libbpf: Fix removal of inner map in bpf_object__create_map

[ Upstream commit a21ab4c ]

If creating an outer map of a BTF-defined map-in-map fails (via
bpf_object__create_map()), then the previously created its inner map
won't be destroyed.

Fix this by ensuring that the destroy routines are not bypassed in the
case of a failure.

Fixes: 646f02f ("libbpf: Add BTF-defined map-in-map support")
Reported-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Martynas Pumputis <m@lambda.lt>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210719173838.423148-2-m@lambda.lt
Signed-off-by: Sasha Levin <sashal@kernel.org>

tools/lib/bpf/libbpf.c

@@ -4123,6 +4123,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map)
 {
 	struct bpf_create_map_attr create_attr;
 	struct bpf_map_def *def = &map->def;
+	int err = 0;
 
 	memset(&create_attr, 0, sizeof(create_attr));
 
@@ -4165,8 +4166,6 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map)
 
 	if (bpf_map_type__is_map_in_map(def->type)) {
 		if (map->inner_map) {
-			int err;
-
 			err = bpf_object__create_map(obj, map->inner_map);
 			if (err) {
 				pr_warn("map '%s': failed to create inner map: %d\n",
@@ -4183,8 +4182,8 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map)
 	if (map->fd < 0 && (create_attr.btf_key_type_id ||
 			    create_attr.btf_value_type_id)) {
 		char *cp, errmsg[STRERR_BUFSIZE];
-		int err = -errno;
 
+		err = -errno;
 		cp = libbpf_strerror_r(err, errmsg, sizeof(errmsg));
 		pr_warn("Error in bpf_create_map_xattr(%s):%s(%d). Retrying without BTF.\n",
 			map->name, cp, err);
@@ -4196,15 +4195,14 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map)
 		map->fd = bpf_create_map_xattr(&create_attr);
 	}
 
-	if (map->fd < 0)
-		return -errno;
+	err = map->fd < 0 ? -errno : 0;
 
 	if (bpf_map_type__is_map_in_map(def->type) && map->inner_map) {
 		bpf_map__destroy(map->inner_map);
 		zfree(&map->inner_map);
 	}
 
-	return 0;
+	return err;
 }
 
 static int init_map_slots(struct bpf_map *map)