TOMOYO Linux Cross Reference
Linux/ipc/sem.c

   // SPDX-License-Identifier: GPL-2.0
   /*
    * linux/ipc/sem.c
    * Copyright (C) 1992 Krishna Balasubramanian
    * Copyright (C) 1995 Eric Schenk, Bruno Haible
    *
    * /proc/sysvipc/sem support (c) 1999 Dragos Acostachioaie <dragos@iname.com>
    *
    * SMP-threaded, sysctl's added
   * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
   * Enforced range limit on SEM_UNDO
   * (c) 2001 Red Hat Inc
   * Lockless wakeup
   * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
   * (c) 2016 Davidlohr Bueso <dave@stgolabs.net>
   * Further wakeup optimizations, documentation
   * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
   *
   * support for audit of ipc object properties and permission changes
   * Dustin Kirkland <dustin.kirkland@us.ibm.com>
   *
   * namespaces support
   * OpenVZ, SWsoft Inc.
   * Pavel Emelianov <xemul@openvz.org>
   *
   * Implementation notes: (May 2010)
   * This file implements System V semaphores.
   *
   * User space visible behavior:
   * - FIFO ordering for semop() operations (just FIFO, not starvation
   *   protection)
   * - multiple semaphore operations that alter the same semaphore in
   *   one semop() are handled.
   * - sem_ctime (time of last semctl()) is updated in the IPC_SET, SETVAL and
   *   SETALL calls.
   * - two Linux specific semctl() commands: SEM_STAT, SEM_INFO.
   * - undo adjustments at process exit are limited to 0..SEMVMX.
   * - namespace are supported.
   * - SEMMSL, SEMMNS, SEMOPM and SEMMNI can be configured at runtime by writing
   *   to /proc/sys/kernel/sem.
   * - statistics about the usage are reported in /proc/sysvipc/sem.
   *
   * Internals:
   * - scalability:
   *   - all global variables are read-mostly.
   *   - semop() calls and semctl(RMID) are synchronized by RCU.
   *   - most operations do write operations (actually: spin_lock calls) to
   *     the per-semaphore array structure.
   *   Thus: Perfect SMP scaling between independent semaphore arrays.
   *         If multiple semaphores in one array are used, then cache line
   *         trashing on the semaphore array spinlock will limit the scaling.
   * - semncnt and semzcnt are calculated on demand in count_semcnt()
   * - the task that performs a successful semop() scans the list of all
   *   sleeping tasks and completes any pending operations that can be fulfilled.
   *   Semaphores are actively given to waiting tasks (necessary for FIFO).
   *   (see update_queue())
   * - To improve the scalability, the actual wake-up calls are performed after
   *   dropping all locks. (see wake_up_sem_queue_prepare())
   * - All work is done by the waker, the woken up task does not have to do
   *   anything - not even acquiring a lock or dropping a refcount.
   * - A woken up task may not even touch the semaphore array anymore, it may
   *   have been destroyed already by a semctl(RMID).
   * - UNDO values are stored in an array (one per process and per
   *   semaphore array, lazily allocated). For backwards compatibility, multiple
   *   modes for the UNDO variables are supported (per process, per thread)
   *   (see copy_semundo, CLONE_SYSVSEM)
   * - There are two lists of the pending operations: a per-array list
   *   and per-semaphore list (stored in the array). This allows to achieve FIFO
   *   ordering without always scanning all pending operations.
   *   The worst-case behavior is nevertheless O(N^2) for N wakeups.
   */
  
  #include <linux/compat.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/init.h>
  #include <linux/proc_fs.h>
  #include <linux/time.h>
  #include <linux/security.h>
  #include <linux/syscalls.h>
  #include <linux/audit.h>
  #include <linux/capability.h>
  #include <linux/seq_file.h>
  #include <linux/rwsem.h>
  #include <linux/nsproxy.h>
  #include <linux/ipc_namespace.h>
  #include <linux/sched/wake_q.h>
  #include <linux/nospec.h>
  #include <linux/rhashtable.h>
  
  #include <linux/uaccess.h>
  #include "util.h"
  
  /* One semaphore structure for each semaphore in the system. */
  struct sem {
          int     semval;         /* current value */
          /*
           * PID of the process that last modified the semaphore. For
           * Linux, specifically these are:
          *  - semop
          *  - semctl, via SETVAL and SETALL.
          *  - at task exit when performing undo adjustments (see exit_sem).
          */
         struct pid *sempid;
         spinlock_t      lock;   /* spinlock for fine-grained semtimedop */
         struct list_head pending_alter; /* pending single-sop operations */
                                         /* that alter the semaphore */
         struct list_head pending_const; /* pending single-sop operations */
                                         /* that do not alter the semaphore*/
         time64_t         sem_otime;     /* candidate for sem_otime */
 } ____cacheline_aligned_in_smp;
 
 /* One sem_array data structure for each set of semaphores in the system. */
 struct sem_array {
         struct kern_ipc_perm    sem_perm;       /* permissions .. see ipc.h */
         time64_t                sem_ctime;      /* create/last semctl() time */
         struct list_head        pending_alter;  /* pending operations */
                                                 /* that alter the array */
         struct list_head        pending_const;  /* pending complex operations */
                                                 /* that do not alter semvals */
         struct list_head        list_id;        /* undo requests on this array */
         int                     sem_nsems;      /* no. of semaphores in array */
         int                     complex_count;  /* pending complex operations */
         unsigned int            use_global_lock;/* >0: global lock required */
 
         struct sem              sems[];
 } __randomize_layout;
 
 /* One queue for each sleeping process in the system. */
 struct sem_queue {
         struct list_head        list;    /* queue of pending operations */
         struct task_struct      *sleeper; /* this process */
         struct sem_undo         *undo;   /* undo structure */
         struct pid              *pid;    /* process id of requesting process */
         int                     status;  /* completion status of operation */
         struct sembuf           *sops;   /* array of pending operations */
         struct sembuf           *blocking; /* the operation that blocked */
         int                     nsops;   /* number of operations */
         bool                    alter;   /* does *sops alter the array? */
         bool                    dupsop;  /* sops on more than one sem_num */
 };
 
 /* Each task has a list of undo requests. They are executed automatically
  * when the process exits.
  */
 struct sem_undo {
         struct list_head        list_proc;      /* per-process list: *
                                                  * all undos from one process
                                                  * rcu protected */
         struct rcu_head         rcu;            /* rcu struct for sem_undo */
         struct sem_undo_list    *ulp;           /* back ptr to sem_undo_list */
         struct list_head        list_id;        /* per semaphore array list:
                                                  * all undos for one array */
         int                     semid;          /* semaphore set identifier */
         short                   semadj[];       /* array of adjustments */
                                                 /* one per semaphore */
 };
 
 /* sem_undo_list controls shared access to the list of sem_undo structures
  * that may be shared among all a CLONE_SYSVSEM task group.
  */
 struct sem_undo_list {
         refcount_t              refcnt;
         spinlock_t              lock;
         struct list_head        list_proc;
 };
 
 
 #define sem_ids(ns)     ((ns)->ids[IPC_SEM_IDS])
 
 static int newary(struct ipc_namespace *, struct ipc_params *);
 static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
 #ifdef CONFIG_PROC_FS
 static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
 #endif
 
 #define SEMMSL_FAST     256 /* 512 bytes on stack */
 #define SEMOPM_FAST     64  /* ~ 372 bytes on stack */
 
 /*
  * Switching from the mode suitable for simple ops
  * to the mode for complex ops is costly. Therefore:
  * use some hysteresis
  */
 #define USE_GLOBAL_LOCK_HYSTERESIS      10
 
 /*
  * Locking:
  * a) global sem_lock() for read/write
  *      sem_undo.id_next,
  *      sem_array.complex_count,
  *      sem_array.pending{_alter,_const},
  *      sem_array.sem_undo
  *
  * b) global or semaphore sem_lock() for read/write:
  *      sem_array.sems[i].pending_{const,alter}:
  *
  * c) special:
  *      sem_undo_list.list_proc:
  *      * undo_list->lock for write
  *      * rcu for read
  *      use_global_lock:
  *      * global sem_lock() for write
  *      * either local or global sem_lock() for read.
  *
  * Memory ordering:
  * Most ordering is enforced by using spin_lock() and spin_unlock().
  *
  * Exceptions:
  * 1) use_global_lock: (SEM_BARRIER_1)
  * Setting it from non-zero to 0 is a RELEASE, this is ensured by
  * using smp_store_release(): Immediately after setting it to 0,
  * a simple op can start.
  * Testing if it is non-zero is an ACQUIRE, this is ensured by using
  * smp_load_acquire().
  * Setting it from 0 to non-zero must be ordered with regards to
  * this smp_load_acquire(), this is guaranteed because the smp_load_acquire()
  * is inside a spin_lock() and after a write from 0 to non-zero a
  * spin_lock()+spin_unlock() is done.
  * To prevent the compiler/cpu temporarily writing 0 to use_global_lock,
  * READ_ONCE()/WRITE_ONCE() is used.
  *
  * 2) queue.status: (SEM_BARRIER_2)
  * Initialization is done while holding sem_lock(), so no further barrier is
  * required.
  * Setting it to a result code is a RELEASE, this is ensured by both a
  * smp_store_release() (for case a) and while holding sem_lock()
  * (for case b).
  * The ACQUIRE when reading the result code without holding sem_lock() is
  * achieved by using READ_ONCE() + smp_acquire__after_ctrl_dep().
  * (case a above).
  * Reading the result code while holding sem_lock() needs no further barriers,
  * the locks inside sem_lock() enforce ordering (case b above)
  *
  * 3) current->state:
  * current->state is set to TASK_INTERRUPTIBLE while holding sem_lock().
  * The wakeup is handled using the wake_q infrastructure. wake_q wakeups may
  * happen immediately after calling wake_q_add. As wake_q_add_safe() is called
  * when holding sem_lock(), no further barriers are required.
  *
  * See also ipc/mqueue.c for more details on the covered races.
  */
 
