Subject: [PATCH 27/55] sctp: handle two v4 addrs comparison in sctp_inet6_cmp_addr

From: Xin Long <[email-masked]>
Date: Thu, 26 Apr 2018 14:13:57 +0800

[ Upstream commit d625329b06e46bd20baf9ee40847d11982569204 ]

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: [email-masked]
Signed-off-by: Xin Long <[email-masked]>
Acked-by: Neil Horman <[email-masked]>
Acked-by: Marcelo Ricardo Leitner <[email-masked]>
Signed-off-by: David S. Miller <[email-masked]>
---
 net/sctp/ipv6.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index 07b64719d1bc..351e80c59211 100644
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -866,6 +866,9 @@ static int sctp_inet6_cmp_addr(const union sctp_addr *addr1,
 	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);
 }
 
-- 
2.14.3