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

On Mon, Sep 20, 2021 at 01:30:40PM +0100, Marc Zyngier wrote:

Hi Ricardo,

On Fri, 10 Sep 2021 01:49:18 +0100,
Ricardo Koller [off-list ref] wrote:

quoted

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 <redacted>
---
 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()).

Yes, gic-v2 has the same problem. Alexandru first mentioned it here:

  https://lore.kernel.org/kvmarm/5eb41efd-2ff2-d25b-5801-f4a56457a09f@arm.com/ (local)

I'm now working on the next version of the patch which applies to gic-v2
as well.

Thanks,
Ricardo

Thanks,

	M.

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

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