sem.c 46.7 KB
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/*
 * 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
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 * (c) 1999 Manfred Spraul <manfred@colorfullife.com>
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 * Enforced range limit on SEM_UNDO
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 * (c) 2001 Red Hat Inc
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 * Lockless wakeup
 * (c) 2003 Manfred Spraul <manfred@colorfullife.com>
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 * Further wakeup optimizations, documentation
 * (c) 2010 Manfred Spraul <manfred@colorfullife.com>
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 *
 * support for audit of ipc object properties and permission changes
 * Dustin Kirkland <dustin.kirkland@us.ibm.com>
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 *
 * namespaces support
 * OpenVZ, SWsoft Inc.
 * Pavel Emelianov <xemul@openvz.org>
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 *
 * 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 runtine 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_semncnt() and
 *   count_semzcnt()
 * - 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(),
 *   wake_up_sem_queue_do())
 * - 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).
 * - The synchronizations between wake-ups due to a timeout/signal and a
 *   wake-up due to a completed semaphore operation is achieved by using an
 *   intermediate state (IN_WAKEUP).
 * - 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.
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 */

#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>
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#include <linux/capability.h>
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#include <linux/seq_file.h>
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#include <linux/rwsem.h>
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#include <linux/nsproxy.h>
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#include <linux/ipc_namespace.h>
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#include <asm/uaccess.h>
#include "util.h"

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/* One semaphore structure for each semaphore in the system. */
struct sem {
	int	semval;		/* current value */
	int	sempid;		/* pid of last operation */
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	spinlock_t	lock;	/* spinlock for fine-grained semtimedop */
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	struct list_head sem_pending; /* pending single-sop operations */
};

/* 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 */
	int			pid;	 /* process id of requesting process */
	int			status;	 /* completion status of operation */
	struct sembuf		*sops;	 /* array of pending operations */
	int			nsops;	 /* number of operations */
	int			alter;	 /* does *sops alter the array? */
};

/* 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 {
	atomic_t		refcnt;
	spinlock_t		lock;
	struct list_head	list_proc;
};


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#define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
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#define sem_checkid(sma, semid)	ipc_checkid(&sma->sem_perm, semid)
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static int newary(struct ipc_namespace *, struct ipc_params *);
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static void freeary(struct ipc_namespace *, struct kern_ipc_perm *);
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#ifdef CONFIG_PROC_FS
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static int sysvipc_sem_proc_show(struct seq_file *s, void *it);
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#endif

#define SEMMSL_FAST	256 /* 512 bytes on stack */
#define SEMOPM_FAST	64  /* ~ 372 bytes on stack */

/*
 * linked list protection:
 *	sem_undo.id_next,
 *	sem_array.sem_pending{,last},
 *	sem_array.sem_undo: sem_lock() for read/write
 *	sem_undo.proc_next: only "current" is allowed to read/write that field.
 *	
 */

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#define sc_semmsl	sem_ctls[0]
#define sc_semmns	sem_ctls[1]
#define sc_semopm	sem_ctls[2]
#define sc_semmni	sem_ctls[3]

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void sem_init_ns(struct ipc_namespace *ns)
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{
	ns->sc_semmsl = SEMMSL;
	ns->sc_semmns = SEMMNS;
	ns->sc_semopm = SEMOPM;
	ns->sc_semmni = SEMMNI;
	ns->used_sems = 0;
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	ipc_init_ids(&ns->ids[IPC_SEM_IDS]);
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}

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#ifdef CONFIG_IPC_NS
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void sem_exit_ns(struct ipc_namespace *ns)
{
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	free_ipcs(ns, &sem_ids(ns), freeary);
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	idr_destroy(&ns->ids[IPC_SEM_IDS].ipcs_idr);
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}
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#endif
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void __init sem_init (void)
{
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	sem_init_ns(&init_ipc_ns);
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	ipc_init_proc_interface("sysvipc/sem",
				"       key      semid perms      nsems   uid   gid  cuid  cgid      otime      ctime\n",
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				IPC_SEM_IDS, sysvipc_sem_proc_show);
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}

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/*
 * 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.
 *
 * Carefully guard against sma->complex_count changing between zero
 * and non-zero while we are spinning for the lock. The value of
 * sma->complex_count cannot change while we are holding the lock,
 * so sem_unlock should be fine.
 *
 * The global lock path checks that all the local locks have been released,
 * checking each local lock once. This means that the local lock paths
 * cannot start their critical sections while the global lock is held.
 */
static inline int sem_lock(struct sem_array *sma, struct sembuf *sops,
			      int nsops)
{
	int locknum;
 again:
	if (nsops == 1 && !sma->complex_count) {
		struct sem *sem = sma->sem_base + sops->sem_num;

		/* Lock just the semaphore we are interested in. */
		spin_lock(&sem->lock);

		/*
		 * If sma->complex_count was set while we were spinning,
		 * we may need to look at things we did not lock here.
		 */
		if (unlikely(sma->complex_count)) {
			spin_unlock(&sem->lock);
			goto lock_array;
		}

		/*
		 * Another process is holding the global lock on the
		 * sem_array; we cannot enter our critical section,
		 * but have to wait for the global lock to be released.
		 */
		if (unlikely(spin_is_locked(&sma->sem_perm.lock))) {
			spin_unlock(&sem->lock);
			spin_unlock_wait(&sma->sem_perm.lock);
			goto again;
		}

		locknum = sops->sem_num;
	} else {
		int i;
		/*
		 * Lock the semaphore array, and wait for all of the
		 * individual semaphore locks to go away.  The code
		 * above ensures no new single-lock holders will enter
		 * their critical section while the array lock is held.
		 */
 lock_array:
		spin_lock(&sma->sem_perm.lock);
		for (i = 0; i < sma->sem_nsems; i++) {
			struct sem *sem = sma->sem_base + i;
			spin_unlock_wait(&sem->lock);
		}
		locknum = -1;
	}
	return locknum;
}

static inline void sem_unlock(struct sem_array *sma, int locknum)
{
	if (locknum == -1) {
		spin_unlock(&sma->sem_perm.lock);
	} else {
		struct sem *sem = sma->sem_base + locknum;
		spin_unlock(&sem->lock);
	}
}

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/*
 * sem_lock_(check_) routines are called in the paths where the rw_mutex
 * is not held.
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 *
 * The caller holds the RCU read lock.
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 */
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static inline struct sem_array *sem_obtain_lock(struct ipc_namespace *ns,
			int id, struct sembuf *sops, int nsops, int *locknum)
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{
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	struct kern_ipc_perm *ipcp;
	struct sem_array *sma;
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	ipcp = ipc_obtain_object(&sem_ids(ns), id);
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	if (IS_ERR(ipcp))
		return ERR_CAST(ipcp);
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	sma = container_of(ipcp, struct sem_array, sem_perm);
	*locknum = sem_lock(sma, sops, nsops);
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	/* ipc_rmid() may have already freed the ID while sem_lock
	 * was spinning: verify that the structure is still valid
	 */
	if (!ipcp->deleted)
		return container_of(ipcp, struct sem_array, sem_perm);

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	sem_unlock(sma, *locknum);
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	return ERR_PTR(-EINVAL);
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}

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static inline struct sem_array *sem_obtain_object(struct ipc_namespace *ns, int id)
{
	struct kern_ipc_perm *ipcp = ipc_obtain_object(&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);
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	return container_of(ipcp, struct sem_array, sem_perm);
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}

