linux-kernel - Re: [PATCH 05/11] x86/fpu: set PKRU state for kernel threads

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Date:   Thu, 18 Oct 2018 23:24:21 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Dave Hansen <dave.hansen@...ux.intel.com>
Cc:     Andy Lutomirski <luto@...capital.net>,
        Andrew Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        kvm list <kvm@...r.kernel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH 05/11] x86/fpu: set PKRU state for kernel threads

On 2018-10-18 13:56:24 [-0700], Dave Hansen wrote:
> > But this is not the only loophole: There is ptrace interface which is
> > used by gdb (just checked) and also bypasses PKRU. So…
> 
> Bypassing protection keys is not a big deal IMNHO.  In places where a
> sane one is not readily available, I'm totally fine with just
> effectively disabling it (PKRU=0) for the length of time it isn't available.

Okay, this makes things easier. Let document that for kernel threads we
use PKRU=0. This should be happening in my try right now. I double check
tomorrow just in case…

Sebastian