From: Mike Rapoport <rppt@kernel.org>
To: Hagen Paul Pfeifer <hagen@jauu.net>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Borislav Petkov <bp@alien8.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Christopher Lameter <cl@linux.com>,
Dan Williams <dan.j.williams@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
David Hildenbrand <david@redhat.com>,
Elena Reshetova <elena.reshetova@intel.com>,
"H. Peter Anvin" <hpa@zytor.com>, Idan Yaniv <idan.yaniv@ibm.com>,
Ingo Molnar <mingo@redhat.com>,
James Bottomley <jejb@linux.ibm.com>,
"Kirill A. Shutemov" <kirill@shutemov.name>,
Matthew Wilcox <willy@infradead.org>,
Mark Rutland <mark.rutland@arm.com>,
Mike Rapoport <rppt@linux.ibm.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
Shuah Khan <shuah@kernel.org>, Tycho Andersen <tycho@tycho.ws>,
Will Deacon <will@kernel.org>,
linux-api@vger.kernel.org, linux-arch@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org,
x86@kernel.org
Subject: Re: [PATCH v6 0/6] mm: introduce memfd_secret system call to create "secret" memory areas
Date: Tue, 3 Nov 2020 18:30:02 +0200 [thread overview]
Message-ID: <20201103163002.GK4879@kernel.org> (raw)
In-Reply-To: <1547601988.128687.1604411534845@office.mailbox.org>
On Tue, Nov 03, 2020 at 02:52:14PM +0100, Hagen Paul Pfeifer wrote:
> > On 11/02/2020 4:40 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> > > Isn't memfd_secret currently *unnecessarily* designed to be a "one task
> > > feature"? memfd_secret fulfills exactly two (generic) features:
> > >
> > > - address space isolation from kernel (aka SECRET_EXCLUSIVE, not in kernel's
> > > direct map) - hide from kernel, great
> > > - disabling processor's memory caches against speculative-execution vulnerabilities
> > > (spectre and friends, aka SECRET_UNCACHED), also great
> > >
> > > But, what about the following use-case: implementing a hardened IPC mechanism
> > > where even the kernel is not aware of any data and optionally via SECRET_UNCACHED
> > > even the hardware caches are bypassed! With the patches we are so close to
> > > achieving this.
> > >
> > > How? Shared, SECRET_EXCLUSIVE and SECRET_UNCACHED mmaped pages for IPC
> > > involved tasks required to know this mapping (and memfd_secret fd). After IPC
> > > is done, tasks can copy sensitive data from IPC pages into memfd_secret()
> > > pages, un-sensitive data can be used/copied everywhere.
> >
> > As long as the task share the file descriptor, they can share the
> > secretmem pages, pretty much like normal memfd.
>
> Including process_vm_readv() and process_vm_writev()? Let's take a hypothetical
> "dbus-daemon-secure" service that receives data from process A and wants to
> copy/distribute it to data areas of N other processes. Much like dbus but without
> SOCK_DGRAM rather direct copy into secretmem/mmap pages (ring-buffer). Should be
> possible, right?
I'm not sure I follow you here.
For process_vm_readv() and process_vm_writev() secremem will be only
accessible on the local part, but not on the remote.
So copying data to secretmem pages using process_vm_writev wouldn't
work.
> > > One missing piece is still the secure zeroization of the page(s) if the
> > > mapping is closed by last process to guarantee a secure cleanup. This can
> > > probably done as an general mmap feature, not coupled to memfd_secret() and
> > > can be done independently ("reverse" MAP_UNINITIALIZED feature).
> >
> > There are "init_on_alloc" and "init_on_free" kernel parameters that
> > enable zeroing of the pages on alloc and on free globally.
> > Anyway, I'll add zeroing of the freed memory to secretmem.
>
> Great, this allows page-specific (thus runtime-performance-optimized) zeroing
> of secured pages. init_on_free lowers the performance to much and is not precice
> enough.
