
| 826 | { |
| 827 | struct semid_ds tbuf_old; |
| 828 | |
| 829 | if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) |
| 830 | return -EFAULT; |
| 831 | |
| 832 | out->sem_perm.uid = tbuf_old.sem_perm.uid; |
| 833 | out->sem_perm.gid = tbuf_old.sem_perm.gid; |
| 834 | out->sem_perm.mode = tbuf_old.sem_perm.mode; |
| 835 | |
| 836 | return 0; |
| 837 | } |
| 838 | default: |
| 839 | return -EINVAL; |
| 840 | } |
| 841 | } |
| 842 | |
| 843 | /* |
| 844 | * This function handles some semctl commands which require the rw_mutex |
| 845 | * to be held in write mode. |
| 846 | * NOTE: no locks must be held, the rw_mutex is taken inside this function. |
| 847 | */ |
| 848 | static int semctl_down(struct ipc_namespace *ns, int semid, |
| 849 | int cmd, int version, union semun arg) |
| 850 | { |
| 851 | struct sem_array *sma; |
| 852 | int err; |
| 853 | struct semid64_ds semid64; |
| 854 | struct kern_ipc_perm *ipcp; |
| 855 | |
| 856 | if(cmd == IPC_SET) { |
| 857 | if (copy_semid_from_user(&semid64, arg.buf, version)) |
| 858 | return -EFAULT; |
| 859 | } |
| 860 | |
| 861 | ipcp = ipcctl_pre_down(&sem_ids(ns), semid, cmd, &semid64.sem_perm, 0); |
| 862 | if (IS_ERR(ipcp)) |
| 863 | return PTR_ERR(ipcp); |
| 864 | |
| 865 | sma = container_of(ipcp, struct sem_array, sem_perm); |
| 866 | |
| 867 | err = security_sem_semctl(sma, cmd); |
| 868 | if (err) |
| 869 | goto out_unlock; |
| 870 | |
| 871 | switch(cmd){ |
| 872 | case IPC_RMID: |
| 873 | freeary(ns, ipcp); |
| 874 | goto out_up; |
| 875 | case IPC_SET: |
| 876 | ipc_update_perm(&semid64.sem_perm, ipcp); |
| 877 | sma->sem_ctime = get_seconds(); |
| 878 | break; |
| 879 | default: |
| 880 | err = -EINVAL; |
| 881 | } |
| 882 | |
| 883 | out_unlock: |
| 884 | sem_unlock(sma); |
| 885 | out_up: |
| 886 | up_write(&sem_ids(ns).rw_mutex); |
| 887 | return err; |
| 888 | } |
| 889 | |
| 890 | SYSCALL_DEFINE(semctl)(int semid, int semnum, int cmd, union semun arg) |
| 891 | { |
| 892 | int err = -EINVAL; |
| 893 | int version; |
| 894 | struct ipc_namespace *ns; |
| 895 | |
| 896 | if (semid < 0) |
| 897 | return -EINVAL; |
| 898 | |
| 899 | version = ipc_parse_version(&cmd); |
| 900 | ns = current->nsproxy->ipc_ns; |
| 901 | |
| 902 | switch(cmd) { |
| 903 | case IPC_INFO: |
| 904 | case SEM_INFO: |
| 905 | case IPC_STAT: |
| 906 | case SEM_STAT: |
| 907 | err = semctl_nolock(ns, semid, cmd, version, arg); |
| 908 | return err; |
| 909 | case GETALL: |
| 910 | case GETVAL: |
| 911 | case GETPID: |
| 912 | case GETNCNT: |
| 913 | case GETZCNT: |
| 914 | case SETVAL: |
| 915 | case SETALL: |
| 916 | err = semctl_main(ns,semid,semnum,cmd,version,arg); |
| 917 | return err; |
| 918 | case IPC_RMID: |
| 919 | case IPC_SET: |
| 920 | err = semctl_down(ns, semid, cmd, version, arg); |
| 921 | return err; |
| 922 | default: |
| 923 | return -EINVAL; |
| 924 | } |
| 925 | } |
| 926 | #ifdef CONFIG_HAVE_SYSCALL_WRAPPERS |
| 927 | asmlinkage long SyS_semctl(int semid, int semnum, int cmd, union semun arg) |
