linux/ipc/sem.c
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   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 * To prevent the compiler/cpu temporarily writing 0 to use_global_lock,
 221 * READ_ONCE()/WRITE_ONCE() is used.
 222 *
 223 * 2) queue.status: (SEM_BARRIER_2)
 224 * Initialization is done while holding sem_lock(), so no further barrier is
 225 * required.
 226 * Setting it to a result code is a RELEASE, this is ensured by both a
 227 * smp_store_release() (for case a) and while holding sem_lock()
 228 * (for case b).
 229 * The ACQUIRE when reading the result code without holding sem_lock() is
 230 * achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep().
 231 * (case a above).
 232 * Reading the result code while holding sem_lock() needs no further barriers,
 233 * the locks inside sem_lock() enforce ordering (case b above)
 234 *
 235 * 3) current->state:
 236 * current->state is set to TASK_INTERRUPTIBLE while holding sem_lock().
 237 * The wakeup is handled using the wake_q infrastructure. wake_q wakeups may
 238 * happen immediately after calling wake_q_add. As wake_q_add_safe() is called
 239 * when holding sem_lock(), no further barriers are required.
 240 *
 241 * See also ipc/mqueue.c for more details on the covered races.
 242 */
 243
 244#define sc_semmsl       sem_ctls[0]
 245#define sc_semmns       sem_ctls[1]
 246#define sc_semopm       sem_ctls[2]
 247#define sc_semmni       sem_ctls[3]
 248
 249void sem_init_ns(struct ipc_namespace *ns)
 250{
 251        ns->sc_semmsl = SEMMSL;
 252        ns->sc_semmns = SEMMNS;
 253        ns->sc_semopm = SEMOPM;
 254        ns->sc_semmni = SEMMNI;
 255        ns->used_sems = 0;
 256        ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
 257}
 258
 259#ifdef CONFIG_IPC_NS
 260void sem_exit_ns(struct ipc_namespace *ns)
 261{
 262        free_ipcs(ns, &sem_ids(ns), freeary);
 263        idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
 264        rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht);
 265}
 266#endif
 267
 268void __init sem_init(void)
 269{
 270        sem_init_ns(&init_ipc_ns);
 271        ipc_init_proc_interface("sysvipc/sem",
 272                                "       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
 273                                IPC_SEM_IDS, sysvipc_sem_proc_show);
 274}
 275
 276/**
 277 * unmerge_queues - unmerge queues, if possible.
 278 * @sma: semaphore array
 279 *
 280 * The function unmerges the wait queues if complex_count is 0.
 281 * It must be called prior to dropping the global semaphore array lock.
 282 */
 283static void unmerge_queues(struct sem_array *sma)
 284{
 285        struct sem_queue *q, *tq;
 286
 287        /* complex operations still around? */
 288        if (sma->complex_count)
 289                return;
 290        /*
 291         * We will switch back to simple mode.
 292         * Move all pending operation back into the per-semaphore
 293         * queues.
 294         */
 295        list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
 296                struct sem *curr;
 297                curr = &sma->sems[q->sops[0].sem_num];
 298
 299                list_add_tail(&q->list, &curr->pending_alter);
 300        }
 301        INIT_LIST_HEAD(&sma->pending_alter);
 302}
 303
 304/**
 305 * merge_queues - merge single semop queues into global queue
 306 * @sma: semaphore array
 307 *
 308 * This function merges all per-semaphore queues into the global queue.
 309 * It is necessary to achieve FIFO ordering for the pending single-sop
 310 * operations when a multi-semop operation must sleep.
 311 * Only the alter operations must be moved, the const operations can stay.
 312 */
 313static void merge_queues(struct sem_array *sma)
 314{
 315        int i;
 316        for (i = 0; i < sma->sem_nsems; i++) {
 317                struct sem *sem = &sma->sems[i];
 318
 319                list_splice_init(&sem->pending_alter, &sma->pending_alter);
 320        }
 321}
 322
 323static void sem_rcu_free(struct rcu_head *head)
 324{
 325        struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
 326        struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
 327
 328        security_sem_free(&sma->sem_perm);
 329        kvfree(sma);
 330}
 331
 332/*
 333 * Enter the mode suitable for non-simple operations:
 334 * Caller must own sem_perm.lock.
 335 */
 336static void complexmode_enter(struct sem_array *sma)
 337{
 338        int i;
 339        struct sem *sem;
 340
 341        if (sma->use_global_lock > 0)  {
 342                /*
 343                 * We are already in global lock mode.
 344                 * Nothing to do, just reset the
 345                 * counter until we return to simple mode.
 346                 */
 347                WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS);
 348                return;
 349        }
 350        WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS);
 351
 352        for (i = 0; i < sma->sem_nsems; i++) {
 353                sem = &sma->sems[i];
 354                spin_lock(&sem->lock);
 355                spin_unlock(&sem->lock);
 356        }
 357}
 358
 359/*
 360 * Try to leave the mode that disallows simple operations:
 361 * Caller must own sem_perm.lock.
 362 */
 363static void complexmode_tryleave(struct sem_array *sma)
 364{
 365        if (sma->complex_count)  {
 366                /* Complex ops are sleeping.
 367                 * We must stay in complex mode
 368                 */
 369                return;
 370        }
 371        if (sma->use_global_lock == 1) {
 372
 373                /* See SEM_BARRIER_1 for purpose/pairing */
 374                smp_store_release(&sma->use_global_lock, 0);
 375        } else {
 376                WRITE_ONCE(sma->use_global_lock,
 377                                sma->use_global_lock-1);
 378        }
 379}
 380
 381#define SEM_GLOBAL_LOCK (-1)
 382/*
 383 * If the request contains only one semaphore operation, and there are
 384 * no complex transactions pending, lock only the semaphore involved.
 385 * Otherwise, lock the entire semaphore array, since we either have
 386 * multiple semaphores in our own semops, or we need to look at
 387 * semaphores from other pending complex operations.
 388 */
 389static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
 390                              int nsops)
 391{
 392        struct sem *sem;
 393        int idx;
 394
 395        if (nsops != 1) {
 396                /* Complex operation - acquire a full lock */
 397                ipc_lock_object(&sma->sem_perm);
 398
 399                /* Prevent parallel simple ops */
 400                complexmode_enter(sma);
 401                return SEM_GLOBAL_LOCK;
 402        }
 403
 404        /*
 405         * Only one semaphore affected - try to optimize locking.
 406         * Optimized locking is possible if no complex operation
 407         * is either enqueued or processed right now.
 408         *
 409         * Both facts are tracked by use_global_mode.
 410         */
 411        idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
 412        sem = &sma->sems[idx];
 413
 414        /*
 415         * Initial check for use_global_lock. Just an optimization,
 416         * no locking, no memory barrier.
 417         */
 418        if (!READ_ONCE(sma->use_global_lock)) {
 419                /*
 420                 * It appears that no complex operation is around.
 421                 * Acquire the per-semaphore lock.
 422                 */
 423                spin_lock(&sem->lock);
 424
 425                /* see SEM_BARRIER_1 for purpose/pairing */
 426                if (!smp_load_acquire(&sma->use_global_lock)) {
 427                        /* fast path successful! */
 428                        return sops->sem_num;
 429                }
 430                spin_unlock(&sem->lock);
 431        }
 432
 433        /* slow path: acquire the full lock */
 434        ipc_lock_object(&sma->sem_perm);
 435
 436        if (sma->use_global_lock == 0) {
 437                /*
 438                 * The use_global_lock mode ended while we waited for
 439                 * sma->sem_perm.lock. Thus we must switch to locking
 440                 * with sem->lock.
 441                 * Unlike in the fast path, there is no need to recheck
 442                 * sma->use_global_lock after we have acquired sem->lock:
 443                 * We own sma->sem_perm.lock, thus use_global_lock cannot
 444                 * change.
 445                 */
 446                spin_lock(&sem->lock);
 447
 448                ipc_unlock_object(&sma->sem_perm);
 449                return sops->sem_num;
 450        } else {
 451                /*
 452                 * Not a false alarm, thus continue to use the global lock
 453                 * mode. No need for complexmode_enter(), this was done by
 454                 * the caller that has set use_global_mode to non-zero.
 455                 */
 456                return SEM_GLOBAL_LOCK;
 457        }
 458}
 459
 460static inline void sem_unlock(struct sem_array *sma, int locknum)
 461{
 462        if (locknum == SEM_GLOBAL_LOCK) {
 463                unmerge_queues(sma);
 464                complexmode_tryleave(sma);
 465                ipc_unlock_object(&sma->sem_perm);
 466        } else {
 467                struct sem *sem = &sma->sems[locknum];
 468                spin_unlock(&sem->lock);
 469        }
 470}
 471
 472/*
 473 * sem_lock_(check_) routines are called in the paths where the rwsem
 474 * is not held.
 475 *
 476 * The caller holds the RCU read lock.
