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: Ubuntu-5.10.0-12.13~10185^2~1 X-Git-Url: https://git.proxmox.com/?a=commitdiff_plain;h=33c35aa4817864e056fd772230b0c6b552e36ea2;p=mirror_ubuntu-hirsute-kernel.git 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: Waiman Long Signed-off-by: Tejun Heo Cc: stable@vger.kernel.org # v4.5+ --- diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h index 21745946cae1..ec47101cb1bf 100644 --- a/include/linux/cgroup-defs.h +++ b/include/linux/cgroup-defs.h @@ -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 */ diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index c3c9a0e1b3c9..8d4e85eae42c 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -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.