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KVM: Forbid the use of tagged userspace addresses for memslots

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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>
This commit is contained in:
Marc Zyngier 2021-01-21 12:08:15 +00:00 committed by Greg Kroah-Hartman
parent e895a39a2b
commit 256a0040c6
2 changed files with 4 additions and 0 deletions
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3
Documentation/virt/kvm/api.rst
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@ -1264,6 +1264,9 @@ field userspace_addr, which must point at user addressable memory for
the entire memory slot size. Any object may back this memory, including the entire memory slot size. Any object may back this memory, including
anonymous memory, ordinary files, and hugetlbfs. 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 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 be identical. This allows large pages in the guest to be backed by large
pages in the host. pages in the host.

1
virt/kvm/kvm_main.c
View File

@ -1289,6 +1289,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
return -EINVAL; return -EINVAL;
/* We can read the guest memory with __xxx_user() later on. */ /* We can read the guest memory with __xxx_user() later on. */
if ((mem->userspace_addr & (PAGE_SIZE - 1)) || if ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
(mem->userspace_addr != untagged_addr(mem->userspace_addr)) ||
!access_ok((void __user *)(unsigned long)mem->userspace_addr, !access_ok((void __user *)(unsigned long)mem->userspace_addr,
mem->memory_size)) mem->memory_size))
return -EINVAL; return -EINVAL;