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authorTejun Heo <tj@kernel.org>2013-11-27 18:16:21 -0500
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-04 11:05:55 -0800
commite6af24fef5c9ed17a25f062b3c22c3df44904dc9 (patch)
parent65d6ec10c7cf2575de2aa9159f8cf43cbc1074fe (diff)
cgroup: fix cgroup_subsys_state leak for seq_files
commit e605b36575e896edd8161534550c9ea021b03bc0 upstream. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c422bc50d017..5c9127dc1b66 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -231,6 +231,7 @@ 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
@@ -2471,7 +2472,7 @@ 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)
@@ -2532,6 +2533,8 @@ static int cgroup_file_release(struct inode *inode, struct file *file)
ret = cft->release(inode, file);
if (css->ss)
+ if (file->f_op == &cgroup_seqfile_operations)
+ single_release(inode, file);
return ret;