From: Waiman Long Date: Mon, 15 May 2017 13:34:06 +0000 (-0400) Subject: cgroup: Prevent kill_css() from being called more than once X-Git-Tag: archive/raspbian/4.9.30-2+deb9u2+rpi1~4^2~516 X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=c5691b452ad7b461b2765c7faaecafca226ed62a;p=linux-4.9.git cgroup: Prevent kill_css() from being called more than once 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 Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 5b17de62c962..6fb1c34cf805 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -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 */ diff --git a/kernel/cgroup.c b/kernel/cgroup.c index e9ec63d7bc04..84f45a33d69f 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -5412,6 +5412,11 @@ 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.