powerpc/iommu: Avoid undefined right shift in iommu_range_alloc()

[Michael Ellerman]

On Tue, 2017-08-08 at 07:06:32 UTC, Michael Ellerman wrote:
> In iommu_range_alloc() we generate a mask by right shifting ~0,
> however if the specified alignment is 0 then we right shift by 64,
> which is undefined. UBSAN tells us so:
> 
>   UBSAN: Undefined behaviour in ../arch/powerpc/kernel/iommu.c:193:35
>   shift exponent 64 is too large for 64-bit type 'long unsigned int'
> 
> We can avoid it by instead generating the mask with:
> 
>   align_mask = (1ull << align_order) - 1;
> 
> That will also generate an undefined shift if align_order is 64 or
> greater, but that shouldn't be a problem for a while.
> 
> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>

Applied to powerpc next.

https://git.kernel.org/powerpc/c/63b85621d9aa6bdc410f01b22f7821

cheers