linux/ipc/sem.c
<<
>>
Prefs
   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. */
  95struct 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. */
 114struct 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. */
 130struct 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 */
 146struct 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 */
 162struct 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
 171static int newary(struct ipc_namespace *, struct ipc_params *);
 172static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
 173#ifdef CONFIG_PROC_FS
 174static 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 *
 221 * 2) queue.status: (SEM_BARRIER_2)
 222 * Initialization is done while holding sem_lock(), so no further barrier is
 223 * required.
 224 * Setting it to a result code is a RELEASE, this is ensured by both a
 225 * smp_store_release() (for case a) and while holding sem_lock()
 226 * (for case b).
 227 * The ACQUIRE when reading the result code without holding sem_lock() is
 228 * achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep().
 229 * (case a above).
 230 * Reading the result code while holding sem_lock() needs no further barriers,
 231 * the locks inside sem_lock() enforce ordering (case b above)
 232 *
 233 * 3) current->state:
 234 * current->state is set to TASK_INTERRUPTIBLE while holding sem_lock().
 235 * The wakeup is handled using the wake_q infrastructure. wake_q wakeups may
 236 * happen immediately after calling wake_q_add. As wake_q_add_safe() is called
 237 * when holding sem_lock(), no further barriers are required.
 238 *
 239 * See also ipc/mqueue.c for more details on the covered races.
 240 */
 241
 242#define sc_semmsl       sem_ctls[0]
 243#define sc_semmns       sem_ctls[1]
 244#define sc_semopm       sem_ctls[2]
 245#define sc_semmni       sem_ctls[3]
 246
 247void sem_init_ns(struct ipc_namespace *ns)
 248{
 249        ns->sc_semmsl = SEMMSL;
 250        ns->sc_semmns = SEMMNS;
 251        ns->sc_semopm = SEMOPM;
 252        ns->sc_semmni = SEMMNI;
 253        ns->used_sems = 0;
 254        ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
 255}
 256
 257#ifdef CONFIG_IPC_NS
 258void sem_exit_ns(struct ipc_namespace *ns)
 259{
 260        free_ipcs(ns, &sem_ids(ns), freeary);
 261        idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
 262        rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht);
 263}
 264#endif
 265
 266void __init sem_init(void)
 267{
 268        sem_init_ns(&init_ipc_ns);
 269        ipc_init_proc_interface("sysvipc/sem",
 270                                "       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
 271                                IPC_SEM_IDS, sysvipc_sem_proc_show);
 272}
 273
 274/**
 275 * unmerge_queues - unmerge queues, if possible.
 276 * @sma: semaphore array
 277 *
 278 * The function unmerges the wait queues if complex_count is 0.
 279 * It must be called prior to dropping the global semaphore array lock.
 280 */
 281static void unmerge_queues(struct sem_array *sma)
 282{
 283        struct sem_queue *q, *tq;
 284
 285        /* complex operations still around? */
 286        if (sma->complex_count)
 287                return;
 288        /*
 289         * We will switch back to simple mode.
 290         * Move all pending operation back into the per-semaphore
 291         * queues.
 292         */
 293        list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
 294                struct sem *curr;
 295                curr = &sma->sems[q->sops[0].sem_num];
 296
 297                list_add_tail(&q->list, &curr->pending_alter);
 298        }
 299        INIT_LIST_HEAD(&sma->pending_alter);
 300}
 301
 302/**
 303 * merge_queues - merge single semop queues into global queue
 304 * @sma: semaphore array
 305 *
 306 * This function merges all per-semaphore queues into the global queue.
 307 * It is necessary to achieve FIFO ordering for the pending single-sop
 308 * operations when a multi-semop operation must sleep.
 309 * Only the alter operations must be moved, the const operations can stay.
 310 */
 311static void merge_queues(struct sem_array *sma)
 312{
 313        int i;
 314        for (i = 0; i < sma->sem_nsems; i++) {
 315                struct sem *sem = &sma->sems[i];
 316
 317                list_splice_init(&sem->pending_alter, &sma->pending_alter);
 318        }
 319}
 320
 321static void sem_rcu_free(struct rcu_head *head)
 322{
 323        struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
 324        struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
 325
 326        security_sem_free(&sma->sem_perm);
 327        kvfree(sma);
 328}
 329
 330/*
 331 * Enter the mode suitable for non-simple operations:
 332 * Caller must own sem_perm.lock.
 333 */
 334static void complexmode_enter(struct sem_array *sma)
 335{
 336        int i;
 337        struct sem *sem;
 338
 339        if (sma->use_global_lock > 0)  {
 340                /*
 341                 * We are already in global lock mode.
 342                 * Nothing to do, just reset the
 343                 * counter until we return to simple mode.
 344                 */
 345                sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
 346                return;
 347        }
 348        sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
 349
 350        for (i = 0; i < sma->sem_nsems; i++) {
 351                sem = &sma->sems[i];
 352                spin_lock(&sem->lock);
 353                spin_unlock(&sem->lock);
 354        }
 355}
 356
 357/*
 358 * Try to leave the mode that disallows simple operations:
 359 * Caller must own sem_perm.lock.
 360 */
 361static void complexmode_tryleave(struct sem_array *sma)
 362{
 363        if (sma->complex_count)  {
 364                /* Complex ops are sleeping.
 365                 * We must stay in complex mode
 366                 */
 367                return;
 368        }
 369        if (sma->use_global_lock == 1) {
 370
 371                /* See SEM_BARRIER_1 for purpose/pairing */
 372                smp_store_release(&sma->use_global_lock, 0);
 373        } else {
 374                sma->use_global_lock--;
 375        }
 376}
 377
 378#define SEM_GLOBAL_LOCK (-1)
 379/*
 380 * If the request contains only one semaphore operation, and there are
 381 * no complex transactions pending, lock only the semaphore involved.
 382 * Otherwise, lock the entire semaphore array, since we either have
 383 * multiple semaphores in our own semops, or we need to look at
 384 * semaphores from other pending complex operations.
 385 */
 386static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
 387                              int nsops)
 388{
 389        struct sem *sem;
 390        int idx;
 391
 392        if (nsops != 1) {
 393                /* Complex operation - acquire a full lock */
 394                ipc_lock_object(&sma->sem_perm);
 395
 396                /* Prevent parallel simple ops */
 397                complexmode_enter(sma);
 398                return SEM_GLOBAL_LOCK;
 399        }
 400
 401        /*
 402         * Only one semaphore affected - try to optimize locking.
 403         * Optimized locking is possible if no complex operation
 404         * is either enqueued or processed right now.
 405         *
 406         * Both facts are tracked by use_global_mode.
 407         */
 408        idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
 409        sem = &sma->sems[idx];
 410
 411        /*
 412         * Initial check for use_global_lock. Just an optimization,
 413         * no locking, no memory barrier.
 414         */
 415        if (!sma->use_global_lock) {
 416                /*
 417                 * It appears that no complex operation is around.
 418                 * Acquire the per-semaphore lock.
 419                 */
 420                spin_lock(&sem->lock);
 421
 422                /* see SEM_BARRIER_1 for purpose/pairing */
 423                if (!smp_load_acquire(&sma->use_global_lock)) {
 424                        /* fast path successful! */
 425                        return sops->sem_num;
 426                }
 427                spin_unlock(&sem->lock);
 428        }
 429
 430        /* slow path: acquire the full lock */
 431        ipc_lock_object(&sma->sem_perm);
 432
 433        if (sma->use_global_lock == 0) {
 434                /*
 435                 * The use_global_lock mode ended while we waited for
 436                 * sma->sem_perm.lock. Thus we must switch to locking
 437                 * with sem->lock.
 438                 * Unlike in the fast path, there is no need to recheck
 439                 * sma->use_global_lock after we have acquired sem->lock:
 440                 * We own sma->sem_perm.lock, thus use_global_lock cannot
 441                 * change.
 442                 */
 443                spin_lock(&sem->lock);
 444
 445                ipc_unlock_object(&sma->sem_perm);
 446                return sops->sem_num;
 447        } else {
 448                /*
 449                 * Not a false alarm, thus continue to use the global lock
 450                 * mode. No need for complexmode_enter(), this was done by
 451                 * the caller that has set use_global_mode to non-zero.
 452                 */
 453                return SEM_GLOBAL_LOCK;
 454        }
 455}
 456
 457static inline void sem_unlock(struct sem_array *sma, int locknum)
 458{
 459        if (locknum == SEM_GLOBAL_LOCK) {
 460                unmerge_queues(sma);
 461                complexmode_tryleave(sma);
 462                ipc_unlock_object(&sma->sem_perm);
 463        } else {
 464                struct sem *sem = &sma->sems[locknum];
 465                spin_unlock(&sem->lock);
 466        }
 467}
 468
 469/*
 470 * sem_lock_(check_) routines are called in the paths where the rwsem
 471 * is not held.
 472 *
 473 * The caller holds the RCU read lock.
