From patchwork Wed Nov 23 21:43:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13054365 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89503C4332F for ; Wed, 23 Nov 2022 21:43:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232341AbiKWVn2 (ORCPT ); Wed, 23 Nov 2022 16:43:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230009AbiKWVn2 (ORCPT ); Wed, 23 Nov 2022 16:43:28 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B18DC689C; Wed, 23 Nov 2022 13:43:26 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2972861F36; Wed, 23 Nov 2022 21:43:26 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id EF86BC433D6; Wed, 23 Nov 2022 21:43:24 +0000 (UTC) Date: Wed, 23 Nov 2022 16:43:23 -0500 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Tom Zanussi Subject: [PATCH] tracing: Fix race where histograms can be called before the event Message-ID: <20221123164323.03450c3a@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: "Steven Rostedt (Google)" 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/ Cc: stable@vger.kernel.org Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events") Reported-by: Masami Hiramatsu (Google) Signed-off-by: Steven Rostedt (Google) Acked-by: Masami Hiramatsu (Google) --- kernel/trace/trace_events_hist.c | 3 +++ 1 file changed, 3 insertions(+) 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) {