From: Eric Dumazet <eric.duma...@gmail.com>
Date: Thu, 15 Sep 2016 08:48:46 -0700
> From: Eric Dumazet <eduma...@google.com>
> A malicious TCP receiver, sending SACK, can force the sender to split
> skbs in write queue and increase its memory usage.
> Then, when socket is closed and its write queue purged, we might
> overflow sk_forward_alloc (It becomes negative)
> sk_mem_reclaim() does nothing in this case, and more than 2GB
> are leaked from TCP perspective (tcp_memory_allocated is not changed)
> Then warnings trigger from inet_sock_destruct() and
> sk_stream_kill_queues() seeing a not zero sk_forward_alloc
> All TCP stack can be stuck because TCP is under memory pressure.
> A simple fix is to preemptively reclaim from sk_mem_uncharge().
> This makes sure a socket wont have more than 2 MB forward allocated,
> after burst and idle period.
> Signed-off-by: Eric Dumazet <eduma...@google.com>