linux-kernel - Re: [PATCH] x86,seccomp,prctl: Remove PR_TSC

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Message-ID: <20141003211204.GQ10583@worktop.programming.kicks-ass.net>
Date:	Fri, 3 Oct 2014 23:12:04 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Kees Cook <keescook@...omium.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Erik Bosman <ebn310@....vu.nl>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linux API <linux-api@...r.kernel.org>,
	Michael Kerrisk-manpages <mtk.manpages@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	X86 ML <x86@...nel.org>
Subject: Re: [PATCH] x86,seccomp,prctl: Remove PR_TSC_SIGSEGV and seccomp TSC
 filtering

On Fri, Oct 03, 2014 at 02:04:53PM -0700, Andy Lutomirski wrote:
> On Fri, Oct 3, 2014 at 2:02 PM, Peter Zijlstra <peterz@...radead.org> wrote:

> > Something like so.. slightly less ugly and possibly with more
> > complicated conditions setting the cr4 if you want to fix tsc vs seccomp
> > as well.
> 
> This will crash anything that tries rdpmc in an allow-everything
> seccomp sandbox.  It's also not very compatible with my grand scheme
> of allowing rdtsc to be turned off without breaking clock_gettime. :)

Well, we clear cap_user_rdpmc, so everybody who still tries it gets what
he deserves, no problem there.
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