Re: [PATCH] perf/core: Allow list_del during perf_event_overflow()

[sashiko-bot@kernel.org]

> A PMU might use perf_sched_cb_inc() and perf_sched_cb_dec()
> interface to get the PMU call back function pmu::sched_task
> invoked at schedule in and schedule out. This is achieved
> by walking along the list anchored by sched_cb_list.
> 
> The following scenario might lead to a list corruption.
> 
>    perf_pmu_sched_task()
>       for_each_list_entry(..., &sched_cb_list)
>       +--> __perf_pmu_sched_task()
>            +--> event->pmu->sched_task())
>                 +--> PMU_push_sample()
>                      +--> perf_event_overflow()
>                           +--> __perf_event_overflow()
>                                +--> pmu->stop()
>                                     +--> perf_sched_cb_dec()
>                                          remove entry from sched_cb_list
>                                          while list node in use.
> 
> This happens when ioctl(fd, PERF_EVENT_IOC_REFRESH, xxx) has been
> invoked and perf_event::event_limit hits zero.
> 
> Prevent the list corruption and convert for_each_list_entry()
> to for_each_list_entry_safe().
> 
> Cc: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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