ksmbd: the buffer of smb2 query dir response has at least 1 byte

When STATUS_NO_MORE_FILES status is set to smb2 query dir response,
->StructureSize is set to 9, which mean buffer has 1 byte.
This issue occurs because ->Buffer[1] in smb2_query_directory_rsp to
flex-array.

Fixes: eb3e28c1e89b ("smb3: Replace smb2pdu 1-element arrays with flex-arrays")
Cc: [e-mail] # v6.1+
Signed-off-by: Namjae Jeon <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/smb/server/smb2pdu.c

···
 		rsp->OutputBufferLength = cpu_to_le32(0);
 		rsp->Buffer[0] = 0;
 		rc = ksmbd_iov_pin_rsp(work, (void *)rsp,
-				       sizeof(struct smb2_query_directory_rsp));
+				       offsetof(struct smb2_query_directory_rsp, Buffer)
+				       + 1);
 		if (rc)
 			goto err_out;
 	} else {