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

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Date:	Sat, 5 Dec 2015 18:10:13 +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 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?

Thanks,

	tglx
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