Messages in this thread | | | Date | Thu, 16 Aug 2012 07:52:35 +0000 | From | Bart Van Assche <> | Subject | Re: [PATCH RESEND] remove the queue unlock in scsi_requset_fn |
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On 08/16/12 01:35, Chanho Min wrote: >> functions will occur in line. I also don't see why the sdev reference >> couldn't drop to zero here. > scsi_request_fn is called under the lock of request_queue->queue_lock. > If we drop the sdev reference to zero here, > scsi_device_dev_release_usercontext is > invoked and make request_queue to NULL. When caller of scsi_request_fn try to > unlock request_queue->queue_lock, the oops is occurred.
Whether or not your patch is applied, if the put_device() call in scsi_request_fn() decreases the sdev reference count to zero, the scsi_request_fn() caller will still try to unlock the queue lock after scsi_request_fn() finished and hence will trigger a use-after-free. I'm afraid the only real solution is to modify the SCSI and/or block layers such that scsi_remove_device() can't finish while scsi_request_fn() is in progress. And once that is guaranteed the get_device() / put_device() pair can be left out from scsi_request_fn().
Bart.
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