Re: [Qemu-devel] [PATCH 4/4][RFC] Add logic to QEMU to read command line options from qcow2 images

[Philip Boulain <prb@ecs.soton.ac.uk>]

Yikes. I like the intent, but the idea of a previously just-data file format 
suddenly being able to imply "-hdb fat:rw:/home/" does not strike me as a good 
one. :/

andrzej zaborowski wrote:
> Yes, the file format starting with "#! /path/to/qemu" is a much better
> idea...

That should probably be "#!/usr/bin/env qemu", or something similar, if the 
intent is that "self-executing" image files are mostly zero-effort portable 
across (UNIX-y) host environments.

Anthony Liguori wrote:
> The disk image is directly executable and it makes it very clear to the user that they have to trust the disk image.

Only if qemu only read the embedded arguments in the case where it was executed 
as a script interpreter for the image, and/or only if the image's execute bit 
is set. In other words, this should prevent embedded arguments from being used:

   $ chmod -x dubious-image.qcow2
   $ qemu -hda dubious-image.qcow2

This also doesn't apply outside of UNIX-like environments, e.g. Windows; if 
someone had told Explorer to launch image files as "qemu.exe -hda (image)" 
(which is as close to shebanging a data file as you can really get), this could 
really be a nasty surprise.

LionsPhil