bpf: Free special fields when update [lru_,]percpu_hash maps

In the Linux kernel, the following vulnerability has been resolved: bpf: Free special fields when update [lru_,]percpu_hash maps As [lru_,]percpu_hash maps support BPF_KPTR_{REF,PERCPU}, missing calls to 'bpf_obj_free_fields()' in 'pcpu_copy_value()' could cause the memory referenced by BPF_KPTR_{REF,PERCPU} fields to be held until the map gets freed. Fix this by calling 'bpf_obj_free_fields()' after 'copy_map_value[,_long]()' in 'pcpu_copy_value()'.