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? thanks -john -- 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/
