| 1 | // SPDX-License-Identifier: GPL-2.0 |
| 2 | /* |
| 3 | * linux/ipc/sem.c |
| 4 | * Copyright (C) 1992 Krishna Balasubramanian |
| 5 | * Copyright (C) 1995 Eric Schenk, Bruno Haible |
| 6 | * |
| 7 | * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com> |
| 8 | * |
| 9 | * SMP-threaded, sysctl's added |
| 10 | * (c) 1999 Manfred Spraul <manfred@colorfullife.com> |
| 11 | * Enforced range limit on SEM_UNDO |
| 12 | * (c) 2001 Red Hat Inc |
| 13 | * Lockless wakeup |
| 14 | * (c) 2003 Manfred Spraul <manfred@colorfullife.com> |
| 15 | * (c) 2016 Davidlohr Bueso <dave@stgolabs.net> |
| 16 | * Further wakeup optimizations, documentation |
| 17 | * (c) 2010 Manfred Spraul <manfred@colorfullife.com> |
| 18 | * |
| 19 | * support for audit of ipc object properties and permission changes |
| 20 | * Dustin Kirkland <dustin.kirkland@us.ibm.com> |
| 21 | * |
| 22 | * namespaces support |
| 23 | * OpenVZ, SWsoft Inc. |
| 24 | * Pavel Emelianov <xemul@openvz.org> |
| 25 | * |
| 26 | * Implementation notes: (May 2010) |
| 27 | * This file implements System V semaphores. |
| 28 | * |
| 29 | * User space visible behavior: |
| 30 | * - FIFO ordering for semop() operations (just FIFO, not starvation |
| 31 | * protection) |
| 32 | * - multiple semaphore operations that alter the same semaphore in |
| 33 | * one semop() are handled. |
| 34 | * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and |
| 35 | * SETALL calls. |
| 36 | * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO. |
| 37 | * - undo adjustments at process exit are limited to 0..SEMVMX. |
| 38 | * - namespace are supported. |
| 39 | * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtime by writing |
| 40 | * to /proc/sys/kernel/sem. |
| 41 | * - statistics about the usage are reported in /proc/sysvipc/sem. |
| 42 | * |
| 43 | * Internals: |
| 44 | * - scalability: |
| 45 | * - all global variables are read-mostly. |
| 46 | * - semop() calls and semctl(RMID) are synchronized by RCU. |
| 47 | * - most operations do write operations (actually: spin_lock calls) to |
| 48 | * the per-semaphore array structure. |
| 49 | * Thus: Perfect SMP scaling between independent semaphore arrays. |
| 50 | * If multiple semaphores in one array are used, then cache line |
| 51 | * trashing on the semaphore array spinlock will limit the scaling. |
| 52 | * - semncnt and semzcnt are calculated on demand in count_semcnt() |
| 53 | * - the task that performs a successful semop() scans the list of all |
| 54 | * sleeping tasks and completes any pending operations that can be fulfilled. |
| 55 | * Semaphores are actively given to waiting tasks (necessary for FIFO). |
| 56 | * (see update_queue()) |
| 57 | * - To improve the scalability, the actual wake-up calls are performed after |
| 58 | * dropping all locks. (see wake_up_sem_queue_prepare()) |
| 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 | * - UNDO values are stored in an array (one per process and per |
| 64 | * semaphore array, lazily allocated). For backwards compatibility, multiple |
| 65 | * modes for the UNDO variables are supported (per process, per thread) |
| 66 | * (see copy_semundo, CLONE_SYSVSEM) |
| 67 | * - There are two lists of the pending operations: a per-array list |
| 68 | * and per-semaphore list (stored in the array). This allows to achieve FIFO |
| 69 | * ordering without always scanning all pending operations. |
| 70 | * The worst-case behavior is nevertheless O(N^2) for N wakeups. |
| 71 | */ |
| 72 | |
| 73 | #include <linux/compat.h> |
| 74 | #include <linux/slab.h> |
| 75 | #include <linux/spinlock.h> |
| 76 | #include <linux/init.h> |
| 77 | #include <linux/proc_fs.h> |
| 78 | #include <linux/time.h> |
| 79 | #include <linux/security.h> |
| 80 | #include <linux/syscalls.h> |
| 81 | #include <linux/audit.h> |
| 82 | #include <linux/capability.h> |
| 83 | #include <linux/seq_file.h> |
| 84 | #include <linux/rwsem.h> |
| 85 | #include <linux/nsproxy.h> |
| 86 | #include <linux/ipc_namespace.h> |
| 87 | #include <linux/sched/wake_q.h> |
| 88 | #include <linux/nospec.h> |
| 89 | #include <linux/rhashtable.h> |
| 90 | |
| 91 | #include <linux/uaccess.h> |
| 92 | #include "util.h" |
| 93 | |
| 94 | /* One semaphore structure for each semaphore in the system. */ |
| 95 | struct sem { |
| 96 | int semval; /* current value */ |
| 97 | /* |
| 98 | * PID of the process that last modified the semaphore. For |
| 99 | * Linux, specifically these are: |
| 100 | * - semop |
| 101 | * - semctl, via SETVAL and SETALL. |
| 102 | * - at task exit when performing undo adjustments (see exit_sem). |
| 103 | */ |
| 104 | struct pid *sempid; |
| 105 | spinlock_t lock; /* spinlock for fine-grained semtimedop */ |
| 106 | struct list_head pending_alter; /* pending single-sop operations */ |
| 107 | /* that alter the semaphore */ |
| 108 | struct list_head pending_const; /* pending single-sop operations */ |
| 109 | /* that do not alter the semaphore*/ |
| 110 | time64_t sem_otime; /* candidate for sem_otime */ |
| 111 | } ____cacheline_aligned_in_smp; |
| 112 | |
| 113 | /* One sem_array data structure for each set of semaphores in the system. */ |
| 114 | struct sem_array { |
| 115 | struct kern_ipc_perm sem_perm; /* permissions .. see ipc.h */ |
| 116 | time64_t sem_ctime; /* create/last semctl() time */ |
| 117 | struct list_head pending_alter; /* pending operations */ |
| 118 | /* that alter the array */ |
| 119 | struct list_head pending_const; /* pending complex operations */ |
| 120 | /* that do not alter semvals */ |
| 121 | struct list_head list_id; /* undo requests on this array */ |
| 122 | int sem_nsems; /* no. of semaphores in array */ |
| 123 | int complex_count; /* pending complex operations */ |
| 124 | unsigned int use_global_lock;/* >0: global lock required */ |
| 125 | |
| 126 | struct sem sems[]; |
| 127 | } __randomize_layout; |
| 128 | |
| 129 | /* One queue for each sleeping process in the system. */ |
| 130 | struct sem_queue { |
| 131 | struct list_head list; /* queue of pending operations */ |
| 132 | struct task_struct *sleeper; /* this process */ |
| 133 | struct sem_undo *undo; /* undo structure */ |
| 134 | struct pid *pid; /* process id of requesting process */ |
| 135 | int status; /* completion status of operation */ |
| 136 | struct sembuf *sops; /* array of pending operations */ |
| 137 | struct sembuf *blocking; /* the operation that blocked */ |
| 138 | int nsops; /* number of operations */ |
| 139 | bool alter; /* does *sops alter the array? */ |
| 140 | bool dupsop; /* sops on more than one sem_num */ |
| 141 | }; |
| 142 | |
| 143 | /* Each task has a list of undo requests. They are executed automatically |
| 144 | * when the process exits. |
| 145 | */ |
| 146 | struct sem_undo { |
| 147 | struct list_head list_proc; /* per-process list: * |
| 148 | * all undos from one process |
| 149 | * rcu protected */ |
| 150 | struct rcu_head rcu; /* rcu struct for sem_undo */ |
| 151 | struct sem_undo_list *ulp; /* back ptr to sem_undo_list */ |
| 152 | struct list_head list_id; /* per semaphore array list: |
| 153 | * all undos for one array */ |
| 154 | int semid; /* semaphore set identifier */ |
| 155 | short semadj[]; /* array of adjustments */ |
| 156 | /* one per semaphore */ |
| 157 | }; |
| 158 | |
| 159 | /* sem_undo_list controls shared access to the list of sem_undo structures |
| 160 | * that may be shared among all a CLONE_SYSVSEM task group. |
| 161 | */ |
| 162 | struct sem_undo_list { |
| 163 | refcount_t refcnt; |
| 164 | spinlock_t lock; |
| 165 | struct list_head list_proc; |
| 166 | }; |
| 167 | |
| 168 | |
| 169 | #define sem_ids(ns) ((ns)->ids[IPC_SEM_IDS]) |
| 170 | |
| 171 | static int newary(struct ipc_namespace *, struct ipc_params *); |
| 172 | static void freeary(struct ipc_namespace *, struct kern_ipc_perm *); |
| 173 | #ifdef CONFIG_PROC_FS |
| 174 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it); |
| 175 | #endif |
| 176 | |
| 177 | #define SEMMSL_FAST 256 /* 512 bytes on stack */ |
| 178 | #define SEMOPM_FAST 64 /* ~ 372 bytes on stack */ |
| 179 | |
| 180 | /* |
| 181 | * Switching from the mode suitable for simple ops |
| 182 | * to the mode for complex ops is costly. Therefore: |
| 183 | * use some hysteresis |
| 184 | */ |
| 185 | #define USE_GLOBAL_LOCK_HYSTERESIS 10 |
| 186 | |
| 187 | /* |
| 188 | * Locking: |
| 189 | * a) global sem_lock() for read/write |
| 190 | * sem_undo.id_next, |
| 191 | * sem_array.complex_count, |
| 192 | * sem_array.pending{_alter,_const}, |
| 193 | * sem_array.sem_undo |
| 194 | * |
| 195 | * b) global or semaphore sem_lock() for read/write: |
| 196 | * sem_array.sems[i].pending_{const,alter}: |
| 197 | * |
| 198 | * c) special: |
| 199 | * sem_undo_list.list_proc: |
| 200 | * * undo_list->lock for write |
| 201 | * * rcu for read |
| 202 | * use_global_lock: |
| 203 | * * global sem_lock() for write |
| 204 | * * either local or global sem_lock() for read. |
| 205 | * |
| 206 | * Memory ordering: |
| 207 | * Most ordering is enforced by using spin_lock() and spin_unlock(). |
| 208 | * |
| 209 | * Exceptions: |
| 210 | * 1) use_global_lock: (SEM_BARRIER_1) |
| 211 | * Setting it from non-zero to 0 is a RELEASE, this is ensured by |
| 212 | * using smp_store_release(): Immediately after setting it to 0, |
| 213 | * a simple op can start. |
| 214 | * Testing if it is non-zero is an ACQUIRE, this is ensured by using |
| 215 | * smp_load_acquire(). |
| 216 | * Setting it from 0 to non-zero must be ordered with regards to |
| 217 | * this smp_load_acquire(), this is guaranteed because the smp_load_acquire() |
| 218 | * is inside a spin_lock() and after a write from 0 to non-zero a |
| 219 | * spin_lock()+spin_unlock() is done. |
| 220 | * To prevent the compiler/cpu temporarily writing 0 to use_global_lock, |
| 221 | * READ_ONCE()/WRITE_ONCE() is used. |
| 222 | * |
| 223 | * 2) queue.status: (SEM_BARRIER_2) |
| 224 | * Initialization is done while holding sem_lock(), so no further barrier is |
| 225 | * required. |
| 226 | * Setting it to a result code is a RELEASE, this is ensured by both a |
| 227 | * smp_store_release() (for case a) and while holding sem_lock() |
| 228 | * (for case b). |
| 229 | * The ACQUIRE when reading the result code without holding sem_lock() is |
| 230 | * achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep(). |
| 231 | * (case a above). |
| 232 | * Reading the result code while holding sem_lock() needs no further barriers, |
| 233 | * the locks inside sem_lock() enforce ordering (case b above) |
| 234 | * |
| 235 | * 3) current->state: |
| 236 | * current->state is set to TASK_INTERRUPTIBLE while holding sem_lock(). |
| 237 | * The wakeup is handled using the wake_q infrastructure. wake_q wakeups may |
