From: Guilherme Piccoli <gpiccoli@canonical.com>
To: David Hildenbrand <david@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
linux-mm@kvack.org, kernel-hardening@lists.openwall.com,
linux-hardening@vger.kernel.org,
linux-security-module@vger.kernel.org,
"Guilherme G. Piccoli" <kernel@gpiccoli.net>,
Thadeu Lima de Souza Cascardo <cascardo@canonical.com>,
Alexander Potapenko <glider@google.com>,
James Morris <jamorris@linux.microsoft.com>,
Kees Cook <keescook@chromium.org>
Subject: Re: [PATCH] mm, hugetlb: Avoid double clearing for hugetlb pages
Date: Tue, 20 Oct 2020 17:19:42 -0300 [thread overview]
Message-ID: <CAHD1Q_wQrnSEGOvbCi0uhHZ5bRf=inzPdOhGKJ9PkVms5GSWRA@mail.gmail.com> (raw)
In-Reply-To: <5650dc95-4ae2-05d3-c71a-3828d35bd49b@redhat.com>
When I first wrote that, the design was a bit different, the flag was
called __GFP_HTLB_PAGE or something like that. The design was to
signal/mark the composing pages of hugetlb as exactly this: they are
pages composing a huge page of hugetlb "type". Then, I skipped the
"init_on_alloc" thing for such pages.
If your concern is more about semantics (or giving multiple users,
like drivers, the power to try "optimize" their code and skip this
security feature), I think my first approach was better! This way, the
flag would be restricted to hugetlb usage only.
I've changed my mind about that approach before submitting for 2 reasons:
(a) It feels a waste of resources having a GFP flag *only* to signal
regular pages composing hugetlb pages, it's a single user only,
forever!
(b) Having 2 conditional settings on __GFP_BITS_SHIFT (LOCKDEP and
HUGETLB) started to make this define a bit tricky to code, since we'd
have 2 Kconfig-conditional bits to be set.
So, I've moved to this other approach, hereby submitted.
Cheers,
Guilherme
next prev parent reply other threads:[~2020-10-20 20:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-19 18:28 [PATCH] mm, hugetlb: Avoid double clearing for hugetlb pages Guilherme G. Piccoli
2020-10-20 8:20 ` Michal Hocko
2020-10-20 13:36 ` David Hildenbrand
2020-10-20 16:55 ` Mike Kravetz
2020-10-20 19:19 ` Guilherme G. Piccoli
2020-10-20 20:07 ` David Hildenbrand
2020-10-20 20:19 ` Guilherme Piccoli [this message]
2020-10-21 6:25 ` Michal Hocko
2020-10-20 20:28 ` David Hildenbrand
2020-10-21 6:15 ` Michal Hocko
2020-10-21 9:50 ` David Hildenbrand
2020-10-21 11:31 ` Michal Hocko
2020-10-21 23:32 ` Mike Kravetz
2020-10-22 8:04 ` David Hildenbrand
2020-10-22 8:55 ` Michal Hocko
2020-10-23 8:23 ` David Hildenbrand
2020-11-05 19:37 ` Guilherme G. Piccoli
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