Patch "decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb" has been added to the 4.9-stable tree

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

decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb

to the 4.9-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:
decnet-dn_rtmsg-improve-input-length-sanitization-in-dnrmg_receive_user_skb.patch
and it can be found in the queue-4.9 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 16:14:29 +0200
Subject: decnet: dn_rtmsg: Improve input length sanitization in dnrmg_receive_user_skb

From: Mateusz Jurczyk <[email protected]>

[ Upstream commit dd0da17b209ed91f39872766634ca967c170ada1 ]

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 < sizeof(*nlh) 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/decnet/netfilter/dn_rtmsg.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

@@ -102,7 +102,9 @@ static inline void dnrmg_receive_user_sk
 {
 	struct nlmsghdr *nlh = nlmsg_hdr(skb);
 
-	if (nlh->nlmsg_len < sizeof(*nlh) || skb->len < nlh->nlmsg_len)
+	if (skb->len < sizeof(*nlh) ||
+	    nlh->nlmsg_len < sizeof(*nlh) ||
+	    skb->len < nlh->nlmsg_len)
 		return;
 
 	if (!netlink_capable(skb, CAP_NET_ADMIN))

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

queue-4.9/decnet-dn_rtmsg-improve-input-length-sanitization-in-dnrmg_receive_user_skb.patch queue-4.9/af_unix-add-sockaddr-length-checks-before-accessing-sa_family-in-bind-and-connect-handlers.patch