sem.c 52.3 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 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*/
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	time_t	sem_otime;	/* candidate for sem_otime */
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} ____cacheline_aligned_in_smp;
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/* 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 */

/*
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 * Locking:
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 *	sem_undo.id_next,
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 *	sem_array.complex_count,
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 *	sem_array.pending{_alter,_cont},
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 *	sem_array.sem_undo: global sem_lock() for read/write
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 *	sem_undo.proc_next: only "current" is allowed to read/write that field.
 *	
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 *	sem_array.sem_base[i].pending_{const,alter}:
 *		global or semaphore sem_lock() for read/write
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 */

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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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/**
 * 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->sem_base[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->sem_base + i;

		list_splice_init(&sem->pending_alter, &sma->pending_alter);
	}
}

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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:
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		ipc_lock_object(&sma->sem_perm);
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		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) {
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		unmerge_queues(sma);
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		ipc_unlock_object(&sma->sem_perm);
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	} 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
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 *	* unlinking the queue entry from the pending list
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 *	* 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].pending_alter);
		INIT_LIST_HEAD(&sma->sem_base[i].pending_const);
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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->pending_alter);
	INIT_LIST_HEAD(&sma->pending_const);
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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;
L
Linus Torvalds 已提交
538

N
Nadia Derbey 已提交
539
	return ipcget(ns, &sem_ids(ns), &sem_ops, &sem_params);
L
Linus Torvalds 已提交
540 541
}

542 543 544 545 546 547 548 549 550 551
/** perform_atomic_semop - Perform (if possible) a semaphore operation
 * @sma: semaphore array
 * @sops: array with operations that should be checked
 * @nsems: number of sops
 * @un: undo array
 * @pid: pid that did the change
 *
 * Returns 0 if the operation was possible.
 * Returns 1 if the operation is impossible, the caller must sleep.
 * Negative values are error codes.
L
Linus Torvalds 已提交
552 553
 */

554
static int perform_atomic_semop(struct sem_array *sma, struct sembuf *sops,
L
Linus Torvalds 已提交
555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614
			     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;
}

615 616 617 618 619
/** 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
620
 */
621 622
static void wake_up_sem_queue_prepare(struct list_head *pt,
				struct sem_queue *q, int error)
N
Nick Piggin 已提交
623
{
624 625 626 627 628 629 630
	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
631
	q->status = IN_WAKEUP;
632 633
	q->pid = error;

634
	list_add_tail(&q->list, pt);
635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651
}

/**
 * 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);
652
	list_for_each_entry_safe(q, t, pt, list) {
653 654 655 656 657 658 659
		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
660 661
}

662 663 664
static void unlink_queue(struct sem_array *sma, struct sem_queue *q)
{
	list_del(&q->list);
665
	if (q->nsops > 1)
666 667 668
		sma->complex_count--;
}

669 670 671 672 673 674 675
/** 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
676 677
 * modified the array.
 * Note that wait-for-zero operations are handled without restart.
678 679 680
 */
static int check_restart(struct sem_array *sma, struct sem_queue *q)
{
681 682
	/* pending complex alter operations are too difficult to analyse */
	if (!list_empty(&sma->pending_alter))
683 684 685 686 687 688
		return 1;

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

689 690 691 692 693 694 695 696 697 698 699 700 701
	/* It is impossible that someone waits for the new value:
	 * - complex operations always restart.
	 * - wait-for-zero are handled seperately.
	 * - 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;
}
702

703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728
/**
 * wake_const_ops(sma, semnum, pt) - Wake up non-alter tasks
 * @sma: semaphore array.
 * @semnum: semaphore that was modified.
 * @pt: list head for the tasks that must be woken up.
 *
 * 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 @pt. 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 list_head *pt)
{
	struct sem_queue *q;
	struct list_head *walk;
	struct list_head *pending_list;
	int semop_completed = 0;

	if (semnum == -1)
		pending_list = &sma->pending_const;
	else
		pending_list = &sma->sem_base[semnum].pending_const;
729

730 731 732 733 734 735 736
	walk = pending_list->next;
	while (walk != pending_list) {
		int error;

		q = container_of(walk, struct sem_queue, list);
		walk = walk->next;

737 738
		error = perform_atomic_semop(sma, q->sops, q->nsops,
						 q->undo, q->pid);
739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785

		if (error <= 0) {
			/* operation completed, remove from queue & wakeup */

			unlink_queue(sma, q);

			wake_up_sem_queue_prepare(pt, q, error);
			if (error == 0)
				semop_completed = 1;
		}
	}
	return semop_completed;
}

/**
 * do_smart_wakeup_zero(sma, sops, nsops, pt) - wakeup all wait for zero tasks
 * @sma: semaphore array
 * @sops: operations that were performed
 * @nsops: number of operations
 * @pt: list head of the tasks that must be woken up.
 *
 * do_smart_wakeup_zero() 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 list_head *pt)
{
	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->sem_base[num].semval == 0) {
				got_zero = 1;
				semop_completed |= wake_const_ops(sma, num, pt);
			}
		}
	} else {
		/*
		 * No sops means modified semaphores not known.
		 * Assume all were changed.
786
		 */
787 788 789 790 791 792
		for (i = 0; i < sma->sem_nsems; i++) {
			if (sma->sem_base[i].semval == 0) {
				got_zero = 1;
				semop_completed |= wake_const_ops(sma, i, pt);
			}
		}
793 794
	}
	/*
795 796
	 * If one of the modified semaphores got 0,
	 * then check the global queue, too.
797
	 */
798 799
	if (got_zero)
		semop_completed |= wake_const_ops(sma, -1, pt);
800

