From: Tejun Heo <tj@kernel.org>
Date: Wed, 27 Nov 2013 23:16:21 +0000 (-0500)
Subject: cgroup: fix cgroup_subsys_state leak for seq_files
X-Git-Tag: v3.13-rc2~6^2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e605b36575e896edd8161534550c9ea021b03bc0;p=pandora-kernel.git

cgroup: fix cgroup_subsys_state leak for seq_files

If a cgroup file implements either read_map() or read_seq_string(),
such file is served using seq_file by overriding file->f_op to
cgroup_seqfile_operations, which also overrides the release method to
single_release() from cgroup_file_release().

Because cgroup_file_open() didn't use to acquire any resources, this
used to be fine, but since f7d58818ba42 ("cgroup: pin
cgroup_subsys_state when opening a cgroupfs file"), cgroup_file_open()
pins the css (cgroup_subsys_state) which is put by
cgroup_file_release().  The patch forgot to update the release path
for seq_files and each open/release cycle leaks a css reference.

Fix it by updating cgroup_file_release() to also handle seq_files and
using it for seq_file release path too.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # v3.12
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