linux-kernel - Re: [BUG] Null pointer deref with hrtimer_try_to

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Date:	Sat, 20 Dec 2008 22:04:01 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Eric Sesterhenn <snakebyte@....de>,
	LKML <linux-kernel@...r.kernel.org>,
	John Stultz <johnstul@...ibm.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [BUG] Null pointer deref with hrtimer_try_to_cancel()

On 12/20, Thomas Gleixner wrote:
>
> +static int no_timer_create(struct k_itimer *new_timer)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
>  /*
>   * Return nonzero if we know a priori this clockid_t value is bogus.
>   */
> @@ -248,6 +253,7 @@ static __init int init_posix_timers(void)
>  		.clock_getres = hrtimer_get_res,
>  		.clock_get = posix_get_monotonic_raw,
>  		.clock_set = do_posix_clock_nosettime,
> +		.timer_create = no_timer_create,

Agreed, this patch is better than mine (and thanks for your
explanation about CLOCK_MONOTONIC_RAW).

I am not sure about -EOPNOTSUPP. To clarify, I do not claim this
is wrong, I just do not know.

But please note that sys_timer_create() does:

	if (invalid_clockid(which_clock))
		return -EINVAL;

And ltp's timer_create04.c expects timer_create(MAX_CLOCKS == 4)
returns -EINVAL.

Oleg.

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