In the vlan_changelink function, a loop is used to parse the nested
attributes IFLA_VLAN_EGRESS_QOS and IFLA_VLAN_INGRESS_QOS in order to
obtain the struct ifla_vlan_qos_mapping. These two nested attributes are
checked in the vlan_validate_qos_map function, which calls
nla_validate_nested_deprecated with the vlan_map_policy.

However, this deprecated validator applies a LIBERAL strictness, allowing
the presence of an attribute with the type IFLA_VLAN_QOS_UNSPEC.
Consequently, the loop in vlan_changelink may parse an attribute of type
IFLA_VLAN_QOS_UNSPEC and believe it carries a payload of
struct ifla_vlan_qos_mapping, which is not necessarily true.

To address this issue and ensure compatibility, this patch introduces two
type checks that skip attributes whose type is not IFLA_VLAN_QOS_MAPPING.

Fixes: 07b5b17e ("[VLAN]: Use rtnl_link API")
Signed-off-by: Lin Ma <linma@zju.edu.cn>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240118130306.1644001-1-linma@zju.edu.cnSigned-off-by: Jakub Kicinski <kuba@kernel.org>