Tree connect for SMB3.1.1 must be signed for non-encrypted shares

SMB3.1.1 tree connect was only being signed when signing was mandatory
but needs to always be signed (for non-guest users).

See MS-SMB2 section 3.2.4.1.1
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
CC: Stable <stable@vger.kernel.org>

fs/cifs/smb2pdu.c

@@ -1305,6 +1305,11 @@ SMB2_tcon(const unsigned int xid, struct cifs_ses *ses, const char *tree,
 	iov[1].iov_base = unc_path;
 	iov[1].iov_len = unc_path_len;
 
+	/* 3.11 tcon req must be signed if not encrypted. See MS-SMB2 3.2.4.1.1 */
+	if ((ses->server->dialect == SMB311_PROT_ID) &&
+	    !encryption_required(tcon))
+		req->sync_hdr.Flags |= SMB2_FLAGS_SIGNED;
+
 	rc = smb2_send_recv(xid, ses, iov, 2, &resp_buftype, flags, &rsp_iov);
 	cifs_small_buf_release(req);
 	rsp = (struct smb2_tree_connect_rsp *)rsp_iov.iov_base;