Merge branch 'nvme-4.19' of git://git.infradead.org/nvme into for-linus

Pull single NVMe fix from Christoph.

* 'nvme-4.19' of git://git.infradead.org/nvme:
  nvmet-rdma: fix possible bogus dereference under heavy load

drivers/nvme/target/rdma.c

@@ -66,6 +66,7 @@ struct nvmet_rdma_rsp {
 
 	struct nvmet_req	req;
 
+	bool			allocated;
 	u8			n_rdma;
 	u32			flags;
 	u32			invalidate_rkey;
@@ -174,11 +175,19 @@ nvmet_rdma_get_rsp(struct nvmet_rdma_queue *queue)
 	unsigned long flags;
 
 	spin_lock_irqsave(&queue->rsps_lock, flags);
-	rsp = list_first_entry(&queue->free_rsps,
+	rsp = list_first_entry_or_null(&queue->free_rsps,
 				struct nvmet_rdma_rsp, free_list);
+	if (likely(rsp))
 		list_del(&rsp->free_list);
 	spin_unlock_irqrestore(&queue->rsps_lock, flags);
 
+	if (unlikely(!rsp)) {
+		rsp = kmalloc(sizeof(*rsp), GFP_KERNEL);
+		if (unlikely(!rsp))
+			return NULL;
+		rsp->allocated = true;
+	}
+
 	return rsp;
 }
 
@@ -187,6 +196,11 @@ nvmet_rdma_put_rsp(struct nvmet_rdma_rsp *rsp)
 {
 	unsigned long flags;
 
+	if (rsp->allocated) {
+		kfree(rsp);
+		return;
+	}
+
 	spin_lock_irqsave(&rsp->queue->rsps_lock, flags);
 	list_add_tail(&rsp->free_list, &rsp->queue->free_rsps);
 	spin_unlock_irqrestore(&rsp->queue->rsps_lock, flags);
@@ -776,6 +790,15 @@ static void nvmet_rdma_recv_done(struct ib_cq *cq, struct ib_wc *wc)
 
 	cmd->queue = queue;
 	rsp = nvmet_rdma_get_rsp(queue);
+	if (unlikely(!rsp)) {
+		/*
+		 * we get here only under memory pressure,
+		 * silently drop and have the host retry
+		 * as we can't even fail it.
+		 */
+		nvmet_rdma_post_recv(queue->dev, cmd);
+		return;
+	}
 	rsp->queue = queue;
 	rsp->cmd = cmd;
 	rsp->flags = 0;