linux-kernel - Re: [PATCH] KVM: arm64: Fix memory check in host_stage2_set_owner

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Message-ID: <86ikmegmw9.wl-maz@kernel.org>
Date: Tue, 06 May 2025 09:32:22 +0100
From: Marc Zyngier <maz@...nel.org>
To: Mostafa Saleh <smostafa@...gle.com>
Cc: linux-kernel@...r.kernel.org,
	kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	oliver.upton@...ux.dev,
	joey.gouly@....com,
	suzuki.poulose@....com,
	yuzenghui@...wei.com,
	catalin.marinas@....com,
	will@...nel.org,
	qperret@...gle.com
Subject: Re: [PATCH] KVM: arm64: Fix memory check in host_stage2_set_owner_locked()

On Thu, 01 May 2025 17:24:50 +0100,
Mostafa Saleh <smostafa@...gle.com> wrote:
> 
> I found this simple bug while preparing some patches for pKVM.
> AFAICT, it should be harmless (besides crashing the kernel if it
> was misbehaving)
> 
> Fixes: e94a7dea2972 ("KVM: arm64: Move host page ownership tracking to the hyp vmemmap")
> Signed-off-by: Mostafa Saleh <smostafa@...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 2a5284f749b4..e80f3ebd3e2a 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -503,7 +503,7 @@ int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id)
>  {
>  	int ret;
>  
> -	if (!addr_is_memory(addr))
> +	if (!range_is_memory(addr, addr + size))
>  		return -EPERM;
>  
>  	ret = host_stage2_try(kvm_pgtable_stage2_set_owner, &host_mmu.pgt,

I vaguely seem to remember that there was an assumption around
addr/size representing a single page, and therefore addr_is_memory()
was doing the right thing.

Has this assumption changed? Or is this only a figment of my imagination?

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.