Messages in this thread | | | Date | Wed, 26 Nov 2014 11:12:26 -0800 | Subject | Re: [RFC 2/2] kvm: eventfd: detect integer overflow using check_*_overflow | From | Linus Torvalds <> |
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On Wed, Nov 26, 2014 at 11:06 AM, Sasha Levin <sasha.levin@oracle.com> wrote: > > I'm pretty sure that this is something GCC will warn you about in the > compilation stage.
It does? I've never seen it, but maybe it's a new thing.
The gcc signedness warnings have historically been so wretched that it's just sad, and they have to be turned off.
> kernel/time/ntp.c:process_adjtimex_modes(): > > if (txc->modes & ADJ_FREQUENCY) { > time_freq = txc->freq * PPM_SCALE; <=== Undefined overflow > time_freq = min(time_freq, MAXFREQ_SCALED); > time_freq = max(time_freq, -MAXFREQ_SCALED); > /* update pps_freq */ > pps_set_freq(time_freq); > } > > The multiplication is between signed integers, and it overflows (user triggerable).
Well, we check that the end result - overflowed or not - is in a sane range. So this might fall under the heading of "user gets what he asks for".
Linus
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