2012-11-28 18:33:59

by Greg Thelen

Subject: [PATCH] cgroup: avoid creating degenerate allcg_list

Before this patch init_cgroup_root() created a degenerate list by
first inserting a element into allcg_list and then initializing the
inserted list element. The initialization reset the element's
prev/next fields forming a degenerate list where allcg_list pointed to
element, but element pointed to itself. This problem was introduced
in 2243076ad128 "cgroup: initialize cgrp->allcg_node in
init_cgroup_housekeeping()". CONFIG_DEBUG_LIST reported a list_add
corruption in cgroup_mkdir() running next-20121127 (ce2931a).

This patch fixes the problem by performing element initialization
before insertion.

Signed-off-by: Greg Thelen <[email protected]>
---
kernel/cgroup.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 01d5342..ece60d4 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1394,6 +1394,7 @@ static void init_cgroup_root(struct cgroupfs_root *root)
{
struct cgroup *cgrp = &root->top_cgroup;

+ init_cgroup_housekeeping(cgrp);
INIT_LIST_HEAD(&root->subsys_list);
INIT_LIST_HEAD(&root->root_list);
INIT_LIST_HEAD(&root->allcg_list);
@@ -1401,7 +1402,6 @@ static void init_cgroup_root(struct cgroupfs_root *root)
cgrp->root = root;
cgrp->top_cgroup = cgrp;
list_add_tail(&cgrp->allcg_node, &root->allcg_list);
- init_cgroup_housekeeping(cgrp);
}

static bool init_root_id(struct cgroupfs_root *root)
--
1.7.7.3

2012-11-28 18:29:19

by Tejun Heo

Subject: Re: [PATCH] cgroup: avoid creating degenerate allcg_list

Hey, Greg.

On Wed, Nov 28, 2012 at 10:26:32AM -0800, Greg Thelen wrote:
> Before this patch init_cgroup_root() created a degenerate list by
> first inserting a element into allcg_list and then initializing the
> inserted list element. The initialization reset the element's
> prev/next fields forming a degenerate list where allcg_list pointed to
> element, but element pointed to itself. This problem was introduced
> in 2243076ad128 "cgroup: initialize cgrp->allcg_node in
> init_cgroup_housekeeping()". CONFIG_DEBUG_LIST reported a list_add
> corruption in cgroup_mkdir() running next-20121127 (ce2931a).
>
> This patch fixes the problem by performing element initialization
> before insertion.

You're beaten by Li Zhong by 9 hrs. :)

http://thread.gmane.org/gmane.linux.kernel.next/25096

--
tejun