[Xen-changelog] [xen staging] xen/arm: mm: Only increment mfn when valid in xen_pt_update

[patchbot@xxxxxxx]

commit 4a53f2c7f9b978f3bb45a8e8861d483c790cbb35
Author:     Julien Grall <julien.grall@xxxxxxx>
AuthorDate: Fri Mar 22 17:22:43 2019 +0000
Commit:     Julien Grall <julien.grall@xxxxxxx>
CommitDate: Fri Jun 14 18:35:46 2019 +0100

    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@xxxxxxx>
    Reviewed-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
    Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
---
 xen/arch/arm/mm.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index 085a99b976..23e9565ddc 100644
--- 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);
     }
 
     /*
--
generated by git-patchbot for /home/xen/git/xen.git#staging

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