 #define sc_semmsl       sem_ctls[0]
 #define sc_semmns       sem_ctls[1]
 #define sc_semopm       sem_ctls[2]
 #define sc_semmni       sem_ctls[3]
 
 void sem_init_ns(struct ipc_namespace *ns)
 {
         ns->sc_semmsl = SEMMSL;
         ns->sc_semmns = SEMMNS;
         ns->sc_semopm = SEMOPM;
         ns->sc_semmni = SEMMNI;
         ns->used_sems = 0;
         ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
 }
 
 #ifdef CONFIG_IPC_NS
 void sem_exit_ns(struct ipc_namespace *ns)
 {
         free_ipcs(ns, &sem_ids(ns), freeary);
         idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
         rhashtable_destroy(&ns->ids[IPC_SEM_IDS].key_ht);
 }
 #endif
 
 void __init sem_init(void)
 {
         sem_init_ns(&init_ipc_ns);
         ipc_init_proc_interface("sysvipc/sem",
                                 "       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
                                 IPC_SEM_IDS, sysvipc_sem_proc_show);
 }
 
 /**
  * unmerge_queues - unmerge queues, if possible.
  * @sma: semaphore array
  *
  * The function unmerges the wait queues if complex_count is 0.
  * It must be called prior to dropping the global semaphore array lock.
  */
 static void unmerge_queues(struct sem_array *sma)
 {
         struct sem_queue *q, *tq;
 
         /* complex operations still around? */
         if (sma->complex_count)
                 return;
         /*
          * We will switch back to simple mode.
          * Move all pending operation back into the per-semaphore
          * queues.
          */
         list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
                 struct sem *curr;
                 curr = &sma->sems[q->sops[0].sem_num];
 
                 list_add_tail(&q->list, &curr->pending_alter);
         }
         INIT_LIST_HEAD(&sma->pending_alter);
 }
 
 /**
  * merge_queues - merge single semop queues into global queue
  * @sma: semaphore array
  *
  * This function merges all per-semaphore queues into the global queue.
  * It is necessary to achieve FIFO ordering for the pending single-sop
  * operations when a multi-semop operation must sleep.
  * Only the alter operations must be moved, the const operations can stay.
  */
 static void merge_queues(struct sem_array *sma)
 {
         int i;
         for (i = 0; i < sma->sem_nsems; i++) {
                 struct sem *sem = &sma->sems[i];
 
                 list_splice_init(&sem->pending_alter, &sma->pending_alter);
         }
 }
 
 static void sem_rcu_free(struct rcu_head *head)
 {
         struct kern_ipc_perm *p = container_of(head, struct kern_ipc_perm, rcu);
         struct sem_array *sma = container_of(p, struct sem_array, sem_perm);
 
         security_sem_free(&sma->sem_perm);
         kvfree(sma);
 }
 
 /*
  * Enter the mode suitable for non-simple operations:
  * Caller must own sem_perm.lock.
  */
 static void complexmode_enter(struct sem_array *sma)
 {
         int i;
         struct sem *sem;
 
         if (sma->use_global_lock > 0)  {
                 /*
                  * We are already in global lock mode.
                  * Nothing to do, just reset the
                  * counter until we return to simple mode.
                  */
                 WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS);
                 return;
         }
         WRITE_ONCE(sma->use_global_lock, USE_GLOBAL_LOCK_HYSTERESIS);
 
         for (i = 0; i < sma->sem_nsems; i++) {
                 sem = &sma->sems[i];
                 spin_lock(&sem->lock);
                 spin_unlock(&sem->lock);
         }
 }
 
 /*
  * Try to leave the mode that disallows simple operations:
  * Caller must own sem_perm.lock.
  */
 static void complexmode_tryleave(struct sem_array *sma)
 {
         if (sma->complex_count)  {
                 /* Complex ops are sleeping.
                  * We must stay in complex mode
                  */
                 return;
         }
         if (sma->use_global_lock == 1) {
 
                 /* See SEM_BARRIER_1 for purpose/pairing */
                 smp_store_release(&sma->use_global_lock, 0);
         } else {
                 WRITE_ONCE(sma->use_global_lock,
                                 sma->use_global_lock-1);
         }
 }
 
 #define SEM_GLOBAL_LOCK (-1)
 /*
  * If the request contains only one semaphore operation, and there are
  * no complex transactions pending, lock only the semaphore involved.
  * Otherwise, lock the entire semaphore array, since we either have
  * multiple semaphores in our own semops, or we need to look at
  * semaphores from other pending complex operations.
  */
 static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
                               int nsops)
 {
         struct sem *sem;
         int idx;
 
         if (nsops != 1) {
                 /* Complex operation - acquire a full lock */
                 ipc_lock_object(&sma->sem_perm);
 
                 /* Prevent parallel simple ops */
                 complexmode_enter(sma);
                 return SEM_GLOBAL_LOCK;
         }
 
         /*
          * Only one semaphore affected - try to optimize locking.
          * Optimized locking is possible if no complex operation
          * is either enqueued or processed right now.
          *
          * Both facts are tracked by use_global_mode.
          */
         idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
         sem = &sma->sems[idx];
 
         /*
          * Initial check for use_global_lock. Just an optimization,
          * no locking, no memory barrier.
          */
         if (!READ_ONCE(sma->use_global_lock)) {
                 /*
                  * It appears that no complex operation is around.
                  * Acquire the per-semaphore lock.
                  */
                 spin_lock(&sem->lock);
 
                 /* see SEM_BARRIER_1 for purpose/pairing */
                 if (!smp_load_acquire(&sma->use_global_lock)) {
                         /* fast path successful! */
                         return sops->sem_num;
                 }
                 spin_unlock(&sem->lock);
         }
 
         /* slow path: acquire the full lock */
         ipc_lock_object(&sma->sem_perm);
 
         if (sma->use_global_lock == 0) {
                 /*
                  * The use_global_lock mode ended while we waited for
                  * sma->sem_perm.lock. Thus we must switch to locking
                  * with sem->lock.
                  * Unlike in the fast path, there is no need to recheck
                  * sma->use_global_lock after we have acquired sem->lock:
                  * We own sma->sem_perm.lock, thus use_global_lock cannot
                  * change.
                  */
                 spin_lock(&sem->lock);
 
                 ipc_unlock_object(&sma->sem_perm);
                 return sops->sem_num;
         } else {
                 /*
                  * Not a false alarm, thus continue to use the global lock
                  * mode. No need for complexmode_enter(), this was done by
                  * the caller that has set use_global_mode to non-zero.
                  */
                 return SEM_GLOBAL_LOCK;
         }
 }
 
 static inline void sem_unlock(struct sem_array *sma, int locknum)
 {
         if (locknum == SEM_GLOBAL_LOCK) {
                 unmerge_queues(sma);
                 complexmode_tryleave(sma);
                 ipc_unlock_object(&sma->sem_perm);
         } else {
                 struct sem *sem = &sma->sems[locknum];
                 spin_unlock(&sem->lock);
         }
 }
 
 /*
  * sem_lock_(check_) routines are called in the paths where the rwsem
  * is not held.
  *
  * The caller holds the RCU read lock.
  */
 static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
 {
         struct kern_ipc_perm *ipcp = ipc_obtain_object_idr(&sem_ids(ns), id);
 
         if (IS_ERR(ipcp))
                 return ERR_CAST(ipcp);
 
         return container_of(ipcp, struct sem_array, sem_perm);
 }
 
 static inline struct sem_array *sem_obtain_object_check(struct ipc_namespace *ns,
                                                         int id)
 {
         struct kern_ipc_perm *ipcp = ipc_obtain_object_check(&sem_ids(ns), id);
 
         if (IS_ERR(ipcp))
                 return ERR_CAST(ipcp);
 
         return container_of(ipcp, struct sem_array, sem_perm);
 }
 
 static inline void sem_lock_and_putref(struct sem_array *sma)
 {
         sem_lock(sma, NULL, -1);
         ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 }
 
 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
 {
         ipc_rmid(&sem_ids(ns), &s->sem_perm);
 }
 
 static struct sem_array *sem_alloc(size_t nsems)
 {
         struct sem_array *sma;
 
         if (nsems > (INT_MAX - sizeof(*sma)) / sizeof(sma->sems[0]))
                 return NULL;
 
         sma = kvzalloc(struct_size(sma, sems, nsems), GFP_KERNEL_ACCOUNT);
         if (unlikely(!sma))
                 return NULL;
 
         return sma;
 }
 
 /**
  * newary - Create a new semaphore set
  * @ns: namespace
  * @params: ptr to the structure that contains key, semflg and nsems
  *
  * Called with sem_ids.rwsem held (as a writer)
  */
 static int newary(struct ipc_namespace *ns, struct ipc_params *params)
 {
         int retval;
         struct sem_array *sma;
         key_t key = params->key;
         int nsems = params->u.nsems;
         int semflg = params->flg;
         int i;
 
         if (!nsems)
                 return -EINVAL;
         if (ns->used_sems + nsems > ns->sc_semmns)
                 return -ENOSPC;
 
         sma = sem_alloc(nsems);
         if (!sma)
                 return -ENOMEM;
 
         sma->sem_perm.mode = (semflg & S_IRWXUGO);
         sma->sem_perm.key = key;
 
         sma->sem_perm.security = NULL;
         retval = security_sem_alloc(&sma->sem_perm);
         if (retval) {
                 kvfree(sma);
                 return retval;
         }
 
         for (i = 0; i < nsems; i++) {
                 INIT_LIST_HEAD(&sma->sems[i].pending_alter);
                 INIT_LIST_HEAD(&sma->sems[i].pending_const);
                 spin_lock_init(&sma->sems[i].lock);
         }
 
         sma->complex_count = 0;
         sma->use_global_lock = USE_GLOBAL_LOCK_HYSTERESIS;
         INIT_LIST_HEAD(&sma->pending_alter);
         INIT_LIST_HEAD(&sma->pending_const);
         INIT_LIST_HEAD(&sma->list_id);
         sma->sem_nsems = nsems;
         sma->sem_ctime = ktime_get_real_seconds();
 
