linux-kernel - Re: [RFC][PATCH 13/24] x86/pti: Extend PTI user mappings

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Message-ID: <CALCETrX-cN8zcSNZnmEw=0dL+mkaqkWVMdE2FkGTfUFR+Si=Bg@mail.gmail.com>
Date:   Mon, 9 Nov 2020 09:28:01 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Alexandre Chartre <alexandre.chartre@...cle.com>
Cc:     X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH 13/24] x86/pti: Extend PTI user mappings

On Mon, Nov 9, 2020 at 3:22 AM Alexandre Chartre
<alexandre.chartre@...cle.com> wrote:
>
> Extend PTI user mappings so that more kernel entry code can be executed
> with the user page-table. To do so, we need to map syscall and interrupt
> entry code,

Probably fine.

> per cpu offsets (__per_cpu_offset, which is used some in
> entry code),

This likely already leaks due to vulnerable CPUs leaking address space
layout info.

> the stack canary,

That's going to be a very tough sell.