linux-kernel - [PATCH v4 7/7] tracing: Change synthetic event string format to limit printed length

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Date:   Sun,  4 Oct 2020 17:14:09 -0500
From:   Tom Zanussi <zanussi@...nel.org>
To:     rostedt@...dmis.org, axelrasmussen@...gle.com
Cc:     mhiramat@...nel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v4 7/7] tracing: Change synthetic event string format to limit printed length

From: Steven Rostedt <rostedt@...dmis.org>

Change the format for printing synthetic field strings to limit the
length of the string printed even if it's not correctly terminated.

Description from Steve:

I also added this for a bit of paranoid, and probably should be a
separate patch, just to make sure if the string isn't nul terminated,
this will keep it from bleeding pass the end of the string.
---
 kernel/trace/trace_events_synth.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 24bc6d61aa40..742ce5f62d6d 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -234,7 +234,7 @@ 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";
 
 	return fmt;
 }
@@ -303,11 +303,13 @@ 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);
-- 
2.17.1