4.14-stable review patch. If anyone has any objections, please let me know.
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From: Roman Gushchin guro@fb.com
[ Upstream commit edbe69ef2c90fc86998a74b08319a01c508bd497 ]
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 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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/memcontrol.c | 14 ++++++++++++++ net/core/sock.c | 5 +---- net/ipv4/inet_connection_sock.c | 1 - 3 files changed, 15 insertions(+), 5 deletions(-)
--- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5828,6 +5828,20 @@ 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) --- a/net/core/sock.c +++ b/net/core/sock.c @@ -1677,16 +1677,13 @@ struct sock *sk_clone_lock(const struct 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(); --- a/net/ipv4/inet_connection_sock.c +++ b/net/ipv4/inet_connection_sock.c @@ -475,7 +475,6 @@ struct sock *inet_csk_accept(struct sock } spin_unlock_bh(&queue->fastopenq.lock); } - mem_cgroup_sk_alloc(newsk); out: release_sock(sk); if (req)