sem.c 33.6 KB
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/*
 * linux/ipc/sem.c
 * Copyright (C) 1992 Krishna Balasubramanian
 * Copyright (C) 1995 Eric Schenk, Bruno Haible
 *
 * IMPLEMENTATION NOTES ON CODE REWRITE (Eric Schenk, January 1995):
 * This code underwent a massive rewrite in order to solve some problems
 * with the original code. In particular the original code failed to
 * wake up processes that were waiting for semval to go to 0 if the
 * value went to 0 and was then incremented rapidly enough. In solving
 * this problem I have also modified the implementation so that it
 * processes pending operations in a FIFO manner, thus give a guarantee
 * that processes waiting for a lock on the semaphore won't starve
 * unless another locking process fails to unlock.
 * In addition the following two changes in behavior have been introduced:
 * - The original implementation of semop returned the value
 *   last semaphore element examined on success. This does not
 *   match the manual page specifications, and effectively
 *   allows the user to read the semaphore even if they do not
 *   have read permissions. The implementation now returns 0
 *   on success as stated in the manual page.
 * - There is some confusion over whether the set of undo adjustments
 *   to be performed at exit should be done in an atomic manner.
 *   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.
 *   The current implementation does not do so. This is because I don't
 *   think it is the right thing (TM) to do, and because I couldn't
 *   see a clean way to get the old behavior with the new design.
 *   The POSIX standard and SVID should be consulted to determine
 *   what behavior is mandated.
 *
 * Further notes on refinement (Christoph Rohland, December 1998):
 * - The POSIX standard says, that the undo adjustments simply should
 *   redo. So the current implementation is o.K.
 * - The previous code had two flaws:
 *   1) It actively gave the semaphore to the next waiting process
 *      sleeping on the semaphore. Since this process did not have the
 *      cpu this led to many unnecessary context switches and bad
 *      performance. Now we only check which process should be able to
 *      get the semaphore and if this process wants to reduce some
 *      semaphore value we simply wake it up without doing the
 *      operation. So it has to try to get it later. Thus e.g. the
 *      running process may reacquire the semaphore during the current
 *      time slice. If it only waits for zero or increases the semaphore,
 *      we do the operation in advance and wake it up.
 *   2) It did not wake up all zero waiting processes. We try to do
 *      better but only get the semops right which only wait for zero or
 *      increase. If there are decrement operations in the operations
 *      array we do the same as before.
 *
 * With the incarnation of O(1) scheduler, it becomes unnecessary to perform
 * check/retry algorithm for waking up blocked processes as the new scheduler
 * is better at handling thread switch than the old one.
 *
 * /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
 * (c) 2001 Red Hat Inc <alan@redhat.com>
 * Lockless wakeup
 * (c) 2003 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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 */

#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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#define sem_ids(ns)	((ns)->ids[IPC_SEM_IDS])
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#define sem_unlock(sma)		ipc_unlock(&(sma)->sem_perm)
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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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}
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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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/*
 * This routine is called in the paths where the rw_mutex is held to protect
 * access to the idr tree.
 */
static inline struct sem_array *sem_lock_check_down(struct ipc_namespace *ns,
						int id)
{
	struct kern_ipc_perm *ipcp = ipc_lock_check_down(&sem_ids(ns), id);

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	if (IS_ERR(ipcp))
		return (struct sem_array *)ipcp;

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	return container_of(ipcp, struct sem_array, sem_perm);
}

/*
 * sem_lock_(check_) routines are called in the paths where the rw_mutex
 * is not held.
 */
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static inline struct sem_array *sem_lock(struct ipc_namespace *ns, int id)
{
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	struct kern_ipc_perm *ipcp = ipc_lock(&sem_ids(ns), id);

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	if (IS_ERR(ipcp))
		return (struct sem_array *)ipcp;

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	return container_of(ipcp, struct sem_array, sem_perm);
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}

static inline struct sem_array *sem_lock_check(struct ipc_namespace *ns,
						int id)
{
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	struct kern_ipc_perm *ipcp = ipc_lock_check(&sem_ids(ns), id);

