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Commit 15724ecb authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Linus Torvalds
Browse files

ipc,msg: shorten critical region in msgctl_down 



Instead of holding the ipc lock for the entire function, use the
ipcctl_pre_down_nolock and only acquire the lock for specific commands:
RMID and SET.

Signed-off-by: default avatarDavidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7b4cc5d8

ipc/msg.c

+7 −5
Original line number Diff line number Diff line
@@ -410,11 +410,10 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd, 
	down_write(&msg_ids(ns).rw_mutex);

	rcu_read_lock();



	ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,

	ipcp = ipcctl_pre_down_nolock(ns, &msg_ids(ns), msqid, cmd,

				      &msqid64.msg_perm, msqid64.msg_qbytes);

	if (IS_ERR(ipcp)) {

		err = PTR_ERR(ipcp);

		/* the ipc lock is not held upon failure */

		goto out_unlock1;

	}
@@ -422,10 +421,11 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd, 


	err = security_msg_queue_msgctl(msq, cmd);

	if (err)

		goto out_unlock0;

		goto out_unlock1;



	switch (cmd) {

	case IPC_RMID:

		ipc_lock_object(&msq->q_perm);

		/* freeque unlocks the ipc object and rcu */

		freeque(ns, ipcp);

		goto out_up;
@@ -433,9 +433,10 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd, 
		if (msqid64.msg_qbytes > ns->msg_ctlmnb &&

		    !capable(CAP_SYS_RESOURCE)) {

			err = -EPERM;

			goto out_unlock0;

			goto out_unlock1;

		}



		ipc_lock_object(&msq->q_perm);

		err = ipc_update_perm(&msqid64.msg_perm, ipcp);

		if (err)

			goto out_unlock0;
@@ -454,6 +455,7 @@ static int msgctl_down(struct ipc_namespace *ns, int msqid, int cmd, 
		break;

	default:

		err = -EINVAL;

		goto out_unlock1;

	}



out_unlock0: