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From: Catalin Marinas <catalin.marinas@arm.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	James Morse <james.morse@arm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64/mm: Fix ttbr0 values stored in struct thread_info for software-pan
Date: Tue, 15 Jun 2021 15:25:39 +0100	[thread overview]
Message-ID: <20210615142539.GJ26027@arm.com> (raw)
In-Reply-To: <1623749578-11231-1-git-send-email-anshuman.khandual@arm.com>

On Tue, Jun 15, 2021 at 03:02:58PM +0530, Anshuman Khandual wrote:
> When using CONFIG_ARM64_SW_TTBR0_PAN, a task's thread_info::ttbr0 must be
> the TTBR0_EL1 value used to run userspace. With 52-bit PAs, the PA must be
> packed into the TTBR using phys_to_ttbr(), but we forget to do this in some
> of the SW PAN code. Thus, if the value is installed into TTBR0_EL1 (as may
> happen in the uaccess routines), this could result in UNPREDICTABLE
> behaviour.
> 
> Since hardware with 52-bit PA support almost certainly has HW PAN, which
> will be used in preference, this shouldn't be a practical issue, but let's
> fix this for consistency.

I'm ok with fixing this for consistency. We should never hit those paths
unless someone built hardware with 52-bit PA (8.2) but without PAN (8.1)
and it would not be architecture compliant.

I'll leave it with Will for 5.14, it's no a fix that needs urgent
queuing.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	Will Deacon <will@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	James Morse <james.morse@arm.com>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] arm64/mm: Fix ttbr0 values stored in struct thread_info for software-pan
Date: Tue, 15 Jun 2021 15:25:39 +0100	[thread overview]
Message-ID: <20210615142539.GJ26027@arm.com> (raw)
In-Reply-To: <1623749578-11231-1-git-send-email-anshuman.khandual@arm.com>

On Tue, Jun 15, 2021 at 03:02:58PM +0530, Anshuman Khandual wrote:
> When using CONFIG_ARM64_SW_TTBR0_PAN, a task's thread_info::ttbr0 must be
> the TTBR0_EL1 value used to run userspace. With 52-bit PAs, the PA must be
> packed into the TTBR using phys_to_ttbr(), but we forget to do this in some
> of the SW PAN code. Thus, if the value is installed into TTBR0_EL1 (as may
> happen in the uaccess routines), this could result in UNPREDICTABLE
> behaviour.
> 
> Since hardware with 52-bit PA support almost certainly has HW PAN, which
> will be used in preference, this shouldn't be a practical issue, but let's
> fix this for consistency.

I'm ok with fixing this for consistency. We should never hit those paths
unless someone built hardware with 52-bit PA (8.2) but without PAN (8.1)
and it would not be architecture compliant.

I'll leave it with Will for 5.14, it's no a fix that needs urgent
queuing.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

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  reply	other threads:[~2021-06-15 14:26 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-15  9:32 [PATCH] arm64/mm: Fix ttbr0 values stored in struct thread_info for software-pan Anshuman Khandual
2021-06-15  9:32 ` Anshuman Khandual
2021-06-15 14:25 ` Catalin Marinas [this message]
2021-06-15 14:25   ` Catalin Marinas
2021-06-15 14:26   ` Will Deacon
2021-06-15 14:26     ` Will Deacon
2021-06-15 19:18 ` Will Deacon
2021-06-15 19:18   ` Will Deacon

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