Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758571Ab2EIIQb (ORCPT ); Wed, 9 May 2012 04:16:31 -0400 Received: from mail-yw0-f46.google.com ([209.85.213.46]:61306 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750797Ab2EIIQ2 (ORCPT ); Wed, 9 May 2012 04:16:28 -0400 Date: Wed, 9 May 2012 03:16:17 -0500 From: Jonathan Nieder To: Ben Hutchings Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Eric Dumazet , Vijay Subramanian , "David S. Miller" Subject: Re: [ 074/167] [PATCH 14/26] tcp: fix tcp_trim_head() Message-ID: <20120509081617.GD32230@burratino> References: <20120509055029.588587017@decadent.org.uk> <20120509055040.099618905@decadent.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120509055040.099618905@decadent.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2152 Lines: 66 Ben Hutchings wrote: > 3.2-stable review patch. If anyone has any objections, please let me know. [...] > [ Upstream commit 4fa48bf3c75069d636fc8830743c929a062e80dc ] > > commit f07d960df3 (tcp: avoid frag allocation for small frames) > breaked assumption in tcp stack that skb is either linear (skb->data_len > == 0), or fully fragged (skb->data_len == skb->len) > > tcp_trim_head() made this assumption, we must fix it. Is this needed in the context of 3.2.y (which does not include f07d960df3)? Curious, Jonathan > Thanks to Vijay for providing a very detailed explanation. > > Reported-by: Vijay Subramanian > Signed-off-by: Eric Dumazet > Signed-off-by: David S. Miller > Signed-off-by: Ben Hutchings > --- > net/ipv4/tcp_output.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > index 097e0c7..7413437 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -1093,6 +1093,13 @@ static void __pskb_trim_head(struct sk_buff *skb, int len) > { > int i, k, eat; > > + eat = min_t(int, len, skb_headlen(skb)); > + if (eat) { > + __skb_pull(skb, eat); > + len -= eat; > + if (!len) > + return; > + } > eat = len; > k = 0; > for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { > @@ -1124,11 +1131,7 @@ int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) > if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) > return -ENOMEM; > > - /* If len == headlen, we avoid __skb_pull to preserve alignment. */ > - if (unlikely(len < skb_headlen(skb))) > - __skb_pull(skb, len); > - else > - __pskb_trim_head(skb, len - skb_headlen(skb)); > + __pskb_trim_head(skb, len); > > TCP_SKB_CB(skb)->seq += len; > skb->ip_summed = CHECKSUM_PARTIAL; > -- > 1.7.10 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/