[PATCH net] net/mlx5e: Fix AF_XDP TX timestamp teardown NULL dereference

[prathameshdeshpande7@gmail.com]

From: Prathamesh Deshpande <prathameshdeshpande7@gmail.com>

During XSK TX queue teardown, outstanding descriptors are completed
without a CQE. If one requested a TX timestamp, the completion path
passes that NULL CQE to mlx5e_xsk_fill_timestamp(), which dereferences
it.

Return zero when no CQE is available, indicating that teardown did not
produce a TX timestamp.

Fixes: ec706a860eba ("net/mlx5e: Implement AF_XDP TX timestamp and checksum offload")

Signed-off-by: Prathamesh Deshpande <prathameshdeshpande7@gmail.com>
---
 drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
index 77ea51bfbaae..2cca20e1b9b7 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en/xdp.c
@@ -293,6 +293,9 @@ static u64 mlx5e_xsk_fill_timestamp(void *_priv)
 	struct mlx5e_xsk_tx_complete *priv = _priv;
 	u64 ts;
 
+	if (!priv->cqe)
+		return 0;
+
 	ts = get_cqe_ts(priv->cqe);
 
 	if (mlx5_is_real_time_rq(priv->cq->mdev) || mlx5_is_real_time_sq(priv->cq->mdev))
-- 
2.43.0