sctp: do not check port in sctp_inet6_cmp_addr

pf->cmp_addr() is called before binding a v6 address to the sock. It
should not check ports, like in sctp_inet_cmp_addr.

But sctp_inet6_cmp_addr checks the addr by invoking af(6)->cmp_addr,
sctp_v6_cmp_addr where it also compares the ports.

This would cause that setsockopt(SCTP_SOCKOPT_BINDX_ADD) could bind
multiple duplicated IPv6 addresses after Commit 40b4f0fd ("sctp:
lack the check for ports in sctp_v6_cmp_addr").

This patch is to remove af->cmp_addr called in sctp_inet6_cmp_addr,
but do the proper check for both v6 addrs and v4mapped addrs.

v1->v2:
  - define __sctp_v6_cmp_addr to do the common address comparison
    used for both pf and af v6 cmp_addr.

Fixes: 40b4f0fd ("sctp: lack the check for ports in sctp_v6_cmp_addr")
Reported-by: Jianwen Ji <jiji@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/ipv6.c

@@ -556,46 +556,49 @@ static void sctp_v6_to_addr(union sctp_addr *addr, struct in6_addr *saddr,
 	addr->v6.sin6_scope_id = 0;
 }
 
-/* Compare addresses exactly.
- * v4-mapped-v6 is also in consideration.
- */
-static int sctp_v6_cmp_addr(const union sctp_addr *addr1,
-			    const union sctp_addr *addr2)
+static int __sctp_v6_cmp_addr(const union sctp_addr *addr1,
+			      const union sctp_addr *addr2)
 {
 	if (addr1->sa.sa_family != addr2->sa.sa_family) {
 		if (addr1->sa.sa_family == AF_INET &&
 		    addr2->sa.sa_family == AF_INET6 &&
-		    ipv6_addr_v4mapped(&addr2->v6.sin6_addr)) {
-			if (addr2->v6.sin6_port == addr1->v4.sin_port &&
-			    addr2->v6.sin6_addr.s6_addr32[3] ==
-			    addr1->v4.sin_addr.s_addr)
-				return 1;
-		}
+		    ipv6_addr_v4mapped(&addr2->v6.sin6_addr) &&
+		    addr2->v6.sin6_addr.s6_addr32[3] ==
+		    addr1->v4.sin_addr.s_addr)
+			return 1;
+
 		if (addr2->sa.sa_family == AF_INET &&
 		    addr1->sa.sa_family == AF_INET6 &&
-		    ipv6_addr_v4mapped(&addr1->v6.sin6_addr)) {
-			if (addr1->v6.sin6_port == addr2->v4.sin_port &&
-			    addr1->v6.sin6_addr.s6_addr32[3] ==
-			    addr2->v4.sin_addr.s_addr)
-				return 1;
-		}
+		    ipv6_addr_v4mapped(&addr1->v6.sin6_addr) &&
+		    addr1->v6.sin6_addr.s6_addr32[3] ==
+		    addr2->v4.sin_addr.s_addr)
+			return 1;
+
 		return 0;
 	}
-	if (addr1->v6.sin6_port != addr2->v6.sin6_port)
-		return 0;
+
 	if (!ipv6_addr_equal(&addr1->v6.sin6_addr, &addr2->v6.sin6_addr))
 		return 0;
+
 	/* If this is a linklocal address, compare the scope_id. */
-	if (ipv6_addr_type(&addr1->v6.sin6_addr) & IPV6_ADDR_LINKLOCAL) {
-		if (addr1->v6.sin6_scope_id && addr2->v6.sin6_scope_id &&
-		    (addr1->v6.sin6_scope_id != addr2->v6.sin6_scope_id)) {
-			return 0;
-		}
-	}
+	if ((ipv6_addr_type(&addr1->v6.sin6_addr) & IPV6_ADDR_LINKLOCAL) &&
+	    addr1->v6.sin6_scope_id && addr2->v6.sin6_scope_id &&
+	    addr1->v6.sin6_scope_id != addr2->v6.sin6_scope_id)
+		return 0;
 
 	return 1;
 }
 
+/* Compare addresses exactly.
+ * v4-mapped-v6 is also in consideration.
+ */
+static int sctp_v6_cmp_addr(const union sctp_addr *addr1,
+			    const union sctp_addr *addr2)
+{
+	return __sctp_v6_cmp_addr(addr1, addr2) &&
+	       addr1->v6.sin6_port == addr2->v6.sin6_port;
+}
+
 /* Initialize addr struct to INADDR_ANY. */
 static void sctp_v6_inaddr_any(union sctp_addr *addr, __be16 port)
 {
@@ -875,8 +878,8 @@ static int sctp_inet6_cmp_addr(const union sctp_addr *addr1,
 			       const union sctp_addr *addr2,
 			       struct sctp_sock *opt)
 {
-	struct sctp_af *af1, *af2;
 	struct sock *sk = sctp_opt2sk(opt);
+	struct sctp_af *af1, *af2;
 
 	af1 = sctp_get_af_specific(addr1->sa.sa_family);
 	af2 = sctp_get_af_specific(addr2->sa.sa_family);
@@ -892,10 +895,7 @@ 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 != addr2->sa.sa_family)
-		return 0;
-
-	return af1->cmp_addr(addr1, addr2);
+	return __sctp_v6_cmp_addr(addr1, addr2);
 }
 
 /* Verify that the provided sockaddr looks bindable.   Common verification,