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Re: [Xen-devel] [PATCH 2/2] xen/gntdev: Fix partial gntdev_mmap() cleanup

On 01/09/2018 07:10 AM, Ross Lagerwall wrote:
When cleaning up after a partially successful gntdev_mmap(), unmap the
successfully mapped grant pages otherwise Xen will kill the domain if
in debug mode (Attempt to implicitly unmap a granted PTE) or Linux will
kill the process and emit "BUG: Bad page map in process" if Xen is in
release mode.

This is only needed when use_ptemod is true because gntdev_put_map()
will unmap grant pages itself when use_ptemod is false.

Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

although I wonder whether it may be possible to have gntdev_put_map() figure whether to unmap the pages if use_ptemod is set.

  drivers/xen/gntdev.c | 4 +++-
  1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index d3391a1..bd56653 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -1071,8 +1071,10 @@ static int gntdev_mmap(struct file *flip, struct 
vm_area_struct *vma)
-       if (use_ptemod)
+       if (use_ptemod) {
                map->vma = NULL;
+               unmap_grant_pages(map, 0, map->count);
+       }
        gntdev_put_map(priv, map);
        return err;

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