This is a note to let you know that I've just added the patch titled
tracing: Fix race where histograms can be called before the event
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tracing-fix-race-where-histograms-can-be-called-before-the-event.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From ef38c79a522b660f7f71d45dad2d6244bc741841 Mon Sep 17 00:00:00 2001
From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
Date: Wed, 23 Nov 2022 16:43:23 -0500
Subject: tracing: Fix race where histograms can be called before the event
From: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
commit ef38c79a522b660f7f71d45dad2d6244bc741841 upstream.
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@xxxxxxxxxx/
Link: https://lore.kernel.org/linux-trace-kernel/20221123164323.03450c3a@xxxxxxxxxxxxxxxxxx
Cc: Tom Zanussi <zanussi@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
Reported-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/trace/trace_events_hist.c | 3 +++
1 file changed, 3 insertions(+)
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -4677,6 +4677,9 @@ static void event_hist_trigger(struct ev
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) {
Patches currently in stable-queue which might be from rostedt@xxxxxxxxxxx are
queue-5.15/error-injection-add-prompt-for-function-error-injection.patch
queue-5.15/tracing-free-buffers-when-a-used-dynamic-event-is-removed.patch
queue-5.15/tracing-osnoise-fix-duration-type.patch
queue-5.15/tracing-fix-race-where-histograms-can-be-called-before-the-event.patch