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static inline void sem_lock_and_putref(struct sem_array *sma)
{
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	sem_lock(sma, NULL, -1);
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	ipc_rcu_putref(sma);
}

static inline void sem_putref(struct sem_array *sma)
{
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	ipc_rcu_putref(sma);
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}

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static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)
{
	ipc_rmid(&sem_ids(ns), &s->sem_perm);
}

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/*
 * Lockless wakeup algorithm:
 * Without the check/retry algorithm a lockless wakeup is possible:
 * - queue.status is initialized to -EINTR before blocking.
 * - wakeup is performed by
 *	* unlinking the queue entry from sma->sem_pending
 *	* setting queue.status to IN_WAKEUP
 *	  This is the notification for the blocked thread that a
 *	  result value is imminent.
 *	* call wake_up_process
 *	* set queue.status to the final value.
 * - the previously blocked thread checks queue.status:
 *   	* if it's IN_WAKEUP, then it must wait until the value changes
 *   	* if it's not -EINTR, then the operation was completed by
 *   	  update_queue. semtimedop can return queue.status without
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 *   	  performing any operation on the sem array.
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 *   	* otherwise it must acquire the spinlock and check what's up.
 *
 * The two-stage algorithm is necessary to protect against the following
 * races:
 * - if queue.status is set after wake_up_process, then the woken up idle
 *   thread could race forward and try (and fail) to acquire sma->lock
 *   before update_queue had a chance to set queue.status
 * - if queue.status is written before wake_up_process and if the
 *   blocked process is woken up by a signal between writing
 *   queue.status and the wake_up_process, then the woken up
 *   process could return from semtimedop and die by calling
 *   sys_exit before wake_up_process is called. Then wake_up_process
 *   will oops, because the task structure is already invalid.
 *   (yes, this happened on s390 with sysv msg).
 *
 */
#define IN_WAKEUP	1

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/**
 * newary - Create a new semaphore set
 * @ns: namespace
 * @params: ptr to the structure that contains key, semflg and nsems
 *
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 * Called with sem_ids.rw_mutex held (as a writer)
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 */

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static int newary(struct ipc_namespace *ns, struct ipc_params *params)
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{
	int id;
	int retval;
	struct sem_array *sma;
	int size;
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	key_t key = params->key;
	int nsems = params->u.nsems;
	int semflg = params->flg;
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	int i;
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	if (!nsems)
		return -EINVAL;
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	if (ns->used_sems + nsems > ns->sc_semmns)
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		return -ENOSPC;

	size = sizeof (*sma) + nsems * sizeof (struct sem);
	sma = ipc_rcu_alloc(size);
	if (!sma) {
		return -ENOMEM;
	}
	memset (sma, 0, size);

	sma->sem_perm.mode = (semflg & S_IRWXUGO);
	sma->sem_perm.key = key;

	sma->sem_perm.security = NULL;
	retval = security_sem_alloc(sma);
	if (retval) {
		ipc_rcu_putref(sma);
		return retval;
	}

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	id = ipc_addid(&sem_ids(ns), &sma->sem_perm, ns->sc_semmni);
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	if (id < 0) {
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		security_sem_free(sma);
		ipc_rcu_putref(sma);
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		return id;
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	}
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	ns->used_sems += nsems;
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	sma->sem_base = (struct sem *) &sma[1];
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	for (i = 0; i < nsems; i++) {
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		INIT_LIST_HEAD(&sma->sem_base[i].sem_pending);
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		spin_lock_init(&sma->sem_base[i].lock);
	}
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	sma->complex_count = 0;
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	INIT_LIST_HEAD(&sma->sem_pending);
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	INIT_LIST_HEAD(&sma->list_id);
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	sma->sem_nsems = nsems;
	sma->sem_ctime = get_seconds();
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	sem_unlock(sma, -1);
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	rcu_read_unlock();
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	return sma->sem_perm.id;
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}

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/*
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 * Called with sem_ids.rw_mutex and ipcp locked.
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 */
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static inline int sem_security(struct kern_ipc_perm *ipcp, int semflg)
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{
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	struct sem_array *sma;

	sma = container_of(ipcp, struct sem_array, sem_perm);
	return security_sem_associate(sma, semflg);
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}

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/*
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 * Called with sem_ids.rw_mutex and ipcp locked.
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 */
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static inline int sem_more_checks(struct kern_ipc_perm *ipcp,
				struct ipc_params *params)
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{
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	struct sem_array *sma;

	sma = container_of(ipcp, struct sem_array, sem_perm);
	if (params->u.nsems > sma->sem_nsems)
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		return -EINVAL;

	return 0;
}

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SYSCALL_DEFINE3(semget, key_t, key, int, nsems, int, semflg)
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{
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	struct ipc_namespace *ns;
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	struct ipc_ops sem_ops;
	struct ipc_params sem_params;
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	ns = current->nsproxy->ipc_ns;
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	if (nsems < 0 || nsems > ns->sc_semmsl)
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		return -EINVAL;
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	sem_ops.getnew = newary;
	sem_ops.associate = sem_security;
	sem_ops.more_checks = sem_more_checks;

	sem_params.key = key;
	sem_params.flg = semflg;
	sem_params.u.nsems = nsems;
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	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
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}

/*
 * Determine whether a sequence of semaphore operations would succeed
 * all at once. Return 0 if yes, 1 if need to sleep, else return error code.
 */

static int try_atomic_semop (struct sem_array * sma, struct sembuf * sops,
			     int nsops, struct sem_undo *un, int pid)
{
	int result, sem_op;
	struct sembuf *sop;
	struct sem * curr;

	for (sop = sops; sop < sops + nsops; sop++) {
		curr = sma->sem_base + sop->sem_num;
		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;
		}
		curr->semval = result;
	}

	sop--;
	while (sop >= sops) {
		sma->sem_base[sop->sem_num].sempid = pid;
		if (sop->sem_flg & SEM_UNDO)
			un->semadj[sop->sem_num] -= sop->sem_op;
		sop--;
	}
	
	return 0;

out_of_range:
	result = -ERANGE;
	goto undo;

would_block:
	if (sop->sem_flg & IPC_NOWAIT)
		result = -EAGAIN;
	else
		result = 1;

undo:
	sop--;
	while (sop >= sops) {
		sma->sem_base[sop->sem_num].semval -= sop->sem_op;
		sop--;
	}

	return result;
}

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/** wake_up_sem_queue_prepare(q, error): Prepare wake-up
 * @q: queue entry that must be signaled
 * @error: Error value for the signal
 *
 * Prepare the wake-up of the queue entry q.
N
Nick Piggin 已提交
556
 */
557 558
static void wake_up_sem_queue_prepare(struct list_head *pt,
				struct sem_queue *q, int error)
N
Nick Piggin 已提交
559
{
560 561 562 563 564 565 566
	if (list_empty(pt)) {
		/*
		 * Hold preempt off so that we don't get preempted and have the
		 * wakee busy-wait until we're scheduled back on.
		 */
		preempt_disable();
	}
N
Nick Piggin 已提交
567
	q->status = IN_WAKEUP;
568 569
	q->pid = error;

570
	list_add_tail(&q->list, pt);
571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587
}

