linux-kernel - Re: [PATCH] KVM: arm64: Fix the upper limit of the walker range

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Message-ID: <Z4Z8yRPGwvqHpzRs@google.com>
Date: Tue, 14 Jan 2025 15:03:37 +0000
From: Sebastian Ene <sebastianene@...gle.com>
To: Marc Zyngier <maz@...nel.org>
Cc: catalin.marinas@....com, joey.gouly@....com, kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	oliver.upton@...ux.dev, suzuki.poulose@....com, will@...nel.org,
	yuzenghui@...wei.com
Subject: Re: [PATCH] KVM: arm64: Fix the upper limit of the walker range

On Tue, Jan 14, 2025 at 02:55:17PM +0000, Marc Zyngier wrote:
> On Tue, 14 Jan 2025 14:50:51 +0000,
> Sebastian Ene <sebastianene@...gle.com> wrote:
> > 
> > Prevent the walker from running into weeds when walking an
> > entire address range.
> > 
> > Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
> > ---
> >  arch/arm64/kvm/hyp/pgtable.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> > index 40bd55966..2ffb5571e 100644
> > --- a/arch/arm64/kvm/hyp/pgtable.c
> > +++ b/arch/arm64/kvm/hyp/pgtable.c
> > @@ -260,7 +260,7 @@ static int _kvm_pgtable_walk(struct kvm_pgtable *pgt, struct kvm_pgtable_walk_da
> >  {
> >  	u32 idx;
> >  	int ret = 0;
> > -	u64 limit = BIT(pgt->ia_bits);
> > +	u64 limit = BIT(pgt->ia_bits) - 1;
> >  
> >  	if (data->addr > limit || data->end > limit)
> >  		return -ERANGE;
> 
> Huh, nice catch. I guess this deserves a
> 
> Fixes: b1e57de62cfb4 ("KVM: arm64: Add stand-alone page-table walker infrastructure")
> Cc: stable@...r.kernel.org
> 
> right?
> 
> 	M.

Hi Marc,

Thanks for the prompt review. Adding the missing bits now and re-spinnig
v2.

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

Cheers
Sebastian