From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933564AbXG2SG1 (ORCPT ); Sun, 29 Jul 2007 14:06:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765241AbXG2SGO (ORCPT ); Sun, 29 Jul 2007 14:06:14 -0400 Received: from pentafluge.infradead.org ([213.146.154.40]:55496 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757404AbXG2SGN (ORCPT ); Sun, 29 Jul 2007 14:06:13 -0400 Date: Sun, 29 Jul 2007 23:48:24 +0530 (IST) From: Satyam Sharma X-X-Sender: satyam@enigma.security.iitk.ac.in To: Oliver Neukum cc: linux-usb-devel@lists.sourceforge.net, Jesper Juhl , Greg Kroah-Hartman , netdev@vger.kernel.org, Linux Kernel Mailing List , Petko Manolov Subject: Re: [linux-usb-devel] [PATCH] USB Pegasus driver - avoid a potential NULL pointer dereference. In-Reply-To: <200707291049.26619.oliver@neukum.org> Message-ID: References: <200707290019.02591.jesper.juhl@gmail.com> <9a8748490707281655u66e50bbfqba58687b579a85fe@mail.gmail.com> <200707291049.26619.oliver@neukum.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 29 Jul 2007, Oliver Neukum wrote: > Am Sonntag 29 Juli 2007 schrieb Jesper Juhl: > > 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. > > > > [...] > > > > > > 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... > > pegasus == NULL there would be a kernel bug. Silently ignoring > it, like the code now wants to do is bad. As the oops has never been > reported, I figure turning it into an explicit debugging test is overkill, > so removal seems to be the best option. Ok, thanks. Updated patch below. [PATCH] pegasus: Remove bogus checks in urb->complete() callbacks urb->complete() callbacks registered in drivers/net/usb/pegasus.c needlessly check for urb->context != NULL, but that is not possible (the only way that can be possible would be a kernel bug elsewhere, and these checks would simply end up hiding that). So let's remove the bogus checks. Signed-off-by: Satyam Sharma --- drivers/net/usb/pegasus.c | 9 +-------- 1 files changed, 1 insertions(+), 8 deletions(-) diff --git a/drivers/net/usb/pegasus.c b/drivers/net/usb/pegasus.c index a05fd97..439ef9f 100644 --- a/drivers/net/usb/pegasus.c +++ b/drivers/net/usb/pegasus.c @@ -770,9 +770,6 @@ static void write_bulk_callback(struct urb *urb) pegasus_t *pegasus = urb->context; struct net_device *net = pegasus->net; - if (!pegasus) - return; - if (!netif_device_present(net) || !netif_running(net)) return; @@ -805,13 +802,9 @@ static void write_bulk_callback(struct urb *urb) static void intr_callback(struct urb *urb) { pegasus_t *pegasus = urb->context; - struct net_device *net; + struct net_device *net = pegasus->net; int status; - if (!pegasus) - return; - net = pegasus->net; - switch (urb->status) { case 0: break;