On Tue, Jul 21, 2026 at 01:42:56AM +0000, Deep Shah wrote: > testptp's -f option stores the requested adjustment as an int ppb and > converts it to scaled ppm, so it cannot express the 64-bit scaled-ppm > values needed to overflow scaled_ppm_to_ppb() and bypass the max_adj > check enforced by ptp_clock_adjtime(). > > Add a small test that crafts struct timex.freq directly and verifies that > an overflowing frequency adjustment is rejected with -ERANGE. The test > skips when no frequency-adjustable PTP device is available. > > Signed-off-by: Deep Shah <[email protected]>
... > diff --git a/tools/testing/selftests/ptp/ptp_freq_overflow.c > b/tools/testing/selftests/ptp/ptp_freq_overflow.c ... > + /* > + * (1 + 147573952589676412) * 125 == 2^64 + 9, which overflows s64 in > + * scaled_ppm_to_ppb() and wraps the result to a ppb of 0. A kernel > + * that does not detect the overflow lets this absurd frequency past > + * the max_adj check; a fixed kernel rejects it with -ERANGE. > + */ > + tx.modes = ADJ_FREQUENCY; > +#if __SIZEOF_LONG__ >= 8 > + tx.freq = 147573952589676412L; > +#endif Thanks for the update here. But unfortunately sashiko.dev still flags a problem. "Will this preprocessor condition cause a false test failure on 32-bit architectures configured with 64-bit time types (such as x32 or y2038 compliant systems)? "On those architectures, the runtime check earlier in main() passes because sizeof(tx.freq) is 8. However, __SIZEOF_LONG__ evaluates to 4, which causes the preprocessor to skip the assignment of tx.freq. "This leaves tx.freq as 0, allowing clock_adjtime() to successfully apply a zero adjustment instead of rejecting the call with -ERANGE, which triggers a test failure. I wonder if dropping the #if/#endif would address that concern.
