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SubjectRe: [PATCH v2] vfio/type1: Use follow_pte()
On Tue, 16 Feb 2021 15:49:34 -0700
Alex Williamson <alex.williamson@redhat.com> wrote:

> 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@nvidia.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.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;
> }
>
>

Adding the following to resolve 32-bit build:

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 8a777250764a..ed03f3fcb07e 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -24,6 +24,7 @@
#include <linux/compat.h>
#include <linux/device.h>
#include <linux/fs.h>
+#include <linux/highmem.h>
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/mm.h>
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