blk-mq: protect debugfs_create_files() from failures

If debugfs were to return a non-NULL error for a debugfs call, using
that pointer later in debugfs_create_files() would crash.

Fix that by properly checking the pointer before referencing it.

Reported-by: Michal Hocko <mhocko@kernel.org>
Reported-and-tested-by: syzbot+b382ba6a802a3d242790@syzkaller.appspotmail.com
Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 90d6876..777638f 100644 (file)
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -838,6 +838,9 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_ctx_attrs[] = {
 static bool debugfs_create_files(struct dentry *parent, void *data,
                                 const struct blk_mq_debugfs_attr *attr)
 {
+       if (IS_ERR_OR_NULL(parent))
+               return false;
+
        d_inode(parent)->i_private = data;
 
        for (; attr->name; attr++) {