Patch "netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv" has been added to the 4.12-stable tree

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

netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv

to the 4.12-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:
netfilter-nfnetlink-improve-input-length-sanitization-in-nfnetlink_rcv.patch
and it can be found in the queue-4.12 subdirectory.

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

From: Mateusz Jurczyk <[email protected]>
Date: Wed, 7 Jun 2017 15:50:38 +0200
Subject: netfilter: nfnetlink: Improve input length sanitization in nfnetlink_rcv

From: Mateusz Jurczyk <[email protected]>

commit f55ce7b024090a51382ccab2730b96e2f7b4e9cf upstream.

Verify that the length of the socket buffer is sufficient to cover the nlmsghdr structure before accessing the nlh->nlmsg_len field for further input sanitization. If the client only supplies 1-3 bytes of data in sk_buff, then nlh->nlmsg_len remains partially uninitialized and contains leftover memory from the corresponding kernel allocation. Operating on such data may result in indeterminate evaluation of the nlmsg_len < NLMSG_HDRLEN expression.

The bug was discovered by a runtime instrumentation designed to detect use of uninitialized memory in the kernel. The patch prevents this and other similar tools (e.g. KMSAN) from flagging this behavior in the future.

---
 net/netfilter/nfnetlink.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

@@ -463,8 +463,7 @@ static void nfnetlink_rcv_skb_batch(stru
 	if (msglen > skb->len)
 		msglen = skb->len;
 
-	if (nlh->nlmsg_len < NLMSG_HDRLEN ||
-	    skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
+	if (skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
 		return;
 
 	err = nla_parse(cda, NFNL_BATCH_MAX, attr, attrlen, nfnl_batch_policy,

@@ -491,7 +490,8 @@ static void nfnetlink_rcv(struct sk_buff
 {
 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
 
-	if (nlh->nlmsg_len < NLMSG_HDRLEN ||
+	if (skb->len < NLMSG_HDRLEN ||
+	    nlh->nlmsg_len < NLMSG_HDRLEN ||
 	    skb->len < nlh->nlmsg_len)
 		return;
 

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

queue-4.12/netfilter-nfnetlink-improve-input-length-sanitization-in-nfnetlink_rcv.patch