Patch "sctp: make sure stream nums can match optlen in sctp_setsockopt_reset_streams" has been added to the 4.14-stable tree

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

sctp: make sure stream nums can match optlen in sctp_setsockopt_reset_streams

to the 4.14-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:
sctp-make-sure-stream-nums-can-match-optlen-in-sctp_setsockopt_reset_streams.patch
and it can be found in the queue-4.14 subdirectory.

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

From: Xin Long <[email protected]>
Date: Sun, 10 Dec 2017 15:40:51 +0800
Subject: sctp: make sure stream nums can match optlen in sctp_setsockopt_reset_streams

From: Xin Long <[email protected]>

[ Upstream commit 2342b8d95bcae5946e1b9b8d58645f37500ef2e7 ]

Now in sctp_setsockopt_reset_streams, it only does the check optlen < sizeof(*params) for optlen. But it's not enough, as params->srs_number_streams should also match optlen.

If the streams in params->srs_stream_list are less than stream nums in params->srs_number_streams, later when dereferencing the stream list, it could cause a slab-out-of-bounds crash, as reported by syzbot.

This patch is to fix it by also checking the stream numbers in sctp_setsockopt_reset_streams to make sure at least it's not greater than the streams in the list.

---
 net/sctp/socket.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

@@ -3874,13 +3874,17 @@ static int sctp_setsockopt_reset_streams
 	struct sctp_association *asoc;
 	int retval = -EINVAL;
 
-	if (optlen < sizeof(struct sctp_reset_streams))
+	if (optlen < sizeof(*params))
 		return -EINVAL;
 
 	params = memdup_user(optval, optlen);
 	if (IS_ERR(params))
 		return PTR_ERR(params);
 
+	if (params->srs_number_streams * sizeof(__u16) >
+	    optlen - sizeof(*params))
+		goto out;
+
 	asoc = sctp_id2assoc(sk, params->srs_assoc_id);
 	if (!asoc)
 		goto out;

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

queue-4.14/sctp-make-sure-stream-nums-can-match-optlen-in-sctp_setsockopt_reset_streams.patch queue-4.14/ipv6-mcast-better-catch-silly-mtu-values.patch