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

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Date:   Sun, 4 Jun 2017 17:06:11 +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 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.

Thanks,

	tglx