From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>,
maz@kernel.org, catalin.marinas@arm.com, will@kernel.org,
mark.rutland@arm.com, anshuman.khandual@arm.com,
qperret@google.com, kernel-team@android.com
Subject: [PATCH 0/2] arm64: use XN table mappings for the linear region
Date: Thu, 4 Mar 2021 18:11:43 +0100 [thread overview]
Message-ID: <20210304171145.12281-1-ardb@kernel.org> (raw)
This patch tweaks the kernel page table population code to set the UXNTable
and PXNTable bits on all table entries that cover the linear region. This
removes the ability for lower level mappings to grant executable permissions
which are never needed in the linear region. And given that swapper's PGD
level is mapped r/o and can only be updated via the fixmap API, this cannot
be trivially reverted by poking writable memory.
This does not address a known exploit or vulnerability, but it applies the
principle of least privilege in a way that does not result in any space
or runtime overhead.
Cc: maz@kernel.org
Cc: catalin.marinas@arm.com
Cc: will@kernel.org
Cc: mark.rutland@arm.com
Cc: anshuman.khandual@arm.com
Cc: qperret@google.com
Cc: kernel-team@android.com
Ard Biesheuvel (2):
arm64: mm: add missing P4D definitions and use them consistently
arm64: mm: use XN table mapping attributes for the linear region
arch/arm64/include/asm/pgtable-hwdef.h | 12 ++++++++
arch/arm64/mm/mmu.c | 31 ++++++++++++++------
2 files changed, 34 insertions(+), 9 deletions(-)
--
2.20.1
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next reply other threads:[~2021-03-04 17:15 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-04 17:11 Ard Biesheuvel [this message]
2021-03-04 17:11 ` [PATCH 1/2] arm64: mm: add missing P4D definitions and use them consistently Ard Biesheuvel
2021-03-04 17:39 ` Mark Rutland
2021-03-08 9:06 ` Anshuman Khandual
2021-03-08 9:07 ` Ard Biesheuvel
2021-03-04 17:11 ` [PATCH 2/2] arm64: mm: use XN table mapping attributes for the linear region Ard Biesheuvel
2021-03-04 17:39 ` Mark Rutland
2021-03-05 8:13 ` Ard Biesheuvel
2021-03-05 19:06 ` Catalin Marinas
2021-03-05 19:17 ` Ard Biesheuvel
2021-03-05 20:37 ` Catalin Marinas
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