[PATCH 4.4 30/34] xen/gntdev: Fix off-by-one error when unmapping with holes

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ross Lagerwall <ross.lagerw...@citrix.com>


[ Upstream commit 951a010233625b77cde3430b4b8785a9a22968d1 ]

If the requested range has a hole, the calculation of the number of
pages to unmap is off by one. Fix it.

Signed-off-by: Ross Lagerwall <ross.lagerw...@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/xen/gntdev.c |    4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -378,10 +378,8 @@ static int unmap_grant_pages(struct gran
                }
                range = 0;
                while (range < pages) {
-                       if (map->unmap_ops[offset+range].handle == -1) {
-                               range--;
+                       if (map->unmap_ops[offset+range].handle == -1)
                                break;
-                       }
                        range++;
                }
                err = __unmap_grant_pages(map, offset, range);