[v3] sprof: check pread size and offset for overflow

[Collin Funk]

DJ Delorie <dj@redhat.com> writes:

> Add a bit of descriptive paranoia to the values we read from
> the ELF headers and use to access data.
>
> ---- 8< ----
>
> v2: rewrote check math
> v3: add overflow checks; avoid side effects in macros
>
> diff --git a/elf/sprof.c b/elf/sprof.c
> index c82c7c9db6..e9d2a66a4f 100644

Looks good. Thanks!

Reviewed-by: Collin Funk <collin.funk1@gmail.com>

Collin