801
	return semop_completed;
802 803
}

804 805 806 807 808

/**
 * update_queue(sma, semnum): Look for tasks that can be completed.
 * @sma: semaphore array.
 * @semnum: semaphore that was modified.
809
 * @pt: list head for the tasks that must be woken up.
810 811
 *
 * update_queue must be called after a semaphore in a semaphore array
812 813 814
 * 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.
815 816
 * The tasks that must be woken up are added to @pt. The return code
 * is stored in q->pid.
817 818
 * The function internally checks if const operations can now succeed.
 *
819
 * The function return 1 if at least one semop was completed successfully.
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Linus Torvalds 已提交
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 */
821
static int update_queue(struct sem_array *sma, int semnum, struct list_head *pt)
L
Linus Torvalds 已提交
822
{
823 824 825
	struct sem_queue *q;
	struct list_head *walk;
	struct list_head *pending_list;
826
	int semop_completed = 0;
827

828
	if (semnum == -1)
829
		pending_list = &sma->pending_alter;
830
	else
831
		pending_list = &sma->sem_base[semnum].pending_alter;
N
Nick Piggin 已提交
832 833

again:
834 835
	walk = pending_list->next;
	while (walk != pending_list) {
836
		int error, restart;
837

838
		q = container_of(walk, struct sem_queue, list);
839
		walk = walk->next;
L
Linus Torvalds 已提交
840

841 842
		/* If we are scanning the single sop, per-semaphore list of
		 * one semaphore and that semaphore is 0, then it is not
843
		 * necessary to scan further: simple increments
844 845 846 847
		 * 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.
		 */
848
		if (semnum != -1 && sma->sem_base[semnum].semval == 0)
849 850
			break;

851
		error = perform_atomic_semop(sma, q->sops, q->nsops,
L
Linus Torvalds 已提交
852 853 854
					 q->undo, q->pid);

		/* Does q->sleeper still need to sleep? */
N
Nick Piggin 已提交
855 856 857
		if (error > 0)
			continue;

858
		unlink_queue(sma, q);
N
Nick Piggin 已提交
859

860
		if (error) {
861
			restart = 0;
862 863
		} else {
			semop_completed = 1;
864
			do_smart_wakeup_zero(sma, q->sops, q->nsops, pt);
865
			restart = check_restart(sma, q);
866
		}
867

868
		wake_up_sem_queue_prepare(pt, q, error);
869
		if (restart)
N
Nick Piggin 已提交
870
			goto again;
L
Linus Torvalds 已提交
871
	}
872
	return semop_completed;
L
Linus Torvalds 已提交
873 874
}

875 876
/**
 * do_smart_update(sma, sops, nsops, otime, pt) - optimized update_queue
877 878 879
 * @sma: semaphore array
 * @sops: operations that were performed
 * @nsops: number of operations
880 881
 * @otime: force setting otime
 * @pt: list head of the tasks that must be woken up.
882
 *
883 884
 * 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.
885 886 887
 * 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.
888
 */
889 890
static void do_smart_update(struct sem_array *sma, struct sembuf *sops, int nsops,
			int otime, struct list_head *pt)
891 892 893
{
	int i;

894 895
	otime |= do_smart_wakeup_zero(sma, sops, nsops, pt);

896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921
	if (!list_empty(&sma->pending_alter)) {
		/* semaphore array uses the global queue - just process it. */
		otime |= update_queue(sma, -1, pt);
	} 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, pt);
		} 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 wont 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, pt);
				}
922
			}
923
		}
924
	}
925 926 927 928 929 930 931 932
	if (otime) {
		if (sops == NULL) {
			sma->sem_base[0].sem_otime = get_seconds();
		} else {
			sma->sem_base[sops[0].sem_num].sem_otime =
								get_seconds();
		}
	}
933 934 935
}


L
Linus Torvalds 已提交
936 937 938 939 940 941 942 943 944 945 946 947 948 949 950
/* 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;
951
	list_for_each_entry(q, &sma->sem_base[semnum].pending_alter, list) {
R
Rik van Riel 已提交
952 953 954 955 956 957
		struct sembuf * sops = q->sops;
		BUG_ON(sops->sem_num != semnum);
		if ((sops->sem_op < 0) && !(sops->sem_flg & IPC_NOWAIT))
			semncnt++;
	}

958
	list_for_each_entry(q, &sma->pending_alter, list) {
L
Linus Torvalds 已提交
959 960 961 962 963 964 965 966 967 968 969
		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;
}
970

L
Linus Torvalds 已提交
971 972 973 974 975 976
static int count_semzcnt (struct sem_array * sma, ushort semnum)
{
	int semzcnt;
	struct sem_queue * q;

	semzcnt = 0;
977
	list_for_each_entry(q, &sma->sem_base[semnum].pending_const, list) {
R
Rik van Riel 已提交
978 979 980 981 982 983
		struct sembuf * sops = q->sops;
		BUG_ON(sops->sem_num != semnum);
		if ((sops->sem_op == 0) && !(sops->sem_flg & IPC_NOWAIT))
			semzcnt++;
	}

984
	list_for_each_entry(q, &sma->pending_const, list) {
L
Linus Torvalds 已提交
985 986 987 988 989 990 991 992 993 994 995 996
		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
997 998 999
/* 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
1000
 */
1001
static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
L
Linus Torvalds 已提交
1002
{
1003 1004
	struct sem_undo *un, *tu;
	struct sem_queue *q, *tq;
1005
	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
1006
	struct list_head tasks;
1007
	int i;
L
Linus Torvalds 已提交
1008

