On Wed, Apr 15, 2020 at 01:23:24PM +0200, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
The patch below does not apply to the 5.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b8fdef311a0bd9223f10754f94fdcf1a594a3457 Mon Sep 17 00:00:00 2001
From: Mark Brown <broonie@xxxxxxxxxx>
Date: Tue, 31 Mar 2020 20:44:59 +0100
Subject: [PATCH] arm64: Always force a branch protection mode when the
compiler has one
Compilers with branch protection support can be configured to enable it by
default, it is likely that distributions will do this as part of deploying
branch protection system wide. As well as the slight overhead from having
some extra NOPs for unused branch protection features this can cause more
serious problems when the kernel is providing pointer authentication to
userspace but not built for pointer authentication itself. In that case our
switching of keys for userspace can affect the kernel unexpectedly, causing
pointer authentication instructions in the kernel to corrupt addresses.
To ensure that we get consistent and reliable behaviour always explicitly
initialise the branch protection mode, ensuring that the kernel is built
the same way regardless of the compiler defaults.
Fixes: 7503197562567 (arm64: add basic pointer authentication support)
Reported-by: Szabolcs Nagy <szabolcs.nagy@xxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
[catalin.marinas@xxxxxxx: remove Kconfig option in favour of Makefile check]
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
I don't think that this is needed anywhere without 74afda4016a7 ("arm64:
compile the kernel with ptrauth return address signing")?
--
Thanks,
Sasha
