From: Mathieu Desnoyers mathieu.desnoyers@efficios.com

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@google.com

Link: http://lkml.kernel.org/r/20190817141208.15226-1-mathieu.desnoyers@efficios.c...

Cc: stable@vger.kernel.org CC: Steven Rostedt (VMware) rostedt@goodmis.org CC: Joel Fernandes (Google) joel@joelfernandes.org CC: Peter Zijlstra peterz@infradead.org CC: Thomas Gleixner tglx@linutronix.de CC: Paul E. McKenney paulmck@linux.ibm.com Reported-by: syzbot+774fddf07b7ab29a1e55@syzkaller.appspotmail.com Fixes: d914ba37d7145 ("tracing: Add support for recording tgid of tasks") Signed-off-by: Mathieu Desnoyers mathieu.desnoyers@efficios.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org --- kernel/trace/trace_sched_switch.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c index e288168661e1..e304196d7c28 100644 --- a/kernel/trace/trace_sched_switch.c +++ b/kernel/trace/trace_sched_switch.c @@ -89,8 +89,10 @@ static void tracing_sched_unregister(void)

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: