Patch "ipv6: dccp: fix out of bound access in dccp_v6_err()" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

ipv6: dccp: fix out of bound access in dccp_v6_err()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ipv6-dccp-fix-out-of-bound-access-in-dccp_v6_err.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Dumazet <[email protected]>
Date: Wed, 2 Nov 2016 20:30:48 -0700
Subject: ipv6: dccp: fix out of bound access in dccp_v6_err()

From: Eric Dumazet <[email protected]>

[ Upstream commit 1aa9d1a0e7eefcc61696e147d123453fc0016005 ]

dccp_v6_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 icmpv6_notify() are more than enough.

---
 net/dccp/ipv6.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

@@ -70,7 +70,7 @@ static void dccp_v6_err(struct sk_buff *
 			u8 type, u8 code, int offset, __be32 info)
 {
 	const struct ipv6hdr *hdr = (const struct ipv6hdr *)skb->data;
-	const struct dccp_hdr *dh = (struct dccp_hdr *)(skb->data + offset);
+	const struct dccp_hdr *dh;
 	struct dccp_sock *dp;
 	struct ipv6_pinfo *np;
 	struct sock *sk;

@@ -78,12 +78,13 @@ static void dccp_v6_err(struct sk_buff *
 	__u64 seq;
 	struct net *net = dev_net(skb->dev);
 
-	if (skb->len < offset + sizeof(*dh) ||
-	    skb->len < offset + __dccp_basic_hdr_len(dh)) {
-		ICMP6_INC_STATS_BH(net, __in6_dev_get(skb->dev),
-				   ICMP6_MIB_INERRORS);
-		return;
-	}
+	/* Only need dccph_dport & dccph_sport which are the first
+	 * 4 bytes in dccp header.
+	 * Our caller (icmpv6_notify()) 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 = __inet6_lookup_established(net, &dccp_hashinfo,
 					&hdr->daddr, dh->dccph_dport,

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/net-__skb_flow_dissect-must-cap-its-return-value.patch queue-4.4/tcp-take-care-of-truncations-done-by-sk_filter.patch queue-4.4/net-clear-sk_err_soft-in-sk_clone_lock.patch queue-4.4/net-mangle-zero-checksum-in-skb_checksum_help.patch queue-4.4/ipv6-dccp-fix-out-of-bound-access-in-dccp_v6_err.patch queue-4.4/ipv6-dccp-add-missing-bind_conflict-to-dccp_ipv6_mapped.patch queue-4.4/tcp-fix-potential-memory-corruption.patch queue-4.4/dccp-do-not-send-reset-to-already-closed-sockets.patch queue-4.4/dccp-fix-out-of-bound-access-in-dccp_v4_err.patch queue-4.4/sock-fix-sendmmsg-for-partial-sendmsg.patch