linux-kernel - [for-next][PATCH 09/12] tracing: Fix strncpy warning in trace_events

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Message-ID: <20220312232551.559953567@goodmis.org>
Date:   Sat, 12 Mar 2022 18:25:34 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kernel test robot <lkp@...el.com>,
        Tom Zanussi <zanussi@...nel.org>
Subject: [for-next][PATCH 09/12] tracing: Fix strncpy warning in trace_events_synth.c

From: Tom Zanussi <zanussi@...nel.org>

0-day reported the strncpy error below:

../kernel/trace/trace_events_synth.c: In function 'last_cmd_set':
../kernel/trace/trace_events_synth.c:65:9: warning: 'strncpy' specified bound depends on the length o\
f the source argument [-Wstringop-truncation]
   65 |         strncpy(last_cmd, str, strlen(str) + 1);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../kernel/trace/trace_events_synth.c:65:32: note: length computed here
   65 |         strncpy(last_cmd, str, strlen(str) + 1);
      |                                ^~~~~~~~~~~

There's no reason to use strncpy here, in fact there's no reason to do
anything but a simple kstrdup() (note we don't even need to check for
failure since last_cmod is expected to be either the last cmd string
or NULL, and the containing function is a void return).

Link: https://lkml.kernel.org/r/77deca8cbfd226981b3f1eab203967381e9b5bd9.camel@kernel.org

Fixes: 27c888da9867 ("tracing: Remove size restriction on synthetic event cmd error logging")

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Tom Zanussi <zanussi@...nel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 kernel/trace/trace_events_synth.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index fdd79e07e2fc..5e8c07aef071 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -58,11 +58,8 @@ static void last_cmd_set(const char *str)
 		return;
 
 	kfree(last_cmd);
-	last_cmd = kzalloc(strlen(str) + 1, GFP_KERNEL);
-	if (!last_cmd)
-		return;
 
-	strncpy(last_cmd, str, strlen(str) + 1);
+	last_cmd = kstrdup(str, GFP_KERNEL);
 }
 
 static void synth_err(u8 err_type, u16 err_pos)
-- 
2.35.1