 474 */
 475static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
 476{
 477        struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
 478
 479        if (IS_ERR(ipcp))
 480                return ERR_CAST(ipcp);
 481
 482        return container_of(ipcp, struct sem_array, sem_perm);
 483}
 484
 485static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
 486                                                        int id)
 487{
 488        struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
 489
 490        if (IS_ERR(ipcp))
 491                return ERR_CAST(ipcp);
 492
 493        return container_of(ipcp, struct sem_array, sem_perm);
 494}
 495
 496static inline void sem_lock_and_putref(struct sem_array *sma)
 497{
 498        sem_lock(sma, NULL, -1);
 499        ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 500}
 501
 502static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
 503{
 504        ipc_rmid(&sem_ids(ns), &s->sem_perm);
 505}
 506
 507static struct sem_array *sem_alloc(size_t nsems)
 508{
 509        struct sem_array *sma;
 510
 511        if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
 512                return NULL;
 513
 514        sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL);
 515        if (unlikely(!sma))
 516                return NULL;
 517
 518        return sma;
 519}
 520
 521/**
 522 * newary - Create a new semaphore set
 523 * @ns: namespace
 524 * @params: ptr to the structure that contains key, semflg and nsems
 525 *
 526 * Called with sem_ids.rwsem held (as a writer)
 527 */
 528static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 529{
 530        int retval;
 531        struct sem_array *sma;
 532        key_t key = params->key;
 533        int nsems = params->u.nsems;
 534        int semflg = params->flg;
 535        int i;
 536
 537        if (!nsems)
 538                return -EINVAL;
 539        if (ns->used_sems + nsems > ns->sc_semmns)
 540                return -ENOSPC;
 541
 542        sma = sem_alloc(nsems);
 543        if (!sma)
 544                return -ENOMEM;
 545
 546        sma->sem_perm.mode = (semflg & S_IRWXUGO);
 547        sma->sem_perm.key = key;
 548
 549        sma->sem_perm.security = NULL;
 550        retval = security_sem_alloc(&sma->sem_perm);
 551        if (retval) {
 552                kvfree(sma);
 553                return retval;
 554        }
 555
 556        for (i = 0; i < nsems; i++) {
 557                INIT_LIST_HEAD(&sma->sems[i].pending_alter);
 558                INIT_LIST_HEAD(&sma->sems[i].pending_const);
 559                spin_lock_init(&sma->sems[i].lock);
 560        }
 561
 562        sma->complex_count = 0;
 563        sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
 564        INIT_LIST_HEAD(&sma->pending_alter);
 565        INIT_LIST_HEAD(&sma->pending_const);
 566        INIT_LIST_HEAD(&sma->list_id);
 567        sma->sem_nsems = nsems;
 568        sma->sem_ctime = ktime_get_real_seconds();
 569
 570        /* ipc_addid() locks sma upon success. */
 571        retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
 572        if (retval < 0) {
 573                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 574                return retval;
 575        }
 576        ns->used_sems += nsems;
 577
 578        sem_unlock(sma, -1);
 579        rcu_read_unlock();
 580
 581        return sma->sem_perm.id;
 582}
 583
 584
 585/*
 586 * Called with sem_ids.rwsem and ipcp locked.
 587 */
 588static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params)
 589{
 590        struct sem_array *sma;
 591
 592        sma = container_of(ipcp, struct sem_array, sem_perm);
 593        if (params->u.nsems > sma->sem_nsems)
 594                return -EINVAL;
 595
 596        return 0;
 597}
 598
 599long ksys_semget(key_t key, int nsems, int semflg)
 600{
 601        struct ipc_namespace *ns;
 602        static const struct ipc_ops sem_ops = {
 603                .getnew = newary,
 604                .associate = security_sem_associate,
 605                .more_checks = sem_more_checks,
 606        };
 607        struct ipc_params sem_params;
 608
 609        ns = current->nsproxy->ipc_ns;
 610
 611        if (nsems < 0 || nsems > ns->sc_semmsl)
 612                return -EINVAL;
 613
 614        sem_params.key = key;
 615        sem_params.flg = semflg;
 616        sem_params.u.nsems = nsems;
 617
 618        return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
 619}
 620
 621SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
 622{
 623        return ksys_semget(key, nsems, semflg);
 624}
 625
 626/**
 627 * perform_atomic_semop[_slow] - Attempt to perform semaphore
 628 *                               operations on a given array.
 629 * @sma: semaphore array
 630 * @q: struct sem_queue that describes the operation
 631 *
 632 * Caller blocking are as follows, based the value
 633 * indicated by the semaphore operation (sem_op):
 634 *
 635 *  (1) >0 never blocks.
 636 *  (2)  0 (wait-for-zero operation): semval is non-zero.
 637 *  (3) <0 attempting to decrement semval to a value smaller than zero.
 638 *
 639 * Returns 0 if the operation was possible.
 640 * Returns 1 if the operation is impossible, the caller must sleep.
 641 * Returns <0 for error codes.
 642 */
 643static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
 644{
 645        int result, sem_op, nsops;
 646        struct pid *pid;
 647        struct sembuf *sop;
 648        struct sem *curr;
 649        struct sembuf *sops;
 650        struct sem_undo *un;
 651
 652        sops = q->sops;
 653        nsops = q->nsops;
 654        un = q->undo;
 655
 656        for (sop = sops; sop < sops + nsops; sop++) {
 657                int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
 658                curr = &sma->sems[idx];
 659                sem_op = sop->sem_op;
 660                result = curr->semval;
 661
 662                if (!sem_op && result)
 663                        goto would_block;
 664
 665                result += sem_op;
 666                if (result < 0)
 667                        goto would_block;
 668                if (result > SEMVMX)
 669                        goto out_of_range;
 670
 671                if (sop->sem_flg & SEM_UNDO) {
 672                        int undo = un->semadj[sop->sem_num] - sem_op;
 673                        /* Exceeding the undo range is an error. */
 674                        if (undo < (-SEMAEM - 1) || undo > SEMAEM)
 675                                goto out_of_range;
 676                        un->semadj[sop->sem_num] = undo;
 677                }
 678
 679                curr->semval = result;
 680        }
 681
 682        sop--;
 683        pid = q->pid;
 684        while (sop >= sops) {
 685                ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid);
 686                sop--;
 687        }
 688
 689        return 0;
 690
 691out_of_range:
 692        result = -ERANGE;
 693        goto undo;
 694
 695would_block:
 696        q->blocking = sop;
 697
 698        if (sop->sem_flg & IPC_NOWAIT)
 699                result = -EAGAIN;
 700        else
 701                result = 1;
 702
 703undo:
 704        sop--;
 705        while (sop >= sops) {
 706                sem_op = sop->sem_op;
 707                sma->sems[sop->sem_num].semval -= sem_op;
 708                if (sop->sem_flg & SEM_UNDO)
 709                        un->semadj[sop->sem_num] += sem_op;
 710                sop--;
 711        }
 712
 713        return result;
 714}
 715
 716static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
 717{
 718        int result, sem_op, nsops;
 719        struct sembuf *sop;
 720        struct sem *curr;
 721        struct sembuf *sops;
 722        struct sem_undo *un;
 723
 724        sops = q->sops;
 725        nsops = q->nsops;
 726        un = q->undo;
 727
 728        if (unlikely(q->dupsop))
 729                return perform_atomic_semop_slow(sma, q);
 730
 731        /*
 732         * We scan the semaphore set twice, first to ensure that the entire
 733         * operation can succeed, therefore avoiding any pointless writes
 734         * to shared memory and having to undo such changes in order to block
 735         * until the operations can go through.
 736         */
 737        for (sop = sops; sop < sops + nsops; sop++) {
 738                int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
 739
 740                curr = &sma->sems[idx];
 741                sem_op = sop->sem_op;
 742                result = curr->semval;
 743
 744                if (!sem_op && result)
 745                        goto would_block; /* wait-for-zero */
 746
 747                result += sem_op;
 748                if (result < 0)
 749                        goto would_block;
 750
 751                if (result > SEMVMX)
 752                        return -ERANGE;
 753
 754                if (sop->sem_flg & SEM_UNDO) {
 755                        int undo = un->semadj[sop->sem_num] - sem_op;
 756
 757                        /* Exceeding the undo range is an error. */
 758                        if (undo < (-SEMAEM - 1) || undo > SEMAEM)
 759                                return -ERANGE;
 760                }
 761        }
 762
 763        for (sop = sops; sop < sops + nsops; sop++) {
 764                curr = &sma->sems[sop->sem_num];
 765                sem_op = sop->sem_op;
 766                result = curr->semval;
 767
 768                if (sop->sem_flg & SEM_UNDO) {
 769                        int undo = un->semadj[sop->sem_num] - sem_op;
 770
 771                        un->semadj[sop->sem_num] = undo;
 772                }
 773                curr->semval += sem_op;
 774                ipc_update_pid(&curr->sempid, q->pid);
 775        }
 776
 777        return 0;
 778
 779would_block:
 780        q->blocking = sop;
 781        return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
 782}
 783
 784static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
 785                                             struct wake_q_head *wake_q)
 786{
 787        struct task_struct *sleeper;
 788
 789        sleeper = get_task_struct(q->sleeper);
 790
 791        /* see SEM_BARRIER_2 for purpose/pairing */
 792        smp_store_release(&q->status, error);
 793
 794        wake_q_add_safe(wake_q, sleeper);
 795}
 796
 797static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
 798{
 799        list_del(&q->list);
 800        if (q->nsops > 1)
 801                sma->complex_count--;
 802}
 803
 804/** check_restart(sma, q)
 805 * @sma: semaphore array
 806 * @q: the operation that just completed
 807 *
 808 * update_queue is O(N^2) when it restarts scanning the whole queue of
 809 * waiting operations. Therefore this function checks if the restart is
 810 * really necessary. It is called after a previously waiting operation
 811 * modified the array.
