[PATCH 5.9 142/255] net/mlx5e: Fix incorrect access of RCU-protected xdp_prog

[Greg Kroah-Hartman]

From: Maxim Mikityanskiy <maximmi@xxxxxxxxxxxx>

[ Upstream commit 1a50cf9a67ff2241c2949d30bc11c8dd4280eef8 ]

rq->xdp_prog is RCU-protected and should be accessed only with
rcu_access_pointer for the NULL check in mlx5e_poll_rx_cq.

rq->xdp_prog may change on the fly only from one non-NULL value to
another non-NULL value, so the checks in mlx5e_xdp_handle and
mlx5e_poll_rx_cq will have the same result during one NAPI cycle,
meaning that no additional synchronization is needed.

Fixes: fe45386a2082 ("net/mlx5e: Use RCU to protect rq->xdp_prog")
Signed-off-by: Maxim Mikityanskiy <maximmi@xxxxxxxxxxxx>
Reviewed-by: Tariq Toukan <tariqt@xxxxxxxxxx>
Signed-off-by: Saeed Mahameed <saeedm@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/ethernet/mellanox/mlx5/core/en_rx.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
index 64c8ac5eabf6a..a0a4398408b85 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_rx.c
@@ -1566,7 +1566,7 @@ int mlx5e_poll_rx_cq(struct mlx5e_cq *cq, int budget)
 	} while ((++work_done < budget) && (cqe = mlx5_cqwq_get_cqe(cqwq)));
 
 out:
-	if (rq->xdp_prog)
+	if (rcu_access_pointer(rq->xdp_prog))
 		mlx5e_xdp_rx_poll_complete(rq);
 
 	mlx5_cqwq_update_db_record(cqwq);
-- 
2.27.0