[PATCH][next] afs: fix integer overflow when shifting 1 more than 32 places
Colin Ian King
colin.king at canonical.com
Wed Apr 11 07:17:59 PDT 2018
On 11/04/18 15:10, David Howells wrote:
> Colin Ian King <colin.king at canonical.com> wrote:
>
>>>> - mask = (1 << nr_slots) - 1;
>>>> + mask = (1ULL << nr_slots) - 1;
>>>
>>> nr_slots cannot be larger than 9, so what I wrote is actually fine and is
>>> more efficient on a 32-bit machine.
>>
>> ok, sorry about the noise.
>
> It would be possible to cast the value to u64 before assigning it, I suppose.
> Would that help? E.g.:
>
> mask = (u64)((1 << nr_slots) - 1);
>
> It looks a bit odd, though, since the cast is made implicitly anyway.
I'm not sure that actually helps, 1 << nr_slots is still evaluating as
a 32 bit value, so that final cast does not may any difference. Anyhow,
since nr_slots is less than 32 then keeping it the way it was is fine.
>
> David
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