From: Juergen Gross <jgross@suse.com>
Date: Wed, 25 Oct 2017 17:08:07 +0200
Patch-mainline: v4.14-rc7
Git-commit: 298d275d4d9bea3524ff4bc76678c140611d8a8d
References: bnc#1065600
Subject: [PATCH] xen/gntdev: avoid out of bounds access in case of partial
 gntdev_mmap()

In case gntdev_mmap() succeeds only partially in mapping grant pages
it will leave some vital information uninitialized needed later for
cleanup. This will lead to an out of bounds array access when unmapping
the already mapped pages.

So just initialize the data needed for unmapping the pages a little bit
earlier.

Cc: <stable@vger.kernel.org>
Reported-by: Arthur Borsboom <arthurborsboom@gmail.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
---
 drivers/xen/gntdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
index 82360594fa8e..57efbd3b053b 100644
--- a/drivers/xen/gntdev.c
+++ b/drivers/xen/gntdev.c
@@ -1024,6 +1024,7 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 	mutex_unlock(&priv->lock);
 
 	if (use_ptemod) {
+		map->pages_vm_start = vma->vm_start;
 		err = apply_to_page_range(vma->vm_mm, vma->vm_start,
 					  vma->vm_end - vma->vm_start,
 					  find_grant_ptes, map);
@@ -1061,7 +1062,6 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma)
 					    set_grant_ptes_as_special, NULL);
 		}
 #endif
-		map->pages_vm_start = vma->vm_start;
 	}
 
 	return 0;
-- 
2.16.4