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perf/core: Allow list_del during perf_event_overflow()

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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().

Fixes: bd27568117 ("perf: Rewrite core context handling")
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260908105637.627004-1-tmricht@linux.ibm.com
This commit is contained in:
Thomas Richter
2026-09-10 10:22:50 +02:00
committed by Peter Zijlstra
parent df2908090c
commit 59e63416f5
1 changed files with 2 additions and 2 deletions
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kernel/events/core.c
+2 -2
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@@ -3925,13 +3925,13 @@ static void perf_pmu_sched_task(struct task_struct *prev,
bool sched_in)
{
struct perf_cpu_context *cpuctx = this_cpu_ptr(&perf_cpu_context);
struct perf_cpu_pmu_context *cpc;
struct perf_cpu_pmu_context *cpc, *cpc2;
/* cpuctx->task_ctx will be handled in perf_event_context_sched_in/out */
if (prev == next || cpuctx->task_ctx)
return;
list_for_each_entry(cpc, this_cpu_ptr(&sched_cb_list), sched_cb_entry)
list_for_each_entry_safe(cpc, cpc2, this_cpu_ptr(&sched_cb_list), sched_cb_entry)
__perf_pmu_sched_task(cpc, sched_in ? next : prev, sched_in);
}