From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753403Ab3HPQ24 (ORCPT ); Fri, 16 Aug 2013 12:28:56 -0400 Received: from mail-qc0-f178.google.com ([209.85.216.178]:46480 "EHLO mail-qc0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751575Ab3HPQ2w (ORCPT ); Fri, 16 Aug 2013 12:28:52 -0400 Date: Fri, 16 Aug 2013 12:28:44 -0400 From: Tejun Heo To: Richard Weinberger Cc: linux-kernel@vger.kernel.org, Jeff Dike , Richard Weinberger , user-mode-linux-devel@lists.sourceforge.net Subject: Re: [PATCH] print_worker_info: Handle pointer with more care Message-ID: <20130816162844.GJ2505@htj.dyndns.org> References: <1376668606-32354-1-git-send-email-richard@nod.at> <20130816161229.GI2505@htj.dyndns.org> <520E500B.5000408@nod.at> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <520E500B.5000408@nod.at> 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 Fri, Aug 16, 2013 at 06:15:07PM +0200, Richard Weinberger wrote: > On UML I hit the case that pwq is NULL. > Then we oops at &pwq->wq... Hmmm? I'm confused. &pwq->wq is pwq's pointer + wq's offset in pwq. It doesn't involve dereferencing pwq->wq. Maybe uml isn't implementing probe_kernel_thread()? Now that I think about it, I'm not sure how it could. cc'ing uml people. Hey, guys, workqueue uses proble_kernel_read() to print out workqueue related information during oops because those events are completely asynchronous and workqueue states may not be consistently accessible. It seems like uml doesn't implement probe_kernel_read() and tries direct derference of incorrect pointers leading to its own oops. Maybe uml should check whether the memory is mapped from probe_kernel_read()? Thanks. -- tejun