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From: Sergey Senozhatsky <>
To: Jens Axboe <>
Cc: Philipp Reisner <>,
	Andrew Morton <>,
	Lars Ellenberg <>,
	"Stephen M. Cameron" <>,
Subject: [PATCH] loop: queue_lock NULL pointer derefence in blk_throtl_exit
Date: Fri, 14 Jan 2011 21:25:32 +0200	[thread overview]
Message-ID: <20110114192532.GA4274@swordfish> (raw)

$ 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'.

Signed-off-by: Sergey Senozhatsky <>


 drivers/block/loop.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 44e18c0..49e6a54 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1641,6 +1641,9 @@ out:
 static void loop_free(struct loop_device *lo)
+	if (!lo->lo_queue->queue_lock)
+		lo->lo_queue->queue_lock = &lo->lo_queue->__queue_lock;

             reply	other threads:[~2011-01-14 19:25 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-14 19:25 Sergey Senozhatsky [this message]
2011-01-20  0:32 ` Jens Axboe
2011-01-20 11:32 ` Vivek Goyal
2011-01-20 12:58   ` [PATCH] loop: queue_lock NULL pointer derefence in blk_throtl_exit (v2) Sergey Senozhatsky
2011-01-20 14:35     ` Vivek Goyal
2011-01-20 15:18       ` Sergey Senozhatsky
2011-01-20 15:43         ` Vivek Goyal
2011-01-21 12:55           ` [PATCH] loop: queue_lock NULL pointer derefence in blk_throtl_exit (v3) Sergey Senozhatsky

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