net/mlx5: Avoid panic when setting vport mac, getting vport config

If we try to set VFs mac address on a VF (not PF) net device,
the kernel will be crash. The commands are show as below:

$ echo 2 > /sys/class/net/$MLX_PF0/device/sriov_numvfs
$ ip link set $MLX_VF0 vf 0 mac 00:11:22:33:44:00

[exception RIP: mlx5_eswitch_set_vport_mac+41]
[ffffb8b7079e3688] do_setlink at ffffffff8f67f85b
[ffffb8b7079e37a8] __rtnl_newlink at ffffffff8f683778
[ffffb8b7079e3b68] rtnl_newlink at ffffffff8f683a63
[ffffb8b7079e3b90] rtnetlink_rcv_msg at ffffffff8f67d812
[ffffb8b7079e3c10] netlink_rcv_skb at ffffffff8f6b88ab
[ffffb8b7079e3c60] netlink_unicast at ffffffff8f6b808f
[ffffb8b7079e3ca0] netlink_sendmsg at ffffffff8f6b8412
[ffffb8b7079e3d18] sock_sendmsg at ffffffff8f6452f6
[ffffb8b7079e3d30] ___sys_sendmsg at ffffffff8f645860
[ffffb8b7079e3eb0] __sys_sendmsg at ffffffff8f647a38
[ffffb8b7079e3f38] do_syscall_64 at ffffffff8f00401b
[ffffb8b7079e3f50] entry_SYSCALL_64_after_hwframe at ffffffff8f80008c

and

[exception RIP: mlx5_eswitch_get_vport_config+12]
[ffffa70607e57678] mlx5e_get_vf_config at ffffffffc03c7f8f [mlx5_core]
[ffffa70607e57688] do_setlink at ffffffffbc67fa59
[ffffa70607e577a8] __rtnl_newlink at ffffffffbc683778
[ffffa70607e57b68] rtnl_newlink at ffffffffbc683a63
[ffffa70607e57b90] rtnetlink_rcv_msg at ffffffffbc67d812
[ffffa70607e57c10] netlink_rcv_skb at ffffffffbc6b88ab
[ffffa70607e57c60] netlink_unicast at ffffffffbc6b808f
[ffffa70607e57ca0] netlink_sendmsg at ffffffffbc6b8412
[ffffa70607e57d18] sock_sendmsg at ffffffffbc6452f6
[ffffa70607e57d30] ___sys_sendmsg at ffffffffbc645860
[ffffa70607e57eb0] __sys_sendmsg at ffffffffbc647a38
[ffffa70607e57f38] do_syscall_64 at ffffffffbc00401b
[ffffa70607e57f50] entry_SYSCALL_64_after_hwframe at ffffffffbc80008c

Fixes: a8d70a05 ("net/mlx5: E-Switch, Disallow vlan/spoofcheck setup if not being esw manager")
Cc: Eli Cohen <eli@mellanox.com>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Acked-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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

@@ -1931,7 +1931,7 @@ int mlx5_eswitch_set_vport_mac(struct mlx5_eswitch *esw,
 	u64 node_guid;
 	int err = 0;
 
-	if (!MLX5_CAP_GEN(esw->dev, vport_group_manager))
+	if (!esw || !MLX5_CAP_GEN(esw->dev, vport_group_manager))
 		return -EPERM;
 	if (!LEGAL_VPORT(esw, vport) || is_multicast_ether_addr(mac))
 		return -EINVAL;
@@ -2005,7 +2005,7 @@ int mlx5_eswitch_get_vport_config(struct mlx5_eswitch *esw,
 {
 	struct mlx5_vport *evport;
 
-	if (!MLX5_CAP_GEN(esw->dev, vport_group_manager))
+	if (!esw || !MLX5_CAP_GEN(esw->dev, vport_group_manager))
 		return -EPERM;
 	if (!LEGAL_VPORT(esw, vport))
 		return -EINVAL;