---

yaml
---
r: 184146
b: refs/heads/master
c: 10a1993
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c30f540b63047437ffa894b5353216410c480d1a
+refs/heads/master: 10a199394b8f9b4c4e0be6e14a61109a7d891b1b

trunk/net/netfilter/xt_TCPMSS.c

@@ -60,17 +60,9 @@ tcpmss_mangle_packet(struct sk_buff *skb,
 	tcplen = skb->len - tcphoff;
 	tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
 
-	/* Since it passed flags test in tcp match, we know it is is
-	   not a fragment, and has data >= tcp header length.  SYN
-	   packets should not contain data: if they did, then we risk
-	   running over MTU, sending Frag Needed and breaking things
-	   badly. --RR */
-	if (tcplen != tcph->doff*4) {
-		if (net_ratelimit())
-			printk(KERN_ERR "xt_TCPMSS: bad length (%u bytes)\n",
-			       skb->len);
+	/* Header cannot be larger than the packet */
+	if (tcplen < tcph->doff*4)
 		return -1;
-	}
 
 	if (info->mss == XT_TCPMSS_CLAMP_PMTU) {
 		if (dst_mtu(skb_dst(skb)) <= minlen) {
@@ -115,6 +107,12 @@ tcpmss_mangle_packet(struct sk_buff *skb,
 		}
 	}
 
+	/* There is data after the header so the option can't be added
+	   without moving it, and doing so may make the SYN packet
+	   itself too large. Accept the packet unmodified instead. */
+	if (tcplen > tcph->doff*4)
+		return 0;
+
 	/*
 	 * MSS Option not found ?! add it..
 	 */