dccp: fix out of bound access in dccp_v4_err() (6706a97f) · Commits · 戴 / test

dccp_v4_err() does not use pskb_may_pull() and might access garbage. We only need 4 bytes at the beginning of the DCCP header, like TCP, so the 8 bytes pulled in icmp_socket_deliver() are more than enough. This patch might allow to process more ICMP messages, as some routers are still limiting the size of reflected bytes to 28 (RFC 792), instead of extended lengths (RFC 1812 4.3.2.3) Signed-off-by:

Eric Dumazet <edumazet@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/dccp/ipv4.c

+8 −6

Original line number	Diff line number	Diff line
		@@ -235,7 +235,7 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
		{
		const struct iphdr iph = (struct iphdr )skb->data;
		const u8 offset = iph->ihl << 2;
		const struct dccp_hdr dh = (struct dccp_hdr )(skb->data + offset);
		const struct dccp_hdr *dh;
		struct dccp_sock *dp;
		struct inet_sock *inet;
		const int type = icmp_hdr(skb)->type;
		@@ -245,11 +245,13 @@ static void dccp_v4_err(struct sk_buff *skb, u32 info)
		int err;
		struct net *net = dev_net(skb->dev);

		if (skb->len < offset + sizeof(*dh) \|\|
		skb->len < offset + __dccp_basic_hdr_len(dh)) {
		__ICMP_INC_STATS(net, ICMP_MIB_INERRORS);
		return;
		}
		/* Only need dccph_dport & dccph_sport which are the first
		* 4 bytes in dccp header.
		* Our caller (icmp_socket_deliver()) already pulled 8 bytes for us.
		*/
		BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_sport) > 8);
		BUILD_BUG_ON(offsetofend(struct dccp_hdr, dccph_dport) > 8);
		dh = (struct dccp_hdr *)(skb->data + offset);

		sk = __inet_lookup_established(net, &dccp_hashinfo,
		iph->daddr, dh->dccph_dport,

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