Re: 2.6.15 OOPS while trying to mount cdrom

[Helge Hafting]

Chuck Ebbert wrote:

> In-Reply-To: <20060110184624.GA6721@xxxxxxxxxxxxx>
>
> 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: 
> > <ffffffff80235a92>{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).
>  
Correct - much later I discovered that.  "sync" and another "mount"
hung in D-state, so I rebooted.  I am now running without ide-scsi
and have no problem using cd's. :-)

Helge Hafting
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