1009
	/* Free the existing undo structures for this semaphore set.  */
1010
	ipc_assert_locked_object(&sma->sem_perm);
1011 1012 1013
	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
1014
		un->semid = -1;
1015 1016
		list_del_rcu(&un->list_proc);
		spin_unlock(&un->ulp->lock);
1017
		kfree_rcu(un, rcu);
1018
	}
L
Linus Torvalds 已提交
1019 1020

	/* Wake up all pending processes and let them fail with EIDRM. */
1021
	INIT_LIST_HEAD(&tasks);
1022 1023 1024 1025 1026 1027
	list_for_each_entry_safe(q, tq, &sma->pending_const, list) {
		unlink_queue(sma, q);
		wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
	}

	list_for_each_entry_safe(q, tq, &sma->pending_alter, list) {
1028
		unlink_queue(sma, q);
1029
		wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
L
Linus Torvalds 已提交
1030
	}
1031 1032
	for (i = 0; i < sma->sem_nsems; i++) {
		struct sem *sem = sma->sem_base + i;
1033 1034 1035 1036 1037
		list_for_each_entry_safe(q, tq, &sem->pending_const, list) {
			unlink_queue(sma, q);
			wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
		}
		list_for_each_entry_safe(q, tq, &sem->pending_alter, list) {
1038 1039 1040 1041
			unlink_queue(sma, q);
			wake_up_sem_queue_prepare(&tasks, q, -EIDRM);
		}
	}
L
Linus Torvalds 已提交
1042

N
Nadia Derbey 已提交
1043 1044
	/* Remove the semaphore set from the IDR */
	sem_rmid(ns, sma);
1045
	sem_unlock(sma, -1);
1046
	rcu_read_unlock();
L
Linus Torvalds 已提交
1047

1048
	wake_up_sem_queue_do(&tasks);
K
Kirill Korotaev 已提交
1049
	ns->used_sems -= sma->sem_nsems;
L
Linus Torvalds 已提交
1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062
	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;

1063 1064
		memset(&out, 0, sizeof(out));

L
Linus Torvalds 已提交
1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077
		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;
	}
}

1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092
static time_t get_semotime(struct sem_array *sma)
{
	int i;
	time_t res;

	res = sma->sem_base[0].sem_otime;
	for (i = 1; i < sma->sem_nsems; i++) {
		time_t to = sma->sem_base[i].sem_otime;

		if (to > res)
			res = to;
	}
	return res;
}

1093
static int semctl_nolock(struct ipc_namespace *ns, int semid,
1094
			 int cmd, int version, void __user *p)
L
Linus Torvalds 已提交
1095
{
1096
	int err;
L
Linus Torvalds 已提交
1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110
	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
1111 1112 1113 1114
		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
1115 1116 1117 1118
		seminfo.semvmx = SEMVMX;
		seminfo.semmnu = SEMMNU;
		seminfo.semmap = SEMMAP;
		seminfo.semume = SEMUME;
N
Nadia Derbey 已提交
1119
		down_read(&sem_ids(ns).rw_mutex);
L
Linus Torvalds 已提交
1120
		if (cmd == SEM_INFO) {
K
Kirill Korotaev 已提交
1121 1122
			seminfo.semusz = sem_ids(ns).in_use;
			seminfo.semaem = ns->used_sems;
L
Linus Torvalds 已提交
1123 1124 1125 1126
		} else {
			seminfo.semusz = SEMUSZ;
			seminfo.semaem = SEMAEM;
		}
N
Nadia Derbey 已提交
1127
		max_id = ipc_get_maxid(&sem_ids(ns));
N
Nadia Derbey 已提交
1128
		up_read(&sem_ids(ns).rw_mutex);
1129
		if (copy_to_user(p, &seminfo, sizeof(struct seminfo))) 
L
Linus Torvalds 已提交
1130 1131 1132
			return -EFAULT;
		return (max_id < 0) ? 0: max_id;
	}
1133
	case IPC_STAT:
L
Linus Torvalds 已提交
1134 1135 1136
	case SEM_STAT:
	{
		struct semid64_ds tbuf;
1137 1138 1139
		int id = 0;

		memset(&tbuf, 0, sizeof(tbuf));
L
Linus Torvalds 已提交
1140

1141
		rcu_read_lock();
1142
		if (cmd == SEM_STAT) {
1143 1144 1145 1146 1147
			sma = sem_obtain_object(ns, semid);
			if (IS_ERR(sma)) {
				err = PTR_ERR(sma);
				goto out_unlock;
			}
1148 1149
			id = sma->sem_perm.id;
		} else {
1150 1151 1152 1153 1154
			sma = sem_obtain_object_check(ns, semid);
			if (IS_ERR(sma)) {
				err = PTR_ERR(sma);
				goto out_unlock;
			}
1155
		}
L
Linus Torvalds 已提交
1156 1157

		err = -EACCES;
1158
		if (ipcperms(ns, &sma->sem_perm, S_IRUGO))
L
Linus Torvalds 已提交
1159 1160 1161 1162 1163 1164 1165
			goto out_unlock;

