Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755051Ab1DTOeI (ORCPT ); Wed, 20 Apr 2011 10:34:08 -0400 Received: from kroah.org ([198.145.64.141]:43683 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753379Ab1DTOeD (ORCPT ); Wed, 20 Apr 2011 10:34:03 -0400 Date: Wed, 20 Apr 2011 07:34:35 -0700 From: Greg KH To: Amit Shah Cc: Milton Miller , Rusty Russell , linux-kernel@vger.kernel.org, benh@kernel.crashing.org, linuxppc-dev@ozlabs.org Subject: Re: hvc_console: Don't access hvc_task if not initialised Message-ID: <20110420143435.GB22436@kroah.com> References: <20110325084714.GA28356@amit-x200.redhat.com> <20110420123330.GB3519@amit-x200.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110420123330.GB3519@amit-x200.redhat.com> 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 Content-Length: 1618 Lines: 43 On Wed, Apr 20, 2011 at 06:03:30PM +0530, Amit Shah wrote: > On (Mon) 28 Mar 2011 [11:52:05], Milton Miller wrote: > > On Fri, 25 Mar 2011 about 14:17:14 +0530, Amit Shah wrote: > > > On (Thu) 24 Mar 2011 [08:58:04], Milton Miller wrote: > > > > On Thu, 24 Mar 2011 07:29:58 -0000, Amit Shah wrote: > > > > > hvc_open() can be called without having any backing device. This > > > > > results in a call to hvc_kick() which calls wake_up_process on a NULL > > > > > pointer. > > > > > > > > How is hvc_open called without a hvc_driver registered to the tty layer? > > > > > > This gets reproduced in a couple of scenarios, I'm trying to get more > > > information. > > OK - I finally could reproduce myself, albiet it's a panic in > hvc_open, not the one mentioned earlier. > > hvc_console is built into the kernel and virtio_console is a module. > This sequence triggers a panic: > > - modprobe virtio_console > - agetty /dev/hvc0 9600 vt100 > - rmmod virtio_console > - modprobe virtio_console > - agetty /dev/hvc0 9600 vt100 > > A patch that I had sent previously, to hvc_remove() a port when the > associated virtio_console port gets unplugged, fixes this panic. > > Stricter checking in hvc_open(), as you mentioned, will solve the > other one as well. Care to either create this patch, or resend your original one, if you want it applied? thanks, greg k-h -- 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/