[PATCH v2 6/7] vfio/cdx: keep logical vm_pgoff in MMIO region mmap

[Abdifatah Suruur <suruurism@gmail.com>]

vfio_cdx_mmap_mmio() overwrites vma->vm_pgoff with the physical frame
number of the MMIO region and passes it to io_remap_pfn_range().  The
VMA is inserted into the device file's mapping->i_mmap interval tree
keyed by vm_pgoff, which VFIO expects to be the logical file offset:
the core links every device mmap to the device inode's i_mapping
precisely so that unmap_mapping_range() can revoke all mappings
associated with a device (see vfio_device_cdev_open()).

With a raw PFN in vm_pgoff the interval tree entry lands in the wrong
coordinate space and unmap_mapping_range() cannot find the VMA,
leaving stale MMIO mappings behind any revocation attempt.  Keep
vm_pgoff in the logical VFIO offset space, as vfio-pci does, and pass
the physical PFN to io_remap_pfn_range() explicitly.

This is defensive hygiene: none of vfio-platform, vfio/fsl-mc and
vfio/cdx call unmap_mapping_range() today, so no reachable
stale-mapping issue exists.  Keeping vm_pgoff logical preserves the
VFIO core contract for any future revocation path.

Signed-off-by: Abdifatah Suruur <suruurism@gmail.com>
---
 drivers/vfio/cdx/main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/cdx/main.c b/drivers/vfio/cdx/main.c
index 28386fdb01f2e..ea55b7767672c 100644
--- a/drivers/vfio/cdx/main.c
+++ b/drivers/vfio/cdx/main.c
@@ -254,10 +254,10 @@ static int vfio_cdx_mmap_mmio(struct vfio_cdx_region region,
 	if (base + size > region.size)
 		return -EINVAL;
 
-	vma->vm_pgoff = (region.addr >> PAGE_SHIFT) + pgoff;
 	vma->vm_page_prot = pgprot_device(vma->vm_page_prot);
 
-	return io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
+	return io_remap_pfn_range(vma, vma->vm_start,
+				  (region.addr >> PAGE_SHIFT) + pgoff,
 				  size, vma->vm_page_prot);
 }
 
-- 
2.53.0