 477 */
 478static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
 479{
 480        struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
 481
 482        if (IS_ERR(ipcp))
 483                return ERR_CAST(ipcp);
 484
 485        return container_of(ipcp, struct sem_array, sem_perm);
 486}
 487
 488static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
 489                                                        int id)
 490{
 491        struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
 492
 493        if (IS_ERR(ipcp))
 494                return ERR_CAST(ipcp);
 495
 496        return container_of(ipcp, struct sem_array, sem_perm);
 497}
 498
 499static inline void sem_lock_and_putref(struct sem_array *sma)
 500{
 501        sem_lock(sma, NULL, -1);
 502        ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 503}
 504
 505static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
 506{
 507        ipc_rmid(&sem_ids(ns), &s->sem_perm);
 508}
 509
 510static struct sem_array *sem_alloc(size_t nsems)
 511{
 512        struct sem_array *sma;
 513
 514        if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
 515                return NULL;
 516
 517        sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL_ACCOUNT);
 518        if (unlikely(!sma))
 519                return NULL;
 520
 521        return sma;
 522}
 523
 524/**
 525 * newary - Create a new semaphore set
 526 * @ns: namespace
 527 * @params: ptr to the structure that contains key, semflg and nsems
 528 *
 529 * Called with sem_ids.rwsem held (as a writer)
 530 */
 531static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 532{
 533        int retval;
 534        struct sem_array *sma;
 535        key_t key = params->key;
 536        int nsems = params->u.nsems;
 537        int semflg = params->flg;
 538        int i;
 539
 540        if (!nsems)
 541                return -EINVAL;
 542        if (ns->used_sems + nsems > ns->sc_semmns)
 543                return -ENOSPC;
 544
 545        sma = sem_alloc(nsems);
 546        if (!sma)
 547                return -ENOMEM;
 548
 549        sma->sem_perm.mode = (semflg & S_IRWXUGO);
 550        sma->sem_perm.key = key;
 551
 552        sma->sem_perm.security = NULL;
 553        retval = security_sem_alloc(&sma->sem_perm);
 554        if (retval) {
 555                kvfree(sma);
 556                return retval;
 557        }
 558
 559        for (i = 0; i < nsems; i++) {
 560                INIT_LIST_HEAD(&sma->sems[i].pending_alter);
 561                INIT_LIST_HEAD(&sma->sems[i].pending_const);
 562                spin_lock_init(&sma->sems[i].lock);
 563        }
 564
 565        sma->complex_count = 0;
 566        sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
 567        INIT_LIST_HEAD(&sma->pending_alter);
 568        INIT_LIST_HEAD(&sma->pending_const);
 569        INIT_LIST_HEAD(&sma->list_id);
 570        sma->sem_nsems = nsems;
 571        sma->sem_ctime = ktime_get_real_seconds();
 572
 573        /* ipc_addid() locks sma upon success. */
 574        retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
 575        if (retval < 0) {
 576                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 577                return retval;
 578        }
 579        ns->used_sems += nsems;
 580
 581        sem_unlock(sma, -1);
 582        rcu_read_unlock();
 583
 584        return sma->sem_perm.id;
 585}
 586
 587
 588/*
 589 * Called with sem_ids.rwsem and ipcp locked.
 590 */
 591static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params)
 592{
 593        struct sem_array *sma;
 594
 595        sma = container_of(ipcp, struct sem_array, sem_perm);
 596        if (params->u.nsems > sma->sem_nsems)
 597                return -EINVAL;
 598
 599        return 0;
 600}
 601
 602long ksys_semget(key_t key, int nsems, int semflg)
 603{
 604        struct ipc_namespace *ns;
 605        static const struct ipc_ops sem_ops = {
 606                .getnew = newary,
 607                .associate = security_sem_associate,
 608                .more_checks = sem_more_checks,
 609        };
 610        struct ipc_params sem_params;
 611
 612        ns = current->nsproxy->ipc_ns;
 613
 614        if (nsems < 0 || nsems > ns->sc_semmsl)
 615                return -EINVAL;
 616
 617        sem_params.key = key;
 618        sem_params.flg = semflg;
 619        sem_params.u.nsems = nsems;
 620
 621        return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
 622}
 623
 624SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
 625{
 626        return ksys_semget(key, nsems, semflg);
 627}
 628
 629/**
 630 * perform_atomic_semop[_slow] - Attempt to perform semaphore
 631 *                               operations on a given array.
 632 * @sma: semaphore array
 633 * @q: struct sem_queue that describes the operation
 634 *
 635 * Caller blocking are as follows, based the value
 636 * indicated by the semaphore operation (sem_op):
 637 *
 638 *  (1) >0 never blocks.
 639 *  (2)  0 (wait-for-zero operation): semval is non-zero.
 640 *  (3) <0 attempting to decrement semval to a value smaller than zero.
 641 *
 642 * Returns 0 if the operation was possible.
 643 * Returns 1 if the operation is impossible, the caller must sleep.
 644 * Returns <0 for error codes.
 645 */
 646static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
 647{
 648        int result, sem_op, nsops;
 649        struct pid *pid;
 650        struct sembuf *sop;
 651        struct sem *curr;
 652        struct sembuf *sops;
 653        struct sem_undo *un;
 654
 655        sops = q->sops;
 656        nsops = q->nsops;
 657        un = q->undo;
 658
 659        for (sop = sops; sop < sops + nsops; sop++) {
 660                int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
 661                curr = &sma->sems[idx];
 662                sem_op = sop->sem_op;
 663                result = curr->semval;
 664
 665                if (!sem_op && result)
 666                        goto would_block;
 667
 668                result += sem_op;
 669                if (result < 0)
 670                        goto would_block;
 671                if (result > SEMVMX)
 672                        goto out_of_range;
 673
 674                if (sop->sem_flg & SEM_UNDO) {
 675                        int undo = un->semadj[sop->sem_num] - sem_op;
 676                        /* Exceeding the undo range is an error. */
 677                        if (undo < (-SEMAEM - 1) || undo > SEMAEM)
 678                                goto out_of_range;
 679                        un->semadj[sop->sem_num] = undo;
 680                }
 681
 682                curr->semval = result;
 683        }
 684
 685        sop--;
 686        pid = q->pid;
 687        while (sop >= sops) {
 688                ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid);
 689                sop--;
 690        }
 691
 692        return 0;
 693
 694out_of_range:
 695        result = -ERANGE;
 696        goto undo;
 697
 698would_block:
 699        q->blocking = sop;
 700
 701        if (sop->sem_flg & IPC_NOWAIT)
 702                result = -EAGAIN;
 703        else
 704                result = 1;
 705
 706undo:
 707        sop--;
 708        while (sop >= sops) {
 709                sem_op = sop->sem_op;
 710                sma->sems[sop->sem_num].semval -= sem_op;
 711                if (sop->sem_flg & SEM_UNDO)
 712                        un->semadj[sop->sem_num] += sem_op;
 713                sop--;
 714        }
 715
 716        return result;
 717}
 718
 719static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
 720{
 721        int result, sem_op, nsops;
 722        struct sembuf *sop;
 723        struct sem *curr;
 724        struct sembuf *sops;
 725        struct sem_undo *un;
 726
 727        sops = q->sops;
 728        nsops = q->nsops;
 729        un = q->undo;
 730
 731        if (unlikely(q->dupsop))
 732                return perform_atomic_semop_slow(sma, q);
 733
 734        /*
 735         * We scan the semaphore set twice, first to ensure that the entire
 736         * operation can succeed, therefore avoiding any pointless writes
 737         * to shared memory and having to undo such changes in order to block
 738         * until the operations can go through.
 739         */
 740        for (sop = sops; sop < sops + nsops; sop++) {
 741                int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
 742
 743                curr = &sma->sems[idx];
 744                sem_op = sop->sem_op;
 745                result = curr->semval;
 746
 747                if (!sem_op && result)
 748                        goto would_block; /* wait-for-zero */
 749
 750                result += sem_op;
 751                if (result < 0)
 752                        goto would_block;
 753
 754                if (result > SEMVMX)
 755                        return -ERANGE;
 756
 757                if (sop->sem_flg & SEM_UNDO) {
 758                        int undo = un->semadj[sop->sem_num] - sem_op;
 759
 760                        /* Exceeding the undo range is an error. */
 761                        if (undo < (-SEMAEM - 1) || undo > SEMAEM)
 762                                return -ERANGE;
 763                }
 764        }
 765
 766        for (sop = sops; sop < sops + nsops; sop++) {
 767                curr = &sma->sems[sop->sem_num];
 768                sem_op = sop->sem_op;
 769
 770                if (sop->sem_flg & SEM_UNDO) {
 771                        int undo = un->semadj[sop->sem_num] - sem_op;
 772
 773                        un->semadj[sop->sem_num] = undo;
 774                }
 775                curr->semval += sem_op;
 776                ipc_update_pid(&curr->sempid, q->pid);
 777        }
 778
 779        return 0;
 780
 781would_block:
 782        q->blocking = sop;
 783        return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
 784}
 785
 786static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
 787                                             struct wake_q_head *wake_q)
 788{
 789        struct task_struct *sleeper;
 790
 791        sleeper = get_task_struct(q->sleeper);
 792
 793        /* see SEM_BARRIER_2 for purpose/pairing */
 794        smp_store_release(&q->status, error);
 795
 796        wake_q_add_safe(wake_q, sleeper);
 797}
 798
 799static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
 800{
 801        list_del(&q->list);
 802        if (q->nsops > 1)
 803                sma->complex_count--;
 804}
 805
 806/** check_restart(sma, q)
 807 * @sma: semaphore array
 808 * @q: the operation that just completed
 809 *
 810 * update_queue is O(N^2) when it restarts scanning the whole queue of
 811 * waiting operations. Therefore this function checks if the restart is
 812 * really necessary. It is called after a previously waiting operation
 813 * modified the array.
