From edbe69ef2c90fc86998a74b08319a01c508bd497 Mon Sep 17 00:00:00 2001 From: Roman Gushchin Date: Fri, 2 Feb 2018 15:26:57 +0000 Subject: Revert "defer call to mem_cgroup_sk_alloc()" This patch effectively reverts commit 9f1c2674b328 ("net: memcontrol: defer call to mem_cgroup_sk_alloc()"). Moving mem_cgroup_sk_alloc() to the inet_csk_accept() completely breaks memcg socket memory accounting, as packets received before memcg pointer initialization are not accounted and are causing refcounting underflow on socket release. Actually the free-after-use problem was fixed by commit c0576e397508 ("net: call cgroup_sk_alloc() earlier in sk_clone_lock()") for the cgroup pointer. So, let's revert it and call mem_cgroup_sk_alloc() just before cgroup_sk_alloc(). This is safe, as we hold a reference to the socket we're cloning, and it holds a reference to the memcg. Also, let's drop BUG_ON(mem_cgroup_is_root()) check from mem_cgroup_sk_alloc(). I see no reasons why bumping the root memcg counter is a good reason to panic, and there are no realistic ways to hit it. Signed-off-by: Roman Gushchin Cc: Eric Dumazet Cc: David S. Miller Cc: Johannes Weiner Cc: Tejun Heo Signed-off-by: David S. Miller --- mm/memcontrol.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'mm/memcontrol.c') diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0ae2dc3a1748..0937f2c52c7d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5747,6 +5747,20 @@ void mem_cgroup_sk_alloc(struct sock *sk) if (!mem_cgroup_sockets_enabled) return; + /* + * Socket cloning can throw us here with sk_memcg already + * filled. It won't however, necessarily happen from + * process context. So the test for root memcg given + * the current task's memcg won't help us in this case. + * + * Respecting the original socket's memcg is a better + * decision in this case. + */ + if (sk->sk_memcg) { + css_get(&sk->sk_memcg->css); + return; + } + rcu_read_lock(); memcg = mem_cgroup_from_task(current); if (memcg == root_mem_cgroup) -- cgit v1.2.3-55-g7522