linux-kernel - [PATCH v2] vfio/type1: Use follow

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Message-ID: <161351571186.15573.5602248562129684350.stgit@gimli.home>
Date:   Tue, 16 Feb 2021 15:49:34 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     alex.williamson@...hat.com
Cc:     cohuck@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, pbonzini@...hat.com, jgg@...dia.com,
        peterx@...hat.com
Subject: [PATCH v2] vfio/type1: Use follow_pte()

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()")
Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
Reviewed-by: Cornelia Huck <cohuck@...hat.com>
Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
---

v2: Update to current follow_pte() API, add Reviews

 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..ae4fd2295c95 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, &ptep, &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, &ptep, &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;
 }