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	if (IS_ERR(ipcp))
		return (struct sem_array *)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)
{
	ipc_lock_by_ptr(&sma->sem_perm);
	ipc_rcu_putref(sma);
}

static inline void sem_getref_and_unlock(struct sem_array *sma)
{
	ipc_rcu_getref(sma);
	ipc_unlock(&(sma)->sem_perm);
}

static inline void sem_putref(struct sem_array *sma)
{
	ipc_lock_by_ptr(&sma->sem_perm);
	ipc_rcu_putref(sma);
	ipc_unlock(&(sma)->sem_perm);
}

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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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	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];
	/* sma->sem_pending = NULL; */
	sma->sem_pending_last = &sma->sem_pending;
	/* sma->undo = NULL; */
	sma->sem_nsems = nsems;
	sma->sem_ctime = get_seconds();
	sem_unlock(sma);

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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;
}

asmlinkage long sys_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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}

/* Manage the doubly linked list sma->sem_pending as a FIFO:
 * insert new queue elements at the tail sma->sem_pending_last.
 */
static inline void append_to_queue (struct sem_array * sma,
				    struct sem_queue * q)
{
	*(q->prev = sma->sem_pending_last) = q;
	*(sma->sem_pending_last = &q->next) = NULL;
}

static inline void prepend_to_queue (struct sem_array * sma,
				     struct sem_queue * q)
{
	q->next = sma->sem_pending;
	*(q->prev = &sma->sem_pending) = q;
	if (q->next)
		q->next->prev = &q->next;
	else /* sma->sem_pending_last == &sma->sem_pending */
		sma->sem_pending_last = &q->next;
}

static inline void remove_from_queue (struct sem_array * sma,
				      struct sem_queue * q)
{
	*(q->prev) = q->next;
	if (q->next)
		q->next->prev = q->prev;
	else /* sma->sem_pending_last == &q->next */
		sma->sem_pending_last = q->prev;
	q->prev = NULL; /* mark as removed */
}

/*
 * 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--;
	}
	
	sma->sem_otime = get_seconds();
	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;
}

/* Go through the pending queue for the indicated semaphore
 * looking for tasks that can be completed.
 */
static void update_queue (struct sem_array * sma)
{
	int error;
	struct sem_queue * q;

	q = sma->sem_pending;
	while(q) {
		error = try_atomic_semop(sma, q->sops, q->nsops,
					 q->undo, q->pid);

		/* Does q->sleeper still need to sleep? */
		if (error <= 0) {
			struct sem_queue *n;
			remove_from_queue(sma,q);
			q->status = IN_WAKEUP;
			/*
			 * Continue scanning. The next operation
			 * that must be checked depends on the type of the
			 * completed operation:
			 * - if the operation modified the array, then
			 *   restart from the head of the queue and
			 *   check for threads that might be waiting
			 *   for semaphore values to become 0.
			 * - if the operation didn't modify the array,
			 *   then just continue.
			 */
			if (q->alter)
				n = sma->sem_pending;
			else
				n = q->next;
			wake_up_process(q->sleeper);
			/* hands-off: q will disappear immediately after
			 * writing q->status.
			 */
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			smp_wmb();
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			q->status = error;
			q = n;
		} else {
			q = q->next;
		}
	}
}

/* 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;
	for (q = sma->sem_pending; q; q = q->next) {
		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;
}
static int count_semzcnt (struct sem_array * sma, ushort semnum)
{
	int semzcnt;
	struct sem_queue * q;

	semzcnt = 0;
	for (q = sma->sem_pending; q; q = q->next) {
		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;
}

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/* 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.
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 */
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static void freeary(struct ipc_namespace *ns, struct kern_ipc_perm *ipcp)
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{
	struct sem_undo *un;
	struct sem_queue *q;
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	struct sem_array *sma = container_of(ipcp, struct sem_array, sem_perm);
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	/* Invalidate the existing undo structures for this semaphore set.
	 * (They will be freed without any further action in exit_sem()
	 * or during the next semop.)
	 */
	for (un = sma->undo; un; un = un->id_next)
		un->semid = -1;

