diff mbox series

[for-linus,4/6] tracing: Fix race where histograms can be called before the event

Message ID 20221124144824.035022085@goodmis.org
State New
Headers
Series tracing: Fixes for 6.1 |

Commit Message

Steven Rostedt Nov. 24, 2022, 2:47 p.m. UTC 
  From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

commit 94eedf3dded5 ("tracing: Fix race where eprobes can be called before
the event") fixed an issue where if an event is soft disabled, and the
trigger is being added, there's a small window where the event sees that
there's a trigger but does not see that it requires reading the event yet,
and then calls the trigger with the record == NULL.

This could be solved with adding memory barriers in the hot path, or to
make sure that all the triggers requiring a record check for NULL. The
latter was chosen.

Commit 94eedf3dded5 set the eprobe trigger handle to check for NULL, but
the same needs to be done with histograms.

Link: https://lore.kernel.org/linux-trace-kernel/20221118211809.701d40c0f8a757b0df3c025a@kernel.org/
Link: https://lore.kernel.org/linux-trace-kernel/20221123164323.03450c3a@gandalf.local.home

Cc: Tom Zanussi <zanussi@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
Reported-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 kernel/trace/trace_events_hist.c | 3 +++
 1 file changed, 3 insertions(+)
diff mbox series

Patch

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index 087c19548049..1c82478e8dff 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -5143,6 +5143,9 @@  static void event_hist_trigger(struct event_trigger_data *data,
 	void *key = NULL;
 	unsigned int i;
 
+	if (unlikely(!rbe))
+		return;
+
 	memset(compound_key, 0, hist_data->key_size);
 
 	for_each_hist_key_field(i, hist_data) {