Re: [PATCH] crypto_mem_not_equal: add constant-time equality testing of memory regions

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* James Yonan:

> + * Constant-time equality testing of memory regions.
> + * Returns 0 when data is equal, non-zero otherwise.
> + * Fast path if size == 16.
> + */
> +noinline unsigned long crypto_mem_not_equal(const void *a, const void *b, size_t size)

I think this should really return unsigned or int, to reduce the risk
that the upper bytes are truncated because the caller uses an
inappropriate type, resulting in a bogus zero result.  Reducing the
value to 0/1 probably doesn't hurt performance too much.  It also
doesn't encode any information about the location of the difference in
the result value, which helps if that ever leaks.
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