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    Subject[PATCH 5.4 223/340] vfio/type1: Use follow_pte()
    Date
    From: Alex Williamson <alex.williamson@redhat.com>

    [ Upstream commit 07956b6269d3ed05d854233d5bb776dca91751dd ]

    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>
    Reviewed-by: Peter Xu <peterx@redhat.com>
    Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/vfio/vfio_iommu_type1.c | 15 +++++++++++++--
    1 file changed, 13 insertions(+), 2 deletions(-)

    diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
    index 9cbe058a530f0..6b1e8cba17984 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>
    @@ -339,9 +340,11 @@ 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;

    @@ -355,9 +358,17 @@ 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;
    }

    --
    2.27.0


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