 812 * Note that wait-for-zero operations are handled without restart.
 813 */
 814static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
 815{
 816        /* pending complex alter operations are too difficult to analyse */
 817        if (!list_empty(&sma->pending_alter))
 818                return 1;
 819
 820        /* we were a sleeping complex operation. Too difficult */
 821        if (q->nsops > 1)
 822                return 1;
 823
 824        /* It is impossible that someone waits for the new value:
 825         * - complex operations always restart.
 826         * - wait-for-zero are handled separately.
 827         * - q is a previously sleeping simple operation that
 828         *   altered the array. It must be a decrement, because
 829         *   simple increments never sleep.
 830         * - If there are older (higher priority) decrements
 831         *   in the queue, then they have observed the original
 832         *   semval value and couldn't proceed. The operation
 833         *   decremented to value - thus they won't proceed either.
 834         */
 835        return 0;
 836}
 837
 838/**
 839 * wake_const_ops - wake up non-alter tasks
 840 * @sma: semaphore array.
 841 * @semnum: semaphore that was modified.
 842 * @wake_q: lockless wake-queue head.
 843 *
 844 * wake_const_ops must be called after a semaphore in a semaphore array
 845 * was set to 0. If complex const operations are pending, wake_const_ops must
 846 * be called with semnum = -1, as well as with the number of each modified
 847 * semaphore.
 848 * The tasks that must be woken up are added to @wake_q. The return code
 849 * is stored in q->pid.
 850 * The function returns 1 if at least one operation was completed successfully.
 851 */
 852static int wake_const_ops(struct sem_array *sma, int semnum,
 853                          struct wake_q_head *wake_q)
 854{
 855        struct sem_queue *q, *tmp;
 856        struct list_head *pending_list;
 857        int semop_completed = 0;
 858
 859        if (semnum == -1)
 860                pending_list = &sma->pending_const;
 861        else
 862                pending_list = &sma->sems[semnum].pending_const;
 863
 864        list_for_each_entry_safe(q, tmp, pending_list, list) {
 865                int error = perform_atomic_semop(sma, q);
 866
 867                if (error > 0)
 868                        continue;
 869                /* operation completed, remove from queue & wakeup */
 870                unlink_queue(sma, q);
 871
 872                wake_up_sem_queue_prepare(q, error, wake_q);
 873                if (error == 0)
 874                        semop_completed = 1;
 875        }
 876
 877        return semop_completed;
 878}
 879
 880/**
 881 * do_smart_wakeup_zero - wakeup all wait for zero tasks
 882 * @sma: semaphore array
 883 * @sops: operations that were performed
 884 * @nsops: number of operations
 885 * @wake_q: lockless wake-queue head
 886 *
 887 * Checks all required queue for wait-for-zero operations, based
 888 * on the actual changes that were performed on the semaphore array.
 889 * The function returns 1 if at least one operation was completed successfully.
 890 */
 891static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
 892                                int nsops, struct wake_q_head *wake_q)
 893{
 894        int i;
 895        int semop_completed = 0;
 896        int got_zero = 0;
 897
 898        /* first: the per-semaphore queues, if known */
 899        if (sops) {
 900                for (i = 0; i < nsops; i++) {
 901                        int num = sops[i].sem_num;
 902
 903                        if (sma->sems[num].semval == 0) {
 904                                got_zero = 1;
 905                                semop_completed |= wake_const_ops(sma, num, wake_q);
 906                        }
 907                }
 908        } else {
 909                /*
 910                 * No sops means modified semaphores not known.
 911                 * Assume all were changed.
 912                 */
 913                for (i = 0; i < sma->sem_nsems; i++) {
 914                        if (sma->sems[i].semval == 0) {
 915                                got_zero = 1;
 916                                semop_completed |= wake_const_ops(sma, i, wake_q);
 917                        }
 918                }
 919        }
 920        /*
 921         * If one of the modified semaphores got 0,
 922         * then check the global queue, too.
 923         */
 924        if (got_zero)
 925                semop_completed |= wake_const_ops(sma, -1, wake_q);
 926
 927        return semop_completed;
 928}
 929
 930
 931/**
 932 * update_queue - look for tasks that can be completed.
 933 * @sma: semaphore array.
 934 * @semnum: semaphore that was modified.
 935 * @wake_q: lockless wake-queue head.
 936 *
 937 * update_queue must be called after a semaphore in a semaphore array
 938 * was modified. If multiple semaphores were modified, update_queue must
 939 * be called with semnum = -1, as well as with the number of each modified
 940 * semaphore.
 941 * The tasks that must be woken up are added to @wake_q. The return code
 942 * is stored in q->pid.
 943 * The function internally checks if const operations can now succeed.
 944 *
 945 * The function return 1 if at least one semop was completed successfully.
 946 */
 947static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
 948{
 949        struct sem_queue *q, *tmp;
 950        struct list_head *pending_list;
 951        int semop_completed = 0;
 952
 953        if (semnum == -1)
 954                pending_list = &sma->pending_alter;
 955        else
 956                pending_list = &sma->sems[semnum].pending_alter;
 957
 958again:
 959        list_for_each_entry_safe(q, tmp, pending_list, list) {
 960                int error, restart;
 961
 962                /* If we are scanning the single sop, per-semaphore list of
 963                 * one semaphore and that semaphore is 0, then it is not
 964                 * necessary to scan further: simple increments
 965                 * that affect only one entry succeed immediately and cannot
 966                 * be in the  per semaphore pending queue, and decrements
 967                 * cannot be successful if the value is already 0.
 968                 */
 969                if (semnum != -1 && sma->sems[semnum].semval == 0)
 970                        break;
 971
 972                error = perform_atomic_semop(sma, q);
 973
 974                /* Does q->sleeper still need to sleep? */
 975                if (error > 0)
 976                        continue;
 977
 978                unlink_queue(sma, q);
 979
 980                if (error) {
 981                        restart = 0;
 982                } else {
 983                        semop_completed = 1;
 984                        do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
 985                        restart = check_restart(sma, q);
 986                }
 987
 988                wake_up_sem_queue_prepare(q, error, wake_q);
 989                if (restart)
 990                        goto again;
 991        }
 992        return semop_completed;
 993}
 994
 995/**
 996 * set_semotime - set sem_otime
 997 * @sma: semaphore array
 998 * @sops: operations that modified the array, may be NULL
 999 *
1000 * sem_otime is replicated to avoid cache line trashing.
1001 * This function sets one instance to the current time.
1002 */
1003static void set_semotime(struct sem_array *sma, struct sembuf *sops)
1004{
1005        if (sops == NULL) {
1006                sma->sems[0].sem_otime = ktime_get_real_seconds();
1007        } else {
1008                sma->sems[sops[0].sem_num].sem_otime =
1009                                                ktime_get_real_seconds();
1010        }
1011}
1012
1013/**
1014 * do_smart_update - optimized update_queue
1015 * @sma: semaphore array
1016 * @sops: operations that were performed
1017 * @nsops: number of operations
1018 * @otime: force setting otime
1019 * @wake_q: lockless wake-queue head
1020 *
1021 * do_smart_update() does the required calls to update_queue and wakeup_zero,
1022 * based on the actual changes that were performed on the semaphore array.
1023 * Note that the function does not do the actual wake-up: the caller is
1024 * responsible for calling wake_up_q().
1025 * It is safe to perform this call after dropping all locks.
1026 */
1027static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
1028                            int otime, struct wake_q_head *wake_q)
1029{
1030        int i;
1031
1032        otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
1033
1034        if (!list_empty(&sma->pending_alter)) {
1035                /* semaphore array uses the global queue - just process it. */
1036                otime |= update_queue(sma, -1, wake_q);
1037        } else {
1038                if (!sops) {
1039                        /*
1040                         * No sops, thus the modified semaphores are not
1041                         * known. Check all.
1042                         */
1043                        for (i = 0; i < sma->sem_nsems; i++)
1044                                otime |= update_queue(sma, i, wake_q);
1045                } else {
1046                        /*
1047                         * Check the semaphores that were increased:
1048                         * - No complex ops, thus all sleeping ops are
1049                         *   decrease.
1050                         * - if we decreased the value, then any sleeping
1051                         *   semaphore ops won't be able to run: If the
1052                         *   previous value was too small, then the new
1053                         *   value will be too small, too.
1054                         */
1055                        for (i = 0; i < nsops; i++) {
1056                                if (sops[i].sem_op > 0) {
1057                                        otime |= update_queue(sma,
1058                                                              sops[i].sem_num, wake_q);
1059                                }
1060                        }
1061                }
1062        }
1063        if (otime)
1064                set_semotime(sma, sops);
1065}
1066
1067/*
1068 * check_qop: Test if a queued operation sleeps on the semaphore semnum
1069 */
1070static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1071                        bool count_zero)
1072{
1073        struct sembuf *sop = q->blocking;
1074
1075        /*
1076         * Linux always (since 0.99.10) reported a task as sleeping on all
1077         * semaphores. This violates SUS, therefore it was changed to the
1078         * standard compliant behavior.
1079         * Give the administrators a chance to notice that an application
1080         * might misbehave because it relies on the Linux behavior.
1081         */
1082        pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1083                        "The task %s (%d) triggered the difference, watch for misbehavior.\n",
1084                        current->comm, task_pid_nr(current));
1085
1086        if (sop->sem_num != semnum)
1087                return 0;
1088
1089        if (count_zero && sop->sem_op == 0)
1090                return 1;
1091        if (!count_zero && sop->sem_op < 0)
1092                return 1;
1093
1094        return 0;
1095}
1096
1097/* The following counts are associated to each semaphore:
1098 *   semncnt        number of tasks waiting on semval being nonzero
1099 *   semzcnt        number of tasks waiting on semval being zero
1100 *
1101 * Per definition, a task waits only on the semaphore of the first semop
1102 * that cannot proceed, even if additional operation would block, too.
1103 */
1104static int count_semcnt(struct sem_array *sma, ushort semnum,
1105                        bool count_zero)
1106{
1107        struct list_head *l;
1108        struct sem_queue *q;
1109        int semcnt;
1110
1111        semcnt = 0;
1112        /* First: check the simple operations. They are easy to evaluate */
1113        if (count_zero)
1114                l = &sma->sems[semnum].pending_const;
1115        else
1116                l = &sma->sems[semnum].pending_alter;
1117
1118        list_for_each_entry(q, l, list) {
1119                /* all task on a per-semaphore list sleep on exactly
1120                 * that semaphore
1121                 */
1122                semcnt++;
1123        }
1124
1125        /* Then: check the complex operations. */
1126        list_for_each_entry(q, &sma->pending_alter, list) {
1127                semcnt += check_qop(sma, semnum, q, count_zero);
1128        }
1129        if (count_zero) {
1130                list_for_each_entry(q, &sma->pending_const, list) {
1131                        semcnt += check_qop(sma, semnum, q, count_zero);
1132                }
1133        }
1134        return semcnt;
1135}
1136
1137/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1138 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1139 * remains locked on exit.
1140 */
1141static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1142{
1143        struct sem_undo *un, *tu;
1144        struct sem_queue *q, *tq;
1145        struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1146        int i;
1147        DEFINE_WAKE_Q(wake_q);
1148
1149        /* Free the existing undo structures for this semaphore set.  */
1150        ipc_assert_locked_object(&sma->sem_perm);
1151        list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1152                list_del(&un->list_id);
1153                spin_lock(&un->ulp->lock);
1154                un->semid = -1;
1155                list_del_rcu(&un->list_proc);
1156                spin_unlock(&un->ulp->lock);
1157                kfree_rcu(un, rcu);
1158        }
1159
1160        /* Wake up all pending processes and let them fail with EIDRM. */
1161        list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1162                unlink_queue(sma, q);
1163                wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1164        }
1165
1166        list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1167                unlink_queue(sma, q);
1168                wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1169        }
1170        for (i = 0; i < sma->sem_nsems; i++) {
1171                struct sem *sem = &sma->sems[i];
1172                list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1173                        unlink_queue(sma, q);
1174                        wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1175                }
1176                list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1177                        unlink_queue(sma, q);
1178                        wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1179                }
1180                ipc_update_pid(&sem->sempid, NULL);
1181        }
1182
1183        /* Remove the semaphore set from the IDR */
1184        sem_rmid(ns, sma);
1185        sem_unlock(sma, -1);
1186        rcu_read_unlock();
1187
1188        wake_up_q(&wake_q);
1189        ns->used_sems -= sma->sem_nsems;
1190        ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1191}
1192
1193static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1194{
1195        switch (version) {
1196        case IPC_64:
1197                return copy_to_user(buf, in, sizeof(*in));
1198        case IPC_OLD:
1199            {
1200                struct semid_ds out;
1201
1202                memset(&out, 0, sizeof(out));
1203
1204                ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1205
1206                out.sem_otime   = in->sem_otime;
1207                out.sem_ctime   = in->sem_ctime;
1208                out.sem_nsems   = in->sem_nsems;
1209
1210                return copy_to_user(buf, &out, sizeof(out));
1211            }
1212        default:
1213                return -EINVAL;
1214        }
1215}
1216
1217static time64_t get_semotime(struct sem_array *sma)
1218{
1219        int i;
1220        time64_t res;
1221
1222        res = sma->sems[0].sem_otime;
1223        for (i = 1; i < sma->sem_nsems; i++) {
1224                time64_t to = sma->sems[i].sem_otime;
1225
1226                if (to > res)
1227                        res = to;
1228        }
1229        return res;
1230}
1231
1232static int semctl_stat(struct ipc_namespace *ns, int semid,
1233                         int cmd, struct semid64_ds *semid64)
1234{
1235        struct sem_array *sma;
1236        time64_t semotime;
1237        int err;
1238
1239        memset(semid64, 0, sizeof(*semid64));
1240
1241        rcu_read_lock();
1242        if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) {
1243                sma = sem_obtain_object(ns, semid);
1244                if (IS_ERR(sma)) {
1245                        err = PTR_ERR(sma);
1246                        goto out_unlock;
1247                }
1248        } else { /* IPC_STAT */
1249                sma = sem_obtain_object_check(ns, semid);
1250                if (IS_ERR(sma)) {
1251                        err = PTR_ERR(sma);
1252                        goto out_unlock;
1253                }
1254        }
1255
1256        /* see comment for SHM_STAT_ANY */
1257        if (cmd == SEM_STAT_ANY)
1258                audit_ipc_obj(&sma->sem_perm);
1259        else {
1260                err = -EACCES;
1261                if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1262                        goto out_unlock;
1263        }
1264
1265        err = security_sem_semctl(&sma->sem_perm, cmd);
1266        if (err)
1267                goto out_unlock;
1268
1269        ipc_lock_object(&sma->sem_perm);
1270
1271        if (!ipc_valid_object(&sma->sem_perm)) {
1272                ipc_unlock_object(&sma->sem_perm);
1273                err = -EIDRM;
1274                goto out_unlock;
1275        }
1276
1277        kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
1278        semotime = get_semotime(sma);
1279        semid64->sem_otime = semotime;
1280        semid64->sem_ctime = sma->sem_ctime;
1281#ifndef CONFIG_64BIT
1282        semid64->sem_otime_high = semotime >> 32;
1283        semid64->sem_ctime_high = sma->sem_ctime >> 32;
1284#endif
1285        semid64->sem_nsems = sma->sem_nsems;
1286
1287        if (cmd == IPC_STAT) {
1288                /*
1289                 * As defined in SUS:
1290                 * Return 0 on success
1291                 */
1292                err = 0;
1293        } else {
1294                /*
1295                 * SEM_STAT and SEM_STAT_ANY (both Linux specific)
1296                 * Return the full id, including the sequence number
1297                 */
1298                err = sma->sem_perm.id;
1299        }
1300        ipc_unlock_object(&sma->sem_perm);
1301out_unlock:
1302        rcu_read_unlock();
1303        return err;
1304}
1305
1306static int semctl_info(struct ipc_namespace *ns, int semid,
1307                         int cmd, void __user *p)
1308{
1309        struct seminfo seminfo;
1310        int max_idx;
1311        int err;
1312
1313        err = security_sem_semctl(NULL, cmd);
1314        if (err)
1315                return err;
1316
1317        memset(&seminfo, 0, sizeof(seminfo));
1318        seminfo.semmni = ns->sc_semmni;
1319        seminfo.semmns = ns->sc_semmns;
1320        seminfo.semmsl = ns->sc_semmsl;
1321        seminfo.semopm = ns->sc_semopm;
1322        seminfo.semvmx = SEMVMX;
1323        seminfo.semmnu = SEMMNU;
1324        seminfo.semmap = SEMMAP;
1325        seminfo.semume = SEMUME;
