[PATCH] nvme: fix NULL pointer dereference

[Keith Busch]

On Wed, Sep 16, 2020 at 11:36:49AM -0400, Tong Zhang wrote:
> @@ -960,6 +960,8 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
>  	}
>  
>  	req = blk_mq_tag_to_rq(nvme_queue_tagset(nvmeq), cqe->command_id);
> +	if (!req)
> +		return;

As I mentioned before, blk_mq_tag_to_rq() returns NULL if the tag
exceeds the depth. We already verify the tag prior to calling this
function, so what's the real root cause for how we're winding up with
NULL here? I'm only asking this because it sounds like there's a bug
somewhere else and this change is masking over it.


>  	trace_nvme_sq(req, cqe->sq_head, nvmeq->sq_tail);
>  	if (!nvme_try_complete_req(req, cqe->status, cqe->result))
>  		nvme_pci_complete_rq(req);