linux-kernel - Re: [PATCH 4/5] tracing: eprobe-event: Allocate string buffers from heap

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Message-ID: <20250718135549.387b98ab@batman.local.home>
Date: Fri, 18 Jul 2025 13:55:49 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 4/5] tracing: eprobe-event: Allocate string buffers from
 heap

On Fri, 18 Jul 2025 20:34:40 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Allocate temporary string buffers for parsing eprobe-events
> from heap instead of stack.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> ---
>  kernel/trace/trace_eprobe.c |   24 ++++++++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
> index 1e18a8619b40..75d8208cd859 100644
> --- a/kernel/trace/trace_eprobe.c
> +++ b/kernel/trace/trace_eprobe.c
> @@ -9,6 +9,7 @@
>   * Copyright (C) 2021, VMware Inc, Tzvetomir Stoyanov tz.stoyanov@...il.com>
>   *
>   */
> +#include <linux/cleanup.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
>  #include <linux/ftrace.h>
> @@ -871,10 +872,10 @@ static int __trace_eprobe_create(int argc, const char *argv[])
>  	const char *event = NULL, *group = EPROBE_EVENT_SYSTEM;
>  	const char *sys_event = NULL, *sys_name = NULL;
>  	struct trace_event_call *event_call;
> +	char *buf1 __free(kfree) = NULL;
> +	char *buf2 __free(kfree) = NULL;
> +	char *gbuf __free(kfree) = NULL;
>  	struct trace_eprobe *ep = NULL;
> -	char buf1[MAX_EVENT_NAME_LEN];
> -	char buf2[MAX_EVENT_NAME_LEN];
> -	char gbuf[MAX_EVENT_NAME_LEN];
>  	int ret = 0, filter_idx = 0;
>  	int i, filter_cnt;
>  
> @@ -885,6 +886,11 @@ static int __trace_eprobe_create(int argc, const char *argv[])
>  
>  	event = strchr(&argv[0][1], ':');
>  	if (event) {
> +		gbuf = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
> +		if (!gbuf) {
> +			ret = -ENOMEM;
> +			goto parse_error;
> +		}
>  		event++;
>  		ret = traceprobe_parse_event_name(&event, &group, gbuf,
>  						  event - argv[0]);
> @@ -894,6 +900,12 @@ static int __trace_eprobe_create(int argc, const char *argv[])
>  
>  	trace_probe_log_set_index(1);
>  	sys_event = argv[1];
> +
> +	buf2 = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
> +	if (!buf2) {
> +		ret = -ENOMEM;
> +		goto parse_error;
> +	}
>  	ret = traceprobe_parse_event_name(&sys_event, &sys_name, buf2, 0);
>  	if (ret || !sys_event || !sys_name) {
>  		trace_probe_log_err(0, NO_EVENT_INFO);
> @@ -901,7 +913,11 @@ static int __trace_eprobe_create(int argc, const char *argv[])
>  	}
>  
>  	if (!event) {
> -		strscpy(buf1, sys_event, MAX_EVENT_NAME_LEN);
> +		buf1 = kstrdup(sys_event, GFP_KERNEL);
> +		if (!buf1) {
> +			ret = -ENOMEM;
> +			goto error;
> +		}

I kinda hate all these updating of "ret" before jumping to error.

>  		event = buf1;
>  	}
>  

What about this:

-- Steve

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index 916555f0de81..48cc1079a1dd 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -9,6 +9,7 @@
  * Copyright (C) 2021, VMware Inc, Tzvetomir Stoyanov tz.stoyanov@...il.com>
  *
  */
+#include <linux/cleanup.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/ftrace.h>
@@ -869,10 +870,10 @@ static int __trace_eprobe_create(int argc, const char *argv[])
 	const char *event = NULL, *group = EPROBE_EVENT_SYSTEM;
 	const char *sys_event = NULL, *sys_name = NULL;
 	struct trace_event_call *event_call;
+	char *buf1 __free(kfree) = NULL;
+	char *buf2 __free(kfree) = NULL;
+	char *gbuf __free(kfree) = NULL;
 	struct trace_eprobe *ep = NULL;
-	char buf1[MAX_EVENT_NAME_LEN];
-	char buf2[MAX_EVENT_NAME_LEN];
-	char gbuf[MAX_EVENT_NAME_LEN];
 	int ret = 0, filter_idx = 0;
 	int i, filter_cnt;
 
@@ -883,6 +884,9 @@ static int __trace_eprobe_create(int argc, const char *argv[])
 
 	event = strchr(&argv[0][1], ':');
 	if (event) {
+		gbuf = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
+		if (!gbuf)
+			goto mem_error;
 		event++;
 		ret = traceprobe_parse_event_name(&event, &group, gbuf,
 						  event - argv[0]);
@@ -892,6 +896,10 @@ static int __trace_eprobe_create(int argc, const char *argv[])
 
 	trace_probe_log_set_index(1);
 	sys_event = argv[1];
+
+	buf2 = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
+	if (!buf2)
+		goto mem_error;
 	ret = traceprobe_parse_event_name(&sys_event, &sys_name, buf2, 0);
 	if (ret || !sys_event || !sys_name) {
 		trace_probe_log_err(0, NO_EVENT_INFO);
@@ -899,7 +907,9 @@ static int __trace_eprobe_create(int argc, const char *argv[])
 	}
 
 	if (!event) {
-		strscpy(buf1, sys_event, MAX_EVENT_NAME_LEN);
+		buf1 = kstrdup(sys_event, GFP_KERNEL);
+		if (!buf1)
+			goto mem_error;
 		event = buf1;
 	}
 
@@ -972,6 +982,9 @@ static int __trace_eprobe_create(int argc, const char *argv[])
 	trace_probe_log_clear();
 	return ret;
 
+mem_error:
+	ret = -ENOMEM;
+	goto error;
 parse_error:
 	ret = -EINVAL;
 error: