Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754468AbaJMPzv (ORCPT ); Mon, 13 Oct 2014 11:55:51 -0400 Received: from mho-02-ewr.mailhop.org ([204.13.248.72]:11473 "EHLO mho-02-ewr.mailhop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753286AbaJMPzt (ORCPT ); Mon, 13 Oct 2014 11:55:49 -0400 X-Mail-Handler: Dyn Standard SMTP by Dyn X-Originating-IP: 96.249.243.124 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX18IKfCfeQgGUj5HFirEKweq2wM2tdcjpnE= X-DKIM: OpenDKIM Filter v2.0.1 titan 663985FCDEF Date: Sun, 12 Oct 2014 15:22:09 -0400 From: Jason Cooper To: Rickard Strandqvist Cc: Matt Mackall , Herbert Xu , Torsten Duwe , "Theodore Ts'o" , Amit Shah , Stephen Boyd , Paul Gortmaker , Kees Cook , Dan Carpenter , linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] char: hw_random: core.c: Changed from using strncat to strlcat Message-ID: <20141012192209.GC14147@titan.lakedaemon.net> References: <1413110971-17392-1-git-send-email-rickard_strandqvist@spectrumdigital.se> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1413110971-17392-1-git-send-email-rickard_strandqvist@spectrumdigital.se> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Rickard, On Sun, Oct 12, 2014 at 12:49:31PM +0200, Rickard Strandqvist wrote: > Changed from using strncat to strlcat to simplify the code I'd like to see a little more explicit discussion here. As Guenter got caught up in the mis-understanding, I doubt he'd be the only one. I think it's worth spelling out that the old code prevents overflowing the buffer 'buf' of size PAGE_SIZE. And that strlcat() does that internally allowing this code to be more readable. It should also be mentioned that the final strlen(buf) is safe because every operation on buf will insert a NULL terminator within the buffers limit. thx, Jason. > Signed-off-by: Rickard Strandqvist > --- > 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 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/