xen/arm: mm: Only increment mfn when valid in xen_pt_update

Currently, the MFN will be incremented even if it is invalid. This will
result to have a valid MFN after the first iteration.

While this is not a major problem today, this will be in the future if
the code expect an invalid MFN at every iteration.

Such behavior is prevented by avoiding to increment an invalid MFN.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 085a99b97657de16d2ef847790dde98db6837b5c..23e9565ddc280669819a1aa71d1f3323eac4f295 100644 (file)
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -1024,11 +1024,14 @@ static int xen_pt_update(enum xenmap_operation op,
 
     spin_lock(&xen_pt_lock);
 
-    for(; addr < addr_end; addr += PAGE_SIZE, mfn = mfn_add(mfn, 1))
+    for( ; addr < addr_end; addr += PAGE_SIZE )
     {
         rc = xen_pt_update_entry(op, addr, mfn, flags);
         if ( rc )
             break;
+
+        if ( !mfn_eq(mfn, INVALID_MFN) )
+            mfn = mfn_add(mfn, 1);
     }
 
     /*