net/mlx5e: Avoid referencing skb after free-ing in drop path of mlx5e_sq_xmit_wqe

When SQ is a port timestamping SQ for PTP, do not access tx flags of skb
after free-ing the skb. Free the skb only after all references that depend
on it have been handled in the dropped WQE path.

Fixes: 3178308a ("net/mlx5e: Make tx_port_ts logic resilient to out-of-order CQEs")
Signed-off-by: Rahul Rameshbabu <rrameshbabu@nvidia.com>
Reviewed-by: Tariq Toukan <tariqt@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Link: https://lore.kernel.org/r/20231114215846.5902-10-saeed@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlx5/core/en_tx.c

@@ -494,10 +494,10 @@ mlx5e_sq_xmit_wqe(struct mlx5e_txqsq *sq, struct sk_buff *skb,
 
 err_drop:
 	stats->dropped++;
-	dev_kfree_skb_any(skb);
 	if (unlikely(sq->ptpsq && (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP)))
 		mlx5e_ptp_metadata_fifo_push(&sq->ptpsq->metadata_freelist,
 					     be32_to_cpu(eseg->flow_table_metadata));
+	dev_kfree_skb_any(skb);
 	mlx5e_tx_flush(sq);
 }