Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933778AbXK2UZY (ORCPT ); Thu, 29 Nov 2007 15:25:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932196AbXK2UZI (ORCPT ); Thu, 29 Nov 2007 15:25:08 -0500 Received: from rtr.ca ([76.10.145.34]:2814 "EHLO mail.rtr.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932419AbXK2UZH (ORCPT ); Thu, 29 Nov 2007 15:25:07 -0500 Message-ID: <474F2020.7020004@rtr.ca> Date: Thu, 29 Nov 2007 15:25:04 -0500 From: Mark Lord User-Agent: Thunderbird 2.0.0.9 (X11/20071031) MIME-Version: 1.0 To: Greg KH Cc: Alan Stern , Andrew Morton , Linus Torvalds , linux-usb-devel@lists.sourceforge.net, Linux Kernel Subject: Re: [linux-usb-devel] [PATCH] base/class.c: prevent ooops due to insert/remove race (v3) References: <474F1AAC.7040908@rtr.ca> <20071129201224.GA25356@suse.de> <474F1DB3.4030900@rtr.ca> In-Reply-To: <474F1DB3.4030900@rtr.ca> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2148 Lines: 70 (resending .. somebody trimmed the CC: list earlier) Greg KH wrote: >>>> Mark Lord wrote: >>>>> .. >>>>> >>>>> While doing insert/remove (quickly) tests on USB, >>>>> I managed to trigger an Oops on 2.6.23.8 on a call >>>>> to strlen() in make_class_name(). ... > I'll hold off on adding this patch for now. .. Why? Bugs that result in Oops in core code (class.c) can bite just about any subsystem that does hotplug, and should get prompt attention. Or so one might think. * * * * Patch reproduced below for full CC: While doing insert/remove (quickly) tests on USB, I managed to trigger an Oops on 2.6.23.1 on the call to strlen() in make_class_name(). This patch prevents the oops, but still keeps the bug visible. There is still the larger problem of the overall race that caused this in the first place, but much of the rest of the code in class.c appears to also do NULL checks to avoid Oops'ing, so this continues the tradition. Signed-off-by: Mark Lord --- Patch applies to both 2.6.24 and 2.6.23. --- old/drivers/base/class.c 2007-11-29 10:51:43.000000000 -0500 +++ linux/drivers/base/class.c 2007-11-29 13:00:15.000000000 -0500 @@ -352,9 +352,22 @@ char *make_class_name(const char *name, struct kobject *kobj) { char *class_name; + const char *kname; int size; - size = strlen(name) + strlen(kobject_name(kobj)) + 2; + /* Rapidly inserting/removing a USB device (others?) + * can trigger an Oops on the strlen() call. + * Cause unknown yet, so prevent the Oops + * but don't mask the issue. + */ + kname = kobject_name(kobj); + if (!kname || !name) { + printk(KERN_ERR "make_class_name: name=%p kname=%p\n", + name, kname); + BUG_ON(1); + return NULL; + } + size = strlen(name) + strlen(kname) + 2; class_name = kmalloc(size, GFP_KERNEL); if (!class_name) - 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/