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Revert "defer call to mem_cgroup_sk_alloc()" 

This patch effectively reverts commit 9f1c2674b3 ("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 c0576e3975 ("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 <guro@fb.com>
Cc: Eric Dumazet <edumazet@google.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Roman Gushchin 2018-02-02 15:26:57 +00:00 committed by David S. Miller
parent 4db428a7c9
commit edbe69ef2c
3 changed files with 15 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
mm/memcontrol.c
View File

@ -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)

5
net/core/sock.c
View File

@ -1683,16 +1683,13 @@ struct sock *sk_clone_lock(const struct sock *sk, const gfp_t priority)
newsk->sk_dst_pending_confirm = 0;
newsk->sk_wmem_queued = 0;
newsk->sk_forward_alloc = 0;
/* sk->sk_memcg will be populated at accept() time */
newsk->sk_memcg = NULL;
atomic_set(&newsk->sk_drops, 0);
newsk->sk_send_head = NULL;
newsk->sk_userlocks = sk->sk_userlocks & ~SOCK_BINDPORT_LOCK;
atomic_set(&newsk->sk_zckey, 0);
sock_reset_flag(newsk, SOCK_DONE);
mem_cgroup_sk_alloc(newsk);
cgroup_sk_alloc(&newsk->sk_cgrp_data);
rcu_read_lock();

1
net/ipv4/inet_connection_sock.c
View File

@ -475,7 +475,6 @@ struct sock *inet_csk_accept(struct sock *sk, int flags, int *err, bool kern)
}
spin_unlock_bh(&queue->fastopenq.lock);
}
mem_cgroup_sk_alloc(newsk);
out:
release_sock(sk);
if (req)