         /* ipc_addid() locks sma upon success. */
         retval = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
         if (retval < 0) {
                 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
                 return retval;
         }
         ns->used_sems += nsems;
 
         sem_unlock(sma, -1);
         rcu_read_unlock();
 
         return sma->sem_perm.id;
 }
 
 
 /*
  * Called with sem_ids.rwsem and ipcp locked.
  */
 static int sem_more_checks(struct kern_ipc_perm *ipcp, struct ipc_params *params)
 {
         struct sem_array *sma;
 
         sma = container_of(ipcp, struct sem_array, sem_perm);
         if (params->u.nsems > sma->sem_nsems)
                 return -EINVAL;
 
         return 0;
 }
 
 long ksys_semget(key_t key, int nsems, int semflg)
 {
         struct ipc_namespace *ns;
         static const struct ipc_ops sem_ops = {
                 .getnew = newary,
                 .associate = security_sem_associate,
                 .more_checks = sem_more_checks,
         };
         struct ipc_params sem_params;
 
         ns = current->nsproxy->ipc_ns;
 
         if (nsems < 0 || nsems > ns->sc_semmsl)
                 return -EINVAL;
 
         sem_params.key = key;
         sem_params.flg = semflg;
         sem_params.u.nsems = nsems;
 
         return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
 }
 
 SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
 {
         return ksys_semget(key, nsems, semflg);
 }
 
 /**
  * perform_atomic_semop[_slow] - Attempt to perform semaphore
  *                               operations on a given array.
  * @sma: semaphore array
  * @q: struct sem_queue that describes the operation
  *
  * Caller blocking are as follows, based the value
  * indicated by the semaphore operation (sem_op):
  *
  *  (1) >0 never blocks.
  *  (2)  0 (wait-for-zero operation): semval is non-zero.
  *  (3) <0 attempting to decrement semval to a value smaller than zero.
  *
  * Returns 0 if the operation was possible.
  * Returns 1 if the operation is impossible, the caller must sleep.
  * Returns <0 for error codes.
  */
 static int perform_atomic_semop_slow(struct sem_array *sma, struct sem_queue *q)
 {
         int result, sem_op, nsops;
         struct pid *pid;
         struct sembuf *sop;
         struct sem *curr;
         struct sembuf *sops;
         struct sem_undo *un;
 
         sops = q->sops;
         nsops = q->nsops;
         un = q->undo;
 
         for (sop = sops; sop < sops + nsops; sop++) {
                 int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
                 curr = &sma->sems[idx];
                 sem_op = sop->sem_op;
                 result = curr->semval;
 
                 if (!sem_op && result)
                         goto would_block;
 
                 result += sem_op;
                 if (result < 0)
                         goto would_block;
                 if (result > SEMVMX)
                         goto out_of_range;
 
                 if (sop->sem_flg & SEM_UNDO) {
                         int undo = un->semadj[sop->sem_num] - sem_op;
                         /* Exceeding the undo range is an error. */
                         if (undo < (-SEMAEM - 1) || undo > SEMAEM)
                                 goto out_of_range;
                         un->semadj[sop->sem_num] = undo;
                 }
 
                 curr->semval = result;
         }
 
         sop--;
         pid = q->pid;
         while (sop >= sops) {
                 ipc_update_pid(&sma->sems[sop->sem_num].sempid, pid);
                 sop--;
         }
 
         return 0;
 
 out_of_range:
         result = -ERANGE;
         goto undo;
 
 would_block:
         q->blocking = sop;
 
         if (sop->sem_flg & IPC_NOWAIT)
                 result = -EAGAIN;
         else
                 result = 1;
 
 undo:
         sop--;
         while (sop >= sops) {
                 sem_op = sop->sem_op;
                 sma->sems[sop->sem_num].semval -= sem_op;
                 if (sop->sem_flg & SEM_UNDO)
                         un->semadj[sop->sem_num] += sem_op;
                 sop--;
         }
 
         return result;
 }
 
 static int perform_atomic_semop(struct sem_array *sma, struct sem_queue *q)
 {
         int result, sem_op, nsops;
         struct sembuf *sop;
         struct sem *curr;
         struct sembuf *sops;
         struct sem_undo *un;
 
         sops = q->sops;
         nsops = q->nsops;
         un = q->undo;
 
         if (unlikely(q->dupsop))
                 return perform_atomic_semop_slow(sma, q);
 
         /*
          * We scan the semaphore set twice, first to ensure that the entire
          * operation can succeed, therefore avoiding any pointless writes
          * to shared memory and having to undo such changes in order to block
          * until the operations can go through.
          */
         for (sop = sops; sop < sops + nsops; sop++) {
                 int idx = array_index_nospec(sop->sem_num, sma->sem_nsems);
 
                 curr = &sma->sems[idx];
                 sem_op = sop->sem_op;
                 result = curr->semval;
 
                 if (!sem_op && result)
                         goto would_block; /* wait-for-zero */
 
                 result += sem_op;
                 if (result < 0)
                         goto would_block;
 
                 if (result > SEMVMX)
                         return -ERANGE;
 
                 if (sop->sem_flg & SEM_UNDO) {
                         int undo = un->semadj[sop->sem_num] - sem_op;
 
                         /* Exceeding the undo range is an error. */
                         if (undo < (-SEMAEM - 1) || undo > SEMAEM)
                                 return -ERANGE;
                 }
         }
 
         for (sop = sops; sop < sops + nsops; sop++) {
                 curr = &sma->sems[sop->sem_num];
                 sem_op = sop->sem_op;
 
                 if (sop->sem_flg & SEM_UNDO) {
                         int undo = un->semadj[sop->sem_num] - sem_op;
 
                         un->semadj[sop->sem_num] = undo;
                 }
                 curr->semval += sem_op;
                 ipc_update_pid(&curr->sempid, q->pid);
         }
 
         return 0;
 
 would_block:
         q->blocking = sop;
         return sop->sem_flg & IPC_NOWAIT ? -EAGAIN : 1;
 }
 
 static inline void wake_up_sem_queue_prepare(struct sem_queue *q, int error,
                                              struct wake_q_head *wake_q)
 {
         struct task_struct *sleeper;
 
         sleeper = get_task_struct(q->sleeper);
 
         /* see SEM_BARRIER_2 for purpose/pairing */
         smp_store_release(&q->status, error);
 
         wake_q_add_safe(wake_q, sleeper);
 }
 
 static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
 {
         list_del(&q->list);
         if (q->nsops > 1)
                 sma->complex_count--;
 }
 
 /** check_restart(sma, q)
  * @sma: semaphore array
  * @q: the operation that just completed
  *
  * update_queue is O(N^2) when it restarts scanning the whole queue of
  * waiting operations. Therefore this function checks if the restart is
  * really necessary. It is called after a previously waiting operation
  * modified the array.
  * Note that wait-for-zero operations are handled without restart.
  */
 static inline int check_restart(struct sem_array *sma, struct sem_queue *q)
 {
         /* pending complex alter operations are too difficult to analyse */
         if (!list_empty(&sma->pending_alter))
                 return 1;
 
         /* we were a sleeping complex operation. Too difficult */
         if (q->nsops > 1)
                 return 1;
 
         /* It is impossible that someone waits for the new value:
          * - complex operations always restart.
          * - wait-for-zero are handled separately.
          * - q is a previously sleeping simple operation that
          *   altered the array. It must be a decrement, because
          *   simple increments never sleep.
          * - If there are older (higher priority) decrements
          *   in the queue, then they have observed the original
          *   semval value and couldn't proceed. The operation
          *   decremented to value - thus they won't proceed either.
          */
         return 0;
 }
 
 /**
  * wake_const_ops - wake up non-alter tasks
  * @sma: semaphore array.
  * @semnum: semaphore that was modified.
  * @wake_q: lockless wake-queue head.
  *
  * wake_const_ops must be called after a semaphore in a semaphore array
  * was set to 0. If complex const operations are pending, wake_const_ops must
  * be called with semnum = -1, as well as with the number of each modified
  * semaphore.
  * The tasks that must be woken up are added to @wake_q. The return code
  * is stored in q->pid.
  * The function returns 1 if at least one operation was completed successfully.
  */
 static int wake_const_ops(struct sem_array *sma, int semnum,
                           struct wake_q_head *wake_q)
 {
         struct sem_queue *q, *tmp;
         struct list_head *pending_list;
         int semop_completed = 0;
 
         if (semnum == -1)
                 pending_list = &sma->pending_const;
         else
                 pending_list = &sma->sems[semnum].pending_const;
 
         list_for_each_entry_safe(q, tmp, pending_list, list) {
                 int error = perform_atomic_semop(sma, q);
 
                 if (error > 0)
                         continue;
                 /* operation completed, remove from queue & wakeup */
                 unlink_queue(sma, q);
 
                 wake_up_sem_queue_prepare(q, error, wake_q);
                 if (error == 0)
                         semop_completed = 1;
         }
 
         return semop_completed;
 }
 
 /**
  * do_smart_wakeup_zero - wakeup all wait for zero tasks
  * @sma: semaphore array
  * @sops: operations that were performed
  * @nsops: number of operations
  * @wake_q: lockless wake-queue head
  *
  * Checks all required queue for wait-for-zero operations, based
  * on the actual changes that were performed on the semaphore array.
  * The function returns 1 if at least one operation was completed successfully.
  */
 static int do_smart_wakeup_zero(struct sem_array *sma, struct sembuf *sops,
                                 int nsops, struct wake_q_head *wake_q)
 {
         int i;
         int semop_completed = 0;
         int got_zero = 0;
 
