Contrary to what is written in the comment, a buggy guest can misconfigure
the transport buffers and pdu_marshal() may return an error. If this ever
happens, it is up to the transport layer to handle the situation (9P is
transport agnostic).
This fixes Coverity issue CID1348518.
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>