Re: [PATCH v2 1/5] string_helpers: add kstrdup_quotable

[Kees Cook]

On Mon, Mar 28, 2016 at 4:30 PM, Joe Perches <joe@xxxxxxxxxxx> wrote:
> On Mon, 2016-03-28 at 14:14 -0700, Kees Cook wrote:
>> Handle allocating and escaping a string safe for logging.
> []
>> diff --git 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(char *src);
>
> char *kstrdup_quotable(const char *src)
>
> but shouldn't this really take a gfp_t like all
> the other kstr<string> functions?

Ah, good idea, yes. I'll add this.

>> diff --git a/lib/string_helpers.c b/lib/string_helpers.c
> []
>> +char *kstrdup_quotable(char *src)
> []
>> +     BUG_ON(string_escape_mem(src, slen, dst, dlen, flags, esc) != dlen);
>
> BUG_ON?  why?

I was thinking that if the string_escape_mem output length changes
between calls, something has gone terribly wrong internally, and we
should stop. But, since we're limited to dlen, it'll be a truncation
at worst. I will change this to WARN_ON, which is what kasprintf does.

Thanks!

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security