cgroup: fix unbalanced locking

cgroup_pidlist_start() holds cgrp->pidlist_mutex and then calls
pidlist_array_load(), and cgroup_pidlist_stop() releases the mutex.

It is wrong that we release the mutex in the failure path in
pidlist_array_load(), because cgroup_pidlist_stop() will be called
no matter if cgroup_pidlist_start() returns errno or not.

Fixes: 4bac00d16a8760eae7205e41d2c246477d42a210
Cc: <stable@vger.kernel.org> # 3.14+
Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 940aced..3a73f99 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3985,7 +3985,6 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
 
        l = cgroup_pidlist_find_create(cgrp, type);
        if (!l) {
-               mutex_unlock(&cgrp->pidlist_mutex);
                pidlist_free(array);
                return -ENOMEM;
        }