linux-kernel - Re: [PATCH v4 3/6] string_helpers: add kstrdup_quotable

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Date:	Tue, 12 Apr 2016 16:24:45 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	James Morris <jmorris@...ei.org>, Joe Perches <joe@...ches.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Serge E. Hallyn" <serge@...lyn.com>,
	Jonathan Corbet <corbet@....net>,
	Kalle Valo <kvalo@...eaurora.org>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Jiri Slaby <jslaby@...e.com>, Paul Moore <pmoore@...hat.com>,
	Stephen Smalley <sds@...ho.nsa.gov>,
	Casey Schaufler <casey@...aufler-ca.com>,
	Andreas Gruenbacher <agruenba@...hat.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH v4 3/6] string_helpers: add kstrdup_quotable_file

Quoting Kees Cook (keescook@...omium.org):
> Allocate a NULL-terminated file path with special characters escaped,
> safe for logging.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>

Acked-by: Serge Hallyn <serge.hallyn@...onical.com>

> ---
>  include/linux/string_helpers.h |  3 +++
>  lib/string_helpers.c           | 30 ++++++++++++++++++++++++++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
> index 684d2695fc36..5ce9538f290e 100644
> --- a/include/linux/string_helpers.h
> +++ b/include/linux/string_helpers.h
> @@ -3,6 +3,8 @@
>  
>  #include <linux/types.h>
>  
> +struct file;
> +
>  /* Descriptions of the types of units to
>   * print in */
>  enum string_size_units {
> @@ -70,5 +72,6 @@ static inline int string_escape_str_any_np(const char *src, char *dst,
>  
>  char *kstrdup_quotable(const char *src, gfp_t gfp);
>  char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp);
> +char *kstrdup_quotable_file(struct file *file, gfp_t gfp);
>  
>  #endif
> diff --git a/lib/string_helpers.c b/lib/string_helpers.c
> index b16ee85aaf87..ecaac2c0526f 100644
> --- a/lib/string_helpers.c
> +++ b/lib/string_helpers.c
> @@ -10,6 +10,8 @@
>  #include <linux/export.h>
>  #include <linux/ctype.h>
>  #include <linux/errno.h>
> +#include <linux/fs.h>
> +#include <linux/limits.h>
>  #include <linux/mm.h>
>  #include <linux/slab.h>
>  #include <linux/string.h>
> @@ -596,3 +598,31 @@ char *kstrdup_quotable_cmdline(struct task_struct *task, gfp_t gfp)
>  	return quoted;
>  }
>  EXPORT_SYMBOL_GPL(kstrdup_quotable_cmdline);
> +
> +/*
> + * Returns allocated NULL-terminated string containing pathname,
> + * with special characters escaped, able to be safely logged. If
> + * there is an error, the leading character will be "<".
> + */
> +char *kstrdup_quotable_file(struct file *file, gfp_t gfp)
> +{
> +	char *temp, *pathname;
> +
> +	if (!file)
> +		return kstrdup("<unknown>", gfp);
> +
> +	/* We add 11 spaces for ' (deleted)' to be appended */
> +	temp = kmalloc(PATH_MAX + 11, GFP_TEMPORARY);
> +	if (!temp)
> +		return kstrdup("<no_memory>", gfp);
> +
> +	pathname = file_path(file, temp, PATH_MAX + 11);
> +	if (IS_ERR(pathname))
> +		pathname = kstrdup("<too_long>", gfp);
> +	else
> +		pathname = kstrdup_quotable(pathname, gfp);
> +
> +	kfree(temp);
> +	return pathname;
> +}
> +EXPORT_SYMBOL_GPL(kstrdup_quotable_file);
> -- 
> 2.6.3