/**
 * wake_up_sem_queue_do(pt) - do the actual wake-up
 * @pt: list of tasks to be woken up
 *
 * Do the actual wake-up.
 * The function is called without any locks held, thus the semaphore array
 * could be destroyed already and the tasks can disappear as soon as the
 * status is set to the actual return code.
 */
static void wake_up_sem_queue_do(struct list_head *pt)
{
	struct sem_queue *q, *t;
	int did_something;

	did_something = !list_empty(pt);
588
	list_for_each_entry_safe(q, t, pt, list) {
589 590 591 592 593 594 595
		wake_up_process(q->sleeper);
		/* q can disappear immediately after writing q->status. */
		smp_wmb();
		q->status = q->pid;
	}
	if (did_something)
		preempt_enable();
N
Nick Piggin 已提交
596 597
}

598 599 600
static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
{
	list_del(&q->list);
601
	if (q->nsops > 1)
602 603 604
		sma->complex_count--;
}

605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653
/** 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
 * was completed.
 */
static int check_restart(struct sem_array *sma, struct sem_queue *q)
{
	struct sem *curr;
	struct sem_queue *h;

	/* if the operation didn't modify the array, then no restart */
	if (q->alter == 0)
		return 0;

	/* pending complex operations are too difficult to analyse */
	if (sma->complex_count)
		return 1;

	/* we were a sleeping complex operation. Too difficult */
	if (q->nsops > 1)
		return 1;

	curr = sma->sem_base + q->sops[0].sem_num;

	/* No-one waits on this queue */
	if (list_empty(&curr->sem_pending))
		return 0;

	/* the new semaphore value */
	if (curr->semval) {
		/* It is impossible that someone waits for the new value:
		 * - q is a previously sleeping simple operation that
		 *   altered the array. It must be a decrement, because
		 *   simple increments never sleep.
		 * - The value is not 0, thus wait-for-zero won't proceed.
		 * - 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.
		 */
		BUG_ON(q->sops[0].sem_op >= 0);
		return 0;
	}
	/*
	 * semval is 0. Check if there are wait-for-zero semops.
654
	 * They must be the first entries in the per-semaphore queue
655
	 */
656
	h = list_first_entry(&curr->sem_pending, struct sem_queue, list);
657 658 659 660 661 662 663 664 665 666 667
	BUG_ON(h->nsops != 1);
	BUG_ON(h->sops[0].sem_num != q->sops[0].sem_num);

	/* Yes, there is a wait-for-zero semop. Restart */
	if (h->sops[0].sem_op == 0)
		return 1;

	/* Again - no-one is waiting for the new value. */
	return 0;
}

668 669 670 671 672

/**
 * update_queue(sma, semnum): Look for tasks that can be completed.
 * @sma: semaphore array.
 * @semnum: semaphore that was modified.
673
 * @pt: list head for the tasks that must be woken up.
674 675
 *
 * update_queue must be called after a semaphore in a semaphore array
676 677 678
 * 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.
679 680 681
 * The tasks that must be woken up are added to @pt. The return code
 * is stored in q->pid.
 * The function return 1 if at least one semop was completed successfully.
L
Linus Torvalds 已提交
682
 */
683
static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
L
Linus Torvalds 已提交
684
{
685 686 687
	struct sem_queue *q;
	struct list_head *walk;
	struct list_head *pending_list;
688
	int semop_completed = 0;
689

690
	if (semnum == -1)
691
		pending_list = &sma->sem_pending;
692
	else
693
		pending_list = &sma->sem_base[semnum].sem_pending;
N
Nick Piggin 已提交
694 695

again:
696 697
	walk = pending_list->next;
	while (walk != pending_list) {
698
		int error, restart;
699

700
		q = container_of(walk, struct sem_queue, list);
701
		walk = walk->next;
L
Linus Torvalds 已提交
702

703 704 705 706 707 708 709 710 711 712 713
		/* 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 the "alter" entries: 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->sem_base[semnum].semval == 0 &&
				q->alter)
			break;

L
Linus Torvalds 已提交
714 715 716 717
		error = try_atomic_semop(sma, q->sops, q->nsops,
					 q->undo, q->pid);

		/* Does q->sleeper still need to sleep? */
N
Nick Piggin 已提交
718 719 720
		if (error > 0)
			continue;

721
		unlink_queue(sma, q);
N
Nick Piggin 已提交
722

723
		if (error) {
724
			restart = 0;
725 726
		} else {
			semop_completed = 1;
727
			restart = check_restart(sma, q);
728
		}
729

730
		wake_up_sem_queue_prepare(pt, q, error);
731
		if (restart)
N
Nick Piggin 已提交
732
			goto again;
L
Linus Torvalds 已提交
733
	}
734
	return semop_completed;
L
Linus Torvalds 已提交
735 736
}

737 738
/**
 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
739 740 741
 * @sma: semaphore array
 * @sops: operations that were performed
 * @nsops: number of operations
742 743
 * @otime: force setting otime
 * @pt: list head of the tasks that must be woken up.
744 745 746
 *
 * do_smart_update() does the required called to update_queue, based on the
 * actual changes that were performed on the semaphore array.
747 748 749
 * Note that the function does not do the actual wake-up: the caller is
 * responsible for calling wake_up_sem_queue_do(@pt).
 * It is safe to perform this call after dropping all locks.
750
 */
751 752
static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
			int otime, struct list_head *pt)
753 754 755 756
{
	int i;

	if (sma->complex_count || sops == NULL) {
757 758
		if (update_queue(sma, -1, pt))
			otime = 1;
759 760 761 762 763 764 765 766
	}

	if (!sops) {
		/* No semops; something special is going on. */
		for (i = 0; i < sma->sem_nsems; i++) {
			if (update_queue(sma, i, pt))
				otime = 1;
		}
767
		goto done;
768 769
	}

770
	/* Check the semaphores that were modified. */
771 772 773 774
	for (i = 0; i < nsops; i++) {
		if (sops[i].sem_op > 0 ||
			(sops[i].sem_op < 0 &&
				sma->sem_base[sops[i].sem_num].semval == 0))
775 776
			if (update_queue(sma, sops[i].sem_num, pt))
				otime = 1;
777
	}
778 779 780
done:
	if (otime)
		sma->sem_otime = get_seconds();
781 782 783
}


L
Linus Torvalds 已提交
784 785 786 787 788 789 790 791 792 793 794 795 796 797 798
/* 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
 * This model assumes that a task waits on exactly one semaphore.
 * Since semaphore operations are to be performed atomically, tasks actually
 * wait on a whole sequence of semaphores simultaneously.
 * The counts we return here are a rough approximation, but still
 * warrant that semncnt+semzcnt>0 if the task is on the pending queue.
 */
static int count_semncnt (struct sem_array * sma, ushort semnum)
{
	int semncnt;
	struct sem_queue * q;

	semncnt = 0;
799
	list_for_each_entry(q, &sma->sem_pending, list) {
L
Linus Torvalds 已提交
800 801 802 803 804 805 806 807 808 809 810
		struct sembuf * sops = q->sops;
		int nsops = q->nsops;
		int i;
		for (i = 0; i < nsops; i++)
			if (sops[i].sem_num == semnum
			    && (sops[i].sem_op < 0)
			    && !(sops[i].sem_flg & IPC_NOWAIT))
				semncnt++;
	}
	return semncnt;
}
811

