Re: FreeBSD Security Advisory FreeBSD-SA-19:23.midi

On Tue, Aug 20, 2019 at 04:01:39PM -0600, Ian Lepore wrote:
> On Wed, 2019-08-21 at 04:55 +0700, Eugene Grosbein wrote:
> > 21.08.2019 3:12, FreeBSD Security Advisories wrote:
> > 
> > [skip]
> > 
> > > IV.  Workaround
> > > 
> > > No workaround is available.  Custom kernels without "device sound"
> > > are not vulnerable.
> > 
> > Is it true that there is no way to disable vulnerable and unneeded
> > device driver
> > built in GENERIC other that through rebuilding the kernel?
> > 
> > I remember that pre-4.x versions of FreeBSD had visual VGA-based pre-
> > boot configurator
> > allowing to disable any compiled-in device driver. Don't
> > device.hints(5) or loader(8) have means to do so?
> > 
> > These days GENERIC have LOTS of drivers and it's convenient but
> > unsafe.
> > 
> 
> "No workaround" just seems to be wrong.  Aside from setting the
> disabled hint to turn off the driver (or using devctl to turn it off on
> a live system), the exploit also requires opening /dev/midistat, so a
> viable workaround is to change its permissions so that users can't open
> it.

Yeah, this was an oversight.  The SA text will be amended.
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