linux-hardening - Re: [PATCH] ftrace: Replace all non-returning strlcpy with strscpy

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Date:   Thu, 18 May 2023 07:28:15 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Azeem Shaikh <azeemshaikh38@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        linux-hardening@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH] ftrace: Replace all non-returning strlcpy with strscpy

On Wed, 17 May 2023 14:53:23 +0000
Azeem Shaikh <azeemshaikh38@...il.com> wrote:

> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> No return values were used, so direct replacement is safe.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks!

> ---
>  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 764668467155..6a77edb51f18 100644
> --- a/kernel/trace/ftrace.c
> +++ b/kernel/trace/ftrace.c
> @@ -5743,7 +5743,7 @@ 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);
> @@ -5751,7 +5751,7 @@ __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);
> @@ -5763,14 +5763,14 @@ 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;
>  }
>  __setup("ftrace_graph_notrace=", set_graph_notrace_function);
> @@ -6569,8 +6569,8 @@ 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);
>  		*exported = 0;
>  		return 0;
>  	}
> @@ -6933,7 +6933,7 @@ 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);
>  
>  		return found_func->name;
>  	}
> @@ -6987,8 +6987,8 @@ 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);
>  			*exported = 1;
>  			preempt_enable();
>  			return 0;
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>