smb: server: stop sending fake security descriptors

in smb2_get_info_sec, a dummy security descriptor (SD) is returned if
the requested information is not supported.

the code is currently wrong, as DACL_PROTECTED is set in the type field,
but there is no DACL is present.

instead of faking a security, report a STATUS_NOT_SUPPORTED error.

this seems to fix a "Error 0x80090006: Invalid Signature" on file
transfers with Windows 11 clients (25H2, build 26200.8246).

capturing traffic shows that the client is sending a GET_INFO/SEC_INFO
request, with the additional_info field set to 0x20
(ATTRIBUTE_SECURITY_INFORMATION). Returning an empty SD
(with only SELF_RELATIVE set) does not fix the error.

Signed-off-by: Marios Makassikis <[email protected]>
Acked-by: Namjae Jeon <[email protected]>
Signed-off-by: Steve French <[email protected]>

Author: Marios Makassikis

fs/smb/server/smb2pdu.c

@@ -5746,20 +5746,8 @@ static int smb2_get_info_sec(struct ksmbd_work *work,
 		ksmbd_debug(SMB, "Unsupported addition info: 0x%x)\n",
 		       addition_info);
 
-		pntsd = kzalloc(ALIGN(sizeof(struct smb_ntsd), 8),
-				KSMBD_DEFAULT_GFP);
-		if (!pntsd)
-			return -ENOMEM;
-
-		pntsd->revision = cpu_to_le16(1);
-		pntsd->type = cpu_to_le16(SELF_RELATIVE | DACL_PROTECTED);
-		pntsd->osidoffset = 0;
-		pntsd->gsidoffset = 0;
-		pntsd->sacloffset = 0;
-		pntsd->dacloffset = 0;
-
-		secdesclen = sizeof(struct smb_ntsd);
-		goto iov_pin;
+		rsp->hdr.Status = STATUS_NOT_SUPPORTED;
+		return -EINVAL;
 	}
 
 	if (work->next_smb2_rcv_hdr_off) {
@@ -5826,7 +5814,6 @@ static int smb2_get_info_sec(struct ksmbd_work *work,
 	if (rc)
 		goto err_out;
 
-iov_pin:
 	rsp->OutputBufferLength = cpu_to_le32(secdesclen);
 	rc = buffer_check_err(le32_to_cpu(req->OutputBufferLength),
 			      rsp, work->response_buf);