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Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention

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On Tue, Nov 8, 2016 at 5:16 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Mon, Nov 07, 2016 at 10:12:09PM -0800, Ricardo Neri wrote:
>> There is a caveat, however. Certain applications running in virtual-8086
>> mode, such as DOSEMU[1] and Wine[2], want to utilize the SGDT, SIDT and
>> SLDT instructions for legitimate reasons. In order to keep such
>> applications working, UMIP must be disabled/enabled when entering/exiting
>> virtual-8086 mode.
>
> Would it not be better to emulate these instructions for them? What way
> we can verify they're not malicious.

Forget malice -- if they are really needed for some silly vm86-using
program, let's trap them and emulate them so they return dummy values.

Also, keep in mind that vm86 is already effectively gated behind a
sysctl for non-root.  I think the default should be that, if root has
enabled vm86, it should work.

--Andy

-- 
Andy Lutomirski
AMA Capital Management, LLC

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[PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-08 07:20 +0100
  [PATCH 3/4] x86: Enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-08 07:20 +0100
  [PATCH 4/4] selftests/x86: Add tests for User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-08 07:20 +0100
  [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-08 07:20 +0100
    Re: [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode  Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2016-11-08 17:10 +0100
      Re: [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode  Instruction Prevention Peter Zijlstra <peterz@infradead.org> - 2016-11-08 18:10 +0100
        Re: [PATCH 2/4] x86: Prepare vm86 tasks to handle User-Mode  Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-09 05:30 +0100
  Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Peter Zijlstra <peterz@infradead.org> - 2016-11-08 14:20 +0100
    Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2016-11-08 16:40 +0100
      Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Thomas Gleixner <tglx@linutronix.de> - 2016-11-08 18:00 +0100
        Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-09 05:30 +0100
      Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-09 05:40 +0100
        Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Andy Lutomirski <luto@amacapital.net> - 2016-11-09 12:40 +0100
          Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-10 07:50 +0100
            Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Stas Sergeev <stsp@list.ru> - 2016-11-10 10:00 +0100
              Re: [PATCH 0/4] x86: enable User-Mode Instruction Prevention Ricardo Neri <ricardo.neri-calderon@linux.intel.com> - 2016-11-11 05:20 +0100

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