[PATCH 5.3 020/105] cgroup: dont put ERR_PTR() into fc->root

[Greg Kroah-Hartman]

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

[ Upstream commit 630faf81b3e61bcc90dc6d8b497800657d2752a5 ]

the caller of ->get_tree() expects NULL left there on error...

Reported-by: Thibaut Sautereau <thibaut@xxxxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 kernel/cgroup/cgroup.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 8be1da1ebd9a4..f23862fa15146 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -2119,11 +2119,12 @@ int cgroup_do_get_tree(struct fs_context *fc)
 
 		nsdentry = kernfs_node_dentry(cgrp->kn, sb);
 		dput(fc->root);
-		fc->root = nsdentry;
 		if (IS_ERR(nsdentry)) {
-			ret = PTR_ERR(nsdentry);
 			deactivate_locked_super(sb);
+			ret = PTR_ERR(nsdentry);
+			nsdentry = NULL;
 		}
+		fc->root = nsdentry;
 	}
 
 	if (!ctx->kfc.new_sb_created)
-- 
2.20.1