net: marvell: prestera: fix incorrect return of port_find

stable inclusion
from stable-v5.10.89
commit 78e49d77e517c205e7c2c2f7a970468dd2f867b1
bugzilla: 186140 https://gitee.com/openeuler/kernel/issues/I4S8HA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=78e49d77e517c205e7c2c2f7a970468dd2f867b1

--------------------------------

[ Upstream commit 8b681bd7 ]

In case, when some ports is in list and we don't find requested - we
return last iterator state and not return NULL as expected.

Fixes: 501ef306 ("net: marvell: prestera: Add driver for Prestera family ASIC devices")
Signed-off-by: NYevhen Orlov <yevhen.orlov@plvision.eu>
Link: https://lore.kernel.org/r/20211216170736.8851-1-yevhen.orlov@plvision.euSigned-off-by: NJakub Kicinski <kuba@kernel.org>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/net/ethernet/marvell/prestera/prestera_main.c

@@ -50,12 +50,14 @@ int prestera_port_pvid_set(struct prestera_port *port, u16 vid)
 struct prestera_port *prestera_port_find_by_hwid(struct prestera_switch *sw,
 						 u32 dev_id, u32 hw_id)
 {
-	struct prestera_port *port = NULL;
+	struct prestera_port *port = NULL, *tmp;
 
 	read_lock(&sw->port_list_lock);
-	list_for_each_entry(port, &sw->port_list, list) {
-		if (port->dev_id == dev_id && port->hw_id == hw_id)
+	list_for_each_entry(tmp, &sw->port_list, list) {
+		if (tmp->dev_id == dev_id && tmp->hw_id == hw_id) {
+			port = tmp;
 			break;
+		}
 	}
 	read_unlock(&sw->port_list_lock);
 
@@ -64,12 +66,14 @@ struct prestera_port *prestera_port_find_by_hwid(struct prestera_switch *sw,
 
 struct prestera_port *prestera_find_port(struct prestera_switch *sw, u32 id)
 {
-	struct prestera_port *port = NULL;
+	struct prestera_port *port = NULL, *tmp;
 
 	read_lock(&sw->port_list_lock);
-	list_for_each_entry(port, &sw->port_list, list) {
-		if (port->id == id)
+	list_for_each_entry(tmp, &sw->port_list, list) {
+		if (tmp->id == id) {
+			port = tmp;
 			break;
+		}
 	}
 	read_unlock(&sw->port_list_lock);