Linux-Media Archive on lore.kernel.org
 help / color / Atom feed
From: enh <enh@google.com>
To: Evgenii Stepanov <eugenis@google.com>
Cc: Kees Cook <keescook@chromium.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Andrey Konovalov <andreyknvl@google.com>,
	Khalid Aziz <khalid.aziz@oracle.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
	linux-rdma@vger.kernel.org, linux-media@vger.kernel.org,
	kvm@vger.kernel.org,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Yishai Hadas <yishaih@mellanox.com>,
	Felix Kuehling <Felix.Kuehling@amd.com>,
	Alexander Deucher <Alexander.Deucher@amd.com>,
	Christian Koenig <Christian.Koenig@amd.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Jens Wiklander <jens.wiklander@linaro.org>,
	Alex Williamson <alex.williamson@redhat.com>,
	Leon Romanovsky <leon@kernel.org>,
	Dmitry Vyukov <dvyukov@google.com>,
	Kostya Serebryany <kcc@google.com>, Lee Smith <Lee.Smith@arm.com>,
	Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
	Jacob Bramley <Jacob.Bramley@arm.com>,
	Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	Szabolcs Nagy <Szabolcs.Nagy@arm.com>
Subject: Re: [PATCH v15 00/17] arm64: untag user pointers passed to the kernel
Date: Wed, 22 May 2019 16:09:31 -0700
Message-ID: <CAJgzZorUPzrXu0ysDdKwnqdvgWZJ9tqRjF-9_5CU_UV+c0bRCA@mail.gmail.com> (raw)
In-Reply-To: <CAFKCwrjOjdJAbcABp3qxwyYy+hgfyQirvmqGkDSJVJe5pSz0Uw@mail.gmail.com>

On Wed, May 22, 2019 at 4:03 PM Evgenii Stepanov <eugenis@google.com> wrote:
>
> On Wed, May 22, 2019 at 1:47 PM Kees Cook <keescook@chromium.org> wrote:
> >
> > On Wed, May 22, 2019 at 05:35:27PM +0100, Catalin Marinas wrote:
> > > The two hard requirements I have for supporting any new hardware feature
> > > in Linux are (1) a single kernel image binary continues to run on old
> > > hardware while making use of the new feature if available and (2) old
> > > user space continues to run on new hardware while new user space can
> > > take advantage of the new feature.
> >
> > Agreed! And I think the series meets these requirements, yes?
> >
> > > For MTE, we just can't enable it by default since there are applications
> > > who use the top byte of a pointer and expect it to be ignored rather
> > > than failing with a mismatched tag. Just think of a hwasan compiled
> > > binary where TBI is expected to work and you try to run it with MTE
> > > turned on.
> >
> > Ah! Okay, here's the use-case I wasn't thinking of: the concern is TBI
> > conflicting with MTE. And anything that starts using TBI suddenly can't
> > run in the future because it's being interpreted as MTE bits? (Is that
> > the ABI concern? I feel like we got into the weeds about ioctl()s and
> > one-off bugs...)
> >
> > So there needs to be some way to let the kernel know which of three
> > things it should be doing:
> > 1- leaving userspace addresses as-is (present)
> > 2- wiping the top bits before using (this series)
> > 3- wiping the top bits for most things, but retaining them for MTE as
> >    needed (the future)
> >
> > I expect MTE to be the "default" in the future. Once a system's libc has
> > grown support for it, everything will be trying to use MTE. TBI will be
> > the special case (but TBI is effectively a prerequisite).
> >
> > AFAICT, the only difference I see between 2 and 3 will be the tag handling
> > in usercopy (all other places will continue to ignore the top bits). Is
> > that accurate?
> >
> > Is "1" a per-process state we want to keep? (I assume not, but rather it
> > is available via no TBI/MTE CONFIG or a boot-time option, if at all?)
> >
> > To choose between "2" and "3", it seems we need a per-process flag to
> > opt into TBI (and out of MTE). For userspace, how would a future binary
> > choose TBI over MTE? If it's a library issue, we can't use an ELF bit,
> > since the choice may be "late" after ELF load (this implies the need
> > for a prctl().) If it's binary-only ("built with HWKASan") then an ELF
> > bit seems sufficient. And without the marking, I'd expect the kernel to
> > enforce MTE when there are high bits.
> >
> > > I would also expect the C library or dynamic loader to check for the
> > > presence of a HWCAP_MTE bit before starting to tag memory allocations,
> > > otherwise it would get SIGILL on the first MTE instruction it tries to
> > > execute.
> >
> > I've got the same question as Elliot: aren't MTE instructions just NOP
> > to older CPUs? I.e. if the CPU (or kernel) don't support it, it just
> > gets entirely ignored: checking is only needed to satisfy curiosity
> > or behavioral expectations.
>
> MTE instructions are not NOP. Most of them have side effects (changing
> register values, zeroing memory).

no, i meant "they're encoded in a space that was previously no-ops, so
running on MTE code on old hardware doesn't cause SIGILL".

