Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

tracing: Fix hist trigger timestamps for buffered events

Syzkaller triggered a WARN_ON_ONCE(!nest) warning:

WARNING: kernel/trace/ring_buffer.c:821 at ring_buffer_event_time_stamp Call trace: ring_buffer_event_time_stamp hist_field_timestamp hist_fn_call event_hist_trigger event_triggers_call __event_trigger_test_discard trace_event_buffer_commit do_trace_event_raw_event_sched_switch trace_event_raw_event_sched_switch

The warning is probabilistically reproducible and is related to syzkaller executing the following commands:

echo 'prev_pid == 999999' > events/sched/sched_switch/filter echo 'hist:keys=common_timestamp' > events/sched/sched_switch/trigger

The specific triggering process is as follows:

CPU 0 CPU 1 (context switching) (echo 'hist:keys=common_timestamp' > \ events/sched/sched_switch/trigger) do_trace_event_raw_event_##call trace_event_buffer_lock_reserve if (!tr->no_filter_buffering_ref && trace_file->flags & EVENT_FILE_FL_FILTERED) return entry; // return directly event_hist_trigger_parse hist_register_trigger tracing_set_filter_buffering(file->tr, true…