linux-kernel - Re: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs

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Date:   Fri, 28 Aug 2020 00:58:37 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Denis Efremov <efremov@...ux.com>,
        Julia Lawall <julia.lawall@...ia.fr>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-kernel@...r.kernel.org, cocci <cocci@...teme.lip6.fr>,
        Alex Dewar <alex.dewar90@...il.com>
Subject: Re: [Cocci] [PATCH] usb: atm: don't use snprintf() for sysfs attrs

On Thu, Aug 27, 2020 at 09:12:06PM -0700, Joe Perches wrote:
> Perhaps something like the below with a sample conversion
> that uses single and multiple sysfs_emit uses.

On quick review, I like it. :)

> [...]
> +int sysfs_emit(char *buf, char *pos, const char *fmt, ...)
> +{
> +	int len;
> +	va_list args;
> +
> +	WARN(pos < buf, "pos < buf\n");
> +	WARN(pos - buf >= PAGE_SIZE, "pos >= PAGE_SIZE (%tu > %lu)\n",
> +	     pos - buf, PAGE_SIZE);
> +	if (pos < buf || pos - buf >= PAGE_SIZE)
> +		return 0;

This can be:

	if (WARN(pos < buf, "pos < buf\n") ||
	    WARN(pos - buf >= PAGE_SIZE, "pos >= PAGE_SIZE (%tu > %lu)\n",
		 pos - buf, PAGE_SIZE))
		return 0;

-- 
Kees Cook