> This only matters for stack tagging, though. Heap tagging is a runtime
> decision in the allocator.
>
> If an image needs to run on old hardware, it will have to do heap tagging only.
>
> > To me, the conflict seems to be using TBI in the face of expecting MTE to
> > be the default state of the future. (But the internal changes needed
> > for TBI -- this series -- is a prereq for MTE.)
> >
> > --
> > Kees Cook

  reply index

Thread overview: 99+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-06 16:30 Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 01/17] uaccess: add untagged_addr definition for other arches Andrey Konovalov
2019-05-29 14:49   ` Khalid Aziz
2019-05-06 16:30 ` [PATCH v15 02/17] arm64: untag user pointers in access_ok and __uaccess_mask_ptr Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 03/17] lib, arm64: untag user pointers in strn*_user Andrey Konovalov
2019-05-22 10:41   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 04/17] mm: add ksys_ wrappers to memory syscalls Andrey Konovalov
2019-05-22 10:56   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 05/17] arms64: untag user pointers passed " Andrey Konovalov
2019-05-22 11:49   ` Catalin Marinas
2019-05-22 21:16     ` Evgenii Stepanov
2019-05-23  9:04       ` Catalin Marinas
2019-05-24  4:23         ` Evgenii Stepanov
2019-05-24 15:41   ` Andrew Murray
2019-05-25  9:57   ` Catalin Marinas
2019-05-27  9:42   ` Catalin Marinas
2019-05-27 14:37   ` Catalin Marinas
2019-05-28 14:54     ` Andrew Murray
2019-05-28 15:40       ` Catalin Marinas
2019-05-28 15:56         ` Dave Martin
2019-05-28 16:34           ` Catalin Marinas
2019-05-29 12:42             ` Dave Martin
2019-05-29 13:23               ` Catalin Marinas
2019-05-29 15:18                 ` Dave Martin
2019-05-28 23:33         ` Khalid Aziz
2019-05-29 14:20           ` Catalin Marinas
2019-05-29 19:16             ` Khalid Aziz
2019-05-30 15:11               ` Catalin Marinas
2019-05-30 16:05                 ` Khalid Aziz
2019-05-30 16:57                   ` Catalin Marinas
2019-05-28 13:05   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 06/17] mm: untag user pointers in do_pages_move Andrey Konovalov
2019-05-22 11:51   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 07/17] mm, arm64: untag user pointers in mm/gup.c Andrey Konovalov
2019-05-22 11:56   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 08/17] mm, arm64: untag user pointers in get_vaddr_frames Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 09/17] fs, arm64: untag user pointers in copy_mount_options Andrey Konovalov
2019-05-22 12:09   ` Catalin Marinas
2019-05-06 16:30 ` [PATCH v15 10/17] fs, arm64: untag user pointers in fs/userfaultfd.c Andrey Konovalov
2019-05-06 16:30 ` [PATCH v15 11/17] drm/amdgpu, arm64: untag user pointers Andrey Konovalov
2019-05-07 16:43   ` Kuehling, Felix
2019-05-06 16:30 ` [PATCH v15 12/17] drm/radeon, arm64: untag user pointers in radeon_gem_userptr_ioctl Andrey Konovalov
2019-05-07 16:44   ` Kuehling, Felix
2019-05-06 16:30 ` [PATCH v15 13/17] IB, arm64: untag user pointers in ib_uverbs_(re)reg_mr() Andrey Konovalov
2019-05-06 19:50   ` Jason Gunthorpe
2019-05-07  6:33     ` Leon Romanovsky
2019-05-06 16:31 ` [PATCH v15 14/17] media/v4l2-core, arm64: untag user pointers in videobuf_dma_contig_user_get Andrey Konovalov
2019-05-24 13:13   ` Mauro Carvalho Chehab
2019-05-06 16:31 ` [PATCH v15 15/17] tee, arm64: untag user pointers in tee_shm_register Andrey Konovalov
2019-05-06 16:31 ` [PATCH v15 16/17] vfio/type1, arm64: untag user pointers in vaddr_get_pfn Andrey Konovalov
2019-05-06 16:31 ` [PATCH v15 17/17] selftests, arm64: add a selftest for passing tagged pointers to kernel Andrey Konovalov
2019-05-22 14:16   ` Catalin Marinas
2019-05-31 14:21     ` Andrey Konovalov
2019-05-31 16:22       ` Catalin Marinas
2019-05-17 14:49 ` [PATCH v15 00/17] arm64: untag user pointers passed to the kernel Catalin Marinas
2019-05-20 23:53   ` Evgenii Stepanov
2019-05-21 18:29     ` Catalin Marinas
2019-05-22  0:04       ` Kees Cook
2019-05-22 10:11         ` Catalin Marinas
2019-05-22 15:30           ` enh
2019-05-22 16:35             ` Catalin Marinas
2019-05-22 16:58               ` enh
2019-05-23 15:21                 ` Catalin Marinas
2019-05-22 20:47               ` Kees Cook
2019-05-22 23:03                 ` Evgenii Stepanov
2019-05-22 23:09                   ` enh [this message]
2019-05-23  7:34                     ` Catalin Marinas
2019-05-23 14:44                 ` Catalin Marinas
2019-05-23 15:44                   ` enh
2019-05-23 17:00                     ` Catalin Marinas
2019-05-23 16:38                   ` Kees Cook
2019-05-23 17:43                     ` Catalin Marinas
2019-05-23 21:31                       ` Kees Cook
2019-05-24 11:20                         ` Catalin Marinas
2019-05-28 17:02                         ` Catalin Marinas
2019-06-02  5:06                           ` Kees Cook
2019-05-22 19:21             ` Kees Cook
2019-05-22 20:15               ` enh
2019-05-23 15:08               ` Catalin Marinas
2019-05-23 17:51         ` Khalid Aziz
2019-05-23 20:11           ` Catalin Marinas
2019-05-23 21:42             ` Khalid Aziz
2019-05-23 21:49             ` Khalid Aziz
2019-05-24 10:11               ` Catalin Marinas
2019-05-24 14:25                 ` Khalid Aziz
2019-05-28 14:14                   ` Andrey Konovalov
2019-05-29  6:11                     ` Christoph Hellwig
2019-05-29 12:12                       ` Catalin Marinas
2019-05-30 17:15                     ` Catalin Marinas
2019-05-31 14:29                       ` Andrey Konovalov
2019-05-31 16:19                         ` Catalin Marinas
2019-05-31 16:24                           ` Andrey Konovalov
2019-05-31 16:46                             ` Catalin Marinas
2019-05-21 18:48   ` Jason Gunthorpe
2019-05-22 13:49     ` Dave Martin
2019-05-23  0:20       ` Jason Gunthorpe
2019-05-23 10:42         ` Dave Martin
2019-05-23 16:57           ` Catalin Marinas
2019-05-24 14:23             ` Dave Martin