1326        down_read(&sem_ids(ns).rwsem);
1327        if (cmd == SEM_INFO) {
1328                seminfo.semusz = sem_ids(ns).in_use;
1329                seminfo.semaem = ns->used_sems;
1330        } else {
1331                seminfo.semusz = SEMUSZ;
1332                seminfo.semaem = SEMAEM;
1333        }
1334        max_idx = ipc_get_maxidx(&sem_ids(ns));
1335        up_read(&sem_ids(ns).rwsem);
1336        if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1337                return -EFAULT;
1338        return (max_idx < 0) ? 0 : max_idx;
1339}
1340
1341static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1342                int val)
1343{
1344        struct sem_undo *un;
1345        struct sem_array *sma;
1346        struct sem *curr;
1347        int err;
1348        DEFINE_WAKE_Q(wake_q);
1349
1350        if (val > SEMVMX || val < 0)
1351                return -ERANGE;
1352
1353        rcu_read_lock();
1354        sma = sem_obtain_object_check(ns, semid);
1355        if (IS_ERR(sma)) {
1356                rcu_read_unlock();
1357                return PTR_ERR(sma);
1358        }
1359
1360        if (semnum < 0 || semnum >= sma->sem_nsems) {
1361                rcu_read_unlock();
1362                return -EINVAL;
1363        }
1364
1365
1366        if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1367                rcu_read_unlock();
1368                return -EACCES;
1369        }
1370
1371        err = security_sem_semctl(&sma->sem_perm, SETVAL);
1372        if (err) {
1373                rcu_read_unlock();
1374                return -EACCES;
1375        }
1376
1377        sem_lock(sma, NULL, -1);
1378
1379        if (!ipc_valid_object(&sma->sem_perm)) {
1380                sem_unlock(sma, -1);
1381                rcu_read_unlock();
1382                return -EIDRM;
1383        }
1384
1385        semnum = array_index_nospec(semnum, sma->sem_nsems);
1386        curr = &sma->sems[semnum];
1387
1388        ipc_assert_locked_object(&sma->sem_perm);
1389        list_for_each_entry(un, &sma->list_id, list_id)
1390                un->semadj[semnum] = 0;
1391
1392        curr->semval = val;
1393        ipc_update_pid(&curr->sempid, task_tgid(current));
1394        sma->sem_ctime = ktime_get_real_seconds();
1395        /* maybe some queued-up processes were waiting for this */
1396        do_smart_update(sma, NULL, 0, 0, &wake_q);
1397        sem_unlock(sma, -1);
1398        rcu_read_unlock();
1399        wake_up_q(&wake_q);
1400        return 0;
1401}
1402
1403static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1404                int cmd, void __user *p)
1405{
1406        struct sem_array *sma;
1407        struct sem *curr;
1408        int err, nsems;
1409        ushort fast_sem_io[SEMMSL_FAST];
1410        ushort *sem_io = fast_sem_io;
1411        DEFINE_WAKE_Q(wake_q);
1412
1413        rcu_read_lock();
1414        sma = sem_obtain_object_check(ns, semid);
1415        if (IS_ERR(sma)) {
1416                rcu_read_unlock();
1417                return PTR_ERR(sma);
1418        }
1419
1420        nsems = sma->sem_nsems;
1421
1422        err = -EACCES;
1423        if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1424                goto out_rcu_wakeup;
1425
1426        err = security_sem_semctl(&sma->sem_perm, cmd);
1427        if (err)
1428                goto out_rcu_wakeup;
1429
1430        err = -EACCES;
1431        switch (cmd) {
1432        case GETALL:
1433        {
1434                ushort __user *array = p;
1435                int i;
1436
1437                sem_lock(sma, NULL, -1);
1438                if (!ipc_valid_object(&sma->sem_perm)) {
1439                        err = -EIDRM;
1440                        goto out_unlock;
1441                }
1442                if (nsems > SEMMSL_FAST) {
1443                        if (!ipc_rcu_getref(&sma->sem_perm)) {
1444                                err = -EIDRM;
1445                                goto out_unlock;
1446                        }
1447                        sem_unlock(sma, -1);
1448                        rcu_read_unlock();
1449                        sem_io = kvmalloc_array(nsems, sizeof(ushort),
1450                                                GFP_KERNEL);
1451                        if (sem_io == NULL) {
1452                                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1453                                return -ENOMEM;
1454                        }
1455
1456                        rcu_read_lock();
1457                        sem_lock_and_putref(sma);
1458                        if (!ipc_valid_object(&sma->sem_perm)) {
1459                                err = -EIDRM;
1460                                goto out_unlock;
1461                        }
1462                }
1463                for (i = 0; i < sma->sem_nsems; i++)
1464                        sem_io[i] = sma->sems[i].semval;
1465                sem_unlock(sma, -1);
1466                rcu_read_unlock();
1467                err = 0;
1468                if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1469                        err = -EFAULT;
1470                goto out_free;
1471        }
1472        case SETALL:
1473        {
1474                int i;
1475                struct sem_undo *un;
1476
1477                if (!ipc_rcu_getref(&sma->sem_perm)) {
1478                        err = -EIDRM;
1479                        goto out_rcu_wakeup;
1480                }
1481                rcu_read_unlock();
1482
1483                if (nsems > SEMMSL_FAST) {
1484                        sem_io = kvmalloc_array(nsems, sizeof(ushort),
1485                                                GFP_KERNEL);
1486                        if (sem_io == NULL) {
1487                                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1488                                return -ENOMEM;
1489                        }
1490                }
1491
1492                if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1493                        ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1494                        err = -EFAULT;
1495                        goto out_free;
1496                }
1497
1498                for (i = 0; i < nsems; i++) {
1499                        if (sem_io[i] > SEMVMX) {
1500                                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1501                                err = -ERANGE;
1502                                goto out_free;
1503                        }
1504                }
1505                rcu_read_lock();
1506                sem_lock_and_putref(sma);
1507                if (!ipc_valid_object(&sma->sem_perm)) {
1508                        err = -EIDRM;
1509                        goto out_unlock;
1510                }
1511
1512                for (i = 0; i < nsems; i++) {
1513                        sma->sems[i].semval = sem_io[i];
1514                        ipc_update_pid(&sma->sems[i].sempid, task_tgid(current));
1515                }
1516
1517                ipc_assert_locked_object(&sma->sem_perm);
1518                list_for_each_entry(un, &sma->list_id, list_id) {
1519                        for (i = 0; i < nsems; i++)
1520                                un->semadj[i] = 0;
1521                }
1522                sma->sem_ctime = ktime_get_real_seconds();
1523                /* maybe some queued-up processes were waiting for this */
1524                do_smart_update(sma, NULL, 0, 0, &wake_q);
1525                err = 0;
1526                goto out_unlock;
1527        }
1528        /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1529        }
1530        err = -EINVAL;
1531        if (semnum < 0 || semnum >= nsems)
1532                goto out_rcu_wakeup;
1533
1534        sem_lock(sma, NULL, -1);
1535        if (!ipc_valid_object(&sma->sem_perm)) {
1536                err = -EIDRM;
1537                goto out_unlock;
1538        }
1539
1540        semnum = array_index_nospec(semnum, nsems);
1541        curr = &sma->sems[semnum];
1542
1543        switch (cmd) {
1544        case GETVAL:
1545                err = curr->semval;
1546                goto out_unlock;
1547        case GETPID:
1548                err = pid_vnr(curr->sempid);
1549                goto out_unlock;
1550        case GETNCNT:
1551                err = count_semcnt(sma, semnum, 0);
1552                goto out_unlock;
1553        case GETZCNT:
1554                err = count_semcnt(sma, semnum, 1);
1555                goto out_unlock;
1556        }
1557
1558out_unlock:
1559        sem_unlock(sma, -1);
1560out_rcu_wakeup:
1561        rcu_read_unlock();
1562        wake_up_q(&wake_q);
1563out_free:
1564        if (sem_io != fast_sem_io)
1565                kvfree(sem_io);
1566        return err;
1567}
1568
1569static inline unsigned long
1570copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1571{
1572        switch (version) {
1573        case IPC_64:
1574                if (copy_from_user(out, buf, sizeof(*out)))
1575                        return -EFAULT;
1576                return 0;
1577        case IPC_OLD:
1578            {
1579                struct semid_ds tbuf_old;
1580
1581                if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1582                        return -EFAULT;
1583
1584                out->sem_perm.uid       = tbuf_old.sem_perm.uid;
1585                out->sem_perm.gid       = tbuf_old.sem_perm.gid;
1586                out->sem_perm.mode      = tbuf_old.sem_perm.mode;
1587
1588                return 0;
1589            }
1590        default:
1591                return -EINVAL;
1592        }
1593}
1594
1595/*
1596 * This function handles some semctl commands which require the rwsem
1597 * to be held in write mode.
1598 * NOTE: no locks must be held, the rwsem is taken inside this function.
