linux-kernel - Re: Avoid speculative indirect calls in kernel

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Date:   Thu, 4 Jan 2018 01:12:49 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <andi@...stfloor.org>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        dwmw@...zon.co.uk, Tim Chen <tim.c.chen@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dave Hansen <dave.hansen@...el.com>
Subject: Re: Avoid speculative indirect calls in kernel

On Wed, 3 Jan 2018, Andi Kleen wrote:
> On Wed, Jan 03, 2018 at 03:51:35PM -0800, Linus Torvalds wrote:
> > On Wed, Jan 3, 2018 at 3:09 PM, Andi Kleen <andi@...stfloor.org> wrote:
> > > This is a fix for Variant 2 in
> > > https://googleprojectzero.blogspot.com/2018/01/reading-privileged-memory-with-side.html
> > >
> > > Any speculative indirect calls in the kernel can be tricked
> > > to execute any kernel code, which may allow side channel
> > > attacks that can leak arbitrary kernel data.
> > 
> > Why is this all done without any configuration options?
> 
> I was thinking of a config option, but I was struggling with a name.
> 
> CONFIG_INSECURE_KERNEL, CONFIG_LEAK_MEMORY?
> 
> And should it be positive or negative?

It should be a CPU_BUG bit as we have for the other mess. And that can be
used for patching.

Thanks,

	tglx