linux-kernel - Re: [PATCH] char: hw_random: core.c: Changed from using strncpy to strlcpy

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Date:	Sat, 11 Oct 2014 19:11:22 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Mark D Rustad <mrustad@...il.com>
Cc:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	Matt Mackall <mpm@...enic.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Torsten Duwe <duwe@....de>, Theodore Ts'o <tytso@....edu>,
	Jason Cooper <jason@...edaemon.net>,
	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] char: hw_random: core.c:  Changed from using strncpy to
 strlcpy

On Sat, Oct 11, 2014 at 05:27:41PM -0700, Mark D Rustad wrote:
> On Oct 11, 2014, at 3:36 PM, Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se> wrote:
> 
> > Changed from using strncpy to strlcpy to simplify the code
> 
> Actually you changed from using strncat to strlcat.
> 
... and changed the length parameter along the way, making the length check
overall quite worthless and introducing a _real_ problem.

Guenter

> > Signed-off-by: Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>
> > ---
> > 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
> 
> -- 
> Mark Rustad, MRustad@...il.com
> 


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