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 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

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-4.4 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 10:14:57 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 @@ -332,16 +332,14 @@ 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-4.4/sctp-do-not-allow-the-v4-socket-to-bind-a-v4mapped-v6-address.patch queue-4.4/pppoe-take-needed_headroom-of-lower-device-into-account-on-xmit.patch queue-4.4/sctp-return-error-if-the-asoc-has-been-peeled-off-in-sctp_wait_for_sndbuf.patch