From nobody Wed Apr 8 11:45:06 2026 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 6B9E4C25B08 for ; Sun, 21 Aug 2022 00:09:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236767AbiHUAJQ (ORCPT ); Sat, 20 Aug 2022 20:09:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41094 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235643AbiHUAIg (ORCPT ); Sat, 20 Aug 2022 20:08:36 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4147912748; Sat, 20 Aug 2022 17:08:32 -0700 (PDT) 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 ams.source.kernel.org (Postfix) with ESMTPS id 81583B80B66; Sun, 21 Aug 2022 00:08:31 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4E382C43140; Sun, 21 Aug 2022 00:08:30 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.96) (envelope-from ) id 1oPYWD-005Dkz-06; Sat, 20 Aug 2022 20:08:45 -0400 Message-ID: <20220821000844.870621395@goodmis.org> User-Agent: quilt/0.66 Date: Sat, 20 Aug 2022 20:07:40 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , stable@vger.kernel.org, Krister Johansen , Jiri Olsa Subject: [for-linus][PATCH 03/10] tracing/perf: Fix double put of trace event when init fails References: <20220821000737.328590235@goodmis.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: "Steven Rostedt (Google)" If in perf_trace_event_init(), the perf_trace_event_open() fails, then it will call perf_trace_event_unreg() which will not only unregister the perf trace event, but will also call the put() function of the tp_event. The problem here is that the trace_event_try_get_ref() is called by the caller of perf_trace_event_init() and if perf_trace_event_init() returns a failure, it will then call trace_event_put(). But since the perf_trace_event_unreg() already called the trace_event_put() function, it triggers a WARN_ON(). WARNING: CPU: 1 PID: 30309 at kernel/trace/trace_dynevent.c:46 trace_event= _dyn_put_ref+0x15/0x20 If perf_trace_event_reg() does not call the trace_event_try_get_ref() then the perf_trace_event_unreg() should not be calling trace_event_put(). This breaks symmetry and causes bugs like these. Pull out the trace_event_put() from perf_trace_event_unreg() and call it in the locations that perf_trace_event_unreg() is called. This not only fixes this bug, but also brings back the proper symmetry of the reg/unreg vs get/put logic. Link: https://lore.kernel.org/all/cover.1660347763.git.kjlx@templeofstupid.= com/ Link: https://lkml.kernel.org/r/20220816192817.43d5e17f@gandalf.local.home Cc: stable@vger.kernel.org Fixes: 1d18538e6a092 ("tracing: Have dynamic events have a ref counter") Reported-by: Krister Johansen Reviewed-by: Krister Johansen Tested-by: Krister Johansen Acked-by: Jiri Olsa Signed-off-by: Steven Rostedt (Google) --- kernel/trace/trace_event_perf.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_per= f.c index a114549720d6..61e3a2620fa3 100644 --- a/kernel/trace/trace_event_perf.c +++ b/kernel/trace/trace_event_perf.c @@ -157,7 +157,7 @@ static void perf_trace_event_unreg(struct perf_event *p= _event) int i; =20 if (--tp_event->perf_refcount > 0) - goto out; + return; =20 tp_event->class->reg(tp_event, TRACE_REG_PERF_UNREGISTER, NULL); =20 @@ -176,8 +176,6 @@ static void perf_trace_event_unreg(struct perf_event *p= _event) perf_trace_buf[i] =3D NULL; } } -out: - trace_event_put_ref(tp_event); } =20 static int perf_trace_event_open(struct perf_event *p_event) @@ -241,6 +239,7 @@ void perf_trace_destroy(struct perf_event *p_event) mutex_lock(&event_mutex); perf_trace_event_close(p_event); perf_trace_event_unreg(p_event); + trace_event_put_ref(p_event->tp_event); mutex_unlock(&event_mutex); } =20 @@ -292,6 +291,7 @@ void perf_kprobe_destroy(struct perf_event *p_event) mutex_lock(&event_mutex); perf_trace_event_close(p_event); perf_trace_event_unreg(p_event); + trace_event_put_ref(p_event->tp_event); mutex_unlock(&event_mutex); =20 destroy_local_trace_kprobe(p_event->tp_event); @@ -347,6 +347,7 @@ void perf_uprobe_destroy(struct perf_event *p_event) mutex_lock(&event_mutex); perf_trace_event_close(p_event); perf_trace_event_unreg(p_event); + trace_event_put_ref(p_event->tp_event); mutex_unlock(&event_mutex); destroy_local_trace_uprobe(p_event->tp_event); } --=20 2.35.1