L
Linus Torvalds 已提交
812 813 814 815 816 817
static int count_semzcnt (struct sem_array * sma, ushort semnum)
{
	int semzcnt;
	struct sem_queue * q;

	semzcnt = 0;
818
	list_for_each_entry(q, &sma->sem_pending, list) {
L
Linus Torvalds 已提交
819 820 821 822 823 824 825 826 827 828 829 830
		struct sembuf * sops = q->sops;
		int nsops = q->nsops;
		int i;
		for (i = 0; i < nsops; i++)
			if (sops[i].sem_num == semnum
			    && (sops[i].sem_op == 0)
			    && !(sops[i].sem_flg & IPC_NOWAIT))
				semzcnt++;
	}
	return semzcnt;
}

N
Nadia Derbey 已提交
831 832 833
/* Free a semaphore set. freeary() is called with sem_ids.rw_mutex locked
 * as a writer and the spinlock for this semaphore set hold. sem_ids.rw_mutex
 * remains locked on exit.
L
Linus Torvalds 已提交
834
 */
835
static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
L
Linus Torvalds 已提交
836
{
837 838
	struct sem_undo *un, *tu;
	struct sem_queue *q, *tq;
839
	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
840
	struct list_head tasks;
841
	int i;
L
Linus Torvalds 已提交
842

843
	/* Free the existing undo structures for this semaphore set.  */
844
	assert_spin_locked(&sma->sem_perm.lock);
845 846 847
	list_for_each_entry_safe(un, tu, &sma->list_id, list_id) {
		list_del(&un->list_id);
		spin_lock(&un->ulp->lock);
L
Linus Torvalds 已提交
848
		un->semid = -1;
849 850
		list_del_rcu(&un->list_proc);
		spin_unlock(&un->ulp->lock);
851
		kfree_rcu(un, rcu);
852
	}
L
Linus Torvalds 已提交
853 854

	/* Wake up all pending processes and let them fail with EIDRM. */
855
	INIT_LIST_HEAD(&tasks);
856
	list_for_each_entry_safe(q, tq, &sma->sem_pending, list) {
857
		unlink_queue(sma, q);
858
		wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
L
Linus Torvalds 已提交
859
	}
860 861 862 863 864 865 866
	for (i = 0; i < sma->sem_nsems; i++) {
		struct sem *sem = sma->sem_base + i;
		list_for_each_entry_safe(q, tq, &sem->sem_pending, list) {
			unlink_queue(sma, q);
			wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
		}
	}
L
Linus Torvalds 已提交
867

N
Nadia Derbey 已提交
868 869
	/* Remove the semaphore set from the IDR */
	sem_rmid(ns, sma);
870
	sem_unlock(sma, -1);
871
	rcu_read_unlock();
L
Linus Torvalds 已提交
872

873
	wake_up_sem_queue_do(&tasks);
K
Kirill Korotaev 已提交
874
	ns->used_sems -= sma->sem_nsems;
L
Linus Torvalds 已提交
875 876 877 878 879 880 881 882 883 884 885 886 887
	security_sem_free(sma);
	ipc_rcu_putref(sma);
}

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;

888 889
		memset(&out, 0, sizeof(out));

L
Linus Torvalds 已提交
890 891 892 893 894 895 896 897 898 899 900 901 902
		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;
	}
}

903
static int semctl_nolock(struct ipc_namespace *ns, int semid,
904
			 int cmd, int version, void __user *p)
L
Linus Torvalds 已提交
905
{
906
	int err;
L
Linus Torvalds 已提交
907 908 909 910 911 912 913 914 915 916 917 918 919 920
	struct sem_array *sma;

	switch(cmd) {
	case IPC_INFO:
	case SEM_INFO:
	{
		struct seminfo seminfo;
		int max_id;

		err = security_sem_semctl(NULL, cmd);
		if (err)
			return err;
		
		memset(&seminfo,0,sizeof(seminfo));
K
Kirill Korotaev 已提交
921 922 923 924
		seminfo.semmni = ns->sc_semmni;
		seminfo.semmns = ns->sc_semmns;
		seminfo.semmsl = ns->sc_semmsl;
		seminfo.semopm = ns->sc_semopm;
L
Linus Torvalds 已提交
925 926 927 928
		seminfo.semvmx = SEMVMX;
		seminfo.semmnu = SEMMNU;
		seminfo.semmap = SEMMAP;
		seminfo.semume = SEMUME;
N
Nadia Derbey 已提交
929
		down_read(&sem_ids(ns).rw_mutex);
L
Linus Torvalds 已提交
930
		if (cmd == SEM_INFO) {
K
Kirill Korotaev 已提交
931 932
			seminfo.semusz = sem_ids(ns).in_use;
			seminfo.semaem = ns->used_sems;
L
Linus Torvalds 已提交
933 934 935 936
		} else {
			seminfo.semusz = SEMUSZ;
			seminfo.semaem = SEMAEM;
		}
N
Nadia Derbey 已提交
937
		max_id = ipc_get_maxid(&sem_ids(ns));
N
Nadia Derbey 已提交
938
		up_read(&sem_ids(ns).rw_mutex);
939
		if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) 
L
Linus Torvalds 已提交
940 941 942
			return -EFAULT;
		return (max_id < 0) ? 0: max_id;
	}
943
	case IPC_STAT:
L
Linus Torvalds 已提交
944 945 946
	case SEM_STAT:
	{
		struct semid64_ds tbuf;
947 948 949
		int id = 0;

		memset(&tbuf, 0, sizeof(tbuf));
L
Linus Torvalds 已提交
950

951
		if (cmd == SEM_STAT) {
952 953 954 955 956 957
			rcu_read_lock();
			sma = sem_obtain_object(ns, semid);
			if (IS_ERR(sma)) {
				err = PTR_ERR(sma);
				goto out_unlock;
			}
958 959
			id = sma->sem_perm.id;
		} else {
960 961 962 963 964 965
			rcu_read_lock();
			sma = sem_obtain_object_check(ns, semid);
			if (IS_ERR(sma)) {
				err = PTR_ERR(sma);
				goto out_unlock;
			}
966
		}
L
Linus Torvalds 已提交
967 968

		err = -EACCES;
969
		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
L
Linus Torvalds 已提交
970 971 972 973 974 975 976 977 978 979
			goto out_unlock;

		err = security_sem_semctl(sma, cmd);
		if (err)
			goto out_unlock;

		kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
		tbuf.sem_otime  = sma->sem_otime;
		tbuf.sem_ctime  = sma->sem_ctime;
		tbuf.sem_nsems  = sma->sem_nsems;
980
		rcu_read_unlock();
981
		if (copy_semid_to_user(p, &tbuf, version))
L
Linus Torvalds 已提交
982 983 984 985 986 987 988
			return -EFAULT;
		return id;
	}
	default:
		return -EINVAL;
	}
out_unlock:
989
	rcu_read_unlock();
L
Linus Torvalds 已提交
990 991 992
	return err;
}

993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009
static int semctl_setval(struct ipc_namespace *ns, int semid, int semnum,
		unsigned long arg)
{
	struct sem_undo *un;
	struct sem_array *sma;
	struct sem* curr;
	int err;
	struct list_head tasks;
	int val;
#if defined(CONFIG_64BIT) && defined(__BIG_ENDIAN)
	/* big-endian 64bit */
	val = arg >> 32;
#else
	/* 32bit or little-endian 64bit */
	val = arg;
#endif

