From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752286AbdIIWer (ORCPT ); Sat, 9 Sep 2017 18:34:47 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:41756 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751970AbdIIWYx (ORCPT ); Sat, 9 Sep 2017 18:24:53 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Neal Cardwell" , "Yuchung Cheng" , "Eric Dumazet" , "Soheil Hassas Yeganeh" , "David S. Miller" Date: Sat, 09 Sep 2017 22:47:14 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 010/233] tcp: avoid fragmenting peculiar skbs in SACK In-Reply-To: X-SA-Exim-Connect-IP: 2a02:8011:400e:2:6f00:88c8:c921:d332 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.48-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Yuchung Cheng commit b451e5d24ba6687c6f0e7319c727a709a1846c06 upstream. This patch fixes a bug in splitting an SKB during SACK processing. Specifically if an skb contains multiple packets and is only partially sacked in the higher sequences, tcp_match_sack_to_skb() splits the skb and marks the second fragment as SACKed. The current code further attempts rounding up the first fragment to MSS boundaries. But it misses a boundary condition when the rounded-up fragment size (pkt_len) is exactly skb size. Spliting such an skb is pointless and causses a kernel warning and aborts the SACK processing. This patch universally checks such over-split before calling tcp_fragment to prevent these unnecessary warnings. Fixes: adb92db857ee ("tcp: Make SACK code to split only at mss boundaries") Signed-off-by: Yuchung Cheng Signed-off-by: Eric Dumazet Signed-off-by: Soheil Hassas Yeganeh Acked-by: Neal Cardwell Signed-off-by: David S. Miller Signed-off-by: Ben Hutchings --- net/ipv4/tcp_input.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1160,13 +1160,14 @@ static int tcp_match_skb_to_sack(struct */ if (pkt_len > mss) { unsigned int new_len = (pkt_len / mss) * mss; - if (!in_sack && new_len < pkt_len) { + if (!in_sack && new_len < pkt_len) new_len += mss; - if (new_len >= skb->len) - return 0; - } pkt_len = new_len; } + + if (pkt_len >= skb->len && !in_sack) + return 0; + err = tcp_fragment(sk, skb, pkt_len, mss, GFP_ATOMIC); if (err < 0) return err;