Commit c5006b8a authored Jan 15, 2018 by Xin Long Committed by David S. Miller Jan 16, 2018

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



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: 7dab83de ("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>

parent a0ff6600

net/sctp/socket.c

+6 −8

Original line number	Diff line number	Diff line
		@@ -335,16 +335,14 @@ static struct sctp_af sctp_sockaddr_af(struct sctp_sock opt,
		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))
		ipv6_addr_v4mapped(&addr->v6.sin6_addr) &&
		!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;
		}

		/* If we get this far, af is valid. */
		af = sctp_get_af_specific(addr->sa.sa_family);

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