 814 * Note that wait-for-zero operations are handled without restart.
 815 */
 816static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
 817{
 818        /* pending complex alter operations are too difficult to analyse */
 819        if (!list_empty(&sma->pending_alter))
 820                return 1;
 821
 822        /* we were a sleeping complex operation. Too difficult */
 823        if (q->nsops > 1)
 824                return 1;
 825
 826        /* It is impossible that someone waits for the new value:
 827         * - complex operations always restart.
 828         * - wait-for-zero are handled separately.
 829         * - q is a previously sleeping simple operation that
 830         *   altered the array. It must be a decrement, because
 831         *   simple increments never sleep.
 832         * - If there are older (higher priority) decrements
 833         *   in the queue, then they have observed the original
 834         *   semval value and couldn't proceed. The operation
 835         *   decremented to value - thus they won't proceed either.
 836         */
 837        return 0;
 838}
 839
 840/**
 841 * wake_const_ops - wake up non-alter tasks
 842 * @sma: semaphore array.
 843 * @semnum: semaphore that was modified.
 844 * @wake_q: lockless wake-queue head.
 845 *
 846 * wake_const_ops must be called after a semaphore in a semaphore array
 847 * was set to 0. If complex const operations are pending, wake_const_ops must
 848 * be called with semnum = -1, as well as with the number of each modified
 849 * semaphore.
 850 * The tasks that must be woken up are added to @wake_q. The return code
 851 * is stored in q->pid.
 852 * The function returns 1 if at least one operation was completed successfully.
 853 */
 854static int wake_const_ops(struct sem_array *sma, int semnum,
 855                          struct wake_q_head *wake_q)
 856{
 857        struct sem_queue *q, *tmp;
 858        struct list_head *pending_list;
 859        int semop_completed = 0;
 860
 861        if (semnum == -1)
 862                pending_list = &sma->pending_const;
 863        else
 864                pending_list = &sma->sems[semnum].pending_const;
 865
 866        list_for_each_entry_safe(q, tmp, pending_list, list) {
 867                int error = perform_atomic_semop(sma, q);
 868
 869                if (error > 0)
 870                        continue;
 871                /* operation completed, remove from queue & wakeup */
 872                unlink_queue(sma, q);
 873
 874                wake_up_sem_queue_prepare(q, error, wake_q);
 875                if (error == 0)
 876                        semop_completed = 1;
 877        }
 878
 879        return semop_completed;
 880}
 881
 882/**
 883 * do_smart_wakeup_zero - wakeup all wait for zero tasks
 884 * @sma: semaphore array
 885 * @sops: operations that were performed
 886 * @nsops: number of operations
 887 * @wake_q: lockless wake-queue head
 888 *
 889 * Checks all required queue for wait-for-zero operations, based
 890 * on the actual changes that were performed on the semaphore array.
 891 * The function returns 1 if at least one operation was completed successfully.
 892 */
 893static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
 894                                int nsops, struct wake_q_head *wake_q)
 895{
 896        int i;
 897        int semop_completed = 0;
 898        int got_zero = 0;
 899
 900        /* first: the per-semaphore queues, if known */
 901        if (sops) {
 902                for (i = 0; i < nsops; i++) {
 903                        int num = sops[i].sem_num;
 904
 905                        if (sma->sems[num].semval == 0) {
 906                                got_zero = 1;
 907                                semop_completed |= wake_const_ops(sma, num, wake_q);
 908                        }
 909                }
 910        } else {
 911                /*
 912                 * No sops means modified semaphores not known.
 913                 * Assume all were changed.
 914                 */
 915                for (i = 0; i < sma->sem_nsems; i++) {
 916                        if (sma->sems[i].semval == 0) {
 917                                got_zero = 1;
 918                                semop_completed |= wake_const_ops(sma, i, wake_q);
 919                        }
 920                }
 921        }
 922        /*
 923         * If one of the modified semaphores got 0,
 924         * then check the global queue, too.
 925         */
 926        if (got_zero)
 927                semop_completed |= wake_const_ops(sma, -1, wake_q);
 928
 929        return semop_completed;
 930}
 931
 932
 933/**
 934 * update_queue - look for tasks that can be completed.
 935 * @sma: semaphore array.
 936 * @semnum: semaphore that was modified.
 937 * @wake_q: lockless wake-queue head.
 938 *
 939 * update_queue must be called after a semaphore in a semaphore array
 940 * was modified. If multiple semaphores were modified, update_queue must
 941 * be called with semnum = -1, as well as with the number of each modified
 942 * semaphore.
 943 * The tasks that must be woken up are added to @wake_q. The return code
 944 * is stored in q->pid.
 945 * The function internally checks if const operations can now succeed.
 946 *
 947 * The function return 1 if at least one semop was completed successfully.
 948 */
 949static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
 950{
 951        struct sem_queue *q, *tmp;
 952        struct list_head *pending_list;
 953        int semop_completed = 0;
 954
 955        if (semnum == -1)
 956                pending_list = &sma->pending_alter;
 957        else
 958                pending_list = &sma->sems[semnum].pending_alter;
 959
 960again:
 961        list_for_each_entry_safe(q, tmp, pending_list, list) {
 962                int error, restart;
 963
 964                /* If we are scanning the single sop, per-semaphore list of
 965                 * one semaphore and that semaphore is 0, then it is not
 966                 * necessary to scan further: simple increments
 967                 * that affect only one entry succeed immediately and cannot
 968                 * be in the  per semaphore pending queue, and decrements
 969                 * cannot be successful if the value is already 0.
 970                 */
 971                if (semnum != -1 && sma->sems[semnum].semval == 0)
 972                        break;
 973
 974                error = perform_atomic_semop(sma, q);
 975
 976                /* Does q->sleeper still need to sleep? */
 977                if (error > 0)
 978                        continue;
 979
 980                unlink_queue(sma, q);
 981
 982                if (error) {
 983                        restart = 0;
 984                } else {
 985                        semop_completed = 1;
 986                        do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
 987                        restart = check_restart(sma, q);
 988                }
 989
 990                wake_up_sem_queue_prepare(q, error, wake_q);
 991                if (restart)
 992                        goto again;
 993        }
 994        return semop_completed;
 995}
 996
 997/**
 998 * set_semotime - set sem_otime
 999 * @sma: semaphore array
1000 * @sops: operations that modified the array, may be NULL
1001 *
1002 * sem_otime is replicated to avoid cache line trashing.
1003 * This function sets one instance to the current time.
1004 */
1005static void set_semotime(struct sem_array *sma, struct sembuf *sops)
1006{
1007        if (sops == NULL) {
1008                sma->sems[0].sem_otime = ktime_get_real_seconds();
1009        } else {
1010                sma->sems[sops[0].sem_num].sem_otime =
1011                                                ktime_get_real_seconds();
1012        }
1013}
1014
1015/**
1016 * do_smart_update - optimized update_queue
1017 * @sma: semaphore array
1018 * @sops: operations that were performed
1019 * @nsops: number of operations
1020 * @otime: force setting otime
1021 * @wake_q: lockless wake-queue head
1022 *
1023 * do_smart_update() does the required calls to update_queue and wakeup_zero,
1024 * based on the actual changes that were performed on the semaphore array.
1025 * Note that the function does not do the actual wake-up: the caller is
1026 * responsible for calling wake_up_q().
1027 * It is safe to perform this call after dropping all locks.
1028 */
1029static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
1030                            int otime, struct wake_q_head *wake_q)
1031{
1032        int i;
1033
1034        otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
1035
1036        if (!list_empty(&sma->pending_alter)) {
1037                /* semaphore array uses the global queue - just process it. */
1038                otime |= update_queue(sma, -1, wake_q);
1039        } else {
1040                if (!sops) {
1041                        /*
1042                         * No sops, thus the modified semaphores are not
1043                         * known. Check all.
1044                         */
1045                        for (i = 0; i < sma->sem_nsems; i++)
1046                                otime |= update_queue(sma, i, wake_q);
1047                } else {
1048                        /*
1049                         * Check the semaphores that were increased:
1050                         * - No complex ops, thus all sleeping ops are
1051                         *   decrease.
1052                         * - if we decreased the value, then any sleeping
1053                         *   semaphore ops won't be able to run: If the
1054                         *   previous value was too small, then the new
1055                         *   value will be too small, too.
1056                         */
1057                        for (i = 0; i < nsops; i++) {
1058                                if (sops[i].sem_op > 0) {
1059                                        otime |= update_queue(sma,
1060                                                              sops[i].sem_num, wake_q);
1061                                }
1062                        }
1063                }
1064        }
1065        if (otime)
1066                set_semotime(sma, sops);
1067}
1068
1069/*
1070 * check_qop: Test if a queued operation sleeps on the semaphore semnum
1071 */
1072static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
1073                        bool count_zero)
1074{
1075        struct sembuf *sop = q->blocking;
1076
1077        /*
1078         * Linux always (since 0.99.10) reported a task as sleeping on all
1079         * semaphores. This violates SUS, therefore it was changed to the
1080         * standard compliant behavior.
