Patch "ipc,shm: shorten critical region in shmctl_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,shm: shorten critical region in shmctl_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-shm-shorten-critical-region-in-shmctl_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 79ccf0f8c8e04e8b9eda6645ba0f63b0915a3075 Mon Sep 17 00:00:00 2001
From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>
Date: Wed, 11 Sep 2013 14:26:16 -0700
Subject: ipc,shm: shorten critical region in shmctl_down

From: Davidlohr Bueso <davidlohr.bueso@xxxxxx>

commit 79ccf0f8c8e04e8b9eda6645ba0f63b0915a3075 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>
Tested-by: Sedat Dilek <sedat.dilek@xxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Manfred Spraul <manfred@xxxxxxxxxxxxxxxx>
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/shm.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/ipc/shm.c
+++ b/ipc/shm.c
@@ -780,11 +780,10 @@ static int shmctl_down(struct ipc_namesp
 	down_write(&shm_ids(ns).rw_mutex);
 	rcu_read_lock();
 
-	ipcp = ipcctl_pre_down(ns, &shm_ids(ns), shmid, cmd,
-			       &shmid64.shm_perm, 0);
+	ipcp = ipcctl_pre_down_nolock(ns, &shm_ids(ns), shmid, cmd,
+				      &shmid64.shm_perm, 0);
 	if (IS_ERR(ipcp)) {
 		err = PTR_ERR(ipcp);
-		/* the ipc lock is not held upon failure */
 		goto out_unlock1;
 	}
 
@@ -792,14 +791,16 @@ static int shmctl_down(struct ipc_namesp
 
 	err = security_shm_shmctl(shp, cmd);
 	if (err)
-		goto out_unlock0;
+		goto out_unlock1;
 
 	switch (cmd) {
 	case IPC_RMID:
+		ipc_lock_object(&shp->shm_perm);
 		/* do_shm_rmid unlocks the ipc object and rcu */
 		do_shm_rmid(ns, ipcp);
 		goto out_up;
 	case IPC_SET:
+		ipc_lock_object(&shp->shm_perm);
 		err = ipc_update_perm(&shmid64.shm_perm, ipcp);
 		if (err)
 			goto out_unlock0;
@@ -807,6 +808,7 @@ static int shmctl_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-shm-shorten-critical-region-in-shmctl_down.patch
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-shm-introduce-lockless-functions-to-obtain-the-ipc-object.patch
queue-3.10/ipc-remove-unused-functions.patch
queue-3.10/ipc-shm-shorten-critical-region-for-shmat.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-sem-separate-wait-for-zero-and-alter-tasks-into-seperate-queues.patch
queue-3.10/ipc-shm-shorten-critical-region-for-shmctl.patch
queue-3.10/ipc-msg-shorten-critical-region-in-msgsnd.patch
queue-3.10/ipc-shm-introduce-shmctl_nolock.patch
queue-3.10/ipc-drop-ipcctl_pre_down.patch
queue-3.10/ipc-util.c-ipc_rcu_alloc-cacheline-align-allocation.patch
queue-3.10/ipc-introduce-ipc-object-locking-helpers.patch
queue-3.10/ipc-sem.c-cacheline-align-the-semaphore-structures.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-sem.c-always-use-only-one-queue-for-alter-operations.patch
queue-3.10/ipc-shm-cleanup-do_shmat-pasta.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
queue-3.10/ipc-sem.c-rename-try_atomic_semop-to-perform_atomic_semop-docu-update.patch
queue-3.10/ipc-shm-make-shmctl_nolock-lockless.patch
queue-3.10/ipc-sem.c-replace-shared-sem_otime-with-per-semaphore-value.patch
--
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