	/* Wake up all pending processes and let them fail with EIDRM. */
	q = sma->sem_pending;
	while(q) {
		struct sem_queue *n;
		/* lazy remove_from_queue: we are killing the whole queue */
		q->prev = NULL;
		n = q->next;
		q->status = IN_WAKEUP;
		wake_up_process(q->sleeper); /* doesn't sleep */
566
		smp_wmb();
L
Linus Torvalds 已提交
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		q->status = -EIDRM;	/* hands-off q */
		q = n;
	}

N
Nadia Derbey 已提交
571 572
	/* Remove the semaphore set from the IDR */
	sem_rmid(ns, sma);
L
Linus Torvalds 已提交
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	sem_unlock(sma);

K
Kirill Korotaev 已提交
575
	ns->used_sems -= sma->sem_nsems;
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	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;

		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;
	}
}

602 603
static int semctl_nolock(struct ipc_namespace *ns, int semid,
			 int cmd, int version, union semun arg)
L
Linus Torvalds 已提交
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{
	int err = -EINVAL;
	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
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		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
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		seminfo.semvmx = SEMVMX;
		seminfo.semmnu = SEMMNU;
		seminfo.semmap = SEMMAP;
		seminfo.semume = SEMUME;
N
Nadia Derbey 已提交
628
		down_read(&sem_ids(ns).rw_mutex);
L
Linus Torvalds 已提交
629
		if (cmd == SEM_INFO) {
K
Kirill Korotaev 已提交
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			seminfo.semusz = sem_ids(ns).in_use;
			seminfo.semaem = ns->used_sems;
L
Linus Torvalds 已提交
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		} else {
			seminfo.semusz = SEMUSZ;
			seminfo.semaem = SEMAEM;
		}
N
Nadia Derbey 已提交
636
		max_id = ipc_get_maxid(&sem_ids(ns));
N
Nadia Derbey 已提交
637
		up_read(&sem_ids(ns).rw_mutex);
L
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		if (copy_to_user (arg.__buf, &seminfo, sizeof(struct seminfo))) 
			return -EFAULT;
		return (max_id < 0) ? 0: max_id;
	}
642
	case IPC_STAT:
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	case SEM_STAT:
	{
		struct semid64_ds tbuf;
		int id;

648 649 650 651 652 653 654 655 656 657 658
		if (cmd == SEM_STAT) {
			sma = sem_lock(ns, semid);
			if (IS_ERR(sma))
				return PTR_ERR(sma);
			id = sma->sem_perm.id;
		} else {
			sma = sem_lock_check(ns, semid);
			if (IS_ERR(sma))
				return PTR_ERR(sma);
			id = 0;
		}
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		err = -EACCES;
		if (ipcperms (&sma->sem_perm, S_IRUGO))
			goto out_unlock;

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

668 669
		memset(&tbuf, 0, sizeof(tbuf));

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		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;
		sem_unlock(sma);
		if (copy_semid_to_user (arg.buf, &tbuf, version))
			return -EFAULT;
		return id;
	}
	default:
		return -EINVAL;
	}
	return err;
out_unlock:
	sem_unlock(sma);
	return err;
}

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Kirill Korotaev 已提交
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static int semctl_main(struct ipc_namespace *ns, int semid, int semnum,
		int cmd, int version, union semun arg)
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{
	struct sem_array *sma;
	struct sem* curr;
	int err;
	ushort fast_sem_io[SEMMSL_FAST];
	ushort* sem_io = fast_sem_io;
	int nsems;

698 699 700
	sma = sem_lock_check(ns, semid);
	if (IS_ERR(sma))
		return PTR_ERR(sma);
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	nsems = sma->sem_nsems;

	err = -EACCES;
	if (ipcperms (&sma->sem_perm, (cmd==SETVAL||cmd==SETALL)?S_IWUGO:S_IRUGO))
		goto out_unlock;

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

	err = -EACCES;
	switch (cmd) {
	case GETALL:
	{
		ushort __user *array = arg.array;
		int i;

		if(nsems > SEMMSL_FAST) {
720
			sem_getref_and_unlock(sma);
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			sem_io = ipc_alloc(sizeof(ushort)*nsems);
			if(sem_io == NULL) {
724
				sem_putref(sma);
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				return -ENOMEM;
			}

