[patch 22/73] ATM: Check IP header validity in mpc_send_packet

[Greg KH]

2.6.23-stable review patch.  If anyone has any objections, please let us know.
------------------
From: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>

[ATM]: Check IP header validity in mpc_send_packet

[ Upstream commit: 1c9b7aa1eb40ab708ef3242f74b9a61487623168 ]

Al went through the ip_fast_csum callers and found this piece of code
that did not validate the IP header.  While root crashing the machine
by sending bogus packets through raw or AF_PACKET sockets isn't that
serious, it is still nice to react gracefully.

This patch ensures that the skb has enough data for an IP header and
that the header length field is valid.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 net/atm/mpc.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/net/atm/mpc.c
+++ b/net/atm/mpc.c
@@ -542,6 +542,13 @@ static int mpc_send_packet(struct sk_buf
 	if (eth->h_proto != htons(ETH_P_IP))
 		goto non_ip; /* Multi-Protocol Over ATM :-) */
 
+	/* Weed out funny packets (e.g., AF_PACKET or raw). */
+	if (skb->len < ETH_HLEN + sizeof(struct iphdr))
+		goto non_ip;
+	skb_set_network_header(skb, ETH_HLEN);
+	if (skb->len < ETH_HLEN + ip_hdr(skb)->ihl * 4 || ip_hdr(skb)->ihl < 5)
+		goto non_ip;
+
 	while (i < mpc->number_of_mps_macs) {
 		if (!compare_ether_addr(eth->h_dest, (mpc->mps_macs + i*ETH_ALEN)))
 			if ( send_via_shortcut(skb, mpc) == 0 )           /* try shortcut */

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