xen: fix scrub_page()

Impact: fix guest kernel crash with CONFIG_XEN_SCRUB_PAGES=y

Jens noticed that scrub_page() has a buggy unmap of the wrong
thing. (virtual address instead of page)

Linus pointed out that the whole scrub_page() code is an unnecessary
reimplementation of clear_highpage() to begin with.

Just use clear_highpage() rather than reimplementing it poorly.

Reported-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 8 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index a0fb5eac407c..526c191e84ea 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -122,14 +122,7 @@ static struct timer_list balloon_timer;
 static void scrub_page(struct page *page)
 {
 #ifdef CONFIG_XEN_SCRUB_PAGES
-        if (PageHighMem(page)) {
-                void *v = kmap(page);
-                clear_page(v);
-                kunmap(v);
-        } else {
-                void *v = page_address(page);
-                clear_page(v);
-        }
+        clear_highpage(page);
 #endif
 }