x86: add an extra check when validating a huge pv L2 entry

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@novell.com>
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 579d40b9bc2fea0e1fa73220645e3c8275509792..336883508ff053ea8cce277a42677d826c1a5585 100644 (file)
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -844,14 +844,16 @@ get_page_from_l2e(
         int writeable = !!(l2e_get_flags(l2e) & _PAGE_RW);
   
         do {
-            rc = get_data_page(mfn_to_page(m), d, writeable);
-            if ( unlikely(!rc) )
+            if ( !mfn_valid(m) ||
+                 !get_data_page(mfn_to_page(m), d, writeable) )
             {
                 while ( m-- > mfn )
                     put_data_page(mfn_to_page(m), writeable);
                 return -EINVAL;
             }
         } while ( m++ < (mfn + (L1_PAGETABLE_ENTRIES-1)) );
+
+        rc = 1;
     }
 
     return rc;