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

		kernel_to_ipc64_perm(&sma->sem_perm, &tbuf.sem_perm);
1166 1167 1168
		tbuf.sem_otime = get_semotime(sma);
		tbuf.sem_ctime = sma->sem_ctime;
		tbuf.sem_nsems = sma->sem_nsems;
1169
		rcu_read_unlock();
1170
		if (copy_semid_to_user(p, &tbuf, version))
L
Linus Torvalds 已提交
1171 1172 1173 1174 1175 1176 1177
			return -EFAULT;
		return id;
	}
	default:
		return -EINVAL;
	}
out_unlock:
1178
	rcu_read_unlock();
L
Linus Torvalds 已提交
1179 1180 1181
	return err;
}

1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198
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

1199 1200
	if (val > SEMVMX || val < 0)
		return -ERANGE;
1201 1202 1203

	INIT_LIST_HEAD(&tasks);

1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220
	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;
	}
1221 1222

	err = security_sem_semctl(sma, SETVAL);
1223 1224 1225 1226
	if (err) {
		rcu_read_unlock();
		return -EACCES;
	}
1227

1228
	sem_lock(sma, NULL, -1);
1229 1230 1231

	curr = &sma->sem_base[semnum];

1232
	ipc_assert_locked_object(&sma->sem_perm);
1233 1234 1235 1236 1237 1238 1239 1240
	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);
1241
	sem_unlock(sma, -1);
1242
	rcu_read_unlock();
1243
	wake_up_sem_queue_do(&tasks);
1244
	return 0;
1245 1246
}

K
Kirill Korotaev 已提交
1247
static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
1248
		int cmd, void __user *p)
L
Linus Torvalds 已提交
1249 1250 1251
{
	struct sem_array *sma;
	struct sem* curr;
1252
	int err, nsems;
L
Linus Torvalds 已提交
1253 1254
	ushort fast_sem_io[SEMMSL_FAST];
	ushort* sem_io = fast_sem_io;
1255
	struct list_head tasks;
L
Linus Torvalds 已提交
1256

1257 1258 1259 1260 1261 1262
	INIT_LIST_HEAD(&tasks);

	rcu_read_lock();
	sma = sem_obtain_object_check(ns, semid);
	if (IS_ERR(sma)) {
		rcu_read_unlock();
1263
		return PTR_ERR(sma);
1264
	}
L
Linus Torvalds 已提交
1265 1266 1267 1268

	nsems = sma->sem_nsems;

	err = -EACCES;
1269 1270
	if (ipcperms(ns, &sma->sem_perm, cmd == SETALL ? S_IWUGO : S_IRUGO))
		goto out_rcu_wakeup;
L
Linus Torvalds 已提交
1271 1272

	err = security_sem_semctl(sma, cmd);
1273 1274
	if (err)
		goto out_rcu_wakeup;
L
Linus Torvalds 已提交
1275 1276 1277 1278 1279

	err = -EACCES;
	switch (cmd) {
	case GETALL:
	{
1280
		ushort __user *array = p;
L
Linus Torvalds 已提交
1281 1282
		int i;

1283
		sem_lock(sma, NULL, -1);
L
Linus Torvalds 已提交
1284
		if(nsems > SEMMSL_FAST) {
1285 1286
			if (!ipc_rcu_getref(sma)) {
				sem_unlock(sma, -1);
1287
				rcu_read_unlock();
1288 1289 1290 1291
				err = -EIDRM;
				goto out_free;
			}
			sem_unlock(sma, -1);
1292
			rcu_read_unlock();
L
Linus Torvalds 已提交
1293 1294
			sem_io = ipc_alloc(sizeof(ushort)*nsems);
			if(sem_io == NULL) {
1295
				sem_putref(sma);
L
Linus Torvalds 已提交
1296 1297 1298
				return -ENOMEM;
			}

1299
			rcu_read_lock();
1300
			sem_lock_and_putref(sma);
L
Linus Torvalds 已提交
1301
			if (sma->sem_perm.deleted) {
1302
				sem_unlock(sma, -1);
1303
				rcu_read_unlock();
L
Linus Torvalds 已提交
1304 1305 1306
				err = -EIDRM;
				goto out_free;
			}
1307
		}
L
Linus Torvalds 已提交
1308 1309
		for (i = 0; i < sma->sem_nsems; i++)
			sem_io[i] = sma->sem_base[i].semval;
1310
		sem_unlock(sma, -1);
1311
		rcu_read_unlock();
L
Linus Torvalds 已提交
1312 1313 1314 1315 1316 1317 1318 1319 1320 1321
		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;

1322 1323 1324 1325
		if (!ipc_rcu_getref(sma)) {
			rcu_read_unlock();
			return -EIDRM;
		}
1326
		rcu_read_unlock();
L
Linus Torvalds 已提交
1327 1328 1329 1330

		if(nsems > SEMMSL_FAST) {
			sem_io = ipc_alloc(sizeof(ushort)*nsems);
			if(sem_io == NULL) {
1331
				sem_putref(sma);
L
Linus Torvalds 已提交
1332 1333 1334 1335
				return -ENOMEM;
			}
		}

