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From: Matthias Andree <matthias.andree@gmx.de>
To: Kris Kennaway <kris@obsecurity.org>
In-Reply-To: <20050830232818.GA83944@xor.obsecurity.org> (Kris Kennaway's
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Date: Wed, 31 Aug 2005 12:12:11 +0200
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Cc: Matthias Andree <matthias.andree@gmx.de>,
	Jeremie Le Hen <jeremie@le-hen.org>, freebsd-current@freebsd.org
Subject: Re: nfs through nullfs
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Kris Kennaway <kris@obsecurity.org> writes:

> On Tue, Aug 30, 2005 at 02:44:35PM +0200, Jeremie Le Hen wrote:
>> > Subject says it all.
>> > 
>> > mount a ext2 file system, use it as basis for a nullfs mount -> panic.
>> 
>> Mount a NFS filesystem, use it as basis for nullfs mount -> panic.
>
> Please provide details.

OK, to reproduce, three steps apart from having an ext2 file system
(the ext2 FS is clean according to e2fsck)

mount_ext2fs /dev/ad0s5 /linux
mount_nullfs /linux /mnt
umount /mnt                    -> panic, "locking against myself"

backtrace in the kernel debugger, copied manually:

kdb_enter
panic   +0x13d
lockmgr +0x44d
vop_stdlock +0x2f
VOP_LOCK_APV
vn_lock
vrele
null_reclaim
VOP_RECLAIM_APV
vgonel
vgone
vflush
nullfs_unmount
dounmount
unmount
syscall...
(process unmount)

If needed, I can save a core of this.

-- 
Matthias Andree