netdev - [PATCH 1/1] ipv4: off-by-one in continuation handling in /proc/net/route

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 13 Aug 2015 11:21:07 +0100
From:	Andy Whitcroft <apw@...onical.com>
To:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andy Whitcroft <apw@...onical.com>
Subject: [PATCH 1/1] ipv4: off-by-one in continuation handling in /proc/net/route

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 </proc/net/route >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 <apw@...onical.com>
---
 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 netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html