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()'.

Fixes: 65334e6 ("bpf: Support kptrs in percpu hashmap and percpu LRU hashmap")
Signed-off-by: Leon Hwang <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: Asphaltt

kernel/bpf/hashtab.c

@@ -937,12 +937,14 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
 	if (!onallcpus) {
 		/* copy true value_size bytes */
 		copy_map_value(&htab->map, this_cpu_ptr(pptr), value);
+		bpf_obj_free_fields(htab->map.record, this_cpu_ptr(pptr));
 	} else {
 		u32 size = round_up(htab->map.value_size, 8);
 		int off = 0, cpu;
 
 		for_each_possible_cpu(cpu) {
 			copy_map_value_long(&htab->map, per_cpu_ptr(pptr, cpu), value + off);
+			bpf_obj_free_fields(htab->map.record, per_cpu_ptr(pptr, cpu));
 			off += size;
 		}
 	}