From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793207656; b=U5leJaQs65DfJGVoGpcj/uGpmVvsLGKtxWZuqj1y0y2gpUWedhAekkmAn42HPuN3x0sm 3zRz7wcPmJJh9nKziZT0N00aS2ZEFluG4gHui2tsxAj/u53WABsK714Uxk9dFrpnVafP0 nNhw2o5P7B4HIY83K39zE44tLXNmQir5gApov+dwzIZScY/p745V8Ar0JZiqbT9JO8QkZ Bk2z7nnoYtnhsJzJ1wTLSV4ZTAjDIzXxxx/2MLgIw/n/azs280oGiTM8IRmepuWI6zB9u bagXegVDgVboZAPYoQBisbOhAhPMEc3fT380GtcwvUC4lh3f/9t5U29UhwSNvx/qTzg== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793207656; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=Gv0M2Bz3hpddZaM8d9U4CH/QKP7glonyXKibiSPBUAo=; b=pCqLytk/g7oH1guG2hN3adTdSjjoC0QsR26Rm1+hdl9iAyfOLaK/Mdt8JOkERfNkJlVX 27jmVKLZJui3KTbxTH8hACSiDawmZ3lBBxYhzUEQeq2fuq75pczSVrtyC++k9JWA9u1gW r90UWwTIt843k2mRds7+OjplJK9l0HzDV/VvRevJzAyJTNwd8JBrFDaTrSM+ZhvBmaVsa T1soBY/VcaiwyxsYpYSDN8YTFQLNas+etI0gDBbPff9Tce2cNSNqc2zv9b84cjaYnCJ5X MaYyAZ9TSAqnVL79kEiplSgkYWTwQZ/FW2oeKHDUuXRQ1F6vfJBhIMSEPVvYvUJQKlQ== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=0nTHwm6I; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 667E6606A31A; Wed, 28 Oct 2026 17:14:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=0nTHwm6I Received: by smtp.kernel.org (Postfix) with ESMTPSA id B32991F01825; Wed, 28 Oct 2026 17:14:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793207656; bh=Gv0M2Bz3hpddZaM8d9U4CH/QKP7glonyXKibiSPBUAo=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=0nTHwm6IlaEVPr5UIXGz8pUwFoYL/4dEmtvpRXkojnO1esXdFlNylhIbK53so2Aia N/EW5Yq0nJm47wyiXtiTNkNzTXAuBa5o9KgzQOaVkvLVCRiBzHhsS6zJdB23J3/Eo+ b2drOvg6dj68dqxfS8qF6ngEZb5v61CjOWKKFEwU= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Tengda Wu , Steven Rostedt Subject: [PATCH 6.12 094/247] tracing: Fix hist trigger timestamps for buffered events Date: Wed, 28 Oct 2026 17:58:17 +0100 Message-ID: <20261028165949.621088142@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165947.349197979@linuxfoundation.org> References: <20261028165947.349197979@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tengda Wu commit 9414ca3b99e5a7f1f3bf51c2a01b383e1b355dd0 upstream. Syzkaller triggered a WARN_ON_ONCE(!nest) warning: WARNING: kernel/trace/ring_buffer.c:821 at ring_buffer_event_time_stamp Call trace: ring_buffer_event_time_stamp hist_field_timestamp hist_fn_call event_hist_trigger event_triggers_call __event_trigger_test_discard trace_event_buffer_commit do_trace_event_raw_event_sched_switch trace_event_raw_event_sched_switch The warning is probabilistically reproducible and is related to syzkaller executing the following commands: echo 'prev_pid == 999999' > events/sched/sched_switch/filter echo 'hist:keys=common_timestamp' > events/sched/sched_switch/trigger The specific triggering process is as follows: CPU 0 CPU 1 (context switching) (echo 'hist:keys=common_timestamp' > \ events/sched/sched_switch/trigger) do_trace_event_raw_event_##call trace_event_buffer_lock_reserve if (!tr->no_filter_buffering_ref && trace_file->flags & EVENT_FILE_FL_FILTERED) return entry; // return directly event_hist_trigger_parse hist_register_trigger tracing_set_filter_buffering(file->tr, true); tr->no_filter_buffering_ref++; __trace_buffer_lock_reserve rb_start_commit local_inc(&cpu_buffer->committing); // skipped and not executed trace_event_buffer_commit __event_trigger_test_discard event_triggers_call event_hist_trigger hist_fn_call hist_field_timestamp ring_buffer_event_time_stamp nest = local_read(&cpu_buffer->committing); WARN_ON_ONCE(!nest) // trigger warning The root cause is that when an event file has a filter attached and the hist trigger has not yet been attached, trace_event_buffer_lock_reserve() writes the event into the per-CPU trace_buffered_event temp buffer instead of reserving it in the ring buffer, so cpu_buffer->committing is not incremented. When the event is later processed at commit time by a hist trigger, hist_field_timestamp() -> ring_buffer_event_time_stamp() sees a zero committing count, triggering WARN_ON_ONCE(!nest). tracing_event_time_stamp() was added by commit d8279bfc5e959 ("tracing: Add tracing_event_time_stamp() API") for exactly this case: if the event is the per-CPU trace_buffered_event, it returns the current ring buffer timestamp. But it never gained a caller. Use it in hist_field_timestamp(), so that a hist trigger that races onto a buffered event records the current time, which is only marginally later than when the event was recorded, instead of warning and recording a bogus timestamp. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260929104015.1689921-1-wutengda@huaweicloud.com Fixes: b94bc80df648 ("tracing: Use a no_filter_buffering_ref to stop using the filter buffer") Signed-off-by: Tengda Wu Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- kernel/trace/trace_events_hist.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -866,7 +866,7 @@ static u64 hist_field_timestamp(struct h struct hist_trigger_data *hist_data = hist_field->hist_data; struct trace_array *tr = hist_data->event_file->tr; - u64 ts = ring_buffer_event_time_stamp(buffer, rbe); + u64 ts = tracing_event_time_stamp(buffer, rbe); if (hist_data->attrs->ts_in_usecs && trace_clock_in_ns(tr)) ts = ns2usecs(ts);