| 238 | * happen immediately after calling wake_q_add. As wake_q_add_safe() is called |
| 239 | * when holding sem_lock(), no further barriers are required. |
| 240 | * |
| 241 | * See also ipc/mqueue.c for more details on the covered races. |
| 242 | */ |
| 243 | |
| 244 | #define sc_semmsl sem_ctls[0] |
| 245 | #define sc_semmns sem_ctls[1] |
| 246 | #define sc_semopm sem_ctls[2] |
| 247 | #define sc_semmni sem_ctls[3] |
| 248 | |
| 249 | void sem_init_ns(struct ipc_namespace *ns) |
| 250 | { |
| 251 | ns->sc_semmsl = SEMMSL; |
| 252 | ns->sc_semmns = SEMMNS; |
| 253 | ns->sc_semopm = SEMOPM; |
| 254 | ns->sc_semmni = SEMMNI; |
| 255 | ns->used_sems = 0; |
| 256 | ipc_init_ids(&ns->ids[IPC_SEM_IDS]); |
| 257 | } |
| 258 | |
| 259 | #ifdef CONFIG_IPC_NS |
| 260 | void sem_exit_ns(struct ipc_namespace *ns) |
| 261 | { |
| 262 | free_ipcs(ns, &sem_ids(ns), freeary); |
| 263 | idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr); |
| 264 | rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht); |
| 265 | } |
| 266 | #endif |
| 267 | |
| 268 | void __init sem_init(void) |
| 269 | { |
| 270 | sem_init_ns(&init_ipc_ns); |
| 271 | ipc_init_proc_interface("sysvipc/sem", |
| 272 | " key semid perms nsems uid gid cuid cgid otime ctime\n", |
| 273 | IPC_SEM_IDS, sysvipc_sem_proc_show); |
| 274 | } |
| 275 | |
| 276 | /** |
| 277 | * unmerge_queues - unmerge queues, if possible. |
| 278 | * @sma: semaphore array |
| 279 | * |
| 280 | * The function unmerges the wait queues if complex_count is 0. |
| 281 | * It must be called prior to dropping the global semaphore array lock. |
| 282 | */ |
| 283 | static void unmerge_queues(struct sem_array *sma) |
| 284 | { |
| 285 | struct sem_queue *q, *tq; |
| 286 | |
| 287 | /* complex operations still around? */ |
| 288 | if (sma->complex_count) |
| 289 | return; |
| 290 | /* |
| 291 | * We will switch back to simple mode. |
| 292 | * Move all pending operation back into the per-semaphore |
| 293 | * queues. |
| 294 | */ |
| 295 | list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { |
| 296 | struct sem *curr; |
| 297 | curr = &sma->sems[q->sops[0].sem_num]; |
| 298 | |
| 299 | list_add_tail(&q->list, &curr->pending_alter); |
| 300 | } |
| 301 | INIT_LIST_HEAD(&sma->pending_alter); |
| 302 | } |
| 303 | |
| 304 | /** |
| 305 | * merge_queues - merge single semop queues into global queue |
| 306 | * @sma: semaphore array |
| 307 | * |
| 308 | * This function merges all per-semaphore queues into the global queue. |
| 309 | * It is necessary to achieve FIFO ordering for the pending single-sop |
| 310 | * operations when a multi-semop operation must sleep. |
| 311 | * Only the alter operations must be moved, the const operations can stay. |
| 312 | */ |
| 313 | static void merge_queues(struct sem_array *sma) |
| 314 | { |
| 315 | int i; |
| 316 | for (i = 0; i < sma->sem_nsems; i++) { |
| 317 | struct sem *sem = &sma->sems[i]; |
| 318 | |
| 319 | list_splice_init(&sem->pending_alter, &sma->pending_alter); |
| 320 | } |
| 321 | } |
| 322 | |
| 323 | static void sem_rcu_free(struct rcu_head *head) |
| 324 | { |
| 325 | struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu); |
| 326 | struct sem_array *sma = container_of(p, struct sem_array, sem_perm); |
| 327 | |
| 328 | security_sem_free(&sma->sem_perm); |
| 329 | kvfree(sma); |
| 330 | } |
| 331 | |
| 332 | /* |
| 333 | * Enter the mode suitable for non-simple operations: |
| 334 | * Caller must own sem_perm.lock. |
| 335 | */ |
| 336 | static void complexmode_enter(struct sem_array *sma) |
| 337 | { |
| 338 | int i; |
| 339 | struct sem *sem; |
| 340 | |
| 341 | if (sma->use_global_lock > 0) { |
| 342 | /* |
| 343 | * We are already in global lock mode. |
| 344 | * Nothing to do, just reset the |
| 345 | * counter until we return to simple mode. |
| 346 | */ |
| 347 | WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS); |
| 348 | return; |
| 349 | } |
| 350 | WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS); |
| 351 | |
| 352 | for (i = 0; i < sma->sem_nsems; i++) { |
| 353 | sem = &sma->sems[i]; |
| 354 | spin_lock(&sem->lock); |
| 355 | spin_unlock(&sem->lock); |
| 356 | } |
| 357 | } |
| 358 | |
| 359 | /* |
| 360 | * Try to leave the mode that disallows simple operations: |
| 361 | * Caller must own sem_perm.lock. |
| 362 | */ |
| 363 | static void complexmode_tryleave(struct sem_array *sma) |
| 364 | { |
| 365 | if (sma->complex_count) { |
| 366 | /* Complex ops are sleeping. |
| 367 | * We must stay in complex mode |
| 368 | */ |
| 369 | return; |
| 370 | } |
| 371 | if (sma->use_global_lock == 1) { |
| 372 | |
| 373 | /* See SEM_BARRIER_1 for purpose/pairing */ |
| 374 | smp_store_release(&sma->use_global_lock, 0); |
| 375 | } else { |
| 376 | WRITE_ONCE(sma->use_global_lock, |
| 377 | sma->use_global_lock-1); |
| 378 | } |
| 379 | } |
| 380 | |
| 381 | #define SEM_GLOBAL_LOCK (-1) |
| 382 | /* |
| 383 | * If the request contains only one semaphore operation, and there are |
| 384 | * no complex transactions pending, lock only the semaphore involved. |
| 385 | * Otherwise, lock the entire semaphore array, since we either have |
| 386 | * multiple semaphores in our own semops, or we need to look at |
| 387 | * semaphores from other pending complex operations. |
| 388 | */ |
| 389 | static inline int sem_lock(struct sem_array *sma, struct sembuf *sops, |
| 390 | int nsops) |
| 391 | { |
| 392 | struct sem *sem; |
| 393 | int idx; |
| 394 | |
| 395 | if (nsops != 1) { |
| 396 | /* Complex operation - acquire a full lock */ |
| 397 | ipc_lock_object(&sma->sem_perm); |
| 398 | |
| 399 | /* Prevent parallel simple ops */ |
| 400 | complexmode_enter(sma); |
| 401 | return SEM_GLOBAL_LOCK; |
| 402 | } |
| 403 | |
| 404 | /* |
| 405 | * Only one semaphore affected - try to optimize locking. |
| 406 | * Optimized locking is possible if no complex operation |
| 407 | * is either enqueued or processed right now. |
| 408 | * |
| 409 | * Both facts are tracked by use_global_mode. |
| 410 | */ |
| 411 | idx = array_index_nospec(sops->sem_num, sma->sem_nsems); |
| 412 | sem = &sma->sems[idx]; |
| 413 | |
| 414 | /* |
| 415 | * Initial check for use_global_lock. Just an optimization, |
| 416 | * no locking, no memory barrier. |
| 417 | */ |
| 418 | if (!READ_ONCE(sma->use_global_lock)) { |
| 419 | /* |
| 420 | * It appears that no complex operation is around. |
| 421 | * Acquire the per-semaphore lock. |
| 422 | */ |
| 423 | spin_lock(&sem->lock); |
| 424 | |
| 425 | /* see SEM_BARRIER_1 for purpose/pairing */ |
| 426 | if (!smp_load_acquire(&sma->use_global_lock)) { |
| 427 | /* fast path successful! */ |
| 428 | return sops->sem_num; |
| 429 | } |
| 430 | spin_unlock(&sem->lock); |
| 431 | } |
| 432 | |
| 433 | /* slow path: acquire the full lock */ |
| 434 | ipc_lock_object(&sma->sem_perm); |
| 435 | |
| 436 | if (sma->use_global_lock == 0) { |
| 437 | /* |
| 438 | * The use_global_lock mode ended while we waited for |
| 439 | * sma->sem_perm.lock. Thus we must switch to locking |
| 440 | * with sem->lock. |
| 441 | * Unlike in the fast path, there is no need to recheck |
| 442 | * sma->use_global_lock after we have acquired sem->lock: |
| 443 | * We own sma->sem_perm.lock, thus use_global_lock cannot |
| 444 | * change. |
| 445 | */ |
| 446 | spin_lock(&sem->lock); |
| 447 | |
| 448 | ipc_unlock_object(&sma->sem_perm); |
| 449 | return sops->sem_num; |
| 450 | } else { |
| 451 | /* |
| 452 | * Not a false alarm, thus continue to use the global lock |
| 453 | * mode. No need for complexmode_enter(), this was done by |
| 454 | * the caller that has set use_global_mode to non-zero. |
| 455 | */ |
| 456 | return SEM_GLOBAL_LOCK; |
| 457 | } |
| 458 | } |
| 459 | |
| 460 | static inline void sem_unlock(struct sem_array *sma, int locknum) |
| 461 | { |
| 462 | if (locknum == SEM_GLOBAL_LOCK) { |
| 463 | unmerge_queues(sma); |
| 464 | complexmode_tryleave(sma); |
| 465 | ipc_unlock_object(&sma->sem_perm); |
| 466 | } else { |
| 467 | struct sem *sem = &sma->sems[locknum]; |
| 468 | spin_unlock(&sem->lock); |
| 469 | } |
| 470 | } |
| 471 | |
| 472 | /* |
| 473 | * sem_lock_(check_) routines are called in the paths where the rwsem |
| 474 | * is not held. |
| 475 | * |
| 476 | * The caller holds the RCU read lock. |
| 477 | */ |
| 478 | static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id) |
| 479 | { |
| 480 | struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id); |
| 481 | |
| 482 | if (IS_ERR(ipcp)) |
| 483 | return ERR_CAST(ipcp); |
| 484 | |
| 485 | return container_of(ipcp, struct sem_array, sem_perm); |
| 486 | } |
| 487 | |
| 488 | static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns, |
| 489 | int id) |
| 490 | { |
| 491 | struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id); |
| 492 | |
| 493 | if (IS_ERR(ipcp)) |
| 494 | return ERR_CAST(ipcp); |
| 495 | |
| 496 | return container_of(ipcp, struct sem_array, sem_perm); |
| 497 | } |
| 498 | |
| 499 | static inline void sem_lock_and_putref(struct sem_array *sma) |
| 500 | { |
| 501 | sem_lock(sma, NULL, -1); |
| 502 | ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| 503 | } |
| 504 | |
| 505 | static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s) |
| 506 | { |
| 507 | ipc_rmid(&sem_ids(ns), &s->sem_perm); |
| 508 | } |
| 509 | |
| 510 | static struct sem_array *sem_alloc(size_t nsems) |
| 511 | { |
| 512 | struct sem_array *sma; |
| 513 | |
| 514 | if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0])) |
| 515 | return NULL; |
| 516 | |
| 517 | sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL_ACCOUNT); |
| 518 | if (unlikely(!sma)) |
| 519 | return NULL; |
| 520 | |
| 521 | return sma; |
| 522 | } |
| 523 | |
| 524 | /** |
| 525 | * newary - Create a new semaphore set |
| 526 | * @ns: namespace |
| 527 | * @params: ptr to the structure that contains key, semflg and nsems |
| 528 | * |
| 529 | * Called with sem_ids.rwsem held (as a writer) |
| 530 | */ |
| 531 | static int newary(struct ipc_namespace *ns, struct ipc_params *params) |
| 532 | { |
| 533 | int retval; |
| 534 | struct sem_array *sma; |
| 535 | key_t key = params->key; |
| 536 | int nsems = params->u.nsems; |
| 537 | int semflg = params->flg; |
| 538 | int i; |
| 539 | |
| 540 | if (!nsems) |
| 541 | return -EINVAL; |
| 542 | if (ns->used_sems + nsems > ns->sc_semmns) |
| 543 | return -ENOSPC; |
| 544 | |
| 545 | sma = sem_alloc(nsems); |
| 546 | if (!sma) |
| 547 | return -ENOMEM; |
| 548 | |
| 549 | sma->sem_perm.mode = (semflg & S_IRWXUGO); |
| 550 | sma->sem_perm.key = key; |
| 551 | |
| 552 | sma->sem_perm.security = NULL; |
| 553 | retval = security_sem_alloc(&sma->sem_perm); |
| 554 | if (retval) { |
| 555 | kvfree(sma); |
| 556 | return retval; |
| 557 | } |
| 558 | |
| 559 | for (i = 0; i < nsems; i++) { |
| 560 | INIT_LIST_HEAD(&sma->sems[i].pending_alter); |
| 561 | INIT_LIST_HEAD(&sma->sems[i].pending_const); |
| 562 | spin_lock_init(&sma->sems[i].lock); |
| 563 | } |
| 564 | |
| 565 | sma->complex_count = 0; |
| 566 | sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS; |
| 567 | INIT_LIST_HEAD(&sma->pending_alter); |
| 568 | INIT_LIST_HEAD(&sma->pending_const); |
| 569 | INIT_LIST_HEAD(&sma->list_id); |
| 570 | sma->sem_nsems = nsems; |
| 571 | sma->sem_ctime = ktime_get_real_seconds(); |
| 572 | |
| 573 | /* ipc_addid() locks sma upon success. */ |
| 574 | retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni); |
| 575 | if (retval < 0) { |
| 576 | ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| 577 | return retval; |
| 578 | } |
| 579 | ns->used_sems += nsems; |
| 580 | |
| 581 | sem_unlock(sma, -1); |
| 582 | rcu_read_unlock(); |
| 583 | |
| 584 | return sma->sem_perm.id; |
| 585 | } |
| 586 | |
| 587 | |
| 588 | /* |
| 589 | * Called with sem_ids.rwsem and ipcp locked. |
| 590 | */ |
| 591 | static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params) |
| 592 | { |
| 593 | struct sem_array *sma; |
| 594 | |
| 595 | sma = container_of(ipcp, struct sem_array, sem_perm); |
| 596 | if (params->u.nsems > sma->sem_nsems) |
| 597 | return -EINVAL; |
| 598 | |
| 599 | return 0; |
| 600 | } |
| 601 | |
| 602 | long ksys_semget(key_t key, int nsems, int semflg) |
| 603 | { |
| 604 | struct ipc_namespace *ns; |
| 605 | static const struct ipc_ops sem_ops = { |
| 606 | .getnew = newary, |
| 607 | .associate = security_sem_associate, |
| 608 | .more_checks = sem_more_checks, |
| 609 | }; |
| 610 | struct ipc_params sem_params; |
| 611 | |
| 612 | ns = current->nsproxy->ipc_ns; |
| 613 | |
| 614 | if (nsems < 0 || nsems > ns->sc_semmsl) |
| 615 | return -EINVAL; |
| 616 | |
| 617 | sem_params.key = key; |
| 618 | sem_params.flg = semflg; |
| 619 | sem_params.u.nsems = nsems; |
| 620 | |
| 621 | return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params); |
| 622 | } |
| 623 | |
| 624 | SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg) |
| 625 | { |
| 626 | return ksys_semget(key, nsems, semflg); |
| 627 | } |
| 628 | |
| 629 | /** |
| 630 | * perform_atomic_semop[_slow] - Attempt to perform semaphore |
| 631 | * operations on a given array. |
| 632 | * @sma: semaphore array |
| 633 | * @q: struct sem_queue that describes the operation |
| 634 | * |
| 635 | * Caller blocking are as follows, based the value |
| 636 | * indicated by the semaphore operation (sem_op): |
| 637 | * |
| 638 | * (1) >0 never blocks. |
| 639 | * (2) 0 (wait-for-zero operation): semval is non-zero. |
| 640 | * (3) <0 attempting to decrement semval to a value smaller than zero. |
| 641 | * |
| 642 | * Returns 0 if the operation was possible. |
| 643 | * Returns 1 if the operation is impossible, the caller must sleep. |
| 644 | * Returns <0 for error codes. |
| 645 | */ |
| 646 | static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q) |
| 647 | { |
| 648 | int result, sem_op, nsops; |
| 649 | struct pid *pid; |
| 650 | struct sembuf *sop; |
| 651 | struct sem *curr; |
| 652 | struct sembuf *sops; |
| 653 | struct sem_undo *un; |
| 654 | |
| 655 | sops = q->sops; |
| 656 | nsops = q->nsops; |
| 657 | un = q->undo; |
| 658 | |
| 659 | for (sop = sops; sop < sops + nsops; sop++) { |
| 660 | int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); |
| 661 | curr = &sma->sems[idx]; |
| 662 | sem_op = sop->sem_op; |
| 663 | result = curr->semval; |
| 664 | |
| 665 | if (!sem_op && result) |
| 666 | goto would_block; |
| 667 | |
| 668 | result += sem_op; |
| 669 | if (result < 0) |
| 670 | goto would_block; |
| 671 | if (result > SEMVMX) |
| 672 | goto out_of_range; |
| 673 | |
| 674 | if (sop->sem_flg & SEM_UNDO) { |
| 675 | int undo = un->semadj[sop->sem_num] - sem_op; |
| 676 | /* Exceeding the undo range is an error. */ |
| 677 | if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
| 678 | goto out_of_range; |
| 679 | un->semadj[sop->sem_num] = undo; |
| 680 | } |
| 681 | |
| 682 | curr->semval = result; |
| 683 | } |
| 684 | |
| 685 | sop--; |
| 686 | pid = q->pid; |
| 687 | while (sop >= sops) { |
| 688 | ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid); |
| 689 | sop--; |
| 690 | } |
| 691 | |
| 692 | return 0; |
| 693 | |
| 694 | out_of_range: |
| 695 | result = -ERANGE; |
| 696 | goto undo; |
| 697 | |
| 698 | would_block: |
| 699 | q->blocking = sop; |
| 700 | |
| 701 | if (sop->sem_flg & IPC_NOWAIT) |
| 702 | result = -EAGAIN; |
| 703 | else |
| 704 | result = 1; |
| 705 | |
| 706 | undo: |
| 707 | sop--; |
| 708 | while (sop >= sops) { |
| 709 | sem_op = sop->sem_op; |
| 710 | sma->sems[sop->sem_num].semval -= sem_op; |
| 711 | if (sop->sem_flg & SEM_UNDO) |
| 712 | un->semadj[sop->sem_num] += sem_op; |
| 713 | sop--; |
| 714 | } |
| 715 | |
| 716 | return result; |
| 717 | } |
| 718 | |
| 719 | static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q) |
| 720 | { |
| 721 | int result, sem_op, nsops; |
| 722 | struct sembuf *sop; |
| 723 | struct sem *curr; |
| 724 | struct sembuf *sops; |
| 725 | struct sem_undo *un; |
| 726 | |
| 727 | sops = q->sops; |
| 728 | nsops = q->nsops; |
| 729 | un = q->undo; |
| 730 | |
| 731 | if (unlikely(q->dupsop)) |
| 732 | return perform_atomic_semop_slow(sma, q); |
| 733 | |
| 734 | /* |
| 735 | * We scan the semaphore set twice, first to ensure that the entire |
| 736 | * operation can succeed, therefore avoiding any pointless writes |
| 737 | * to shared memory and having to undo such changes in order to block |
| 738 | * until the operations can go through. |
| 739 | */ |
| 740 | for (sop = sops; sop < sops + nsops; sop++) { |
| 741 | int idx = array_index_nospec(sop->sem_num, sma->sem_nsems); |
| 742 | |
| 743 | curr = &sma->sems[idx]; |
| 744 | sem_op = sop->sem_op; |
| 745 | result = curr->semval; |
| 746 | |
| 747 | if (!sem_op && result) |
| 748 | goto would_block; /* wait-for-zero */ |
| 749 | |
| 750 | result += sem_op; |
| 751 | if (result < 0) |
| 752 | goto would_block; |
| 753 | |
| 754 | if (result > SEMVMX) |
| 755 | return -ERANGE; |
| 756 | |
| 757 | if (sop->sem_flg & SEM_UNDO) { |
| 758 | int undo = un->semadj[sop->sem_num] - sem_op; |
| 759 | |
| 760 | /* Exceeding the undo range is an error. */ |
| 761 | if (undo < (-SEMAEM - 1) || undo > SEMAEM) |
| 762 | return -ERANGE; |
| 763 | } |
| 764 | } |
| 765 | |
| 766 | for (sop = sops; sop < sops + nsops; sop++) { |
| 767 | curr = &sma->sems[sop->sem_num]; |
| 768 | sem_op = sop->sem_op; |
| 769 | |
| 770 | if (sop->sem_flg & SEM_UNDO) { |
| 771 | int undo = un->semadj[sop->sem_num] - sem_op; |
| 772 | |
| 773 | un->semadj[sop->sem_num] = undo; |
| 774 | } |
| 775 | curr->semval += sem_op; |
| 776 | ipc_update_pid(&curr->sempid, q->pid); |
| 777 | } |
| 778 | |
| 779 | return 0; |
| 780 | |
| 781 | would_block: |
| 782 | q->blocking = sop; |
| 783 | return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1; |
| 784 | } |
| 785 | |
| 786 | static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error, |
| 787 | struct wake_q_head *wake_q) |
| 788 | { |
| 789 | struct task_struct *sleeper; |
| 790 | |
| 791 | sleeper = get_task_struct(q->sleeper); |
| 792 | |
| 793 | /* see SEM_BARRIER_2 for purpose/pairing */ |
| 794 | smp_store_release(&q->status, error); |
| 795 | |
| 796 | wake_q_add_safe(wake_q, sleeper); |
| 797 | } |
| 798 | |
| 799 | static void unlink_queue(struct sem_array *sma, struct sem_queue *q) |
| 800 | { |
| 801 | list_del(&q->list); |
| 802 | if (q->nsops > 1) |
| 803 | sma->complex_count--; |
| 804 | } |
| 805 | |
| 806 | /** check_restart(sma, q) |
| 807 | * @sma: semaphore array |
| 808 | * @q: the operation that just completed |
| 809 | * |
| 810 | * update_queue is O(N^2) when it restarts scanning the whole queue of |
| 811 | * waiting operations. Therefore this function checks if the restart is |
| 812 | * really necessary. It is called after a previously waiting operation |
| 813 | * modified the array. |
| 814 | * Note that wait-for-zero operations are handled without restart. |
| 815 | */ |
| 816 | static inline int check_restart(struct sem_array *sma, struct sem_queue *q) |
| 817 | { |
| 818 | /* pending complex alter operations are too difficult to analyse */ |
| 819 | if (!list_empty(&sma->pending_alter)) |
| 820 | return 1; |
| 821 | |
| 822 | /* we were a sleeping complex operation. Too difficult */ |
| 823 | if (q->nsops > 1) |
| 824 | return 1; |
| 825 | |
| 826 | /* It is impossible that someone waits for the new value: |
| 827 | * - complex operations always restart. |
| 828 | * - wait-for-zero are handled separately. |
| 829 | * - q is a previously sleeping simple operation that |
| 830 | * altered the array. It must be a decrement, because |
| 831 | * simple increments never sleep. |
| 832 | * - If there are older (higher priority) decrements |
| 833 | * in the queue, then they have observed the original |
| 834 | * semval value and couldn't proceed. The operation |
| 835 | * decremented to value - thus they won't proceed either. |
| 836 | */ |
| 837 | return 0; |
| 838 | } |
| 839 | |
| 840 | /** |
| 841 | * wake_const_ops - wake up non-alter tasks |
| 842 | * @sma: semaphore array. |
| 843 | * @semnum: semaphore that was modified. |
| 844 | * @wake_q: lockless wake-queue head. |
| 845 | * |
| 846 | * wake_const_ops must be called after a semaphore in a semaphore array |
| 847 | * was set to 0. If complex const operations are pending, wake_const_ops must |
| 848 | * be called with semnum = -1, as well as with the number of each modified |
| 849 | * semaphore. |
| 850 | * The tasks that must be woken up are added to @wake_q. The return code |
| 851 | * is stored in q->pid. |
| 852 | * The function returns 1 if at least one operation was completed successfully. |
| 853 | */ |
| 854 | static int wake_const_ops(struct sem_array *sma, int semnum, |
| 855 | struct wake_q_head *wake_q) |
| 856 | { |
| 857 | struct sem_queue *q, *tmp; |
| 858 | struct list_head *pending_list; |
| 859 | int semop_completed = 0; |
| 860 | |
| 861 | if (semnum == -1) |
| 862 | pending_list = &sma->pending_const; |
| 863 | else |
| 864 | pending_list = &sma->sems[semnum].pending_const; |
| 865 | |
| 866 | list_for_each_entry_safe(q, tmp, pending_list, list) { |
| 867 | int error = perform_atomic_semop(sma, q); |
| 868 | |
| 869 | if (error > 0) |
| 870 | continue; |
| 871 | /* operation completed, remove from queue & wakeup */ |
| 872 | unlink_queue(sma, q); |
| 873 | |
| 874 | wake_up_sem_queue_prepare(q, error, wake_q); |
| 875 | if (error == 0) |
| 876 | semop_completed = 1; |
| 877 | } |
| 878 | |
| 879 | return semop_completed; |
| 880 | } |
| 881 | |
| 882 | /** |
| 883 | * do_smart_wakeup_zero - wakeup all wait for zero tasks |
| 884 | * @sma: semaphore array |
