[SRU Bionic] cgroup: add missing skcd->no_refcnt check in cgroup_sk_clone()

[Thadeu Lima de Souza Cascardo]

From: Yang Yingliang <yangyingliang at huawei.com>

BugLink: https://bugs.launchpad.net/bugs/1886860

Add skcd->no_refcnt check which is missed when backporting
ad0f75e5f57c ("cgroup: fix cgroup_sk_alloc() for sk_clone_lock()").

This patch is needed in stable-4.9, stable-4.14 and stable-4.19.

Signed-off-by: Yang Yingliang <yangyingliang at huawei.com>
Signed-off-by: Sasha Levin <sashal at kernel.org>
(cherry picked from commit 1bfba2f4270c64c912756fc76621bbce959ddf2e linux-4.14.y)
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo at canonical.com>
---
 kernel/cgroup/cgroup.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 963ec350d07e..37ca9b4b04b2 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -5919,6 +5919,8 @@ void cgroup_sk_clone(struct sock_cgroup_data *skcd)
 {
 	/* Socket clone path */
 	if (skcd->val) {
+		if (skcd->no_refcnt)
+			return;
 		/*
 		 * We might be cloning a socket which is left in an empty
 		 * cgroup and the cgroup might have already been rmdir'd.
-- 
2.25.1