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authorTejun Heo <tj@kernel.org>2013-11-27 18:16:21 -0500
committerTejun Heo <tj@kernel.org>2013-11-27 18:16:21 -0500
commite605b36575e896edd8161534550c9ea021b03bc0 (patch)
tree3505166d31674b264cc00f7a5fa6836f6f7b35cf /kernel
parent0fc0287c9ed1ffd3706f8b4d9b314aa102ef1245 (diff)
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
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup.c5
1 files changed, 4 insertions, 1 deletions
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;
}