mpls: In mpls_egress verify the packet length.
Reobert Shearman noticed that mpls_egress is failing to verify that
the bytes to be examined are in fact present in the packet before
mpls_egress reads those bytes.
As suggested by David Miller reduce this to a single pskb_may_pull
call so that we don't do unnecessary work in the fast path.
Reported-by: Robert Shearman <rshearma@brocade.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index 0ad8f7141..db8a2ea 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -92,9 +92,24 @@
* The strange cases if we choose to support them will require
* manual configuration.
*/
- struct iphdr *hdr4 = ip_hdr(skb);
+ struct iphdr *hdr4;
bool success = true;
+ /* The IPv4 code below accesses through the IPv4 header
+ * checksum, which is 12 bytes into the packet.
+ * The IPv6 code below accesses through the IPv6 hop limit
+ * which is 8 bytes into the packet.
+ *
+ * For all supported cases there should always be at least 12
+ * bytes of packet data present. The IPv4 header is 20 bytes
+ * without options and the IPv6 header is always 40 bytes
+ * long.
+ */
+ if (!pskb_may_pull(skb, 12))
+ return false;
+
+ /* Use ip_hdr to find the ip protocol version */
+ hdr4 = ip_hdr(skb);
if (hdr4->version == 4) {
skb->protocol = htons(ETH_P_IP);
csum_replace2(&hdr4->check,