[ 3.5.y.z extended stable ] Patch "cgroup: fix an off-by-one bug which may trigger BUG_ON()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    cgroup: fix an off-by-one bug which may trigger BUG_ON()

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From a3f7ab8154c32fbf1934037c4fae4c28bb388d53 Mon Sep 17 00:00:00 2001
From: Li Zefan <lizefan at huawei.com>
Date: Tue, 12 Mar 2013 15:36:00 -0700
Subject: [PATCH] cgroup: fix an off-by-one bug which may trigger BUG_ON()

commit 3ac1707a13a3da9cfc8f242a15b2fae6df2c5f88 upstream.

The 3rd parameter of flex_array_prealloc() is the number of elements,
not the index of the last element.

The effect of the bug is, when opening cgroup.procs, a flex array will
be allocated and all elements of the array is allocated with
GFP_KERNEL flag, but the last one is GFP_ATOMIC, and if we fail to
allocate memory for it, it'll trigger a BUG_ON().

Signed-off-by: Li Zefan <lizefan at huawei.com>
Signed-off-by: Tejun Heo <tj at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 kernel/cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 87fbb45..5168e37 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2079,7 +2079,7 @@ static int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
 	if (!group)
 		return -ENOMEM;
 	/* pre-allocate to guarantee space while iterating in rcu read-side. */
-	retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
+	retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
 	if (retval)
 		goto out_free_group_list;

--
1.8.1.2