1081         * Give the administrators a chance to notice that an application
1082         * might misbehave because it relies on the Linux behavior.
1083         */
1084        pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
1085                        "The task %s (%d) triggered the difference, watch for misbehavior.\n",
1086                        current->comm, task_pid_nr(current));
1087
1088        if (sop->sem_num != semnum)
1089                return 0;
1090
1091        if (count_zero && sop->sem_op == 0)
1092                return 1;
1093        if (!count_zero && sop->sem_op < 0)
1094                return 1;
1095
1096        return 0;
1097}
1098
1099/* The following counts are associated to each semaphore:
1100 *   semncnt        number of tasks waiting on semval being nonzero
1101 *   semzcnt        number of tasks waiting on semval being zero
1102 *
1103 * Per definition, a task waits only on the semaphore of the first semop
1104 * that cannot proceed, even if additional operation would block, too.
1105 */
1106static int count_semcnt(struct sem_array *sma, ushort semnum,
1107                        bool count_zero)
1108{
1109        struct list_head *l;
1110        struct sem_queue *q;
1111        int semcnt;
1112
1113        semcnt = 0;
1114        /* First: check the simple operations. They are easy to evaluate */
1115        if (count_zero)
1116                l = &sma->sems[semnum].pending_const;
1117        else
1118                l = &sma->sems[semnum].pending_alter;
1119
1120        list_for_each_entry(q, l, list) {
1121                /* all task on a per-semaphore list sleep on exactly
1122                 * that semaphore
1123                 */
1124                semcnt++;
1125        }
1126
1127        /* Then: check the complex operations. */
1128        list_for_each_entry(q, &sma->pending_alter, list) {
1129                semcnt += check_qop(sma, semnum, q, count_zero);
1130        }
1131        if (count_zero) {
1132                list_for_each_entry(q, &sma->pending_const, list) {
1133                        semcnt += check_qop(sma, semnum, q, count_zero);
1134                }
1135        }
1136        return semcnt;
1137}
1138
1139/* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
1140 * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
1141 * remains locked on exit.
1142 */
1143static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
1144{
1145        struct sem_undo *un, *tu;
1146        struct sem_queue *q, *tq;
1147        struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1148        int i;
1149        DEFINE_WAKE_Q(wake_q);
1150
1151        /* Free the existing undo structures for this semaphore set.  */
1152        ipc_assert_locked_object(&sma->sem_perm);
1153        list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
1154                list_del(&un->list_id);
1155                spin_lock(&un->ulp->lock);
1156                un->semid = -1;
1157                list_del_rcu(&un->list_proc);
1158                spin_unlock(&un->ulp->lock);
1159                kvfree_rcu(un, rcu);
1160        }
1161
1162        /* Wake up all pending processes and let them fail with EIDRM. */
1163        list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
1164                unlink_queue(sma, q);
1165                wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1166        }
1167
1168        list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1169                unlink_queue(sma, q);
1170                wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1171        }
1172        for (i = 0; i < sma->sem_nsems; i++) {
1173                struct sem *sem = &sma->sems[i];
1174                list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
1175                        unlink_queue(sma, q);
1176                        wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1177                }
1178                list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1179                        unlink_queue(sma, q);
1180                        wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
1181                }
1182                ipc_update_pid(&sem->sempid, NULL);
1183        }
1184
1185        /* Remove the semaphore set from the IDR */
1186        sem_rmid(ns, sma);
1187        sem_unlock(sma, -1);
1188        rcu_read_unlock();
1189
1190        wake_up_q(&wake_q);
1191        ns->used_sems -= sma->sem_nsems;
1192        ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1193}
1194
1195static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
1196{
1197        switch (version) {
1198        case IPC_64:
1199                return copy_to_user(buf, in, sizeof(*in));
1200        case IPC_OLD:
1201            {
1202                struct semid_ds out;
1203
1204                memset(&out, 0, sizeof(out));
1205
1206                ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
1207
1208                out.sem_otime   = in->sem_otime;
1209                out.sem_ctime   = in->sem_ctime;
1210                out.sem_nsems   = in->sem_nsems;
1211
1212                return copy_to_user(buf, &out, sizeof(out));
1213            }
1214        default:
1215                return -EINVAL;
1216        }
1217}
1218
1219static time64_t get_semotime(struct sem_array *sma)
1220{
1221        int i;
1222        time64_t res;
1223
1224        res = sma->sems[0].sem_otime;
1225        for (i = 1; i < sma->sem_nsems; i++) {
1226                time64_t to = sma->sems[i].sem_otime;
1227
1228                if (to > res)
1229                        res = to;
1230        }
1231        return res;
1232}
1233
1234static int semctl_stat(struct ipc_namespace *ns, int semid,
1235                         int cmd, struct semid64_ds *semid64)
1236{
1237        struct sem_array *sma;
1238        time64_t semotime;
1239        int err;
1240
1241        memset(semid64, 0, sizeof(*semid64));
1242
1243        rcu_read_lock();
1244        if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) {
1245                sma = sem_obtain_object(ns, semid);
1246                if (IS_ERR(sma)) {
1247                        err = PTR_ERR(sma);
1248                        goto out_unlock;
1249                }
1250        } else { /* IPC_STAT */
1251                sma = sem_obtain_object_check(ns, semid);
1252                if (IS_ERR(sma)) {
1253                        err = PTR_ERR(sma);
1254                        goto out_unlock;
1255                }
1256        }
1257
1258        /* see comment for SHM_STAT_ANY */
1259        if (cmd == SEM_STAT_ANY)
1260                audit_ipc_obj(&sma->sem_perm);
1261        else {
1262                err = -EACCES;
1263                if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
1264                        goto out_unlock;
1265        }
1266
1267        err = security_sem_semctl(&sma->sem_perm, cmd);
1268        if (err)
1269                goto out_unlock;
1270
1271        ipc_lock_object(&sma->sem_perm);
1272
1273        if (!ipc_valid_object(&sma->sem_perm)) {
1274                ipc_unlock_object(&sma->sem_perm);
1275                err = -EIDRM;
1276                goto out_unlock;
1277        }
1278
1279        kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
1280        semotime = get_semotime(sma);
1281        semid64->sem_otime = semotime;
1282        semid64->sem_ctime = sma->sem_ctime;
1283#ifndef CONFIG_64BIT
1284        semid64->sem_otime_high = semotime >> 32;
1285        semid64->sem_ctime_high = sma->sem_ctime >> 32;
1286#endif
1287        semid64->sem_nsems = sma->sem_nsems;
1288
1289        if (cmd == IPC_STAT) {
1290                /*
1291                 * As defined in SUS:
1292                 * Return 0 on success
1293                 */
1294                err = 0;
1295        } else {
1296                /*
1297                 * SEM_STAT and SEM_STAT_ANY (both Linux specific)
1298                 * Return the full id, including the sequence number
1299                 */
1300                err = sma->sem_perm.id;
1301        }
1302        ipc_unlock_object(&sma->sem_perm);
1303out_unlock:
1304        rcu_read_unlock();
1305        return err;
1306}
1307
1308static int semctl_info(struct ipc_namespace *ns, int semid,
1309                         int cmd, void __user *p)
1310{
1311        struct seminfo seminfo;
1312        int max_idx;
1313        int err;
1314
1315        err = security_sem_semctl(NULL, cmd);
1316        if (err)
1317                return err;
1318
1319        memset(&seminfo, 0, sizeof(seminfo));
1320        seminfo.semmni = ns->sc_semmni;
1321        seminfo.semmns = ns->sc_semmns;
1322        seminfo.semmsl = ns->sc_semmsl;
1323        seminfo.semopm = ns->sc_semopm;
1324        seminfo.semvmx = SEMVMX;
1325        seminfo.semmnu = SEMMNU;
1326        seminfo.semmap = SEMMAP;
1327        seminfo.semume = SEMUME;
1328        down_read(&sem_ids(ns).rwsem);
1329        if (cmd == SEM_INFO) {
1330                seminfo.semusz = sem_ids(ns).in_use;
1331                seminfo.semaem = ns->used_sems;
1332        } else {
1333                seminfo.semusz = SEMUSZ;
1334                seminfo.semaem = SEMAEM;
1335        }
1336        max_idx = ipc_get_maxidx(&sem_ids(ns));
1337        up_read(&sem_ids(ns).rwsem);
1338        if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
