linux-kernel - [PATCH 7/7] tracing: Remove size restriction on synthetic event cmd error logging

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Date:   Thu, 27 Jan 2022 15:44:21 -0600
From:   Tom Zanussi <zanussi@...nel.org>
To:     rostedt@...dmis.org
Cc:     mhiramat@...nel.org, linux-kernel@...r.kernel.org,
        Tom Zanussi <zanussi@...nel.org>
Subject: [PATCH 7/7] tracing: Remove size restriction on synthetic event cmd error logging

Currently, synthetic event command error strings are restricted to a
length of MAX_FILTER_STR_VAL (256), which is too short for some
commands already seen in the wild (with cmd strings longer than that
showing up truncated in err_log).

Remove the restriction so that no synthetic event command error string
is ever truncated.

Signed-off-by: Tom Zanussi <zanussi@...nel.org>
---
 kernel/trace/trace_events_synth.c | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 149011e34ad9..7d50b4251c60 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -42,10 +42,13 @@ enum { ERRORS };
 
 static const char *err_text[] = { ERRORS };
 
-static char last_cmd[MAX_FILTER_STR_VAL];
+static char *last_cmd;
 
 static int errpos(const char *str)
 {
+	if (!str || !last_cmd)
+		return 0;
+
 	return err_pos(last_cmd, str);
 }
 
@@ -54,11 +57,19 @@ static void last_cmd_set(const char *str)
 	if (!str)
 		return;
 
-	strncpy(last_cmd, str, MAX_FILTER_STR_VAL - 1);
+	kfree(last_cmd);
+	last_cmd = kzalloc(strlen(str) + 1, GFP_KERNEL);
+	if (!last_cmd)
+		return;
+
+	strncpy(last_cmd, str, strlen(str));
 }
 
-static void synth_err(u8 err_type, u8 err_pos)
+static void synth_err(u8 err_type, u16 err_pos)
 {
+	if (!last_cmd)
+		return;
+
 	tracing_log_err(NULL, "synthetic_events", last_cmd, err_text,
 			err_type, err_pos);
 }
-- 
2.17.1