1 files changed, 18 insertions, 8 deletions

diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 5c16591a128e..6f0e6343c15e 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -439,7 +439,7 @@ assemble_neg_contexts(struct smb2_negotiate_req *req)
 	build_encrypt_ctxt((struct smb2_encryption_neg_context *)pneg_ctxt);
 	req->NegotiateContextOffset = cpu_to_le32(OFFSET_OF_NEG_CONTEXT);
 	req->NegotiateContextCount = cpu_to_le16(2);
-	inc_rfc1001_len(req, 4 + sizeof(struct smb2_preauth_neg_context) + 2
+	inc_rfc1001_len(req, 4 + sizeof(struct smb2_preauth_neg_context)
 			+ sizeof(struct smb2_encryption_neg_context)); /* calculate hash */
 }
 #else
@@ -570,10 +570,11 @@ SMB2_negotiate(const unsigned int xid, struct cifs_ses *ses)
 			/* ops set to 3.0 by default for default so update */
 			ses->server->ops = &smb21_operations;
 		}
-	} else if (rsp->DialectRevision != ses->server->vals->protocol_id) {
+	} else if (le16_to_cpu(rsp->DialectRevision) !=
+				ses->server->vals->protocol_id) {
 		/* if requested single dialect ensure returned dialect matched */
 		cifs_dbg(VFS, "Illegal 0x%x dialect returned: not requested\n",
-			cpu_to_le16(rsp->DialectRevision));
+			le16_to_cpu(rsp->DialectRevision));
 		return -EIO;
 	}
 
@@ -655,15 +656,22 @@ int smb3_validate_negotiate(const unsigned int xid, struct cifs_tcon *tcon)
 
 	/*
 	 * validation ioctl must be signed, so no point sending this if we
-	 * can not sign it.  We could eventually change this to selectively
+	 * can not sign it (ie are not known user).  Even if signing is not
+	 * required (enabled but not negotiated), in those cases we selectively
 	 * sign just this, the first and only signed request on a connection.
-	 * This is good enough for now since a user who wants better security
-	 * would also enable signing on the mount. Having validation of
-	 * negotiate info for signed connections helps reduce attack vectors
+	 * Having validation of negotiate info  helps reduce attack vectors.
 	 */
-	if (tcon->ses->server->sign == false)
+	if (tcon->ses->session_flags & SMB2_SESSION_FLAG_IS_GUEST)
 		return 0; /* validation requires signing */
 
+	if (tcon->ses->user_name == NULL) {
+		cifs_dbg(FYI, "Can't validate negotiate: null user mount\n");
+		return 0; /* validation requires signing */
+	}
+
+	if (tcon->ses->session_flags & SMB2_SESSION_FLAG_IS_NULL)
+		cifs_dbg(VFS, "Unexpected null user (anonymous) auth flag sent by server\n");
+
 	vneg_inbuf.Capabilities =
 			cpu_to_le32(tcon->ses->server->vals->req_capabilities);
 	memcpy(vneg_inbuf.Guid, tcon->ses->server->client_guid,
@@ -1175,6 +1183,8 @@ SMB2_sess_setup(const unsigned int xid, struct cifs_ses *ses,
 	while (sess_data->func)
 		sess_data->func(sess_data);
 
+	if ((ses->session_flags & SMB2_SESSION_FLAG_IS_GUEST) && (ses->sign))
+		cifs_dbg(VFS, "signing requested but authenticated as guest\n");
 	rc = sess_data->result;
 out:
 	kfree(sess_data);