1010 1011
	if (val > SEMVMX || val < 0)
		return -ERANGE;
1012 1013 1014

	INIT_LIST_HEAD(&tasks);

1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031
	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;
	}
1032 1033

	err = security_sem_semctl(sma, SETVAL);
1034 1035 1036 1037
	if (err) {
		rcu_read_unlock();
		return -EACCES;
	}
1038

1039
	sem_lock(sma, NULL, -1);
1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051

	curr = &sma->sem_base[semnum];

	assert_spin_locked(&sma->sem_perm.lock);
	list_for_each_entry(un, &sma->list_id, list_id)
		un->semadj[semnum] = 0;

	curr->semval = val;
	curr->sempid = task_tgid_vnr(current);
	sma->sem_ctime = get_seconds();
	/* maybe some queued-up processes were waiting for this */
	do_smart_update(sma, NULL, 0, 0, &tasks);
1052
	sem_unlock(sma, -1);
1053
	rcu_read_unlock();
1054
	wake_up_sem_queue_do(&tasks);
1055
	return 0;
1056 1057
}

K
Kirill Korotaev 已提交
1058
static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1059
		int cmd, void __user *p)
L
Linus Torvalds 已提交
1060 1061 1062
{
	struct sem_array *sma;
	struct sem* curr;
1063
	int err, nsems;
L
Linus Torvalds 已提交
1064 1065
	ushort fast_sem_io[SEMMSL_FAST];
	ushort* sem_io = fast_sem_io;
1066
	struct list_head tasks;
L
Linus Torvalds 已提交
1067

1068 1069 1070 1071 1072 1073
	INIT_LIST_HEAD(&tasks);

	rcu_read_lock();
	sma = sem_obtain_object_check(ns, semid);
	if (IS_ERR(sma)) {
		rcu_read_unlock();
1074
		return PTR_ERR(sma);
1075
	}
L
Linus Torvalds 已提交
1076 1077 1078 1079

	nsems = sma->sem_nsems;

	err = -EACCES;
1080
	if (ipcperms(ns, &sma->sem_perm,
1081 1082 1083 1084
			cmd == SETALL ? S_IWUGO : S_IRUGO)) {
		rcu_read_unlock();
		goto out_wakeup;
	}
L
Linus Torvalds 已提交
1085 1086

	err = security_sem_semctl(sma, cmd);
1087 1088 1089 1090
	if (err) {
		rcu_read_unlock();
		goto out_wakeup;
	}
L
Linus Torvalds 已提交
1091 1092 1093 1094 1095

	err = -EACCES;
	switch (cmd) {
	case GETALL:
	{
1096
		ushort __user *array = p;
L
Linus Torvalds 已提交
1097 1098
		int i;

1099
		sem_lock(sma, NULL, -1);
L
Linus Torvalds 已提交
1100
		if(nsems > SEMMSL_FAST) {
1101 1102
			if (!ipc_rcu_getref(sma)) {
				sem_unlock(sma, -1);
1103
				rcu_read_unlock();
1104 1105 1106 1107
				err = -EIDRM;
				goto out_free;
			}
			sem_unlock(sma, -1);
1108
			rcu_read_unlock();
L
Linus Torvalds 已提交
1109 1110
			sem_io = ipc_alloc(sizeof(ushort)*nsems);
			if(sem_io == NULL) {
1111
				sem_putref(sma);
L
Linus Torvalds 已提交
1112 1113 1114
				return -ENOMEM;
			}

1115
			rcu_read_lock();
1116
			sem_lock_and_putref(sma);
L
Linus Torvalds 已提交
1117
			if (sma->sem_perm.deleted) {
1118
				sem_unlock(sma, -1);
1119
				rcu_read_unlock();
L
Linus Torvalds 已提交
1120 1121 1122
				err = -EIDRM;
				goto out_free;
			}
1123
		}
L
Linus Torvalds 已提交
1124 1125
		for (i = 0; i < sma->sem_nsems; i++)
			sem_io[i] = sma->sem_base[i].semval;
1126
		sem_unlock(sma, -1);
1127
		rcu_read_unlock();
L
Linus Torvalds 已提交
1128 1129 1130 1131 1132 1133 1134 1135 1136 1137
		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;

1138 1139 1140 1141
		if (!ipc_rcu_getref(sma)) {
			rcu_read_unlock();
			return -EIDRM;
		}
1142
		rcu_read_unlock();
L
Linus Torvalds 已提交
1143 1144 1145 1146

		if(nsems > SEMMSL_FAST) {
			sem_io = ipc_alloc(sizeof(ushort)*nsems);
			if(sem_io == NULL) {
1147
				sem_putref(sma);
L
Linus Torvalds 已提交
1148 1149 1150 1151
				return -ENOMEM;
			}
		}

1152
		if (copy_from_user (sem_io, p, nsems*sizeof(ushort))) {
1153
			sem_putref(sma);
L
Linus Torvalds 已提交
1154 1155 1156 1157 1158 1159
			err = -EFAULT;
			goto out_free;
		}

		for (i = 0; i < nsems; i++) {
			if (sem_io[i] > SEMVMX) {
1160
				sem_putref(sma);
L
Linus Torvalds 已提交
1161 1162 1163 1164
				err = -ERANGE;
				goto out_free;
			}
		}
1165
		rcu_read_lock();
1166
		sem_lock_and_putref(sma);
L
Linus Torvalds 已提交
1167
		if (sma->sem_perm.deleted) {
1168
			sem_unlock(sma, -1);
1169
			rcu_read_unlock();
L
Linus Torvalds 已提交
1170 1171 1172 1173 1174 1175
			err = -EIDRM;
			goto out_free;
		}

		for (i = 0; i < nsems; i++)
			sma->sem_base[i].semval = sem_io[i];
1176 1177 1178

		assert_spin_locked(&sma->sem_perm.lock);
		list_for_each_entry(un, &sma->list_id, list_id) {
L
Linus Torvalds 已提交
1179 1180
			for (i = 0; i < nsems; i++)
				un->semadj[i] = 0;
1181
		}
L
Linus Torvalds 已提交
1182 1183
		sma->sem_ctime = get_seconds();
		/* maybe some queued-up processes were waiting for this */
1184
		do_smart_update(sma, NULL, 0, 0, &tasks);
L
Linus Torvalds 已提交
1185 1186 1187
		err = 0;
		goto out_unlock;
	}
1188
	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
L
Linus Torvalds 已提交
1189 1190
	}
	err = -EINVAL;
1191 1192 1193 1194
	if (semnum < 0 || semnum >= nsems) {
		rcu_read_unlock();
		goto out_wakeup;
	}
L
Linus Torvalds 已提交
1195

1196
	sem_lock(sma, NULL, -1);
L
Linus Torvalds 已提交
1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212
	curr = &sma->sem_base[semnum];

	switch (cmd) {
	case GETVAL:
		err = curr->semval;
		goto out_unlock;
	case GETPID:
		err = curr->sempid;
		goto out_unlock;
	case GETNCNT:
		err = count_semncnt(sma,semnum);
		goto out_unlock;
	case GETZCNT:
		err = count_semzcnt(sma,semnum);
		goto out_unlock;
	}
1213

L
Linus Torvalds 已提交
1214
out_unlock:
1215
	sem_unlock(sma, -1);
1216
	rcu_read_unlock();
1217
out_wakeup:
1218
	wake_up_sem_queue_do(&tasks);
L
Linus Torvalds 已提交
1219 1220 1221 1222 1223 1224
out_free:
	if(sem_io != fast_sem_io)
		ipc_free(sem_io, sizeof(ushort)*nsems);
	return err;
}

1225 1226
static inline unsigned long
copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
L
Linus Torvalds 已提交
1227 1228 1229
{
	switch(version) {
	case IPC_64:
1230
		if (copy_from_user(out, buf, sizeof(*out)))
L
Linus Torvalds 已提交
1231 1232 1233 1234 1235 1236 1237 1238 1239
			return -EFAULT;
		return 0;
	case IPC_OLD:
	    {
		struct semid_ds tbuf_old;

		if(copy_from_user(&tbuf_old, buf, sizeof(tbuf_old)))
			return -EFAULT;

1240 1241 1242
		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;
L
Linus Torvalds 已提交
1243 1244 1245 1246 1247 1248 1249 1250

		return 0;
	    }
	default:
		return -EINVAL;
	}
}

1251 1252 1253 1254 1255
/*
 * This function handles some semctl commands which require the rw_mutex
 * to be held in write mode.
 * NOTE: no locks must be held, the rw_mutex is taken inside this function.
 */
1256
static int semctl_down(struct ipc_namespace *ns, int semid,
1257
		       int cmd, int version, void __user *p)
L
Linus Torvalds 已提交
1258 1259 1260
{
	struct sem_array *sma;
	int err;
1261
	struct semid64_ds semid64;
L
Linus Torvalds 已提交
1262 1263 1264
	struct kern_ipc_perm *ipcp;

	if(cmd == IPC_SET) {
1265
		if (copy_semid_from_user(&semid64, p, version))
L
Linus Torvalds 已提交
1266 1267
			return -EFAULT;
	}
S
Steve Grubb 已提交
1268

1269 1270
	ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
				      &semid64.sem_perm, 0);
1271 1272
	if (IS_ERR(ipcp))
		return PTR_ERR(ipcp);
S
Steve Grubb 已提交
1273

1274
	sma = container_of(ipcp, struct sem_array, sem_perm);
L
Linus Torvalds 已提交
1275 1276

	err = security_sem_semctl(sma, cmd);
1277 1278
	if (err) {
		rcu_read_unlock();
1279
		goto out_up;
1280
	}
L
Linus Torvalds 已提交
1281 1282 1283

	switch(cmd){
	case IPC_RMID:
1284
		sem_lock(sma, NULL, -1);
1285
		freeary(ns, ipcp);
1286
		goto out_up;
L
Linus Torvalds 已提交
1287
	case IPC_SET:
1288
		sem_lock(sma, NULL, -1);
1289 1290 1291
		err = ipc_update_perm(&semid64.sem_perm, ipcp);
		if (err)
			goto out_unlock;
L
Linus Torvalds 已提交
1292 1293 1294
		sma->sem_ctime = get_seconds();
		break;
	default:
1295
		rcu_read_unlock();
L
Linus Torvalds 已提交
1296
		err = -EINVAL;
1297
		goto out_up;
L
Linus Torvalds 已提交
1298 1299 1300
	}

out_unlock:
1301
	sem_unlock(sma, -1);
1302
	rcu_read_unlock();
1303 1304
out_up:
	up_write(&sem_ids(ns).rw_mutex);
L
Linus Torvalds 已提交
1305 1306 1307
	return err;
}

1308
SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
L
Linus Torvalds 已提交
1309 1310
{
	int version;
K
Kirill Korotaev 已提交
1311
	struct ipc_namespace *ns;
1312
	void __user *p = (void __user *)arg;
L
Linus Torvalds 已提交
1313 1314 1315 1316 1317

	if (semid < 0)
		return -EINVAL;

	version = ipc_parse_version(&cmd);
K
Kirill Korotaev 已提交
1318
	ns = current->nsproxy->ipc_ns;
L
Linus Torvalds 已提交
1319 1320 1321 1322

	switch(cmd) {
	case IPC_INFO:
	case SEM_INFO:
1323
	case IPC_STAT:
L
Linus Torvalds 已提交
1324
	case SEM_STAT:
1325
		return semctl_nolock(ns, semid, cmd, version, p);
L
Linus Torvalds 已提交
1326 1327 1328 1329 1330 1331
	case GETALL:
	case GETVAL:
	case GETPID:
	case GETNCNT:
	case GETZCNT:
	case SETALL:
1332 1333 1334
		return semctl_main(ns, semid, semnum, cmd, p);
	case SETVAL:
		return semctl_setval(ns, semid, semnum, arg);
L
Linus Torvalds 已提交
1335 1336
	case IPC_RMID:
	case IPC_SET:
1337
		return semctl_down(ns, semid, cmd, version, p);
L
Linus Torvalds 已提交
1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359
	default:
		return -EINVAL;
	}
}

/* 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) {
1360
		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
L
Linus Torvalds 已提交
1361 1362
		if (undo_list == NULL)
			return -ENOMEM;
I
Ingo Molnar 已提交
1363
		spin_lock_init(&undo_list->lock);
L
Linus Torvalds 已提交
1364
		atomic_set(&undo_list->refcnt, 1);
1365 1366
		INIT_LIST_HEAD(&undo_list->list_proc);

L
Linus Torvalds 已提交
1367 1368 1369 1370 1371 1372
		current->sysvsem.undo_list = undo_list;
	}
	*undo_listp = undo_list;
	return 0;
}

1373
static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
L
Linus Torvalds 已提交
1374
{
1375
	struct sem_undo *un;
1376

1377 1378 1379
	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
		if (un->semid == semid)
			return un;
L
Linus Torvalds 已提交
1380
	}
1381
	return NULL;
L
Linus Torvalds 已提交
1382 1383
}

1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397
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;
}

1398 1399 1400 1401 1402 1403 1404 1405
/**
 * 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.
1406 1407
 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
 * performs a rcu_read_lock().
1408 1409
 */
static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
L
Linus Torvalds 已提交
1410 1411 1412 1413
{
	struct sem_array *sma;
	struct sem_undo_list *ulp;
	struct sem_undo *un, *new;
1414
	int nsems, error;
L
Linus Torvalds 已提交
1415 1416 1417 1418 1419

	error = get_undo_list(&ulp);
	if (error)
		return ERR_PTR(error);

1420
	rcu_read_lock();
1421
	spin_lock(&ulp->lock);
L
Linus Torvalds 已提交
1422
	un = lookup_undo(ulp, semid);
1423
	spin_unlock(&ulp->lock);
L
Linus Torvalds 已提交
1424 1425 1426 1427
	if (likely(un!=NULL))
		goto out;

	/* no undo structure around - allocate one. */
1428
	/* step 1: figure out the size of the semaphore array */
1429 1430 1431
	sma = sem_obtain_object_check(ns, semid);
	if (IS_ERR(sma)) {
		rcu_read_unlock();
J
Julia Lawall 已提交
1432
		return ERR_CAST(sma);
1433
	}
1434

