[v2] sprof: check pread size and offset for overflow

[Collin Funk]

DJ Delorie <dj@redhat.com> writes:

> Collin Funk <collin.funk1@gmail.com> writes:
>> Generally, I prefer to avoid writing overflow checks manually since it
>
> Checking for overflow is NOT one of the things I'm worried about.  It's
> not one of the things I'm expecting or checking for.
>
> I'm checking that all the values are in the range [0..filesize].

Right, you mentioned that in another mail. But I did not address it, my
apologies.

I think that we should check for overflows in this case. I could
construct an ELF file where the following expression overflows:

    (ehdr->e_shnum * sizeof (ElfW (Shdr)) + ehdr->e_shoff

Even though a real ELF file would almost certainly not cause this, I
think it is better to throw a meaningful error instead of continuing
with an integer that has wrapped around, or undefined behavior in the
case they are casted to signed integers like your patch.

Collin