openvswitch: Stricter validation for the userspace action

openvswitch: Stricter validation for the userspace action

This change enhances the robustness of validate_userspace() by ensuring
that all Netlink attributes are fully contained within the parent
attribute. The previous use of nla_parse_nested_deprecated() could
silently skip trailing or malformed attributes, as it stops parsing at
the first invalid entry.

By switching to nla_parse_deprecated_strict(), we make sure only fully
validated attributes are copied for later use.

Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Acked-by: Ilya Maximets <i.maximets@ovn.org>
Link: https://patch.msgid.link/67eb414e2d250e8408bb8afeb982deca2ff2b10b.1747037304.git.echaudro@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>