linux-kernel - Re: [PATCH v4 1/6] string_helpers: add kstrdup

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Date:	Tue, 12 Apr 2016 16:13:00 -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 1/6] string_helpers: add kstrdup_quotable

Quoting Kees Cook (keescook@...omium.org):
> Handle allocating and escaping a string safe for logging.
> 
> Signed-off-by: Kees Cook <keescook@...omium.org>

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

> ---
>  include/linux/string_helpers.h |  2 ++
>  lib/string_helpers.c           | 28 ++++++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
> 
> diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
> index dabe643eb5fa..9de228af00c1 100644
> --- a/include/linux/string_helpers.h
> +++ b/include/linux/string_helpers.h
> @@ -68,4 +68,6 @@ static inline int string_escape_str_any_np(const char *src, char *dst,
>  	return string_escape_str(src, dst, sz, ESCAPE_ANY_NP, only);
>  }
>  
> +char *kstrdup_quotable(const char *src, gfp_t gfp);
> +
>  #endif
> diff --git a/lib/string_helpers.c b/lib/string_helpers.c
> index 5c88204b6f1f..aa00c9f989ee 100644
> --- a/lib/string_helpers.c
> +++ b/lib/string_helpers.c
> @@ -10,6 +10,7 @@
>  #include <linux/export.h>
>  #include <linux/ctype.h>
>  #include <linux/errno.h>
> +#include <linux/slab.h>
>  #include <linux/string.h>
>  #include <linux/string_helpers.h>
>  
> @@ -534,3 +535,30 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
>  	return p - dst;
>  }
>  EXPORT_SYMBOL(string_escape_mem);
> +
> +/*
> + * Return an allocated string that has been escaped of special characters
> + * and double quotes, making it safe to log in quotes.
> + */
> +char *kstrdup_quotable(const char *src, gfp_t gfp)
> +{
> +	size_t slen, dlen;
> +	char *dst;
> +	const int flags = ESCAPE_HEX;
> +	const char esc[] = "\f\n\r\t\v\a\e\\\"";
> +
> +	if (!src)
> +		return NULL;
> +	slen = strlen(src);
> +
> +	dlen = string_escape_mem(src, slen, NULL, 0, flags, esc);
> +	dst = kmalloc(dlen + 1, gfp);
> +	if (!dst)
> +		return NULL;
> +
> +	WARN_ON(string_escape_mem(src, slen, dst, dlen, flags, esc) != dlen);
> +	dst[dlen] = '\0';
> +
> +	return dst;
> +}
> +EXPORT_SYMBOL_GPL(kstrdup_quotable);
> -- 
> 2.6.3