linux-kernel - Re: [PATCH 3v] char: hw_random: core.c: Changed from using strncat to strlcat

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Message-ID: <20141016175358.GN17447@titan.lakedaemon.net>
Date:	Thu, 16 Oct 2014 13:53:58 -0400
From:	Jason Cooper <jason@...edaemon.net>
To:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
Cc:	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Torsten Duwe <duwe@....de>, Theodore Ts'o <tytso@....edu>,
	Amit Shah <amit.shah@...hat.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Kees Cook <keescook@...omium.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3v] char: hw_random: core.c:  Changed from using
 strncat to strlcat

On Thu, Oct 16, 2014 at 07:15:22PM +0200, Rickard Strandqvist wrote:
> The buf is used to hold the list of hwrng devices registered.
> The old code ensures we don't walk off the end of buf as we
> fill it, but it's unnecessarily complicated and thus difficult
> to maintain. Simplify it by using strlcat.
> We also ensure the string within buf is NULL terminated
> so the final strlen is ok.
> 
> Signed-off-by: Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>

Reviewed-by: Jason Cooper <jason@...edaemon.net>

thx,

Jason.

> ---
>  drivers/char/hw_random/core.c |   12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c
> index aa30a25..1500cfd 100644
> --- a/drivers/char/hw_random/core.c
> +++ b/drivers/char/hw_random/core.c
> @@ -281,7 +281,6 @@ static ssize_t hwrng_attr_available_show(struct device *dev,
>  					 char *buf)
>  {
>  	int err;
> -	ssize_t ret = 0;
>  	struct hwrng *rng;
>  
>  	err = mutex_lock_interruptible(&rng_mutex);
> @@ -289,16 +288,13 @@ static ssize_t hwrng_attr_available_show(struct device *dev,
>  		return -ERESTARTSYS;
>  	buf[0] = '\0';
>  	list_for_each_entry(rng, &rng_list, list) {
> -		strncat(buf, rng->name, PAGE_SIZE - ret - 1);
> -		ret += strlen(rng->name);
> -		strncat(buf, " ", PAGE_SIZE - ret - 1);
> -		ret++;
> +		strlcat(buf, rng->name, PAGE_SIZE);
> +		strlcat(buf, " ", PAGE_SIZE);
>  	}
> -	strncat(buf, "\n", PAGE_SIZE - ret - 1);
> -	ret++;
> +	strlcat(buf, "\n", PAGE_SIZE);
>  	mutex_unlock(&rng_mutex);
>  
> -	return ret;
> +	return strlen(buf);
>  }
>  
>  static DEVICE_ATTR(rng_current, S_IRUGO | S_IWUSR,
> -- 
> 1.7.10.4
> 
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