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Message-ID: <1459336039.5907.37.camel@linux.intel.com>
Subject: Re: [PATCH v2 2/5] string_helpers: add kstrdup_quotable_cmdline
From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Kees Cook <keescook@chromium.org>, James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Kalle Valo <kvalo@codeaurora.org>,
        Mauro Carvalho Chehab <mchehab@osg.samsung.com>,
        Joe Perches <joe@perches.com>, Guenter Roeck <linux@roeck-us.net>,
        Jiri Slaby <jslaby@suse.com>, Paul Moore <pmoore@redhat.com>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Mimi Zohar <zohar@linux.vnet.ibm.com>,
        Casey Schaufler <casey@schaufler-ca.com>,
        Andreas Gruenbacher <agruenba@redhat.com>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org
Date: Wed, 30 Mar 2016 14:07:19 +0300
In-Reply-To: <1459199662-16558-3-git-send-email-keescook@chromium.org>
References: <1459199662-16558-1-git-send-email-keescook@chromium.org>
	 <1459199662-16558-3-git-send-email-keescook@chromium.org>
Organization: Intel Finland Oy
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On Mon, 2016-03-28 at 14:14 -0700, Kees Cook wrote:
> Provide an escaped (but readable: no inter-argument NULLs)
> commandline
> safe for logging.

> +/*
> + * Returns allocated NULL-terminated string containing process
> + * command line, with inter-argument NULLs replaced with spaces,
> + * and other special characters escaped.
> + */
> +char *kstrdup_quotable_cmdline(struct task_struct *task)
> +{
> +	char *buffer, *quoted;
> +	int i, res;
> +
> +	buffer = kmalloc(PAGE_SIZE, GFP_TEMPORARY);
> +	if (!buffer)
> +		return NULL;
> +
> +	res = get_cmdline(task, buffer, PAGE_SIZE - 1);
> +	buffer[res] = '\0';
> +
> +	/* Collapse trailing NULLs. */
> +	for (; res > 0; res--)
> +		if (buffer[res-1] != '\0')
> +			break;

/* buffer[res] is '\0', so, predecrement is safe here */
while (buffer[--res] == '\0')
 /* nothing */;

?

> +
> +	/* Replace inter-argument NULLs. */
> +	for (i = 0; i < res; i++)
> +		if (buffer[i] == '\0')
> +			buffer[i] = ' ';
> +
> +	/* Make sure result is printable. */
> +	quoted = kstrdup_quotable(buffer);
> +	kfree(buffer);
> +	return quoted;
> +}
> +EXPORT_SYMBOL_GPL(kstrdup_quotable_cmdline);

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy