linux-kernel - Re: [tip:x86/urgent] x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels

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Message-ID: <21a22ace-fbc3-4f97-a277-9cdf4f2253eb@email.android.com>
Date:	Sat, 12 Apr 2014 12:44:42 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Brian Gerst <brgerst@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	stable <stable@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [tip:x86/urgent] x86-64, modify_ldt: Ban 16-bit segments on 64-bit kernels

Run a 32-bit VM.  The 32-bit kernel does this right.

I suspect it would also work fine in a Qemu user mode guest (is this supported by KVM?), in a ReactOS VM, or some other number of combinations.

The real question is how many real users are actually affected.

On April 12, 2014 12:35:41 PM PDT, Borislav Petkov <bp@...en8.de> wrote:
>On Sat, Apr 12, 2014 at 10:18:25AM -0700, H. Peter Anvin wrote:
>> So Wine regressed and noone noticed? They doesn't sound like an
>active
>> user base.
>
>Btw, wouldn't this obscure use case simply work in a KVM guest with a
>kernel <= 3.14?
>
>Because if so, we simply cut it at 3.14, everything newer has the leak
>fix and people who still want to play phone games on a x86 machine, can
>do so in a guest with an older kernel. Everybody's happy.

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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