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Subject: Re: [RFC PATCH v2 15/27] mm/mprotect: Prevent mprotect from changing
 shadow stack
To:     Yu-cheng Yu <yu-cheng.yu@intel.com>,
        Peter Zijlstra <peterz@infradead.org>
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Message-ID: <a4dae7e3-58a7-5c38-1071-2deee758bb98@linux.intel.com>
Date:   Wed, 11 Jul 2018 09:22:28 -0700
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On 07/11/2018 09:07 AM, Yu-cheng Yu wrote:
>> Why do we need to disallow this? AFAICT the worst that can happen is
>> that a process wrecks itself, so what?
> Agree.  I will remove the patch.

No so quick. :)

We still need to find out a way to handle things that ask for an
mprotect() which is incompatible with shadow stacks.  PROT_READ without
PROT_WRITE comes to mind.  We also need to be careful that we don't
copy-on-write/copy-on-access pages which fault on PROT_NONE.  I *think*
it'll get done correctly but we have to be sure.

BTW, where are all the selftests for this code?  We're slowly building
up a list of pathological things that need to get tested.

I don't think this can or should get merged before we have selftests.