         /* first: the per-semaphore queues, if known */
         if (sops) {
                 for (i = 0; i < nsops; i++) {
                         int num = sops[i].sem_num;
 
                         if (sma->sems[num].semval == 0) {
                                 got_zero = 1;
                                 semop_completed |= wake_const_ops(sma, num, wake_q);
                         }
                 }
         } else {
                 /*
                  * No sops means modified semaphores not known.
                  * Assume all were changed.
                  */
                 for (i = 0; i < sma->sem_nsems; i++) {
                         if (sma->sems[i].semval == 0) {
                                 got_zero = 1;
                                 semop_completed |= wake_const_ops(sma, i, wake_q);
                         }
                 }
         }
         /*
          * If one of the modified semaphores got 0,
          * then check the global queue, too.
          */
         if (got_zero)
                 semop_completed |= wake_const_ops(sma, -1, wake_q);
 
         return semop_completed;
 }
 
 
 /**
  * update_queue - look for tasks that can be completed.
  * @sma: semaphore array.
  * @semnum: semaphore that was modified.
  * @wake_q: lockless wake-queue head.
  *
  * update_queue must be called after a semaphore in a semaphore array
  * was modified. If multiple semaphores were modified, update_queue must
  * be called with semnum = -1, as well as with the number of each modified
  * semaphore.
  * The tasks that must be woken up are added to @wake_q. The return code
  * is stored in q->pid.
  * The function internally checks if const operations can now succeed.
  *
  * The function return 1 if at least one semop was completed successfully.
  */
 static int update_queue(struct sem_array *sma, int semnum, struct wake_q_head *wake_q)
 {
         struct sem_queue *q, *tmp;
         struct list_head *pending_list;
         int semop_completed = 0;
 
         if (semnum == -1)
                 pending_list = &sma->pending_alter;
         else
                 pending_list = &sma->sems[semnum].pending_alter;
 
 again:
         list_for_each_entry_safe(q, tmp, pending_list, list) {
                 int error, restart;
 
                 /* If we are scanning the single sop, per-semaphore list of
                  * one semaphore and that semaphore is 0, then it is not
                  * necessary to scan further: simple increments
                  * that affect only one entry succeed immediately and cannot
                  * be in the  per semaphore pending queue, and decrements
                  * cannot be successful if the value is already 0.
                  */
                 if (semnum != -1 && sma->sems[semnum].semval == 0)
                         break;
 
                 error = perform_atomic_semop(sma, q);
 
                 /* Does q->sleeper still need to sleep? */
                 if (error > 0)
                         continue;
 
                 unlink_queue(sma, q);
 
                 if (error) {
                         restart = 0;
                 } else {
                         semop_completed = 1;
                         do_smart_wakeup_zero(sma, q->sops, q->nsops, wake_q);
                         restart = check_restart(sma, q);
                 }
 
                 wake_up_sem_queue_prepare(q, error, wake_q);
                 if (restart)
                         goto again;
         }
         return semop_completed;
 }
 
 /**
  * set_semotime - set sem_otime
  * @sma: semaphore array
  * @sops: operations that modified the array, may be NULL
  *
  * sem_otime is replicated to avoid cache line trashing.
  * This function sets one instance to the current time.
  */
 static void set_semotime(struct sem_array *sma, struct sembuf *sops)
 {
         if (sops == NULL) {
                 sma->sems[0].sem_otime = ktime_get_real_seconds();
         } else {
                 sma->sems[sops[0].sem_num].sem_otime =
                                                 ktime_get_real_seconds();
         }
 }
 
 /**
  * do_smart_update - optimized update_queue
  * @sma: semaphore array
  * @sops: operations that were performed
  * @nsops: number of operations
  * @otime: force setting otime
  * @wake_q: lockless wake-queue head
  *
  * do_smart_update() does the required calls to update_queue and wakeup_zero,
  * based on the actual changes that were performed on the semaphore array.
  * Note that the function does not do the actual wake-up: the caller is
  * responsible for calling wake_up_q().
  * It is safe to perform this call after dropping all locks.
  */
 static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
                             int otime, struct wake_q_head *wake_q)
 {
         int i;
 
         otime |= do_smart_wakeup_zero(sma, sops, nsops, wake_q);
 
         if (!list_empty(&sma->pending_alter)) {
                 /* semaphore array uses the global queue - just process it. */
                 otime |= update_queue(sma, -1, wake_q);
         } else {
                 if (!sops) {
                         /*
                          * No sops, thus the modified semaphores are not
                          * known. Check all.
                          */
                         for (i = 0; i < sma->sem_nsems; i++)
                                 otime |= update_queue(sma, i, wake_q);
                 } else {
                         /*
                          * Check the semaphores that were increased:
                          * - No complex ops, thus all sleeping ops are
                          *   decrease.
                          * - if we decreased the value, then any sleeping
                          *   semaphore ops won't be able to run: If the
                          *   previous value was too small, then the new
                          *   value will be too small, too.
                          */
                         for (i = 0; i < nsops; i++) {
                                 if (sops[i].sem_op > 0) {
                                         otime |= update_queue(sma,
                                                               sops[i].sem_num, wake_q);
                                 }
                         }
                 }
         }
         if (otime)
                 set_semotime(sma, sops);
 }
 
 /*
  * check_qop: Test if a queued operation sleeps on the semaphore semnum
  */
 static int check_qop(struct sem_array *sma, int semnum, struct sem_queue *q,
                         bool count_zero)
 {
         struct sembuf *sop = q->blocking;
 
         /*
          * Linux always (since 0.99.10) reported a task as sleeping on all
          * semaphores. This violates SUS, therefore it was changed to the
          * standard compliant behavior.
          * Give the administrators a chance to notice that an application
          * might misbehave because it relies on the Linux behavior.
          */
         pr_info_once("semctl(GETNCNT/GETZCNT) is since 3.16 Single Unix Specification compliant.\n"
                         "The task %s (%d) triggered the difference, watch for misbehavior.\n",
                         current->comm, task_pid_nr(current));
 
         if (sop->sem_num != semnum)
                 return 0;
 
         if (count_zero && sop->sem_op == 0)
                 return 1;
         if (!count_zero && sop->sem_op < 0)
                 return 1;
 
         return 0;
 }
 
 /* The following counts are associated to each semaphore:
  *   semncnt        number of tasks waiting on semval being nonzero
  *   semzcnt        number of tasks waiting on semval being zero
  *
  * Per definition, a task waits only on the semaphore of the first semop
  * that cannot proceed, even if additional operation would block, too.
  */
 static int count_semcnt(struct sem_array *sma, ushort semnum,
                         bool count_zero)
 {
         struct list_head *l;
         struct sem_queue *q;
         int semcnt;
 
         semcnt = 0;
         /* First: check the simple operations. They are easy to evaluate */
         if (count_zero)
                 l = &sma->sems[semnum].pending_const;
         else
                 l = &sma->sems[semnum].pending_alter;
 
         list_for_each_entry(q, l, list) {
                 /* all task on a per-semaphore list sleep on exactly
                  * that semaphore
                  */
                 semcnt++;
         }
 
         /* Then: check the complex operations. */
         list_for_each_entry(q, &sma->pending_alter, list) {
                 semcnt += check_qop(sma, semnum, q, count_zero);
         }
         if (count_zero) {
                 list_for_each_entry(q, &sma->pending_const, list) {
                         semcnt += check_qop(sma, semnum, q, count_zero);
                 }
         }
         return semcnt;
 }
 
 /* Free a semaphore set. freeary() is called with sem_ids.rwsem locked
  * as a writer and the spinlock for this semaphore set hold. sem_ids.rwsem
  * remains locked on exit.
  */
 static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
 {
         struct sem_undo *un, *tu;
         struct sem_queue *q, *tq;
         struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
         int i;
         DEFINE_WAKE_Q(wake_q);
 
         /* Free the existing undo structures for this semaphore set.  */
         ipc_assert_locked_object(&sma->sem_perm);
         list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
                 list_del(&un->list_id);
                 spin_lock(&un->ulp->lock);
                 un->semid = -1;
                 list_del_rcu(&un->list_proc);
                 spin_unlock(&un->ulp->lock);
                 kvfree_rcu(un, rcu);
         }
 
         /* Wake up all pending processes and let them fail with EIDRM. */
         list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
                 unlink_queue(sma, q);
                 wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
         }
 
         list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
                 unlink_queue(sma, q);
                 wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
         }
         for (i = 0; i < sma->sem_nsems; i++) {
                 struct sem *sem = &sma->sems[i];
                 list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
                         unlink_queue(sma, q);
                         wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
                 }
                 list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
                         unlink_queue(sma, q);
                         wake_up_sem_queue_prepare(q, -EIDRM, &wake_q);
                 }
                 ipc_update_pid(&sem->sempid, NULL);
         }
 
         /* Remove the semaphore set from the IDR */
         sem_rmid(ns, sma);
         sem_unlock(sma, -1);
         rcu_read_unlock();
 
         wake_up_q(&wake_q);
         ns->used_sems -= sma->sem_nsems;
         ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
 }
 
 static unsigned long copy_semid_to_user(void __user *buf, struct semid64_ds *in, int version)
 {
         switch (version) {
         case IPC_64:
                 return copy_to_user(buf, in, sizeof(*in));
         case IPC_OLD:
             {
                 struct semid_ds out;
 
                 memset(&out, 0, sizeof(out));
 
                 ipc64_perm_to_ipc_perm(&in->sem_perm, &out.sem_perm);
 
                 out.sem_otime   = in->sem_otime;
                 out.sem_ctime   = in->sem_ctime;
                 out.sem_nsems   = in->sem_nsems;
 
                 return copy_to_user(buf, &out, sizeof(out));
             }
         default:
                 return -EINVAL;
         }
 }
 
 static time64_t get_semotime(struct sem_array *sma)
 {
         int i;
         time64_t res;
 
         res = sma->sems[0].sem_otime;
         for (i = 1; i < sma->sem_nsems; i++) {
                 time64_t to = sma->sems[i].sem_otime;
 
                 if (to > res)
                         res = to;
         }
         return res;
 }
 
 static int semctl_stat(struct ipc_namespace *ns, int semid,
                          int cmd, struct semid64_ds *semid64)
 {
         struct sem_array *sma;
         time64_t semotime;
         int err;
 
         memset(semid64, 0, sizeof(*semid64));
 
         rcu_read_lock();
         if (cmd == SEM_STAT || cmd == SEM_STAT_ANY) {
                 sma = sem_obtain_object(ns, semid);
                 if (IS_ERR(sma)) {
                         err = PTR_ERR(sma);
                         goto out_unlock;
                 }
         } else { /* IPC_STAT */
                 sma = sem_obtain_object_check(ns, semid);
                 if (IS_ERR(sma)) {
                         err = PTR_ERR(sma);
                         goto out_unlock;
                 }
         }
 
