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: <07aae6e7-4042-1c5c-a482-6ad3a34a3b07@redhat.com>
Date:   Tue, 8 Feb 2022 09:49:35 +0100
From:   David Hildenbrand <david@...hat.com>
To:     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
Cc:     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 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().

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.


[1]
https://lkml.kernel.org/r/20211122135933.arjxpl7wyskkwvwv@box.shutemov.name


-- 
Thanks,

David / dhildenb