[PATCH 2/2] xen/gntdev: Fix partial gntdev_mmap() cleanup

[Ross Lagerwall <ross.lagerwall@citrix.com>]

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@citrix.com>
---
 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)
 out_unlock_put:
 	mutex_unlock(&priv->lock);
 out_put_map:
-	if (use_ptemod)
+	if (use_ptemod) {
 		map->vma = NULL;
+		unmap_grant_pages(map, 0, map->count);
+	}
 	gntdev_put_map(priv, map);
 	return err;
 }
-- 
2.9.5