X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=blobdiff_plain;f=net%2Fnetfilter%2Fxt_TCPMSS.c;h=07741640d9b68f393f0a8728dc8332e5d20adbfa;hp=9e63b43faeed030b5b51118f54722bc68cd2997d;hb=d84eeff84e9869d29f442ff652ce1352cfa63e84;hpb=7fcaa9aaea48996ba308c047a381de7a17ce03b2

diff --git a/net/netfilter/xt_TCPMSS.c b/net/netfilter/xt_TCPMSS.c
index 9e63b43faeed..07741640d9b6 100644
--- a/net/netfilter/xt_TCPMSS.c
+++ b/net/netfilter/xt_TCPMSS.c
@@ -44,25 +44,34 @@ optlen(const u_int8_t *opt, unsigned int offset)
 
 static int
 tcpmss_mangle_packet(struct sk_buff *skb,
-		     const struct xt_tcpmss_info *info,
+		     const struct xt_action_param *par,
 		     unsigned int in_mtu,
 		     unsigned int tcphoff,
 		     unsigned int minlen)
 {
+	const struct xt_tcpmss_info *info = par->targinfo;
 	struct tcphdr *tcph;
-	unsigned int tcplen, i;
+	int len, tcp_hdrlen;
+	unsigned int i;
 	__be16 oldval;
 	u16 newmss;
 	u8 *opt;
 
+	/* This is a fragment, no TCP header is available */
+	if (par->fragoff != 0)
+		return 0;
+
 	if (!skb_make_writable(skb, skb->len))
 		return -1;
 
-	tcplen = skb->len - tcphoff;
+	len = skb->len - tcphoff;
+	if (len < (int)sizeof(struct tcphdr))
+		return -1;
+
 	tcph = (struct tcphdr *)(skb_network_header(skb) + tcphoff);
+	tcp_hdrlen = tcph->doff * 4;
 
-	/* Header cannot be larger than the packet */
-	if (tcplen < tcph->doff*4)
+	if (len < tcp_hdrlen || tcp_hdrlen < sizeof(struct tcphdr))
 		return -1;
 
 	if (info->mss == XT_TCPMSS_CLAMP_PMTU) {
@@ -83,9 +92,8 @@ tcpmss_mangle_packet(struct sk_buff *skb,
 		newmss = info->mss;
 
 	opt = (u_int8_t *)tcph;
-	for (i = sizeof(struct tcphdr); i < tcph->doff*4; i += optlen(opt, i)) {
-		if (opt[i] == TCPOPT_MSS && tcph->doff*4 - i >= TCPOLEN_MSS &&
-		    opt[i+1] == TCPOLEN_MSS) {
+	for (i = sizeof(struct tcphdr); i <= tcp_hdrlen - TCPOLEN_MSS; i += optlen(opt, i)) {
+		if (opt[i] == TCPOPT_MSS && opt[i+1] == TCPOLEN_MSS) {
 			u_int16_t oldmss;
 
 			oldmss = (opt[i+2] << 8) | opt[i+3];
@@ -108,9 +116,14 @@ 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)
+	 * without moving it, and doing so may make the SYN packet
+	 * itself too large. Accept the packet unmodified instead.
+	 */
+	if (len > tcp_hdrlen)
+		return 0;
+
+	/* tcph->doff has 4 bits, do not wrap it to 0 */
+	if (tcp_hdrlen >= 15 * 4)
 		return 0;
 
 	/*
@@ -127,10 +140,10 @@ tcpmss_mangle_packet(struct sk_buff *skb,
 	skb_put(skb, TCPOLEN_MSS);
 
 	opt = (u_int8_t *)tcph + sizeof(struct tcphdr);
-	memmove(opt + TCPOLEN_MSS, opt, tcplen - sizeof(struct tcphdr));
+	memmove(opt + TCPOLEN_MSS, opt, len - sizeof(struct tcphdr));
 
 	inet_proto_csum_replace2(&tcph->check, skb,
-				 htons(tcplen), htons(tcplen + TCPOLEN_MSS), 1);
+				 htons(len), htons(len + TCPOLEN_MSS), 1);
 	opt[0] = TCPOPT_MSS;
 	opt[1] = TCPOLEN_MSS;
 	opt[2] = (newmss & 0xff00) >> 8;
@@ -183,7 +196,7 @@ tcpmss_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 	__be16 newlen;
 	int ret;
 
-	ret = tcpmss_mangle_packet(skb, par->targinfo,
+	ret = tcpmss_mangle_packet(skb, par,
 				   tcpmss_reverse_mtu(skb, PF_INET),
 				   iph->ihl * 4,
 				   sizeof(*iph) + sizeof(struct tcphdr));
@@ -211,7 +224,7 @@ tcpmss_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 	tcphoff = ipv6_skip_exthdr(skb, sizeof(*ipv6h), &nexthdr);
 	if (tcphoff < 0)
 		return NF_DROP;
-	ret = tcpmss_mangle_packet(skb, par->targinfo,
+	ret = tcpmss_mangle_packet(skb, par,
 				   tcpmss_reverse_mtu(skb, PF_INET6),
 				   tcphoff,
 				   sizeof(*ipv6h) + sizeof(struct tcphdr));