arm/arm64: KVM: Ensure memslots are within KVM_PHYS_SIZE

When creating or moving a memslot, make sure the IPA space is within the
addressable range of the guest.  Otherwise, user space can create too
large a memslot and KVM would try to access potentially unallocated page
table entries when inserting entries in the Stage-2 page tables.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index ee142edcca84ab8152e2a125724aebf6ccabc0fd..8c40829d4a524ce4c85e27db25e215fbb7d62d1d 100644 (file)
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1003,6 +1003,9 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu, struct kvm_run *run)
                goto out_unlock;
        }
 
+       /* Userspace should not be able to register out-of-bounds IPAs */
+       VM_BUG_ON(fault_ipa >= KVM_PHYS_SIZE);
+
        ret = user_mem_abort(vcpu, fault_ipa, memslot, hva, fault_status);
        if (ret == 0)
                ret = 1;
@@ -1228,6 +1231,14 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
        if (change != KVM_MR_CREATE && change != KVM_MR_MOVE)
                return 0;
 
+       /*
+        * Prevent userspace from creating a memory region outside of the IPA
+        * space addressable by the KVM guest IPA space.
+        */
+       if (memslot->base_gfn + memslot->npages >=
+           (KVM_PHYS_SIZE >> PAGE_SHIFT))
+               return -EFAULT;
+
        /*
         * A memory region could potentially cover multiple VMAs, and any holes
         * between them, so iterate over all of them to find out if we can map