From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752144Ab1GKJjN (ORCPT ); Mon, 11 Jul 2011 05:39:13 -0400 Received: from mail-iy0-f174.google.com ([209.85.210.174]:51796 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750870Ab1GKJjL (ORCPT ); Mon, 11 Jul 2011 05:39:11 -0400 Date: Mon, 11 Jul 2011 17:36:51 +0800 From: wangyanqing To: Jesper Juhl Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] USB: Avoid NULL pointer dereference in usb_disconnect() Message-ID: <20110711093651.GA10217@udknight> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 11, 2011 at 11:21:18AM +0200, Jesper Juhl wrote: > If, in drivers/usb/core/hub.c::usb_disconnect(), 'udev' is NULL, then > we'll never get to the printing of a debug message and returning from > the function since we'll have already dereferenced the NULL pointer in > the bus_to_hcd(udev->bus) call. > This patch moves the dereference to after the test for NULL, thus > avoiding that potential crash. > > Signed-off-by: Jesper Juhl > --- > drivers/usb/core/hub.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > disclaimer: compile tested only. > > diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c > index a428aa0..0a98c76 100644 > --- a/drivers/usb/core/hub.c > +++ b/drivers/usb/core/hub.c > @@ -1634,13 +1634,15 @@ void usb_disconnect(struct usb_device **pdev) > { > struct usb_device *udev = *pdev; > int i; > - struct usb_hcd *hcd = bus_to_hcd(udev->bus); > + struct usb_hcd *hcd; > > if (!udev) { > pr_debug ("%s nodev\n", __func__); > return; > } > > + hcd = bus_to_hcd(udev->bus); > + > /* mark the device as inactive, so any further urb submissions for > * this device (and any of its children) will fail immediately. > * this quiesces everything except pending urbs. > -- > 1.7.6 > > > -- > Jesper Juhl http://www.chaosbits.net/ > Don't top-post http://www.catb.org/jargon/html/T/top-post.html > Plain text mails only, please. > > -- > 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/ Hello,All.Just a question,should we add the NULL checker code at everywhere that dereference pointer in kernel? If so,it will scare me.