Re: [Qemu-devel] [Bug 1626972] Re: [PATCH] util: secure memfd_create fallback mechanism

[Daniel P. Berrange]

On Tue, Sep 27, 2016 at 11:01:10AM -0000, Rafael David Tinoco wrote:
> > On Sep 27, 2016, at 05:36, Daniel P. Berrange <address@hidden> wrote:
> > 
> > On Tue, Sep 27, 2016 at 03:06:21AM +0000, Rafael David Tinoco wrote:
> >> Commit: 35f9b6ef3acc9d0546c395a566b04e63ca84e302 added a fallback
> >> mechanism for systems not supporting memfd_create syscall (started
> >> being supported since 3.17).
> > 
> > This is really dubious code in general and IMHO should just
> > be reverted.
> 
> There are numerous people relying on older kernels in openstack 
> deployments - sometimes with specific drivers (ovswitch, dpdk, 
> infiniband) holding kernel upgrades - but still in need of upgrading 
> userland (e.g. newer releases). Having a fallback mechanism seems 
> appropriate for those cases.

I'm not against some kind of fallback - just about the way it
silently creates files in /tmp.

> 
> Note that the filename, per se, is not as important as other files, 
> since qemu won't provide it for being accessed by external programs, and,
> deletes the file, while keeping the descriptor, right after its creation
> (due to its nature, that is probably why it was created in /tmp).

If it doesn't shared with other processes, and is deleted immediately,
why does the file need to be on disk at all ?


Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|