linux-kernel - Re: [PATCH] [RFC] x86: work around MPX Erratum

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Message-ID: <CA+55aFxnAkGXdxrSJn-=HAS6zhXd08rTyk_JpvAXtQfjQcbFgw@mail.gmail.com>
Date:	Tue, 3 May 2016 14:39:38 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>
Subject: Re: [PATCH] [RFC] x86: work around MPX Erratum

On Tue, May 3, 2016 at 2:31 PM, Andy Lutomirski <luto@...capital.net> wrote:
>
> Having actually read the erratum: how can this affect Linux at all
> under any scenario where user code hasn't already completely
> compromised the kernel?

If it matches purely on linear address, you will potentially have
interesting situations with people running in virtualized environments
and crashing programs in other virtual containers or the host.

I do agree that we likely don't care all that much (especially with
the lack of users in the first place).  But considering that the
trivial workaround is to make sure SMEP is enabled - which we want to
heavily encourage anyway - I also don't think there's any real
downside to just enforcing that workaround.

              Linus