Patch "sctp: do not allow the v4 socket to bind a v4mapped v6 address" has been added to the 3.18-stable tree

[<gregkh@linuxfoundation.org>]

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

    sctp: do not allow the v4 socket to bind a v4mapped v6 address

to the 3.18-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-do-not-allow-the-v4-socket-to-bind-a-v4mapped-v6-address.patch
and it can be found in the queue-3.18 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 Mon Jan 29 11:15:06 CET 2018
From: Xin Long <lucien.xin@gmail.com>
Date: Mon, 15 Jan 2018 17:02:00 +0800
Subject: sctp: do not allow the v4 socket to bind a v4mapped v6 address

From: Xin Long <lucien.xin@gmail.com>


[ Upstream commit c5006b8aa74599ce19104b31d322d2ea9ff887cc ]

The check in sctp_sockaddr_af is not robust enough to forbid binding a
v4mapped v6 addr on a v4 socket.

The worse thing is that v4 socket's bind_verify would not convert this
v4mapped v6 addr to a v4 addr. syzbot even reported a crash as the v4
socket bound a v6 addr.

This patch is to fix it by doing the common sa.sa_family check first,
then AF_INET check for v4mapped v6 addrs.

Fixes: 7dab83de50c7 ("sctp: Support ipv6only AF_INET6 sockets.")
Reported-by: syzbot+7b7b518b1228d2743963@syzkaller.appspotmail.com
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/sctp/socket.c |   14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -333,16 +333,14 @@ static struct sctp_af *sctp_sockaddr_af(
 	if (len < sizeof (struct sockaddr))
 		return NULL;
 
+	if (!opt->pf->af_supported(addr->sa.sa_family, opt))
+		return NULL;
+
 	/* V4 mapped address are really of AF_INET family */
 	if (addr->sa.sa_family == AF_INET6 &&
-	    ipv6_addr_v4mapped(&addr->v6.sin6_addr)) {
-		if (!opt->pf->af_supported(AF_INET, opt))
-			return NULL;
-	} else {
-		/* Does this PF support this AF? */
-		if (!opt->pf->af_supported(addr->sa.sa_family, opt))
-			return NULL;
-	}
+	    ipv6_addr_v4mapped(&addr->v6.sin6_addr) &&
+	    !opt->pf->af_supported(AF_INET, opt))
+		return NULL;
 
 	/* If we get this far, af is valid. */
 	af = sctp_get_af_specific(addr->sa.sa_family);


Patches currently in stable-queue which might be from lucien.xin@gmail.com are

queue-3.18/sctp-do-not-allow-the-v4-socket-to-bind-a-v4mapped-v6-address.patch
queue-3.18/pppoe-take-needed_headroom-of-lower-device-into-account-on-xmit.patch
queue-3.18/sctp-return-error-if-the-asoc-has-been-peeled-off-in-sctp_wait_for_sndbuf.patch