[dm-devel] [PATCH 2/2] dm: Avoid use-after-free of a mapped device
Bart Van Assche
bvanassche at acm.org
Fri Feb 22 10:47:31 UTC 2013
As the comment above rq_completed() explains, md members must
not be touched after the dm_put() at the end of that function
has been invoked. Avoid that the md->queue can be run
asynchronously after the last md reference has been dropped by
running that queue synchronously. This patch fixes the
following kernel oops:
general protection fault: 0000 [#1] SMP
RIP: 0010:[<ffffffff810fe754>] [<ffffffff810fe754>] mempool_free+0x24/0xb0
Call Trace:
<IRQ>
[<ffffffff81187417>] bio_put+0x97/0xc0
[<ffffffffa02247a5>] end_clone_bio+0x35/0x90 [dm_mod]
[<ffffffff81185efd>] bio_endio+0x1d/0x30
[<ffffffff811f03a3>] req_bio_endio.isra.51+0xa3/0xe0
[<ffffffff811f2f68>] blk_update_request+0x118/0x520
[<ffffffff811f3397>] blk_update_bidi_request+0x27/0xa0
[<ffffffff811f343c>] blk_end_bidi_request+0x2c/0x80
[<ffffffff811f34d0>] blk_end_request+0x10/0x20
[<ffffffffa000b32b>] scsi_io_completion+0xfb/0x6c0 [scsi_mod]
[<ffffffffa000107d>] scsi_finish_command+0xbd/0x120 [scsi_mod]
[<ffffffffa000b12f>] scsi_softirq_done+0x13f/0x160 [scsi_mod]
[<ffffffff811f9fd0>] blk_done_softirq+0x80/0xa0
[<ffffffff81044551>] __do_softirq+0xf1/0x250
[<ffffffff8142ee8c>] call_softirq+0x1c/0x30
[<ffffffff8100420d>] do_softirq+0x8d/0xc0
[<ffffffff81044885>] irq_exit+0xd5/0xe0
[<ffffffff8142f3e3>] do_IRQ+0x63/0xe0
[<ffffffff814257af>] common_interrupt+0x6f/0x6f
<EOI>
[<ffffffffa021737c>] srp_queuecommand+0x8c/0xcb0 [ib_srp]
[<ffffffffa0002f18>] scsi_dispatch_cmd+0x148/0x310 [scsi_mod]
[<ffffffffa000a38e>] scsi_request_fn+0x31e/0x520 [scsi_mod]
[<ffffffff811f1e57>] __blk_run_queue+0x37/0x50
[<ffffffff811f1f69>] blk_delay_work+0x29/0x40
[<ffffffff81059003>] process_one_work+0x1c3/0x5c0
[<ffffffff8105b22e>] worker_thread+0x15e/0x440
[<ffffffff8106164b>] kthread+0xdb/0xe0
[<ffffffff8142db9c>] ret_from_fork+0x7c/0xb0
Signed-off-by: Bart Van Assche <bvanassche at acm.org>
Cc: Alasdair G Kergon <agk at redhat.com>
Cc: Jens Axboe <axboe at kernel.dk>
Cc: Mike Snitzer <snitzer at redhat.com>
Cc: Tejun Heo <tj at kernel.org>
Cc: James Bottomley <JBottomley at parallels.com>
Cc: <stable at vger.kernel.org>
---
drivers/md/dm.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 314a0e2..0218fc3 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -729,13 +729,13 @@ static void rq_completed(struct mapped_device *md, int rw, int run_queue)
wake_up(&md->wait);
/*
- * Run this off this callpath, as drivers could invoke end_io while
- * inside their request_fn (and holding the queue lock). Calling
- * back into ->request_fn() could deadlock attempting to grab the
- * queue lock again.
+ * Although this function may be invoked indirectly from inside
+ * blk_run_queue(), invoking blk_run_queue() here is safe because that
+ * function returns immediately when it detects that it has been
+ * called recursively.
*/
if (run_queue)
- blk_run_queue_async(md->queue);
+ blk_run_queue(md->queue);
/*
* dm_put() must be at the end of this function. See the comment above
--
1.7.10.4
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