net: core: devlink: use right genl user_ptr when handling port param get/set

Fix incorrect user_ptr dereferencing when handling port param get/set:

    idx [0] stores the 'struct devlink' pointer;
    idx [1] stores the 'struct devlink_port' pointer;

Fixes: 637989b5 ("devlink: Always use user_ptr[0] for devlink and simplify post_doit")
CC: Parav Pandit <parav@mellanox.com>
Signed-off-by: Oleksandr Mazur <oleksandr.mazur@plvision.eu>
Signed-off-by: Vadym Kochan <vadym.kochan@plvision.eu>
Link: https://lore.kernel.org/r/20210119085333.16833-1-vadym.kochan@plvision.euSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/core/devlink.c

@@ -4146,7 +4146,7 @@ static int devlink_nl_cmd_port_param_get_dumpit(struct sk_buff *msg,
 static int devlink_nl_cmd_port_param_get_doit(struct sk_buff *skb,
 					      struct genl_info *info)
 {
-	struct devlink_port *devlink_port = info->user_ptr[0];
+	struct devlink_port *devlink_port = info->user_ptr[1];
 	struct devlink_param_item *param_item;
 	struct sk_buff *msg;
 	int err;
@@ -4175,7 +4175,7 @@ static int devlink_nl_cmd_port_param_get_doit(struct sk_buff *skb,
 static int devlink_nl_cmd_port_param_set_doit(struct sk_buff *skb,
 					      struct genl_info *info)
 {
-	struct devlink_port *devlink_port = info->user_ptr[0];
+	struct devlink_port *devlink_port = info->user_ptr[1];
 
 	return __devlink_nl_cmd_param_set_doit(devlink_port->devlink,
 					       devlink_port->index,