Re: [PATCH v2] posix-cpu-timers: fix nanosleep task_struct leak

[Oleg Nesterov <oleg@redhat.com>]

Thanks Stanislaw.

I think this patch is fine.

On 02/07, Stanislaw Gruszka wrote:
>
> In do_cpu_nanosleep() we do posic_cpu_timer_create(), but forgot
> corresponding posix_cpu_timer_del() what lead to task_struct leak.
> 
> Reported-and-tested-by: Tommi Rantala <tt.rantala@gmail.com>
> Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
> ---
> v1 -> v2: add comments
> 
>  kernel/posix-cpu-timers.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
> index a278cad..942ca27 100644
> --- a/kernel/posix-cpu-timers.c
> +++ b/kernel/posix-cpu-timers.c
> @@ -1401,8 +1401,10 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
>  		while (!signal_pending(current)) {
>  			if (timer.it.cpu.expires.sched == 0) {
>  				/*
> -				 * Our timer fired and was reset.
> +				 * Our timer fired and was reset, below
> +				 * deletion can not fail.
>  				 */
> +				posix_cpu_timer_del(&timer);
>  				spin_unlock_irq(&timer.it_lock);
>  				return 0;
>  			}
> @@ -1420,9 +1422,26 @@ static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
>  		 * We were interrupted by a signal.
>  		 */
>  		sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
> -		posix_cpu_timer_set(&timer, 0, &zero_it, it);
> +		error = posix_cpu_timer_set(&timer, 0, &zero_it, it);
> +		if (!error) {
> +			/*
> +			 * Timer is now unarmed, deletion can not fail.
> +			 */
> +			posix_cpu_timer_del(&timer);
> +		}
>  		spin_unlock_irq(&timer.it_lock);
>  
> +		while (error == TIMER_RETRY) {
> +			/*
> +			 * We need to handle case when timer was or is in the
> +			 * middle of firing. In other cases we already freed
> +			 * resources.
> +			 */
> +			spin_lock_irq(&timer.it_lock);
> +			error = posix_cpu_timer_del(&timer);
> +			spin_unlock_irq(&timer.it_lock);
> +		}
> +
>  		if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
>  			/*
>  			 * It actually did fire already.
> -- 
> 1.7.11.7
>