728
			sem_lock_and_putref(sma);
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			if (sma->sem_perm.deleted) {
				sem_unlock(sma);
				err = -EIDRM;
				goto out_free;
			}
		}

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

749
		sem_getref_and_unlock(sma);
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		if(nsems > SEMMSL_FAST) {
			sem_io = ipc_alloc(sizeof(ushort)*nsems);
			if(sem_io == NULL) {
754
				sem_putref(sma);
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				return -ENOMEM;
			}
		}

		if (copy_from_user (sem_io, arg.array, nsems*sizeof(ushort))) {
760
			sem_putref(sma);
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			err = -EFAULT;
			goto out_free;
		}

		for (i = 0; i < nsems; i++) {
			if (sem_io[i] > SEMVMX) {
767
				sem_putref(sma);
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				err = -ERANGE;
				goto out_free;
			}
		}
772
		sem_lock_and_putref(sma);
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		if (sma->sem_perm.deleted) {
			sem_unlock(sma);
			err = -EIDRM;
			goto out_free;
		}

		for (i = 0; i < nsems; i++)
			sma->sem_base[i].semval = sem_io[i];
		for (un = sma->undo; un; un = un->id_next)
			for (i = 0; i < nsems; i++)
				un->semadj[i] = 0;
		sma->sem_ctime = get_seconds();
		/* maybe some queued-up processes were waiting for this */
		update_queue(sma);
		err = 0;
		goto out_unlock;
	}
	/* GETVAL, GETPID, GETNCTN, GETZCNT, SETVAL: fall-through */
	}
	err = -EINVAL;
	if(semnum < 0 || semnum >= nsems)
		goto out_unlock;

	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;
	case SETVAL:
	{
		int val = arg.val;
		struct sem_undo *un;
		err = -ERANGE;
		if (val > SEMVMX || val < 0)
			goto out_unlock;

		for (un = sma->undo; un; un = un->id_next)
			un->semadj[semnum] = 0;
		curr->semval = val;
822
		curr->sempid = task_tgid_vnr(current);
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		sma->sem_ctime = get_seconds();
		/* maybe some queued-up processes were waiting for this */
		update_queue(sma);
		err = 0;
		goto out_unlock;
	}
	}
out_unlock:
	sem_unlock(sma);
out_free:
	if(sem_io != fast_sem_io)
		ipc_free(sem_io, sizeof(ushort)*nsems);
	return err;
}

struct sem_setbuf {
	uid_t	uid;
	gid_t	gid;
	mode_t	mode;
};

static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __user *buf, int version)
{
	switch(version) {
	case IPC_64:
	    {
		struct semid64_ds tbuf;

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

		out->uid	= tbuf.sem_perm.uid;
		out->gid	= tbuf.sem_perm.gid;
		out->mode	= tbuf.sem_perm.mode;

		return 0;
	    }
	case IPC_OLD:
	    {
		struct semid_ds tbuf_old;

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

		out->uid	= tbuf_old.sem_perm.uid;
		out->gid	= tbuf_old.sem_perm.gid;
		out->mode	= tbuf_old.sem_perm.mode;

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

878 879 880 881 882
/*
 * 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.
 */
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static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,
		int cmd, int version, union semun arg)
L
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{
	struct sem_array *sma;
	int err;
888
	struct sem_setbuf uninitialized_var(setbuf);
L
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	struct kern_ipc_perm *ipcp;

	if(cmd == IPC_SET) {
		if(copy_semid_from_user (&setbuf, arg.buf, version))
			return -EFAULT;
	}
895
	down_write(&sem_ids(ns).rw_mutex);
N
Nadia Derbey 已提交
896
	sma = sem_lock_check_down(ns, semid);
897 898 899 900
	if (IS_ERR(sma)) {
		err = PTR_ERR(sma);
		goto out_up;
	}
L
Linus Torvalds 已提交
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	ipcp = &sma->sem_perm;
S
Steve Grubb 已提交
903 904 905 906 907

	err = audit_ipc_obj(ipcp);
	if (err)
		goto out_unlock;

