Re: [PATCH 1/2] KVM: arm64: vgic: check redist region is not above the VM IPA size

[Alexandru Elisei <alexandru.elisei@arm.com>]

Hi Ricardo,

On 9/8/21 10:03 PM, Ricardo Koller wrote:
> Extend vgic_v3_check_base() to verify that the redistributor regions
> don't go above the VM-specified IPA size (phys_size). This can happen
> when using the legacy KVM_VGIC_V3_ADDR_TYPE_REDIST attribute with:
>
>   base + size > phys_size AND base < phys_size
>
> vgic_v3_check_base() is used to check the redist regions bases when
> setting them (with the vcpus added so far) and when attempting the first
> vcpu-run.
>
> Signed-off-by: Ricardo Koller <ricarkol@google.com>
> ---
>  arch/arm64/kvm/vgic/vgic-v3.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
> index 66004f61cd83..5afd9f6f68f6 100644
> --- a/arch/arm64/kvm/vgic/vgic-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-v3.c
> @@ -512,6 +512,10 @@ bool vgic_v3_check_base(struct kvm *kvm)
>  		if (rdreg->base + vgic_v3_rd_region_size(kvm, rdreg) <
>  			rdreg->base)
>  			return false;
> +
> +		if (rdreg->base + vgic_v3_rd_region_size(kvm, rdreg) >
> +			kvm_phys_size(kvm))
> +			return false;

Looks to me like this same check (and the overflow one before it) is done when
adding a new Redistributor region in kvm_vgic_addr() -> vgic_v3_set_redist_base()
-> vgic_v3_alloc_redist_region() -> vgic_check_ioaddr(). As far as I can tell,
kvm_vgic_addr() handles both ways of setting the Redistributor address.

Without this patch, did you manage to set a base address such that base + size >
kvm_phys_size()?

Thanks,

Alex

>  	}
>  
>  	if (IS_VGIC_ADDR_UNDEF(d->vgic_dist_base))
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