From: Steven Rostedt (Google) Date: Wed, 23 Nov 2022 21:43:23 +0000 (-0500) Subject: tracing: Fix race where histograms can be called before the event X-Git-Tag: v6.1-rc8~28^2~2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=ef38c79a522b660f7f71d45dad2d6244bc741841;p=thirdparty%2Fkernel%2Flinux.git tracing: Fix race where histograms can be called before the event 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 Cc: stable@vger.kernel.org Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events") Reported-by: Masami Hiramatsu (Google) Acked-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) --- diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 087c19548049e..1c82478e8dffe 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) {