908 909 910 911 912
	if (cmd == IPC_SET) {
		err = audit_ipc_set_perm(0, setbuf.uid, setbuf.gid, setbuf.mode);
		if (err)
			goto out_unlock;
	}
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913 914 915 916 917 918 919 920 921 922 923 924
	if (current->euid != ipcp->cuid && 
	    current->euid != ipcp->uid && !capable(CAP_SYS_ADMIN)) {
	    	err=-EPERM;
		goto out_unlock;
	}

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

	switch(cmd){
	case IPC_RMID:
925
		freeary(ns, ipcp);
926
		goto out_up;
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Linus Torvalds 已提交
927 928 929 930 931 932 933 934 935 936 937 938 939
	case IPC_SET:
		ipcp->uid = setbuf.uid;
		ipcp->gid = setbuf.gid;
		ipcp->mode = (ipcp->mode & ~S_IRWXUGO)
				| (setbuf.mode & S_IRWXUGO);
		sma->sem_ctime = get_seconds();
		break;
	default:
		err = -EINVAL;
	}

out_unlock:
	sem_unlock(sma);
940 941
out_up:
	up_write(&sem_ids(ns).rw_mutex);
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	return err;
}

asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg)
{
	int err = -EINVAL;
	int version;
K
Kirill Korotaev 已提交
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	struct ipc_namespace *ns;
L
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950 951 952 953 954

	if (semid < 0)
		return -EINVAL;

	version = ipc_parse_version(&cmd);
K
Kirill Korotaev 已提交
955
	ns = current->nsproxy->ipc_ns;
L
Linus Torvalds 已提交
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	switch(cmd) {
	case IPC_INFO:
	case SEM_INFO:
960
	case IPC_STAT:
L
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	case SEM_STAT:
962
		err = semctl_nolock(ns, semid, cmd, version, arg);
L
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		return err;
	case GETALL:
	case GETVAL:
	case GETPID:
	case GETNCNT:
	case GETZCNT:
	case SETVAL:
	case SETALL:
K
Kirill Korotaev 已提交
971
		err = semctl_main(ns,semid,semnum,cmd,version,arg);
L
Linus Torvalds 已提交
972 973 974
		return err;
	case IPC_RMID:
	case IPC_SET:
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Kirill Korotaev 已提交
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		err = semctl_down(ns,semid,semnum,cmd,version,arg);
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		return err;
	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) {
999
		undo_list = kzalloc(sizeof(*undo_list), GFP_KERNEL);
L
Linus Torvalds 已提交
1000 1001
		if (undo_list == NULL)
			return -ENOMEM;
I
Ingo Molnar 已提交
1002
		spin_lock_init(&undo_list->lock);
L
Linus Torvalds 已提交
1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029
		atomic_set(&undo_list->refcnt, 1);
		current->sysvsem.undo_list = undo_list;
	}
	*undo_listp = undo_list;
	return 0;
}

static struct sem_undo *lookup_undo(struct sem_undo_list *ulp, int semid)
{
	struct sem_undo **last, *un;

	last = &ulp->proc_list;
	un = *last;
	while(un != NULL) {
		if(un->semid==semid)
			break;
		if(un->semid==-1) {
			*last=un->proc_next;
			kfree(un);
		} else {
			last=&un->proc_next;
		}
		un=*last;
	}
	return un;
}

K
Kirill Korotaev 已提交
1030
static struct sem_undo *find_undo(struct ipc_namespace *ns, int semid)
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1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041
{
	struct sem_array *sma;
	struct sem_undo_list *ulp;
	struct sem_undo *un, *new;
	int nsems;
	int error;

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

1042
	spin_lock(&ulp->lock);
L
Linus Torvalds 已提交
1043
	un = lookup_undo(ulp, semid);
1044
	spin_unlock(&ulp->lock);
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1045 1046 1047 1048
	if (likely(un!=NULL))
		goto out;

	/* no undo structure around - allocate one. */
1049 1050 1051 1052
	sma = sem_lock_check(ns, semid);
	if (IS_ERR(sma))
		return ERR_PTR(PTR_ERR(sma));

