linux-kernel - Re: [PATCH v19 5/8] mm: introduce memfd_secret system call to create "secret" memory areas

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: <YKIZ3Zfai00A2O15@kernel.org>
Date:   Mon, 17 May 2021 10:23:09 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christopher Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Hagen Paul Pfeifer <hagen@...u.net>,
        Ingo Molnar <mingo@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        Kees Cook <keescook@...omium.org>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        Mark Rutland <mark.rutland@....com>,
        Michal Hocko <mhocko@...e.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Roman Gushchin <guro@...com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
        Yury Norov <yury.norov@...il.com>, linux-api@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org
Subject: Re: [PATCH v19 5/8] mm: introduce memfd_secret system call to create
 "secret" memory areas

On Fri, May 14, 2021 at 10:50:55AM +0200, David Hildenbrand wrote:
> On 13.05.21 20:47, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@...ux.ibm.com>
> > 
> > Removing of the pages from the direct map may cause its fragmentation
> > on architectures that use large pages to map the physical memory
> > which affects the system performance. However, the original Kconfig
> > text for CONFIG_DIRECT_GBPAGES said that gigabyte pages in the direct
> > map "... can improve the kernel's performance a tiny bit ..." (commit
> > 00d1c5e05736 ("x86: add gbpages switches")) and the recent report [1]
> > showed that "... although 1G mappings are a good default choice,
> > there is no compelling evidence that it must be the only choice".
> > Hence, it is sufficient to have secretmem disabled by default with
> > the ability of a system administrator to enable it at boot time.
> 
> Maybe add a link to the Intel performance evaluation.
 
" ... the recent report [1]" and the link below.
 
> > Pages in the secretmem regions are unevictable and unmovable to
> > avoid accidental exposure of the sensitive data via swap or during
> > page migration.
 
...

> > A page that was a part of the secret memory area is cleared when it
> > is freed to ensure the data is not exposed to the next user of that
> > page.
> 
> You could skip that with init_on_free (and eventually also with
> init_on_alloc) set to avoid double clearing.

Right, but for now I'd prefer to keep this explicit in the secretmem
implementation. We may add the check for init_on_free/init_on_alloc later
on.


> > [1]
> > https://lore.kernel.org/linux-mm/213b4567-46ce-f116-9cdf-bbd0c884eb3c@linux.intel.com/
> 

-- 
Sincerely yours,
Mike.