From e605b36575e896edd8161534550c9ea021b03bc0 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Wed, 27 Nov 2013 18:16:21 -0500 Subject: [PATCH] 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 Cc: stable@vger.kernel.org # v3.12 --- kernel/cgroup.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index a7b98ee35ef7..8b729c278b64 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -199,6 +199,7 @@ static void cgroup_destroy_css_killed(struct cgroup *cgrp); static int cgroup_destroy_locked(struct cgroup *cgrp); static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[], bool is_add); +static int cgroup_file_release(struct inode *inode, struct file *file); /** * cgroup_css - obtain a cgroup's css for the specified subsystem @@ -2429,7 +2430,7 @@ static const struct file_operations cgroup_seqfile_operations = { .read = seq_read, .write = cgroup_file_write, .llseek = seq_lseek, - .release = single_release, + .release = cgroup_file_release, }; static int cgroup_file_open(struct inode *inode, struct file *file) @@ -2490,6 +2491,8 @@ static int cgroup_file_release(struct inode *inode, struct file *file) ret = cft->release(inode, file); if (css->ss) css_put(css); + if (file->f_op == &cgroup_seqfile_operations) + single_release(inode, file); return ret; } -- 2.39.2