net/mlx5: Check if lag is supported before creating one

This patch fixes a memleak issue by preventing to create a lag and
add PFs if lag is not supported.

comm “python3”, pid 349349, jiffies 4296985507 (age 1446.976s)
hex dump (first 32 bytes):
  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  …………….
  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  …………….
 backtrace:
  [<000000005b216ae7>] mlx5_lag_add+0x1d5/0×3f0 [mlx5_core]
  [<000000000445aa55>] mlx5e_nic_enable+0x66/0×1b0 [mlx5_core]
  [<00000000c56734c3>] mlx5e_attach_netdev+0x16e/0×200 [mlx5_core]
  [<0000000030439d1f>] mlx5e_attach+0x5c/0×90 [mlx5_core]
  [<0000000018fd8615>] mlx5e_add+0x1a4/0×410 [mlx5_core]
  [<0000000068bc504b>] mlx5_add_device+0x72/0×120 [mlx5_core]
  [<000000009fce51f9>] mlx5_register_device+0x77/0xb0 [mlx5_core]
  [<00000000d0d81ff3>] mlx5_load_one+0xc58/0×1eb0 [mlx5_core]
  [<0000000045077adc>] init_one+0x3ea/0×920 [mlx5_core]
  [<0000000043287674>] pci_device_probe+0xcd/0×150
  [<00000000dafd3279>] really_probe+0x1c9/0×4b0
  [<00000000f06bdd84>] driver_probe_device+0x5d/0×140
  [<00000000e3d508b6>] device_driver_attach+0x4f/0×60
  [<0000000084fba0f0>] bind_store+0xbf/0×120
  [<00000000bf6622b3>] kernfs_fop_write+0x114/0×1b0

Fixes: 9b412cc3 ("net/mlx5e: Add LAG warning if bond slave is not lag master")
Signed-off-by: Mark Zhang <markzhang@nvidia.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Reviewed-by: Maor Gottlieb <maorg@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>

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

@@ -564,7 +564,9 @@ void mlx5_lag_add(struct mlx5_core_dev *dev, struct net_device *netdev)
 	struct mlx5_core_dev *tmp_dev;
 	int i, err;
 
-	if (!MLX5_CAP_GEN(dev, vport_group_manager))
+	if (!MLX5_CAP_GEN(dev, vport_group_manager) ||
+	    !MLX5_CAP_GEN(dev, lag_master) ||
+	    MLX5_CAP_GEN(dev, num_lag_ports) != MLX5_MAX_PORTS)
 		return;
 
 	tmp_dev = mlx5_get_next_phys_dev(dev);
@@ -582,12 +584,9 @@ void mlx5_lag_add(struct mlx5_core_dev *dev, struct net_device *netdev)
 	if (mlx5_lag_dev_add_pf(ldev, dev, netdev) < 0)
 		return;
 
-	for (i = 0; i < MLX5_MAX_PORTS; i++) {
-		tmp_dev = ldev->pf[i].dev;
-		if (!tmp_dev || !MLX5_CAP_GEN(tmp_dev, lag_master) ||
-		    MLX5_CAP_GEN(tmp_dev, num_lag_ports) != MLX5_MAX_PORTS)
+	for (i = 0; i < MLX5_MAX_PORTS; i++)
+		if (!ldev->pf[i].dev)
 			break;
-	}
 
 	if (i >= MLX5_MAX_PORTS)
 		ldev->flags |= MLX5_LAG_FLAG_READY;