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memcg, tcp_kmem: check for cg_proto in sock_update_memcg

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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>
This commit is contained in:
Michal Hocko 2015-09-08 15:01:13 -07:00 committed by Linus Torvalds
parent 9f2115f93b
commit a03f1f0589
1 changed files with 1 additions and 2 deletions
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3
mm/memcontrol.c
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@ -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;
}