Re: [PATCH] fs/resctrl: Fix use-after-free in resctrl_offline_mon_domain()

[Luck, Tony]

On Wed, May 06, 2026 at 11:24:30AM -0700, Reinette Chatre wrote:
> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
> index 02f87c4bc03c..cc8620ace7ed 100644
> --- a/fs/resctrl/rdtgroup.c
> +++ b/fs/resctrl/rdtgroup.c
> @@ -4539,8 +4539,19 @@ void resctrl_offline_cpu(unsigned int cpu)
>  	d = get_mon_domain_from_cpu(cpu, l3);
>  	if (d) {
>  		if (resctrl_is_mbm_enabled() && cpu == d->mbm_work_cpu) {
> -			cancel_delayed_work(&d->mbm_over);
> -			mbm_setup_overflow_handler(d, 0, cpu);
> +			if (cancel_delayed_work(&d->mbm_over)) {
> +				mbm_setup_overflow_handler(d, 0, cpu);

Per your comment[1] should this "0" also be MBM_OVERFLOW_INTERVAL?

Does the same "delay 0 is magic, ignore the cpu argument and run right away" apply?

> +			} else {
> +				/*
> +				 * Unable to schedule work on new CPU if it
> +				 * is currently running since the re-schedule
> +				 * will just force new work to run on
> +				 * current CPU. Mark domain's worker as
> +				 * needing to be rescheduled to be handled
> +				 * by worker itself.
> +				 */
> +				d->mbm_work_cpu = nr_cpu_ids;
> +			}
>  		}
>  		if (resctrl_is_mon_event_enabled(QOS_L3_OCCUP_EVENT_ID) &&
>  		    cpu == d->cqm_work_cpu && has_busy_rmid(d)) {

-Tony

Link: https://lore.kernel.org/all/389bd92c-47ba-46af-81cb-9b669533b1fe@xxxxxxxxx/ [1]