linux-kernel - Re: [PATCH v2] arm64: mops: Do not dereference src reg for a set operation

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Message-ID: <8df29f21-fe0d-4784-84cc-4e20ce19c4bd@arm.com>
Date: Wed, 26 Mar 2025 17:32:00 +0000
From: Kristina Martšenko <kristina.martsenko@....com>
To: Keir Fraser <keirf@...gle.com>
Cc: Catalin Marinas <catalin.marinas@....com>,
 Mark Rutland <mark.rutland@....com>, Will Deacon <will@...nel.org>,
 stable@...r.kernel.org, Marc Zyngier <maz@...nel.org>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64: mops: Do not dereference src reg for a set
 operation

On 26/03/2025 11:04, Keir Fraser wrote:
> The source register is not used for SET* and reading it can result in
> a UBSAN out-of-bounds array access error, specifically when the MOPS
> exception is taken from a SET* sequence with XZR (reg 31) as the
> source. Architecturally this is the only case where a src/dst/size
> field in the ESR can be reported as 31.
> 
> Prior to 2de451a329cf662b the code in do_el0_mops() was benign as the
> use of pt_regs_read_reg() prevented the out-of-bounds access.
> 
> Fixes: 2de451a329cf662b ("KVM: arm64: Add handler for MOPS exceptions")
> Cc: Kristina Martsenko <kristina.martsenko@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: stable@...r.kernel.org
> Reviewed-by: Marc Zyngier <maz@...nel.org>
> Signed-off-by: Keir Fraser <keirf@...gle.com>

FWIW,

Reviewed-by: Kristina Martšenko <kristina.martsenko@....com>

Thanks,
Kristina