Re: [PATCH] time: verify time values in adjtimex ADJ_SETOFFSET to avoid overflow

Thomas Gleixner
2015-12-06T09:07:56Z

On Sat, 5 Dec 2015, Sasha Levin wrote:
> On 12/05/2015 12:10 PM, Thomas Gleixner wrote:
> > On Thu, 3 Dec 2015, Sasha Levin wrote:
> >
> >> Make sure the tv_usec makes sense. We might multiply them later which can
> >> cause an overflow and undefined behavior.
> >>
> >> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
> >> ---
> >> kernel/time/timekeeping.c | 4 ++++
> >> 1 file changed, 4 insertions(+)
> >>
> >> diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
> >> index d563c19..aa3c1c2 100644
> >> --- a/kernel/time/timekeeping.c
> >> +++ b/kernel/time/timekeeping.c
> >> @@ -1987,6 +1987,10 @@ int do_adjtimex(struct timex *txc)
> >>
> >> if (txc->modes & ADJ_SETOFFSET) {
> >> struct timespec delta;
> >> +
> >> + if (txc->time.tv_usec >= USEC_PER_SEC || txc->time.tv_usec <= -USEC_PER_SEC)
> >> + return -EINVAL;
> >
> > That's not a canonical timeval. timeval_valid() is what you want to
> > check it. Or has adjtimex some magic exception here?
>
> Nope, it looks like timeval_valid() is indeed what I've needed to use.
>
> Is there a reason ntp_validate_timex() doesn't do timeval_valid() too
> for at least the ADJ_SETOFFSET case? If not, I'll add it in.

Not that I know, but John might have some opinion on that.

Thanks,

tglx