linux-kernel - Re: [PATCH] tracing: Fix possible memory leak in __create_synth

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Message-ID: <20211208154457.3a301cf8@gandalf.local.home>
Date:   Wed, 8 Dec 2021 15:44:57 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Miaoqian Lin <linmq006@...il.com>
Cc:     Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tracing: Fix possible memory leak in
 __create_synth_event

On Fri, 26 Nov 2021 10:47:08 +0000
Miaoqian Lin <linmq006@...il.com> wrote:

> Before goto err, call argv_free to handle argv in order to prevent
> memory leak.
> 
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
>  kernel/trace/trace_events_synth.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
> index 22db3ce95e74..fe2e37564c9b 100644
> --- a/kernel/trace/trace_events_synth.c
> +++ b/kernel/trace/trace_events_synth.c
> @@ -1261,6 +1261,7 @@ static int __create_synth_event(const char *name, const char *raw_fields)
>  			 */
>  			if (cmd_version > 1 && n_fields_this_loop >= 1) {
>  				synth_err(SYNTH_ERR_INVALID_CMD, errpos(field_str));
> +				argv_free(argv);
>  				ret = -EINVAL;
>  				goto err;
>  			}
> @@ -1268,6 +1269,7 @@ static int __create_synth_event(const char *name, const char *raw_fields)
>  			fields[n_fields++] = field;
>  			if (n_fields == SYNTH_FIELDS_MAX) {
>  				synth_err(SYNTH_ERR_TOO_MANY_FIELDS, 0);
> +				argv_free(argv);
>  				ret = -EINVAL;
>  				goto err;
>  			}
> @@ -1277,6 +1279,7 @@ static int __create_synth_event(const char *name, const char *raw_fields)
>  
>  		if (consumed < argc) {
>  			synth_err(SYNTH_ERR_INVALID_CMD, 0);
> +			argv_free(argv);
>  			ret = -EINVAL;
>  			goto err;
>  		}

A cleaner way is to have:

diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c
index 98e002648994..a88f1f9046a6 100644
--- a/kernel/trace/trace_events_synth.c
+++ b/kernel/trace/trace_events_synth.c
@@ -1237,9 +1237,8 @@ static int __create_synth_event(const char *name, const char *raw_fields)
 						  argv + consumed, &consumed,
 						  &field_version);
 			if (IS_ERR(field)) {
-				argv_free(argv);
 				ret = PTR_ERR(field);
-				goto err;
+				goto err_free_arg;
 			}
 
 			/*
@@ -1262,26 +1261,25 @@ static int __create_synth_event(const char *name, const char *raw_fields)
 			if (cmd_version > 1 && n_fields_this_loop >= 1) {
 				synth_err(SYNTH_ERR_INVALID_CMD, errpos(field_str));
 				ret = -EINVAL;
-				goto err;
+				goto err_free_arg;
 			}
 
 			fields[n_fields++] = field;
 			if (n_fields == SYNTH_FIELDS_MAX) {
 				synth_err(SYNTH_ERR_TOO_MANY_FIELDS, 0);
 				ret = -EINVAL;
-				goto err;
+				goto err_free_arg;
 			}
 
 			n_fields_this_loop++;
 		}
+		argv_free(argv);
 
 		if (consumed < argc) {
 			synth_err(SYNTH_ERR_INVALID_CMD, 0);
 			ret = -EINVAL;
 			goto err;
 		}
-
-		argv_free(argv);
 	}
 
 	if (n_fields == 0) {
@@ -1307,6 +1305,8 @@ static int __create_synth_event(const char *name, const char *raw_fields)
 	kfree(saved_fields);
 
 	return ret;
+ err_free_arg:
+	argv_free(argv);
  err:
 	for (i = 0; i < n_fields; i++)
 		free_synth_field(fields[i]);


Feel free to send v2 and add:

Suggested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve