Re: [PATCH v2 1/2] KVM: arm64: vgic: check redist region is not above the VM IPA size

[Marc Zyngier <maz@kernel.org>]

Hi Ricardo,

On Fri, 10 Sep 2021 01:49:18 +0100,
Ricardo Koller <ricarkol@google.com> wrote:
> 
> Verify that the redistributor regions do not extend beyond the
> VM-specified IPA size (phys_size). This can happen when using
> KVM_VGIC_V3_ADDR_TYPE_REDIST or KVM_VGIC_V3_ADDR_TYPE_REDIST_REGIONS
> with:
> 
>   base + size > phys_size AND base < phys_size
> 
> Add the missing check into vgic_v3_alloc_redist_region() which is called
> when setting the regions, and into vgic_v3_check_base() which is called
> when attempting the first vcpu-run. The vcpu-run check does not apply to
> KVM_VGIC_V3_ADDR_TYPE_REDIST_REGIONS because the regions size is known
> before the first vcpu-run. Finally, this patch also enables some extra
> tests in vgic_v3_alloc_redist_region() by calculating "size" early for
> the legacy redist api.
> 
> Signed-off-by: Ricardo Koller <ricarkol@google.com>
> ---
>  arch/arm64/kvm/vgic/vgic-mmio-v3.c | 7 ++++++-
>  arch/arm64/kvm/vgic/vgic-v3.c      | 4 ++++
>  2 files changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> index a09cdc0b953c..055671bede85 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> @@ -796,7 +796,9 @@ static int vgic_v3_alloc_redist_region(struct kvm *kvm, uint32_t index,
>  	struct vgic_dist *d = &kvm->arch.vgic;
>  	struct vgic_redist_region *rdreg;
>  	struct list_head *rd_regions = &d->rd_regions;
> -	size_t size = count * KVM_VGIC_V3_REDIST_SIZE;
> +	int nr_vcpus = atomic_read(&kvm->online_vcpus);
> +	size_t size = count ? count * KVM_VGIC_V3_REDIST_SIZE :
> +			nr_vcpus * KVM_VGIC_V3_REDIST_SIZE;
>  	int ret;
>  
>  	/* cross the end of memory ? */
> @@ -834,6 +836,9 @@ static int vgic_v3_alloc_redist_region(struct kvm *kvm, uint32_t index,
>  	if (vgic_v3_rdist_overlap(kvm, base, size))
>  		return -EINVAL;
>  
> +	if (base + size > kvm_phys_size(kvm))
> +		return -E2BIG;
> +
>  	rdreg = kzalloc(sizeof(*rdreg), GFP_KERNEL);
>  	if (!rdreg)
>  		return -ENOMEM;
> 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;
>  	}
>  
>  	if (IS_VGIC_ADDR_UNDEF(d->vgic_dist_base))

How about vgic-v2? From what I can see, the placement of the
distributor and CPU interface should be subjected to the same checks
(see vgic_v2_check_base()).

Thanks,

	M.

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