Re: [Xen-devel] [PATCH MM-PART2 RESEND v2 18/19] xen/arm: mm: Check start is always before end in {destroy, modify}_xen_mappings

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 14 May 2019, Julien Grall wrote:
> The two helpers {destroy, modify}_xen_mappings don't check that the
> start is always before the end. This should never happen but if it
> happens, it will result to unexpected behavior.
> 
> Catch such issues earlier on by adding an ASSERT in destroy_xen_mappings
> and modify_xen_mappings.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Reviewed-by: Andrii Anisov <andrii_anisov@xxxxxxxx>

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>     Changes in v2:
>         - Add Andrii's reviewed-by
> ---
>  xen/arch/arm/mm.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index eacc1647e0..b408de7c75 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -1077,11 +1077,13 @@ int populate_pt_range(unsigned long virt, unsigned 
> long nr_mfns)
>  
>  int destroy_xen_mappings(unsigned long v, unsigned long e)
>  {
> +    ASSERT(v <= e);
>      return create_xen_entries(REMOVE, v, INVALID_MFN, (e - v) >> PAGE_SHIFT, 
> 0);
>  }
>  
>  int modify_xen_mappings(unsigned long s, unsigned long e, unsigned int flags)
>  {
> +    ASSERT(s <= e);
>      return create_xen_entries(MODIFY, s, INVALID_MFN, (e - s) >> PAGE_SHIFT,
>                                flags);
>  }
> -- 
> 2.11.0
> 

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