linux-kernel - [PATCH 4.4 34/68] cgroup: set css->id to -1 during init

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Date:	Mon,  8 Aug 2016 21:11:09 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	Wenwei Tao <ww.tao0320@...il.com>
Subject: [PATCH 4.4 34/68] cgroup: set css->id to -1 during init

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tejun Heo <tj@...nel.org>

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

---
 kernel/cgroup.c |    1 +
 1 file changed, 1 insertion(+)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4793,6 +4793,7 @@ static void init_and_link_css(struct cgr
 	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++;