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Date:	Wed, 11 May 2016 19:11:57 -0700
From:	Kees Cook <>
To:	Andi Kleen <>
Cc:	Hector Marco-Gisbert <>,
	Andy Lutomirski <>,
	LKML <>,
	Thomas Gleixner <>,
	Ingo Molnar <>,
	"H. Peter Anvin" <>,
	"" <>, Brian Gerst <>,
	Borislav Petkov <>,
	Huaitong Han <>,
	Ismael Ripoll Ripoll <>
Subject: Re: [PATCH] x86_64: Disabling read-implies-exec when the stack is executable

On Wed, May 11, 2016 at 3:40 PM, Andi Kleen <> wrote:
>> However, I would tend to agree: RIE should only be needed on 32-bit
>> since 64-bit started its life knowing about no-exec permissions.
> NX was not in the original AMD K8 chips.  Was only added some time later.

So we should retain this behavior for all of 64-bit?

>> set_personality_64bit()'s (which is confusingly just an initializer
>> and not called during the personality() syscall) comment about this
>> makes no sense to me:
>>         /* TBD: overwrites user setup. Should have two bits.
>>            But 64bit processes have always behaved this way,
>>            so it's not too bad. The main problem is just that
>>            32bit childs are affected again. */
>>         current->personality &= ~READ_IMPLIES_EXEC;
> What does not make sense?

I just don't have enough context to make sense of it. What two bits?
Always behaved what way?Affected by what?


Kees Cook
Chrome OS & Brillo Security

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