[PATCH] vfio/type1: Use follow_pte()

[Alex Williamson]

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.william...@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;
 }