Sashiko recommended some additional checks to prevent null pointer access. Check for revoked states inside perf_event_read_local(), as the pmu event may have already been freed at this point. Add a null check inside __perf_event_read_cpu() as well before accessing the pmu ptr.
Cc: Dapeng Mi <[email protected]> Signed-off-by: Vinay Belgaumkar <[email protected]> --- kernel/events/core.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index f19d27ac411d..bb90034a2054 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4788,14 +4788,19 @@ static inline const struct cpumask *perf_scope_cpu_topology_cpumask(unsigned int static int __perf_event_read_cpu(struct perf_event *event, int event_cpu) { + struct pmu *pmu = READ_ONCE(event->pmu); int local_cpu = smp_processor_id(); u16 local_pkg, event_pkg; if ((unsigned)event_cpu >= nr_cpu_ids) return event_cpu; + if (!pmu) + return -ENODEV; + if (event->group_caps & PERF_EV_CAP_READ_SCOPE) { - const struct cpumask *cpumask = perf_scope_cpu_topology_cpumask(event->pmu->scope, event_cpu); + const struct cpumask *cpumask = perf_scope_cpu_topology_cpumask(pmu->scope, + event_cpu); if (cpumask && cpumask_test_cpu(local_cpu, cpumask)) return local_cpu; @@ -4917,6 +4922,11 @@ int perf_event_read_local(struct perf_event *event, u64 *value, goto out; } + if (READ_ONCE(event->state) <= PERF_EVENT_STATE_REVOKED) { + ret = -ENODEV; + goto out; + } + /* * Get the event CPU numbers, and adjust them to local if the event is * a per-package event that can be read locally -- 2.38.1
