Re: [Qemu-devel] [PATCH v2 2/3] qemu-img: Detect backing file chain infinite loops

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Oct 16, 2012 at 12:11:44PM +0200, Kevin Wolf wrote:
> Am 15.10.2012 14:44, schrieb Stefan Hajnoczi:
> > A malicious or corruption image can contain an infinite loop of backing
> > files.  The qemu-img info --backing-chain command must not hang when
> > such files are encountered.
> > 
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> 
> This seems to do what is intended, but I think rather than fixing the
> 'qemu-img info' special case I'd have fixed bdrv_open() to detect the
> situation.

When bdrv_open() on the chain fails we'll still need to iterate each
image (with infinite loop detection) in qemu-img info.  This allows
qemu-img info to print out details of the chain and where the chain goes
wrong.

> Do we need to properly communicate what the broken image is with JSON
> output? This patch will only produce broken JSON in the failure case.

Ah, you're right.  We must close the JSON array and add a test case for
this :(.

Will send v3.

Stefan