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

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Message-ID: <20250718135846.6dd841e7@batman.local.home>
Date: Fri, 18 Jul 2025 13:58:46 -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 5/5] tracing: uprobe-event: Allocate string buffers from
 heap

On Fri, 18 Jul 2025 20:34:51 +0900
"Masami Hiramatsu (Google)" <mhiramat@...nel.org> wrote:

> From: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> 
> Allocate temporary string buffers for parsing uprobe-events
> from heap instead of stack.
> 
> Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
> ---
>  kernel/trace/trace_uprobe.c |   22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
> index 1fd479718d03..17124769e254 100644
> --- a/kernel/trace/trace_uprobe.c
> +++ b/kernel/trace/trace_uprobe.c
> @@ -7,6 +7,7 @@
>   */
>  #define pr_fmt(fmt)	"trace_uprobe: " fmt
>  
> +#include <linux/cleanup.h>
>  #include <linux/bpf-cgroup.h>
>  #include <linux/security.h>
>  #include <linux/ctype.h>
> @@ -19,6 +20,7 @@
>  #include <linux/filter.h>
>  #include <linux/percpu.h>
>  
> +#include "trace.h"
>  #include "trace_dynevent.h"
>  #include "trace_probe.h"
>  #include "trace_probe_tmpl.h"
> @@ -538,15 +540,15 @@ static int register_trace_uprobe(struct trace_uprobe *tu)
>  static int __trace_uprobe_create(int argc, const char **argv)
>  {
>  	struct traceprobe_parse_context *ctx __free(traceprobe_parse_context) = NULL;
> -	struct trace_uprobe *tu;
>  	const char *event = NULL, *group = UPROBE_EVENT_SYSTEM;
>  	char *arg, *filename, *rctr, *rctr_end, *tmp;
> -	char buf[MAX_EVENT_NAME_LEN];
> -	char gbuf[MAX_EVENT_NAME_LEN];
> -	enum probe_print_type ptype;
> -	struct path path;
>  	unsigned long offset, ref_ctr_offset;
> +	char *gbuf __free(kfree) = NULL;
> +	char *buf __free(kfree) = NULL;
> +	enum probe_print_type ptype;
> +	struct trace_uprobe *tu;
>  	bool is_return = false;
> +	struct path path;
>  	int i, ret;
>  
>  	ref_ctr_offset = 0;
> @@ -654,6 +656,11 @@ static int __trace_uprobe_create(int argc, const char **argv)
>  	/* setup a probe */
>  	trace_probe_log_set_index(0);
>  	if (event) {
> +		gbuf = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
> +		if (!gbuf) {
> +			ret = -ENOMEM;
> +			goto fail_address_parse;
> +		}
>  		ret = traceprobe_parse_event_name(&event, &group, gbuf,
>  						  event - argv[0]);
>  		if (ret)
> @@ -674,6 +681,11 @@ static int __trace_uprobe_create(int argc, const char **argv)
>  		if (ptr)
>  			*ptr = '\0';
>  
> +		buf = kmalloc(MAX_EVENT_NAME_LEN, GFP_KERNEL);
> +		if (!buf) {
> +			ret = -ENOMEM;
> +			goto fail_address_parse;
> +		}
>  		snprintf(buf, MAX_EVENT_NAME_LEN, "%c_%s_0x%lx", 'p', tail, offset);
>  		event = buf;
>  		kfree(tail);

You could easily do the same thing as I mentioned in my reply to patch 4:

		if (!buf)
			goto fail_mem;

error:
	free_trace_uprobe(tu);
out:
	trace_probe_log_clear();
	return ret;

fail_mem:
	ret = -ENOMEM;
fail_address_parse:
	trace_probe_log_clear();
	path_put(&path);
	kfree(filename);

	return ret;
}

-- Steve