mlxsw: spectrum: Guard against invalid local ports

When processing events generated by the device's firmware, the driver
protects itself from events reported for non-existent local ports, but
not for the CPU port (local port 0), which exists, but does not have all
the fields as any local port.

This can result in a NULL pointer dereference when trying access
'struct mlxsw_sp_port' fields which are not initialized for CPU port.

Commit 63b08b1f ("mlxsw: spectrum: Protect driver from buggy firmware")
already handled such issue by bailing early when processing a PUDE event
reported for the CPU port.

Generalize the approach by moving the check to a common function and
making use of it in all relevant places.
Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/mellanox/mlxsw/spectrum.c

@@ -2148,13 +2148,11 @@ static void mlxsw_sp_pude_event_func(const struct mlxsw_reg_info *reg,
 	struct mlxsw_sp *mlxsw_sp = priv;
 	struct mlxsw_sp_port *mlxsw_sp_port;
 	enum mlxsw_reg_pude_oper_status status;
-	unsigned int max_ports;
 	u16 local_port;
 
-	max_ports = mlxsw_core_max_ports(mlxsw_sp->core);
 	local_port = mlxsw_reg_pude_local_port_get(pude_pl);
 
-	if (WARN_ON_ONCE(!local_port || local_port >= max_ports))
+	if (WARN_ON_ONCE(!mlxsw_sp_local_port_is_valid(mlxsw_sp, local_port)))
 		return;
 	mlxsw_sp_port = mlxsw_sp->ports[local_port];
 	if (!mlxsw_sp_port)

drivers/net/ethernet/mellanox/mlxsw/spectrum.h

@@ -481,6 +481,13 @@ int
 mlxsw_sp_port_vlan_classification_set(struct mlxsw_sp_port *mlxsw_sp_port,
 				      bool is_8021ad_tagged,
 				      bool is_8021q_tagged);
+static inline bool
+mlxsw_sp_local_port_is_valid(struct mlxsw_sp *mlxsw_sp, u16 local_port)
+{
+	unsigned int max_ports = mlxsw_core_max_ports(mlxsw_sp->core);
+
+	return local_port < max_ports && local_port;
+}
 
 /* spectrum_buffers.c */
 struct mlxsw_sp_hdroom_prio {

drivers/net/ethernet/mellanox/mlxsw/spectrum_ptp.c

@@ -568,12 +568,11 @@ void mlxsw_sp1_ptp_got_timestamp(struct mlxsw_sp *mlxsw_sp, bool ingress,
 				 u8 domain_number, u16 sequence_id,
 				 u64 timestamp)
 {
-	unsigned int max_ports = mlxsw_core_max_ports(mlxsw_sp->core);
 	struct mlxsw_sp_port *mlxsw_sp_port;
 	struct mlxsw_sp1_ptp_key key;
 	u8 types;
 
-	if (WARN_ON_ONCE(local_port >= max_ports))
+	if (WARN_ON_ONCE(!mlxsw_sp_local_port_is_valid(mlxsw_sp, local_port)))
 		return;
 	mlxsw_sp_port = mlxsw_sp->ports[local_port];
 	if (!mlxsw_sp_port)

drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c

@@ -2616,7 +2616,6 @@ static void mlxsw_sp_fdb_notify_mac_process(struct mlxsw_sp *mlxsw_sp,
 					    char *sfn_pl, int rec_index,
 					    bool adding)
 {
-	unsigned int max_ports = mlxsw_core_max_ports(mlxsw_sp->core);
 	struct mlxsw_sp_port_vlan *mlxsw_sp_port_vlan;
 	struct mlxsw_sp_bridge_device *bridge_device;
 	struct mlxsw_sp_bridge_port *bridge_port;
@@ -2630,7 +2629,7 @@ static void mlxsw_sp_fdb_notify_mac_process(struct mlxsw_sp *mlxsw_sp,
 
 	mlxsw_reg_sfn_mac_unpack(sfn_pl, rec_index, mac, &fid, &local_port);
 
-	if (WARN_ON_ONCE(local_port >= max_ports))
+	if (WARN_ON_ONCE(!mlxsw_sp_local_port_is_valid(mlxsw_sp, local_port)))
 		return;
 	mlxsw_sp_port = mlxsw_sp->ports[local_port];
 	if (!mlxsw_sp_port) {