linux-kernel - [for-next][PATCH 1/2] tracing: Fix synth event printk format for str fields

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Message-ID: <20250327000827.980585561@goodmis.org>
Date: Wed, 26 Mar 2025 20:08:12 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: linux-kernel@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>,
 Mark Rutland <mark.rutland@....com>,
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 stable@...r.kernel.org,
 Douglas Raillard <douglas.raillard@....com>
Subject: [for-next][PATCH 1/2] tracing: Fix synth event printk format for str fields

From: Douglas Raillard <douglas.raillard@....com>

The printk format for synth event uses "%.*s" to print string fields,
but then only passes the pointer part as var arg.

Replace %.*s with %s as the C string is guaranteed to be null-terminated.

The output in print fmt should never have been updated as __get_str()
handles the string limit because it can access the length of the string in
the string meta data that is saved in the ring buffer.

Cc: stable@...r.kernel.org
Cc: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Fixes: 8db4d6bfbbf92 ("tracing: Change synthetic event string format to limit printed length")
Link: https://lore.kernel.org/20250325165202.541088-1-douglas.raillard@arm.com
Signed-off-by: Douglas Raillard <douglas.raillard@....com>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_events_synth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index a5c5f34c207a..6d592cbc38e4 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -305,7 +305,7 @@ static const char *synth_field_fmt(char *type)
 	else if (strcmp(type, "gfp_t") == 0)
 		fmt = "%x";
 	else if (synth_field_is_string(type))
-		fmt = "%.*s";
+		fmt = "%s";
 	else if (synth_field_is_stack(type))
 		fmt = "%s";
 
-- 
2.47.2