| 885 | * @sops: operations that were performed |
| 886 | * @nsops: number of operations |
| 887 | * @wake_q: lockless wake-queue head |
| 888 | * |
| 889 | * Checks all required queue for wait-for-zero operations, based |
| 890 | * on the actual changes that were performed on the semaphore array. |
| 891 | * The function returns 1 if at least one operation was completed successfully. |
| 892 | */ |
| 893 | static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops, |
| 894 | int nsops, struct wake_q_head *wake_q) |
| 895 | { |
| 896 | int i; |
| 897 | int semop_completed = 0; |
| 898 | int got_zero = 0; |
| 899 | |
| 900 | /* first: the per-semaphore queues, if known */ |
| 901 | if (sops) { |
| 902 | for (i = 0; i < nsops; i++) { |
| 903 | int num = sops[i].sem_num; |
| 904 | |
| 905 | if (sma->sems[num].semval == 0) { |
| 906 | got_zero = 1; |
| 907 | semop_completed |= wake_const_ops(sma, num, wake_q); |
| 908 | } |
| 909 | } |
| 910 | } else { |
| 911 | /* |
| 912 | * No sops means modified semaphores not known. |
| 913 | * Assume all were changed. |
| 914 | */ |
| 915 | for (i = 0; i < sma->sem_nsems; i++) { |
| 916 | if (sma->sems[i].semval == 0) { |
| 917 | got_zero = 1; |
| 918 | semop_completed |= wake_const_ops(sma, i, wake_q); |
| 919 | } |
| 920 | } |
| 921 | } |
| 922 | /* |
| 923 | * If one of the modified semaphores got 0, |
| 924 | * then check the global queue, too. |
| 925 | */ |
| 926 | if (got_zero) |
| 927 | semop_completed |= wake_const_ops(sma, -1, wake_q); |
| 928 | |
| 929 | return semop_completed; |
| 930 | } |
| 931 | |
| 932 | |
| 933 | /** |
| 934 | * update_queue - look for tasks that can be completed. |
| 935 | * @sma: semaphore array. |
| 936 | * @semnum: semaphore that was modified. |
| 937 | * @wake_q: lockless wake-queue head. |
| 938 | * |
| 939 | * update_queue must be called after a semaphore in a semaphore array |
| 940 | * was modified. If multiple semaphores were modified, update_queue must |
| 941 | * be called with semnum = -1, as well as with the number of each modified |
| 942 | * semaphore. |
| 943 | * The tasks that must be woken up are added to @wake_q. The return code |
| 944 | * is stored in q->pid. |
| 945 | * The function internally checks if const operations can now succeed. |
| 946 | * |
| 947 | * The function return 1 if at least one semop was completed successfully. |
| 948 | */ |
| 949 | static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q) |
| 950 | { |
| 951 | struct sem_queue *q, *tmp; |
| 952 | struct list_head *pending_list; |
| 953 | int semop_completed = 0; |
| 954 | |
| 955 | if (semnum == -1) |
| 956 | pending_list = &sma->pending_alter; |
| 957 | else |
| 958 | pending_list = &sma->sems[semnum].pending_alter; |
| 959 | |
| 960 | again: |
| 961 | list_for_each_entry_safe(q, tmp, pending_list, list) { |
| 962 | int error, restart; |
| 963 | |
| 964 | /* If we are scanning the single sop, per-semaphore list of |
| 965 | * one semaphore and that semaphore is 0, then it is not |
| 966 | * necessary to scan further: simple increments |
| 967 | * that affect only one entry succeed immediately and cannot |
| 968 | * be in the per semaphore pending queue, and decrements |
| 969 | * cannot be successful if the value is already 0. |
| 970 | */ |
| 971 | if (semnum != -1 && sma->sems[semnum].semval == 0) |
| 972 | break; |
| 973 | |
| 974 | error = perform_atomic_semop(sma, q); |
| 975 | |
| 976 | /* Does q->sleeper still need to sleep? */ |
| 977 | if (error > 0) |
| 978 | continue; |
| 979 | |
| 980 | unlink_queue(sma, q); |
| 981 | |
| 982 | if (error) { |
| 983 | restart = 0; |
| 984 | } else { |
| 985 | semop_completed = 1; |
| 986 | do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q); |
| 987 | restart = check_restart(sma, q); |
| 988 | } |
| 989 | |
| 990 | wake_up_sem_queue_prepare(q, error, wake_q); |
| 991 | if (restart) |
| 992 | goto again; |
| 993 | } |
| 994 | return semop_completed; |
| 995 | } |
| 996 | |
| 997 | /** |
| 998 | * set_semotime - set sem_otime |
| 999 | * @sma: semaphore array |
| 1000 | * @sops: operations that modified the array, may be NULL |
| 1001 | * |
| 1002 | * sem_otime is replicated to avoid cache line trashing. |
| 1003 | * This function sets one instance to the current time. |
| 1004 | */ |
| 1005 | static void set_semotime(struct sem_array *sma, struct sembuf *sops) |
| 1006 | { |
| 1007 | if (sops == NULL) { |
| 1008 | sma->sems[0].sem_otime = ktime_get_real_seconds(); |
| 1009 | } else { |
| 1010 | sma->sems[sops[0].sem_num].sem_otime = |
| 1011 | ktime_get_real_seconds(); |
| 1012 | } |
| 1013 | } |
| 1014 | |
| 1015 | /** |
| 1016 | * do_smart_update - optimized update_queue |
| 1017 | * @sma: semaphore array |
| 1018 | * @sops: operations that were performed |
| 1019 | * @nsops: number of operations |
| 1020 | * @otime: force setting otime |
| 1021 | * @wake_q: lockless wake-queue head |
| 1022 | * |
| 1023 | * do_smart_update() does the required calls to update_queue and wakeup_zero, |
| 1024 | * based on the actual changes that were performed on the semaphore array. |
| 1025 | * Note that the function does not do the actual wake-up: the caller is |
| 1026 | * responsible for calling wake_up_q(). |
| 1027 | * It is safe to perform this call after dropping all locks. |
| 1028 | */ |
| 1029 | static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops, |
| 1030 | int otime, struct wake_q_head *wake_q) |
| 1031 | { |
| 1032 | int i; |
| 1033 | |
| 1034 | otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q); |
| 1035 | |
| 1036 | if (!list_empty(&sma->pending_alter)) { |
| 1037 | /* semaphore array uses the global queue - just process it. */ |
| 1038 | otime |= update_queue(sma, -1, wake_q); |
| 1039 | } else { |
| 1040 | if (!sops) { |
| 1041 | /* |
| 1042 | * No sops, thus the modified semaphores are not |
| 1043 | * known. Check all. |
| 1044 | */ |
| 1045 | for (i = 0; i < sma->sem_nsems; i++) |
| 1046 | otime |= update_queue(sma, i, wake_q); |
| 1047 | } else { |
| 1048 | /* |
| 1049 | * Check the semaphores that were increased: |
| 1050 | * - No complex ops, thus all sleeping ops are |
| 1051 | * decrease. |
| 1052 | * - if we decreased the value, then any sleeping |
| 1053 | * semaphore ops won't be able to run: If the |
| 1054 | * previous value was too small, then the new |
| 1055 | * value will be too small, too. |
| 1056 | */ |
| 1057 | for (i = 0; i < nsops; i++) { |
| 1058 | if (sops[i].sem_op > 0) { |
| 1059 | otime |= update_queue(sma, |
| 1060 | sops[i].sem_num, wake_q); |
| 1061 | } |
| 1062 | } |
| 1063 | } |
| 1064 | } |
| 1065 | if (otime) |
| 1066 | set_semotime(sma, sops); |
| 1067 | } |
| 1068 | |
| 1069 | /* |
| 1070 | * check_qop: Test if a queued operation sleeps on the semaphore semnum |
| 1071 | */ |
| 1072 | static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q, |
| 1073 | bool count_zero) |
| 1074 | { |
| 1075 | struct sembuf *sop = q->blocking; |
| 1076 | |
| 1077 | /* |
| 1078 | * Linux always (since 0.99.10) reported a task as sleeping on all |
| 1079 | * semaphores. This violates SUS, therefore it was changed to the |
| 1080 | * standard compliant behavior. |
| 1081 | * Give the administrators a chance to notice that an application |
| 1082 | * might misbehave because it relies on the Linux behavior. |
| 1083 | */ |
| 1084 | pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n" |
| 1085 | "The task %s (%d) triggered the difference, watch for misbehavior.\n", |
| 1086 | current->comm, task_pid_nr(current)); |
| 1087 | |
| 1088 | if (sop->sem_num != semnum) |
| 1089 | return 0; |
| 1090 | |
| 1091 | if (count_zero && sop->sem_op == 0) |
| 1092 | return 1; |
| 1093 | if (!count_zero && sop->sem_op < 0) |
| 1094 | return 1; |
| 1095 | |
| 1096 | return 0; |
| 1097 | } |
| 1098 | |
| 1099 | /* The following counts are associated to each semaphore: |
| 1100 | * semncnt number of tasks waiting on semval being nonzero |
| 1101 | * semzcnt number of tasks waiting on semval being zero |
| 1102 | * |
| 1103 | * Per definition, a task waits only on the semaphore of the first semop |
| 1104 | * that cannot proceed, even if additional operation would block, too. |
| 1105 | */ |
| 1106 | static int count_semcnt(struct sem_array *sma, ushort semnum, |
| 1107 | bool count_zero) |
| 1108 | { |
| 1109 | struct list_head *l; |
| 1110 | struct sem_queue *q; |
| 1111 | int semcnt; |
| 1112 | |
| 1113 | semcnt = 0; |
| 1114 | /* First: check the simple operations. They are easy to evaluate */ |
| 1115 | if (count_zero) |
| 1116 | l = &sma->sems[semnum].pending_const; |
| 1117 | else |
| 1118 | l = &sma->sems[semnum].pending_alter; |
| 1119 | |
| 1120 | list_for_each_entry(q, l, list) { |
| 1121 | /* all task on a per-semaphore list sleep on exactly |
| 1122 | * that semaphore |
| 1123 | */ |
| 1124 | semcnt++; |
| 1125 | } |
| 1126 | |
| 1127 | /* Then: check the complex operations. */ |
| 1128 | list_for_each_entry(q, &sma->pending_alter, list) { |
| 1129 | semcnt += check_qop(sma, semnum, q, count_zero); |
| 1130 | } |
| 1131 | if (count_zero) { |
| 1132 | list_for_each_entry(q, &sma->pending_const, list) { |
| 1133 | semcnt += check_qop(sma, semnum, q, count_zero); |
| 1134 | } |
| 1135 | } |
| 1136 | return semcnt; |
| 1137 | } |
| 1138 | |
| 1139 | /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked |
| 1140 | * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem |
| 1141 | * remains locked on exit. |
| 1142 | */ |
| 1143 | static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp) |
| 1144 | { |
| 1145 | struct sem_undo *un, *tu; |
| 1146 | struct sem_queue *q, *tq; |
| 1147 | struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
| 1148 | int i; |
| 1149 | DEFINE_WAKE_Q(wake_q); |
| 1150 | |
| 1151 | /* Free the existing undo structures for this semaphore set. */ |
| 1152 | ipc_assert_locked_object(&sma->sem_perm); |
| 1153 | list_for_each_entry_safe(un, tu, &sma->list_id, list_id) { |
| 1154 | list_del(&un->list_id); |
| 1155 | spin_lock(&un->ulp->lock); |
| 1156 | un->semid = -1; |
| 1157 | list_del_rcu(&un->list_proc); |
| 1158 | spin_unlock(&un->ulp->lock); |
| 1159 | kvfree_rcu(un, rcu); |
| 1160 | } |
| 1161 | |
| 1162 | /* Wake up all pending processes and let them fail with EIDRM. */ |
| 1163 | list_for_each_entry_safe(q, tq, &sma->pending_const, list) { |
| 1164 | unlink_queue(sma, q); |
| 1165 | wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
| 1166 | } |
| 1167 | |
| 1168 | list_for_each_entry_safe(q, tq, &sma->pending_alter, list) { |
| 1169 | unlink_queue(sma, q); |
| 1170 | wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
| 1171 | } |
| 1172 | for (i = 0; i < sma->sem_nsems; i++) { |
| 1173 | struct sem *sem = &sma->sems[i]; |
| 1174 | list_for_each_entry_safe(q, tq, &sem->pending_const, list) { |
