selinux: add AF_UNSPEC and INADDR_ANY checks to selinux_socket_bind()

Commit d452930f ("selinux: Add SCTP support") breaks compatibility
with the old programs that can pass sockaddr_in structure with AF_UNSPEC
and INADDR_ANY to bind(). As a result, bind() returns EAFNOSUPPORT error.
This was found with LTP/asapi_01 test.

Similar to commit 29c486df ("net: ipv4: relax AF_INET check in
bind()"), which relaxed AF_INET check for compatibility, add AF_UNSPEC
case to AF_INET and make sure that the address is INADDR_ANY.

Fixes: d452930f ("selinux: Add SCTP support")
Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/hooks.c

@@ -4568,6 +4568,7 @@ static int selinux_socket_post_create(struct socket *sock, int family,
 static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, int addrlen)
 {
 	struct sock *sk = sock->sk;
+	struct sk_security_struct *sksec = sk->sk_security;
 	u16 family;
 	int err;
 
@@ -4579,11 +4580,11 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in
 	family = sk->sk_family;
 	if (family == PF_INET || family == PF_INET6) {
 		char *addrp;
-		struct sk_security_struct *sksec = sk->sk_security;
 		struct common_audit_data ad;
 		struct lsm_network_audit net = {0,};
 		struct sockaddr_in *addr4 = NULL;
 		struct sockaddr_in6 *addr6 = NULL;
+		u16 family_sa = address->sa_family;
 		unsigned short snum;
 		u32 sid, node_perm;
 
@@ -4593,11 +4594,20 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in
 		 * need to check address->sa_family as it is possible to have
 		 * sk->sk_family = PF_INET6 with addr->sa_family = AF_INET.
 		 */
-		switch (address->sa_family) {
+		switch (family_sa) {
+		case AF_UNSPEC:
 		case AF_INET:
 			if (addrlen < sizeof(struct sockaddr_in))
 				return -EINVAL;
 			addr4 = (struct sockaddr_in *)address;
+			if (family_sa == AF_UNSPEC) {
+				/* see __inet_bind(), we only want to allow
+				 * AF_UNSPEC if the address is INADDR_ANY
+				 */
+				if (addr4->sin_addr.s_addr != htonl(INADDR_ANY))
+					goto err_af;
+				family_sa = AF_INET;
+			}
 			snum = ntohs(addr4->sin_port);
 			addrp = (char *)&addr4->sin_addr.s_addr;
 			break;
@@ -4609,13 +4619,7 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in
 			addrp = (char *)&addr6->sin6_addr.s6_addr;
 			break;
 		default:
-			/* Note that SCTP services expect -EINVAL, whereas
-			 * others expect -EAFNOSUPPORT.
-			 */
-			if (sksec->sclass == SECCLASS_SCTP_SOCKET)
-				return -EINVAL;
-			else
-				return -EAFNOSUPPORT;
+			goto err_af;
 		}
 
 		if (snum) {
@@ -4673,7 +4677,7 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in
 		ad.u.net->sport = htons(snum);
 		ad.u.net->family = family;
 
-		if (address->sa_family == AF_INET)
+		if (family_sa == AF_INET)
 			ad.u.net->v4info.saddr = addr4->sin_addr.s_addr;
 		else
 			ad.u.net->v6info.saddr = addr6->sin6_addr;
@@ -4686,6 +4690,11 @@ static int selinux_socket_bind(struct socket *sock, struct sockaddr *address, in
 	}
 out:
 	return err;
+err_af:
+	/* Note that SCTP services expect -EINVAL, others -EAFNOSUPPORT. */
+	if (sksec->sclass == SECCLASS_SCTP_SOCKET)
+		return -EINVAL;
+	return -EAFNOSUPPORT;
 }
 
 /* This supports connect(2) and SCTP connect services such as sctp_connectx(3)