linux-kernel - Re: [PATCH 1/2] KVM: arm64: Fix off-by-one in range_is

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Date:   Thu, 29 Jul 2021 17:52:49 +0100
From:   Quentin Perret <qperret@...gle.com>
To:     David Brazdil <dbrazdil@...gle.com>
Cc:     kvmarm@...ts.cs.columbia.edu, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: arm64: Fix off-by-one in range_is_memory

On Wednesday 28 Jul 2021 at 15:32:31 (+0000), David Brazdil wrote:
> Hyp checks whether an address range only covers RAM by checking the
> start/endpoints against a list of memblock_region structs. However,
> the endpoint here is exclusive but internally is treated as inclusive.
> Fix the off-by-one error that caused valid address ranges to be
> rejected.
> 
> Cc: Quentin Perret <qperret@...gle.com>
> Fixes: 90134ac9cabb6 ("KVM: arm64: Protect the .hyp sections from the host")
> Signed-off-by: David Brazdil <dbrazdil@...gle.com>
> ---
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index d938ce95d3bd..a6ce991b1467 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -193,7 +193,7 @@ static bool range_is_memory(u64 start, u64 end)
>  {
>  	struct kvm_mem_range r1, r2;
>  
> -	if (!find_mem_range(start, &r1) || !find_mem_range(end, &r2))
> +	if (!find_mem_range(start, &r1) || !find_mem_range(end - 1, &r2))
>  		return false;
>  	if (r1.start != r2.start)
>  		return false;

Looks good to me:

Reviewed-by: Quentin Perret <qperret@...gle.com>

Thanks,
Quentin