| 1175 | unlink_queue(sma, q); |
| 1176 | wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
| 1177 | } |
| 1178 | list_for_each_entry_safe(q, tq, &sem->pending_alter, list) { |
| 1179 | unlink_queue(sma, q); |
| 1180 | wake_up_sem_queue_prepare(q, -EIDRM, &wake_q); |
| 1181 | } |
| 1182 | ipc_update_pid(&sem->sempid, NULL); |
| 1183 | } |
| 1184 | |
| 1185 | /* Remove the semaphore set from the IDR */ |
| 1186 | sem_rmid(ns, sma); |
| 1187 | sem_unlock(sma, -1); |
| 1188 | rcu_read_unlock(); |
| 1189 | |
| 1190 | wake_up_q(&wake_q); |
| 1191 | ns->used_sems -= sma->sem_nsems; |
| 1192 | ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| 1193 | } |
| 1194 | |
| 1195 | static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version) |
| 1196 | { |
| 1197 | switch (version) { |
| 1198 | case IPC_64: |
| 1199 | return copy_to_user(buf, in, sizeof(*in)); |
| 1200 | case IPC_OLD: |
| 1201 | { |
| 1202 | struct semid_ds out; |
| 1203 | |
| 1204 | memset(&out, 0, sizeof(out)); |
| 1205 | |
| 1206 | ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm); |
| 1207 | |
| 1208 | out.sem_otime = in->sem_otime; |
| 1209 | out.sem_ctime = in->sem_ctime; |
| 1210 | out.sem_nsems = in->sem_nsems; |
| 1211 | |
| 1212 | return copy_to_user(buf, &out, sizeof(out)); |
| 1213 | } |
| 1214 | default: |
| 1215 | return -EINVAL; |
| 1216 | } |
| 1217 | } |
| 1218 | |
| 1219 | static time64_t get_semotime(struct sem_array *sma) |
| 1220 | { |
| 1221 | int i; |
| 1222 | time64_t res; |
| 1223 | |
| 1224 | res = sma->sems[0].sem_otime; |
| 1225 | for (i = 1; i < sma->sem_nsems; i++) { |
| 1226 | time64_t to = sma->sems[i].sem_otime; |
| 1227 | |
| 1228 | if (to > res) |
| 1229 | res = to; |
| 1230 | } |
| 1231 | return res; |
| 1232 | } |
| 1233 | |
| 1234 | static int semctl_stat(struct ipc_namespace *ns, int semid, |
| 1235 | int cmd, struct semid64_ds *semid64) |
| 1236 | { |
| 1237 | struct sem_array *sma; |
| 1238 | time64_t semotime; |
| 1239 | int err; |
| 1240 | |
| 1241 | memset(semid64, 0, sizeof(*semid64)); |
| 1242 | |
| 1243 | rcu_read_lock(); |
| 1244 | if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) { |
| 1245 | sma = sem_obtain_object(ns, semid); |
| 1246 | if (IS_ERR(sma)) { |
| 1247 | err = PTR_ERR(sma); |
| 1248 | goto out_unlock; |
| 1249 | } |
| 1250 | } else { /* IPC_STAT */ |
| 1251 | sma = sem_obtain_object_check(ns, semid); |
| 1252 | if (IS_ERR(sma)) { |
| 1253 | err = PTR_ERR(sma); |
| 1254 | goto out_unlock; |
| 1255 | } |
| 1256 | } |
| 1257 | |
| 1258 | /* see comment for SHM_STAT_ANY */ |
| 1259 | if (cmd == SEM_STAT_ANY) |
| 1260 | audit_ipc_obj(&sma->sem_perm); |
| 1261 | else { |
| 1262 | err = -EACCES; |
| 1263 | if (ipcperms(ns, &sma->sem_perm, S_IRUGO)) |
| 1264 | goto out_unlock; |
| 1265 | } |
| 1266 | |
| 1267 | err = security_sem_semctl(&sma->sem_perm, cmd); |
| 1268 | if (err) |
| 1269 | goto out_unlock; |
| 1270 | |
| 1271 | ipc_lock_object(&sma->sem_perm); |
| 1272 | |
| 1273 | if (!ipc_valid_object(&sma->sem_perm)) { |
| 1274 | ipc_unlock_object(&sma->sem_perm); |
| 1275 | err = -EIDRM; |
| 1276 | goto out_unlock; |
| 1277 | } |
| 1278 | |
| 1279 | kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm); |
| 1280 | semotime = get_semotime(sma); |
| 1281 | semid64->sem_otime = semotime; |
| 1282 | semid64->sem_ctime = sma->sem_ctime; |
| 1283 | #ifndef CONFIG_64BIT |
| 1284 | semid64->sem_otime_high = semotime >> 32; |
| 1285 | semid64->sem_ctime_high = sma->sem_ctime >> 32; |
| 1286 | #endif |
| 1287 | semid64->sem_nsems = sma->sem_nsems; |
| 1288 | |
| 1289 | if (cmd == IPC_STAT) { |
| 1290 | /* |
| 1291 | * As defined in SUS: |
| 1292 | * Return 0 on success |
| 1293 | */ |
| 1294 | err = 0; |
| 1295 | } else { |
| 1296 | /* |
| 1297 | * SEM_STAT and SEM_STAT_ANY (both Linux specific) |
| 1298 | * Return the full id, including the sequence number |
| 1299 | */ |
| 1300 | err = sma->sem_perm.id; |
| 1301 | } |
| 1302 | ipc_unlock_object(&sma->sem_perm); |
| 1303 | out_unlock: |
| 1304 | rcu_read_unlock(); |
| 1305 | return err; |
| 1306 | } |
| 1307 | |
| 1308 | static int semctl_info(struct ipc_namespace *ns, int semid, |
| 1309 | int cmd, void __user *p) |
| 1310 | { |
| 1311 | struct seminfo seminfo; |
| 1312 | int max_idx; |
| 1313 | int err; |
| 1314 | |
| 1315 | err = security_sem_semctl(NULL, cmd); |
| 1316 | if (err) |
| 1317 | return err; |
| 1318 | |
| 1319 | memset(&seminfo, 0, sizeof(seminfo)); |
| 1320 | seminfo.semmni = ns->sc_semmni; |
| 1321 | seminfo.semmns = ns->sc_semmns; |
| 1322 | seminfo.semmsl = ns->sc_semmsl; |
| 1323 | seminfo.semopm = ns->sc_semopm; |
| 1324 | seminfo.semvmx = SEMVMX; |
| 1325 | seminfo.semmnu = SEMMNU; |
| 1326 | seminfo.semmap = SEMMAP; |
| 1327 | seminfo.semume = SEMUME; |
| 1328 | down_read(&sem_ids(ns).rwsem); |
| 1329 | if (cmd == SEM_INFO) { |
| 1330 | seminfo.semusz = sem_ids(ns).in_use; |
| 1331 | seminfo.semaem = ns->used_sems; |
| 1332 | } else { |
| 1333 | seminfo.semusz = SEMUSZ; |
| 1334 | seminfo.semaem = SEMAEM; |
| 1335 | } |
| 1336 | max_idx = ipc_get_maxidx(&sem_ids(ns)); |
| 1337 | up_read(&sem_ids(ns).rwsem); |
| 1338 | if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) |
| 1339 | return -EFAULT; |
| 1340 | return (max_idx < 0) ? 0 : max_idx; |
| 1341 | } |
| 1342 | |
| 1343 | static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum, |
| 1344 | int val) |
| 1345 | { |
| 1346 | struct sem_undo *un; |
| 1347 | struct sem_array *sma; |
| 1348 | struct sem *curr; |
| 1349 | int err; |
| 1350 | DEFINE_WAKE_Q(wake_q); |
| 1351 | |
| 1352 | if (val > SEMVMX || val < 0) |
| 1353 | return -ERANGE; |
| 1354 | |
| 1355 | rcu_read_lock(); |
| 1356 | sma = sem_obtain_object_check(ns, semid); |
| 1357 | if (IS_ERR(sma)) { |
| 1358 | rcu_read_unlock(); |
| 1359 | return PTR_ERR(sma); |
| 1360 | } |
| 1361 | |
| 1362 | if (semnum < 0 || semnum >= sma->sem_nsems) { |
| 1363 | rcu_read_unlock(); |
| 1364 | return -EINVAL; |
| 1365 | } |
| 1366 | |
| 1367 | |
| 1368 | if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) { |
| 1369 | rcu_read_unlock(); |
| 1370 | return -EACCES; |
| 1371 | } |
| 1372 | |
| 1373 | err = security_sem_semctl(&sma->sem_perm, SETVAL); |
| 1374 | if (err) { |
| 1375 | rcu_read_unlock(); |
| 1376 | return -EACCES; |
| 1377 | } |
| 1378 | |
| 1379 | sem_lock(sma, NULL, -1); |
| 1380 | |
| 1381 | if (!ipc_valid_object(&sma->sem_perm)) { |
| 1382 | sem_unlock(sma, -1); |
| 1383 | rcu_read_unlock(); |
| 1384 | return -EIDRM; |
| 1385 | } |
| 1386 | |
| 1387 | semnum = array_index_nospec(semnum, sma->sem_nsems); |
| 1388 | curr = &sma->sems[semnum]; |
| 1389 | |
| 1390 | ipc_assert_locked_object(&sma->sem_perm); |
| 1391 | list_for_each_entry(un, &sma->list_id, list_id) |
| 1392 | un->semadj[semnum] = 0; |
| 1393 | |
| 1394 | curr->semval = val; |
| 1395 | ipc_update_pid(&curr->sempid, task_tgid(current)); |
| 1396 | sma->sem_ctime = ktime_get_real_seconds(); |
| 1397 | /* maybe some queued-up processes were waiting for this */ |
| 1398 | do_smart_update(sma, NULL, 0, 0, &wake_q); |
| 1399 | sem_unlock(sma, -1); |
| 1400 | rcu_read_unlock(); |
| 1401 | wake_up_q(&wake_q); |
| 1402 | return 0; |
| 1403 | } |
| 1404 | |
| 1405 | static int semctl_main(struct ipc_namespace *ns, int semid, int semnum, |
| 1406 | int cmd, void __user *p) |
| 1407 | { |
| 1408 | struct sem_array *sma; |
| 1409 | struct sem *curr; |
| 1410 | int err, nsems; |
| 1411 | ushort fast_sem_io[SEMMSL_FAST]; |
| 1412 | ushort *sem_io = fast_sem_io; |
| 1413 | DEFINE_WAKE_Q(wake_q); |
| 1414 | |
| 1415 | rcu_read_lock(); |
| 1416 | sma = sem_obtain_object_check(ns, semid); |
| 1417 | if (IS_ERR(sma)) { |
| 1418 | rcu_read_unlock(); |
| 1419 | return PTR_ERR(sma); |
| 1420 | } |
| 1421 | |
| 1422 | nsems = sma->sem_nsems; |
| 1423 | |
| 1424 | err = -EACCES; |
| 1425 | if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO)) |
| 1426 | goto out_rcu_wakeup; |
| 1427 | |
| 1428 | err = security_sem_semctl(&sma->sem_perm, cmd); |
| 1429 | if (err) |
| 1430 | goto out_rcu_wakeup; |
| 1431 | |
| 1432 | switch (cmd) { |
| 1433 | case GETALL: |
| 1434 | { |
| 1435 | ushort __user *array = p; |
| 1436 | int i; |
| 1437 | |
| 1438 | sem_lock(sma, NULL, -1); |
| 1439 | if (!ipc_valid_object(&sma->sem_perm)) { |
| 1440 | err = -EIDRM; |
| 1441 | goto out_unlock; |
| 1442 | } |
| 1443 | if (nsems > SEMMSL_FAST) { |
| 1444 | if (!ipc_rcu_getref(&sma->sem_perm)) { |
| 1445 | err = -EIDRM; |
| 1446 | goto out_unlock; |
| 1447 | } |
| 1448 | sem_unlock(sma, -1); |
| 1449 | rcu_read_unlock(); |
| 1450 | sem_io = kvmalloc_array(nsems, sizeof(ushort), |
| 1451 | GFP_KERNEL); |
| 1452 | if (sem_io == NULL) { |
| 1453 | ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| 1454 | return -ENOMEM; |
| 1455 | } |
| 1456 | |
| 1457 | rcu_read_lock(); |
| 1458 | sem_lock_and_putref(sma); |
| 1459 | if (!ipc_valid_object(&sma->sem_perm)) { |
| 1460 | err = -EIDRM; |
| 1461 | goto out_unlock; |
| 1462 | } |
| 1463 | } |
| 1464 | for (i = 0; i < sma->sem_nsems; i++) |
| 1465 | sem_io[i] = sma->sems[i].semval; |
| 1466 | sem_unlock(sma, -1); |
| 1467 | rcu_read_unlock(); |
| 1468 | err = 0; |
| 1469 | if (copy_to_user(array, sem_io, nsems*sizeof(ushort))) |
| 1470 | err = -EFAULT; |
| 1471 | goto out_free; |
| 1472 | } |
| 1473 | case SETALL: |
| 1474 | { |
| 1475 | int i; |
| 1476 | struct sem_undo *un; |
| 1477 | |
| 1478 | if (!ipc_rcu_getref(&sma->sem_perm)) { |
| 1479 | err = -EIDRM; |
| 1480 | goto out_rcu_wakeup; |
| 1481 | } |
| 1482 | rcu_read_unlock(); |
| 1483 | |
| 1484 | if (nsems > SEMMSL_FAST) { |
| 1485 | sem_io = kvmalloc_array(nsems, sizeof(ushort), |
| 1486 | GFP_KERNEL); |
| 1487 | if (sem_io == NULL) { |
| 1488 | ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| 1489 | return -ENOMEM; |
| 1490 | } |
| 1491 | } |
| 1492 | |
| 1493 | if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) { |
| 1494 | ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| 1495 | err = -EFAULT; |
| 1496 | goto out_free; |
| 1497 | } |
| 1498 | |
| 1499 | for (i = 0; i < nsems; i++) { |
| 1500 | if (sem_io[i] > SEMVMX) { |
| 1501 | ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| 1502 | err = -ERANGE; |
| 1503 | goto out_free; |
| 1504 | } |
| 1505 | } |
| 1506 | rcu_read_lock(); |
| 1507 | sem_lock_and_putref(sma); |
| 1508 | if (!ipc_valid_object(&sma->sem_perm)) { |
| 1509 | err = -EIDRM; |
| 1510 | goto out_unlock; |
| 1511 | } |
| 1512 | |
| 1513 | for (i = 0; i < nsems; i++) { |
| 1514 | sma->sems[i].semval = sem_io[i]; |
| 1515 | ipc_update_pid(&sma->sems[i].sempid, task_tgid(current)); |
| 1516 | } |
| 1517 | |
| 1518 | ipc_assert_locked_object(&sma->sem_perm); |
| 1519 | list_for_each_entry(un, &sma->list_id, list_id) { |
| 1520 | for (i = 0; i < nsems; i++) |
| 1521 | un->semadj[i] = 0; |
