Patch "ipc,msg: shorten critical region in msgctl_down" has been added to the 3.10-stable tree

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This is a note to let you know that I've just added the patch titled

    ipc,msg: shorten critical region in msgctl_down

to the 3.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     ipc-msg-shorten-critical-region-in-msgctl_down.patch
and it can be found in the queue-3.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 15724ecb7e9bab35fc694c666ad563adba820cc3 Mon Sep 17 00:00:00 2001
From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Date: Mon, 8 Jul 2013 16:01:13 -0700
Subject: ipc,msg: shorten critical region in msgctl_down

From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>

commit 15724ecb7e9bab35fc694c666ad563adba820cc3 upstream.

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: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Cc: Andi Kleen <andi@xxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 ipc/msg.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/ipc/msg.c
+++ b/ipc/msg.c
@@ -410,11 +410,10 @@ static int msgctl_down(struct ipc_namesp
 	down_write(&msg_ids(ns).rw_mutex);
 	rcu_read_lock();
 
-	ipcp = ipcctl_pre_down(ns, &msg_ids(ns), msqid, cmd,
-			       &msqid64.msg_perm, msqid64.msg_qbytes);
+	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_namesp
 
 	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_namesp
 		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_namesp
 		break;
 	default:
 		err = -EINVAL;
+		goto out_unlock1;
 	}
 
 out_unlock0:


Patches currently in stable-queue which might be from davidlohr.bueso@xxxxxx are

queue-3.10/ipc-msg-introduce-lockless-functions-to-obtain-the-ipc-object.patch
queue-3.10/ipc-msg-shorten-critical-region-in-msgctl_down.patch
queue-3.10/ipc-remove-unused-functions.patch
queue-3.10/ipc-msg-introduce-msgctl_nolock.patch
queue-3.10/ipc-move-rcu-lock-out-of-ipc_addid.patch
queue-3.10/ipc-msg-shorten-critical-region-in-msgsnd.patch
queue-3.10/ipc-introduce-ipc-object-locking-helpers.patch
queue-3.10/ipc-msg-shorten-critical-region-in-msgrcv.patch
queue-3.10/ipc-msg-make-msgctl_nolock-lockless.patch
queue-3.10/ipc-move-locking-out-of-ipcctl_pre_down_nolock.patch
queue-3.10/ipc-close-open-coded-spin-lock-calls.patch
--
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