L
Linus Torvalds 已提交
1435
	nsems = sma->sem_nsems;
1436 1437 1438 1439 1440
	if (!ipc_rcu_getref(sma)) {
		rcu_read_unlock();
		un = ERR_PTR(-EIDRM);
		goto out;
	}
1441
	rcu_read_unlock();
L
Linus Torvalds 已提交
1442

1443
	/* step 2: allocate new undo structure */
1444
	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
L
Linus Torvalds 已提交
1445
	if (!new) {
1446
		sem_putref(sma);
L
Linus Torvalds 已提交
1447 1448 1449
		return ERR_PTR(-ENOMEM);
	}

1450
	/* step 3: Acquire the lock on semaphore array */
1451
	rcu_read_lock();
1452
	sem_lock_and_putref(sma);
L
Linus Torvalds 已提交
1453
	if (sma->sem_perm.deleted) {
1454
		sem_unlock(sma, -1);
1455
		rcu_read_unlock();
L
Linus Torvalds 已提交
1456 1457 1458 1459
		kfree(new);
		un = ERR_PTR(-EIDRM);
		goto out;
	}
1460 1461 1462 1463 1464 1465 1466 1467 1468 1469
	spin_lock(&ulp->lock);

	/*
	 * step 4: check for races: did someone else allocate the undo struct?
	 */
	un = lookup_undo(ulp, semid);
	if (un) {
		kfree(new);
		goto success;
	}
1470 1471
	/* step 5: initialize & link new undo structure */
	new->semadj = (short *) &new[1];
1472
	new->ulp = ulp;
1473 1474
	new->semid = semid;
	assert_spin_locked(&ulp->lock);
1475
	list_add_rcu(&new->list_proc, &ulp->list_proc);
1476 1477
	assert_spin_locked(&sma->sem_perm.lock);
	list_add(&new->list_id, &sma->list_id);
1478
	un = new;
1479

1480
success:
1481
	spin_unlock(&ulp->lock);
1482
	sem_unlock(sma, -1);
L
Linus Torvalds 已提交
1483 1484 1485 1486
out:
	return un;
}

1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513

/**
 * get_queue_result - Retrieve the result code from sem_queue
 * @q: Pointer to queue structure
 *
 * Retrieve the return code from the pending queue. If IN_WAKEUP is found in
 * q->status, then we must loop until the value is replaced with the final
 * value: This may happen if a task is woken up by an unrelated event (e.g.
 * signal) and in parallel the task is woken up by another task because it got
 * the requested semaphores.
 *
 * The function can be called with or without holding the semaphore spinlock.
 */
static int get_queue_result(struct sem_queue *q)
{
	int error;

	error = q->status;
	while (unlikely(error == IN_WAKEUP)) {
		cpu_relax();
		error = q->status;
	}

	return error;
}


1514 1515
SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
		unsigned, nsops, const struct timespec __user *, timeout)
L
Linus Torvalds 已提交
1516 1517 1518 1519 1520 1521
{
	int error = -EINVAL;
	struct sem_array *sma;
	struct sembuf fast_sops[SEMOPM_FAST];
	struct sembuf* sops = fast_sops, *sop;
	struct sem_undo *un;
1522
	int undos = 0, alter = 0, max, locknum;
L
Linus Torvalds 已提交
1523 1524
	struct sem_queue queue;
	unsigned long jiffies_left = 0;
K
Kirill Korotaev 已提交
1525
	struct ipc_namespace *ns;
1526
	struct list_head tasks;
K
Kirill Korotaev 已提交
1527 1528

	ns = current->nsproxy->ipc_ns;
L
Linus Torvalds 已提交
1529 1530 1531

	if (nsops < 1 || semid < 0)
		return -EINVAL;
K
Kirill Korotaev 已提交
1532
	if (nsops > ns->sc_semopm)
L
Linus Torvalds 已提交
1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560
		return -E2BIG;
	if(nsops > SEMOPM_FAST) {
		sops = kmalloc(sizeof(*sops)*nsops,GFP_KERNEL);
		if(sops==NULL)
			return -ENOMEM;
	}
	if (copy_from_user (sops, tsops, nsops * sizeof(*tsops))) {
		error=-EFAULT;
		goto out_free;
	}
	if (timeout) {
		struct timespec _timeout;
		if (copy_from_user(&_timeout, timeout, sizeof(*timeout))) {
			error = -EFAULT;
			goto out_free;
		}
		if (_timeout.tv_sec < 0 || _timeout.tv_nsec < 0 ||
			_timeout.tv_nsec >= 1000000000L) {
			error = -EINVAL;
			goto out_free;
		}
		jiffies_left = timespec_to_jiffies(&_timeout);
	}
	max = 0;
	for (sop = sops; sop < sops + nsops; sop++) {
		if (sop->sem_num >= max)
			max = sop->sem_num;
		if (sop->sem_flg & SEM_UNDO)
1561 1562
			undos = 1;
		if (sop->sem_op != 0)
L
Linus Torvalds 已提交
1563 1564 1565
			alter = 1;
	}

1566 1567
	INIT_LIST_HEAD(&tasks);

L
Linus Torvalds 已提交
1568
	if (undos) {
1569
		/* On success, find_alloc_undo takes the rcu_read_lock */
1570
		un = find_alloc_undo(ns, semid);
L
Linus Torvalds 已提交
1571 1572 1573 1574
		if (IS_ERR(un)) {
			error = PTR_ERR(un);
			goto out_free;
		}
1575
	} else {
L
Linus Torvalds 已提交
1576
		un = NULL;
1577 1578
		rcu_read_lock();
	}
L
Linus Torvalds 已提交
1579

1580
	sma = sem_obtain_object_check(ns, semid);
1581
	if (IS_ERR(sma)) {
1582
		rcu_read_unlock();
1583
		error = PTR_ERR(sma);
L
Linus Torvalds 已提交
1584
		goto out_free;
1585 1586
	}

1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604
	error = -EFBIG;
	if (max >= sma->sem_nsems) {
		rcu_read_unlock();
		goto out_wakeup;
	}

	error = -EACCES;
	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO)) {
		rcu_read_unlock();
		goto out_wakeup;
	}

	error = security_sem_semop(sma, sops, nsops, alter);
	if (error) {
		rcu_read_unlock();
		goto out_wakeup;
	}

L
Linus Torvalds 已提交
1605
	/*
1606
	 * semid identifiers are not unique - find_alloc_undo may have
L
Linus Torvalds 已提交
1607
	 * allocated an undo structure, it was invalidated by an RMID
1608
	 * and now a new array with received the same id. Check and fail.
L
Lucas De Marchi 已提交
1609
	 * This case can be detected checking un->semid. The existence of
1610
	 * "un" itself is guaranteed by rcu.
L
Linus Torvalds 已提交
1611
	 */
1612
	error = -EIDRM;
1613 1614 1615
	locknum = sem_lock(sma, sops, nsops);
	if (un && un->semid == -1)
		goto out_unlock_free;
1616

1617
	error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
L
Linus Torvalds 已提交
1618 1619
	if (error <= 0) {
		if (alter && error == 0)
1620
			do_smart_update(sma, sops, nsops, 1, &tasks);
1621

L
Linus Torvalds 已提交
1622 1623 1624 1625 1626 1627 1628 1629 1630 1631
		goto out_unlock_free;
	}

