From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Jesper Juhl" Subject: Re: [PATCH] USB Pegasus driver - avoid a potential NULL pointer dereference. Date: Sun, 29 Jul 2007 01:55:00 +0200 Message-ID: <9a8748490707281655u66e50bbfqba58687b579a85fe@mail.gmail.com> References: <200707290019.02591.jesper.juhl@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Greg Kroah-Hartman , netdev@vger.kernel.org, Linux Kernel Mailing List , Petko Manolov , linux-usb-devel@lists.sourceforge.net To: "Satyam Sharma" Return-path: In-Reply-To: Content-Disposition: inline List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-usb-devel-bounces@lists.sourceforge.net Errors-To: linux-usb-devel-bounces@lists.sourceforge.net List-Id: netdev.vger.kernel.org On 29/07/07, Satyam Sharma wrote: > Hi, > > On 7/29/07, Jesper Juhl wrote: > > Hello, > > > > This patch makes sure we don't dereference a NULL pointer in > > drivers/net/usb/pegasus.c::write_bulk_callback() in the initial > > struct net_device *net = pegasus->net; assignment. > > The existing code checks if 'pegasus' is NULL and bails out if > > it is, so we better not touch that pointer until after that check. > > [...] > > diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c > > index a05fd97..04cba6b 100644 > > --- a/drivers/net/usb/pegasus.c > > +++ b/drivers/net/usb/pegasus.c > > @@ -768,11 +768,13 @@ done: > > static void write_bulk_callback(struct urb *urb) > > { > > pegasus_t *pegasus = urb->context; > > - struct net_device *net = pegasus->net; > > + struct net_device *net; > > > > if (!pegasus) > > return; > > > > + net = pegasus->net; > > + > > if (!netif_device_present(net) || !netif_running(net)) > > return; > > Is it really possible that we're called into this function with > urb->context == NULL? If not, I'd suggest let's just get rid of > the check itself, instead. > I'm not sure. I am not very familiar with this code. I just figured that moving the assignment is potentially a little safer and it is certainly no worse than the current code, so that's a safe and potentially benneficial change. Removing the check may be safe but I'm not certain enough to make that call... -- Jesper Juhl Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html Plain text mails only, please http://www.expita.com/nomime.html ------------------------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Still grepping through log files to find problems? Stop. Now Search log events and configuration files using AJAX and a browser. Download your FREE copy of Splunk now >> http://get.splunk.com/ _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel