On 12/07/2015 07:02 PM, John Stultz wrote: > On Thu, Dec 3, 2015 at 12:46 PM, Sasha Levin <sasha.le...@oracle.com> wrote: >> > We need to make sure that the offset is valid before manipulating it, >> > otherwise it might overflow on the multiplication. >> > >> > Signed-off-by: Sasha Levin <sasha.le...@oracle.com> >> > --- >> > kernel/time/ntp.c | 6 ++++-- >> > 1 file changed, 4 insertions(+), 2 deletions(-) >> > >> > diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c >> > index 149cc80..36616c3 100644 >> > --- a/kernel/time/ntp.c >> > +++ b/kernel/time/ntp.c >> > @@ -297,6 +297,9 @@ static void ntp_update_offset(long offset) >> > if (!(time_status & STA_PLL)) >> > return; >> > >> > + /* Make sure the multiplication below won't overflow */ >> > + offset = clamp(offset, -MAXPHASE, MAXPHASE); >> > + >> > if (!(time_status & STA_NANO)) >> > offset *= NSEC_PER_USEC; > So looking at this a bit closer, this bit looks sort of crazy since we > clam the offset, do the multiply and then do the exact same clamp. > > I'd much rather do a more logical clamp(offset, -USEC_PER_SEC, > USEC_PER_SEC), but only in the case where we do the multiply. > > Any objection to that?
Nope. Sounds right. Thanks, Sasha -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