1336
		if (copy_from_user (sem_io, p, nsems*sizeof(ushort))) {
1337
			sem_putref(sma);
L
Linus Torvalds 已提交
1338 1339 1340 1341 1342 1343
			err = -EFAULT;
			goto out_free;
		}

		for (i = 0; i < nsems; i++) {
			if (sem_io[i] > SEMVMX) {
1344
				sem_putref(sma);
L
Linus Torvalds 已提交
1345 1346 1347 1348
				err = -ERANGE;
				goto out_free;
			}
		}
1349
		rcu_read_lock();
1350
		sem_lock_and_putref(sma);
L
Linus Torvalds 已提交
1351
		if (sma->sem_perm.deleted) {
1352
			sem_unlock(sma, -1);
1353
			rcu_read_unlock();
L
Linus Torvalds 已提交
1354 1355 1356 1357 1358 1359
			err = -EIDRM;
			goto out_free;
		}

		for (i = 0; i < nsems; i++)
			sma->sem_base[i].semval = sem_io[i];
1360

1361
		ipc_assert_locked_object(&sma->sem_perm);
1362
		list_for_each_entry(un, &sma->list_id, list_id) {
L
Linus Torvalds 已提交
1363 1364
			for (i = 0; i < nsems; i++)
				un->semadj[i] = 0;
1365
		}
L
Linus Torvalds 已提交
1366 1367
		sma->sem_ctime = get_seconds();
		/* maybe some queued-up processes were waiting for this */
1368
		do_smart_update(sma, NULL, 0, 0, &tasks);
L
Linus Torvalds 已提交
1369 1370 1371
		err = 0;
		goto out_unlock;
	}
1372
	/* GETVAL, GETPID, GETNCTN, GETZCNT: fall-through */
L
Linus Torvalds 已提交
1373 1374
	}
	err = -EINVAL;
1375 1376
	if (semnum < 0 || semnum >= nsems)
		goto out_rcu_wakeup;
L
Linus Torvalds 已提交
1377

1378
	sem_lock(sma, NULL, -1);
L
Linus Torvalds 已提交
1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394
	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;
	}
1395

L
Linus Torvalds 已提交
1396
out_unlock:
1397
	sem_unlock(sma, -1);
1398
out_rcu_wakeup:
1399
	rcu_read_unlock();
1400
	wake_up_sem_queue_do(&tasks);
L
Linus Torvalds 已提交
1401 1402 1403 1404 1405 1406
out_free:
	if(sem_io != fast_sem_io)
		ipc_free(sem_io, sizeof(ushort)*nsems);
	return err;
}

1407 1408
static inline unsigned long
copy_semid_from_user(struct semid64_ds *out, void __user *buf, int version)
L
Linus Torvalds 已提交
1409 1410 1411
{
	switch(version) {
	case IPC_64:
1412
		if (copy_from_user(out, buf, sizeof(*out)))
L
Linus Torvalds 已提交
1413 1414 1415 1416 1417 1418 1419 1420 1421
			return -EFAULT;
		return 0;
	case IPC_OLD:
	    {
		struct semid_ds tbuf_old;

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

1422 1423 1424
		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
1425 1426 1427 1428 1429 1430 1431 1432

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

1433 1434 1435 1436 1437
/*
 * 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.
 */
1438
static int semctl_down(struct ipc_namespace *ns, int semid,
1439
		       int cmd, int version, void __user *p)
L
Linus Torvalds 已提交
1440 1441 1442
{
	struct sem_array *sma;
	int err;
1443
	struct semid64_ds semid64;
L
Linus Torvalds 已提交
1444 1445 1446
	struct kern_ipc_perm *ipcp;

	if(cmd == IPC_SET) {
1447
		if (copy_semid_from_user(&semid64, p, version))
L
Linus Torvalds 已提交
1448 1449
			return -EFAULT;
	}
S
Steve Grubb 已提交
1450

1451 1452 1453
	down_write(&sem_ids(ns).rw_mutex);
	rcu_read_lock();

1454 1455
	ipcp = ipcctl_pre_down_nolock(ns, &sem_ids(ns), semid, cmd,
				      &semid64.sem_perm, 0);
1456 1457 1458 1459
	if (IS_ERR(ipcp)) {
		err = PTR_ERR(ipcp);
		goto out_unlock1;
	}
S
Steve Grubb 已提交
1460

1461
	sma = container_of(ipcp, struct sem_array, sem_perm);
L
Linus Torvalds 已提交
1462 1463

	err = security_sem_semctl(sma, cmd);
1464 1465
	if (err)
		goto out_unlock1;
L
Linus Torvalds 已提交
1466

1467
	switch (cmd) {
L
Linus Torvalds 已提交
1468
	case IPC_RMID:
1469
		sem_lock(sma, NULL, -1);
1470
		/* freeary unlocks the ipc object and rcu */
1471
		freeary(ns, ipcp);
1472
		goto out_up;
L
Linus Torvalds 已提交
1473
	case IPC_SET:
1474
		sem_lock(sma, NULL, -1);
1475 1476
		err = ipc_update_perm(&semid64.sem_perm, ipcp);
		if (err)
1477
			goto out_unlock0;
L
Linus Torvalds 已提交
1478 1479 1480 1481
		sma->sem_ctime = get_seconds();
		break;
	default:
		err = -EINVAL;
1482
		goto out_unlock1;
L
Linus Torvalds 已提交
1483 1484
	}

1485
out_unlock0:
1486
	sem_unlock(sma, -1);
1487
out_unlock1:
1488
	rcu_read_unlock();
1489 1490
out_up:
	up_write(&sem_ids(ns).rw_mutex);
L
Linus Torvalds 已提交
1491 1492 1493
	return err;
}

