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Commit 33c35aa4 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
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cgroup: Prevent kill_css() from being called more than once 



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: default avatarWaiman Long <longman@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # v4.5+
parent 2ea659a9

include/linux/cgroup-defs.h

+1 −0
Original line number Diff line number Diff line
@@ -48,6 +48,7 @@ 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 */

kernel/cgroup/cgroup.c

+5 −0
Original line number Diff line number Diff line
@@ -4265,6 +4265,11 @@ 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.