From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Message-ID: <520E58F3.4080309@nod.at> Date: Fri, 16 Aug 2013 18:53:07 +0200 From: Richard Weinberger MIME-Version: 1.0 References: <1376668606-32354-1-git-send-email-richard@nod.at> <20130816161229.GI2505@htj.dyndns.org> <520E500B.5000408@nod.at> <20130816162844.GJ2505@htj.dyndns.org> <520E55A2.9080900@nod.at> <20130816164544.GK2505@htj.dyndns.org> In-Reply-To: <20130816164544.GK2505@htj.dyndns.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Subject: Re: [PATCH] print_worker_info: Handle pointer with more care To: Tejun Heo Cc: linux-kernel@vger.kernel.org, Jeff Dike , user-mode-linux-devel@lists.sourceforge.net List-ID: Am 16.08.2013 18:45, schrieb Tejun Heo: > Hello, > > On Fri, Aug 16, 2013 at 06:38:58PM +0200, Richard Weinberger wrote: >>> 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()? >> >> You are already talking to UML people. ;) > > Ooh... :) > >> Anyway, I'll investigate into that. >> What I see so far is that pwq is NULL after probe_kernel_read(). > > Yeah, and that should be fine. &pwq->wq would be just an offset of wq Yep. Now my brain also parsed the C notation correctly. Sorry for the completely wrong patch. > from NULL which is an invalid pointer but probe_kernel_read() should > be able to handle that and probably just return 0 or -1 (all bits > set). I *think* what's necessary is making probe_kernel_read() use > mincore() to fine out whether the requested address is mapped (it > should return -EFAULT if not) and try to dereference the address iff > it's mapped. UML needs a custom probe_kernel_read()? Fine. :) Thanks, //richard