From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Tue, 21 Aug 2007 07:06:37 +0000 (-0700)
Subject: [SNAP]: Check packet length before reading
X-Git-Tag: v2.6.23-rc4~92^2~4
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d92a7db710c32db826a00ba9bc7a22e741d5041e;p=linux-2.6

[SNAP]: Check packet length before reading

The snap_rcv code reads 5 bytes so we should make sure that
we have 5 bytes in the head before proceeding.

Based on diagnosis and fix by Evgeniy Polyakov, reported by
Alan J. Wylie.

Patch also kills the skb->sk assignment before kfree_skb
since it's redundant.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/net/802/psnap.c b/net/802/psnap.c
index 04ee43e753..31128cb92a 100644
--- a/net/802/psnap.c
+++ b/net/802/psnap.c
@@ -55,6 +55,9 @@ static int snap_rcv(struct sk_buff *skb, struct net_device *dev,
 		.type = __constant_htons(ETH_P_SNAP),
 	};
 
+	if (unlikely(!pskb_may_pull(skb, 5)))
+		goto drop;
+
 	rcu_read_lock();
 	proto = find_snap_client(skb_transport_header(skb));
 	if (proto) {
@@ -62,14 +65,18 @@ static int snap_rcv(struct sk_buff *skb, struct net_device *dev,
 		skb->transport_header += 5;
 		skb_pull_rcsum(skb, 5);
 		rc = proto->rcvfunc(skb, dev, &snap_packet_type, orig_dev);
-	} else {
-		skb->sk = NULL;
-		kfree_skb(skb);
-		rc = 1;
 	}
-
 	rcu_read_unlock();
+
+	if (unlikely(!proto))
+		goto drop;
+
+out:
 	return rc;
+
+drop:
+	kfree_skb(skb);
+	goto out;
 }
 
 /*