1339                return -EFAULT;
1340        return (max_idx < 0) ? 0 : max_idx;
1341}
1342
1343static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
1344                int val)
1345{
1346        struct sem_undo *un;
1347        struct sem_array *sma;
1348        struct sem *curr;
1349        int err;
1350        DEFINE_WAKE_Q(wake_q);
1351
1352        if (val > SEMVMX || val < 0)
1353                return -ERANGE;
1354
1355        rcu_read_lock();
1356        sma = sem_obtain_object_check(ns, semid);
1357        if (IS_ERR(sma)) {
1358                rcu_read_unlock();
1359                return PTR_ERR(sma);
1360        }
1361
1362        if (semnum < 0 || semnum >= sma->sem_nsems) {
1363                rcu_read_unlock();
1364                return -EINVAL;
1365        }
1366
1367
1368        if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
1369                rcu_read_unlock();
1370                return -EACCES;
1371        }
1372
1373        err = security_sem_semctl(&sma->sem_perm, SETVAL);
1374        if (err) {
1375                rcu_read_unlock();
1376                return -EACCES;
1377        }
1378
1379        sem_lock(sma, NULL, -1);
1380
1381        if (!ipc_valid_object(&sma->sem_perm)) {
1382                sem_unlock(sma, -1);
1383                rcu_read_unlock();
1384                return -EIDRM;
1385        }
1386
1387        semnum = array_index_nospec(semnum, sma->sem_nsems);
1388        curr = &sma->sems[semnum];
1389
1390        ipc_assert_locked_object(&sma->sem_perm);
1391        list_for_each_entry(un, &sma->list_id, list_id)
1392                un->semadj[semnum] = 0;
1393
1394        curr->semval = val;
1395        ipc_update_pid(&curr->sempid, task_tgid(current));
1396        sma->sem_ctime = ktime_get_real_seconds();
1397        /* maybe some queued-up processes were waiting for this */
1398        do_smart_update(sma, NULL, 0, 0, &wake_q);
1399        sem_unlock(sma, -1);
1400        rcu_read_unlock();
1401        wake_up_q(&wake_q);
1402        return 0;
1403}
1404
1405static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1406                int cmd, void __user *p)
1407{
1408        struct sem_array *sma;
1409        struct sem *curr;
1410        int err, nsems;
1411        ushort fast_sem_io[SEMMSL_FAST];
1412        ushort *sem_io = fast_sem_io;
1413        DEFINE_WAKE_Q(wake_q);
1414
1415        rcu_read_lock();
1416        sma = sem_obtain_object_check(ns, semid);
1417        if (IS_ERR(sma)) {
1418                rcu_read_unlock();
1419                return PTR_ERR(sma);
1420        }
1421
1422        nsems = sma->sem_nsems;
1423
1424        err = -EACCES;
1425        if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
1426                goto out_rcu_wakeup;
1427
1428        err = security_sem_semctl(&sma->sem_perm, cmd);
1429        if (err)
1430                goto out_rcu_wakeup;
1431
1432        switch (cmd) {
1433        case GETALL:
1434        {
1435                ushort __user *array = p;
1436                int i;
1437
1438                sem_lock(sma, NULL, -1);
1439                if (!ipc_valid_object(&sma->sem_perm)) {
1440                        err = -EIDRM;
1441                        goto out_unlock;
1442                }
1443                if (nsems > SEMMSL_FAST) {
1444                        if (!ipc_rcu_getref(&sma->sem_perm)) {
1445                                err = -EIDRM;
1446                                goto out_unlock;
1447                        }
1448                        sem_unlock(sma, -1);
1449                        rcu_read_unlock();
1450                        sem_io = kvmalloc_array(nsems, sizeof(ushort),
1451                                                GFP_KERNEL);
1452                        if (sem_io == NULL) {
1453                                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1454                                return -ENOMEM;
1455                        }
1456
1457                        rcu_read_lock();
1458                        sem_lock_and_putref(sma);
1459                        if (!ipc_valid_object(&sma->sem_perm)) {
1460                                err = -EIDRM;
1461                                goto out_unlock;
1462                        }
1463                }
1464                for (i = 0; i < sma->sem_nsems; i++)
1465                        sem_io[i] = sma->sems[i].semval;
1466                sem_unlock(sma, -1);
1467                rcu_read_unlock();
1468                err = 0;
1469                if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
1470                        err = -EFAULT;
1471                goto out_free;
1472        }
1473        case SETALL:
1474        {
1475                int i;
1476                struct sem_undo *un;
1477
1478                if (!ipc_rcu_getref(&sma->sem_perm)) {
1479                        err = -EIDRM;
1480                        goto out_rcu_wakeup;
1481                }
1482                rcu_read_unlock();
1483
1484                if (nsems > SEMMSL_FAST) {
1485                        sem_io = kvmalloc_array(nsems, sizeof(ushort),
1486                                                GFP_KERNEL);
1487                        if (sem_io == NULL) {
1488                                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1489                                return -ENOMEM;
1490                        }
1491                }
1492
1493                if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
1494                        ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1495                        err = -EFAULT;
1496                        goto out_free;
1497                }
1498
1499                for (i = 0; i < nsems; i++) {
1500                        if (sem_io[i] > SEMVMX) {
1501                                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1502                                err = -ERANGE;
1503                                goto out_free;
1504                        }
1505                }
1506                rcu_read_lock();
1507                sem_lock_and_putref(sma);
1508                if (!ipc_valid_object(&sma->sem_perm)) {
1509                        err = -EIDRM;
1510                        goto out_unlock;
1511                }
1512
1513                for (i = 0; i < nsems; i++) {
1514                        sma->sems[i].semval = sem_io[i];
1515                        ipc_update_pid(&sma->sems[i].sempid, task_tgid(current));
1516                }
1517
1518                ipc_assert_locked_object(&sma->sem_perm);
1519                list_for_each_entry(un, &sma->list_id, list_id) {
1520                        for (i = 0; i < nsems; i++)
1521                                un->semadj[i] = 0;
1522                }
1523                sma->sem_ctime = ktime_get_real_seconds();
1524                /* maybe some queued-up processes were waiting for this */
1525                do_smart_update(sma, NULL, 0, 0, &wake_q);
1526                err = 0;
1527                goto out_unlock;
1528        }
1529        /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
1530        }
1531        err = -EINVAL;
1532        if (semnum < 0 || semnum >= nsems)
1533                goto out_rcu_wakeup;
1534
1535        sem_lock(sma, NULL, -1);
1536        if (!ipc_valid_object(&sma->sem_perm)) {
1537                err = -EIDRM;
1538                goto out_unlock;
1539        }
1540
1541        semnum = array_index_nospec(semnum, nsems);
1542        curr = &sma->sems[semnum];
1543
1544        switch (cmd) {
1545        case GETVAL:
1546                err = curr->semval;
1547                goto out_unlock;
1548        case GETPID:
1549                err = pid_vnr(curr->sempid);
1550                goto out_unlock;
1551        case GETNCNT:
1552                err = count_semcnt(sma, semnum, 0);
1553                goto out_unlock;
1554        case GETZCNT:
1555                err = count_semcnt(sma, semnum, 1);
1556                goto out_unlock;
1557        }
1558
1559out_unlock:
1560        sem_unlock(sma, -1);
1561out_rcu_wakeup:
1562        rcu_read_unlock();
1563        wake_up_q(&wake_q);
1564out_free:
1565        if (sem_io != fast_sem_io)
1566                kvfree(sem_io);
1567        return err;
1568}
1569
1570static inline unsigned long
1571copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
1572{
1573        switch (version) {
1574        case IPC_64:
1575                if (copy_from_user(out, buf, sizeof(*out)))
1576                        return -EFAULT;
1577                return 0;
1578        case IPC_OLD:
1579            {
1580                struct semid_ds tbuf_old;
1581
1582                if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
1583                        return -EFAULT;
1584
1585                out->sem_perm.uid       = tbuf_old.sem_perm.uid;
1586                out->sem_perm.gid       = tbuf_old.sem_perm.gid;
1587                out->sem_perm.mode      = tbuf_old.sem_perm.mode;
1588
1589                return 0;
1590            }
1591        default:
1592                return -EINVAL;
1593        }
1594}
1595
1596/*
1597 * This function handles some semctl commands which require the rwsem
1598 * to be held in write mode.
1599 * NOTE: no locks must be held, the rwsem is taken inside this function.
