From: roel kluin <roel.kluin@gmail.com>
Date: Wed, 29 Jul 2009 23:46:59 +0000 (+0000)
Subject: ipv4: ARP neigh procfs buffer overflow
X-Git-Tag: v2.6.31-rc6~41^2~26
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=a3e8ee682003685b8b9c98c89340a42e48c3e813;p=platform%2Fkernel%2Flinux-3.10.git

ipv4: ARP neigh procfs buffer overflow

If arp_format_neigh_entry() can be called with n->dev->addr_len == 0, then a
write to hbuffer[-1] occurs.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index c29d75d..090e999 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1304,7 +1304,9 @@ static void arp_format_neigh_entry(struct seq_file *seq,
 		hbuffer[k++] = hex_asc_lo(n->ha[j]);
 		hbuffer[k++] = ':';
 	}
-	hbuffer[--k] = 0;
+	if (k != 0)
+		--k;
+	hbuffer[k] = 0;
 #if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
 	}
 #endif