| 928 | { |
| 929 | return SYSC_semctl((int) semid, (int) semnum, (int) cmd, arg); |
| 930 | } |
| 931 | SYSCALL_ALIAS(sys_semctl, SyS_semctl); |
| 932 | #endif |
| 933 | |
| 934 | /* If the task doesn't already have a undo_list, then allocate one |
| 935 | * here. We guarantee there is only one thread using this undo list, |
| 936 | * and current is THE ONE |
| 937 | * |
| 938 | * If this allocation and assignment succeeds, but later |
| 939 | * portions of this code fail, there is no need to free the sem_undo_list. |
| 940 | * Just let it stay associated with the task, and it'll be freed later |
| 941 | * at exit time. |
| 942 | * |
| 943 | * This can block, so callers must hold no locks. |
| 944 | */ |
| 945 | static inline int get_undo_list(struct sem_undo_list **undo_listp) |
| 946 | { |
| 947 | struct sem_undo_list *undo_list; |
| 948 | |
| 949 | undo_list = current->sysvsem.undo_list; |
| 950 | if (!undo_list) { |
| 951 | undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL); |
| 952 | if (undo_list == NULL) |
| 953 | return -ENOMEM; |
| 954 | spin_lock_init(&undo_list->lock); |
| 955 | atomic_set(&undo_list->refcnt, 1); |
| 956 | INIT_LIST_HEAD(&undo_list->list_proc); |
| 957 | |
| 958 | current->sysvsem.undo_list = undo_list; |
| 959 | } |
| 960 | *undo_listp = undo_list; |
| 961 | return 0; |
| 962 | } |
| 963 | |
| 964 | static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) |
| 965 | { |
| 966 | struct sem_undo *walk; |
| 967 | |
| 968 | list_for_each_entry_rcu(walk, &ulp->list_proc, list_proc) { |
| 969 | if (walk->semid == semid) |
| 970 | return walk; |
| 971 | } |
| 972 | return NULL; |
| 973 | } |
| 974 | |
| 975 | /** |
| 976 | * find_alloc_undo - Lookup (and if not present create) undo array |
| 977 | * @ns: namespace |
| 978 | * @semid: semaphore array id |
| 979 | * |
| 980 | * The function looks up (and if not present creates) the undo structure. |
| 981 | * The size of the undo structure depends on the size of the semaphore |
| 982 | * array, thus the alloc path is not that straightforward. |
| 983 | * Lifetime-rules: sem_undo is rcu-protected, on success, the function |
| 984 | * performs a rcu_read_lock(). |
| 985 | */ |
| 986 | static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) |
| 987 | { |
| 988 | struct sem_array *sma; |
| 989 | struct sem_undo_list *ulp; |
| 990 | struct sem_undo *un, *new; |
| 991 | int nsems; |
| 992 | int error; |
| 993 | |
| 994 | error = get_undo_list(&ulp); |
| 995 | if (error) |
| 996 | return ERR_PTR(error); |
| 997 | |
| 998 | rcu_read_lock(); |
| 999 | spin_lock(&ulp->lock); |
| 1000 | un = lookup_undo(ulp, semid); |
| 1001 | spin_unlock(&ulp->lock); |
| 1002 | if (likely(un!=NULL)) |
| 1003 | goto out; |
| 1004 | rcu_read_unlock(); |
| 1005 | |
| 1006 | /* no undo structure around - allocate one. */ |
| 1007 | /* step 1: figure out the size of the semaphore array */ |
| 1008 | sma = sem_lock_check(ns, semid); |
| 1009 | if (IS_ERR(sma)) |
