[PATCH] iommu/amd: Clear memory encryption mask from physical address

[PATCH] iommu/amd: Clear memory encryption mask from physical address

[Singh, Brijesh]

Boris Ostrovsky reported a memory leak with device passthrough when SME
is active.

The VFIO driver uses iommu_iova_to_phys() to get the physical address for
an iova. This physical address is later passed into vfio_unmap_unpin() to
unpin the memory. The vfio_unmap_unpin() uses pfn_valid() before unpinning
the memory. The pfn_valid() check was failing because encryption mask was
part of the physical address returned. This resulted in the memory not
being unpinned and therefore leaked after the guest terminates.

The memory encryption mask must be cleared from the physical address in
iommu_iova_to_phys().

Fixes: 2543a786aa25 ("iommu/amd: Allow the AMD IOMMU to work with memory encryption")
Reported-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: <iommu@lists.linux-foundation.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: <stable@vger.kernel.org> # 4.14+
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 drivers/iommu/amd_iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 73e47d9..bee0dfb 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -3069,7 +3069,7 @@ static phys_addr_t amd_iommu_iova_to_phys(struct iommu_domain *dom,
 		return 0;
 
 	offset_mask = pte_pgsize - 1;
-	__pte	    = *pte & PM_ADDR_MASK;
+	__pte	    = __sme_clr(*pte & PM_ADDR_MASK);
 
 	return (__pte & ~offset_mask) | (iova & offset_mask);
 }
-- 
2.7.4

Re: [PATCH] iommu/amd: Clear memory encryption mask from physical address

[Joerg Roedel]

On Thu, Oct 04, 2018 at 09:40:23PM +0000, Singh, Brijesh wrote:
> Boris Ostrovsky reported a memory leak with device passthrough when SME
> is active.
> 
> The VFIO driver uses iommu_iova_to_phys() to get the physical address for
> an iova. This physical address is later passed into vfio_unmap_unpin() to
> unpin the memory. The vfio_unmap_unpin() uses pfn_valid() before unpinning
> the memory. The pfn_valid() check was failing because encryption mask was
> part of the physical address returned. This resulted in the memory not
> being unpinned and therefore leaked after the guest terminates.
> 
> The memory encryption mask must be cleared from the physical address in
> iommu_iova_to_phys().

Merged and on its way upstream, thanks Brijesh.