1599 */
1600static int semctl_down(struct ipc_namespace *ns, int semid,
1601                       int cmd, struct semid64_ds *semid64)
1602{
1603        struct sem_array *sma;
1604        int err;
1605        struct kern_ipc_perm *ipcp;
1606
1607        down_write(&sem_ids(ns).rwsem);
1608        rcu_read_lock();
1609
1610        ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
1611                                      &semid64->sem_perm, 0);
1612        if (IS_ERR(ipcp)) {
1613                err = PTR_ERR(ipcp);
1614                goto out_unlock1;
1615        }
1616
1617        sma = container_of(ipcp, struct sem_array, sem_perm);
1618
1619        err = security_sem_semctl(&sma->sem_perm, cmd);
1620        if (err)
1621                goto out_unlock1;
1622
1623        switch (cmd) {
1624        case IPC_RMID:
1625                sem_lock(sma, NULL, -1);
1626                /* freeary unlocks the ipc object and rcu */
1627                freeary(ns, ipcp);
1628                goto out_up;
1629        case IPC_SET:
1630                sem_lock(sma, NULL, -1);
1631                err = ipc_update_perm(&semid64->sem_perm, ipcp);
1632                if (err)
1633                        goto out_unlock0;
1634                sma->sem_ctime = ktime_get_real_seconds();
1635                break;
1636        default:
1637                err = -EINVAL;
1638                goto out_unlock1;
1639        }
1640
1641out_unlock0:
1642        sem_unlock(sma, -1);
1643out_unlock1:
1644        rcu_read_unlock();
1645out_up:
1646        up_write(&sem_ids(ns).rwsem);
1647        return err;
1648}
1649
1650static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version)
1651{
1652        struct ipc_namespace *ns;
1653        void __user *p = (void __user *)arg;
1654        struct semid64_ds semid64;
1655        int err;
1656
1657        if (semid < 0)
1658                return -EINVAL;
1659
1660        ns = current->nsproxy->ipc_ns;
1661
1662        switch (cmd) {
1663        case IPC_INFO:
1664        case SEM_INFO:
1665                return semctl_info(ns, semid, cmd, p);
1666        case IPC_STAT:
1667        case SEM_STAT:
1668        case SEM_STAT_ANY:
1669                err = semctl_stat(ns, semid, cmd, &semid64);
1670                if (err < 0)
1671                        return err;
1672                if (copy_semid_to_user(p, &semid64, version))
1673                        err = -EFAULT;
1674                return err;
1675        case GETALL:
1676        case GETVAL:
1677        case GETPID:
1678        case GETNCNT:
1679        case GETZCNT:
1680        case SETALL:
1681                return semctl_main(ns, semid, semnum, cmd, p);
1682        case SETVAL: {
1683                int val;
1684#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1685                /* big-endian 64bit */
1686                val = arg >> 32;
1687#else
1688                /* 32bit or little-endian 64bit */
1689                val = arg;
1690#endif
1691                return semctl_setval(ns, semid, semnum, val);
1692        }
1693        case IPC_SET:
1694                if (copy_semid_from_user(&semid64, p, version))
1695                        return -EFAULT;
1696                fallthrough;
1697        case IPC_RMID:
1698                return semctl_down(ns, semid, cmd, &semid64);
1699        default:
1700                return -EINVAL;
1701        }
1702}
1703
1704SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1705{
1706        return ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1707}
1708
1709#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
1710long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg)
1711{
1712        int version = ipc_parse_version(&cmd);
1713
1714        return ksys_semctl(semid, semnum, cmd, arg, version);
1715}
1716
1717SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1718{
1719        return ksys_old_semctl(semid, semnum, cmd, arg);
1720}
1721#endif
1722
1723#ifdef CONFIG_COMPAT
1724
1725struct compat_semid_ds {
1726        struct compat_ipc_perm sem_perm;
1727        old_time32_t sem_otime;
1728        old_time32_t sem_ctime;
1729        compat_uptr_t sem_base;
1730        compat_uptr_t sem_pending;
1731        compat_uptr_t sem_pending_last;
1732        compat_uptr_t undo;
1733        unsigned short sem_nsems;
1734};
1735
1736static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf,
1737                                        int version)
1738{
1739        memset(out, 0, sizeof(*out));
1740        if (version == IPC_64) {
1741                struct compat_semid64_ds __user *p = buf;
1742                return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm);
1743        } else {
1744                struct compat_semid_ds __user *p = buf;
1745                return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm);
1746        }
1747}
1748
1749static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in,
1750                                        int version)
1751{
1752        if (version == IPC_64) {
1753                struct compat_semid64_ds v;
1754                memset(&v, 0, sizeof(v));
1755                to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm);
1756                v.sem_otime      = lower_32_bits(in->sem_otime);
1757                v.sem_otime_high = upper_32_bits(in->sem_otime);
1758                v.sem_ctime      = lower_32_bits(in->sem_ctime);
1759                v.sem_ctime_high = upper_32_bits(in->sem_ctime);
1760                v.sem_nsems = in->sem_nsems;
1761                return copy_to_user(buf, &v, sizeof(v));
1762        } else {
1763                struct compat_semid_ds v;
1764                memset(&v, 0, sizeof(v));
1765                to_compat_ipc_perm(&v.sem_perm, &in->sem_perm);
1766                v.sem_otime = in->sem_otime;
1767                v.sem_ctime = in->sem_ctime;
1768                v.sem_nsems = in->sem_nsems;
1769                return copy_to_user(buf, &v, sizeof(v));
1770        }
1771}
1772
1773static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version)
1774{
1775        void __user *p = compat_ptr(arg);
1776        struct ipc_namespace *ns;
1777        struct semid64_ds semid64;
1778        int err;
1779
1780        ns = current->nsproxy->ipc_ns;
1781
1782        if (semid < 0)
1783                return -EINVAL;
1784
1785        switch (cmd & (~IPC_64)) {
1786        case IPC_INFO:
1787        case SEM_INFO:
1788                return semctl_info(ns, semid, cmd, p);
1789        case IPC_STAT:
1790        case SEM_STAT:
1791        case SEM_STAT_ANY:
1792                err = semctl_stat(ns, semid, cmd, &semid64);
1793                if (err < 0)
1794                        return err;
1795                if (copy_compat_semid_to_user(p, &semid64, version))
1796                        err = -EFAULT;
1797                return err;
1798        case GETVAL:
1799        case GETPID:
1800        case GETNCNT:
1801        case GETZCNT:
1802        case GETALL:
1803        case SETALL:
1804                return semctl_main(ns, semid, semnum, cmd, p);
1805        case SETVAL:
1806                return semctl_setval(ns, semid, semnum, arg);
1807        case IPC_SET:
1808                if (copy_compat_semid_from_user(&semid64, p, version))
1809                        return -EFAULT;
1810                fallthrough;
1811        case IPC_RMID:
1812                return semctl_down(ns, semid, cmd, &semid64);
1813        default:
1814                return -EINVAL;
1815        }
1816}
1817
1818COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
1819{
1820        return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1821}
1822
1823#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
1824long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg)
1825{
1826        int version = compat_ipc_parse_version(&cmd);
1827
1828        return compat_ksys_semctl(semid, semnum, cmd, arg, version);
1829}
1830
1831COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg)
1832{
1833        return compat_ksys_old_semctl(semid, semnum, cmd, arg);
1834}
1835#endif
1836#endif
1837
1838/* If the task doesn't already have a undo_list, then allocate one
1839 * here.  We guarantee there is only one thread using this undo list,
1840 * and current is THE ONE
1841 *
1842 * If this allocation and assignment succeeds, but later
1843 * portions of this code fail, there is no need to free the sem_undo_list.
1844 * Just let it stay associated with the task, and it'll be freed later
1845 * at exit time.
1846 *
1847 * This can block, so callers must hold no locks.
1848 */
1849static inline int get_undo_list(struct sem_undo_list **undo_listp)
1850{
1851        struct sem_undo_list *undo_list;
1852
1853        undo_list = current->sysvsem.undo_list;
1854        if (!undo_list) {
1855                undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
1856                if (undo_list == NULL)
1857                        return -ENOMEM;
1858                spin_lock_init(&undo_list->lock);
1859                refcount_set(&undo_list->refcnt, 1);
1860                INIT_LIST_HEAD(&undo_list->list_proc);
1861
1862                current->sysvsem.undo_list = undo_list;
1863        }
1864        *undo_listp = undo_list;
1865        return 0;
1866}
1867
1868static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1869{
1870        struct sem_undo *un;
1871
1872        list_for_each_entry_rcu(un, &ulp->list_proc, list_proc,
1873                                spin_is_locked(&ulp->lock)) {
1874                if (un->semid == semid)
1875                        return un;
1876        }
1877        return NULL;
1878}
1879
1880static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1881{
1882        struct sem_undo *un;
1883
1884        assert_spin_locked(&ulp->lock);
1885
1886        un = __lookup_undo(ulp, semid);
1887        if (un) {
1888                list_del_rcu(&un->list_proc);
1889                list_add_rcu(&un->list_proc, &ulp->list_proc);
1890        }
1891        return un;
1892}
1893
1894/**
1895 * find_alloc_undo - lookup (and if not present create) undo array
1896 * @ns: namespace
1897 * @semid: semaphore array id
1898 *
1899 * The function looks up (and if not present creates) the undo structure.
1900 * The size of the undo structure depends on the size of the semaphore
1901 * array, thus the alloc path is not that straightforward.
1902 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1903 * performs a rcu_read_lock().
