linux-kernel - Re: [PATCH] loop: queue_lock NULL pointer derefence in blk_throtl

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Message-ID: <4D3782BB.9080705@fusionio.com>
Date:	Wed, 19 Jan 2011 17:32:59 -0700
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
CC:	Philipp Reisner <philipp.reisner@...bit.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lars Ellenberg <lars.ellenberg@...bit.com>,
	"Stephen M. Cameron" <scameron@...rdog.cce.hp.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] loop: queue_lock NULL pointer derefence in blk_throtl_exit

On 2011-01-14 12:25, Sergey Senozhatsky wrote:
> Performing 
> $ sudo mount -o loop -o umask=0 /dev/sdb1 /mnt/
> mount: wrong fs type, bad option, bad superblock on /dev/loop0,
>        missing codepage or helper program, or other error
>        In some cases useful info is found in syslog - try
>        dmesg | tail  or so
> 
> $ sudo modprobe -r loop
> 
> results in oops:
> 
>  BUG: unable to handle kernel NULL pointer dereference at 0000000000000004
>  IP: [<ffffffff812479d4>] do_raw_spin_lock+0x14/0x122
>  Process modprobe (pid: 6189, threadinfo ffff88009a898000, task ffff880154a88000)
>  Call Trace:
>   [<ffffffff81486788>] _raw_spin_lock_irq+0x4a/0x51
>   [<ffffffff8123404b>] ? blk_throtl_exit+0x3b/0xa0
>   [<ffffffff8105b120>] ? cancel_delayed_work_sync+0xd/0xf
>   [<ffffffff8123404b>] blk_throtl_exit+0x3b/0xa0
>   [<ffffffff81229bc8>] blk_release_queue+0x21/0x65
>   [<ffffffff8123bb06>] kobject_release+0x51/0x66
>   [<ffffffff8123bab5>] ? kobject_release+0x0/0x66
>   [<ffffffff8123ce1e>] kref_put+0x43/0x4d
>   [<ffffffff8123ba27>] kobject_put+0x47/0x4b
>   [<ffffffff8122717c>] blk_cleanup_queue+0x56/0x5b
>   [<ffffffffa01c3824>] loop_exit+0x68/0x844 [loop]
>   [<ffffffff8107cccc>] sys_delete_module+0x1e8/0x25b
>   [<ffffffff814864c9>] ? trace_hardirqs_on_thunk+0x3a/0x3f
>   [<ffffffff81002112>] system_call_fastpath+0x16/0x1b
> 
> 
> because of an attempt to acquire NULL queue_lock.
> I added the same lines as in blk_queue_make_request - 
> `fall back to embedded per-queue lock'.

Queued up for 2.6.38, thanks.

-- 
Jens Axboe

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