cgroup: fix the retry path of cgroup_mount()

If we hit the retry path, we'll call parse_cgroupfs_options() again,
but the string we pass to it has been modified by the previous call
to this function.

This bug can be observed by:

  # mount -t cgroup -o name=foo,cpuset xxx /mnt && umount /mnt && \
    mount -t cgroup -o name=foo,cpuset xxx /mnt
  mount: wrong fs type, bad option, bad superblock on xxx,
         missing codepage or helper program, or other error
  ...

The second mount passed "name=foo,cpuset" to the parser, and then it
hit the retry path and call the parser again, but this time the string
passed to the parser is "name=foo".

To fix this, we avoid calling parse_cgroupfs_options() again in this
case.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 9fcdaa705b6c..11a03d67635a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1495,7 +1495,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
          */
         if (!use_task_css_set_links)
                 cgroup_enable_task_cg_lists();
-retry:
+
         mutex_lock(&cgroup_tree_mutex);
         mutex_lock(&cgroup_mutex);
 
@@ -1503,7 +1503,7 @@ retry:
         ret = parse_cgroupfs_options(data, &opts);
         if (ret)
                 goto out_unlock;
-
+retry:
         /* look for a matching existing root */
         if (!opts.subsys_mask && !opts.none && !opts.name) {
                 cgrp_dfl_root_visible = true;
@@ -1562,9 +1562,9 @@ retry:
                 if (!atomic_inc_not_zero(&root->cgrp.refcnt)) {
                         mutex_unlock(&cgroup_mutex);
                         mutex_unlock(&cgroup_tree_mutex);
-                        kfree(opts.release_agent);
-                        kfree(opts.name);
                         msleep(10);
+                        mutex_lock(&cgroup_tree_mutex);
+                        mutex_lock(&cgroup_mutex);
                         goto retry;
                 }