linux-kernel - Re: [PATCH] time: verify time values in adjtimex ADJ

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Date:	Sun, 6 Dec 2015 10:07:01 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Sasha Levin <sasha.levin@...cle.com>
cc:	john.stultz@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] time: verify time values in adjtimex ADJ_SETOFFSET to
 avoid overflow

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@...cle.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
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