1600 */
1601static int semctl_down(struct ipc_namespace *ns, int semid,
1602                       int cmd, struct semid64_ds *semid64)
1603{
1604        struct sem_array *sma;
1605        int err;
1606        struct kern_ipc_perm *ipcp;
1607
1608        down_write(&sem_ids(ns).rwsem);
1609        rcu_read_lock();
1610
1611        ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
1612                                      &semid64->sem_perm, 0);
1613        if (IS_ERR(ipcp)) {
1614                err = PTR_ERR(ipcp);
1615                goto out_unlock1;
1616        }
1617
1618        sma = container_of(ipcp, struct sem_array, sem_perm);
1619
1620        err = security_sem_semctl(&sma->sem_perm, cmd);
1621        if (err)
1622                goto out_unlock1;
1623
1624        switch (cmd) {
1625        case IPC_RMID:
1626                sem_lock(sma, NULL, -1);
1627                /* freeary unlocks the ipc object and rcu */
1628                freeary(ns, ipcp);
1629                goto out_up;
1630        case IPC_SET:
1631                sem_lock(sma, NULL, -1);
1632                err = ipc_update_perm(&semid64->sem_perm, ipcp);
1633                if (err)
1634                        goto out_unlock0;
1635                sma->sem_ctime = ktime_get_real_seconds();
1636                break;
1637        default:
1638                err = -EINVAL;
1639                goto out_unlock1;
1640        }
1641
1642out_unlock0:
1643        sem_unlock(sma, -1);
1644out_unlock1:
1645        rcu_read_unlock();
1646out_up:
1647        up_write(&sem_ids(ns).rwsem);
1648        return err;
1649}
1650
1651static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version)
1652{
1653        struct ipc_namespace *ns;
1654        void __user *p = (void __user *)arg;
1655        struct semid64_ds semid64;
1656        int err;
1657
1658        if (semid < 0)
1659                return -EINVAL;
1660
1661        ns = current->nsproxy->ipc_ns;
1662
1663        switch (cmd) {
1664        case IPC_INFO:
1665        case SEM_INFO:
1666                return semctl_info(ns, semid, cmd, p);
1667        case IPC_STAT:
1668        case SEM_STAT:
1669        case SEM_STAT_ANY:
1670                err = semctl_stat(ns, semid, cmd, &semid64);
1671                if (err < 0)
1672                        return err;
1673                if (copy_semid_to_user(p, &semid64, version))
1674                        err = -EFAULT;
1675                return err;
1676        case GETALL:
1677        case GETVAL:
1678        case GETPID:
1679        case GETNCNT:
1680        case GETZCNT:
1681        case SETALL:
1682                return semctl_main(ns, semid, semnum, cmd, p);
1683        case SETVAL: {
1684                int val;
1685#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
1686                /* big-endian 64bit */
1687                val = arg >> 32;
1688#else
1689                /* 32bit or little-endian 64bit */
1690                val = arg;
1691#endif
1692                return semctl_setval(ns, semid, semnum, val);
1693        }
1694        case IPC_SET:
1695                if (copy_semid_from_user(&semid64, p, version))
1696                        return -EFAULT;
1697                fallthrough;
1698        case IPC_RMID:
1699                return semctl_down(ns, semid, cmd, &semid64);
1700        default:
1701                return -EINVAL;
1702        }
1703}
1704
1705SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1706{
1707        return ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1708}
1709
1710#ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
1711long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg)
1712{
1713        int version = ipc_parse_version(&cmd);
1714
1715        return ksys_semctl(semid, semnum, cmd, arg, version);
1716}
1717
1718SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
1719{
1720        return ksys_old_semctl(semid, semnum, cmd, arg);
1721}
1722#endif
1723
1724#ifdef CONFIG_COMPAT
1725
1726struct compat_semid_ds {
1727        struct compat_ipc_perm sem_perm;
1728        old_time32_t sem_otime;
1729        old_time32_t sem_ctime;
1730        compat_uptr_t sem_base;
1731        compat_uptr_t sem_pending;
1732        compat_uptr_t sem_pending_last;
1733        compat_uptr_t undo;
1734        unsigned short sem_nsems;
1735};
1736
1737static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf,
1738                                        int version)
1739{
1740        memset(out, 0, sizeof(*out));
1741        if (version == IPC_64) {
1742                struct compat_semid64_ds __user *p = buf;
1743                return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm);
1744        } else {
1745                struct compat_semid_ds __user *p = buf;
1746                return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm);
1747        }
1748}
1749
1750static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in,
1751                                        int version)
1752{
1753        if (version == IPC_64) {
1754                struct compat_semid64_ds v;
1755                memset(&v, 0, sizeof(v));
1756                to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm);
1757                v.sem_otime      = lower_32_bits(in->sem_otime);
1758                v.sem_otime_high = upper_32_bits(in->sem_otime);
1759                v.sem_ctime      = lower_32_bits(in->sem_ctime);
1760                v.sem_ctime_high = upper_32_bits(in->sem_ctime);
1761                v.sem_nsems = in->sem_nsems;
1762                return copy_to_user(buf, &v, sizeof(v));
1763        } else {
1764                struct compat_semid_ds v;
1765                memset(&v, 0, sizeof(v));
1766                to_compat_ipc_perm(&v.sem_perm, &in->sem_perm);
1767                v.sem_otime = in->sem_otime;
1768                v.sem_ctime = in->sem_ctime;
1769                v.sem_nsems = in->sem_nsems;
1770                return copy_to_user(buf, &v, sizeof(v));
1771        }
1772}
1773
1774static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version)
1775{
1776        void __user *p = compat_ptr(arg);
1777        struct ipc_namespace *ns;
1778        struct semid64_ds semid64;
1779        int err;
1780
1781        ns = current->nsproxy->ipc_ns;
1782
1783        if (semid < 0)
1784                return -EINVAL;
1785
1786        switch (cmd & (~IPC_64)) {
1787        case IPC_INFO:
1788        case SEM_INFO:
1789                return semctl_info(ns, semid, cmd, p);
1790        case IPC_STAT:
1791        case SEM_STAT:
1792        case SEM_STAT_ANY:
1793                err = semctl_stat(ns, semid, cmd, &semid64);
1794                if (err < 0)
1795                        return err;
1796                if (copy_compat_semid_to_user(p, &semid64, version))
1797                        err = -EFAULT;
1798                return err;
1799        case GETVAL:
1800        case GETPID:
1801        case GETNCNT:
1802        case GETZCNT:
1803        case GETALL:
1804        case SETALL:
1805                return semctl_main(ns, semid, semnum, cmd, p);
1806        case SETVAL:
1807                return semctl_setval(ns, semid, semnum, arg);
1808        case IPC_SET:
1809                if (copy_compat_semid_from_user(&semid64, p, version))
1810                        return -EFAULT;
1811                fallthrough;
1812        case IPC_RMID:
1813                return semctl_down(ns, semid, cmd, &semid64);
1814        default:
1815                return -EINVAL;
1816        }
1817}
1818
1819COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
1820{
1821        return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64);
1822}
1823
1824#ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
1825long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg)
1826{
1827        int version = compat_ipc_parse_version(&cmd);
1828
1829        return compat_ksys_semctl(semid, semnum, cmd, arg, version);
1830}
1831
1832COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg)
1833{
1834        return compat_ksys_old_semctl(semid, semnum, cmd, arg);
1835}
1836#endif
1837#endif
1838
1839/* If the task doesn't already have a undo_list, then allocate one
1840 * here.  We guarantee there is only one thread using this undo list,
1841 * and current is THE ONE
1842 *
1843 * If this allocation and assignment succeeds, but later
1844 * portions of this code fail, there is no need to free the sem_undo_list.
1845 * Just let it stay associated with the task, and it'll be freed later
1846 * at exit time.
1847 *
1848 * This can block, so callers must hold no locks.
1849 */
1850static inline int get_undo_list(struct sem_undo_list **undo_listp)
1851{
1852        struct sem_undo_list *undo_list;
1853
1854        undo_list = current->sysvsem.undo_list;
1855        if (!undo_list) {
1856                undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL_ACCOUNT);
1857                if (undo_list == NULL)
1858                        return -ENOMEM;
1859                spin_lock_init(&undo_list->lock);
1860                refcount_set(&undo_list->refcnt, 1);
1861                INIT_LIST_HEAD(&undo_list->list_proc);
1862
1863                current->sysvsem.undo_list = undo_list;
1864        }
1865        *undo_listp = undo_list;
1866        return 0;
1867}
1868
1869static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
1870{
1871        struct sem_undo *un;
1872
1873        list_for_each_entry_rcu(un, &ulp->list_proc, list_proc,
1874                                spin_is_locked(&ulp->lock)) {
1875                if (un->semid == semid)
1876                        return un;
1877        }
1878        return NULL;
1879}
1880
1881static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
1882{
1883        struct sem_undo *un;
1884
1885        assert_spin_locked(&ulp->lock);
1886
1887        un = __lookup_undo(ulp, semid);
1888        if (un) {
1889                list_del_rcu(&un->list_proc);
1890                list_add_rcu(&un->list_proc, &ulp->list_proc);
1891        }
1892        return un;
1893}
1894
1895/**
1896 * find_alloc_undo - lookup (and if not present create) undo array
1897 * @ns: namespace
1898 * @semid: semaphore array id
1899 *
1900 * The function looks up (and if not present creates) the undo structure.
1901 * The size of the undo structure depends on the size of the semaphore
1902 * array, thus the alloc path is not that straightforward.
1903 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
1904 * performs a rcu_read_lock().
1905 */
1906static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
1907{
1908        struct sem_array *sma;
1909        struct sem_undo_list *ulp;
1910        struct sem_undo *un, *new;
1911        int nsems, error;
1912
1913        error = get_undo_list(&ulp);
1914        if (error)
1915                return ERR_PTR(error);
1916
1917        rcu_read_lock();
1918        spin_lock(&ulp->lock);
1919        un = lookup_undo(ulp, semid);
1920        spin_unlock(&ulp->lock);
1921        if (likely(un != NULL))
1922                goto out;
1923
1924        /* no undo structure around - allocate one. */
1925        /* step 1: figure out the size of the semaphore array */
1926        sma = sem_obtain_object_check(ns, semid);
1927        if (IS_ERR(sma)) {
1928                rcu_read_unlock();
1929                return ERR_CAST(sma);
1930        }
1931
1932        nsems = sma->sem_nsems;
1933        if (!ipc_rcu_getref(&sma->sem_perm)) {
1934                rcu_read_unlock();
1935                un = ERR_PTR(-EIDRM);
1936                goto out;
1937        }
1938        rcu_read_unlock();
1939
1940        /* step 2: allocate new undo structure */
1941        new = kvzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems,
1942                       GFP_KERNEL_ACCOUNT);
1943        if (!new) {
1944                ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
1945                return ERR_PTR(-ENOMEM);
1946        }
1947
1948        /* step 3: Acquire the lock on semaphore array */
1949        rcu_read_lock();
1950        sem_lock_and_putref(sma);
1951        if (!ipc_valid_object(&sma->sem_perm)) {
1952                sem_unlock(sma, -1);
1953                rcu_read_unlock();
1954                kvfree(new);
1955                un = ERR_PTR(-EIDRM);
1956                goto out;
1957        }
1958        spin_lock(&ulp->lock);
1959
1960        /*
1961         * step 4: check for races: did someone else allocate the undo struct?
