nvme-pci: avoid dereference of symbol from unloaded module

The 'remove_work' may be scheduled to run after nvme_remove()
returns since we can't simply cancel it in nvme_remove() for
avoiding deadlock. Once nvme_remove() returns, this module(nvme)
can be unloaded.

On the other hand, nvme_put_ctrl() calls ctr->ops->free_ctrl
which may point to nvme_pci_free_ctrl() in unloaded module.

This patch avoids this issue by queuing 'remove_work' via 'nvme_wq',
and flush this worqueue in nvme_exit() as suggested by Sagi.

Suggested-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Keith Busch <keith.busch@intel.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 429d56f1a19e8b11f1124e023bb453a8f2c81a59..762b8402e04c591df728e6e5e5bffa16ccf0d907 100644 (file)
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -2280,7 +2280,7 @@ static void nvme_remove_dead_ctrl(struct nvme_dev *dev, int status)
 
        nvme_get_ctrl(&dev->ctrl);
        nvme_dev_disable(dev, false);
-       if (!schedule_work(&dev->remove_work))
+       if (!queue_work(nvme_wq, &dev->remove_work))
                nvme_put_ctrl(&dev->ctrl);
 }
 
@@ -2703,6 +2703,7 @@ static int __init nvme_init(void)
 static void __exit nvme_exit(void)
 {
        pci_unregister_driver(&nvme_driver);
+       flush_workqueue(nvme_wq);
        _nvme_check_size();
 }