| 1522 | } |
| 1523 | sma->sem_ctime = ktime_get_real_seconds(); |
| 1524 | /* maybe some queued-up processes were waiting for this */ |
| 1525 | do_smart_update(sma, NULL, 0, 0, &wake_q); |
| 1526 | err = 0; |
| 1527 | goto out_unlock; |
| 1528 | } |
| 1529 | /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */ |
| 1530 | } |
| 1531 | err = -EINVAL; |
| 1532 | if (semnum < 0 || semnum >= nsems) |
| 1533 | goto out_rcu_wakeup; |
| 1534 | |
| 1535 | sem_lock(sma, NULL, -1); |
| 1536 | if (!ipc_valid_object(&sma->sem_perm)) { |
| 1537 | err = -EIDRM; |
| 1538 | goto out_unlock; |
| 1539 | } |
| 1540 | |
| 1541 | semnum = array_index_nospec(semnum, nsems); |
| 1542 | curr = &sma->sems[semnum]; |
| 1543 | |
| 1544 | switch (cmd) { |
| 1545 | case GETVAL: |
| 1546 | err = curr->semval; |
| 1547 | goto out_unlock; |
| 1548 | case GETPID: |
| 1549 | err = pid_vnr(curr->sempid); |
| 1550 | goto out_unlock; |
| 1551 | case GETNCNT: |
| 1552 | err = count_semcnt(sma, semnum, 0); |
| 1553 | goto out_unlock; |
| 1554 | case GETZCNT: |
| 1555 | err = count_semcnt(sma, semnum, 1); |
| 1556 | goto out_unlock; |
| 1557 | } |
| 1558 | |
| 1559 | out_unlock: |
| 1560 | sem_unlock(sma, -1); |
| 1561 | out_rcu_wakeup: |
| 1562 | rcu_read_unlock(); |
| 1563 | wake_up_q(&wake_q); |
| 1564 | out_free: |
| 1565 | if (sem_io != fast_sem_io) |
| 1566 | kvfree(sem_io); |
| 1567 | return err; |
| 1568 | } |
| 1569 | |
| 1570 | static inline unsigned long |
| 1571 | copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version) |
| 1572 | { |
| 1573 | switch (version) { |
| 1574 | case IPC_64: |
| 1575 | if (copy_from_user(out, buf, sizeof(*out))) |
| 1576 | return -EFAULT; |
| 1577 | return 0; |
| 1578 | case IPC_OLD: |
| 1579 | { |
| 1580 | struct semid_ds tbuf_old; |
| 1581 | |
| 1582 | if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old))) |
| 1583 | return -EFAULT; |
| 1584 | |
| 1585 | out->sem_perm.uid = tbuf_old.sem_perm.uid; |
| 1586 | out->sem_perm.gid = tbuf_old.sem_perm.gid; |
| 1587 | out->sem_perm.mode = tbuf_old.sem_perm.mode; |
| 1588 | |
| 1589 | return 0; |
| 1590 | } |
| 1591 | default: |
| 1592 | return -EINVAL; |
| 1593 | } |
| 1594 | } |
| 1595 | |
| 1596 | /* |
| 1597 | * This function handles some semctl commands which require the rwsem |
| 1598 | * to be held in write mode. |
| 1599 | * NOTE: no locks must be held, the rwsem is taken inside this function. |
| 1600 | */ |
| 1601 | static int semctl_down(struct ipc_namespace *ns, int semid, |
| 1602 | int cmd, struct semid64_ds *semid64) |
| 1603 | { |
| 1604 | struct sem_array *sma; |
| 1605 | int err; |
| 1606 | struct kern_ipc_perm *ipcp; |
| 1607 | |
| 1608 | down_write(&sem_ids(ns).rwsem); |
| 1609 | rcu_read_lock(); |
| 1610 | |
| 1611 | ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd, |
| 1612 | &semid64->sem_perm, 0); |
| 1613 | if (IS_ERR(ipcp)) { |
| 1614 | err = PTR_ERR(ipcp); |
| 1615 | goto out_unlock1; |
| 1616 | } |
| 1617 | |
| 1618 | sma = container_of(ipcp, struct sem_array, sem_perm); |
| 1619 | |
| 1620 | err = security_sem_semctl(&sma->sem_perm, cmd); |
| 1621 | if (err) |
| 1622 | goto out_unlock1; |
| 1623 | |
| 1624 | switch (cmd) { |
| 1625 | case IPC_RMID: |
| 1626 | sem_lock(sma, NULL, -1); |
| 1627 | /* freeary unlocks the ipc object and rcu */ |
| 1628 | freeary(ns, ipcp); |
| 1629 | goto out_up; |
| 1630 | case IPC_SET: |
| 1631 | sem_lock(sma, NULL, -1); |
| 1632 | err = ipc_update_perm(&semid64->sem_perm, ipcp); |
| 1633 | if (err) |
| 1634 | goto out_unlock0; |
| 1635 | sma->sem_ctime = ktime_get_real_seconds(); |
| 1636 | break; |
| 1637 | default: |
| 1638 | err = -EINVAL; |
| 1639 | goto out_unlock1; |
| 1640 | } |
| 1641 | |
| 1642 | out_unlock0: |
| 1643 | sem_unlock(sma, -1); |
| 1644 | out_unlock1: |
| 1645 | rcu_read_unlock(); |
| 1646 | out_up: |
| 1647 | up_write(&sem_ids(ns).rwsem); |
| 1648 | return err; |
| 1649 | } |
| 1650 | |
| 1651 | static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version) |
| 1652 | { |
| 1653 | struct ipc_namespace *ns; |
| 1654 | void __user *p = (void __user *)arg; |
| 1655 | struct semid64_ds semid64; |
| 1656 | int err; |
| 1657 | |
| 1658 | if (semid < 0) |
| 1659 | return -EINVAL; |
| 1660 | |
| 1661 | ns = current->nsproxy->ipc_ns; |
| 1662 | |
| 1663 | switch (cmd) { |
| 1664 | case IPC_INFO: |
| 1665 | case SEM_INFO: |
| 1666 | return semctl_info(ns, semid, cmd, p); |
| 1667 | case IPC_STAT: |
| 1668 | case SEM_STAT: |
| 1669 | case SEM_STAT_ANY: |
| 1670 | err = semctl_stat(ns, semid, cmd, &semid64); |
| 1671 | if (err < 0) |
| 1672 | return err; |
| 1673 | if (copy_semid_to_user(p, &semid64, version)) |
| 1674 | err = -EFAULT; |
| 1675 | return err; |
| 1676 | case GETALL: |
| 1677 | case GETVAL: |
| 1678 | case GETPID: |
| 1679 | case GETNCNT: |
| 1680 | case GETZCNT: |
| 1681 | case SETALL: |
| 1682 | return semctl_main(ns, semid, semnum, cmd, p); |
| 1683 | case SETVAL: { |
| 1684 | int val; |
| 1685 | #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN) |
| 1686 | /* big-endian 64bit */ |
| 1687 | val = arg >> 32; |
| 1688 | #else |
| 1689 | /* 32bit or little-endian 64bit */ |
| 1690 | val = arg; |
| 1691 | #endif |
| 1692 | return semctl_setval(ns, semid, semnum, val); |
| 1693 | } |
| 1694 | case IPC_SET: |
| 1695 | if (copy_semid_from_user(&semid64, p, version)) |
| 1696 | return -EFAULT; |
| 1697 | fallthrough; |
| 1698 | case IPC_RMID: |
| 1699 | return semctl_down(ns, semid, cmd, &semid64); |
| 1700 | default: |
| 1701 | return -EINVAL; |
| 1702 | } |
| 1703 | } |
| 1704 | |
| 1705 | SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) |
| 1706 | { |
| 1707 | return ksys_semctl(semid, semnum, cmd, arg, IPC_64); |
| 1708 | } |
| 1709 | |
| 1710 | #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION |
| 1711 | long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg) |
| 1712 | { |
| 1713 | int version = ipc_parse_version(&cmd); |
| 1714 | |
| 1715 | return ksys_semctl(semid, semnum, cmd, arg, version); |
| 1716 | } |
| 1717 | |
| 1718 | SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg) |
| 1719 | { |
| 1720 | return ksys_old_semctl(semid, semnum, cmd, arg); |
| 1721 | } |
| 1722 | #endif |
| 1723 | |
| 1724 | #ifdef CONFIG_COMPAT |
| 1725 | |
| 1726 | struct compat_semid_ds { |
| 1727 | struct compat_ipc_perm sem_perm; |
| 1728 | old_time32_t sem_otime; |
| 1729 | old_time32_t sem_ctime; |
| 1730 | compat_uptr_t sem_base; |
| 1731 | compat_uptr_t sem_pending; |
| 1732 | compat_uptr_t sem_pending_last; |
| 1733 | compat_uptr_t undo; |
| 1734 | unsigned short sem_nsems; |
| 1735 | }; |
| 1736 | |
| 1737 | static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf, |
| 1738 | int version) |
| 1739 | { |
| 1740 | memset(out, 0, sizeof(*out)); |
| 1741 | if (version == IPC_64) { |
| 1742 | struct compat_semid64_ds __user *p = buf; |
| 1743 | return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm); |
| 1744 | } else { |
| 1745 | struct compat_semid_ds __user *p = buf; |
| 1746 | return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm); |
| 1747 | } |
| 1748 | } |
| 1749 | |
| 1750 | static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in, |
| 1751 | int version) |
| 1752 | { |
| 1753 | if (version == IPC_64) { |
| 1754 | struct compat_semid64_ds v; |
| 1755 | memset(&v, 0, sizeof(v)); |
| 1756 | to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm); |
| 1757 | v.sem_otime = lower_32_bits(in->sem_otime); |
| 1758 | v.sem_otime_high = upper_32_bits(in->sem_otime); |
| 1759 | v.sem_ctime = lower_32_bits(in->sem_ctime); |
| 1760 | v.sem_ctime_high = upper_32_bits(in->sem_ctime); |
| 1761 | v.sem_nsems = in->sem_nsems; |
| 1762 | return copy_to_user(buf, &v, sizeof(v)); |
| 1763 | } else { |
| 1764 | struct compat_semid_ds v; |
| 1765 | memset(&v, 0, sizeof(v)); |
| 1766 | to_compat_ipc_perm(&v.sem_perm, &in->sem_perm); |
| 1767 | v.sem_otime = in->sem_otime; |
| 1768 | v.sem_ctime = in->sem_ctime; |
| 1769 | v.sem_nsems = in->sem_nsems; |
| 1770 | return copy_to_user(buf, &v, sizeof(v)); |
| 1771 | } |
| 1772 | } |
| 1773 | |
| 1774 | static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version) |
| 1775 | { |
| 1776 | void __user *p = compat_ptr(arg); |
| 1777 | struct ipc_namespace *ns; |
| 1778 | struct semid64_ds semid64; |
| 1779 | int err; |
| 1780 | |
| 1781 | ns = current->nsproxy->ipc_ns; |
| 1782 | |
| 1783 | if (semid < 0) |
| 1784 | return -EINVAL; |
| 1785 | |
| 1786 | switch (cmd & (~IPC_64)) { |
| 1787 | case IPC_INFO: |
| 1788 | case SEM_INFO: |
| 1789 | return semctl_info(ns, semid, cmd, p); |
| 1790 | case IPC_STAT: |
| 1791 | case SEM_STAT: |
| 1792 | case SEM_STAT_ANY: |
| 1793 | err = semctl_stat(ns, semid, cmd, &semid64); |
| 1794 | if (err < 0) |
| 1795 | return err; |
| 1796 | if (copy_compat_semid_to_user(p, &semid64, version)) |
| 1797 | err = -EFAULT; |
| 1798 | return err; |
| 1799 | case GETVAL: |
| 1800 | case GETPID: |
| 1801 | case GETNCNT: |
| 1802 | case GETZCNT: |
| 1803 | case GETALL: |
| 1804 | case SETALL: |
| 1805 | return semctl_main(ns, semid, semnum, cmd, p); |
| 1806 | case SETVAL: |
| 1807 | return semctl_setval(ns, semid, semnum, arg); |
| 1808 | case IPC_SET: |
| 1809 | if (copy_compat_semid_from_user(&semid64, p, version)) |
| 1810 | return -EFAULT; |
| 1811 | fallthrough; |
| 1812 | case IPC_RMID: |
| 1813 | return semctl_down(ns, semid, cmd, &semid64); |
| 1814 | default: |
| 1815 | return -EINVAL; |
| 1816 | } |
| 1817 | } |
| 1818 | |
| 1819 | COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg) |
| 1820 | { |
| 1821 | return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64); |
| 1822 | } |
| 1823 | |
| 1824 | #ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION |
| 1825 | long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg) |
| 1826 | { |
| 1827 | int version = compat_ipc_parse_version(&cmd); |
| 1828 | |
| 1829 | return compat_ksys_semctl(semid, semnum, cmd, arg, version); |
| 1830 | } |
| 1831 | |
| 1832 | COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg) |
| 1833 | { |
| 1834 | return compat_ksys_old_semctl(semid, semnum, cmd, arg); |
| 1835 | } |
| 1836 | #endif |
| 1837 | #endif |
| 1838 | |
| 1839 | /* If the task doesn't already have a undo_list, then allocate one |
| 1840 | * here. We guarantee there is only one thread using this undo list, |
| 1841 | * and current is THE ONE |
| 1842 | * |
| 1843 | * If this allocation and assignment succeeds, but later |
| 1844 | * portions of this code fail, there is no need to free the sem_undo_list. |
| 1845 | * Just let it stay associated with the task, and it'll be freed later |
| 1846 | * at exit time. |
| 1847 | * |
| 1848 | * This can block, so callers must hold no locks. |
| 1849 | */ |
| 1850 | static inline int get_undo_list(struct sem_undo_list **undo_listp) |
