Commit 64ae572b authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Steven Rostedt (VMware)

tracing: Fix sched switch start/stop refcount racy updates

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.com

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: d914ba37 ("tracing: Add support for recording tgid of tasks")
Signed-off-by: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent 5c3469cb
......@@ -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:
......
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