1494
SYSCALL_DEFINE4(semctl, int, semid, int, semnum, int, cmd, unsigned long, arg)
L
Linus Torvalds 已提交
1495 1496
{
	int version;
K
Kirill Korotaev 已提交
1497
	struct ipc_namespace *ns;
1498
	void __user *p = (void __user *)arg;
L
Linus Torvalds 已提交
1499 1500 1501 1502 1503

	if (semid < 0)
		return -EINVAL;

	version = ipc_parse_version(&cmd);
K
Kirill Korotaev 已提交
1504
	ns = current->nsproxy->ipc_ns;
L
Linus Torvalds 已提交
1505 1506 1507 1508

	switch(cmd) {
	case IPC_INFO:
	case SEM_INFO:
1509
	case IPC_STAT:
L
Linus Torvalds 已提交
1510
	case SEM_STAT:
1511
		return semctl_nolock(ns, semid, cmd, version, p);
L
Linus Torvalds 已提交
1512 1513 1514 1515 1516 1517
	case GETALL:
	case GETVAL:
	case GETPID:
	case GETNCNT:
	case GETZCNT:
	case SETALL:
1518 1519 1520
		return semctl_main(ns, semid, semnum, cmd, p);
	case SETVAL:
		return semctl_setval(ns, semid, semnum, arg);
L
Linus Torvalds 已提交
1521 1522
	case IPC_RMID:
	case IPC_SET:
1523
		return semctl_down(ns, semid, cmd, version, p);
L
Linus Torvalds 已提交
1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545
	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) {
1546
		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
L
Linus Torvalds 已提交
1547 1548
		if (undo_list == NULL)
			return -ENOMEM;
I
Ingo Molnar 已提交
1549
		spin_lock_init(&undo_list->lock);
L
Linus Torvalds 已提交
1550
		atomic_set(&undo_list->refcnt, 1);
1551 1552
		INIT_LIST_HEAD(&undo_list->list_proc);

L
Linus Torvalds 已提交
1553 1554 1555 1556 1557 1558
		current->sysvsem.undo_list = undo_list;
	}
	*undo_listp = undo_list;
	return 0;
}

1559
static struct sem_undo *__lookup_undo(struct sem_undo_list *ulp, int semid)
L
Linus Torvalds 已提交
1560
{
1561
	struct sem_undo *un;
1562

1563 1564 1565
	list_for_each_entry_rcu(un, &ulp->list_proc, list_proc) {
		if (un->semid == semid)
			return un;
L
Linus Torvalds 已提交
1566
	}
1567
	return NULL;
L
Linus Torvalds 已提交
1568 1569
}

1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583
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;
}

1584 1585 1586 1587 1588 1589 1590 1591
/**
 * 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.
1592 1593
 * Lifetime-rules: sem_undo is rcu-protected, on success, the function
 * performs a rcu_read_lock().
1594 1595
 */
static struct sem_undo *find_alloc_undo(struct ipc_namespace *ns, int semid)
L
Linus Torvalds 已提交
1596 1597 1598 1599
{
	struct sem_array *sma;
	struct sem_undo_list *ulp;
	struct sem_undo *un, *new;
1600
	int nsems, error;
L
Linus Torvalds 已提交
1601 1602 1603 1604 1605

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

1606
	rcu_read_lock();
1607
	spin_lock(&ulp->lock);
L
Linus Torvalds 已提交
1608
	un = lookup_undo(ulp, semid);
1609
	spin_unlock(&ulp->lock);
L
Linus Torvalds 已提交
1610 1611 1612 1613
	if (likely(un!=NULL))
		goto out;

	/* no undo structure around - allocate one. */
1614
	/* step 1: figure out the size of the semaphore array */
1615 1616 1617
	sma = sem_obtain_object_check(ns, semid);
	if (IS_ERR(sma)) {
		rcu_read_unlock();
J
Julia Lawall 已提交
1618
		return ERR_CAST(sma);
1619
	}
1620

L
Linus Torvalds 已提交
1621
	nsems = sma->sem_nsems;
1622 1623 1624 1625 1626
	if (!ipc_rcu_getref(sma)) {
		rcu_read_unlock();
		un = ERR_PTR(-EIDRM);
		goto out;
	}
1627
	rcu_read_unlock();
L
Linus Torvalds 已提交
1628

1629
	/* step 2: allocate new undo structure */
1630
	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
L
Linus Torvalds 已提交
1631
	if (!new) {
1632
		sem_putref(sma);
L
Linus Torvalds 已提交
1633 1634 1635
		return ERR_PTR(-ENOMEM);
	}

1636
	/* step 3: Acquire the lock on semaphore array */
1637
	rcu_read_lock();
1638
	sem_lock_and_putref(sma);
L
Linus Torvalds 已提交
1639
	if (sma->sem_perm.deleted) {
1640
		sem_unlock(sma, -1);
1641
		rcu_read_unlock();
L
Linus Torvalds 已提交
1642 1643 1644 1645
		kfree(new);
		un = ERR_PTR(-EIDRM);
		goto out;
	}
1646 1647 1648 1649 1650 1651 1652 1653 1654 1655
	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;
	}
1656 1657
	/* step 5: initialize & link new undo structure */
	new->semadj = (short *) &new[1];
1658
	new->ulp = ulp;
1659 1660
	new->semid = semid;
	assert_spin_locked(&ulp->lock);
1661
	list_add_rcu(&new->list_proc, &ulp->list_proc);
1662
	ipc_assert_locked_object(&sma->sem_perm);
1663
	list_add(&new->list_id, &sma->list_id);
1664
	un = new;
1665

1666
success:
1667
	spin_unlock(&ulp->lock);
1668
	sem_unlock(sma, -1);
L
Linus Torvalds 已提交
1669 1670 1671 1672
out:
	return un;
}

