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Date: Fri, 23 Oct 2020 10:23:07 +0200
From: David Hildenbrand <david@...hat.com>
To: Michal Hocko <mhocko@...e.com>
Cc: Mike Kravetz <mike.kravetz@...cle.com>,
"Guilherme G. Piccoli" <gpiccoli@...onical.com>, linux-mm@...ck.org,
kernel-hardening@...ts.openwall.com, linux-hardening@...r.kernel.org,
linux-security-module@...r.kernel.org, kernel@...ccoli.net,
cascardo@...onical.com, Alexander Potapenko <glider@...gle.com>,
James Morris <jamorris@...ux.microsoft.com>,
Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] mm, hugetlb: Avoid double clearing for hugetlb pages
On 22.10.20 10:55, Michal Hocko wrote:
> On Thu 22-10-20 10:04:50, David Hildenbrand wrote:
> [...]
>>> None of that would address the original point of this thread, the global
>>> init_on_alloc parameter.
>>
>> Yes, but I guess we're past that: whatever leaves the buddy shall be
>> zeroed out. That's the whole point of that security hardening mechanism.
>
> Hugetlb can control its zeroying behavior via mount option (for
> MAP_HUGETLB controled by a command line parameter). If the page fault
> handler can recognize the pre-initialized pages then both init_on* can
Right, looking at init_on_alloc tells you if you have to zero after
alloc or if it's already been done even though you didn't pass GFP_ZERO.
--
Thanks,
David / dhildenb
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