From: Catalin Marinas <catalin.marinas@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
Amit Daniel Kachhap <amit.kachhap@arm.com>,
linux-arm-kernel@lists.infradead.org,
Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH] arm64: sync kernel APIAKey when installing
Date: Tue, 21 Apr 2020 14:31:54 +0100 [thread overview]
Message-ID: <20200421133153.GB12076@gaia> (raw)
In-Reply-To: <20200421123150.GA17875@willie-the-truck>
On Tue, Apr 21, 2020 at 01:31:51PM +0100, Will Deacon wrote:
> On Tue, Apr 21, 2020 at 01:10:14PM +0100, Mark Rutland wrote:
> > A direct write to a APxxKey_EL1 register requires a context
> > synchronization event to ensure that indirect reads made by subsequent
> > instructions (e.g. AUTIASP, PACIASP) observe the new value.
> >
> > When we initialize the boot task's APIAKey in boot_init_stack_canary()
> > via ptrauth_keys_switch_kernel() we miss the necessary ISB, and so there
> > is a window where instructions are not guaranteed to use the new APIAKey
> > value. This has been observed to result in boot-time crashes where
> > PACIASP and AUTIASP within a function used a mixture of the old and new
> > key values.
> >
> > Fix this by having ptrauth_keys_switch_kernel() synchronize the new key
> > value with an ISB. At the same time, __ptrauth_key_install() is renamed
> > to __ptrauth_key_install_nosync() so that it is obvious that this
> > performs no synchronization itself.
> >
> > Fixes: 28321582334c261c ("arm64: initialize ptrauth keys for kernel booting task")
> > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
> > Reported-by: Will Deacon <will@kernel.org>
> > Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
> > Cc: Catalin Marinas <catalin.marinas@arm.com>
> > Cc: Marc Zyngier <maz@kernel.org>
> > ---
> > arch/arm64/include/asm/pointer_auth.h | 9 ++++++---
> > 1 file changed, 6 insertions(+), 3 deletions(-)
>
> Tested-by: Will Deacon <will@kernel.org>
>
> Catalin -- please can you queue this for -rc3?
I will. Thanks.
--
Catalin
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prev parent reply other threads:[~2020-04-21 13:32 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-21 12:10 [PATCH] arm64: sync kernel APIAKey when installing Mark Rutland
2020-04-21 12:31 ` Will Deacon
2020-04-21 13:31 ` Catalin Marinas [this message]
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