Reply instructions:

You may reply publically to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CAJgzZorUPzrXu0ysDdKwnqdvgWZJ9tqRjF-9_5CU_UV+c0bRCA@mail.gmail.com \
    --to=enh@google.com \
    --cc=Alexander.Deucher@amd.com \
    --cc=Christian.Koenig@amd.com \
    --cc=Dave.Martin@arm.com \
    --cc=Felix.Kuehling@amd.com \
    --cc=Jacob.Bramley@arm.com \
    --cc=Lee.Smith@arm.com \
    --cc=Ramana.Radhakrishnan@arm.com \
    --cc=Ruben.Ayrapetyan@arm.com \
    --cc=Szabolcs.Nagy@arm.com \
    --cc=akpm@linux-foundation.org \
    --cc=alex.williamson@redhat.com \
    --cc=amd-gfx@lists.freedesktop.org \
    --cc=andreyknvl@google.com \
    --cc=catalin.marinas@arm.com \
    --cc=dri-devel@lists.freedesktop.org \
    --cc=dvyukov@google.com \
    --cc=eugenis@google.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=jens.wiklander@linaro.org \
    --cc=kcc@google.com \
    --cc=keescook@chromium.org \
    --cc=kevin.brodsky@arm.com \
    --cc=khalid.aziz@oracle.com \
    --cc=kvm@vger.kernel.org \
    --cc=leon@kernel.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-kselftest@vger.kernel.org \
    --cc=linux-media@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-rdma@vger.kernel.org \
    --cc=luc.vanoostenryck@gmail.com \
    --cc=mark.rutland@arm.com \
    --cc=mchehab@kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=vincenzo.frascino@arm.com \
    --cc=will.deacon@arm.com \
    --cc=yishaih@mellanox.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Media Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-media/0 linux-media/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-media linux-media/ https://lore.kernel.org/linux-media \
		linux-media@vger.kernel.org linux-media@archiver.kernel.org
	public-inbox-index linux-media

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-media


AGPL code for this site: git clone https://public-inbox.org/ public-inbox