| 1010 | return ERR_PTR(PTR_ERR(sma)); |
| 1011 | |
| 1012 | nsems = sma->sem_nsems; |
| 1013 | sem_getref_and_unlock(sma); |
| 1014 | |
| 1015 | /* step 2: allocate new undo structure */ |
| 1016 | new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL); |
| 1017 | if (!new) { |
| 1018 | sem_putref(sma); |
| 1019 | return ERR_PTR(-ENOMEM); |
| 1020 | } |
| 1021 | |
| 1022 | /* step 3: Acquire the lock on semaphore array */ |
| 1023 | sem_lock_and_putref(sma); |
| 1024 | if (sma->sem_perm.deleted) { |
| 1025 | sem_unlock(sma); |
| 1026 | kfree(new); |
| 1027 | un = ERR_PTR(-EIDRM); |
| 1028 | goto out; |
| 1029 | } |
| 1030 | spin_lock(&ulp->lock); |
| 1031 | |
| 1032 | /* |
| 1033 | * step 4: check for races: did someone else allocate the undo struct? |
| 1034 | */ |
| 1035 | un = lookup_undo(ulp, semid); |
| 1036 | if (un) { |
| 1037 | kfree(new); |
| 1038 | goto success; |
| 1039 | } |
| 1040 | /* step 5: initialize & link new undo structure */ |
| 1041 | new->semadj = (short *) &new[1]; |
| 1042 | new->ulp = ulp; |
| 1043 | new->semid = semid; |
| 1044 | assert_spin_locked(&ulp->lock); |
| 1045 | list_add_rcu(&new->list_proc, &ulp->list_proc); |
| 1046 | assert_spin_locked(&sma->sem_perm.lock); |
| 1047 | list_add(&new->list_id, &sma->list_id); |
| 1048 | un = new; |
| 1049 | |
| 1050 | success: |
| 1051 | spin_unlock(&ulp->lock); |
| 1052 | rcu_read_lock(); |
| 1053 | sem_unlock(sma); |
| 1054 | out: |
| 1055 | return un; |
| 1056 | } |
| 1057 | |
| 1058 | SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, |
| 1059 | unsigned, nsops, const struct timespec __user *, timeout) |
| 1060 | { |
| 1061 | int error = -EINVAL; |
| 1062 | struct sem_array *sma; |
| 1063 | struct sembuf fast_sops[SEMOPM_FAST]; |
| 1064 | struct sembuf* sops = fast_sops, *sop; |
| 1065 | struct sem_undo *un; |
| 1066 | int undos = 0, alter = 0, max; |
| 1067 | struct sem_queue queue; |
| 1068 | unsigned long jiffies_left = 0; |
| 1069 | struct ipc_namespace *ns; |
| 1070 | |
| 1071 | ns = current->nsproxy->ipc_ns; |
| 1072 | |
| 1073 | if (nsops < 1 || semid < 0) |
| 1074 | return -EINVAL; |
| 1075 | if (nsops > ns->sc_semopm) |
| 1076 | return -E2BIG; |
| 1077 | if(nsops > SEMOPM_FAST) { |
| 1078 | sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL); |
| 1079 | if(sops==NULL) |
| 1080 | return -ENOMEM; |
| 1081 | } |
| 1082 | if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) { |
| 1083 | error=-EFAULT; |
| 1084 | goto out_free; |
| 1085 | } |
| 1086 | if (timeout) { |
| 1087 | struct timespec _timeout; |
| 1088 | if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) { |
| 1089 | error = -EFAULT; |
| 1090 | goto out_free; |
| 1091 | } |
| 1092 | if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 || |
| 1093 | _timeout.tv_nsec >= 1000000000L) { |
| 1094 | error = -EINVAL; |
| 1095 | goto out_free; |
| 1096 | } |
| 1097 | jiffies_left = timespec_to_jiffies(&_timeout); |
| 1098 | } |
| 1099 | max = 0; |
| 1100 | for (sop = sops; sop < sops + nsops; sop++) { |