1904 */
1905static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1906{
1907        struct sem_array *sma;
1908        struct sem_undo_list *ulp;
1909        struct sem_undo *un, *new;
1910        int nsems, error;
1911
1912        error = get_undo_list(&ulp);
1913        if (error)
1914                return ERR_PTR(error);
1915
1916        rcu_read_lock();
1917        spin_lock(&ulp->lock);
1918        un = lookup_undo(ulp, semid);
1919        spin_unlock(&ulp->lock);
1920        if (likely(un != NULL))
1921                goto out;
1922
1923        /* no undo structure around - allocate one. */
1924        /* step 1: figure out the size of the semaphore array */
1925        sma = sem_obtain_object_check(ns, semid);
1926        if (IS_ERR(sma)) {
1927                rcu_read_unlock();
1928                return ERR_CAST(sma);
1929        }
1930
1931        nsems = sma->sem_nsems;
1932        if (!ipc_rcu_getref(&sma->sem_perm)) {
1933                rcu_read_unlock();
1934                un = ERR_PTR(-EIDRM);
1935                goto out;
1936        }
1937        rcu_read_unlock();
1938
1939        /* step 2: allocate new undo structure */
1940        new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
1941        if (!new) {
1942                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1943                return ERR_PTR(-ENOMEM);
1944        }
1945
1946        /* step 3: Acquire the lock on semaphore array */
1947        rcu_read_lock();
1948        sem_lock_and_putref(sma);
1949        if (!ipc_valid_object(&sma->sem_perm)) {
1950                sem_unlock(sma, -1);
1951                rcu_read_unlock();
1952                kfree(new);
1953                un = ERR_PTR(-EIDRM);
1954                goto out;
1955        }
1956        spin_lock(&ulp->lock);
1957
1958        /*
1959         * step 4: check for races: did someone else allocate the undo struct?
1960         */
1961        un = lookup_undo(ulp, semid);
1962        if (un) {
1963                kfree(new);
1964                goto success;
1965        }
1966        /* step 5: initialize & link new undo structure */
1967        new->semadj = (short *) &new[1];
1968        new->ulp = ulp;
1969        new->semid = semid;
1970        assert_spin_locked(&ulp->lock);
1971        list_add_rcu(&new->list_proc, &ulp->list_proc);
1972        ipc_assert_locked_object(&sma->sem_perm);
1973        list_add(&new->list_id, &sma->list_id);
1974        un = new;
1975
1976success:
1977        spin_unlock(&ulp->lock);
1978        sem_unlock(sma, -1);
1979out:
1980        return un;
1981}
1982
1983static long do_semtimedop(int semid, struct sembuf __user *tsops,
1984                unsigned nsops, const struct timespec64 *timeout)
1985{
1986        int error = -EINVAL;
1987        struct sem_array *sma;
1988        struct sembuf fast_sops[SEMOPM_FAST];
1989        struct sembuf *sops = fast_sops, *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, jiffies_left = 0;
1995        struct ipc_namespace *ns;
1996
1997        ns = current->nsproxy->ipc_ns;
1998
1999        if (nsops < 1 || semid < 0)
2000                return -EINVAL;
2001        if (nsops > ns->sc_semopm)
2002                return -E2BIG;
2003        if (nsops > SEMOPM_FAST) {
2004                sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
2005                if (sops == NULL)
2006                        return -ENOMEM;
2007        }
2008
2009        if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
2010                error =  -EFAULT;
2011                goto out_free;
2012        }
2013
2014        if (timeout) {
2015                if (timeout->tv_sec < 0 || timeout->tv_nsec < 0 ||
2016                        timeout->tv_nsec >= 1000000000L) {
2017                        error = -EINVAL;
2018                        goto out_free;
2019                }
2020                jiffies_left = timespec64_to_jiffies(timeout);
2021        }
2022
2023        max = 0;
2024        for (sop = sops; sop < sops + nsops; sop++) {
2025                unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
2026
2027                if (sop->sem_num >= max)
2028                        max = sop->sem_num;
2029                if (sop->sem_flg & SEM_UNDO)
2030                        undos = true;
2031                if (dup & mask) {
2032                        /*
2033                         * There was a previous alter access that appears
2034                         * to have accessed the same semaphore, thus use
2035                         * the dupsop logic. "appears", because the detection
2036                         * can only check % BITS_PER_LONG.
2037                         */
2038                        dupsop = true;
2039                }
2040                if (sop->sem_op != 0) {
2041                        alter = true;
2042                        dup |= mask;
2043                }
2044        }
2045
2046        if (undos) {
2047                /* On success, find_alloc_undo takes the rcu_read_lock */
2048                un = find_alloc_undo(ns, semid);
2049                if (IS_ERR(un)) {
2050                        error = PTR_ERR(un);
2051                        goto out_free;
2052                }
2053        } else {
2054                un = NULL;
2055                rcu_read_lock();
2056        }
2057
2058        sma = sem_obtain_object_check(ns, semid);
2059        if (IS_ERR(sma)) {
2060                rcu_read_unlock();
2061                error = PTR_ERR(sma);
2062                goto out_free;
2063        }
2064
2065        error = -EFBIG;
2066        if (max >= sma->sem_nsems) {
2067                rcu_read_unlock();
2068                goto out_free;
2069        }
2070
2071        error = -EACCES;
2072        if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
2073                rcu_read_unlock();
2074                goto out_free;
2075        }
2076
2077        error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
2078        if (error) {
2079                rcu_read_unlock();
2080                goto out_free;
2081        }
2082
2083        error = -EIDRM;
2084        locknum = sem_lock(sma, sops, nsops);
2085        /*
2086         * We eventually might perform the following check in a lockless
2087         * fashion, considering ipc_valid_object() locking constraints.
2088         * If nsops == 1 and there is no contention for sem_perm.lock, then
2089         * only a per-semaphore lock is held and it's OK to proceed with the
2090         * check below. More details on the fine grained locking scheme
2091         * entangled here and why it's RMID race safe on comments at sem_lock()
2092         */
2093        if (!ipc_valid_object(&sma->sem_perm))
2094                goto out_unlock_free;
2095        /*
2096         * semid identifiers are not unique - find_alloc_undo may have
2097         * allocated an undo structure, it was invalidated by an RMID
2098         * and now a new array with received the same id. Check and fail.
2099         * This case can be detected checking un->semid. The existence of
2100         * "un" itself is guaranteed by rcu.
2101         */
2102        if (un && un->semid == -1)
2103                goto out_unlock_free;
2104
2105        queue.sops = sops;
2106        queue.nsops = nsops;
2107        queue.undo = un;
2108        queue.pid = task_tgid(current);
2109        queue.alter = alter;
2110        queue.dupsop = dupsop;
2111
2112        error = perform_atomic_semop(sma, &queue);
2113        if (error == 0) { /* non-blocking successful path */
2114                DEFINE_WAKE_Q(wake_q);
2115
2116                /*
2117                 * If the operation was successful, then do
2118                 * the required updates.
2119                 */
2120                if (alter)
2121                        do_smart_update(sma, sops, nsops, 1, &wake_q);
2122                else
2123                        set_semotime(sma, sops);
2124
2125                sem_unlock(sma, locknum);
2126                rcu_read_unlock();
2127                wake_up_q(&wake_q);
2128
2129                goto out_free;
2130        }
2131        if (error < 0) /* non-blocking error path */
2132                goto out_unlock_free;
2133
2134        /*
2135         * We need to sleep on this operation, so we put the current
2136         * task into the pending queue and go to sleep.
2137         */
2138        if (nsops == 1) {
2139                struct sem *curr;
2140                int idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
2141                curr = &sma->sems[idx];
2142
2143                if (alter) {
2144                        if (sma->complex_count) {
2145                                list_add_tail(&queue.list,
2146                                                &sma->pending_alter);
2147                        } else {
2148
2149                                list_add_tail(&queue.list,
2150                                                &curr->pending_alter);
2151                        }
2152                } else {
2153                        list_add_tail(&queue.list, &curr->pending_const);
2154                }
2155        } else {
2156                if (!sma->complex_count)
2157                        merge_queues(sma);
2158
2159                if (alter)
2160                        list_add_tail(&queue.list, &sma->pending_alter);
2161                else
2162                        list_add_tail(&queue.list, &sma->pending_const);
2163
2164                sma->complex_count++;
2165        }
2166
2167        do {
2168                /* memory ordering ensured by the lock in sem_lock() */
2169                WRITE_ONCE(queue.status, -EINTR);
2170                queue.sleeper = current;
2171
2172                /* memory ordering is ensured by the lock in sem_lock() */
2173                __set_current_state(TASK_INTERRUPTIBLE);
2174                sem_unlock(sma, locknum);
2175                rcu_read_unlock();
2176
2177                if (timeout)
2178                        jiffies_left = schedule_timeout(jiffies_left);
2179                else
2180                        schedule();
2181
2182                /*
2183                 * fastpath: the semop has completed, either successfully or
2184                 * not, from the syscall pov, is quite irrelevant to us at this
2185                 * point; we're done.
2186                 *
2187                 * We _do_ care, nonetheless, about being awoken by a signal or
2188                 * spuriously.  The queue.status is checked again in the
2189                 * slowpath (aka after taking sem_lock), such that we can detect
2190                 * scenarios where we were awakened externally, during the
2191                 * window between wake_q_add() and wake_up_q().
2192                 */
2193                error = READ_ONCE(queue.status);
2194                if (error != -EINTR) {
2195                        /* see SEM_BARRIER_2 for purpose/pairing */
2196                        smp_acquire__after_ctrl_dep();
2197                        goto out_free;
2198                }
2199
2200                rcu_read_lock();
2201                locknum = sem_lock(sma, sops, nsops);
2202
2203                if (!ipc_valid_object(&sma->sem_perm))
2204                        goto out_unlock_free;
2205
2206                /*
2207                 * No necessity for any barrier: We are protect by sem_lock()
2208                 */
2209                error = READ_ONCE(queue.status);
2210
2211                /*
2212                 * If queue.status != -EINTR we are woken up by another process.
