Re: [PATCH] x86_64: Disabling read-implies-exec when the stack is executable

From	Kees Cook <keescook@chromium.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] x86_64: Disabling read-implies-exec when the stack is executable
Date	2016-05-12 04:20 +0200
Message-ID	<rxOoh-4db-1@gated-at.bofh.it> (permalink)
References	<rxzSi-6v5-13@gated-at.bofh.it> <rxJeW-7wL-7@gated-at.bofh.it> <rxL73-U4-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, May 11, 2016 at 3:40 PM, Andi Kleen <ak@linux.intel.com> 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

-- 
Kees Cook
Chrome OS & Brillo Security

Thread

[PATCH] x86_64: Disabling read-implies-exec when the stack is executable Hector Marco-Gisbert <hecmargi@upv.es> - 2016-05-11 12:50 +0200
  Re: [PATCH] x86_64: Disabling read-implies-exec when the stack is executable Kees Cook <keescook@chromium.org> - 2016-05-11 22:50 +0200
    Re: [PATCH] x86_64: Disabling read-implies-exec when the stack is  executable Andi Kleen <ak@linux.intel.com> - 2016-05-12 00:50 +0200
      Re: [PATCH] x86_64: Disabling read-implies-exec when the stack is executable Kees Cook <keescook@chromium.org> - 2016-05-12 04:20 +0200
    Re: [PATCH] x86_64: Disabling read-implies-exec when the stack is  executable Ingo Molnar <mingo@kernel.org> - 2016-05-16 13:00 +0200

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