linux-kernel - Re: [PATCH v5 1/2] mm: add kstrimdup function

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Message-Id: <20140130132251.4f662aeddc09d8410dee4490@linux-foundation.org>
Date:	Thu, 30 Jan 2014 13:22:51 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Sebastian Capella <sebastian.capella@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-pm@...r.kernel.org, linaro-kernel@...ts.linaro.org,
	patches@...aro.org, Joe Perches <joe@...ches.com>,
	Mikulas Patocka <mpatocka@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	Shaohua Li <shli@...nel.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v5 1/2] mm: add kstrimdup function

On Thu, 30 Jan 2014 13:11:57 -0800 Sebastian Capella <sebastian.capella@...aro.org> wrote:

> kstrimdup will duplicate and trim spaces from the passed in
> null terminated string.  This is useful for strings coming from
> sysfs that often include trailing whitespace due to user input.
>
> ...
> 
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
>
> ...
>
> @@ -63,6 +64,35 @@ char *kstrndup(const char *s, size_t max, gfp_t gfp)
>  EXPORT_SYMBOL(kstrndup);
>  
>  /**
> + * kstrimdup - Trim and copy a %NUL terminated string.
> + * @s: the string to trim and duplicate
> + * @gfp: the GFP mask used in the kmalloc() call when allocating memory
> + *
> + * Returns an address, which the caller must kfree, containing
> + * a duplicate of the passed string with leading and/or trailing
> + * whitespace (as defined by isspace) removed.
> + */
> +char *kstrimdup(const char *s, gfp_t gfp)
> +{
> +	char *buf;
> +	char *begin = skip_spaces(s);
> +	size_t len = strlen(begin);
> +
> +	while (len > 1 && isspace(begin[len - 1]))
> +		len--;

That's off-by-one isn't it?  kstrimdup("   ") should return "", not " ".

> +	buf = kmalloc_track_caller(len + 1, gfp);
> +	if (!buf)
> +		return NULL;
> +
> +	memcpy(buf, begin, len);
> +	buf[len] = '\0';
> +
> +	return buf;
> +}
> +EXPORT_SYMBOL(kstrimdup);
> +

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