From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 72C6D2110 for ; Mon, 8 Sep 2025 00:23:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757291004; cv=none; b=kpiKsQieHSrmt/mY531xTsjz5v5cO+/AysGxb0Ho0oCq7Hov43fuRV6QIi1QxM3wdc6nsxoZKMkNE8ScGGubUcbGNUZ8iFU6nzwiHm4ucqtqteM3i11LHCqSym4ciyLM0muvvtiBHw2t0jZBiFOYAV2/H8nQnXSKN1zSNmM4+XQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757291004; c=relaxed/simple; bh=ofkxrUMOoukMAjGb1GpwCj33riTMAfqrbd2xGSYNVCA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RIIhbYQ5Pzq7qYTif0hF7dW5JjU/QLkh6BNGAOGBTFVjWYZNhwwbKiydSg29VhpLXcs7oaBJEoBJL9oRuNd0TIVJ6sm7uof02crQRbV7eaf0BTYsFW43ibawawYsGL3lzbpMQ6fdMLvMaaeiva8gR0fsGF2uYbrz/SK3YjW50k8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=g7siQeps; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="g7siQeps" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42FDEC4CEF1; Mon, 8 Sep 2025 00:23:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757291004; bh=ofkxrUMOoukMAjGb1GpwCj33riTMAfqrbd2xGSYNVCA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=g7siQepsDZdETIC0BnAAvnNEwdxESnADLfNqwYARGHe07HannsQcu///rmamRVzMi 70cQQQNbzNsMosgiU9ky1gmeL75ENW14Y9ESsenIr/YzJwnSKKAAd4KjMMWza3TExK IWYjlePN+3DjXw/1uwHw1+PdWdWpe/U04onubHeZxvQzNPoSZRrScDe6WGtZoPoP3i HNJRjB4CwmLeGG43EwCcFQQ5//UBR0XPKsNEKK7OTnvL2kujuIAGID+og7fG4AmoRp gOl5egX/aHBwtkClxugMHr3kT1t57ORhQ7RFsN/dqQss9nawIKVQWalGqazZ9Gd0KL yKgp4EIR3KbYw== From: Sasha Levin To: stable@vger.kernel.org Cc: Steven Rostedt , Mathieu Desnoyers , Tom Zanussi , Douglas Raillard , "Masami Hiramatsu (Google)" , Sasha Levin Subject: [PATCH 5.15.y] tracing: Do not add length to print format in synthetic events Date: Sun, 7 Sep 2025 20:23:21 -0400 Message-ID: <20250908002321.961475-1-sashal@kernel.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <2025041710-herald-hardwood-63d1@gregkh> References: <2025041710-herald-hardwood-63d1@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Steven Rostedt [ Upstream commit e1a453a57bc76be678bd746f84e3d73f378a9511 ] The following causes a vsnprintf fault: # echo 's:wake_lat char[] wakee; u64 delta;' >> /sys/kernel/tracing/dynamic_events # echo 'hist:keys=pid:ts=common_timestamp.usecs if !(common_flags & 0x18)' > /sys/kernel/tracing/events/sched/sched_waking/trigger # echo 'hist:keys=next_pid:delta=common_timestamp.usecs-$ts:onmatch(sched.sched_waking).trace(wake_lat,next_comm,$delta)' > /sys/kernel/tracing/events/sched/sched_switch/trigger Because the synthetic event's "wakee" field is created as a dynamic string (even though the string copied is not). The print format to print the dynamic string changed from "%*s" to "%s" because another location (__set_synth_event_print_fmt()) exported this to user space, and user space did not need that. But it is still used in print_synth_event(), and the output looks like: -0 [001] d..5. 193.428167: wake_lat: wakee=(efault)sshd-sessiondelta=155 sshd-session-879 [001] d..5. 193.811080: wake_lat: wakee=(efault)kworker/u34:5delta=58 -0 [002] d..5. 193.811198: wake_lat: wakee=(efault)bashdelta=91 bash-880 [002] d..5. 193.811371: wake_lat: wakee=(efault)kworker/u35:2delta=21 -0 [001] d..5. 193.811516: wake_lat: wakee=(efault)sshd-sessiondelta=129 sshd-session-879 [001] d..5. 193.967576: wake_lat: wakee=(efault)kworker/u34:5delta=50 The length isn't needed as the string is always nul terminated. Just print the string and not add the length (which was hard coded to the max string length anyway). Cc: stable@vger.kernel.org Cc: Mathieu Desnoyers Cc: Tom Zanussi Cc: Douglas Raillard Acked-by: Masami Hiramatsu (Google) Link: https://lore.kernel.org/20250407154139.69955768@gandalf.local.home Fixes: 4d38328eb442d ("tracing: Fix synth event printk format for str fields"); Signed-off-by: Steven Rostedt (Google) [ offset calculations instead of union-based data structures ] Signed-off-by: Sasha Levin --- kernel/trace/trace_events_synth.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index ab54810bd8d99..62d146254f470 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -364,13 +364,11 @@ static enum print_line_t print_synth_event(struct trace_iterator *iter, str_field = (char *)entry + data_offset; trace_seq_printf(s, print_fmt, se->fields[i]->name, - STR_VAR_LEN_MAX, str_field, i == se->n_fields - 1 ? "" : " "); n_u64++; } else { trace_seq_printf(s, print_fmt, se->fields[i]->name, - STR_VAR_LEN_MAX, (char *)&entry->fields[n_u64], i == se->n_fields - 1 ? "" : " "); n_u64 += STR_VAR_LEN_MAX / sizeof(u64); -- 2.51.0