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

From: Guenter Roeck
Date: Sat Oct 11 2014 - 22:11:50 EST


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@xxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxxx>
> > ---
> > 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@xxxxxxxxx
>


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