1962         */
1963        un = lookup_undo(ulp, semid);
1964        if (un) {
1965                spin_unlock(&ulp->lock);
1966                kvfree(new);
1967                goto success;
1968        }
1969        /* step 5: initialize & link new undo structure */
1970        new->semadj = (short *) &new[1];
1971        new->ulp = ulp;
1972        new->semid = semid;
1973        assert_spin_locked(&ulp->lock);
1974        list_add_rcu(&new->list_proc, &ulp->list_proc);
1975        ipc_assert_locked_object(&sma->sem_perm);
1976        list_add(&new->list_id, &sma->list_id);
1977        un = new;
1978        spin_unlock(&ulp->lock);
1979success:
1980        sem_unlock(sma, -1);
1981out:
1982        return un;
1983}
1984
1985long __do_semtimedop(int semid, struct sembuf *sops,
1986                unsigned nsops, const struct timespec64 *timeout,
1987                struct ipc_namespace *ns)
1988{
1989        int error = -EINVAL;
1990        struct sem_array *sma;
1991        struct sembuf *sop;
1992        struct sem_undo *un;
1993        int max, locknum;
1994        bool undos = false, alter = false, dupsop = false;
1995        struct sem_queue queue;
1996        unsigned long dup = 0;
1997        ktime_t expires, *exp = NULL;
1998        bool timed_out = false;
1999
2000        if (nsops < 1 || semid < 0)
2001                return -EINVAL;
2002        if (nsops > ns->sc_semopm)
2003                return -E2BIG;
2004
2005        if (timeout) {
2006                if (!timespec64_valid(timeout))
2007                        return -EINVAL;
2008                expires = ktime_add_safe(ktime_get(),
2009                                timespec64_to_ktime(*timeout));
2010                exp = &expires;
2011        }
2012
2013
2014        max = 0;
2015        for (sop = sops; sop < sops + nsops; sop++) {
2016                unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
2017
2018                if (sop->sem_num >= max)
2019                        max = sop->sem_num;
2020                if (sop->sem_flg & SEM_UNDO)
2021                        undos = true;
2022                if (dup & mask) {
2023                        /*
2024                         * There was a previous alter access that appears
2025                         * to have accessed the same semaphore, thus use
2026                         * the dupsop logic. "appears", because the detection
2027                         * can only check % BITS_PER_LONG.
2028                         */
2029                        dupsop = true;
2030                }
2031                if (sop->sem_op != 0) {
2032                        alter = true;
2033                        dup |= mask;
2034                }
2035        }
2036
2037        if (undos) {
2038                /* On success, find_alloc_undo takes the rcu_read_lock */
2039                un = find_alloc_undo(ns, semid);
2040                if (IS_ERR(un)) {
2041                        error = PTR_ERR(un);
2042                        goto out;
2043                }
2044        } else {
2045                un = NULL;
2046                rcu_read_lock();
2047        }
2048
2049        sma = sem_obtain_object_check(ns, semid);
2050        if (IS_ERR(sma)) {
2051                rcu_read_unlock();
2052                error = PTR_ERR(sma);
2053                goto out;
2054        }
2055
2056        error = -EFBIG;
2057        if (max >= sma->sem_nsems) {
2058                rcu_read_unlock();
2059                goto out;
2060        }
2061
2062        error = -EACCES;
2063        if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
2064                rcu_read_unlock();
2065                goto out;
2066        }
2067
2068        error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
2069        if (error) {
2070                rcu_read_unlock();
2071                goto out;
2072        }
2073
2074        error = -EIDRM;
2075        locknum = sem_lock(sma, sops, nsops);
2076        /*
2077         * We eventually might perform the following check in a lockless
2078         * fashion, considering ipc_valid_object() locking constraints.
2079         * If nsops == 1 and there is no contention for sem_perm.lock, then
2080         * only a per-semaphore lock is held and it's OK to proceed with the
2081         * check below. More details on the fine grained locking scheme
2082         * entangled here and why it's RMID race safe on comments at sem_lock()
2083         */
2084        if (!ipc_valid_object(&sma->sem_perm))
2085                goto out_unlock;
2086        /*
2087         * semid identifiers are not unique - find_alloc_undo may have
2088         * allocated an undo structure, it was invalidated by an RMID
2089         * and now a new array with received the same id. Check and fail.
2090         * This case can be detected checking un->semid. The existence of
2091         * "un" itself is guaranteed by rcu.
2092         */
2093        if (un && un->semid == -1)
2094                goto out_unlock;
2095
2096        queue.sops = sops;
2097        queue.nsops = nsops;
2098        queue.undo = un;
2099        queue.pid = task_tgid(current);
2100        queue.alter = alter;
2101        queue.dupsop = dupsop;
2102
2103        error = perform_atomic_semop(sma, &queue);
2104        if (error == 0) { /* non-blocking successful path */
2105                DEFINE_WAKE_Q(wake_q);
2106
2107                /*
2108                 * If the operation was successful, then do
2109                 * the required updates.
2110                 */
2111                if (alter)
2112                        do_smart_update(sma, sops, nsops, 1, &wake_q);
2113                else
2114                        set_semotime(sma, sops);
2115
2116                sem_unlock(sma, locknum);
2117                rcu_read_unlock();
2118                wake_up_q(&wake_q);
2119
2120                goto out;
2121        }
2122        if (error < 0) /* non-blocking error path */
2123                goto out_unlock;
2124
2125        /*
2126         * We need to sleep on this operation, so we put the current
2127         * task into the pending queue and go to sleep.
2128         */
2129        if (nsops == 1) {
2130                struct sem *curr;
2131                int idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
2132                curr = &sma->sems[idx];
2133
2134                if (alter) {
2135                        if (sma->complex_count) {
2136                                list_add_tail(&queue.list,
2137                                                &sma->pending_alter);
2138                        } else {
2139
2140                                list_add_tail(&queue.list,
2141                                                &curr->pending_alter);
2142                        }
2143                } else {
2144                        list_add_tail(&queue.list, &curr->pending_const);
2145                }
2146        } else {
2147                if (!sma->complex_count)
2148                        merge_queues(sma);
2149
2150                if (alter)
2151                        list_add_tail(&queue.list, &sma->pending_alter);
2152                else
2153                        list_add_tail(&queue.list, &sma->pending_const);
2154
2155                sma->complex_count++;
2156        }
2157
2158        do {
2159                /* memory ordering ensured by the lock in sem_lock() */
2160                WRITE_ONCE(queue.status, -EINTR);
2161                queue.sleeper = current;
2162
2163                /* memory ordering is ensured by the lock in sem_lock() */
2164                __set_current_state(TASK_INTERRUPTIBLE);
2165                sem_unlock(sma, locknum);
2166                rcu_read_unlock();
2167
2168                timed_out = !schedule_hrtimeout_range(exp,
2169                                current->timer_slack_ns, HRTIMER_MODE_ABS);
2170
2171                /*
2172                 * fastpath: the semop has completed, either successfully or
2173                 * not, from the syscall pov, is quite irrelevant to us at this
2174                 * point; we're done.
2175                 *
2176                 * We _do_ care, nonetheless, about being awoken by a signal or
2177                 * spuriously.  The queue.status is checked again in the
2178                 * slowpath (aka after taking sem_lock), such that we can detect
2179                 * scenarios where we were awakened externally, during the
2180                 * window between wake_q_add() and wake_up_q().
2181                 */
2182                error = READ_ONCE(queue.status);
2183                if (error != -EINTR) {
2184                        /* see SEM_BARRIER_2 for purpose/pairing */
2185                        smp_acquire__after_ctrl_dep();
2186                        goto out;
2187                }
2188
2189                rcu_read_lock();
2190                locknum = sem_lock(sma, sops, nsops);
2191
2192                if (!ipc_valid_object(&sma->sem_perm))
2193                        goto out_unlock;
2194
2195                /*
2196                 * No necessity for any barrier: We are protect by sem_lock()
2197                 */
2198                error = READ_ONCE(queue.status);
2199
2200                /*
2201                 * If queue.status != -EINTR we are woken up by another process.
2202                 * Leave without unlink_queue(), but with sem_unlock().
2203                 */
2204                if (error != -EINTR)
2205                        goto out_unlock;
2206
2207                /*
2208                 * If an interrupt occurred we have to clean up the queue.
