Re: [Xen-devel] [PATCH for-4.13 v2] xen/arm: Don't use _end in is_xen_fixed_mfn()

[Jan Beulich <jbeulich@xxxxxxxx>]

On 16.10.2019 12:53, Julien Grall wrote:
> virt_to_maddr() is using the hardware page-table walk instructions to
> translate a virtual address to physical address. The function should
> only be called on virtual address mapped.
> 
> _end points past the end of Xen binary and may not be mapped when the
> binary size is page-aligned. This means virt_to_maddr() will not be able
> to do the translation and therefore crash Xen.
> 
> Note there is also an off-by-one issue in this code, but the panic will
> trump that.
> 
> Both issues can be fixed by using _end - 1 in the check.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
> Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
> 
> ---
> 
> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Cc: Julien Grall <julien@xxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Tim Deegan <tim@xxxxxxx>
> Cc: Wei Liu <wl@xxxxxxx>
> 
> x86 seems to be affected by the off-by-one issue. Jan, Andrew?

Indeed. I'm in the process of making a patch.

Jan

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