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1053
	nsems = sma->sem_nsems;
1054
	sem_getref_and_unlock(sma);
L
Linus Torvalds 已提交
1055

1056
	new = kzalloc(sizeof(struct sem_undo) + sizeof(short)*nsems, GFP_KERNEL);
L
Linus Torvalds 已提交
1057
	if (!new) {
1058
		sem_putref(sma);
L
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1059 1060 1061 1062 1063
		return ERR_PTR(-ENOMEM);
	}
	new->semadj = (short *) &new[1];
	new->semid = semid;

1064
	spin_lock(&ulp->lock);
L
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	un = lookup_undo(ulp, semid);
	if (un) {
1067
		spin_unlock(&ulp->lock);
L
Linus Torvalds 已提交
1068
		kfree(new);
1069
		sem_putref(sma);
L
Linus Torvalds 已提交
1070 1071
		goto out;
	}
1072
	sem_lock_and_putref(sma);
L
Linus Torvalds 已提交
1073 1074
	if (sma->sem_perm.deleted) {
		sem_unlock(sma);
1075
		spin_unlock(&ulp->lock);
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1076 1077 1078 1079 1080 1081 1082 1083 1084 1085
		kfree(new);
		un = ERR_PTR(-EIDRM);
		goto out;
	}
	new->proc_next = ulp->proc_list;
	ulp->proc_list = new;
	new->id_next = sma->undo;
	sma->undo = new;
	sem_unlock(sma);
	un = new;
1086
	spin_unlock(&ulp->lock);
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out:
	return un;
}

asmlinkage long sys_semtimedop(int semid, struct sembuf __user *tsops,
			unsigned nsops, const struct timespec __user *timeout)
{
	int error = -EINVAL;
	struct sem_array *sma;
	struct sembuf fast_sops[SEMOPM_FAST];
	struct sembuf* sops = fast_sops, *sop;
	struct sem_undo *un;
1099
	int undos = 0, alter = 0, max;
L
Linus Torvalds 已提交
1100 1101
	struct sem_queue queue;
	unsigned long jiffies_left = 0;
K
Kirill Korotaev 已提交
1102 1103 1104
	struct ipc_namespace *ns;

	ns = current->nsproxy->ipc_ns;
L
Linus Torvalds 已提交
1105 1106 1107

	if (nsops < 1 || semid < 0)
		return -EINVAL;
K
Kirill Korotaev 已提交
1108
	if (nsops > ns->sc_semopm)
L
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1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136
		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)
1137 1138
			undos = 1;
		if (sop->sem_op != 0)
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			alter = 1;
	}

retry_undos:
	if (undos) {
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		un = find_undo(ns, semid);
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		if (IS_ERR(un)) {
			error = PTR_ERR(un);
			goto out_free;
		}
	} else
		un = NULL;

1152 1153 1154
	sma = sem_lock_check(ns, semid);
	if (IS_ERR(sma)) {
		error = PTR_ERR(sma);
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		goto out_free;
1156 1157
	}

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	/*
1159
	 * semid identifiers are not unique - find_undo may have
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	 * allocated an undo structure, it was invalidated by an RMID
	 * and now a new array with received the same id. Check and retry.
	 */
	if (un && un->semid == -1) {
		sem_unlock(sma);
		goto retry_undos;
	}
	error = -EFBIG;
	if (max >= sma->sem_nsems)
		goto out_unlock_free;

	error = -EACCES;
	if (ipcperms(&sma->sem_perm, alter ? S_IWUGO : S_IRUGO))
		goto out_unlock_free;

	error = security_sem_semop(sma, sops, nsops, alter);
	if (error)
		goto out_unlock_free;

1179
	error = try_atomic_semop (sma, sops, nsops, un, task_tgid_vnr(current));
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	if (error <= 0) {
		if (alter && error == 0)
			update_queue (sma);
		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.sma = sma;
	queue.sops = sops;
	queue.nsops = nsops;
	queue.undo = un;
1194
	queue.pid = task_tgid_vnr(current);
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	queue.id = semid;
	queue.alter = alter;
	if (alter)
		append_to_queue(sma ,&queue);
	else
		prepend_to_queue(sma ,&queue);

	queue.status = -EINTR;
	queue.sleeper = current;
	current->state = TASK_INTERRUPTIBLE;
	sem_unlock(sma);

