Re: [PATCH] arm64/mm: Fix ttbr0 values stored in struct thread_info for software-pan
From: Catalin Marinas <catalin.marinas@arm.com>
Date: 2021-06-15 14:26:04
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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> _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel