Messages in this thread Patch in this message | | | From | Mathieu Desnoyers <> | Subject | [PATCH 1/1] Fix: trace sched switch start/stop refcount racy updates | Date | Sat, 17 Aug 2019 10:12:08 -0400 |
| |
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).
[ Compile-tested only. I suspect it might fix the following syzbot report:
syzbot+774fddf07b7ab29a1e55@syzkaller.appspotmail.com ]
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> 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> --- 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: -- 2.11.0
| |