From: Michal Hocko <mhocko@suse.cz>
Date: Tue, 8 Sep 2015 22:01:13 +0000 (-0700)
Subject: memcg, tcp_kmem: check for cg_proto in sock_update_memcg
X-Git-Tag: v4.3-rc1~40^2~80
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a03f1f058969ec350fb7451a6fbca23096ee5727;p=platform%2Fkernel%2Flinux-exynos.git

memcg, tcp_kmem: check for cg_proto in sock_update_memcg

sk_prot->proto_cgroup is allowed to return NULL but sock_update_memcg
doesn't check for NULL.  The function relies on the mem_cgroup_is_root
check because we shouldn't get NULL otherwise because mem_cgroup_from_task
will always return !NULL.

All other callers are checking for NULL and we can safely replace
mem_cgroup_is_root() check by cg_proto != NULL which will be more
straightforward (proto_cgroup returns NULL for the root memcg already).

Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 191d8aa..3033e6c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -315,8 +315,7 @@ void sock_update_memcg(struct sock *sk)
 		rcu_read_lock();
 		memcg = mem_cgroup_from_task(current);
 		cg_proto = sk->sk_prot->proto_cgroup(memcg);
-		if (!mem_cgroup_is_root(memcg) &&
-		    memcg_proto_active(cg_proto) &&
+		if (cg_proto && memcg_proto_active(cg_proto) &&
 		    css_tryget_online(&memcg->css)) {
 			sk->sk_cgrp = cg_proto;
 		}