[RFC PATCH 0/6] arm64: untag user pointers passed to the kernel

From: Andrey Konovalov <andreyknvl@google.com>
To: "Catalin Marinas" <catalin.marinas@arm.com>,
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Cc: Dmitry Vyukov <dvyukov@google.com>,
	Kostya Serebryany <kcc@google.com>,
	Evgeniy Stepanov <eugenis@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>,
	Andrey Konovalov <andreyknvl@google.com>
Subject: [RFC PATCH 0/6] arm64: untag user pointers passed to the kernel
Date: Fri,  9 Mar 2018 15:01:58 +0100	[thread overview]
Message-ID: <cover.1520600533.git.andreyknvl@google.com> (raw)

arm64 has a feature called Top Byte Ignore, which allows to embed pointer
tags into the top byte of each pointer. Userspace programs (such as
HWASan, a memory debugging tool [1]) might use this feature and pass
tagged user pointers to the kernel through syscalls or other interfaces.

This patch makes a few of the kernel interfaces accept tagged user
pointers. The kernel is already able to handle user faults with tagged
pointers and has the untagged_addr macro, which this patchset reuses.

We're not trying to cover all possible ways the kernel accepts user
pointers in one patchset, so this one should be considered as a start.
It would be nice to learn about the interfaces that I missed though.

Sending this as an RFC, as I'm not sure if this should be committed as is,
and would like to receive some feedback.

Thanks!

[1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html

Andrey Konovalov (6):
  arm64: add type casts to untagged_addr macro
  arm64: untag user addresses in copy_from_user and others
  mm, arm64: untag user addresses in memory syscalls
  mm, arm64: untag user addresses in mm/gup.c
  lib, arm64: untag addrs passed to strncpy_from_user and strnlen_user
  arch: add untagged_addr definition for other arches

 arch/alpha/include/asm/uaccess.h      |  2 ++
 arch/arc/include/asm/uaccess.h        |  1 +
 arch/arm/include/asm/uaccess.h        |  2 ++
 arch/arm64/include/asm/uaccess.h      |  9 +++++++--
 arch/blackfin/include/asm/uaccess.h   |  2 ++
 arch/c6x/include/asm/uaccess.h        |  2 ++
 arch/cris/include/asm/uaccess.h       |  2 ++
 arch/frv/include/asm/uaccess.h        |  2 ++
 arch/ia64/include/asm/uaccess.h       |  2 ++
 arch/m32r/include/asm/uaccess.h       |  2 ++
 arch/m68k/include/asm/uaccess.h       |  2 ++
 arch/metag/include/asm/uaccess.h      |  2 ++
 arch/microblaze/include/asm/uaccess.h |  2 ++
 arch/mips/include/asm/uaccess.h       |  2 ++
 arch/mn10300/include/asm/uaccess.h    |  2 ++
 arch/nios2/include/asm/uaccess.h      |  2 ++
 arch/openrisc/include/asm/uaccess.h   |  2 ++
 arch/parisc/include/asm/uaccess.h     |  2 ++
 arch/powerpc/include/asm/uaccess.h    |  2 ++
 arch/riscv/include/asm/uaccess.h      |  2 ++
 arch/score/include/asm/uaccess.h      |  2 ++
 arch/sh/include/asm/uaccess.h         |  2 ++
 arch/sparc/include/asm/uaccess.h      |  2 ++
 arch/tile/include/asm/uaccess.h       |  2 ++
 arch/x86/include/asm/uaccess.h        |  2 ++
 arch/xtensa/include/asm/uaccess.h     |  2 ++
 include/asm-generic/uaccess.h         |  2 ++
 lib/strncpy_from_user.c               |  2 ++
 lib/strnlen_user.c                    |  2 ++
 mm/gup.c                              | 12 ++++++++++++
 mm/madvise.c                          |  2 ++
 mm/mempolicy.c                        |  6 ++++++
 mm/mincore.c                          |  2 ++
 mm/mlock.c                            |  5 +++++
 mm/mmap.c                             |  9 +++++++++
 mm/mprotect.c                         |  2 ++
 mm/mremap.c                           |  2 ++
 mm/msync.c                            |  3 +++
 38 files changed, 105 insertions(+), 2 deletions(-)

-- 
2.16.2.395.g2e18187dfd-goog