linux-kernel - Re: [RFC] ubsan: signed integer overflow in setitimer()

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Date:   Tue, 6 Jun 2017 09:43:41 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Xishi Qiu <qiuxishi@...wei.com>
cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>, fenghua.yu@...el.com,
        Peter Zijlstra <peterz@...radead.org>,
        John Stultz <john.stultz@...aro.org>
Subject: Re: [RFC] ubsan: signed integer overflow in setitimer()

On Tue, 6 Jun 2017, Xishi Qiu wrote:
> On 2017/6/4 23:06, Thomas Gleixner wrote:
> > On Thu, 1 Jun 2017, Xishi Qiu wrote:
> > 
> > Cc'ed John Stultz
> > 
> >> Hi, this is the test case, and then I got ubsan error
> >> (signed integer overflow) report, so the root cause is from
> >> user or kernel? Shall we change something in timeval_valid()?
> >>
> >>
> >> struct itimerval new_value;
> >> int ret;
> >>
> >> new_value.it_interval.tv_sec = 140673496649799L;
> >> new_value.it_interval.tv_usec = 6;
> >> new_value.it_value.tv_sec = 140673496649807L;
> >> new_value.it_value.tv_usec = 5;
> >>
> >> ret = setitimer(ITIMER_VIRTUAL, &new_value, NULL);
> >>
> >>
> >> [  533.326588] ================================================================================
> >> [  533.335346] UBSAN: Undefined behaviour in ./include/linux/time.h:239:27
> >> [  533.342155] signed integer overflow:
> >> [  533.345837] 140673496649807 * 1000000000 cannot be represented in type 'long int'
> >> [  533.422181]  set_cpu_itimer+0x49c/0x540
> >> [  533.442127]  do_setitimer+0xe1/0x540
> > 
> > We need a similar clamping of the conversion as we have for
> > timespec/val_to_ktime(). I'll have a look in the next days unless John
> > beats me to it.
> > 
> 
> Hi Thomas, anything new?

Let me spell it out to you again. I wrote on Sunday late night:

    "I'll have a look in the next days ...."

Do you really think I need a reminder after 24 hours?

Thanks,

	tglx