This is a note to let you know that I've just added the patch titled
cgroups: if you list_empty() a head then don't list_del() it
to the 2.6.38-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:
cgroups-if-you-list_empty-a-head-then-don-t-list_del-it.patch
and it can be found in the queue-2.6.38 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 8d2587970b8bdf7c8d9208e3f4bb93182aef1a0f Mon Sep 17 00:00:00 2001
From: Phil Carmody <[email protected]>
Date: Tue, 22 Mar 2011 16:30:13 -0700
Subject: cgroups: if you list_empty() a head then don't list_del() it
From: Phil Carmody <[email protected]>
commit 8d2587970b8bdf7c8d9208e3f4bb93182aef1a0f upstream.
list_del() leaves poison in the prev and next pointers. The next
list_empty() will compare those poisons, and say the list isn't empty.
Any list operations that assume the node is on a list because of such a
check will be fooled into dereferencing poison. One needs to INIT the
node after the del, and fortunately there's already a wrapper for that -
list_del_init().
Some of the dels are followed by deallocations, so can be ignored, and one
can be merged with an add to make a move. Apart from that, I erred on the
side of caution in making nodes list_empty()-queriable.
Signed-off-by: Phil Carmody <[email protected]>
Reviewed-by: Paul Menage <[email protected]>
Cc: Li Zefan <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
kernel/cgroup.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1813,10 +1813,8 @@ int cgroup_attach_task(struct cgroup *cg
/* Update the css_set linked lists if we're using them */
write_lock(&css_set_lock);
- if (!list_empty(&tsk->cg_list)) {
- list_del(&tsk->cg_list);
- list_add(&tsk->cg_list, &newcg->tasks);
- }
+ if (!list_empty(&tsk->cg_list))
+ list_move(&tsk->cg_list, &newcg->tasks);
write_unlock(&css_set_lock);
for_each_subsys(root, ss) {
@@ -3655,12 +3653,12 @@ again:
spin_lock(&release_list_lock);
set_bit(CGRP_REMOVED, &cgrp->flags);
if (!list_empty(&cgrp->release_list))
- list_del(&cgrp->release_list);
+ list_del_init(&cgrp->release_list);
spin_unlock(&release_list_lock);
cgroup_lock_hierarchy(cgrp->root);
/* delete this cgroup from parent->children */
- list_del(&cgrp->sibling);
+ list_del_init(&cgrp->sibling);
cgroup_unlock_hierarchy(cgrp->root);
d = dget(cgrp->dentry);
@@ -3879,7 +3877,7 @@ void cgroup_unload_subsys(struct cgroup_
subsys[ss->subsys_id] = NULL;
/* remove subsystem from rootnode's list of subsystems */
- list_del(&ss->sibling);
+ list_del_init(&ss->sibling);
/*
* disentangle the css from all css_sets attached to the dummytop. as
@@ -4253,7 +4251,7 @@ void cgroup_exit(struct task_struct *tsk
if (!list_empty(&tsk->cg_list)) {
write_lock(&css_set_lock);
if (!list_empty(&tsk->cg_list))
- list_del(&tsk->cg_list);
+ list_del_init(&tsk->cg_list);
write_unlock(&css_set_lock);
}
Patches currently in stable-queue which might be from
[email protected] are
queue-2.6.38/cgroups-if-you-list_empty-a-head-then-don-t-list_del-it.patch
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