         /* see comment for SHM_STAT_ANY */
         if (cmd == SEM_STAT_ANY)
                 audit_ipc_obj(&sma->sem_perm);
         else {
                 err = -EACCES;
                 if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
                         goto out_unlock;
         }
 
         err = security_sem_semctl(&sma->sem_perm, cmd);
         if (err)
                 goto out_unlock;
 
         ipc_lock_object(&sma->sem_perm);
 
         if (!ipc_valid_object(&sma->sem_perm)) {
                 ipc_unlock_object(&sma->sem_perm);
                 err = -EIDRM;
                 goto out_unlock;
         }
 
         kernel_to_ipc64_perm(&sma->sem_perm, &semid64->sem_perm);
         semotime = get_semotime(sma);
         semid64->sem_otime = semotime;
         semid64->sem_ctime = sma->sem_ctime;
 #ifndef CONFIG_64BIT
         semid64->sem_otime_high = semotime >> 32;
         semid64->sem_ctime_high = sma->sem_ctime >> 32;
 #endif
         semid64->sem_nsems = sma->sem_nsems;
 
         if (cmd == IPC_STAT) {
                 /*
                  * As defined in SUS:
                  * Return 0 on success
                  */
                 err = 0;
         } else {
                 /*
                  * SEM_STAT and SEM_STAT_ANY (both Linux specific)
                  * Return the full id, including the sequence number
                  */
                 err = sma->sem_perm.id;
         }
         ipc_unlock_object(&sma->sem_perm);
 out_unlock:
         rcu_read_unlock();
         return err;
 }
 
 static int semctl_info(struct ipc_namespace *ns, int semid,
                          int cmd, void __user *p)
 {
         struct seminfo seminfo;
         int max_idx;
         int err;
 
         err = security_sem_semctl(NULL, cmd);
         if (err)
                 return err;
 
         memset(&seminfo, 0, sizeof(seminfo));
         seminfo.semmni = ns->sc_semmni;
         seminfo.semmns = ns->sc_semmns;
         seminfo.semmsl = ns->sc_semmsl;
         seminfo.semopm = ns->sc_semopm;
         seminfo.semvmx = SEMVMX;
         seminfo.semmnu = SEMMNU;
         seminfo.semmap = SEMMAP;
         seminfo.semume = SEMUME;
         down_read(&sem_ids(ns).rwsem);
         if (cmd == SEM_INFO) {
                 seminfo.semusz = sem_ids(ns).in_use;
                 seminfo.semaem = ns->used_sems;
         } else {
                 seminfo.semusz = SEMUSZ;
                 seminfo.semaem = SEMAEM;
         }
         max_idx = ipc_get_maxidx(&sem_ids(ns));
         up_read(&sem_ids(ns).rwsem);
         if (copy_to_user(p, &seminfo, sizeof(struct seminfo)))
                 return -EFAULT;
         return (max_idx < 0) ? 0 : max_idx;
 }
 
 static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
                 int val)
 {
         struct sem_undo *un;
         struct sem_array *sma;
         struct sem *curr;
         int err;
         DEFINE_WAKE_Q(wake_q);
 
         if (val > SEMVMX || val < 0)
                 return -ERANGE;
 
         rcu_read_lock();
         sma = sem_obtain_object_check(ns, semid);
         if (IS_ERR(sma)) {
                 rcu_read_unlock();
                 return PTR_ERR(sma);
         }
 
         if (semnum < 0 || semnum >= sma->sem_nsems) {
                 rcu_read_unlock();
                 return -EINVAL;
         }
 
 
         if (ipcperms(ns, &sma->sem_perm, S_IWUGO)) {
                 rcu_read_unlock();
                 return -EACCES;
         }
 
         err = security_sem_semctl(&sma->sem_perm, SETVAL);
         if (err) {
                 rcu_read_unlock();
                 return -EACCES;
         }
 
         sem_lock(sma, NULL, -1);
 
         if (!ipc_valid_object(&sma->sem_perm)) {
                 sem_unlock(sma, -1);
                 rcu_read_unlock();
                 return -EIDRM;
         }
 
         semnum = array_index_nospec(semnum, sma->sem_nsems);
         curr = &sma->sems[semnum];
 
         ipc_assert_locked_object(&sma->sem_perm);
         list_for_each_entry(un, &sma->list_id, list_id)
                 un->semadj[semnum] = 0;
 
         curr->semval = val;
         ipc_update_pid(&curr->sempid, task_tgid(current));
         sma->sem_ctime = ktime_get_real_seconds();
         /* maybe some queued-up processes were waiting for this */
         do_smart_update(sma, NULL, 0, 0, &wake_q);
         sem_unlock(sma, -1);
         rcu_read_unlock();
         wake_up_q(&wake_q);
         return 0;
 }
 
 static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
                 int cmd, void __user *p)
 {
         struct sem_array *sma;
         struct sem *curr;
         int err, nsems;
         ushort fast_sem_io[SEMMSL_FAST];
         ushort *sem_io = fast_sem_io;
         DEFINE_WAKE_Q(wake_q);
 
         rcu_read_lock();
         sma = sem_obtain_object_check(ns, semid);
         if (IS_ERR(sma)) {
                 rcu_read_unlock();
                 return PTR_ERR(sma);
         }
 
         nsems = sma->sem_nsems;
 
         err = -EACCES;
         if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
                 goto out_rcu_wakeup;
 
         err = security_sem_semctl(&sma->sem_perm, cmd);
         if (err)
                 goto out_rcu_wakeup;
 
         switch (cmd) {
         case GETALL:
         {
                 ushort __user *array = p;
                 int i;
 
                 sem_lock(sma, NULL, -1);
                 if (!ipc_valid_object(&sma->sem_perm)) {
                         err = -EIDRM;
                         goto out_unlock;
                 }
                 if (nsems > SEMMSL_FAST) {
                         if (!ipc_rcu_getref(&sma->sem_perm)) {
                                 err = -EIDRM;
                                 goto out_unlock;
                         }
                         sem_unlock(sma, -1);
                         rcu_read_unlock();
                         sem_io = kvmalloc_array(nsems, sizeof(ushort),
                                                 GFP_KERNEL);
                         if (sem_io == NULL) {
                                 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
                                 return -ENOMEM;
                         }
 
                         rcu_read_lock();
                         sem_lock_and_putref(sma);
                         if (!ipc_valid_object(&sma->sem_perm)) {
                                 err = -EIDRM;
                                 goto out_unlock;
                         }
                 }
                 for (i = 0; i < sma->sem_nsems; i++)
                         sem_io[i] = sma->sems[i].semval;
                 sem_unlock(sma, -1);
                 rcu_read_unlock();
                 err = 0;
                 if (copy_to_user(array, sem_io, nsems*sizeof(ushort)))
                         err = -EFAULT;
                 goto out_free;
         }
         case SETALL:
         {
                 int i;
                 struct sem_undo *un;
 
                 if (!ipc_rcu_getref(&sma->sem_perm)) {
                         err = -EIDRM;
                         goto out_rcu_wakeup;
                 }
                 rcu_read_unlock();
 
                 if (nsems > SEMMSL_FAST) {
                         sem_io = kvmalloc_array(nsems, sizeof(ushort),
                                                 GFP_KERNEL);
                         if (sem_io == NULL) {
                                 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
                                 return -ENOMEM;
                         }
                 }
 
                 if (copy_from_user(sem_io, p, nsems*sizeof(ushort))) {
                         ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
                         err = -EFAULT;
                         goto out_free;
                 }
 
                 for (i = 0; i < nsems; i++) {
                         if (sem_io[i] > SEMVMX) {
                                 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
                                 err = -ERANGE;
                                 goto out_free;
                         }
                 }
                 rcu_read_lock();
                 sem_lock_and_putref(sma);
                 if (!ipc_valid_object(&sma->sem_perm)) {
                         err = -EIDRM;
                         goto out_unlock;
                 }
 
                 for (i = 0; i < nsems; i++) {
                         sma->sems[i].semval = sem_io[i];
                         ipc_update_pid(&sma->sems[i].sempid, task_tgid(current));
                 }
 
                 ipc_assert_locked_object(&sma->sem_perm);
                 list_for_each_entry(un, &sma->list_id, list_id) {
                         for (i = 0; i < nsems; i++)
                                 un->semadj[i] = 0;
                 }
                 sma->sem_ctime = ktime_get_real_seconds();
                 /* maybe some queued-up processes were waiting for this */
                 do_smart_update(sma, NULL, 0, 0, &wake_q);
                 err = 0;
                 goto out_unlock;
         }
         /* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
         }
         err = -EINVAL;
         if (semnum < 0 || semnum >= nsems)
                 goto out_rcu_wakeup;
 
         sem_lock(sma, NULL, -1);
         if (!ipc_valid_object(&sma->sem_perm)) {
                 err = -EIDRM;
                 goto out_unlock;
         }
 
         semnum = array_index_nospec(semnum, nsems);
         curr = &sma->sems[semnum];
 
         switch (cmd) {
         case GETVAL:
                 err = curr->semval;
                 goto out_unlock;
         case GETPID:
                 err = pid_vnr(curr->sempid);
                 goto out_unlock;
         case GETNCNT:
                 err = count_semcnt(sma, semnum, 0);
                 goto out_unlock;
         case GETZCNT:
                 err = count_semcnt(sma, semnum, 1);
                 goto out_unlock;
         }
 
 out_unlock:
         sem_unlock(sma, -1);
 out_rcu_wakeup:
         rcu_read_unlock();
         wake_up_q(&wake_q);
 out_free:
         if (sem_io != fast_sem_io)
                 kvfree(sem_io);
         return err;
 }
 
 static inline unsigned long
 copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
 {
         switch (version) {
         case IPC_64:
                 if (copy_from_user(out, buf, sizeof(*out)))
                         return -EFAULT;
                 return 0;
         case IPC_OLD:
             {
                 struct semid_ds tbuf_old;
 
                 if (copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
                         return -EFAULT;
 
                 out->sem_perm.uid       = tbuf_old.sem_perm.uid;
                 out->sem_perm.gid       = tbuf_old.sem_perm.gid;
                 out->sem_perm.mode      = tbuf_old.sem_perm.mode;
 
                 return 0;
             }
         default:
                 return -EINVAL;
         }
 }
 