| 1851 | { |
| 1852 | struct sem_undo_list *undo_list; |
| 1853 | |
| 1854 | undo_list = current->sysvsem.undo_list; |
| 1855 | if (!undo_list) { |
| 1856 | undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL_ACCOUNT); |
| 1857 | if (undo_list == NULL) |
| 1858 | return -ENOMEM; |
| 1859 | spin_lock_init(&undo_list->lock); |
| 1860 | refcount_set(&undo_list->refcnt, 1); |
| 1861 | INIT_LIST_HEAD(&undo_list->list_proc); |
| 1862 | |
| 1863 | current->sysvsem.undo_list = undo_list; |
| 1864 | } |
| 1865 | *undo_listp = undo_list; |
| 1866 | return 0; |
| 1867 | } |
| 1868 | |
| 1869 | static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid) |
| 1870 | { |
| 1871 | struct sem_undo *un; |
| 1872 | |
| 1873 | list_for_each_entry_rcu(un, &ulp->list_proc, list_proc, |
| 1874 | spin_is_locked(&ulp->lock)) { |
| 1875 | if (un->semid == semid) |
| 1876 | return un; |
| 1877 | } |
| 1878 | return NULL; |
| 1879 | } |
| 1880 | |
| 1881 | static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid) |
| 1882 | { |
| 1883 | struct sem_undo *un; |
| 1884 | |
| 1885 | assert_spin_locked(&ulp->lock); |
| 1886 | |
| 1887 | un = __lookup_undo(ulp, semid); |
| 1888 | if (un) { |
| 1889 | list_del_rcu(&un->list_proc); |
| 1890 | list_add_rcu(&un->list_proc, &ulp->list_proc); |
| 1891 | } |
| 1892 | return un; |
| 1893 | } |
| 1894 | |
| 1895 | /** |
| 1896 | * find_alloc_undo - lookup (and if not present create) undo array |
| 1897 | * @ns: namespace |
| 1898 | * @semid: semaphore array id |
| 1899 | * |
| 1900 | * The function looks up (and if not present creates) the undo structure. |
| 1901 | * The size of the undo structure depends on the size of the semaphore |
| 1902 | * array, thus the alloc path is not that straightforward. |
| 1903 | * Lifetime-rules: sem_undo is rcu-protected, on success, the function |
| 1904 | * performs a rcu_read_lock(). |
| 1905 | */ |
| 1906 | static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid) |
| 1907 | { |
| 1908 | struct sem_array *sma; |
| 1909 | struct sem_undo_list *ulp; |
| 1910 | struct sem_undo *un, *new; |
| 1911 | int nsems, error; |
| 1912 | |
| 1913 | error = get_undo_list(&ulp); |
| 1914 | if (error) |
| 1915 | return ERR_PTR(error); |
| 1916 | |
| 1917 | rcu_read_lock(); |
| 1918 | spin_lock(&ulp->lock); |
| 1919 | un = lookup_undo(ulp, semid); |
| 1920 | spin_unlock(&ulp->lock); |
| 1921 | if (likely(un != NULL)) |
| 1922 | goto out; |
| 1923 | |
| 1924 | /* no undo structure around - allocate one. */ |
| 1925 | /* step 1: figure out the size of the semaphore array */ |
| 1926 | sma = sem_obtain_object_check(ns, semid); |
| 1927 | if (IS_ERR(sma)) { |
| 1928 | rcu_read_unlock(); |
| 1929 | return ERR_CAST(sma); |
| 1930 | } |
| 1931 | |
| 1932 | nsems = sma->sem_nsems; |
| 1933 | if (!ipc_rcu_getref(&sma->sem_perm)) { |
| 1934 | rcu_read_unlock(); |
| 1935 | un = ERR_PTR(-EIDRM); |
| 1936 | goto out; |
| 1937 | } |
| 1938 | rcu_read_unlock(); |
| 1939 | |
| 1940 | /* step 2: allocate new undo structure */ |
| 1941 | new = kvzalloc(struct_size(new, semadj, nsems), GFP_KERNEL_ACCOUNT); |
| 1942 | if (!new) { |
| 1943 | ipc_rcu_putref(&sma->sem_perm, sem_rcu_free); |
| 1944 | return ERR_PTR(-ENOMEM); |
| 1945 | } |
| 1946 | |
| 1947 | /* step 3: Acquire the lock on semaphore array */ |
| 1948 | rcu_read_lock(); |
| 1949 | sem_lock_and_putref(sma); |
| 1950 | if (!ipc_valid_object(&sma->sem_perm)) { |
| 1951 | sem_unlock(sma, -1); |
| 1952 | rcu_read_unlock(); |
| 1953 | kvfree(new); |
| 1954 | un = ERR_PTR(-EIDRM); |
| 1955 | goto out; |
| 1956 | } |
| 1957 | spin_lock(&ulp->lock); |
| 1958 | |
| 1959 | /* |
| 1960 | * step 4: check for races: did someone else allocate the undo struct? |
| 1961 | */ |
| 1962 | un = lookup_undo(ulp, semid); |
| 1963 | if (un) { |
| 1964 | spin_unlock(&ulp->lock); |
| 1965 | kvfree(new); |
| 1966 | goto success; |
| 1967 | } |
| 1968 | /* step 5: initialize & link new undo structure */ |
| 1969 | new->ulp = ulp; |
| 1970 | new->semid = semid; |
| 1971 | assert_spin_locked(&ulp->lock); |
| 1972 | list_add_rcu(&new->list_proc, &ulp->list_proc); |
| 1973 | ipc_assert_locked_object(&sma->sem_perm); |
| 1974 | list_add(&new->list_id, &sma->list_id); |
| 1975 | un = new; |
| 1976 | spin_unlock(&ulp->lock); |
| 1977 | success: |
| 1978 | sem_unlock(sma, -1); |
| 1979 | out: |
| 1980 | return un; |
| 1981 | } |
| 1982 | |
| 1983 | long __do_semtimedop(int semid, struct sembuf *sops, |
| 1984 | unsigned nsops, const struct timespec64 *timeout, |
| 1985 | struct ipc_namespace *ns) |
| 1986 | { |
| 1987 | int error = -EINVAL; |
| 1988 | struct sem_array *sma; |
| 1989 | struct sembuf *sop; |
| 1990 | struct sem_undo *un; |
| 1991 | int max, locknum; |
| 1992 | bool undos = false, alter = false, dupsop = false; |
| 1993 | struct sem_queue queue; |
| 1994 | unsigned long dup = 0; |
| 1995 | ktime_t expires, *exp = NULL; |
| 1996 | bool timed_out = false; |
| 1997 | |
| 1998 | if (nsops < 1 || semid < 0) |
| 1999 | return -EINVAL; |
| 2000 | if (nsops > ns->sc_semopm) |
| 2001 | return -E2BIG; |
| 2002 | |
| 2003 | if (timeout) { |
| 2004 | if (!timespec64_valid(timeout)) |
| 2005 | return -EINVAL; |
| 2006 | expires = ktime_add_safe(ktime_get(), |
| 2007 | timespec64_to_ktime(*timeout)); |
| 2008 | exp = &expires; |
| 2009 | } |
| 2010 | |
| 2011 | |
| 2012 | max = 0; |
| 2013 | for (sop = sops; sop < sops + nsops; sop++) { |
| 2014 | unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG); |
| 2015 | |
| 2016 | if (sop->sem_num >= max) |
| 2017 | max = sop->sem_num; |
| 2018 | if (sop->sem_flg & SEM_UNDO) |
| 2019 | undos = true; |
| 2020 | if (dup & mask) { |
| 2021 | /* |
| 2022 | * There was a previous alter access that appears |
| 2023 | * to have accessed the same semaphore, thus use |
| 2024 | * the dupsop logic. "appears", because the detection |
| 2025 | * can only check % BITS_PER_LONG. |
| 2026 | */ |
| 2027 | dupsop = true; |
| 2028 | } |
| 2029 | if (sop->sem_op != 0) { |
| 2030 | alter = true; |
| 2031 | dup |= mask; |
| 2032 | } |
| 2033 | } |
| 2034 | |
| 2035 | if (undos) { |
| 2036 | /* On success, find_alloc_undo takes the rcu_read_lock */ |
| 2037 | un = find_alloc_undo(ns, semid); |
| 2038 | if (IS_ERR(un)) { |
| 2039 | error = PTR_ERR(un); |
| 2040 | goto out; |
| 2041 | } |
| 2042 | } else { |
| 2043 | un = NULL; |
| 2044 | rcu_read_lock(); |
| 2045 | } |
| 2046 | |
| 2047 | sma = sem_obtain_object_check(ns, semid); |
| 2048 | if (IS_ERR(sma)) { |
| 2049 | rcu_read_unlock(); |
| 2050 | error = PTR_ERR(sma); |
| 2051 | goto out; |
| 2052 | } |
| 2053 | |
| 2054 | error = -EFBIG; |
| 2055 | if (max >= sma->sem_nsems) { |
| 2056 | rcu_read_unlock(); |
| 2057 | goto out; |
| 2058 | } |
| 2059 | |
| 2060 | error = -EACCES; |
| 2061 | if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) { |
| 2062 | rcu_read_unlock(); |
| 2063 | goto out; |
| 2064 | } |
| 2065 | |
| 2066 | error = security_sem_semop(&sma->sem_perm, sops, nsops, alter); |
| 2067 | if (error) { |
| 2068 | rcu_read_unlock(); |
| 2069 | goto out; |
| 2070 | } |
| 2071 | |
| 2072 | error = -EIDRM; |
| 2073 | locknum = sem_lock(sma, sops, nsops); |
| 2074 | /* |
| 2075 | * We eventually might perform the following check in a lockless |
| 2076 | * fashion, considering ipc_valid_object() locking constraints. |
| 2077 | * If nsops == 1 and there is no contention for sem_perm.lock, then |
| 2078 | * only a per-semaphore lock is held and it's OK to proceed with the |
| 2079 | * check below. More details on the fine grained locking scheme |
| 2080 | * entangled here and why it's RMID race safe on comments at sem_lock() |
| 2081 | */ |
| 2082 | if (!ipc_valid_object(&sma->sem_perm)) |
| 2083 | goto out_unlock; |
| 2084 | /* |
| 2085 | * semid identifiers are not unique - find_alloc_undo may have |
| 2086 | * allocated an undo structure, it was invalidated by an RMID |
| 2087 | * and now a new array with received the same id. Check and fail. |
| 2088 | * This case can be detected checking un->semid. The existence of |
| 2089 | * "un" itself is guaranteed by rcu. |
| 2090 | */ |
| 2091 | if (un && un->semid == -1) |
| 2092 | goto out_unlock; |
| 2093 | |
| 2094 | queue.sops = sops; |
| 2095 | queue.nsops = nsops; |
| 2096 | queue.undo = un; |
| 2097 | queue.pid = task_tgid(current); |
| 2098 | queue.alter = alter; |
| 2099 | queue.dupsop = dupsop; |
| 2100 | |
| 2101 | error = perform_atomic_semop(sma, &queue); |
| 2102 | if (error == 0) { /* non-blocking successful path */ |
| 2103 | DEFINE_WAKE_Q(wake_q); |
| 2104 | |
| 2105 | /* |
| 2106 | * If the operation was successful, then do |
| 2107 | * the required updates. |
| 2108 | */ |
| 2109 | if (alter) |
| 2110 | do_smart_update(sma, sops, nsops, 1, &wake_q); |
| 2111 | else |
| 2112 | set_semotime(sma, sops); |
| 2113 | |
| 2114 | sem_unlock(sma, locknum); |
| 2115 | rcu_read_unlock(); |
| 2116 | wake_up_q(&wake_q); |
| 2117 | |
| 2118 | goto out; |
| 2119 | } |
| 2120 | if (error < 0) /* non-blocking error path */ |
| 2121 | goto out_unlock; |
| 2122 | |
| 2123 | /* |
| 2124 | * We need to sleep on this operation, so we put the current |
| 2125 | * task into the pending queue and go to sleep. |
| 2126 | */ |
| 2127 | if (nsops == 1) { |
| 2128 | struct sem *curr; |
| 2129 | int idx = array_index_nospec(sops->sem_num, sma->sem_nsems); |
| 2130 | curr = &sma->sems[idx]; |
| 2131 | |
| 2132 | if (alter) { |
| 2133 | if (sma->complex_count) { |
| 2134 | list_add_tail(&queue.list, |
| 2135 | &sma->pending_alter); |
| 2136 | } else { |
| 2137 | |
| 2138 | list_add_tail(&queue.list, |
| 2139 | &curr->pending_alter); |
| 2140 | } |
| 2141 | } else { |
| 2142 | list_add_tail(&queue.list, &curr->pending_const); |
| 2143 | } |
| 2144 | } else { |
| 2145 | if (!sma->complex_count) |
| 2146 | merge_queues(sma); |
| 2147 | |
| 2148 | if (alter) |
| 2149 | list_add_tail(&queue.list, &sma->pending_alter); |
| 2150 | else |
| 2151 | list_add_tail(&queue.list, &sma->pending_const); |
| 2152 | |
| 2153 | sma->complex_count++; |
| 2154 | } |
| 2155 | |
| 2156 | do { |
| 2157 | /* memory ordering ensured by the lock in sem_lock() */ |
| 2158 | WRITE_ONCE(queue.status, -EINTR); |
| 2159 | queue.sleeper = current; |
| 2160 | |
| 2161 | /* memory ordering is ensured by the lock in sem_lock() */ |
| 2162 | __set_current_state(TASK_INTERRUPTIBLE); |
| 2163 | sem_unlock(sma, locknum); |
| 2164 | rcu_read_unlock(); |
| 2165 | |
| 2166 | timed_out = !schedule_hrtimeout_range(exp, |
| 2167 | current->timer_slack_ns, HRTIMER_MODE_ABS); |
| 2168 | |
| 2169 | /* |
| 2170 | * fastpath: the semop has completed, either successfully or |
| 2171 | * not, from the syscall pov, is quite irrelevant to us at this |
| 2172 | * point; we're done. |
| 2173 | * |
