cgroup: Prevent kill_css() from being called more than once (33c35aa4) · Commits · 戴 / test

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> Cc: stable@vger.kernel.org # v4.5+

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.

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