1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698

/**
 * 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;
}

1699 1700
SYSCALL_DEFINE4(semtimedop, int, semid, struct sembuf __user *, tsops,
		unsigned, nsops, const struct timespec __user *, timeout)
L
Linus Torvalds 已提交
1701 1702 1703 1704 1705 1706
{
	int error = -EINVAL;
	struct sem_array *sma;
	struct sembuf fast_sops[SEMOPM_FAST];
	struct sembuf* sops = fast_sops, *sop;
	struct sem_undo *un;
1707
	int undos = 0, alter = 0, max, locknum;
L
Linus Torvalds 已提交
1708 1709
	struct sem_queue queue;
	unsigned long jiffies_left = 0;
K
Kirill Korotaev 已提交
1710
	struct ipc_namespace *ns;
1711
	struct list_head tasks;
K
Kirill Korotaev 已提交
1712 1713

	ns = current->nsproxy->ipc_ns;
L
Linus Torvalds 已提交
1714 1715 1716

	if (nsops < 1 || semid < 0)
		return -EINVAL;
K
Kirill Korotaev 已提交
1717
	if (nsops > ns->sc_semopm)
L
Linus Torvalds 已提交
1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745
		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)
1746 1747
			undos = 1;
		if (sop->sem_op != 0)
L
Linus Torvalds 已提交
1748 1749 1750
			alter = 1;
	}

1751 1752
	INIT_LIST_HEAD(&tasks);

L
Linus Torvalds 已提交
1753
	if (undos) {
1754
		/* On success, find_alloc_undo takes the rcu_read_lock */
1755
		un = find_alloc_undo(ns, semid);
L
Linus Torvalds 已提交
1756 1757 1758 1759
		if (IS_ERR(un)) {
			error = PTR_ERR(un);
			goto out_free;
		}
1760
	} else {
L
Linus Torvalds 已提交
1761
		un = NULL;
1762 1763
		rcu_read_lock();
	}
L
Linus Torvalds 已提交
1764

1765
	sma = sem_obtain_object_check(ns, semid);
1766
	if (IS_ERR(sma)) {
1767
		rcu_read_unlock();
1768
		error = PTR_ERR(sma);
L
Linus Torvalds 已提交
1769
		goto out_free;
1770 1771
	}

1772
	error = -EFBIG;
1773 1774
	if (max >= sma->sem_nsems)
		goto out_rcu_wakeup;
1775 1776

	error = -EACCES;
1777 1778
	if (ipcperms(ns, &sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
		goto out_rcu_wakeup;
1779 1780

	error = security_sem_semop(sma, sops, nsops, alter);
1781 1782
	if (error)
		goto out_rcu_wakeup;
1783

L
Linus Torvalds 已提交
1784
	/*
1785
	 * semid identifiers are not unique - find_alloc_undo may have
L
Linus Torvalds 已提交
1786
	 * allocated an undo structure, it was invalidated by an RMID
1787
	 * and now a new array with received the same id. Check and fail.
L
Lucas De Marchi 已提交
1788
	 * This case can be detected checking un->semid. The existence of
1789
	 * "un" itself is guaranteed by rcu.
L
Linus Torvalds 已提交
1790
	 */
1791
	error = -EIDRM;
1792 1793 1794
	locknum = sem_lock(sma, sops, nsops);
	if (un && un->semid == -1)
		goto out_unlock_free;
1795

1796 1797
	error = perform_atomic_semop(sma, sops, nsops, un,
					task_tgid_vnr(current));
L
Linus Torvalds 已提交
1798 1799
	if (error <= 0) {
		if (alter && error == 0)
1800
			do_smart_update(sma, sops, nsops, 1, &tasks);
1801

L
Linus Torvalds 已提交
1802 1803 1804 1805 1806 1807 1808 1809 1810 1811
		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;
1812
	queue.pid = task_tgid_vnr(current);
L
Linus Torvalds 已提交
1813 1814
	queue.alter = alter;

1815 1816 1817 1818
	if (nsops == 1) {
		struct sem *curr;
		curr = &sma->sem_base[sops->sem_num];

1819 1820 1821 1822 1823 1824 1825 1826 1827 1828
		if (alter) {
			if (sma->complex_count) {
				list_add_tail(&queue.list,
						&sma->pending_alter);
			} else {

				list_add_tail(&queue.list,
						&curr->pending_alter);
			}
		} else {
1829
			list_add_tail(&queue.list, &curr->pending_const);
1830
		}
1831
	} else {
1832 1833 1834
		if (!sma->complex_count)
			merge_queues(sma);

1835
		if (alter)
1836
			list_add_tail(&queue.list, &sma->pending_alter);
1837
		else
1838 1839
			list_add_tail(&queue.list, &sma->pending_const);

1840 1841 1842
		sma->complex_count++;
	}

L
Linus Torvalds 已提交
1843 1844
	queue.status = -EINTR;
	queue.sleeper = current;
1845 1846

sleep_again:
L
Linus Torvalds 已提交
1847
	current->state = TASK_INTERRUPTIBLE;
1848
	sem_unlock(sma, locknum);
1849
	rcu_read_unlock();
L
Linus Torvalds 已提交
1850 1851 1852 1853 1854 1855

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

1856
	error = get_queue_result(&queue);
L
Linus Torvalds 已提交
1857 1858 1859

	if (error != -EINTR) {
		/* fast path: update_queue already obtained all requested
1860 1861 1862 1863 1864 1865 1866 1867
		 * 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();

L
Linus Torvalds 已提交
1868 1869 1870
		goto out_free;
	}

1871
	rcu_read_lock();
1872
	sma = sem_obtain_lock(ns, semid, sops, nsops, &locknum);
1873 1874 1875 1876 1877 1878 1879 1880 1881

