linux-kernel - Re: kernel BUG at fs/sysfs/group.c:65!

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Message-ID: <20130310164102.GD4392@kroah.com>
Date:	Sun, 10 Mar 2013 09:41:02 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Tommi Rantala <tt.rantala@...il.com>, Jens Axboe <axboe@...nel.dk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Guo Chao <yan@...ux.vnet.ibm.com>, Tejun Heo <tj@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: kernel BUG at fs/sysfs/group.c:65!

On Sun, Mar 10, 2013 at 04:53:11PM +0800, Ming Lei wrote:
> On Sun, Mar 10, 2013 at 12:36 AM, Tommi Rantala <tt.rantala@...il.com> wrote:
> > [   40.089036]  [<ffffffff81222e29>] sysfs_get_dirent+0x39/0x80
> > [   40.089036]  [<ffffffff81224ad9>] sysfs_remove_group+0x29/0x100
> > [   40.089036]  [<ffffffff8113f2c4>] blk_trace_remove_sysfs+0x14/0x20
> > [   40.089036]  [<ffffffff813453ae>] blk_unregister_queue+0x5e/0x90
> > [   40.089036]  [<ffffffff8134d417>] del_gendisk+0x107/0x250
> > [   40.089036]  [<ffffffff814f66b8>] loop_remove+0x18/0x40
> 
> Then the crash is triggered in device release path, which should have
> been avoided in device add path.
> 
> If we want to fix the problem completely, add_disk() must handle failure
> path correctly and return error code on failures, which may involve big
> work, since add_disk() are called by 50+ drivers.

Ok, but the root problem here is add_disk() is being called to create a
disk that was already created, right?  Surely the caller should have
detected this before it called to the block core?

Who is calling add_disk() here?  Is this a fuse device?  If so, then any
user can trigger this, right?

That should be the "easier" fix at the moment to resolve this issue.

greg k-h
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