From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: linux-arm-kernel@lists.infradead.org,
Tomas Paukrt <tomas.paukrt@advantech.cz>
Cc: Will Deacon <will@kernel.org>, Alexander Viro <viro@zeniv.linux.org.uk>
Subject: [PATCH 0/3] Fix uaccess kernel protection on ARMv5 and earlier
Date: Mon, 4 May 2020 14:34:35 +0100 [thread overview]
Message-ID: <20200504133435.GD1551@shell.armlinux.org.uk> (raw)
Hi,
This series fixes a problem with the ability for the user accessors to
access kernel space in a very specific circumstance. I'm greatful to
Tomas Paukrt for having the patience to track down the problem.
This only happens when the following conditions are met:
- ARMv5 or earlier CPU
- Software PAN is disabled
- Nested exceptions that want to use user accessors to touch kernel
space (implying use of the set_fs() function.)
The result is that the domain register is not preserved across the
nested exception, but instead is reset to prevent kernel accesses
while we are inside a region that should be permitting them.
Further technical details can be found in patch 3.
Patch 1 consolidates the uaccess macros into a new include file.
Patch 2 integrates the address limit save/reset/restore into this
file, moving it from entry-armv.S, since we need to integrate this
with the domain register manipulations.
Patch 3 ensures that the domain register is always saved and restored
not only if we are using software PAN, but if we're using CPU domains
for kernel memory protection.
arch/arm/include/asm/assembler.h | 75 +-----------------------
arch/arm/include/asm/uaccess-asm.h | 117 +++++++++++++++++++++++++++++++++++++
arch/arm/kernel/entry-armv.S | 11 +---
arch/arm/kernel/entry-header.S | 9 +--
4 files changed, 123 insertions(+), 89 deletions(-)
create mode 100644 arch/arm/include/asm/uaccess-asm.h
--
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 10.2Mbps down 587kbps up
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next reply other threads:[~2020-05-04 13:36 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-04 13:34 Russell King - ARM Linux admin [this message]
2020-05-04 13:34 ` [PATCH 1/3] ARM: uaccess: consolidate uaccess asm to asm/uaccess-asm.h Russell King
2020-05-04 13:35 ` [PATCH 2/3] ARM: uaccess: integrate uaccess_save and uaccess_restore Russell King
2020-05-04 13:35 ` [PATCH 3/3] ARM: uaccess: fix DACR mismatch with nested exceptions Russell King
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