	/* We need to sleep on this operation, so we put the current
	 * task into the pending queue and go to sleep.
	 */
		
	queue.sops = sops;
	queue.nsops = nsops;
	queue.undo = un;
1632
	queue.pid = task_tgid_vnr(current);
L
Linus Torvalds 已提交
1633 1634
	queue.alter = alter;

1635 1636 1637 1638 1639
	if (nsops == 1) {
		struct sem *curr;
		curr = &sma->sem_base[sops->sem_num];

		if (alter)
1640
			list_add_tail(&queue.list, &curr->sem_pending);
1641
		else
1642
			list_add(&queue.list, &curr->sem_pending);
1643
	} else {
1644 1645 1646 1647
		if (alter)
			list_add_tail(&queue.list, &sma->sem_pending);
		else
			list_add(&queue.list, &sma->sem_pending);
1648 1649 1650
		sma->complex_count++;
	}

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Linus Torvalds 已提交
1651 1652
	queue.status = -EINTR;
	queue.sleeper = current;
1653 1654

sleep_again:
L
Linus Torvalds 已提交
1655
	current->state = TASK_INTERRUPTIBLE;
1656
	sem_unlock(sma, locknum);
1657
	rcu_read_unlock();
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1658 1659 1660 1661 1662 1663

	if (timeout)
		jiffies_left = schedule_timeout(jiffies_left);
	else
		schedule();

1664
	error = get_queue_result(&queue);
L
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1665 1666 1667

	if (error != -EINTR) {
		/* fast path: update_queue already obtained all requested
1668 1669 1670 1671 1672 1673 1674 1675
		 * resources.
		 * Perform a smp_mb(): User space could assume that semop()
		 * is a memory barrier: Without the mb(), the cpu could
		 * speculatively read in user space stale data that was
		 * overwritten by the previous owner of the semaphore.
		 */
		smp_mb();

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Linus Torvalds 已提交
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		goto out_free;
	}

1679
	rcu_read_lock();
1680
	sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1681 1682 1683 1684 1685 1686 1687 1688 1689

	/*
	 * Wait until it's guaranteed that no wakeup_sem_queue_do() is ongoing.
	 */
	error = get_queue_result(&queue);

	/*
	 * Array removed? If yes, leave without sem_unlock().
	 */
1690
	if (IS_ERR(sma)) {
1691
		rcu_read_unlock();
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		goto out_free;
	}

1695

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1696
	/*
1697 1698
	 * If queue.status != -EINTR we are woken up by another process.
	 * Leave without unlink_queue(), but with sem_unlock().
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Linus Torvalds 已提交
1699
	 */
1700

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	if (error != -EINTR) {
		goto out_unlock_free;
	}

	/*
	 * If an interrupt occurred we have to clean up the queue
	 */
	if (timeout && jiffies_left == 0)
		error = -EAGAIN;
1710 1711 1712 1713 1714 1715 1716

	/*
	 * If the wakeup was spurious, just retry
	 */
	if (error == -EINTR && !signal_pending(current))
		goto sleep_again;

1717
	unlink_queue(sma, &queue);
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Linus Torvalds 已提交
1718 1719

out_unlock_free:
1720
	sem_unlock(sma, locknum);
1721
	rcu_read_unlock();
1722
out_wakeup:
1723
	wake_up_sem_queue_do(&tasks);
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out_free:
	if(sops != fast_sops)
		kfree(sops);
	return error;
}

1730 1731
SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
		unsigned, nsops)
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{
	return sys_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;
		atomic_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)
{
1771
	struct sem_undo_list *ulp;
L
Linus Torvalds 已提交
1772

1773 1774
	ulp = tsk->sysvsem.undo_list;
	if (!ulp)
L
Linus Torvalds 已提交
1775
		return;
1776
	tsk->sysvsem.undo_list = NULL;
L
Linus Torvalds 已提交
1777

1778
	if (!atomic_dec_and_test(&ulp->refcnt))
L
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1779 1780
		return;

1781
	for (;;) {
L
Linus Torvalds 已提交
1782
		struct sem_array *sma;
1783
		struct sem_undo *un;
1784
		struct list_head tasks;
1785
		int semid, i;
1786

1787
		rcu_read_lock();
1788 1789
		un = list_entry_rcu(ulp->list_proc.next,
				    struct sem_undo, list_proc);
1790 1791 1792 1793
		if (&un->list_proc == &ulp->list_proc)
			semid = -1;
		 else
			semid = un->semid;
1794

1795 1796
		if (semid == -1) {
			rcu_read_unlock();
1797
			break;
1798
		}
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Linus Torvalds 已提交
1799

1800
		sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
1801
		/* exit_sem raced with IPC_RMID, nothing to do */
1802 1803
		if (IS_ERR(sma)) {
			rcu_read_unlock();
1804
			continue;
1805
		}
L
Linus Torvalds 已提交
1806

1807
		sem_lock(sma, NULL, -1);
1808
		un = __lookup_undo(ulp, semid);
1809 1810 1811 1812
		if (un == NULL) {
			/* exit_sem raced with IPC_RMID+semget() that created
			 * exactly the same semid. Nothing to do.
			 */
1813
			sem_unlock(sma, -1);
1814
			rcu_read_unlock();
1815 1816 1817 1818
			continue;
		}

		/* remove un from the linked lists */
1819 1820 1821
		assert_spin_locked(&sma->sem_perm.lock);
		list_del(&un->list_id);

1822 1823 1824 1825
		spin_lock(&ulp->lock);
		list_del_rcu(&un->list_proc);
		spin_unlock(&ulp->lock);

1826 1827
		/* perform adjustments registered in un */
		for (i = 0; i < sma->sem_nsems; i++) {
I
Ingo Molnar 已提交
1828
			struct sem * semaphore = &sma->sem_base[i];
1829 1830
			if (un->semadj[i]) {
				semaphore->semval += un->semadj[i];
L
Linus Torvalds 已提交
1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843
				/*
				 * 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>
				 */
I
Ingo Molnar 已提交
1844 1845 1846 1847
				if (semaphore->semval < 0)
					semaphore->semval = 0;
				if (semaphore->semval > SEMVMX)
					semaphore->semval = SEMVMX;
1848
				semaphore->sempid = task_tgid_vnr(current);
L
Linus Torvalds 已提交
1849 1850 1851
			}
		}
		/* maybe some queued-up processes were waiting for this */
1852 1853
		INIT_LIST_HEAD(&tasks);
		do_smart_update(sma, NULL, 0, 1, &tasks);
1854
		sem_unlock(sma, -1);
1855
		rcu_read_unlock();
1856
		wake_up_sem_queue_do(&tasks);
1857

1858
		kfree_rcu(un, rcu);
L
Linus Torvalds 已提交
1859
	}
1860
	kfree(ulp);
L
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1861 1862 1863
}

#ifdef CONFIG_PROC_FS
1864
static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
L
Linus Torvalds 已提交
1865
{
1866
	struct user_namespace *user_ns = seq_user_ns(s);
1867 1868 1869
	struct sem_array *sma = it;

	return seq_printf(s,
1870
			  "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
1871
			  sma->sem_perm.key,
N
Nadia Derbey 已提交
1872
			  sma->sem_perm.id,
1873 1874
			  sma->sem_perm.mode,
			  sma->sem_nsems,
1875 1876 1877 1878
			  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),
1879 1880
			  sma->sem_otime,
			  sma->sem_ctime);
L
Linus Torvalds 已提交
1881 1882
}
#endif