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 <redacted>
---
Op 30-07-09 00:02, Jarek Poplawski schreef:

Roel Kluin wrote, On 07/29/2009 12:52 PM:

quoted

-	hbuffer[--k] = 0;
+	if (k != 0)
+		hbuffer[--k] = 0;

I guess for k == 0 we need hbuffer[0] = 0 too.

Jarek P.

Thanks, updated patch below.

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