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

[<gregkh@linuxfoundation.org>]

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 <stable@vger.kernel.org> know about it.


>From foo@baz Thu Jun 29 18:57:46 CEST 2017
From: Mateusz Jurczyk <mjurczyk@google.com>
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 <mjurczyk@google.com>


[ 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.

Signed-off-by: Mateusz Jurczyk <mjurczyk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/decnet/netfilter/dn_rtmsg.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/net/decnet/netfilter/dn_rtmsg.c
+++ b/net/decnet/netfilter/dn_rtmsg.c
@@ -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 mjurczyk@google.com 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