From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161461AbWALXS5 (ORCPT ); Thu, 12 Jan 2006 18:18:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161462AbWALXS5 (ORCPT ); Thu, 12 Jan 2006 18:18:57 -0500 Received: from liaag1ad.mx.compuserve.com ([149.174.40.30]:62898 "EHLO liaag1ad.mx.compuserve.com") by vger.kernel.org with ESMTP id S1161461AbWALXS4 (ORCPT ); Thu, 12 Jan 2006 18:18:56 -0500 Date: Thu, 12 Jan 2006 18:14:55 -0500 From: Chuck Ebbert <76306.1226@compuserve.com> Subject: Re: 2.6.15 OOPS while trying to mount cdrom To: Helge Hafting Cc: Greg KH , linux-kernel , Bartlomiej Zolnierkiewicz Message-ID: <200601121818_MC3-1-B5C5-46C7@compuserve.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org In-Reply-To: <20060110184624.GA6721@aitel.hist.no> On Tue, 10 Jan 2006 Helge Hafting wrote: > Kernel 2.6.15 amd64, gcc 4.1.0 from debian. > > The cdrom (/dev/hda) is usually fine. I tried booting with > hda=ide-scsi in order to read a scratched audio cd with cdparanoia. > That way, I at least get error messages when the scratches are > too bad. > > I forgot about hda=ide-scsi, and tried to mount /dev/hda as > usual in order to read an ordinary iso9660 cd. This is > probably not supposed to work when ide-scsi is using the device, > but then I expect something like EBUSY rather than this oops: > > ide-scsi: unsup command: dev hda: flags = REQ_SORTED REQ_CMD REQ_STARTED > REQ_ELVPRIV > sector 64, nr/cnr 2/2 > bio ffff8100044a9b40, biotail ffff8100044a9b40, buffer ffff81000cb4d000, data > 0000000000000000, len 0 > end_request: I/O error, dev hda, sector 64 > isofs_fill_super: bread failed, dev=hda, iso_blknum=16, block=32 > Unable to handle kernel NULL pointer dereference at 0000000000000000 RIP: > {strlen+2} The IDE driver probably shouldn't have allowed the bdev to be opened in the first place. After that happened, mount attempted to fill the superblock and the I/O failed. Upon failure, get_sb_bdev() called deactivate_super() (fs/super.c line 718) and all hell broke loose. - deactivate_super() called fs->kill_sb() (super.c line 176) which pointed to kill_block_super() (fs/isofs/inode.c line 1411) - kill_block_super() called kobject_uevent() with action KOBJ_UMOUNT (Question: why is it sending UMOUNT for a mount that never happened?) - kobject_uevent() called kobject_get_path() and one of the objects had a null kobject.name, which caused strlen() to oops. There seem to be several bugs here: (1) IDE shouldn't have allowed the bdev to be opened. (2) (maybe) kobject_uevent shouldn't have been called for an unmount event when the mount never succeeded. (3) kobject_get_path() shouldn't oops when a path component has a NULL name, or else kobject should fail registration of any such object. > The pc didn't seem to malfunction after this. If you attempt to mount the CD a second time, mount will hang in D state; ps(1) reports it's at text.lock.super. System cannot be cleanly shut down after that -- shutdown(8) hangs and so does sync(1). -- Chuck Currently reading: _Olympos_ by Dan Simmons