From: Tejun Heo <tj@kernel.org>
Date: Thu, 26 May 2016 19:42:13 +0000 (-0400)
Subject: cgroup: set css->id to -1 during init
X-Git-Tag: v4.6.6~49
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=65856851b6229563e43e256b3932d5c8513c047b;p=thirdparty%2Fkernel%2Fstable.git

cgroup: set css->id to -1 during init

commit 8fa3b8d689a54d6d04ff7803c724fb7aca6ce98e upstream.

If percpu_ref initialization fails during css_create(), the free path
can end up trying to free css->id of zero.  As ID 0 is unused, it
doesn't cause a critical breakage but it does trigger a warning
message.  Fix it by setting css->id to -1 from init_and_link_css().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Wenwei Tao <ww.tao0320@gmail.com>
Fixes: 01e586598b22 ("cgroup: release css->id after css_free")
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 789b84f973c92..688eb0cd18517 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5063,6 +5063,7 @@ static void init_and_link_css(struct cgroup_subsys_state *css,
 	memset(css, 0, sizeof(*css));
 	css->cgroup = cgrp;
 	css->ss = ss;
+	css->id = -1;
 	INIT_LIST_HEAD(&css->sibling);
 	INIT_LIST_HEAD(&css->children);
 	css->serial_nr = css_serial_nr_next++;