On 11/26/2014 02:12 PM, Linus Torvalds wrote:
>> 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".
I guess, though it wouldn't be clear to the user why it's broken since he
passed a
seemingly valid looking value for txc->freq.
Thanks,
Sasha
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