netdev - [PATCH net] sctp: handle two v4 addrs comparison in sctp_inet6_cmp

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Date:   Thu, 26 Apr 2018 14:13:57 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     network dev <netdev@...r.kernel.org>, linux-sctp@...r.kernel.org
Cc:     davem@...emloft.net,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Neil Horman <nhorman@...driver.com>, syzkaller@...glegroups.com
Subject: [PATCH net] sctp: handle two v4 addrs comparison in sctp_inet6_cmp_addr

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@...kaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/sctp/ipv6.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/net/sctp/ipv6.c b/net/sctp/ipv6.c
index 2e3f7b7..4224711 100644
--- a/net/sctp/ipv6.c
+++ b/net/sctp/ipv6.c
@@ -895,6 +895,9 @@ 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);
 }

-- 
2.1.0