nvme-pci: NULL pointer dereference in nvme_dev_disable() on linux-next

[Keith Busch]

On Tue, Nov 08, 2022 at 08:48:47AM +0100, Christoph Hellwig wrote:
> Below is the minimal fix.  I'll see if I sort out the mess that is
> probe/reset failure vs ->remove a bit better, though.

This looks good to go. I vote apply for 6.1, and we should consider
merging your larger refactor for 6.2 after more test/review.

Reviewed-by: Keith Busch <kbusch at kernel.org>
 
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index f94b05c585cbc..577bacdcfee08 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -5160,6 +5160,8 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
>  
>  void nvme_stop_queues(struct nvme_ctrl *ctrl)
>  {
> +	if (!ctrl->tagset)
> +		return;
>  	if (!test_and_set_bit(NVME_CTRL_STOPPED, &ctrl->flags))
>  		blk_mq_quiesce_tagset(ctrl->tagset);
>  	else
> @@ -5169,6 +5171,8 @@ EXPORT_SYMBOL_GPL(nvme_stop_queues);
>  
>  void nvme_start_queues(struct nvme_ctrl *ctrl)
>  {
> +	if (!ctrl->tagset)
> +		return;
>  	if (test_and_clear_bit(NVME_CTRL_STOPPED, &ctrl->flags))
>  		blk_mq_unquiesce_tagset(ctrl->tagset);
>  }
>