Re: [PATCH bpf-next v1 04/13] bpf: lsm: Allow btf_id based attachment for LSM hooks

[Andrii Nakryiko]

On Fri, Dec 20, 2019 at 7:42 AM KP Singh <kpsingh@xxxxxxxxxxxx> wrote:
>
> From: KP Singh <kpsingh@xxxxxxxxxx>
>
> Refactor and re-use most of the logic for BPF_PROG_TYPE_TRACING with a few
> changes.
>
> - The LSM hook BTF types are prefixed with "lsm_btf_"

btf_trace_ and btf_struct_ops all have btf_ first, let's keep this consistent.

> - These types do not need the first (void *) pointer argument. The verifier
>   only looks for this argument if prod->aux->attach_btf_trace is set.
>
> Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
> ---
>  kernel/bpf/syscall.c  |  1 +
>  kernel/bpf/verifier.c | 83 ++++++++++++++++++++++++++++++++++++++++---
>  2 files changed, 80 insertions(+), 4 deletions(-)
>

[...]

> +
> +       t = btf_type_by_id(btf_vmlinux, btf_id);
> +       if (!t) {
> +               verbose(env, "attach_btf_id %u is invalid\n", btf_id);
> +               return -EINVAL;
> +       }
> +
> +       tname = btf_name_by_offset(btf_vmlinux, t->name_off);
> +       if (!tname) {

it can be empty, so better: !tname || !tname[0]

> +               verbose(env, "attach_btf_id %u doesn't have a name\n", btf_id);
> +               return -EINVAL;
> +       }
> +

[...]