2213                 * Leave without unlink_queue(), but with sem_unlock().
2214                 */
2215                if (error != -EINTR)
2216                        goto out_unlock_free;
2217
2218                /*
2219                 * If an interrupt occurred we have to clean up the queue.
2220                 */
2221                if (timeout && jiffies_left == 0)
2222                        error = -EAGAIN;
2223        } while (error == -EINTR && !signal_pending(current)); /* spurious */
2224
2225        unlink_queue(sma, &queue);
2226
2227out_unlock_free:
2228        sem_unlock(sma, locknum);
2229        rcu_read_unlock();
2230out_free:
2231        if (sops != fast_sops)
2232                kvfree(sops);
2233        return error;
2234}
2235
2236long ksys_semtimedop(int semid, struct sembuf __user *tsops,
2237                     unsigned int nsops, const struct __kernel_timespec __user *timeout)
2238{
2239        if (timeout) {
2240                struct timespec64 ts;
2241                if (get_timespec64(&ts, timeout))
2242                        return -EFAULT;
2243                return do_semtimedop(semid, tsops, nsops, &ts);
2244        }
2245        return do_semtimedop(semid, tsops, nsops, NULL);
2246}
2247
2248SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
2249                unsigned int, nsops, const struct __kernel_timespec __user *, timeout)
2250{
2251        return ksys_semtimedop(semid, tsops, nsops, timeout);
2252}
2253
2254#ifdef CONFIG_COMPAT_32BIT_TIME
2255long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
2256                            unsigned int nsops,
2257                            const struct old_timespec32 __user *timeout)
2258{
2259        if (timeout) {
2260                struct timespec64 ts;
2261                if (get_old_timespec32(&ts, timeout))
2262                        return -EFAULT;
2263                return do_semtimedop(semid, tsems, nsops, &ts);
2264        }
2265        return do_semtimedop(semid, tsems, nsops, NULL);
2266}
2267
2268SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems,
2269                       unsigned int, nsops,
2270                       const struct old_timespec32 __user *, timeout)
2271{
2272        return compat_ksys_semtimedop(semid, tsems, nsops, timeout);
2273}
2274#endif
2275
2276SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2277                unsigned, nsops)
2278{
2279        return do_semtimedop(semid, tsops, nsops, NULL);
2280}
2281
2282/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2283 * parent and child tasks.
2284 */
2285
2286int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2287{
2288        struct sem_undo_list *undo_list;
2289        int error;
2290
2291        if (clone_flags & CLONE_SYSVSEM) {
2292                error = get_undo_list(&undo_list);
2293                if (error)
2294                        return error;
2295                refcount_inc(&undo_list->refcnt);
2296                tsk->sysvsem.undo_list = undo_list;
2297        } else
2298                tsk->sysvsem.undo_list = NULL;
2299
2300        return 0;
2301}
2302
2303/*
2304 * add semadj values to semaphores, free undo structures.
2305 * undo structures are not freed when semaphore arrays are destroyed
2306 * so some of them may be out of date.
2307 * IMPLEMENTATION NOTE: There is some confusion over whether the
2308 * set of adjustments that needs to be done should be done in an atomic
2309 * manner or not. That is, if we are attempting to decrement the semval
2310 * should we queue up and wait until we can do so legally?
2311 * The original implementation attempted to do this (queue and wait).
2312 * The current implementation does not do so. The POSIX standard
2313 * and SVID should be consulted to determine what behavior is mandated.
2314 */
2315void exit_sem(struct task_struct *tsk)
2316{
2317        struct sem_undo_list *ulp;
2318
2319        ulp = tsk->sysvsem.undo_list;
2320        if (!ulp)
2321                return;
2322        tsk->sysvsem.undo_list = NULL;
2323
2324        if (!refcount_dec_and_test(&ulp->refcnt))
2325                return;
2326
2327        for (;;) {
2328                struct sem_array *sma;
2329                struct sem_undo *un;
2330                int semid, i;
2331                DEFINE_WAKE_Q(wake_q);
2332
2333                cond_resched();
2334
2335                rcu_read_lock();
2336                un = list_entry_rcu(ulp->list_proc.next,
2337                                    struct sem_undo, list_proc);
2338                if (&un->list_proc == &ulp->list_proc) {
2339                        /*
2340                         * We must wait for freeary() before freeing this ulp,
2341                         * in case we raced with last sem_undo. There is a small
2342                         * possibility where we exit while freeary() didn't
2343                         * finish unlocking sem_undo_list.
2344                         */
2345                        spin_lock(&ulp->lock);
2346                        spin_unlock(&ulp->lock);
2347                        rcu_read_unlock();
2348                        break;
2349                }
2350                spin_lock(&ulp->lock);
2351                semid = un->semid;
2352                spin_unlock(&ulp->lock);
2353
2354                /* exit_sem raced with IPC_RMID, nothing to do */
2355                if (semid == -1) {
2356                        rcu_read_unlock();
2357                        continue;
2358                }
2359
2360                sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2361                /* exit_sem raced with IPC_RMID, nothing to do */
2362                if (IS_ERR(sma)) {
2363                        rcu_read_unlock();
2364                        continue;
2365                }
2366
2367                sem_lock(sma, NULL, -1);
2368                /* exit_sem raced with IPC_RMID, nothing to do */
2369                if (!ipc_valid_object(&sma->sem_perm)) {
2370                        sem_unlock(sma, -1);
2371                        rcu_read_unlock();
2372                        continue;
2373                }
2374                un = __lookup_undo(ulp, semid);
2375                if (un == NULL) {
2376                        /* exit_sem raced with IPC_RMID+semget() that created
2377                         * exactly the same semid. Nothing to do.
2378                         */
2379                        sem_unlock(sma, -1);
2380                        rcu_read_unlock();
2381                        continue;
2382                }
2383
2384                /* remove un from the linked lists */
2385                ipc_assert_locked_object(&sma->sem_perm);
2386                list_del(&un->list_id);
2387
2388                spin_lock(&ulp->lock);
2389                list_del_rcu(&un->list_proc);
2390                spin_unlock(&ulp->lock);
2391
2392                /* perform adjustments registered in un */
2393                for (i = 0; i < sma->sem_nsems; i++) {
2394                        struct sem *semaphore = &sma->sems[i];
2395                        if (un->semadj[i]) {
2396                                semaphore->semval += un->semadj[i];
2397                                /*
2398                                 * Range checks of the new semaphore value,
2399                                 * not defined by sus:
2400                                 * - Some unices ignore the undo entirely
2401                                 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2402                                 * - some cap the value (e.g. FreeBSD caps
2403                                 *   at 0, but doesn't enforce SEMVMX)
2404                                 *
2405                                 * Linux caps the semaphore value, both at 0
2406                                 * and at SEMVMX.
2407                                 *
2408                                 *      Manfred <manfred@colorfullife.com>
2409                                 */
2410                                if (semaphore->semval < 0)
2411                                        semaphore->semval = 0;
2412                                if (semaphore->semval > SEMVMX)
2413                                        semaphore->semval = SEMVMX;
2414                                ipc_update_pid(&semaphore->sempid, task_tgid(current));
2415                        }
2416                }
2417                /* maybe some queued-up processes were waiting for this */
2418                do_smart_update(sma, NULL, 0, 1, &wake_q);
2419                sem_unlock(sma, -1);
2420                rcu_read_unlock();
2421                wake_up_q(&wake_q);
2422
2423                kfree_rcu(un, rcu);
2424        }
2425        kfree(ulp);
2426}
2427
2428#ifdef CONFIG_PROC_FS
2429static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2430{
2431        struct user_namespace *user_ns = seq_user_ns(s);
2432        struct kern_ipc_perm *ipcp = it;
2433        struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
2434        time64_t sem_otime;
2435
2436        /*
2437         * The proc interface isn't aware of sem_lock(), it calls
2438         * ipc_lock_object() directly (in sysvipc_find_ipc).
2439         * In order to stay compatible with sem_lock(), we must
2440         * enter / leave complex_mode.
2441         */
2442        complexmode_enter(sma);
2443
2444        sem_otime = get_semotime(sma);
2445
2446        seq_printf(s,
2447                   "%10d %10d  %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
2448                   sma->sem_perm.key,
2449                   sma->sem_perm.id,
2450                   sma->sem_perm.mode,
2451                   sma->sem_nsems,
2452                   from_kuid_munged(user_ns, sma->sem_perm.uid),
2453                   from_kgid_munged(user_ns, sma->sem_perm.gid),
2454                   from_kuid_munged(user_ns, sma->sem_perm.cuid),
2455                   from_kgid_munged(user_ns, sma->sem_perm.cgid),
2456                   sem_otime,
2457                   sma->sem_ctime);
2458
2459        complexmode_tryleave(sma);
2460
2461        return 0;
2462}
2463#endif
2464