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

	error = queue.status;
	while(unlikely(error == IN_WAKEUP)) {
		cpu_relax();
		error = queue.status;
	}

	if (error != -EINTR) {
		/* fast path: update_queue already obtained all requested
		 * resources */
		goto out_free;
	}

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	sma = sem_lock(ns, semid);
1225
	if (IS_ERR(sma)) {
1226
		BUG_ON(queue.prev != NULL);
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		error = -EIDRM;
		goto out_free;
	}

	/*
	 * If queue.status != -EINTR we are woken up by another process
	 */
	error = queue.status;
	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;
	remove_from_queue(sma,&queue);
	goto out_unlock_free;

out_unlock_free:
	sem_unlock(sma);
out_free:
	if(sops != fast_sops)
		kfree(sops);
	return error;
}

asmlinkage long sys_semop (int semid, struct sembuf __user *tsops, unsigned nsops)
{
	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)
{
	struct sem_undo_list *undo_list;
	struct sem_undo *u, **up;
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	struct ipc_namespace *ns;
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	undo_list = tsk->sysvsem.undo_list;
	if (!undo_list)
		return;

	if (!atomic_dec_and_test(&undo_list->refcnt))
		return;

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	ns = tsk->nsproxy->ipc_ns;
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	/* There's no need to hold the semundo list lock, as current
         * is the last task exiting for this undo list.
	 */
	for (up = &undo_list->proc_list; (u = *up); *up = u->proc_next, kfree(u)) {
		struct sem_array *sma;
		int nsems, i;
		struct sem_undo *un, **unp;
		int semid;
	       
		semid = u->semid;

		if(semid == -1)
			continue;
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		sma = sem_lock(ns, semid);
1321
		if (IS_ERR(sma))
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			continue;

		if (u->semid == -1)
			goto next_entry;

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		BUG_ON(sem_checkid(sma, u->semid));
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		/* remove u from the sma->undo list */
		for (unp = &sma->undo; (un = *unp); unp = &un->id_next) {
			if (u == un)
				goto found;
		}
		printk ("exit_sem undo list error id=%d\n", u->semid);
		goto next_entry;
found:
		*unp = un->id_next;
		/* perform adjustments registered in u */
		nsems = sma->sem_nsems;
		for (i = 0; i < nsems; i++) {
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Ingo Molnar 已提交
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			struct sem * semaphore = &sma->sem_base[i];
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			if (u->semadj[i]) {
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Ingo Molnar 已提交
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				semaphore->semval += u->semadj[i];
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				/*
				 * 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>
				 */
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				if (semaphore->semval < 0)
					semaphore->semval = 0;
				if (semaphore->semval > SEMVMX)
					semaphore->semval = SEMVMX;
1361
				semaphore->sempid = task_tgid_vnr(current);
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			}
		}
		sma->sem_otime = get_seconds();
		/* maybe some queued-up processes were waiting for this */
		update_queue(sma);
next_entry:
		sem_unlock(sma);
	}
	kfree(undo_list);
}

#ifdef CONFIG_PROC_FS
1374
static int sysvipc_sem_proc_show(struct seq_file *s, void *it)
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{
1376 1377 1378 1379 1380
	struct sem_array *sma = it;

	return seq_printf(s,
			  "%10d %10d  %4o %10lu %5u %5u %5u %5u %10lu %10lu\n",
			  sma->sem_perm.key,
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Nadia Derbey 已提交
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			  sma->sem_perm.id,
1382 1383 1384 1385 1386 1387 1388 1389
			  sma->sem_perm.mode,
			  sma->sem_nsems,
			  sma->sem_perm.uid,
			  sma->sem_perm.gid,
			  sma->sem_perm.cuid,
			  sma->sem_perm.cgid,
			  sma->sem_otime,
			  sma->sem_ctime);
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}
#endif