Re: [PATCH v2] Linux Patch 1/1

[Thomas Gleixner <tglx@linutronix.de>]

On Fri, 27 Apr 2018, speck for Andi Kleen wrote:
> On Fri, Apr 27, 2018 at 07:48:03PM +0200, speck for Thomas Gleixner wrote:
> > On Fri, 27 Apr 2018, speck for Borislav Petkov wrote:
> > 
> > > On Fri, Apr 27, 2018 at 01:13:03PM -0400, speck for Jon Masters wrote:
> > > > My opinion is this needs to be a prctl that a vulnerable application can
> > > > set. It can be a one-way thing that's set/inherited by children, etc.
> > > 
> > > If the task does prctl, it *must* at least be a one-way thing because,
> > > as jikos said, if a malicious attacker can trick it into calling prctl()
> > > again to turn MD back on, the whole dance we're doing is useless.
> > 
> > That's not the worst problem. The worst thing is that it's inherited on
> > fork and then the child can disable it again nilly-willy, which makes no
> > sense whatsoever. If it's set only then the child CANNOT do that.
> 
> If the child can execute code it itself why shouldn't it be able
> to clear this bit? After all it can do everything else to itself too.

Sure. You set it on that sandbox thing and then the thread which is spawned
of from there can disable it. Brilliant idea.

Thanks,

	tglx