[Xen-devel] [PATCH] x86: add an extra check when validating a huge pv L2 entry

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

While get_page_and_type_from_pagenr() (through get_page_from_pagenr())
does the needed mfn_valid() check, get_data_page() doesn't and, it
being passed a struct page_info pointer, really expects it's caller(s)
to do.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- 2009-08-18.orig/xen/arch/x86/mm.c   2009-09-09 13:32:06.000000000 +0200
+++ 2009-08-18/xen/arch/x86/mm.c        2009-09-09 13:35:02.000000000 +0200
@@ -868,7 +868,10 @@ get_page_from_l2e(
         int writeable = !!(l2e_get_flags(l2e) & _PAGE_RW);
   
         do {
-            rc = get_data_page(mfn_to_page(m), d, writeable);
+            if ( mfn_valid(m) )
+                rc = get_data_page(mfn_to_page(m), d, writeable);
+            else
+                rc = -EINVAL;
             if ( unlikely(!rc) )
             {
                 while ( m-- > mfn )




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