linux-kernel - Re: [PATCH v4 02/12] mm/memfd: Introduce MFD

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YgK0zZjq+KNoeNYM@kernel.org>
Date:   Tue, 8 Feb 2022 20:22:05 +0200
From:   Mike Rapoport <rppt@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Vlastimil Babka <vbabka@...e.cz>,
        Chao Peng <chao.p.peng@...ux.intel.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-fsdevel@...r.kernel.org, qemu-devel@...gnu.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
        Hugh Dickins <hughd@...gle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J . Bruce Fields" <bfields@...ldses.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        luto@...nel.org, jun.nakajima@...el.com, dave.hansen@...el.com,
        ak@...ux.intel.com, Mike Rapoport <rppt@...ux.ibm.com>
Subject: Re: [PATCH v4 02/12] mm/memfd: Introduce MFD_INACCESSIBLE flag

On Tue, Feb 08, 2022 at 09:49:35AM +0100, David Hildenbrand wrote:
> On 07.02.22 19:51, Vlastimil Babka wrote:
> > On 1/18/22 14:21, Chao Peng wrote:
> >> Introduce a new memfd_create() flag indicating the content of the
> >> created memfd is inaccessible from userspace. It does this by force
> >> setting F_SEAL_INACCESSIBLE seal when the file is created. It also set
> >> F_SEAL_SEAL to prevent future sealing, which means, it can not coexist
> >> with MFD_ALLOW_SEALING.
> >>
> >> The pages backed by such memfd will be used as guest private memory in
> >> confidential computing environments such as Intel TDX/AMD SEV. Since
> >> page migration/swapping is not yet supported for such usages so these
> >> pages are currently marked as UNMOVABLE and UNEVICTABLE which makes
> >> them behave like long-term pinned pages.
> > 
> > Shouldn't the amount of such memory allocations be restricted? E.g. similar
> > to secretmem_mmap() doing mlock_future_check().

Heh, for me it was easy, I had the VMA :)
 
> I've raised this already in the past and Kirill wanted to look into it [1].
> 
> We'll most certainly need a way to limit/control the amount of
> unswappable + unmovable ("worse than mlock" memory) a user/process can
> consume via this mechanism.

I think the accounting can be handled in notify_fallocate() and
notify_invalidate_page().

> [1] https://lkml.kernel.org/r/20211122135933.arjxpl7wyskkwvwv@box.shutemov.name
>
> -- 
> Thanks,
> 
> David / dhildenb

-- 
Sincerely yours,
Mike.