net: dsa: felix: Add NULL check for outer_tagging_rule()

In felix_update_tag_8021q_rx_rules(), the return value of
ocelot_vcap_block_find_filter_by_id() is not checked, which could
lead to a NULL pointer dereference if the filter is not found.

Add the necessary check and use `continue` to skip the current CPU
port if the filter is not found, ensuring that all CPU ports are
processed.

Fixes: f1288fd ("net: dsa: felix: fix VLAN tag loss on CPU reception with ocelot-8021q")
Cc: [email protected] # 6.11+
Signed-off-by: Wentao Liang <[email protected]>
Reviewed-by: Michal Swiatkowski <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Signed-off-by: NipaLocal <nipa@local>

Author: ISCAS-Vulab

drivers/net/dsa/ocelot/felix.c

@@ -348,6 +348,8 @@ static int felix_update_tag_8021q_rx_rules(struct dsa_switch *ds, int port,
 
 		outer_tagging_rule = ocelot_vcap_block_find_filter_by_id(block_vcap_es0,
 									 cookie, false);
+		if (!outer_tagging_rule)
+			continue;
 
 		felix_update_tag_8021q_rx_rule(outer_tagging_rule, vlan_filtering);