bpf: Fix deadlock between rcu_tasks_trace and event_mutex.

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix deadlock between rcu_tasks_trace and event_mutex. Fix the following deadlock: CPU A _free_event() perf_kprobe_destroy() mutex_lock(&event_mutex) perf_trace_event_unreg() synchronize_rcu_tasks_trace() There are several paths where _free_event() grabs event_mutex and calls sync_rcu_tasks_trace. Above is one such case. CPU B bpf_prog_test_run_syscall() rcu_read_lock_trace() bpf_prog_run_pin_on_cpu() bpf_prog_load() bpf_tracing_func_proto() trace_set_clr_event() mutex_lock(&event_mutex) Delegate trace_set_clr_event() to workqueue to avoid such lock dependency.

References

• https://git.kernel.org/stable/c/45286680b385f2592db3003554872388dee66d68
• https://git.kernel.org/stable/c/4580f4e0ebdf8dc8d506ae926b88510395a0c1d1