Revert "SELinux: use SECINITSID_NETMSG instead of SECINITSID_UNLABELED for NetLabel"

This reverts commit 9faf65fb.

It bit people like Michal Piotrowski:

  "My system is too secure, I can not login :)"

because it changed how CONFIG_NETLABEL worked, and broke older SElinux
policies.

As a result, quoth James Morris:

  "Can you please revert this patch?

   We thought it only affected people running MLS, but it will affect others.

   Sorry for the hassle."

Cc: James Morris <jmorris@namei.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Cc: Paul Moore <paul.moore@hp.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

security/selinux/hooks.c

@@ -3129,19 +3129,17 @@ static int selinux_parse_skb(struct sk_buff *skb, struct avc_audit_data *ad,
 /**
  * selinux_skb_extlbl_sid - Determine the external label of a packet
  * @skb: the packet
+ * @base_sid: the SELinux SID to use as a context for MLS only external labels
  * @sid: the packet's SID
  *
  * Description:
  * Check the various different forms of external packet labeling and determine
- * the external SID for the packet.  If only one form of external labeling is
- * present then it is used, if both labeled IPsec and NetLabel labels are
- * present then the SELinux type information is taken from the labeled IPsec
- * SA and the MLS sensitivity label information is taken from the NetLabel
- * security attributes.  This bit of "magic" is done in the call to
- * selinux_netlbl_skbuff_getsid().
+ * the external SID for the packet.
  *
  */
-static void selinux_skb_extlbl_sid(struct sk_buff *skb, u32 *sid)
+static void selinux_skb_extlbl_sid(struct sk_buff *skb,
+				   u32 base_sid,
+				   u32 *sid)
 {
 	u32 xfrm_sid;
 	u32 nlbl_sid;
@@ -3149,9 +3147,10 @@ static void selinux_skb_extlbl_sid(struct sk_buff *skb, u32 *sid)
 	selinux_skb_xfrm_sid(skb, &xfrm_sid);
 	if (selinux_netlbl_skbuff_getsid(skb,
 					 (xfrm_sid == SECSID_NULL ?
-					  SECINITSID_NETMSG : xfrm_sid),
+					  base_sid : xfrm_sid),
 					 &nlbl_sid) != 0)
 		nlbl_sid = SECSID_NULL;
+
 	*sid = (nlbl_sid == SECSID_NULL ? xfrm_sid : nlbl_sid);
 }
 
@@ -3696,7 +3695,7 @@ static int selinux_socket_getpeersec_dgram(struct socket *sock, struct sk_buff *
 	if (sock && sock->sk->sk_family == PF_UNIX)
 		selinux_get_inode_sid(SOCK_INODE(sock), &peer_secid);
 	else if (skb)
-		selinux_skb_extlbl_sid(skb, &peer_secid);
+		selinux_skb_extlbl_sid(skb, SECINITSID_UNLABELED, &peer_secid);
 
 	if (peer_secid == SECSID_NULL)
 		err = -EINVAL;
@@ -3757,7 +3756,7 @@ static int selinux_inet_conn_request(struct sock *sk, struct sk_buff *skb,
 	u32 newsid;
 	u32 peersid;
 
-	selinux_skb_extlbl_sid(skb, &peersid);
+	selinux_skb_extlbl_sid(skb, SECINITSID_UNLABELED, &peersid);
 	if (peersid == SECSID_NULL) {
 		req->secid = sksec->sid;
 		req->peer_secid = SECSID_NULL;
@@ -3795,7 +3794,7 @@ static void selinux_inet_conn_established(struct sock *sk,
 {
 	struct sk_security_struct *sksec = sk->sk_security;
 
-	selinux_skb_extlbl_sid(skb, &sksec->peer_sid);
+	selinux_skb_extlbl_sid(skb, SECINITSID_UNLABELED, &sksec->peer_sid);
 }
 
 static void selinux_req_classify_flow(const struct request_sock *req,

security/selinux/netlabel.c

@@ -158,7 +158,9 @@ int selinux_netlbl_skbuff_getsid(struct sk_buff *skb, u32 base_sid, u32 *sid)
 	netlbl_secattr_init(&secattr);
 	rc = netlbl_skbuff_getattr(skb, &secattr);
 	if (rc == 0 && secattr.flags != NETLBL_SECATTR_NONE)
-		rc = security_netlbl_secattr_to_sid(&secattr, base_sid, sid);
+		rc = security_netlbl_secattr_to_sid(&secattr,
+						    base_sid,
+						    sid);
 	else
 		*sid = SECSID_NULL;
 	netlbl_secattr_destroy(&secattr);
@@ -196,7 +198,7 @@ void selinux_netlbl_sock_graft(struct sock *sk, struct socket *sock)
 	if (netlbl_sock_getattr(sk, &secattr) == 0 &&
 	    secattr.flags != NETLBL_SECATTR_NONE &&
 	    security_netlbl_secattr_to_sid(&secattr,
-					   SECINITSID_NETMSG,
+					   SECINITSID_UNLABELED,
 					   &nlbl_peer_sid) == 0)
 		sksec->peer_sid = nlbl_peer_sid;
 	netlbl_secattr_destroy(&secattr);
@@ -293,32 +295,38 @@ int selinux_netlbl_sock_rcv_skb(struct sk_security_struct *sksec,
 				struct avc_audit_data *ad)
 {
 	int rc;
-	u32 nlbl_sid;
-	u32 perm;
+	u32 netlbl_sid;
+	u32 recv_perm;
 
-	rc = selinux_netlbl_skbuff_getsid(skb, SECINITSID_NETMSG, &nlbl_sid);
+	rc = selinux_netlbl_skbuff_getsid(skb,
+					  SECINITSID_UNLABELED,
+					  &netlbl_sid);
 	if (rc != 0)
 		return rc;
-	if (nlbl_sid == SECSID_NULL)
-		nlbl_sid = SECINITSID_UNLABELED;
+
+	if (netlbl_sid == SECSID_NULL)
+		return 0;
 
 	switch (sksec->sclass) {
 	case SECCLASS_UDP_SOCKET:
-		perm = UDP_SOCKET__RECVFROM;
+		recv_perm = UDP_SOCKET__RECVFROM;
 		break;
 	case SECCLASS_TCP_SOCKET:
-		perm = TCP_SOCKET__RECVFROM;
+		recv_perm = TCP_SOCKET__RECVFROM;
 		break;
 	default:
-		perm = RAWIP_SOCKET__RECVFROM;
+		recv_perm = RAWIP_SOCKET__RECVFROM;
 	}
 
-	rc = avc_has_perm(sksec->sid, nlbl_sid, sksec->sclass, perm, ad);
+	rc = avc_has_perm(sksec->sid,
+			  netlbl_sid,
+			  sksec->sclass,
+			  recv_perm,
+			  ad);
 	if (rc == 0)
 		return 0;
 
-	if (nlbl_sid != SECINITSID_UNLABELED)
-		netlbl_skbuff_err(skb, rc);
+	netlbl_skbuff_err(skb, rc);
 	return rc;
 }