From: Xin Long <lucien.xin@gmail.com>
Date: Thu, 26 Apr 2018 14:13:57 +0800
Subject: sctp: handle two v4 addrs comparison in sctp_inet6_cmp_addr
Git-commit: d625329b06e46bd20baf9ee40847d11982569204
Patch-mainline: v4.17-rc4
References: git-fixes

Since sctp ipv6 socket also supports v4 addrs, it's possible to
compare two v4 addrs in pf v6 .cmp_addr, sctp_inet6_cmp_addr.

However after Commit 1071ec9d453a ("sctp: do not check port in
sctp_inet6_cmp_addr"), it no longer calls af1->cmp_addr, which
in this case is sctp_v4_cmp_addr, but calls __sctp_v6_cmp_addr
where it handles them as two v6 addrs. It would cause a out of
bounds crash.

syzbot found this crash when trying to bind two v4 addrs to a
v6 socket.

This patch fixes it by adding the process for two v4 addrs in
sctp_inet6_cmp_addr.

Fixes: 1071ec9d453a ("sctp: do not check port in sctp_inet6_cmp_addr")
Reported-by: syzbot+cd494c1dd681d4d93ebb@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 net/sctp/ipv6.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -863,6 +863,9 @@ static int sctp_inet6_cmp_addr(const uni
 	if (sctp_is_any(sk, addr1) || sctp_is_any(sk, addr2))
 		return 1;
 
+	if (addr1->sa.sa_family == AF_INET && addr2->sa.sa_family == AF_INET)
+		return addr1->v4.sin_addr.s_addr == addr2->v4.sin_addr.s_addr;
+
 	return __sctp_v6_cmp_addr(addr1, addr2);
 }