From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Joel Fernandes <joel@joelfernandes.org>,
Peter Zijlstra <peterz@infradead.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E . McKenney" <paulmck@linux.ibm.com>
Subject: [PATCH 1/1] Fix: trace sched switch start/stop racy updates
Date: Fri, 16 Aug 2019 10:26:43 -0400 [thread overview]
Message-ID: <20190816142643.13758-1-mathieu.desnoyers@efficios.com> (raw)
In-Reply-To: <00000000000076ecf3059030d3f1@google.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).
Also, write and read to/from those variables should be done with
WRITE_ONCE() and READ_ONCE(), given that those are read within tracing
probes without holding the sched_register_mutex.
[ 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: Joel Fernandes (Google) <joel@joelfernandes.org>
CC: Peter Zijlstra <peterz@infradead.org>
CC: Steven Rostedt (VMware) <rostedt@goodmis.org>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Paul E. McKenney <paulmck@linux.ibm.com>
---
kernel/trace/trace_sched_switch.c | 32 ++++++++++++++++++++++----------
1 file changed, 22 insertions(+), 10 deletions(-)
diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c
index e288168661e1..902e8bf59aeb 100644
--- a/kernel/trace/trace_sched_switch.c
+++ b/kernel/trace/trace_sched_switch.c
@@ -26,8 +26,8 @@ probe_sched_switch(void *ignore, bool preempt,
{
int flags;
- flags = (RECORD_TGID * !!sched_tgid_ref) +
- (RECORD_CMDLINE * !!sched_cmdline_ref);
+ flags = (RECORD_TGID * !!READ_ONCE(sched_tgid_ref)) +
+ (RECORD_CMDLINE * !!READ_ONCE(sched_cmdline_ref));
if (!flags)
return;
@@ -39,8 +39,8 @@ probe_sched_wakeup(void *ignore, struct task_struct *wakee)
{
int flags;
- flags = (RECORD_TGID * !!sched_tgid_ref) +
- (RECORD_CMDLINE * !!sched_cmdline_ref);
+ flags = (RECORD_TGID * !!READ_ONCE(sched_tgid_ref)) +
+ (RECORD_CMDLINE * !!READ_ONCE(sched_cmdline_ref));
if (!flags)
return;
@@ -89,21 +89,28 @@ 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:
- sched_cmdline_ref++;
+ WRITE_ONCE(sched_cmdline_ref, sched_cmdline_ref + 1);
break;
case RECORD_TGID:
- sched_tgid_ref++;
+ WRITE_ONCE(sched_tgid_ref, sched_tgid_ref + 1);
break;
+
+ default:
+ WARN_ONCE(1, "Unsupported tracing op: %d", ops);
+ goto end;
}
- if (sched_register && (sched_cmdline_ref || sched_tgid_ref))
+ if (sched_register)
tracing_sched_register();
+end:
mutex_unlock(&sched_register_mutex);
}
@@ -113,16 +120,21 @@ static void tracing_stop_sched_switch(int ops)
switch (ops) {
case RECORD_CMDLINE:
- sched_cmdline_ref--;
+ WRITE_ONCE(sched_cmdline_ref, sched_cmdline_ref - 1);
break;
case RECORD_TGID:
- sched_tgid_ref--;
+ WRITE_ONCE(sched_tgid_ref, sched_tgid_ref - 1);
break;
+
+ default:
+ WARN_ONCE(1, "Unsupported tracing op: %d", ops);
+ goto end;
}
if (!sched_cmdline_ref && !sched_tgid_ref)
tracing_sched_unregister();
+end:
mutex_unlock(&sched_register_mutex);
}
--
2.11.0
next prev parent reply other threads:[~2019-08-16 14:26 UTC|newest]
Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-18 10:29 WARNING in tracepoint_probe_register_prio (3) syzbot
2019-08-16 0:11 ` syzbot
2019-08-16 14:26 ` Mathieu Desnoyers [this message]
2019-08-16 16:25 ` [PATCH 1/1] Fix: trace sched switch start/stop racy updates Steven Rostedt
2019-08-16 16:48 ` Valentin Schneider
2019-08-16 17:04 ` Steven Rostedt
2019-08-16 17:41 ` Mathieu Desnoyers
2019-08-16 19:18 ` Steven Rostedt
2019-08-16 19:19 ` Alan Stern
2019-08-16 20:44 ` Joel Fernandes
2019-08-16 20:49 ` Thomas Gleixner
2019-08-16 20:57 ` Joel Fernandes
2019-08-16 22:27 ` Valentin Schneider
2019-08-16 22:57 ` Linus Torvalds
2019-08-17 1:41 ` Mathieu Desnoyers
2019-08-17 4:52 ` Paul E. McKenney
2019-08-17 8:28 ` Linus Torvalds
2019-08-17 8:44 ` Linus Torvalds
2019-08-17 15:02 ` Mathieu Desnoyers
2019-08-17 20:03 ` Valentin Schneider
2019-08-17 23:00 ` Paul E. McKenney
2019-08-19 10:34 ` Valentin Schneider
2019-08-17 22:28 ` Paul E. McKenney
2019-08-20 14:01 ` Peter Zijlstra
2019-08-20 20:31 ` Paul E. McKenney
2019-08-20 20:39 ` Peter Zijlstra
2019-08-20 20:52 ` Paul E. McKenney
2019-08-16 21:04 ` Linus Torvalds
2019-08-17 1:36 ` Mathieu Desnoyers
2019-08-17 2:13 ` Steven Rostedt
2019-08-17 14:40 ` Mathieu Desnoyers
2019-08-17 15:26 ` Steven Rostedt
2019-08-17 15:55 ` Mathieu Desnoyers
2019-08-17 16:40 ` Steven Rostedt
2019-08-17 22:06 ` Paul E. McKenney
2019-08-17 8:08 ` Linus Torvalds
2019-08-20 13:56 ` Peter Zijlstra
2019-08-20 20:29 ` Paul E. McKenney
2019-08-21 10:32 ` Will Deacon
2019-08-21 13:23 ` Paul E. McKenney
2019-08-21 13:32 ` Will Deacon
2019-08-21 13:56 ` Paul E. McKenney
2019-08-21 16:22 ` Will Deacon
2019-08-21 15:33 ` Peter Zijlstra
2019-08-21 15:48 ` Mathieu Desnoyers
2019-08-21 16:14 ` Paul E. McKenney
2019-08-21 19:03 ` Joel Fernandes
2019-09-09 6:21 ` Herbert Xu
2019-08-16 20:49 ` Steven Rostedt
2019-08-16 20:59 ` Joel Fernandes
2019-08-17 1:25 ` Mathieu Desnoyers
2019-08-18 9:15 ` stable markup was " Pavel Machek
2019-08-16 17:19 ` Mathieu Desnoyers
2019-08-16 19:15 ` Steven Rostedt
2019-08-17 14:27 ` Mathieu Desnoyers
2019-08-17 15:42 ` Steven Rostedt
2019-08-17 15:53 ` Mathieu Desnoyers
2019-08-17 16:43 ` Steven Rostedt
2019-08-16 12:32 ` WARNING in tracepoint_probe_register_prio (3) syzbot
2019-08-16 12:41 ` Sebastian Andrzej Siewior
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