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: Mon, 2 Nov 2020 17:40:28 +0200 [thread overview]
Message-ID: <20201102154028.GD4879@kernel.org> (raw)
In-Reply-To: <20201101110935.GA4105325@laniakea>
On Sun, Nov 01, 2020 at 12:09:35PM +0100, Hagen Paul Pfeifer wrote:
> * Mike Rapoport | 2020-09-24 16:28:58 [+0300]:
>
> >This is an implementation of "secret" mappings backed by a file descriptor.
> >I've dropped the boot time reservation patch for now as it is not strictly
> >required for the basic usage and can be easily added later either with or
> >without CMA.
>
> 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.
> 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.
> PS: thank you Mike for your effort!
>
> See the following pseudo-code as an example:
>
>
> // simple assume file-descriptor and mapping is inherited
> // by child for simplicity, ptr is
> int fd = memfd_secret(SECRETMEM_UNCACHED);
> ftruncate(fd, PAGE_SIZE);
> uint32_t *ptr = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
The ptr here will be visible to both parent and child.
> pid_t pid_other;
>
> void signal_handler(int sig)
> {
> // update IPC data on shared, uncachaed, exclusive mapped page
> *ptr += 1;
> // inform other
> sleep(1);
> kill(pid_other, SIGUSR1);
> }
>
> void ipc_loop(void)
> {
> signal(SIGUSR1, signal_handler);
> while (1) {
> sleep(1);
> }
> }
>
> int main(void)
> {
> pid_t child_pid;
>
> switch (child_pid = fork()) {
> case 0:
> pid_other = getppid();
> break;
> default:
> pid_other = child_pid
> break;
> }
>
> ipc_loop();
> }
>
>
> Hagen
>
--
Sincerely yours,
Mike.
next prev parent reply other threads:[~2020-11-02 15:40 UTC|newest]
Thread overview: 57+ 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
2020-09-25 14:57 ` Tycho Andersen
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 [this message]
2020-11-03 13:52 ` Hagen Paul Pfeifer
2020-11-03 16:30 ` Mike Rapoport
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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