linux-kernel - [PATCH 5.4 21/61] KVM: Forbid the use of tagged userspace addresses for memslots

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Date:   Tue,  2 Feb 2021 14:37:59 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Marc Zyngier <maz@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 5.4 21/61] KVM: Forbid the use of tagged userspace addresses for memslots

From: Marc Zyngier <maz@...nel.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@...r.kernel.org
Reported-by: Rick Edgecombe <rick.p.edgecombe@...el.com>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Acked-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>


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

--- a/Documentation/virt/kvm/api.txt
+++ b/Documentation/virt/kvm/api.txt
@@ -1132,6 +1132,9 @@ 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
@@ -1017,6 +1017,7 @@ int __kvm_set_memory_region(struct kvm *
 	/* We can read the guest memory with __xxx_user() later on. */
 	if ((id < KVM_USER_MEM_SLOTS) &&
 	    ((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)))
 		goto out;