[NETFILTER]: ipt_REJECT: fix memory corruption

On devices with hard_header_len > LL_MAX_HEADER ip_route_me_harder() reallocates the skb, leading to memory corruption when using the stale tcph pointer to update the checksum. Signed-off-by: Patrick McHardy <[email protected]> Signed-off-by: David S. Miller <[email protected]>
neviim · Nov 29, 2006 · af443b6 · af443b6
1 parent 2e47c26
commit af443b6
Showing 1 changed file with 9 additions and 7 deletions.
diff --git a/net/ipv4/netfilter/ipt_REJECT.c b/net/ipv4/netfilter/ipt_REJECT.c
@@ -114,6 +114,14 @@ static void send_reset(struct sk_buff *oldskb, int hook)
 	tcph->window = 0;
 	tcph->urg_ptr = 0;
 
+	/* Adjust TCP checksum */
+	tcph->check = 0;
+	tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr),
+				   nskb->nh.iph->saddr,
+				   nskb->nh.iph->daddr,
+				   csum_partial((char *)tcph,
+						sizeof(struct tcphdr), 0));
+
 	/* Set DF, id = 0 */
 	nskb->nh.iph->frag_off = htons(IP_DF);
 	nskb->nh.iph->id = 0;
@@ -129,14 +137,8 @@ static void send_reset(struct sk_buff *oldskb, int hook)
 	if (ip_route_me_harder(&nskb, addr_type))
 		goto free_nskb;
 
-	/* Adjust TCP checksum */
 	nskb->ip_summed = CHECKSUM_NONE;
-	tcph->check = 0;
-	tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr),
-				   nskb->nh.iph->saddr,
-				   nskb->nh.iph->daddr,
-				   csum_partial((char *)tcph,
-						sizeof(struct tcphdr), 0));
+
 	/* Adjust IP TTL */
 	nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);