From: Michal Hocko <mhocko@xxxxxxx>
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).
Reviewed-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxx>
---
mm/memcontrol.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5d4fba8cbdd0..cf9fb1f41831 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;
}
--
2.1.4
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