Re: [Qemu-devel] [RFC PATCH-for-4.2] tracing: Allow to tune tracing options via the environment

["Daniel P. Berrangé" <berrange@redhat.com>]

On Sat, Jul 06, 2019 at 06:02:18AM +0200, Markus Armbruster wrote:
> Philippe Mathieu-Daudé <philmd@redhat.com> writes:
> 
> > On 7/5/19 3:19 PM, Markus Armbruster wrote:
> >> Philippe Mathieu-Daudé <philmd@redhat.com> writes:
> >>> On 7/5/19 10:07 AM, Stefan Hajnoczi wrote:
> >>>> On Thu, Jul 04, 2019 at 11:28:37AM +0100, Daniel P. Berrangé wrote:
> >>>>> On Thu, Jul 04, 2019 at 11:24:57AM +0100, Stefan Hajnoczi wrote:
> [...]
> >>>>>> What is the concern about adding these environment variables to QEMU?
> >>>>>>
> >>>>>> It is convenient to be able to use tracing even if QEMU is invoked by
> >>>>>> something you cannot modify/control.
> >>>>>>
> >>>>>> The main issues I see with environment variables are:
> >>>>>>
> >>>>>> 1. Security.  Is there a scenario where an attacker can use environment
> >>>>>>    variables to influence the behavior of a QEMU process running at a
> >>>>>>    different trust level?
> >> 
> >> The common (and sad) solution for this is to require whatever runs $PROG
> >> at a different trust level to scrub the environment.
> >
> > I hope people concerned by security build QEMU with the NOP trace backend.
> 
> I sure hope at least one of our tracing backends (other than nop) can be
> used safely in production.

AFAIK, *all* of the trace backends are safe for use in production. The
only questions are around performance in production.  If anyone knows of
any security problems with specific backends we should either address them,
or document the backend is unsafe.

Regards,
Daniel
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