File 23943-xenpaging_clear_page_content_after_evict.patch of Package xen

changeset:   23943:1185ae04b5aa
user:        Olaf Hering <olaf@aepfle.de>
date:        Tue Oct 11 10:46:28 2011 +0100
files:       tools/xenpaging/xenpaging.c xen/arch/x86/mm/p2m.c
description:
xenpaging: clear page content after evict

If the guest happens to read from the gfn while xenpaging is in the process of
evicting the page, the guest may read zeros instead of actual data.
Also if eviction fails the page content will be corrupted and xenpaging wont
attempt to restore the page.

Remove page scrubbing from pager and do it after successful eviction.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>
Acked-by: Tim Deegan <tim@xen.org>
Committed-by: Tim Deegan <tim@xen.org>


---
 tools/xenpaging/xenpaging.c |    3 ---
 xen/arch/x86/mm/p2m.c       |    3 +++
 2 files changed, 3 insertions(+), 3 deletions(-)

Index: xen-4.1.2-testing/tools/xenpaging/xenpaging.c
===================================================================
--- xen-4.1.2-testing.orig/tools/xenpaging/xenpaging.c
+++ xen-4.1.2-testing/tools/xenpaging/xenpaging.c
@@ -455,9 +455,6 @@ static int xenpaging_evict_page(xenpagin
         goto out;
     }
 
-    /* Clear page */
-    memset(page, 0, PAGE_SIZE);
-
     munmap(page, PAGE_SIZE);
 
     /* Tell Xen to evict page */
Index: xen-4.1.2-testing/xen/arch/x86/mm/p2m.c
===================================================================
--- xen-4.1.2-testing.orig/xen/arch/x86/mm/p2m.c
+++ xen-4.1.2-testing/xen/arch/x86/mm/p2m.c
@@ -2916,6 +2916,9 @@ int p2m_mem_paging_evict(struct p2m_doma
     set_p2m_entry(p2m, gfn, _mfn(PAGING_MFN), 0, p2m_ram_paged, a);
     audit_p2m(p2m, 1);
 
+    /* Clear content before returning the page to Xen */
+    scrub_one_page(page);
+
     /* Put the page back so it gets freed */
     put_page(page);