| 2174 | * We _do_ care, nonetheless, about being awoken by a signal or |
| 2175 | * spuriously. The queue.status is checked again in the |
| 2176 | * slowpath (aka after taking sem_lock), such that we can detect |
| 2177 | * scenarios where we were awakened externally, during the |
| 2178 | * window between wake_q_add() and wake_up_q(). |
| 2179 | */ |
| 2180 | rcu_read_lock(); |
| 2181 | error = READ_ONCE(queue.status); |
| 2182 | if (error != -EINTR) { |
| 2183 | /* see SEM_BARRIER_2 for purpose/pairing */ |
| 2184 | smp_acquire__after_ctrl_dep(); |
| 2185 | rcu_read_unlock(); |
| 2186 | goto out; |
| 2187 | } |
| 2188 | |
| 2189 | locknum = sem_lock(sma, sops, nsops); |
| 2190 | |
| 2191 | if (!ipc_valid_object(&sma->sem_perm)) |
| 2192 | goto out_unlock; |
| 2193 | |
| 2194 | /* |
| 2195 | * No necessity for any barrier: We are protect by sem_lock() |
| 2196 | */ |
| 2197 | error = READ_ONCE(queue.status); |
| 2198 | |
| 2199 | /* |
| 2200 | * If queue.status != -EINTR we are woken up by another process. |
| 2201 | * Leave without unlink_queue(), but with sem_unlock(). |
| 2202 | */ |
| 2203 | if (error != -EINTR) |
| 2204 | goto out_unlock; |
| 2205 | |
| 2206 | /* |
| 2207 | * If an interrupt occurred we have to clean up the queue. |
| 2208 | */ |
| 2209 | if (timed_out) |
| 2210 | error = -EAGAIN; |
| 2211 | } while (error == -EINTR && !signal_pending(current)); /* spurious */ |
| 2212 | |
| 2213 | unlink_queue(sma, &queue); |
| 2214 | |
| 2215 | out_unlock: |
| 2216 | sem_unlock(sma, locknum); |
| 2217 | rcu_read_unlock(); |
| 2218 | out: |
| 2219 | return error; |
| 2220 | } |
| 2221 | |
| 2222 | static long do_semtimedop(int semid, struct sembuf __user *tsops, |
| 2223 | unsigned nsops, const struct timespec64 *timeout) |
| 2224 | { |
| 2225 | struct sembuf fast_sops[SEMOPM_FAST]; |
| 2226 | struct sembuf *sops = fast_sops; |
| 2227 | struct ipc_namespace *ns; |
| 2228 | int ret; |
| 2229 | |
| 2230 | ns = current->nsproxy->ipc_ns; |
| 2231 | if (nsops > ns->sc_semopm) |
| 2232 | return -E2BIG; |
| 2233 | if (nsops < 1) |
| 2234 | return -EINVAL; |
| 2235 | |
| 2236 | if (nsops > SEMOPM_FAST) { |
| 2237 | sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL); |
| 2238 | if (sops == NULL) |
| 2239 | return -ENOMEM; |
| 2240 | } |
| 2241 | |
| 2242 | if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) { |
| 2243 | ret = -EFAULT; |
| 2244 | goto out_free; |
| 2245 | } |
| 2246 | |
| 2247 | ret = __do_semtimedop(semid, sops, nsops, timeout, ns); |
| 2248 | |
| 2249 | out_free: |
| 2250 | if (sops != fast_sops) |
| 2251 | kvfree(sops); |
| 2252 | |
| 2253 | return ret; |
| 2254 | } |
| 2255 | |
| 2256 | long ksys_semtimedop(int semid, struct sembuf __user *tsops, |
| 2257 | unsigned int nsops, const struct __kernel_timespec __user *timeout) |
| 2258 | { |
| 2259 | if (timeout) { |
| 2260 | struct timespec64 ts; |
| 2261 | if (get_timespec64(&ts, timeout)) |
| 2262 | return -EFAULT; |
| 2263 | return do_semtimedop(semid, tsops, nsops, &ts); |
| 2264 | } |
| 2265 | return do_semtimedop(semid, tsops, nsops, NULL); |
| 2266 | } |
| 2267 | |
| 2268 | SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops, |
| 2269 | unsigned int, nsops, const struct __kernel_timespec __user *, timeout) |
| 2270 | { |
| 2271 | return ksys_semtimedop(semid, tsops, nsops, timeout); |
| 2272 | } |
| 2273 | |
| 2274 | #ifdef CONFIG_COMPAT_32BIT_TIME |
| 2275 | long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems, |
| 2276 | unsigned int nsops, |
| 2277 | const struct old_timespec32 __user *timeout) |
| 2278 | { |
| 2279 | if (timeout) { |
| 2280 | struct timespec64 ts; |
| 2281 | if (get_old_timespec32(&ts, timeout)) |
| 2282 | return -EFAULT; |
| 2283 | return do_semtimedop(semid, tsems, nsops, &ts); |
| 2284 | } |
| 2285 | return do_semtimedop(semid, tsems, nsops, NULL); |
| 2286 | } |
| 2287 | |
| 2288 | SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems, |
| 2289 | unsigned int, nsops, |
| 2290 | const struct old_timespec32 __user *, timeout) |
| 2291 | { |
| 2292 | return compat_ksys_semtimedop(semid, tsems, nsops, timeout); |
| 2293 | } |
| 2294 | #endif |
| 2295 | |
| 2296 | SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops, |
| 2297 | unsigned, nsops) |
| 2298 | { |
| 2299 | return do_semtimedop(semid, tsops, nsops, NULL); |
| 2300 | } |
| 2301 | |
| 2302 | /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between |
| 2303 | * parent and child tasks. |
| 2304 | */ |
| 2305 | |
| 2306 | int copy_semundo(unsigned long clone_flags, struct task_struct *tsk) |
| 2307 | { |
| 2308 | struct sem_undo_list *undo_list; |
| 2309 | int error; |
| 2310 | |
| 2311 | if (clone_flags & CLONE_SYSVSEM) { |
| 2312 | error = get_undo_list(&undo_list); |
| 2313 | if (error) |
| 2314 | return error; |
| 2315 | refcount_inc(&undo_list->refcnt); |
| 2316 | tsk->sysvsem.undo_list = undo_list; |
| 2317 | } else |
| 2318 | tsk->sysvsem.undo_list = NULL; |
| 2319 | |
| 2320 | return 0; |
| 2321 | } |
| 2322 | |
| 2323 | /* |
| 2324 | * add semadj values to semaphores, free undo structures. |
| 2325 | * undo structures are not freed when semaphore arrays are destroyed |
| 2326 | * so some of them may be out of date. |
| 2327 | * IMPLEMENTATION NOTE: There is some confusion over whether the |
| 2328 | * set of adjustments that needs to be done should be done in an atomic |
| 2329 | * manner or not. That is, if we are attempting to decrement the semval |
| 2330 | * should we queue up and wait until we can do so legally? |
| 2331 | * The original implementation attempted to do this (queue and wait). |
| 2332 | * The current implementation does not do so. The POSIX standard |
| 2333 | * and SVID should be consulted to determine what behavior is mandated. |
| 2334 | */ |
| 2335 | void exit_sem(struct task_struct *tsk) |
| 2336 | { |
| 2337 | struct sem_undo_list *ulp; |
| 2338 | |
| 2339 | ulp = tsk->sysvsem.undo_list; |
| 2340 | if (!ulp) |
| 2341 | return; |
| 2342 | tsk->sysvsem.undo_list = NULL; |
| 2343 | |
| 2344 | if (!refcount_dec_and_test(&ulp->refcnt)) |
| 2345 | return; |
| 2346 | |
| 2347 | for (;;) { |
| 2348 | struct sem_array *sma; |
| 2349 | struct sem_undo *un; |
| 2350 | int semid, i; |
| 2351 | DEFINE_WAKE_Q(wake_q); |
| 2352 | |
| 2353 | cond_resched(); |
| 2354 | |
| 2355 | rcu_read_lock(); |
| 2356 | un = list_entry_rcu(ulp->list_proc.next, |
| 2357 | struct sem_undo, list_proc); |
| 2358 | if (&un->list_proc == &ulp->list_proc) { |
| 2359 | /* |
| 2360 | * We must wait for freeary() before freeing this ulp, |
| 2361 | * in case we raced with last sem_undo. There is a small |
| 2362 | * possibility where we exit while freeary() didn't |
| 2363 | * finish unlocking sem_undo_list. |
| 2364 | */ |
| 2365 | spin_lock(&ulp->lock); |
| 2366 | spin_unlock(&ulp->lock); |
| 2367 | rcu_read_unlock(); |
| 2368 | break; |
| 2369 | } |
| 2370 | spin_lock(&ulp->lock); |
| 2371 | semid = un->semid; |
| 2372 | spin_unlock(&ulp->lock); |
| 2373 | |
| 2374 | /* exit_sem raced with IPC_RMID, nothing to do */ |
| 2375 | if (semid == -1) { |
| 2376 | rcu_read_unlock(); |
| 2377 | continue; |
| 2378 | } |
| 2379 | |
| 2380 | sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid); |
| 2381 | /* exit_sem raced with IPC_RMID, nothing to do */ |
| 2382 | if (IS_ERR(sma)) { |
| 2383 | rcu_read_unlock(); |
| 2384 | continue; |
| 2385 | } |
| 2386 | |
| 2387 | sem_lock(sma, NULL, -1); |
| 2388 | /* exit_sem raced with IPC_RMID, nothing to do */ |
| 2389 | if (!ipc_valid_object(&sma->sem_perm)) { |
| 2390 | sem_unlock(sma, -1); |
| 2391 | rcu_read_unlock(); |
| 2392 | continue; |
| 2393 | } |
| 2394 | un = __lookup_undo(ulp, semid); |
| 2395 | if (un == NULL) { |
| 2396 | /* exit_sem raced with IPC_RMID+semget() that created |
| 2397 | * exactly the same semid. Nothing to do. |
| 2398 | */ |
| 2399 | sem_unlock(sma, -1); |
| 2400 | rcu_read_unlock(); |
| 2401 | continue; |
| 2402 | } |
| 2403 | |
| 2404 | /* remove un from the linked lists */ |
| 2405 | ipc_assert_locked_object(&sma->sem_perm); |
| 2406 | list_del(&un->list_id); |
| 2407 | |
| 2408 | spin_lock(&ulp->lock); |
| 2409 | list_del_rcu(&un->list_proc); |
| 2410 | spin_unlock(&ulp->lock); |
| 2411 | |
| 2412 | /* perform adjustments registered in un */ |
| 2413 | for (i = 0; i < sma->sem_nsems; i++) { |
| 2414 | struct sem *semaphore = &sma->sems[i]; |
| 2415 | if (un->semadj[i]) { |
| 2416 | semaphore->semval += un->semadj[i]; |
| 2417 | /* |
| 2418 | * Range checks of the new semaphore value, |
| 2419 | * not defined by sus: |
| 2420 | * - Some unices ignore the undo entirely |
| 2421 | * (e.g. HP UX 11i 11.22, Tru64 V5.1) |
| 2422 | * - some cap the value (e.g. FreeBSD caps |
| 2423 | * at 0, but doesn't enforce SEMVMX) |
| 2424 | * |
| 2425 | * Linux caps the semaphore value, both at 0 |
| 2426 | * and at SEMVMX. |
| 2427 | * |
| 2428 | * Manfred <manfred@colorfullife.com> |
| 2429 | */ |
| 2430 | if (semaphore->semval < 0) |
| 2431 | semaphore->semval = 0; |
| 2432 | if (semaphore->semval > SEMVMX) |
| 2433 | semaphore->semval = SEMVMX; |
| 2434 | ipc_update_pid(&semaphore->sempid, task_tgid(current)); |
| 2435 | } |
| 2436 | } |
| 2437 | /* maybe some queued-up processes were waiting for this */ |
| 2438 | do_smart_update(sma, NULL, 0, 1, &wake_q); |
| 2439 | sem_unlock(sma, -1); |
| 2440 | rcu_read_unlock(); |
| 2441 | wake_up_q(&wake_q); |
| 2442 | |
| 2443 | kvfree_rcu(un, rcu); |
| 2444 | } |
| 2445 | kfree(ulp); |
| 2446 | } |
| 2447 | |
| 2448 | #ifdef CONFIG_PROC_FS |
| 2449 | static int sysvipc_sem_proc_show(struct seq_file *s, void *it) |
| 2450 | { |
| 2451 | struct user_namespace *user_ns = seq_user_ns(s); |
| 2452 | struct kern_ipc_perm *ipcp = it; |
| 2453 | struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm); |
| 2454 | time64_t sem_otime; |
| 2455 | |
| 2456 | /* |
| 2457 | * The proc interface isn't aware of sem_lock(), it calls |
| 2458 | * ipc_lock_object(), i.e. spin_lock(&sma->sem_perm.lock). |
| 2459 | * (in sysvipc_find_ipc) |
| 2460 | * In order to stay compatible with sem_lock(), we must |
| 2461 | * enter / leave complex_mode. |
| 2462 | */ |
| 2463 | complexmode_enter(sma); |
| 2464 | |
| 2465 | sem_otime = get_semotime(sma); |
| 2466 | |
| 2467 | seq_printf(s, |
| 2468 | "%10d %10d %4o %10u %5u %5u %5u %5u %10llu %10llu\n", |
| 2469 | sma->sem_perm.key, |
| 2470 | sma->sem_perm.id, |
| 2471 | sma->sem_perm.mode, |
| 2472 | sma->sem_nsems, |
| 2473 | from_kuid_munged(user_ns, sma->sem_perm.uid), |
| 2474 | from_kgid_munged(user_ns, sma->sem_perm.gid), |
| 2475 | from_kuid_munged(user_ns, sma->sem_perm.cuid), |
| 2476 | from_kgid_munged(user_ns, sma->sem_perm.cgid), |
| 2477 | sem_otime, |
| 2478 | sma->sem_ctime); |
| 2479 | |
| 2480 | complexmode_tryleave(sma); |
| 2481 | |
| 2482 | return 0; |
| 2483 | } |
| 2484 | #endif |