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Subject: [PATCH] vfio/type1: Use follow_pte()
From:   Alex Williamson <alex.williamson@redhat.com>
To:     alex.williamson@redhat.com
Cc:     cohuck@redhat.com, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, pbonzini@redhat.com, jgg@nvidia.com,
        peterx@redhat.com
Date:   Fri, 12 Feb 2021 12:01:50 -0700
Message-ID: <161315649533.7249.11715726297751446001.stgit@gimli.home>
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Precedence: bulk

follow_pfn() doesn't make sure that we're using the correct page
protections, get the pte with follow_pte() so that we can test
protections and get the pfn from the pte.

Fixes: 5cbf3264bc71 ("vfio/type1: Fix VA->PA translation for PFNMAP VMAs in vaddr_get_pfn()")
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/vfio/vfio_iommu_type1.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index ec9fd95a138b..90715413c3d9 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -463,9 +463,11 @@ static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
 			    unsigned long vaddr, unsigned long *pfn,
 			    bool write_fault)
 {
+	pte_t *ptep;
+	spinlock_t *ptl;
 	int ret;
 
-	ret = follow_pfn(vma, vaddr, pfn);
+	ret = follow_pte(vma->vm_mm, vaddr, NULL, &ptep, NULL, &ptl);
 	if (ret) {
 		bool unlocked = false;
 
@@ -479,9 +481,17 @@ static int follow_fault_pfn(struct vm_area_struct *vma, struct mm_struct *mm,
 		if (ret)
 			return ret;
 
-		ret = follow_pfn(vma, vaddr, pfn);
+		ret = follow_pte(vma->vm_mm, vaddr, NULL, &ptep, NULL, &ptl);
+		if (ret)
+			return ret;
 	}
 
+	if (write_fault && !pte_write(*ptep))
+		ret = -EFAULT;
+	else
+		*pfn = pte_pfn(*ptep);
+
+	pte_unmap_unlock(ptep, ptl);
 	return ret;
 }