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

[Greg Kroah-Hartman]

From: Marc Zyngier <maz@xxxxxxxxxx>

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@xxxxxxxxxxxxxxx
Reported-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 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;