2209                 */
2210                if (timed_out)
2211                        error = -EAGAIN;
2212        } while (error == -EINTR && !signal_pending(current)); /* spurious */
2213
2214        unlink_queue(sma, &queue);
2215
2216out_unlock:
2217        sem_unlock(sma, locknum);
2218        rcu_read_unlock();
2219out:
2220        return error;
2221}
2222
2223static long do_semtimedop(int semid, struct sembuf __user *tsops,
2224                unsigned nsops, const struct timespec64 *timeout)
2225{
2226        struct sembuf fast_sops[SEMOPM_FAST];
2227        struct sembuf *sops = fast_sops;
2228        struct ipc_namespace *ns;
2229        int ret;
2230
2231        ns = current->nsproxy->ipc_ns;
2232        if (nsops > ns->sc_semopm)
2233                return -E2BIG;
2234        if (nsops < 1)
2235                return -EINVAL;
2236
2237        if (nsops > SEMOPM_FAST) {
2238                sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
2239                if (sops == NULL)
2240                        return -ENOMEM;
2241        }
2242
2243        if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
2244                ret =  -EFAULT;
2245                goto out_free;
2246        }
2247
2248        ret = __do_semtimedop(semid, sops, nsops, timeout, ns);
2249
2250out_free:
2251        if (sops != fast_sops)
2252                kvfree(sops);
2253
2254        return ret;
2255}
2256
2257long ksys_semtimedop(int semid, struct sembuf __user *tsops,
2258                     unsigned int nsops, const struct __kernel_timespec __user *timeout)
2259{
2260        if (timeout) {
2261                struct timespec64 ts;
2262                if (get_timespec64(&ts, timeout))
2263                        return -EFAULT;
2264                return do_semtimedop(semid, tsops, nsops, &ts);
2265        }
2266        return do_semtimedop(semid, tsops, nsops, NULL);
2267}
2268
2269SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
2270                unsigned int, nsops, const struct __kernel_timespec __user *, timeout)
2271{
2272        return ksys_semtimedop(semid, tsops, nsops, timeout);
2273}
2274
2275#ifdef CONFIG_COMPAT_32BIT_TIME
2276long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
2277                            unsigned int nsops,
2278                            const struct old_timespec32 __user *timeout)
2279{
2280        if (timeout) {
2281                struct timespec64 ts;
2282                if (get_old_timespec32(&ts, timeout))
2283                        return -EFAULT;
2284                return do_semtimedop(semid, tsems, nsops, &ts);
2285        }
2286        return do_semtimedop(semid, tsems, nsops, NULL);
2287}
2288
2289SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems,
2290                       unsigned int, nsops,
2291                       const struct old_timespec32 __user *, timeout)
2292{
2293        return compat_ksys_semtimedop(semid, tsems, nsops, timeout);
2294}
2295#endif
2296
2297SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
2298                unsigned, nsops)
2299{
2300        return do_semtimedop(semid, tsops, nsops, NULL);
2301}
2302
2303/* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
2304 * parent and child tasks.
2305 */
2306
2307int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
2308{
2309        struct sem_undo_list *undo_list;
2310        int error;
2311
2312        if (clone_flags & CLONE_SYSVSEM) {
2313                error = get_undo_list(&undo_list);
2314                if (error)
2315                        return error;
2316                refcount_inc(&undo_list->refcnt);
2317                tsk->sysvsem.undo_list = undo_list;
2318        } else
2319                tsk->sysvsem.undo_list = NULL;
2320
2321        return 0;
2322}
2323
2324/*
2325 * add semadj values to semaphores, free undo structures.
2326 * undo structures are not freed when semaphore arrays are destroyed
2327 * so some of them may be out of date.
2328 * IMPLEMENTATION NOTE: There is some confusion over whether the
2329 * set of adjustments that needs to be done should be done in an atomic
2330 * manner or not. That is, if we are attempting to decrement the semval
2331 * should we queue up and wait until we can do so legally?
2332 * The original implementation attempted to do this (queue and wait).
2333 * The current implementation does not do so. The POSIX standard
2334 * and SVID should be consulted to determine what behavior is mandated.
2335 */
2336void exit_sem(struct task_struct *tsk)
2337{
2338        struct sem_undo_list *ulp;
2339
2340        ulp = tsk->sysvsem.undo_list;
2341        if (!ulp)
2342                return;
2343        tsk->sysvsem.undo_list = NULL;
2344
2345        if (!refcount_dec_and_test(&ulp->refcnt))
2346                return;
2347
2348        for (;;) {
2349                struct sem_array *sma;
2350                struct sem_undo *un;
2351                int semid, i;
2352                DEFINE_WAKE_Q(wake_q);
2353
2354                cond_resched();
2355
2356                rcu_read_lock();
2357                un = list_entry_rcu(ulp->list_proc.next,
2358                                    struct sem_undo, list_proc);
2359                if (&un->list_proc == &ulp->list_proc) {
2360                        /*
2361                         * We must wait for freeary() before freeing this ulp,
2362                         * in case we raced with last sem_undo. There is a small
2363                         * possibility where we exit while freeary() didn't
2364                         * finish unlocking sem_undo_list.
2365                         */
2366                        spin_lock(&ulp->lock);
2367                        spin_unlock(&ulp->lock);
2368                        rcu_read_unlock();
2369                        break;
2370                }
2371                spin_lock(&ulp->lock);
2372                semid = un->semid;
2373                spin_unlock(&ulp->lock);
2374
2375                /* exit_sem raced with IPC_RMID, nothing to do */
2376                if (semid == -1) {
2377                        rcu_read_unlock();
2378                        continue;
2379                }
2380
2381                sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
2382                /* exit_sem raced with IPC_RMID, nothing to do */
2383                if (IS_ERR(sma)) {
2384                        rcu_read_unlock();
2385                        continue;
2386                }
2387
2388                sem_lock(sma, NULL, -1);
2389                /* exit_sem raced with IPC_RMID, nothing to do */
2390                if (!ipc_valid_object(&sma->sem_perm)) {
2391                        sem_unlock(sma, -1);
2392                        rcu_read_unlock();
2393                        continue;
2394                }
2395                un = __lookup_undo(ulp, semid);
2396                if (un == NULL) {
2397                        /* exit_sem raced with IPC_RMID+semget() that created
2398                         * exactly the same semid. Nothing to do.
2399                         */
2400                        sem_unlock(sma, -1);
2401                        rcu_read_unlock();
2402                        continue;
2403                }
2404
2405                /* remove un from the linked lists */
2406                ipc_assert_locked_object(&sma->sem_perm);
2407                list_del(&un->list_id);
2408
2409                spin_lock(&ulp->lock);
2410                list_del_rcu(&un->list_proc);
2411                spin_unlock(&ulp->lock);
2412
2413                /* perform adjustments registered in un */
2414                for (i = 0; i < sma->sem_nsems; i++) {
2415                        struct sem *semaphore = &sma->sems[i];
2416                        if (un->semadj[i]) {
2417                                semaphore->semval += un->semadj[i];
2418                                /*
2419                                 * Range checks of the new semaphore value,
2420                                 * not defined by sus:
2421                                 * - Some unices ignore the undo entirely
2422                                 *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
2423                                 * - some cap the value (e.g. FreeBSD caps
2424                                 *   at 0, but doesn't enforce SEMVMX)
2425                                 *
2426                                 * Linux caps the semaphore value, both at 0
2427                                 * and at SEMVMX.
2428                                 *
2429                                 *      Manfred <manfred@colorfullife.com>
2430                                 */
2431                                if (semaphore->semval < 0)
2432                                        semaphore->semval = 0;
2433                                if (semaphore->semval > SEMVMX)
2434                                        semaphore->semval = SEMVMX;
2435                                ipc_update_pid(&semaphore->sempid, task_tgid(current));
2436                        }
2437                }
2438                /* maybe some queued-up processes were waiting for this */
2439                do_smart_update(sma, NULL, 0, 1, &wake_q);
2440                sem_unlock(sma, -1);
2441                rcu_read_unlock();
2442                wake_up_q(&wake_q);
2443
2444                kvfree_rcu(un, rcu);
2445        }
2446        kfree(ulp);
2447}
2448
2449#ifdef CONFIG_PROC_FS
2450static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
2451{
2452        struct user_namespace *user_ns = seq_user_ns(s);
2453        struct kern_ipc_perm *ipcp = it;
2454        struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
2455        time64_t sem_otime;
2456
2457        /*
2458         * The proc interface isn't aware of sem_lock(), it calls
2459         * ipc_lock_object(), i.e. spin_lock(&sma->sem_perm.lock).
2460         * (in sysvipc_find_ipc)
2461         * In order to stay compatible with sem_lock(), we must
2462         * enter / leave complex_mode.
2463         */
2464        complexmode_enter(sma);
2465
2466        sem_otime = get_semotime(sma);
2467
2468        seq_printf(s,
2469                   "%10d %10d  %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
2470                   sma->sem_perm.key,
2471                   sma->sem_perm.id,
2472                   sma->sem_perm.mode,
2473                   sma->sem_nsems,
2474                   from_kuid_munged(user_ns, sma->sem_perm.uid),
2475                   from_kgid_munged(user_ns, sma->sem_perm.gid),
2476                   from_kuid_munged(user_ns, sma->sem_perm.cuid),
2477                   from_kgid_munged(user_ns, sma->sem_perm.cgid),
2478                   sem_otime,
2479                   sma->sem_ctime);
2480
2481        complexmode_tryleave(sma);
2482
2483        return 0;
2484}
2485#endif
2486