From mboxrd@z Thu Jan 1 00:00:00 1970 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755048AbdBETdj (ORCPT + 2 others); Sun, 5 Feb 2017 14:33:39 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:28568 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754902AbdBET3Y (ORCPT ); Sun, 5 Feb 2017 14:29:24 -0500 From: Willy Tarreau To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, linux@roeck-us.net Cc: Eric Dumazet , "David S . Miller" , Willy Tarreau Subject: [PATCH 3.10 254/319] net: avoid sk_forward_alloc overflows Date: Sun, 5 Feb 2017 20:21:16 +0100 Message-Id: <1486322541-8206-155-git-send-email-w@1wt.eu> X-Mailer: git-send-email 2.8.0.rc2.1.gbe9624a In-Reply-To: <1486322541-8206-1-git-send-email-w@1wt.eu> References: <1486322541-8206-1-git-send-email-w@1wt.eu> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: From: Eric Dumazet commit 20c64d5cd5a2bdcdc8982a06cb05e5e1bd851a3d upstream. 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 Signed-off-by: David S. Miller Signed-off-by: Willy Tarreau --- include/net/sock.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/include/net/sock.h b/include/net/sock.h index 6d2fbac..a46dd30 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1422,6 +1422,16 @@ static inline void sk_mem_uncharge(struct sock *sk, int size) if (!sk_has_account(sk)) return; sk->sk_forward_alloc += size; + + /* Avoid a possible overflow. + * TCP send queues can make this happen, if sk_mem_reclaim() + * is not called and more than 2 GBytes are released at once. + * + * If we reach 2 MBytes, reclaim 1 MBytes right now, there is + * no need to hold that much forward allocation anyway. + */ + if (unlikely(sk->sk_forward_alloc >= 1 << 21)) + __sk_mem_reclaim(sk, 1 << 20); } static inline void sk_wmem_free_skb(struct sock *sk, struct sk_buff *skb) -- 2.8.0.rc2.1.gbe9624a