linux-kernel - Re: [PATCH v1 2/2] platform/x86: think-lmi: Use strreplace() to replace a character by nul

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Message-ID: <c6caae28-01fc-2354-6c7a-3f515a0e1402@rasmusvillemoes.dk>
Date:   Mon, 18 Sep 2023 16:48:40 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Pearson <mpearson-lenovo@...ebb.ca>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Mark Pearson <markpearson@...ovo.com>,
        Mark Gross <markgross@...nel.org>
Subject: Re: [PATCH v1 2/2] platform/x86: think-lmi: Use strreplace() to
 replace a character by nul

On 13/09/2023 11.27, Andy Shevchenko wrote:

> @@ -921,7 +913,7 @@ static ssize_t display_name_show(struct kobject *kobj, struct kobj_attribute *at
>  static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
>  {
>  	struct tlmi_attr_setting *setting = to_tlmi_attr_setting(kobj);
> -	char *item, *value, *p;
> +	char *item, *value;
>  	int ret;
>  
>  	ret = tlmi_setting(setting->index, &item, LENOVO_BIOS_SETTING_GUID);
> @@ -934,8 +926,7 @@ static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *a
>  		ret = -EINVAL;
>  	else {
>  		/* On Workstations remove the Options part after the value */
> -		p = strchrnul(value, ';');
> -		*p = '\0';
> +		strreplace(value, ';', '\0');

So how do you know that the string contains at most one ';'? Same for
all the other replacements. If that's not guaranteed, this is not at all
equivalent.

Or maybe the result is just used a normal string afterwards, and it
doesn't matter at all how the content after the first ';' has been mangled?

It's certainly not obvious to me that this is correct, but of course I
know nothing about this code.

Rasmus