Re: [PATCH v4 1/6] string_helpers: add kstrdup_quotable

["Serge E. Hallyn" <serge@hallyn.com>]

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

Acked-by: Serge Hallyn <serge.hallyn@canonical.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