[PATCH 5.9 413/757] RDMA/mlx5: Fix potential race between destroy and CQE poll

[Greg Kroah-Hartman]

From: Leon Romanovsky <leonro@xxxxxxxxxxxx>

[ Upstream commit 4b916ed9f9e85f705213ca8d69771d3c1cd6ee5a ]

The SRQ can be destroyed right before mlx5_cmd_get_srq is called.
In such case the latter will return NULL instead of expected SRQ.

Fixes: e126ba97dba9 ("mlx5: Add driver for Mellanox Connect-IB adapters")
Link: https://lore.kernel.org/r/20200830084010.102381-5-leon@xxxxxxxxxx
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/infiniband/hw/mlx5/cq.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/mlx5/cq.c b/drivers/infiniband/hw/mlx5/cq.c
index dceb0eb2bed16..b318bde2e565f 100644
--- a/drivers/infiniband/hw/mlx5/cq.c
+++ b/drivers/infiniband/hw/mlx5/cq.c
@@ -168,7 +168,7 @@ static void handle_responder(struct ib_wc *wc, struct mlx5_cqe64 *cqe,
 {
 	enum rdma_link_layer ll = rdma_port_get_link_layer(qp->ibqp.device, 1);
 	struct mlx5_ib_dev *dev = to_mdev(qp->ibqp.device);
-	struct mlx5_ib_srq *srq;
+	struct mlx5_ib_srq *srq = NULL;
 	struct mlx5_ib_wq *wq;
 	u16 wqe_ctr;
 	u8  roce_packet_type;
@@ -180,7 +180,8 @@ static void handle_responder(struct ib_wc *wc, struct mlx5_cqe64 *cqe,
 
 		if (qp->ibqp.xrcd) {
 			msrq = mlx5_cmd_get_srq(dev, be32_to_cpu(cqe->srqn));
-			srq = to_mibsrq(msrq);
+			if (msrq)
+				srq = to_mibsrq(msrq);
 		} else {
 			srq = to_msrq(qp->ibqp.srq);
 		}
-- 
2.25.1