libbpf: Fix removal of inner map in bpf_object__create_map

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: 646f02ffdd49c ("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

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 17bc922f543fd0572886668cd1c64b8d0690994b..4c153c379989b9250a3b3b0db417cef7487cfc1c 100644 (file)
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -4527,6 +4527,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 {
        struct bpf_create_map_attr create_attr;
        struct bpf_map_def *def = &map->def;
+       int err = 0;
 
        memset(&create_attr, 0, sizeof(create_attr));
 
@@ -4569,8 +4570,6 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
 
        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, true);
                        if (err) {
                                pr_warn("map '%s': failed to create inner map: %d\n",
@@ -4595,8 +4594,8 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
        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);
@@ -4608,8 +4607,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
                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) {
                if (obj->gen_loader)
@@ -4618,7 +4616,7 @@ static int bpf_object__create_map(struct bpf_object *obj, struct bpf_map *map, b
                zfree(&map->inner_map);
        }
 
-       return 0;
+       return err;
 }
 
 static int init_map_slots(struct bpf_object *obj, struct bpf_map *map)