Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752401AbbHMKVM (ORCPT ); Thu, 13 Aug 2015 06:21:12 -0400 Received: from mail-wi0-f181.google.com ([209.85.212.181]:38453 "EHLO mail-wi0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751998AbbHMKVK (ORCPT ); Thu, 13 Aug 2015 06:21:10 -0400 From: Andy Whitcroft To: "David S. Miller" , Alexey Kuznetsov , James Morris , Hideaki YOSHIFUJI , Patrick McHardy Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Whitcroft Subject: [PATCH 1/1] ipv4: off-by-one in continuation handling in /proc/net/route Date: Thu, 13 Aug 2015 11:21:07 +0100 Message-Id: <1439461267-10627-1-git-send-email-apw@canonical.com> X-Mailer: git-send-email 2.5.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1849 Lines: 53 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") diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c index 37c4bb8..b0c6258 100644 --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -2465,7 +2465,7 @@ static struct key_vector *fib_route_get_idx(struct fib_route_iter *iter, key = l->key + 1; iter->pos++; - if (pos-- <= 0) + if (--pos <= 0) break; l = NULL; -- 2.5.0 -- 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/