 /*
  * This function handles some semctl commands which require the rwsem
  * to be held in write mode.
  * NOTE: no locks must be held, the rwsem is taken inside this function.
  */
 static int semctl_down(struct ipc_namespace *ns, int semid,
                        int cmd, struct semid64_ds *semid64)
 {
         struct sem_array *sma;
         int err;
         struct kern_ipc_perm *ipcp;
 
         down_write(&sem_ids(ns).rwsem);
         rcu_read_lock();
 
         ipcp = ipcctl_obtain_check(ns, &sem_ids(ns), semid, cmd,
                                       &semid64->sem_perm, 0);
         if (IS_ERR(ipcp)) {
                 err = PTR_ERR(ipcp);
                 goto out_unlock1;
         }
 
         sma = container_of(ipcp, struct sem_array, sem_perm);
 
         err = security_sem_semctl(&sma->sem_perm, cmd);
         if (err)
                 goto out_unlock1;
 
         switch (cmd) {
         case IPC_RMID:
                 sem_lock(sma, NULL, -1);
                 /* freeary unlocks the ipc object and rcu */
                 freeary(ns, ipcp);
                 goto out_up;
         case IPC_SET:
                 sem_lock(sma, NULL, -1);
                 err = ipc_update_perm(&semid64->sem_perm, ipcp);
                 if (err)
                         goto out_unlock0;
                 sma->sem_ctime = ktime_get_real_seconds();
                 break;
         default:
                 err = -EINVAL;
                 goto out_unlock1;
         }
 
 out_unlock0:
         sem_unlock(sma, -1);
 out_unlock1:
         rcu_read_unlock();
 out_up:
         up_write(&sem_ids(ns).rwsem);
         return err;
 }
 
 static long ksys_semctl(int semid, int semnum, int cmd, unsigned long arg, int version)
 {
         struct ipc_namespace *ns;
         void __user *p = (void __user *)arg;
         struct semid64_ds semid64;
         int err;
 
         if (semid < 0)
                 return -EINVAL;
 
         ns = current->nsproxy->ipc_ns;
 
         switch (cmd) {
         case IPC_INFO:
         case SEM_INFO:
                 return semctl_info(ns, semid, cmd, p);
         case IPC_STAT:
         case SEM_STAT:
         case SEM_STAT_ANY:
                 err = semctl_stat(ns, semid, cmd, &semid64);
                 if (err < 0)
                         return err;
                 if (copy_semid_to_user(p, &semid64, version))
                         err = -EFAULT;
                 return err;
         case GETALL:
         case GETVAL:
         case GETPID:
         case GETNCNT:
         case GETZCNT:
         case SETALL:
                 return semctl_main(ns, semid, semnum, cmd, p);
         case SETVAL: {
                 int val;
 #if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
                 /* big-endian 64bit */
                 val = arg >> 32;
 #else
                 /* 32bit or little-endian 64bit */
                 val = arg;
 #endif
                 return semctl_setval(ns, semid, semnum, val);
         }
         case IPC_SET:
                 if (copy_semid_from_user(&semid64, p, version))
                         return -EFAULT;
                 fallthrough;
         case IPC_RMID:
                 return semctl_down(ns, semid, cmd, &semid64);
         default:
                 return -EINVAL;
         }
 }
 
 SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
 {
         return ksys_semctl(semid, semnum, cmd, arg, IPC_64);
 }
 
 #ifdef CONFIG_ARCH_WANT_IPC_PARSE_VERSION
 long ksys_old_semctl(int semid, int semnum, int cmd, unsigned long arg)
 {
         int version = ipc_parse_version(&cmd);
 
         return ksys_semctl(semid, semnum, cmd, arg, version);
 }
 
 SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
 {
         return ksys_old_semctl(semid, semnum, cmd, arg);
 }
 #endif
 
 #ifdef CONFIG_COMPAT
 
 struct compat_semid_ds {
         struct compat_ipc_perm sem_perm;
         old_time32_t sem_otime;
         old_time32_t sem_ctime;
         compat_uptr_t sem_base;
         compat_uptr_t sem_pending;
         compat_uptr_t sem_pending_last;
         compat_uptr_t undo;
         unsigned short sem_nsems;
 };
 
 static int copy_compat_semid_from_user(struct semid64_ds *out, void __user *buf,
                                         int version)
 {
         memset(out, 0, sizeof(*out));
         if (version == IPC_64) {
                 struct compat_semid64_ds __user *p = buf;
                 return get_compat_ipc64_perm(&out->sem_perm, &p->sem_perm);
         } else {
                 struct compat_semid_ds __user *p = buf;
                 return get_compat_ipc_perm(&out->sem_perm, &p->sem_perm);
         }
 }
 
 static int copy_compat_semid_to_user(void __user *buf, struct semid64_ds *in,
                                         int version)
 {
         if (version == IPC_64) {
                 struct compat_semid64_ds v;
                 memset(&v, 0, sizeof(v));
                 to_compat_ipc64_perm(&v.sem_perm, &in->sem_perm);
                 v.sem_otime      = lower_32_bits(in->sem_otime);
                 v.sem_otime_high = upper_32_bits(in->sem_otime);
                 v.sem_ctime      = lower_32_bits(in->sem_ctime);
                 v.sem_ctime_high = upper_32_bits(in->sem_ctime);
                 v.sem_nsems = in->sem_nsems;
                 return copy_to_user(buf, &v, sizeof(v));
         } else {
                 struct compat_semid_ds v;
                 memset(&v, 0, sizeof(v));
                 to_compat_ipc_perm(&v.sem_perm, &in->sem_perm);
                 v.sem_otime = in->sem_otime;
                 v.sem_ctime = in->sem_ctime;
                 v.sem_nsems = in->sem_nsems;
                 return copy_to_user(buf, &v, sizeof(v));
         }
 }
 
 static long compat_ksys_semctl(int semid, int semnum, int cmd, int arg, int version)
 {
         void __user *p = compat_ptr(arg);
         struct ipc_namespace *ns;
         struct semid64_ds semid64;
         int err;
 
         ns = current->nsproxy->ipc_ns;
 
         if (semid < 0)
                 return -EINVAL;
 
         switch (cmd & (~IPC_64)) {
         case IPC_INFO:
         case SEM_INFO:
                 return semctl_info(ns, semid, cmd, p);
         case IPC_STAT:
         case SEM_STAT:
         case SEM_STAT_ANY:
                 err = semctl_stat(ns, semid, cmd, &semid64);
                 if (err < 0)
                         return err;
                 if (copy_compat_semid_to_user(p, &semid64, version))
                         err = -EFAULT;
                 return err;
         case GETVAL:
         case GETPID:
         case GETNCNT:
         case GETZCNT:
         case GETALL:
         case SETALL:
                 return semctl_main(ns, semid, semnum, cmd, p);
         case SETVAL:
                 return semctl_setval(ns, semid, semnum, arg);
         case IPC_SET:
                 if (copy_compat_semid_from_user(&semid64, p, version))
                         return -EFAULT;
                 fallthrough;
         case IPC_RMID:
                 return semctl_down(ns, semid, cmd, &semid64);
         default:
                 return -EINVAL;
         }
 }
 
 COMPAT_SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, int, arg)
 {
         return compat_ksys_semctl(semid, semnum, cmd, arg, IPC_64);
 }
 
 #ifdef CONFIG_ARCH_WANT_COMPAT_IPC_PARSE_VERSION
 long compat_ksys_old_semctl(int semid, int semnum, int cmd, int arg)
 {
         int version = compat_ipc_parse_version(&cmd);
 
         return compat_ksys_semctl(semid, semnum, cmd, arg, version);
 }
 
 COMPAT_SYSCALL_DEFINE4(old_semctl, int, semid, int, semnum, int, cmd, int, arg)
 {
         return compat_ksys_old_semctl(semid, semnum, cmd, arg);
 }
 #endif
 #endif
 
 /* If the task doesn't already have a undo_list, then allocate one
  * here.  We guarantee there is only one thread using this undo list,
  * and current is THE ONE
  *
  * If this allocation and assignment succeeds, but later
  * portions of this code fail, there is no need to free the sem_undo_list.
  * Just let it stay associated with the task, and it'll be freed later
  * at exit time.
  *
  * This can block, so callers must hold no locks.
  */
 static inline int get_undo_list(struct sem_undo_list **undo_listp)
 {
         struct sem_undo_list *undo_list;
 
         undo_list = current->sysvsem.undo_list;
         if (!undo_list) {
                 undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL_ACCOUNT);
                 if (undo_list == NULL)
                         return -ENOMEM;
                 spin_lock_init(&undo_list->lock);
                 refcount_set(&undo_list->refcnt, 1);
                 INIT_LIST_HEAD(&undo_list->list_proc);
 
                 current->sysvsem.undo_list = undo_list;
         }
         *undo_listp = undo_list;
         return 0;
 }
 
 static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
 {
         struct sem_undo *un;
 
         list_for_each_entry_rcu(un, &ulp->list_proc, list_proc,
                                 spin_is_locked(&ulp->lock)) {
                 if (un->semid == semid)
                         return un;
         }
         return NULL;
 }
 
 static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
 {
         struct sem_undo *un;
 
         assert_spin_locked(&ulp->lock);
 
         un = __lookup_undo(ulp, semid);
         if (un) {
                 list_del_rcu(&un->list_proc);
                 list_add_rcu(&un->list_proc, &ulp->list_proc);
         }
         return un;
 }
 
 /**
  * find_alloc_undo - lookup (and if not present create) undo array
  * @ns: namespace
  * @semid: semaphore array id
  *
  * The function looks up (and if not present creates) the undo structure.
  * The size of the undo structure depends on the size of the semaphore
  * array, thus the alloc path is not that straightforward.
  * Lifetime-rules: sem_undo is rcu-protected, on success, the function
  * performs a rcu_read_lock().
  */
 static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
 {
         struct sem_array *sma;
         struct sem_undo_list *ulp;
         struct sem_undo *un, *new;
         int nsems, error;
 
         error = get_undo_list(&ulp);
         if (error)
                 return ERR_PTR(error);
 
         rcu_read_lock();
         spin_lock(&ulp->lock);
         un = lookup_undo(ulp, semid);
         spin_unlock(&ulp->lock);
         if (likely(un != NULL))
                 goto out;
 
         /* no undo structure around - allocate one. */
         /* step 1: figure out the size of the semaphore array */
         sma = sem_obtain_object_check(ns, semid);
         if (IS_ERR(sma)) {
                 rcu_read_unlock();
                 return ERR_CAST(sma);
         }
 
         nsems = sma->sem_nsems;
         if (!ipc_rcu_getref(&sma->sem_perm)) {
                 rcu_read_unlock();
                 un = ERR_PTR(-EIDRM);
                 goto out;
         }
         rcu_read_unlock();
 
         /* step 2: allocate new undo structure */
         new = kvzalloc(struct_size(new, semadj, nsems), GFP_KERNEL_ACCOUNT);
         if (!new) {
                 ipc_rcu_putref(&sma->sem_perm, sem_rcu_free);
                 return ERR_PTR(-ENOMEM);
         }
 
         /* step 3: Acquire the lock on semaphore array */
         rcu_read_lock();
         sem_lock_and_putref(sma);
         if (!ipc_valid_object(&sma->sem_perm)) {
                 sem_unlock(sma, -1);
                 rcu_read_unlock();
                 kvfree(new);
                 un = ERR_PTR(-EIDRM);
                 goto out;
         }
         spin_lock(&ulp->lock);
 
         /*
          * step 4: check for races: did someone else allocate the undo struct?
          */
         un = lookup_undo(ulp, semid);
         if (un) {
                 spin_unlock(&ulp->lock);
                 kvfree(new);
                 goto success;
         }
         /* step 5: initialize & link new undo structure */
         new->ulp = ulp;
         new->semid = semid;
         assert_spin_locked(&ulp->lock);
         list_add_rcu(&new->list_proc, &ulp->list_proc);
         ipc_assert_locked_object(&sma->sem_perm);
         list_add(&new->list_id, &sma->list_id);
         un = new;
         spin_unlock(&ulp->lock);
 success:
         sem_unlock(sma, -1);
 out:
         return un;
 }
 
 long __do_semtimedop(int semid, struct sembuf *sops,
                 unsigned nsops, const struct timespec64 *timeout,
                 struct ipc_namespace *ns)
 {
         int error = -EINVAL;
         struct sem_array *sma;
         struct sembuf *sop;
         struct sem_undo *un;
         int max, locknum;
         bool undos = false, alter = false, dupsop = false;
         struct sem_queue queue;
         unsigned long dup = 0;
         ktime_t expires, *exp = NULL;
         bool timed_out = false;
 
         if (nsops < 1 || semid < 0)
                 return -EINVAL;
         if (nsops > ns->sc_semopm)
                 return -E2BIG;
 
         if (timeout) {
                 if (!timespec64_valid(timeout))
                         return -EINVAL;
                 expires = ktime_add_safe(ktime_get(),
                                 timespec64_to_ktime(*timeout));
                 exp = &expires;
         }
 
 
         max = 0;
         for (sop = sops; sop < sops + nsops; sop++) {
                 unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
 
                 if (sop->sem_num >= max)
                         max = sop->sem_num;
                 if (sop->sem_flg & SEM_UNDO)
                         undos = true;
                 if (dup & mask) {
                         /*
                          * There was a previous alter access that appears
                          * to have accessed the same semaphore, thus use
                          * the dupsop logic. "appears", because the detection
                          * can only check % BITS_PER_LONG.
                          */
                         dupsop = true;
                 }
                 if (sop->sem_op != 0) {
                         alter = true;
                         dup |= mask;
                 }
         }
 
         if (undos) {
                 /* On success, find_alloc_undo takes the rcu_read_lock */
                 un = find_alloc_undo(ns, semid);
                 if (IS_ERR(un)) {
                         error = PTR_ERR(un);
                         goto out;
                 }
         } else {
                 un = NULL;
                 rcu_read_lock();
         }
 
         sma = sem_obtain_object_check(ns, semid);
         if (IS_ERR(sma)) {
                 rcu_read_unlock();
                 error = PTR_ERR(sma);
                 goto out;
         }
 
         error = -EFBIG;
         if (max >= sma->sem_nsems) {
                 rcu_read_unlock();
                 goto out;
         }
 
         error = -EACCES;
         if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
                 rcu_read_unlock();
                 goto out;
         }
 
         error = security_sem_semop(&sma->sem_perm, sops, nsops, alter);
         if (error) {
                 rcu_read_unlock();
                 goto out;
         }
 
         error = -EIDRM;
         locknum = sem_lock(sma, sops, nsops);
         /*
          * We eventually might perform the following check in a lockless
          * fashion, considering ipc_valid_object() locking constraints.
          * If nsops == 1 and there is no contention for sem_perm.lock, then
          * only a per-semaphore lock is held and it's OK to proceed with the
          * check below. More details on the fine grained locking scheme
          * entangled here and why it's RMID race safe on comments at sem_lock()
          */
         if (!ipc_valid_object(&sma->sem_perm))
                 goto out_unlock;
         /*
          * semid identifiers are not unique - find_alloc_undo may have
          * allocated an undo structure, it was invalidated by an RMID
          * and now a new array with received the same id. Check and fail.
          * This case can be detected checking un->semid. The existence of
          * "un" itself is guaranteed by rcu.
          */
         if (un && un->semid == -1)
                 goto out_unlock;
 
         queue.sops = sops;
         queue.nsops = nsops;
         queue.undo = un;
         queue.pid = task_tgid(current);
         queue.alter = alter;
         queue.dupsop = dupsop;
 
         error = perform_atomic_semop(sma, &queue);
         if (error == 0) { /* non-blocking successful path */
                 DEFINE_WAKE_Q(wake_q);
 
                 /*
                  * If the operation was successful, then do
                  * the required updates.
                  */
                 if (alter)
                         do_smart_update(sma, sops, nsops, 1, &wake_q);
                 else
                         set_semotime(sma, sops);
 
                 sem_unlock(sma, locknum);
                 rcu_read_unlock();
                 wake_up_q(&wake_q);
 
                 goto out;
         }
         if (error < 0) /* non-blocking error path */
                 goto out_unlock;
 
         /*
          * We need to sleep on this operation, so we put the current
          * task into the pending queue and go to sleep.
          */
         if (nsops == 1) {
                 struct sem *curr;
                 int idx = array_index_nospec(sops->sem_num, sma->sem_nsems);
                 curr = &sma->sems[idx];
 
                 if (alter) {
                         if (sma->complex_count) {
                                 list_add_tail(&queue.list,
                                                 &sma->pending_alter);
                         } else {
 
                                 list_add_tail(&queue.list,
                                                 &curr->pending_alter);
                         }
                 } else {
                         list_add_tail(&queue.list, &curr->pending_const);
                 }
         } else {
                 if (!sma->complex_count)
                         merge_queues(sma);
 
                 if (alter)
                         list_add_tail(&queue.list, &sma->pending_alter);
                 else
                         list_add_tail(&queue.list, &sma->pending_const);
 
                 sma->complex_count++;
         }
 
         do {
                 /* memory ordering ensured by the lock in sem_lock() */
                 WRITE_ONCE(queue.status, -EINTR);
                 queue.sleeper = current;
 
                 /* memory ordering is ensured by the lock in sem_lock() */
                 __set_current_state(TASK_INTERRUPTIBLE);
                 sem_unlock(sma, locknum);
                 rcu_read_unlock();
 
                 timed_out = !schedule_hrtimeout_range(exp,
                                 current->timer_slack_ns, HRTIMER_MODE_ABS);
 
                 /*
                  * fastpath: the semop has completed, either successfully or
                  * not, from the syscall pov, is quite irrelevant to us at this
                  * point; we're done.
                  *
                  * We _do_ care, nonetheless, about being awoken by a signal or
                  * spuriously.  The queue.status is checked again in the
                  * slowpath (aka after taking sem_lock), such that we can detect
                  * scenarios where we were awakened externally, during the
                  * window between wake_q_add() and wake_up_q().
                  */
                 rcu_read_lock();
                 error = READ_ONCE(queue.status);
                 if (error != -EINTR) {
                         /* see SEM_BARRIER_2 for purpose/pairing */
                         smp_acquire__after_ctrl_dep();
                         rcu_read_unlock();
                         goto out;
                 }
 
                 locknum = sem_lock(sma, sops, nsops);
 
                 if (!ipc_valid_object(&sma->sem_perm))
                         goto out_unlock;
 
