Re: [Qemu-devel] qcow2 not cleaning up during image create failure

[Fam Zheng]

On Fri, 07/14 12:00, Daniel P. Berrange wrote:
> I've just been looking at the qcow2 image creation code, and found that
> if any method in qcow2_create2() returns an error, then we'll report that,
> but leave the newly created image file on disk in some partially initialized
> state. A user may unwittingly use this file later with undefined behaviour.
> This is particularly bad if we fail to setup encryption, because the user
> is left with a file with no encryption enabled.
> 
> So I'm wondering how is the best way to clean up after failure ?
> 
> Naively I would like to just unlink(filename), but IIUC, filename is
> not guaranteed to refer to a local file, and AFAIK, there is not
> bdrv_delete() method todo this portably.
> 
> If we can't delete a file (because its a block device or network
> volume), then we must at least blank out the just-written qcow2
> header with zeros.
> 
> Ideas / suggestions.

Or just write the header as the last step?

Fam