[PATCH 5.10 046/142] KVM: Forbid the use of tagged userspace addresses for memslots

Greg Kroah-Hartman
2021-02-02T13:58:44Z

From: Marc Zyngier <maz@kernel.org>

commit 139bc8a6146d92822c866cf2fd410159c56b3648 upstream.

The use of a tagged address could be pretty confusing for the
whole memslot infrastructure as well as the MMU notifiers.

Forbid it altogether, as it never quite worked the first place.

Cc: stable@vger.kernel.org
Reported-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
Documentation/virt/kvm/api.rst | 3 +++
virt/kvm/kvm_main.c | 1 +
2 files changed, 4 insertions(+)

--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -1264,6 +1264,9 @@ field userspace_addr, which must point a
the entire memory slot size. Any object may back this memory, including
anonymous memory, ordinary files, and hugetlbfs.

+On architectures that support a form of address tagging, userspace_addr must
+be an untagged address.
+
It is recommended that the lower 21 bits of guest_phys_addr and userspace_addr
be identical. This allows large pages in the guest to be backed by large
pages in the host.
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1289,6 +1289,7 @@ int __kvm_set_memory_region(struct kvm *
return -EINVAL;
/* We can read the guest memory with __xxx_user() later on. */
if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
+ (mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
!access_ok((void __user *)(unsigned long)mem->userspace_addr,
mem->memory_size))
return -EINVAL;