linux-kernel - Re: [PATCH] ftrace: use strscpy to replace strlcpy

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Date:   Fri, 1 Jul 2022 11:28:37 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     "XueBing Chen" <chenxuebing@...i.cn>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: use strscpy to replace strlcpy

On Fri, 1 Jul 2022 19:09:15 +0800 (GMT+08:00)
"XueBing Chen" <chenxuebing@...i.cn> wrote:

> The strlcpy should not be used because it doesn't limit the source
> length. Preferred is strscpy.
> 
> Signed-off-by: XueBing Chen <chenxuebing@...i.cn>
> ---
>  kernel/trace/ftrace.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> index 601ccf1b2f09..8d2ad1472fcb 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -5902,7 +5902,7 @@ bool ftrace_filter_param __initdata;
>  static int __init set_ftrace_notrace(char *str)
>  {
>  	ftrace_filter_param = true;
> -	strlcpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE);
> +	strscpy(ftrace_notrace_buf, str, FTRACE_FILTER_SIZE);
>  	return 1;
>  }
>  __setup("ftrace_notrace=", set_ftrace_notrace);
> @@ -5910,7 +5910,7 @@ __setup("ftrace_notrace=", set_ftrace_notrace);
>  static int __init set_ftrace_filter(char *str)
>  {
>  	ftrace_filter_param = true;
> -	strlcpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE);
> +	strscpy(ftrace_filter_buf, str, FTRACE_FILTER_SIZE);
>  	return 1;
>  }
>  __setup("ftrace_filter=", set_ftrace_filter);
> @@ -5922,14 +5922,14 @@ static int ftrace_graph_set_hash(struct ftrace_hash *hash, char *buffer);
>  
>  static int __init set_graph_function(char *str)
>  {
> -	strlcpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
> +	strscpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
>  	return 1;
>  }
>  __setup("ftrace_graph_filter=", set_graph_function);
>  
>  static int __init set_graph_notrace_function(char *str)
>  {
> -	strlcpy(ftrace_graph_notrace_buf, str, FTRACE_FILTER_SIZE);
> +	strscpy(ftrace_graph_notrace_buf, str, FTRACE_FILTER_SIZE);
>  	return 1;
>  }


No need for strscpy() in init functions that simply read the kernel command
line.

>  __setup("ftrace_graph_notrace=", set_graph_notrace_function);
> @@ -6714,8 +6714,8 @@ static int ftrace_get_trampoline_kallsym(unsigned int symnum,
>  			continue;
>  		*value = op->trampoline;
>  		*type = 't';
> -		strlcpy(name, FTRACE_TRAMPOLINE_SYM, KSYM_NAME_LEN);
> -		strlcpy(module_name, FTRACE_TRAMPOLINE_MOD, MODULE_NAME_LEN);
> +		strscpy(name, FTRACE_TRAMPOLINE_SYM, KSYM_NAME_LEN);
> +		strscpy(module_name, FTRACE_TRAMPOLINE_MOD, MODULE_NAME_LEN);

The source is a macro, no need for strscpy() here.


>  		*exported = 0;
>  		return 0;
>  	}
> @@ -7046,7 +7046,7 @@ ftrace_func_address_lookup(struct ftrace_mod_map *mod_map,
>  		if (off)
>  			*off = addr - found_func->ip;
>  		if (sym)
> -			strlcpy(sym, found_func->name, KSYM_NAME_LEN);
> +			strscpy(sym, found_func->name, KSYM_NAME_LEN);

The name can not be bigger than KSYM_NAME_LEN, no need for strscpy() here.

>  
>  		return found_func->name;
>  	}
> @@ -7100,8 +7100,8 @@ int ftrace_mod_get_kallsym(unsigned int symnum, unsigned long *value,
>  
>  			*value = mod_func->ip;
>  			*type = 'T';
> -			strlcpy(name, mod_func->name, KSYM_NAME_LEN);
> -			strlcpy(module_name, mod_map->mod->name, MODULE_NAME_LEN);
> +			strscpy(name, mod_func->name, KSYM_NAME_LEN);
> +			strscpy(module_name, mod_map->mod->name, MODULE_NAME_LEN);

Same for this.

I don't see how converting any of these to strscpy() is helpful.

NAK.

-- Steve

>  			*exported = 1;
>  			preempt_enable();
>  			return 0;