FAILED: patch "[PATCH] nvmet-rdma: fix null dereference under heavy load" failed to apply to 4.20-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 4.20-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 5cbab6303b4791a3e6713dfe2c5fda6a867f9adc Mon Sep 17 00:00:00 2001
From: Raju Rangoju <rajur@xxxxxxxxxxx>
Date: Thu, 3 Jan 2019 23:05:31 +0530
Subject: [PATCH] nvmet-rdma: fix null dereference under heavy load

Under heavy load if we don't have any pre-allocated rsps left, we
dynamically allocate a rsp, but we are not actually allocating memory
for nvme_completion (rsp->req.rsp). In such a case, accessing pointer
fields (req->rsp->status) in nvmet_req_init() will result in crash.

To fix this, allocate the memory for nvme_completion by calling
nvmet_rdma_alloc_rsp()

Fixes: 8407879c("nvmet-rdma:fix possible bogus dereference under heavy load")

Cc: <stable@xxxxxxxxxxxxxxx>
Reviewed-by: Max Gurtovoy <maxg@xxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Raju Rangoju <rajur@xxxxxxxxxxx>
Signed-off-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>

diff --git a/drivers/nvme/target/rdma.c b/drivers/nvme/target/rdma.c
index a8d23eb80192..a884e3a0e8af 100644
--- a/drivers/nvme/target/rdma.c
+++ b/drivers/nvme/target/rdma.c
@@ -139,6 +139,10 @@ static void nvmet_rdma_recv_done(struct ib_cq *cq, struct ib_wc *wc);
 static void nvmet_rdma_read_data_done(struct ib_cq *cq, struct ib_wc *wc);
 static void nvmet_rdma_qp_event(struct ib_event *event, void *priv);
 static void nvmet_rdma_queue_disconnect(struct nvmet_rdma_queue *queue);
+static void nvmet_rdma_free_rsp(struct nvmet_rdma_device *ndev,
+				struct nvmet_rdma_rsp *r);
+static int nvmet_rdma_alloc_rsp(struct nvmet_rdma_device *ndev,
+				struct nvmet_rdma_rsp *r);
 
 static const struct nvmet_fabrics_ops nvmet_rdma_ops;
 
@@ -182,9 +186,17 @@ nvmet_rdma_get_rsp(struct nvmet_rdma_queue *queue)
 	spin_unlock_irqrestore(&queue->rsps_lock, flags);
 
 	if (unlikely(!rsp)) {
-		rsp = kmalloc(sizeof(*rsp), GFP_KERNEL);
+		int ret;
+
+		rsp = kzalloc(sizeof(*rsp), GFP_KERNEL);
 		if (unlikely(!rsp))
 			return NULL;
+		ret = nvmet_rdma_alloc_rsp(queue->dev, rsp);
+		if (unlikely(ret)) {
+			kfree(rsp);
+			return NULL;
+		}
+
 		rsp->allocated = true;
 	}
 
@@ -197,6 +209,7 @@ nvmet_rdma_put_rsp(struct nvmet_rdma_rsp *rsp)
 	unsigned long flags;
 
 	if (unlikely(rsp->allocated)) {
+		nvmet_rdma_free_rsp(rsp->queue->dev, rsp);
 		kfree(rsp);
 		return;
 	}