linux-kernel - Re: [PATCH] tracing/boot: Test strscpy() against less than zero for error

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Message-Id: <20230705232834.f71d8602c3c9d9c56abd0b15@kernel.org>
Date:   Wed, 5 Jul 2023 23:28:34 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux trace kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] tracing/boot: Test strscpy() against less than zero for
 error

On Tue, 4 Jul 2023 10:08:07 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> Instead of checking for -E2BIG, it is better to just check for less than
> zero of strscpy() for error. Testing for -E2BIG is not very robust, and
> the calling code does not really care about the error code, just that
> there was an error.
> 
> One of the updates to convert strlcpy() to strscpy() had a v2 version
> that changed the test from testing against -E2BIG to less than zero, but I
> took the v1 version that still tested for -E2BIG.

Indeed. This looks good to me.

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

Thank you,

> 
> Link: https://lore.kernel.org/linux-trace-kernel/20230615180420.400769-1-azeemshaikh38@gmail.com/
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  kernel/trace/trace_boot.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
> index 5fe525f1b8cc..7ccc7a8e155b 100644
> --- a/kernel/trace/trace_boot.c
> +++ b/kernel/trace/trace_boot.c
> @@ -31,7 +31,7 @@ trace_boot_set_instance_options(struct trace_array *tr, struct xbc_node *node)
>  
>  	/* Common ftrace options */
>  	xbc_node_for_each_array_value(node, "options", anode, p) {
> -		if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) {
> +		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0) {
>  			pr_err("String is too long: %s\n", p);
>  			continue;
>  		}
> @@ -87,7 +87,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node)
>  	const char *p;
>  
>  	xbc_node_for_each_array_value(node, "events", anode, p) {
> -		if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG) {
> +		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0) {
>  			pr_err("String is too long: %s\n", p);
>  			continue;
>  		}
> @@ -486,7 +486,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
>  
>  	p = xbc_node_find_value(enode, "filter", NULL);
>  	if (p && *p != '\0') {
> -		if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG)
> +		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0)
>  			pr_err("filter string is too long: %s\n", p);
>  		else if (apply_event_filter(file, buf) < 0)
>  			pr_err("Failed to apply filter: %s\n", buf);
> @@ -494,7 +494,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
>  
>  	if (IS_ENABLED(CONFIG_HIST_TRIGGERS)) {
>  		xbc_node_for_each_array_value(enode, "actions", anode, p) {
> -			if (strscpy(buf, p, ARRAY_SIZE(buf)) == -E2BIG)
> +			if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0)
>  				pr_err("action string is too long: %s\n", p);
>  			else if (trigger_process_regex(file, buf) < 0)
>  				pr_err("Failed to apply an action: %s\n", p);
> -- 
> 2.39.2
> 


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