>
> Hagen
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2020-11-03 16:30 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 13:28 [PATCH v6 0/6] mm: introduce memfd_secret system call to create "secret" memory areas Mike Rapoport
2020-09-24 13:28 ` [PATCH v6 1/6] mm: add definition of PMD_PAGE_ORDER Mike Rapoport
2020-09-24 13:29 ` [PATCH v6 2/6] mmap: make mlock_future_check() global Mike Rapoport
2020-09-24 13:29 ` [PATCH v6 3/6] mm: introduce memfd_secret system call to create "secret" memory areas Mike Rapoport
2020-09-29 4:58 ` Edgecombe, Rick P
2020-09-29 13:06 ` Mike Rapoport
2020-09-29 20:06 ` Edgecombe, Rick P
2020-09-30 10:35 ` Mike Rapoport
2020-09-30 20:11 ` Edgecombe, Rick P
2020-10-11 9:42 ` Mike Rapoport
2020-09-24 13:29 ` [PATCH v6 4/6] arch, mm: wire up memfd_secret system call were relevant Mike Rapoport
2020-09-24 13:29 ` [PATCH v6 5/6] mm: secretmem: use PMD-size pages to amortize direct map fragmentation Mike Rapoport
2020-09-25 7:41 ` Peter Zijlstra
2020-09-25 9:00 ` David Hildenbrand
2020-09-25 9:50 ` Peter Zijlstra
2020-09-25 10:31 ` Mark Rutland
2020-09-29 14:04 ` Mike Rapoport
2020-09-29 13:07 ` Mike Rapoport
2020-09-29 13:06 ` Mike Rapoport
2020-09-29 13:05 ` Mike Rapoport
2020-09-29 14:12 ` Peter Zijlstra
2020-09-29 14:31 ` Dave Hansen
2020-09-29 14:58 ` Mike Rapoport
2020-09-29 15:15 ` Peter Zijlstra
2020-09-30 10:27 ` Mike Rapoport
2020-09-30 14:39 ` James Bottomley
2020-09-30 14:45 ` David Hildenbrand
2020-09-30 15:17 ` James Bottomley
2020-09-30 15:25 ` David Hildenbrand
2020-09-30 15:09 ` Matthew Wilcox
2020-10-01 8:14 ` Mike Rapoport
2020-09-29 15:03 ` James Bottomley
2020-09-30 10:20 ` Mike Rapoport
2020-09-30 10:43 ` Peter Zijlstra
2020-09-24 13:29 ` [PATCH v6 6/6] secretmem: test: add basic selftest for memfd_secret(2) Mike Rapoport
2020-09-24 13:35 ` [PATCH] man2: new page describing memfd_secret() system call Mike Rapoport
2020-09-24 14:55 ` Alejandro Colomar
2020-10-03 9:32 ` Alejandro Colomar
2020-10-05 7:32 ` Mike Rapoport
2020-11-16 21:01 ` [PATCH v2] memfd_secret.2: New " Alejandro Colomar
2020-11-17 6:26 ` Mike Rapoport
2020-09-25 2:34 ` [PATCH v6 0/6] mm: introduce memfd_secret system call to create "secret" memory areas Andrew Morton
2020-09-25 6:42 ` Mike Rapoport
2020-11-01 11:09 ` Hagen Paul Pfeifer
2020-11-02 15:40 ` Mike Rapoport
2020-11-03 13:52 ` Hagen Paul Pfeifer
2020-11-03 16:30 ` Mike Rapoport [this message]
2020-11-04 11:39 ` Hagen Paul Pfeifer
2020-11-04 17:02 ` Mike Rapoport
2020-11-09 10:41 ` Hagen Paul Pfeifer
2020-11-02 9:11 ` David Hildenbrand
2020-11-02 9:31 ` David Hildenbrand
2020-11-02 17:43 ` Mike Rapoport
2020-11-02 17:51 ` David Hildenbrand
2020-11-03 9:52 ` Mike Rapoport
2020-11-03 10:11 ` David Hildenbrand
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