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Date: Fri, 12 Aug 2016 16:27:39 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: linux-arm-kernel@...ts.infradead.org
Cc: kernel-hardening@...ts.openwall.com,
Will Deacon <will.deacon@....com>,
James Morse <james.morse@....com>,
Kees Cook <keescook@...omium.org>,
Julien Grall <julien.grall@....com>
Subject: [PATCH 0/7] arm64: Privileged Access Never using TTBR0_EL1 switching
This is the first (public) attempt at emulating PAN by disabling
TTBR0_EL1 accesses on arm64. I chose to use a per-CPU saved_ttbr0_el1
variable to store the actual TTBR0 as, IMO, it looks better w.r.t. the
context switching code, to the detriment of a slightly more complex
uaccess_enable() implementation. The alternative was storing the saved
TTBR0 in thread_info but with more complex thread switching since TTBR0
is normally tied to switch_mm() rather than switch_to(). The latter may
also get more complicated if we are to decouple the kernel stack from
thread_info at some point (vmalloc'ed stacks).
The code requires more testing, especially for combinations where UAO is
present but PAN is not.
The patches are also available on this branch:
git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux ttbr0-pan
Thanks for reviewing/testing.
Catalin Marinas (7):
arm64: Factor out PAN enabling/disabling into separate uaccess_*
macros
arm64: Factor out TTBR0_EL1 setting into a specific asm macro
arm64: Introduce uaccess_{disable,enable} functionality based on
TTBR0_EL1
arm64: Disable TTBR0_EL1 during normal kernel execution
arm64: Handle faults caused by inadvertent user access with PAN
enabled
arm64: xen: Enable user access before a privcmd hvc call
arm64: Enable CONFIG_ARM64_TTBR0_PAN
arch/arm64/Kconfig | 8 +++
arch/arm64/include/asm/assembler.h | 106 +++++++++++++++++++++++++++++++-
arch/arm64/include/asm/cpufeature.h | 6 ++
arch/arm64/include/asm/efi.h | 14 +++++
arch/arm64/include/asm/futex.h | 14 ++---
arch/arm64/include/asm/kernel-pgtable.h | 7 +++
arch/arm64/include/asm/mmu_context.h | 3 +-
arch/arm64/include/asm/uaccess.h | 57 ++++++++++++++---
arch/arm64/include/uapi/asm/ptrace.h | 2 +
arch/arm64/kernel/armv8_deprecated.c | 10 +--
arch/arm64/kernel/cpufeature.c | 1 +
arch/arm64/kernel/entry.S | 62 +++++++++++++++++++
arch/arm64/kernel/head.S | 6 +-
arch/arm64/kernel/suspend.c | 12 ++--
arch/arm64/kernel/vmlinux.lds.S | 5 ++
arch/arm64/lib/clear_user.S | 7 +--
arch/arm64/lib/copy_from_user.S | 7 +--
arch/arm64/lib/copy_in_user.S | 7 +--
arch/arm64/lib/copy_to_user.S | 7 +--
arch/arm64/mm/context.c | 25 +++++++-
arch/arm64/mm/fault.c | 21 ++++---
arch/arm64/mm/proc.S | 16 +----
arch/arm64/xen/hypercall.S | 18 ++++++
23 files changed, 347 insertions(+), 74 deletions(-)
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