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Commit 522bb2a2 authored by Pierre Peiffer's avatar Pierre Peiffer Committed by Linus Torvalds
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IPC/semaphores: move the rwmutex handling inside semctl_down 



semctl_down is called with the rwmutex (the one which protects the list of
ipcs) taken in write mode.

This patch moves this rwmutex taken in write-mode inside semctl_down.

This has the advantages of reducing a little bit the window during which this
rwmutex is taken, clarifying sys_semctl, and finally of having a coherent
behaviour with [shm|msg]ctl_down

Signed-off-by: default avatarPierre Peiffer <pierre.peiffer@bull.net>
Acked-by: default avatarSerge Hallyn <serue@us.ibm.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a0d092fc

ipc/sem.c

+13 −11
Original line number Diff line number Diff line
@@ -875,6 +875,11 @@ static inline unsigned long copy_semid_from_user(struct sem_setbuf *out, void __ 
	}

}



/*

 * 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.

 */

static int semctl_down(struct ipc_namespace *ns, int semid, int semnum,

		int cmd, int version, union semun arg)

{
@@ -887,9 +892,12 @@ static int semctl_down(struct ipc_namespace *ns, int semid, int semnum, 
		if(copy_semid_from_user (&setbuf, arg.buf, version))

			return -EFAULT;

	}

	down_write(&sem_ids(ns).rw_mutex);

	sma = sem_lock_check_down(ns, semid);

	if (IS_ERR(sma))

		return PTR_ERR(sma);

	if (IS_ERR(sma)) {

		err = PTR_ERR(sma);

		goto out_up;

	}



	ipcp = &sma->sem_perm;
@@ -915,26 +923,22 @@ static int semctl_down(struct ipc_namespace *ns, int semid, int semnum, 
	switch(cmd){

	case IPC_RMID:

		freeary(ns, ipcp);

		err = 0;

		break;

		goto out_up;

	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();

		sem_unlock(sma);

		err = 0;

		break;

	default:

		sem_unlock(sma);

		err = -EINVAL;

		break;

	}

	return err;



out_unlock:

	sem_unlock(sma);

out_up:

	up_write(&sem_ids(ns).rw_mutex);

	return err;

}
@@ -968,9 +972,7 @@ asmlinkage long sys_semctl (int semid, int semnum, int cmd, union semun arg) 
		return err;

	case IPC_RMID:

	case IPC_SET:

		down_write(&sem_ids(ns).rw_mutex);

		err = semctl_down(ns,semid,semnum,cmd,version,arg);

		up_write(&sem_ids(ns).rw_mutex);

		return err;

	default:

		return -EINVAL;