On Tue, Oct 10, 2023 at 1:35 AM Jiri Olsa <olsajiri@xxxxxxxxx> wrote:
>
> On Wed, Sep 27, 2023 at 03:58:00PM -0700, Andrii Nakryiko wrote:
>
> SNIP
>
> > -#define BPF_MAP_CREATE_LAST_FIELD map_extra
> > +#define BPF_MAP_CREATE_LAST_FIELD map_token_fd
> > /* called via syscall */
> > static int map_create(union bpf_attr *attr)
> > {
> > const struct bpf_map_ops *ops;
> > + struct bpf_token *token = NULL;
> > int numa_node = bpf_map_attr_numa_node(attr);
> > u32 map_type = attr->map_type;
> > struct bpf_map *map;
> > @@ -1157,14 +1158,32 @@ static int map_create(union bpf_attr *attr)
> > if (!ops->map_mem_usage)
> > return -EINVAL;
> >
> > + if (attr->map_token_fd) {
> > + token = bpf_token_get_from_fd(attr->map_token_fd);
> > + if (IS_ERR(token))
> > + return PTR_ERR(token);
> > +
> > + /* if current token doesn't grant map creation permissions,
> > + * then we can't use this token, so ignore it and rely on
> > + * system-wide capabilities checks
> > + */
> > + if (!bpf_token_allow_cmd(token, BPF_MAP_CREATE) ||
> > + !bpf_token_allow_map_type(token, attr->map_type)) {
> > + bpf_token_put(token);
> > + token = NULL;
> > + }
> > + }
> > +
> > + err = -EPERM;
> > +
> > /* Intent here is for unprivileged_bpf_disabled to block BPF map
> > * creation for unprivileged users; other actions depend
> > * on fd availability and access to bpffs, so are dependent on
> > * object creation success. Even with unprivileged BPF disabled,
> > * capability checks are still carried out.
> > */
> > - if (sysctl_unprivileged_bpf_disabled && !bpf_capable())
> > - return -EPERM;
> > + if (sysctl_unprivileged_bpf_disabled && !bpf_token_capable(token, CAP_BPF))
> > + goto put_token;
> >
> > /* check privileged map type permissions */
> > switch (map_type) {
> > @@ -1197,25 +1216,27 @@ static int map_create(union bpf_attr *attr)
> > case BPF_MAP_TYPE_LRU_PERCPU_HASH:
> > case BPF_MAP_TYPE_STRUCT_OPS:
> > case BPF_MAP_TYPE_CPUMAP:
> > - if (!bpf_capable())
> > - return -EPERM;
> > + if (!bpf_token_capable(token, CAP_BPF))
> > + goto put_token;
> > break;
> > case BPF_MAP_TYPE_SOCKMAP:
> > case BPF_MAP_TYPE_SOCKHASH:
> > case BPF_MAP_TYPE_DEVMAP:
> > case BPF_MAP_TYPE_DEVMAP_HASH:
> > case BPF_MAP_TYPE_XSKMAP:
> > - if (!bpf_net_capable())
> > - return -EPERM;
> > + if (!bpf_token_capable(token, CAP_NET_ADMIN))
> > + goto put_token;
> > break;
> > default:
> > WARN(1, "unsupported map type %d", map_type);
> > - return -EPERM;
> > + goto put_token;
> > }
> >
> > map = ops->map_alloc(attr);
> > - if (IS_ERR(map))
> > - return PTR_ERR(map);
> > + if (IS_ERR(map)) {
> > + err = PTR_ERR(map);
> > + goto put_token;
> > + }
> > map->ops = ops;
> > map->map_type = map_type;
> >
> > @@ -1252,7 +1273,7 @@ static int map_create(union bpf_attr *attr)
> > map->btf = btf;
> >
> > if (attr->btf_value_type_id) {
> > - err = map_check_btf(map, btf, attr->btf_key_type_id,
> > + err = map_check_btf(map, token, btf, attr->btf_key_type_id,
> > attr->btf_value_type_id);
> > if (err)
> > goto free_map;
>
> I might be missing something, but should we call bpf_token_put(token)
> on non-error path as well? probably after bpf_map_save_memcg call
Not missing anything. I used to keep token reference inside struct
bpf_map on success, but I ripped that out, so yes, token has to be put
properly even on success. Thanks for catching this!
And yes, right after bpf_map_save_memcg() seems like the best spot.
>
> jirka
>
> > @@ -1293,6 +1314,8 @@ static int map_create(union bpf_attr *attr)
> > free_map:
> > btf_put(map->btf);
> > map->ops->map_free(map);
> > +put_token:
> > + bpf_token_put(token);
> > return err;
> > }
> >
>
> SNIP
