Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753220AbbHMQHn (ORCPT ); Thu, 13 Aug 2015 12:07:43 -0400 Received: from mail-pa0-f53.google.com ([209.85.220.53]:36260 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752227AbbHMQHl (ORCPT ); Thu, 13 Aug 2015 12:07:41 -0400 Subject: Re: [PATCH 1/1] ipv4: off-by-one in continuation handling in /proc/net/route To: Eric Dumazet , Andy Whitcroft , Alexander Duyck References: <1439461267-10627-1-git-send-email-apw@canonical.com> <1439478658.7960.10.camel@edumazet-glaptop2.roam.corp.google.com> Cc: "David S. Miller" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy , netdev@vger.kernel.org, linux-kernel@vger.kernel.org From: Alexander Duyck Message-ID: <55CCC0CB.6030309@gmail.com> Date: Thu, 13 Aug 2015 09:07:39 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: <1439478658.7960.10.camel@edumazet-glaptop2.roam.corp.google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2145 Lines: 50 On 08/13/2015 08:10 AM, Eric Dumazet wrote: > On Thu, 2015-08-13 at 11:21 +0100, Andy Whitcroft wrote: >> When generating /proc/net/route we emit a header followed by a line for >> each route. When a short read is performed we will restart this process >> based on the open file descriptor. When calculating the start point we >> fail to take into account that the 0th entry is the header. This leads >> us to skip the first entry when doing a continuation read. >> >> This can be easily seen with the comparison below: >> >> while read l; do echo "$l"; done A >> cat /proc/net/route >B >> diff -bu A B | grep '^[+-]' >> >> On my example machine I have approximatly 10KB of route output. There we >> see the very first non-title element is lost in the while read case, >> and an entry around the 8K mark in the cat case: >> >> +wlan0 00000000 02021EAC 0003 0 0 400 00000000 0 0 0 >> -tun1 00C0AC0A 00000000 0001 0 0 950 00C0FFFF 0 0 0 >> >> Fix up the off-by-one when reaquiring position on continuation. >> >> BugLink: http://bugs.launchpad.net/bugs/1483440 >> Signed-off-by: Andy Whitcroft >> --- >> net/ipv4/fib_trie.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> From code inspection I belive this was introduced by the Fixes >> below, but I have not tested this to confirm. >> >> Fixes: 8be33e955cb9 ("ipv4: off-by-one in continuation handling in /proc/net/route") > You probably meant > > Fixes: 8be33e955cb9 ("fib_trie: Fib walk rcu should take a tnode and key instead of a trie and a leaf") > > CC Alexander for review/comment I agree the Fixes line needs to be updated. Other than that the fix looks good. Once you get the comment fixed feel free to add my acked-by. Also you might call out that this is needed for net, and 4.1 stable as well. Acked-by: Alexander Duyck -- 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/