From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> commit 64ae572bc7d0060429e40e1c8d803ce5eb31a0d6 upstream. Reading the sched_cmdline_ref and sched_tgid_ref initial state within tracing_start_sched_switch without holding the sched_register_mutex is racy against concurrent updates, which can lead to tracepoint probes being registered more than once (and thus trigger warnings within tracepoint.c). [ May be the fix for this bug ] Link: https://lore.kernel.org/r/000000000000ab6f84056c786b93@xxxxxxxxxx Link: http://lkml.kernel.org/r/20190817141208.15226-1-mathieu.desnoyers@xxxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx CC: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> CC: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CC: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CC: Paul E. McKenney <paulmck@xxxxxxxxxxxxx> Reported-by: syzbot+774fddf07b7ab29a1e55@xxxxxxxxxxxxxxxxxxxxxxxxx Fixes: d914ba37d7145 ("tracing: Add support for recording tgid of tasks") Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/trace/trace_sched_switch.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) --- a/kernel/trace/trace_sched_switch.c +++ b/kernel/trace/trace_sched_switch.c @@ -89,8 +89,10 @@ static void tracing_sched_unregister(voi static void tracing_start_sched_switch(int ops) { - bool sched_register = (!sched_cmdline_ref && !sched_tgid_ref); + bool sched_register; + mutex_lock(&sched_register_mutex); + sched_register = (!sched_cmdline_ref && !sched_tgid_ref); switch (ops) { case RECORD_CMDLINE:
