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

Steven Rostedt
2025-07-18T17:55:58Z

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

> From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
>
> Allocate temporary string buffers for parsing eprobe-events
> from heap instead of stack.
>
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.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@gmail.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@gmail.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;