| From 64ae572bc7d0060429e40e1c8d803ce5eb31a0d6 Mon Sep 17 00:00:00 2001 |
| From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| Date: Sat, 17 Aug 2019 10:12:08 -0400 |
| Subject: tracing: Fix sched switch start/stop refcount racy updates |
| |
| From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| |
| 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@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: 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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| 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: |