| 1101 | if (sop->sem_num >= max) |
| 1102 | max = sop->sem_num; |
| 1103 | if (sop->sem_flg & SEM_UNDO) |
| 1104 | undos = 1; |
| 1105 | if (sop->sem_op != 0) |
| 1106 | alter = 1; |
| 1107 | } |
| 1108 | |
| 1109 | if (undos) { |
| 1110 | un = find_alloc_undo(ns, semid); |
| 1111 | if (IS_ERR(un)) { |
| 1112 | error = PTR_ERR(un); |
| 1113 | goto out_free; |
| 1114 | } |
| 1115 | } else |
| 1116 | un = NULL; |
| 1117 | |
| 1118 | sma = sem_lock_check(ns, semid); |
| 1119 | if (IS_ERR(sma)) { |
| 1120 | if (un) |
| 1121 | rcu_read_unlock(); |
| 1122 | error = PTR_ERR(sma); |
| 1123 | goto out_free; |
| 1124 | } |
| 1125 | |
| 1126 | /* |
| 1127 | * semid identifiers are not unique - find_alloc_undo may have |
| 1128 | * allocated an undo structure, it was invalidated by an RMID |
| 1129 | * and now a new array with received the same id. Check and fail. |
| 1130 | * This case can be detected checking un->semid. The existance of |
| 1131 | * "un" itself is guaranteed by rcu. |
| 1132 | */ |
| 1133 | error = -EIDRM; |
| 1134 | if (un) { |
| 1135 | if (un->semid == -1) { |
| 1136 | rcu_read_unlock(); |
| 1137 | goto out_unlock_free; |
| 1138 | } else { |
| 1139 | /* |
| 1140 | * rcu lock can be released, "un" cannot disappear: |
| 1141 | * - sem_lock is acquired, thus IPC_RMID is |
| 1142 | * impossible. |
| 1143 | * - exit_sem is impossible, it always operates on |
| 1144 | * current (or a dead task). |
| 1145 | */ |
| 1146 | |
| 1147 | rcu_read_unlock(); |
| 1148 | } |
| 1149 | } |
| 1150 | |
| 1151 | error = -EFBIG; |
| 1152 | if (max >= sma->sem_nsems) |
| 1153 | goto out_unlock_free; |
| 1154 | |
| 1155 | error = -EACCES; |
| 1156 | if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) |
| 1157 | goto out_unlock_free; |
| 1158 | |
| 1159 | error = security_sem_semop(sma, sops, nsops, alter); |
| 1160 | if (error) |
| 1161 | goto out_unlock_free; |
| 1162 | |
| 1163 | error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current)); |
| 1164 | if (error <= 0) { |
| 1165 | if (alter && error == 0) |
| 1166 | update_queue (sma); |
| 1167 | goto out_unlock_free; |
| 1168 | } |
| 1169 | |
| 1170 | /* We need to sleep on this operation, so we put the current |
| 1171 | * task into the pending queue and go to sleep. |
| 1172 | */ |
| 1173 | |
| 1174 | queue.sops = sops; |
| 1175 | queue.nsops = nsops; |
| 1176 | queue.undo = un; |
| 1177 | queue.pid = task_tgid_vnr(current); |
| 1178 | queue.alter = alter; |
| 1179 | if (alter) |
| 1180 | list_add_tail(&queue.list, &sma->sem_pending); |
| 1181 | else |
| 1182 | list_add(&queue.list, &sma->sem_pending); |
| 1183 | |
| 1184 | queue.status = -EINTR; |
| 1185 | queue.sleeper = current; |
| 1186 | current->state = TASK_INTERRUPTIBLE; |
| 1187 | sem_unlock(sma); |
| 1188 | |
| 1189 | if (timeout) |
| 1190 | jiffies_left = schedule_timeout(jiffies_left); |
| 1191 | else |
| 1192 | schedule(); |
| 1193 | |
| 1194 | error = queue.status; |
| 1195 | while(unlikely(error == IN_WAKEUP)) { |
| 1196 | cpu_relax(); |
| 1197 | error = queue.status; |
| 1198 | } |
| 1199 | |
| 1200 | if (error != -EINTR) { |
| 1201 | /* fast path: update_queue already obtained all requested |
| 1202 | * resources */ |
| 1203 | goto out_free; |
| 1204 | } |
| 1205 | |
| 1206 | sma = sem_lock(ns, semid); |
| 1207 | if (IS_ERR(sma)) { |
| 1208 | error = -EIDRM; |
| 1209 | goto out_free; |
| 1210 | } |
| 1211 | |
| 1212 | /* |
| 1213 | * If queue.status != -EINTR we are woken up by another process |
| 1214 | */ |
| 1215 | error = queue.status; |
| 1216 | if (error != -EINTR) { |
| 1217 | goto out_unlock_free; |
| 1218 | } |
| 1219 | |
| 1220 | /* |
| 1221 | * If an interrupt occurred we have to clean up the queue |
| 1222 | */ |
| 1223 | if (timeout && jiffies_left == 0) |
| 1224 | error = -EAGAIN; |
| 1225 | list_del(&queue.list); |
| 1226 | |
| 1227 | out_unlock_free: |
| 1228 | sem_unlock(sma); |
| 1229 | out_free: |
| 1230 | if(sops != fast_sops) |
| 1231 | kfree(sops); |
| 1232 | return error; |
| 1233 | } |
| 1234 | |
| 1235 | SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, |
| 1236 | unsigned, nsops) |
| 1237 | { |
| 1238 | return sys_semtimedop(semid, tsops, nsops, NULL); |
| 1239 | } |
| 1240 | |
| 1241 | /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between |
| 1242 | * parent and child tasks. |
| 1243 | */ |
| 1244 | |
| 1245 | int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) |
| 1246 | { |
| 1247 | struct sem_undo_list *undo_list; |
| 1248 | int error; |
| 1249 | |
| 1250 | if (clone_flags & CLONE_SYSVSEM) { |
| 1251 | error = get_undo_list(&undo_list); |
| 1252 | if (error) |
| 1253 | return error; |
| 1254 | atomic_inc(&undo_list->refcnt); |
| 1255 | tsk->sysvsem.undo_list = undo_list; |
| 1256 | } else |
| 1257 | tsk->sysvsem.undo_list = NULL; |
| 1258 | |
| 1259 | return 0; |
| 1260 | } |
| 1261 | |
| 1262 | /* |
| 1263 | * add semadj values to semaphores, free undo structures. |
| 1264 | * undo structures are not freed when semaphore arrays are destroyed |
| 1265 | * so some of them may be out of date. |
| 1266 | * IMPLEMENTATION NOTE: There is some confusion over whether the |
| 1267 | * set of adjustments that needs to be done should be done in an atomic |
| 1268 | * manner or not. That is, if we are attempting to decrement the semval |
| 1269 | * should we queue up and wait until we can do so legally? |
| 1270 | * The original implementation attempted to do this (queue and wait). |
| 1271 | * The current implementation does not do so. The POSIX standard |
| 1272 | * and SVID should be consulted to determine what behavior is mandated. |
| 1273 | */ |
| 1274 | void exit_sem(struct task_struct *tsk) |
| 1275 | { |
| 1276 | struct sem_undo_list *ulp; |
| 1277 | |
| 1278 | ulp = tsk->sysvsem.undo_list; |
| 1279 | if (!ulp) |
| 1280 | return; |
| 1281 | tsk->sysvsem.undo_list = NULL; |
| 1282 | |
| 1283 | if (!atomic_dec_and_test(&ulp->refcnt)) |
| 1284 | return; |
| 1285 | |
| 1286 | for (;;) { |
| 1287 | struct sem_array *sma; |
| 1288 | struct sem_undo *un; |
| 1289 | int semid; |
| 1290 | int i; |
| 1291 | |
| 1292 | rcu_read_lock(); |
| 1293 | un = list_entry_rcu(ulp->list_proc.next, |
| 1294 | struct sem_undo, list_proc); |
| 1295 | if (&un->list_proc == &ulp->list_proc) |
| 1296 | semid = -1; |
| 1297 | else |
| 1298 | semid = un->semid; |
| 1299 | rcu_read_unlock(); |
| 1300 | |
| 1301 | if (semid == -1) |
| 1302 | break; |
| 1303 | |
| 1304 | sma = sem_lock_check(tsk->nsproxy->ipc_ns, un->semid); |
| 1305 | |
| 1306 | /* exit_sem raced with IPC_RMID, nothing to do */ |
| 1307 | if (IS_ERR(sma)) |
| 1308 | continue; |
| 1309 | |
| 1310 | un = lookup_undo(ulp, semid); |
| 1311 | if (un == NULL) { |
| 1312 | /* exit_sem raced with IPC_RMID+semget() that created |
| 1313 | * exactly the same semid. Nothing to do. |
| 1314 | */ |
| 1315 | sem_unlock(sma); |
| 1316 | continue; |
| 1317 | } |
| 1318 | |
| 1319 | /* remove un from the linked lists */ |
| 1320 | assert_spin_locked(&sma->sem_perm.lock); |
| 1321 | list_del(&un->list_id); |
| 1322 | |
| 1323 | spin_lock(&ulp->lock); |
| 1324 | list_del_rcu(&un->list_proc); |
| 1325 | spin_unlock(&ulp->lock); |
| 1326 | |
| 1327 | /* perform adjustments registered in un */ |
| 1328 | for (i = 0; i < sma->sem_nsems; i++) { |
| 1329 | struct sem * semaphore = &sma->sem_base[i]; |
| 1330 | if (un->semadj[i]) { |
| 1331 | semaphore->semval += un->semadj[i]; |
| 1332 | /* |
| 1333 | * Range checks of the new semaphore value, |
| 1334 | * not defined by sus: |
| 1335 | * - Some unices ignore the undo entirely |
| 1336 | * (e.g. HP UX 11i 11.22, Tru64 V5.1) |
| 1337 | * - some cap the value (e.g. FreeBSD caps |
| 1338 | * at 0, but doesn't enforce SEMVMX) |
| 1339 | * |
| 1340 | * Linux caps the semaphore value, both at 0 |
| 1341 | * and at SEMVMX. |
| 1342 | * |
| 1343 | * Manfred <manfred@colorfullife.com> |
| 1344 | */ |
| 1345 | if (semaphore->semval < 0) |
| 1346 | semaphore->semval = 0; |
| 1347 | if (semaphore->semval > SEMVMX) |
| 1348 | semaphore->semval = SEMVMX; |
| 1349 | semaphore->sempid = task_tgid_vnr(current); |
| 1350 | } |
| 1351 | } |
| 1352 | sma->sem_otime = get_seconds(); |
| 1353 | /* maybe some queued-up processes were waiting for this */ |
| 1354 | update_queue(sma); |
| 1355 | sem_unlock(sma); |
| 1356 | |
| 1357 | call_rcu(&un->rcu, free_un); |
| 1358 | } |
| 1359 | kfree(ulp); |
| 1360 | } |
| 1361 | |
| 1362 | #ifdef CONFIG_PROC_FS |
| 1363 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it) |
| 1364 | { |
| 1365 | struct sem_array *sma = it; |
| 1366 | |
| 1367 | return seq_printf(s, |
| 1368 | "%10d %10d %4o %10lu %5u %5u %5u %5u %10lu %10lu\n", |
| 1369 | sma->sem_perm.key, |
| 1370 | sma->sem_perm.id, |
| 1371 | sma->sem_perm.mode, |
| 1372 | sma->sem_nsems, |
| 1373 | sma->sem_perm.uid, |
| 1374 | sma->sem_perm.gid, |
| 1375 | sma->sem_perm.cuid, |
| 1376 | sma->sem_perm.cgid, |
| 1377 | sma->sem_otime, |
| 1378 | sma->sem_ctime); |
| 1379 | } |
| 1380 | #endif |