Linux-ARM-Kernel Archive on lore.kernel.org
 help / color / Atom feed
From: Catalin Marinas <catalin.marinas@arm.com>
To: Andrey Konovalov <andreyknvl@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
	kvm@vger.kernel.org, Szabolcs Nagy <Szabolcs.Nagy@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	dri-devel@lists.freedesktop.org, linux-mm@kvack.org,
	linux-kselftest@vger.kernel.org,
	Felix Kuehling <Felix.Kuehling@amd.com>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	Jacob Bramley <Jacob.Bramley@arm.com>,
	Leon Romanovsky <leon@kernel.org>,
	linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org,
	Dmitry Vyukov <dvyukov@google.com>,
	Dave Martin <Dave.Martin@arm.com>,
	Evgeniy Stepanov <eugenis@google.com>,
	linux-media@vger.kernel.org,
	Kevin Brodsky <kevin.brodsky@arm.com>,
	Kees Cook <keescook@chromium.org>,
	Ruben Ayrapetyan <Ruben.Ayrapetyan@arm.com>,
	Ramana Radhakrishnan <Ramana.Radhakrishnan@arm.com>,
	Alex Williamson <alex.williamson@redhat.com>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	Kostya Serebryany <kcc@google.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Yishai Hadas <yishaih@mellanox.com>,
	linux-kernel@vger.kernel.org,
	Jens Wiklander <jens.wiklander@linaro.org>,
	Lee Smith <Lee.Smith@arm.com>,
	Alexander Deucher <Alexander.Deucher@amd.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Robin Murphy <robin.murphy@arm.com>,
	Christian Koenig <Christian.Koenig@amd.com>,
	Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Subject: Re: [PATCH v15 00/17] arm64: untag user pointers passed to the kernel
Date: Fri, 17 May 2019 15:49:31 +0100
Message-ID: <20190517144931.GA56186@arrakis.emea.arm.com> (raw)
In-Reply-To: <cover.1557160186.git.andreyknvl@google.com>

Hi Andrey,

On Mon, May 06, 2019 at 06:30:46PM +0200, Andrey Konovalov wrote:
> One of the alternative approaches to untagging that was considered is to
> completely strip the pointer tag as the pointer enters the kernel with
> some kind of a syscall wrapper, but that won't work with the countless
> number of different ioctl calls. With this approach we would need a custom
> wrapper for each ioctl variation, which doesn't seem practical.

The more I look at this problem, the less convinced I am that we can
solve it in a way that results in a stable ABI covering ioctls(). While
for the Android kernel codebase it could be simpler as you don't upgrade
the kernel version every 2.5 months, for the mainline kernel this
doesn't scale. Any run-time checks are relatively limited in terms of
drivers covered. Better static checking would be nice as a long term
solution but we didn't get anywhere with the discussion last year.

IMO (RFC for now), I see two ways forward:

1. Make this a user space problem and do not allow tagged pointers into
   the syscall ABI. A libc wrapper would have to convert structures,
   parameters before passing them into the kernel. Note that we can
   still support the hardware MTE in the kernel by enabling tagged
   memory ranges, saving/restoring tags etc. but not allowing tagged
   addresses at the syscall boundary.

2. Similar shim to the above libc wrapper but inside the kernel
   (arch/arm64 only; most pointer arguments could be covered with an
   __SC_CAST similar to the s390 one). There are two differences from
   what we've discussed in the past:

   a) this is an opt-in by the user which would have to explicitly call
      prctl(). If it returns -ENOTSUPP etc., the user won't be allowed
      to pass tagged pointers to the kernel. This would probably be the
      responsibility of the C lib to make sure it doesn't tag heap
      allocations. If the user did not opt-in, the syscalls are routed
      through the normal path (no untagging address shim).

   b) ioctl() and other blacklisted syscalls (prctl) will not accept
      tagged pointers (to be documented in Vicenzo's ABI patches).

It doesn't solve the problems we are trying to address but 2.a saves us
from blindly relaxing the ABI without knowing how to easily assess new
code being merged (over 500K lines between kernel versions). Existing
applications (who don't opt-in) won't inadvertently start using the new
ABI which could risk becoming de-facto ABI that we need to support on
the long run.

Option 1 wouldn't solve the ioctl() problem either and while it makes
things simpler for the kernel, I am aware that it's slightly more
complicated in user space (but I really don't mind if you prefer option
1 ;)).

The tagged pointers (whether hwasan or MTE) should ideally be a
transparent feature for the application writer but I don't think we can
solve it entirely and make it seamless for the multitude of ioctls().
I'd say you only opt in to such feature if you know what you are doing
and the user code takes care of specific cases like ioctl(), hence the
prctl() proposal even for the hwasan.

Comments welcomed.

-- 
Catalin

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  parent 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 ` Catalin Marinas [this message]
2019-05-20 23:53   ` [PATCH v15 00/17] arm64: untag user pointers passed to the kernel 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
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=20190517144931.GA56186@arrakis.emea.arm.com \
    --to=catalin.marinas@arm.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=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=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-ARM-Kernel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/0 linux-arm-kernel/git/0.git
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/1 linux-arm-kernel/git/1.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-arm-kernel linux-arm-kernel/ https://lore.kernel.org/linux-arm-kernel \
		linux-arm-kernel@lists.infradead.org infradead-linux-arm-kernel@archiver.kernel.org
	public-inbox-index linux-arm-kernel


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-arm-kernel


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