bpf: fix wrong exposure of map_flags into fdinfo for lpm

trie_alloc() always needs to have BPF_F_NO_PREALLOC passed in via
attr->map_flags, since it does not support preallocation yet. We
check the flag, but we never copy the flag into trie->map.map_flags,
which is later on exposed into fdinfo and used by loaders such as
iproute2. Latter uses this in bpf_map_selfcheck_pinned() to test
whether a pinned map has the same spec as the one from the BPF obj
file and if not, bails out, which is currently the case for lpm
since it exposes always 0 as flags.

Also copy over flags in array_map_alloc() and stack_map_alloc().
They always have to be 0 right now, but we should make sure to not
miss to copy them over at a later point in time when we add actual
flags for them to use.

Fixes: b95a5c4db09b ("bpf: add a longest prefix match trie map implementation")
Reported-by: Jarno Rajahalme <jarno@covalent.io>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/bpf/arraymap.c

@@ -86,6 +86,7 @@ static struct bpf_map *array_map_alloc(union bpf_attr *attr)
 	array->map.key_size = attr->key_size;
 	array->map.value_size = attr->value_size;
 	array->map.max_entries = attr->max_entries;
+	array->map.map_flags = attr->map_flags;
 	array->elem_size = elem_size;
 
 	if (!percpu)

kernel/bpf/lpm_trie.c

@@ -432,6 +432,7 @@ static struct bpf_map *trie_alloc(union bpf_attr *attr)
 	trie->map.key_size = attr->key_size;
 	trie->map.value_size = attr->value_size;
 	trie->map.max_entries = attr->max_entries;
+	trie->map.map_flags = attr->map_flags;
 	trie->data_size = attr->key_size -
 			  offsetof(struct bpf_lpm_trie_key, data);
 	trie->max_prefixlen = trie->data_size * 8;

kernel/bpf/stackmap.c

@@ -88,6 +88,7 @@ static struct bpf_map *stack_map_alloc(union bpf_attr *attr)
 	smap->map.key_size = attr->key_size;
 	smap->map.value_size = value_size;
 	smap->map.max_entries = attr->max_entries;
+	smap->map.map_flags = attr->map_flags;
 	smap->n_buckets = n_buckets;
 	smap->map.pages = round_up(cost, PAGE_SIZE) >> PAGE_SHIFT;