                 /*
                  * No necessity for any barrier: We are protect by sem_lock()
                  */
                 error = READ_ONCE(queue.status);
 
                 /*
                  * If queue.status != -EINTR we are woken up by another process.
                  * Leave without unlink_queue(), but with sem_unlock().
                  */
                 if (error != -EINTR)
                         goto out_unlock;
 
                 /*
                  * If an interrupt occurred we have to clean up the queue.
                  */
                 if (timed_out)
                         error = -EAGAIN;
         } while (error == -EINTR && !signal_pending(current)); /* spurious */
 
         unlink_queue(sma, &queue);
 
 out_unlock:
         sem_unlock(sma, locknum);
         rcu_read_unlock();
 out:
         return error;
 }
 
 static long do_semtimedop(int semid, struct sembuf __user *tsops,
                 unsigned nsops, const struct timespec64 *timeout)
 {
         struct sembuf fast_sops[SEMOPM_FAST];
         struct sembuf *sops = fast_sops;
         struct ipc_namespace *ns;
         int ret;
 
         ns = current->nsproxy->ipc_ns;
         if (nsops > ns->sc_semopm)
                 return -E2BIG;
         if (nsops < 1)
                 return -EINVAL;
 
         if (nsops > SEMOPM_FAST) {
                 sops = kvmalloc_array(nsops, sizeof(*sops), GFP_KERNEL);
                 if (sops == NULL)
                         return -ENOMEM;
         }
 
         if (copy_from_user(sops, tsops, nsops * sizeof(*tsops))) {
                 ret =  -EFAULT;
                 goto out_free;
         }
 
         ret = __do_semtimedop(semid, sops, nsops, timeout, ns);
 
 out_free:
         if (sops != fast_sops)
                 kvfree(sops);
 
         return ret;
 }
 
 long ksys_semtimedop(int semid, struct sembuf __user *tsops,
                      unsigned int nsops, const struct __kernel_timespec __user *timeout)
 {
         if (timeout) {
                 struct timespec64 ts;
                 if (get_timespec64(&ts, timeout))
                         return -EFAULT;
                 return do_semtimedop(semid, tsops, nsops, &ts);
         }
         return do_semtimedop(semid, tsops, nsops, NULL);
 }
 
 SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
                 unsigned int, nsops, const struct __kernel_timespec __user *, timeout)
 {
         return ksys_semtimedop(semid, tsops, nsops, timeout);
 }
 
 #ifdef CONFIG_COMPAT_32BIT_TIME
 long compat_ksys_semtimedop(int semid, struct sembuf __user *tsems,
                             unsigned int nsops,
                             const struct old_timespec32 __user *timeout)
 {
         if (timeout) {
                 struct timespec64 ts;
                 if (get_old_timespec32(&ts, timeout))
                         return -EFAULT;
                 return do_semtimedop(semid, tsems, nsops, &ts);
         }
         return do_semtimedop(semid, tsems, nsops, NULL);
 }
 
 SYSCALL_DEFINE4(semtimedop_time32, int, semid, struct sembuf __user *, tsems,
                        unsigned int, nsops,
                        const struct old_timespec32 __user *, timeout)
 {
         return compat_ksys_semtimedop(semid, tsems, nsops, timeout);
 }
 #endif
 
 SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
                 unsigned, nsops)
 {
         return do_semtimedop(semid, tsops, nsops, NULL);
 }
 
 /* If CLONE_SYSVSEM is set, establish sharing of SEM_UNDO state between
  * parent and child tasks.
  */
 
 int copy_semundo(unsigned long clone_flags, struct task_struct *tsk)
 {
         struct sem_undo_list *undo_list;
         int error;
 
         if (clone_flags & CLONE_SYSVSEM) {
                 error = get_undo_list(&undo_list);
                 if (error)
                         return error;
                 refcount_inc(&undo_list->refcnt);
                 tsk->sysvsem.undo_list = undo_list;
         } else
                 tsk->sysvsem.undo_list = NULL;
 
         return 0;
 }
 
 /*
  * add semadj values to semaphores, free undo structures.
  * undo structures are not freed when semaphore arrays are destroyed
  * so some of them may be out of date.
  * IMPLEMENTATION NOTE: There is some confusion over whether the
  * set of adjustments that needs to be done should be done in an atomic
  * manner or not. That is, if we are attempting to decrement the semval
  * should we queue up and wait until we can do so legally?
  * The original implementation attempted to do this (queue and wait).
  * The current implementation does not do so. The POSIX standard
  * and SVID should be consulted to determine what behavior is mandated.
  */
 void exit_sem(struct task_struct *tsk)
 {
         struct sem_undo_list *ulp;
 
         ulp = tsk->sysvsem.undo_list;
         if (!ulp)
                 return;
         tsk->sysvsem.undo_list = NULL;
 
         if (!refcount_dec_and_test(&ulp->refcnt))
                 return;
 
         for (;;) {
                 struct sem_array *sma;
                 struct sem_undo *un;
                 int semid, i;
                 DEFINE_WAKE_Q(wake_q);
 
                 cond_resched();
 
                 rcu_read_lock();
                 un = list_entry_rcu(ulp->list_proc.next,
                                     struct sem_undo, list_proc);
                 if (&un->list_proc == &ulp->list_proc) {
                         /*
                          * We must wait for freeary() before freeing this ulp,
                          * in case we raced with last sem_undo. There is a small
                          * possibility where we exit while freeary() didn't
                          * finish unlocking sem_undo_list.
                          */
                         spin_lock(&ulp->lock);
                         spin_unlock(&ulp->lock);
                         rcu_read_unlock();
                         break;
                 }
                 spin_lock(&ulp->lock);
                 semid = un->semid;
                 spin_unlock(&ulp->lock);
 
                 /* exit_sem raced with IPC_RMID, nothing to do */
                 if (semid == -1) {
                         rcu_read_unlock();
                         continue;
                 }
 
                 sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, semid);
                 /* exit_sem raced with IPC_RMID, nothing to do */
                 if (IS_ERR(sma)) {
                         rcu_read_unlock();
                         continue;
                 }
 
                 sem_lock(sma, NULL, -1);
                 /* exit_sem raced with IPC_RMID, nothing to do */
                 if (!ipc_valid_object(&sma->sem_perm)) {
                         sem_unlock(sma, -1);
                         rcu_read_unlock();
                         continue;
                 }
                 un = __lookup_undo(ulp, semid);
                 if (un == NULL) {
                         /* exit_sem raced with IPC_RMID+semget() that created
                          * exactly the same semid. Nothing to do.
                          */
                         sem_unlock(sma, -1);
                         rcu_read_unlock();
                         continue;
                 }
 
                 /* remove un from the linked lists */
                 ipc_assert_locked_object(&sma->sem_perm);
                 list_del(&un->list_id);
 
                 spin_lock(&ulp->lock);
                 list_del_rcu(&un->list_proc);
                 spin_unlock(&ulp->lock);
 
                 /* perform adjustments registered in un */
                 for (i = 0; i < sma->sem_nsems; i++) {
                         struct sem *semaphore = &sma->sems[i];
                         if (un->semadj[i]) {
                                 semaphore->semval += un->semadj[i];
                                 /*
                                  * Range checks of the new semaphore value,
                                  * not defined by sus:
                                  * - Some unices ignore the undo entirely
                                  *   (e.g. HP UX 11i 11.22, Tru64 V5.1)
                                  * - some cap the value (e.g. FreeBSD caps
                                  *   at 0, but doesn't enforce SEMVMX)
                                  *
                                  * Linux caps the semaphore value, both at 0
                                  * and at SEMVMX.
                                  *
                                  *      Manfred <manfred@colorfullife.com>
                                  */
                                 if (semaphore->semval < 0)
                                         semaphore->semval = 0;
                                 if (semaphore->semval > SEMVMX)
                                         semaphore->semval = SEMVMX;
                                 ipc_update_pid(&semaphore->sempid, task_tgid(current));
                         }
                 }
                 /* maybe some queued-up processes were waiting for this */
                 do_smart_update(sma, NULL, 0, 1, &wake_q);
                 sem_unlock(sma, -1);
                 rcu_read_unlock();
                 wake_up_q(&wake_q);
 
                 kvfree_rcu(un, rcu);
         }
         kfree(ulp);
 }
 
 #ifdef CONFIG_PROC_FS
 static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
 {
         struct user_namespace *user_ns = seq_user_ns(s);
         struct kern_ipc_perm *ipcp = it;
         struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
         time64_t sem_otime;
 
         /*
          * The proc interface isn't aware of sem_lock(), it calls
          * ipc_lock_object(), i.e. spin_lock(&sma->sem_perm.lock).
          * (in sysvipc_find_ipc)
          * In order to stay compatible with sem_lock(), we must
          * enter / leave complex_mode.
          */
         complexmode_enter(sma);
 
         sem_otime = get_semotime(sma);
 
         seq_printf(s,
                    "%10d %10d  %4o %10u %5u %5u %5u %5u %10llu %10llu\n",
                    sma->sem_perm.key,
                    sma->sem_perm.id,
                    sma->sem_perm.mode,
                    sma->sem_nsems,
                    from_kuid_munged(user_ns, sma->sem_perm.uid),
                    from_kgid_munged(user_ns, sma->sem_perm.gid),
                    from_kuid_munged(user_ns, sma->sem_perm.cuid),
                    from_kgid_munged(user_ns, sma->sem_perm.cgid),
                    sem_otime,
                    sma->sem_ctime);
 
         complexmode_tryleave(sma);
 
         return 0;
 }
 #endif
 

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