From: Tony Cheneau <tony.cheneau@amnesiak.org>
Date: Wed, 11 Jul 2012 06:51:14 +0000 (+0000)
Subject: 6lowpan: Fix null pointer dereference in UDP uncompression function
X-Git-Tag: firefly_0821_release~3680^2~2381^2~164
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d4787a15432384826a0bed42d189fc2a97dc73ea;p=firefly-linux-kernel-4.4.55.git

6lowpan: Fix null pointer dereference in UDP uncompression function

When a UDP packet gets fragmented, a crash will occur at reassembly time.
This is because skb->transport_header is not set during earlier period of fragment reassembly.
As a consequence, call to udp_hdr() return NULL and uh (which is NULL) gets
dereferenced without much test.

Signed-off-by: Tony Cheneau <tony.cheneau@amnesiak.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
index 6871ec1b30f8..416a54d31fb2 100644
--- a/net/ieee802154/6lowpan.c
+++ b/net/ieee802154/6lowpan.c
@@ -314,6 +314,9 @@ lowpan_uncompress_udp_header(struct sk_buff *skb)
 	struct udphdr *uh = udp_hdr(skb);
 	u8 tmp;
 
+	if (!uh)
+		goto err;
+
 	if (lowpan_fetch_skb_u8(skb, &tmp))
 		goto err;