	/*
	 * 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().
	 */
1882
	if (IS_ERR(sma)) {
1883
		rcu_read_unlock();
L
Linus Torvalds 已提交
1884 1885 1886
		goto out_free;
	}

1887

L
Linus Torvalds 已提交
1888
	/*
1889 1890
	 * If queue.status != -EINTR we are woken up by another process.
	 * Leave without unlink_queue(), but with sem_unlock().
L
Linus Torvalds 已提交
1891
	 */
1892

L
Linus Torvalds 已提交
1893 1894 1895 1896 1897 1898 1899 1900 1901
	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;
1902 1903 1904 1905 1906 1907 1908

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

1909
	unlink_queue(sma, &queue);
L
Linus Torvalds 已提交
1910 1911

out_unlock_free:
1912
	sem_unlock(sma, locknum);
1913
out_rcu_wakeup:
1914
	rcu_read_unlock();
1915
	wake_up_sem_queue_do(&tasks);
L
Linus Torvalds 已提交
1916 1917 1918 1919 1920 1921
out_free:
	if(sops != fast_sops)
		kfree(sops);
	return error;
}

1922 1923
SYSCALL_DEFINE3(semop, int, semid, struct sembuf __user *, tsops,
		unsigned, nsops)
L
Linus Torvalds 已提交
1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962
{
	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)
{
1963
	struct sem_undo_list *ulp;
L
Linus Torvalds 已提交
1964

1965 1966
	ulp = tsk->sysvsem.undo_list;
	if (!ulp)
L
Linus Torvalds 已提交
1967
		return;
1968
	tsk->sysvsem.undo_list = NULL;
L
Linus Torvalds 已提交
1969

1970
	if (!atomic_dec_and_test(&ulp->refcnt))
L
Linus Torvalds 已提交
1971 1972
		return;

1973
	for (;;) {
L
Linus Torvalds 已提交
1974
		struct sem_array *sma;
1975
		struct sem_undo *un;
1976
		struct list_head tasks;
1977
		int semid, i;
1978

1979
		rcu_read_lock();
1980 1981
		un = list_entry_rcu(ulp->list_proc.next,
				    struct sem_undo, list_proc);
1982 1983 1984 1985
		if (&un->list_proc == &ulp->list_proc)
			semid = -1;
		 else
			semid = un->semid;
1986

1987 1988
		if (semid == -1) {
			rcu_read_unlock();
1989
			break;
1990
		}
L
Linus Torvalds 已提交
1991

1992
		sma = sem_obtain_object_check(tsk->nsproxy->ipc_ns, un->semid);
1993
		/* exit_sem raced with IPC_RMID, nothing to do */
1994 1995
		if (IS_ERR(sma)) {
			rcu_read_unlock();
1996
			continue;
1997
		}
L
Linus Torvalds 已提交
1998

1999
		sem_lock(sma, NULL, -1);
2000
		un = __lookup_undo(ulp, semid);
2001 2002 2003 2004
		if (un == NULL) {
			/* exit_sem raced with IPC_RMID+semget() that created
			 * exactly the same semid. Nothing to do.
			 */
2005
			sem_unlock(sma, -1);
2006
			rcu_read_unlock();
2007 2008 2009 2010
			continue;
		}

		/* remove un from the linked lists */
2011
		ipc_assert_locked_object(&sma->sem_perm);
2012 2013
		list_del(&un->list_id);

2014 2015 2016 2017
		spin_lock(&ulp->lock);
		list_del_rcu(&un->list_proc);
		spin_unlock(&ulp->lock);

2018 2019
		/* perform adjustments registered in un */
		for (i = 0; i < sma->sem_nsems; i++) {
I
Ingo Molnar 已提交
2020
			struct sem * semaphore = &sma->sem_base[i];
2021 2022
			if (un->semadj[i]) {
				semaphore->semval += un->semadj[i];
L
Linus Torvalds 已提交
2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035
				/*
				 * 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
2036 2037 2038 2039
				if (semaphore->semval < 0)
					semaphore->semval = 0;
				if (semaphore->semval > SEMVMX)
					semaphore->semval = SEMVMX;
2040
				semaphore->sempid = task_tgid_vnr(current);
L
Linus Torvalds 已提交
2041 2042 2043
			}
		}
		/* maybe some queued-up processes were waiting for this */
2044 2045
		INIT_LIST_HEAD(&tasks);
		do_smart_update(sma, NULL, 0, 1, &tasks);
2046
		sem_unlock(sma, -1);
2047
		rcu_read_unlock();
2048
		wake_up_sem_queue_do(&tasks);
2049

2050
		kfree_rcu(un, rcu);
L
Linus Torvalds 已提交
2051
	}
2052
	kfree(ulp);
L
Linus Torvalds 已提交
2053 2054 2055
}

#ifdef CONFIG_PROC_FS
2056
static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
L
Linus Torvalds 已提交
2057
{
2058
	struct user_namespace *user_ns = seq_user_ns(s);
2059
	struct sem_array *sma = it;
2060 2061 2062
	time_t sem_otime;

	sem_otime = get_semotime(sma);
2063 2064

	return seq_printf(s,
2065
			  "%10d %10d  %4o %10u %5u %5u %5u %5u %10lu %10lu\n",
2066
			  sma->sem_perm.key,
N
Nadia Derbey 已提交
2067
			  sma->sem_perm.id,
2068 2069
			  sma->sem_perm.mode,
			  sma->sem_nsems,
2070 2071 2072 2073
			  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),
2074
			  sem_otime,
2075
			  sma->sem_ctime);
L
Linus Torvalds 已提交
2076 2077
}
#endif