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cgroup: Prevent kill_css() from being called more than once

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commit 33c35aa4817864e056fd772230b0c6b552e36ea2 upstream.

The kill_css() function may be called more than once under the condition
that the css was killed but not physically removed yet followed by the
removal of the cgroup that is hosting the css. This patch prevents any
harmm from being done when that happens.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Waiman Long 2017-05-15 09:34:06 -04:00 committed by Greg Kroah-Hartman
parent b59ec7072c
commit dff4c8bb13
2 changed files with 6 additions and 0 deletions
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1
include/linux/cgroup-defs.h
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@ -46,6 +46,7 @@ enum {
CSS_ONLINE = (1 << 1), /* between ->css_online() and ->css_offline() */
CSS_RELEASED = (1 << 2), /* refcnt reached zero, released */
CSS_VISIBLE = (1 << 3), /* css is visible to userland */
CSS_DYING = (1 << 4), /* css is dying */
};
/* bits in struct cgroup flags field */

5
kernel/cgroup.c
View File

@ -5407,6 +5407,11 @@ static void kill_css(struct cgroup_subsys_state *css)
{
lockdep_assert_held(&cgroup_mutex);
if (css->flags & CSS_DYING)
return;
css->flags |= CSS_DYING;
/*
* This must happen before css is disassociated with its cgroup.
* See seq_css() for details.