On Thu, Mar 25, 2021 at 04:40:33PM +0100, Toke Høiland-Jørgensen wrote:
> With the introduction of the struct_ops program type, it became possible to
> implement kernel functionality in BPF, making it viable to use BPF in place
> of a regular kernel module for these particular operations.
>
> Thus far, the only user of this mechanism is for implementing TCP
> congestion control algorithms. These are clearly marked as GPL-only when
> implemented as modules (as seen by the use of EXPORT_SYMBOL_GPL for
> tcp_register_congestion_control()), so it seems like an oversight that this
> was not carried over to BPF implementations. And sine this is the only user
> of the struct_ops mechanism, just enforcing GPL-only for the struct_ops
> program type seems like the simplest way to fix this.
>
> Fixes: 0baf26b0fcd7 ("bpf: tcp: Support tcp_congestion_ops in bpf")
> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
> ---
> kernel/bpf/verifier.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 44e4ec1640f1..48dd0c0f087c 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -12166,6 +12166,11 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
> return -ENOTSUPP;
> }
>
> + if (!prog->gpl_compatible) {
> + verbose(env, "struct ops programs must have a GPL compatible license\n");
> + return -EINVAL;
> + }
> +
Thanks for the patch.
A nit. Instead of sitting in between of the attach_btf_id check
and expected_attach_type check, how about moving it to the beginning
of this function. Checking attach_btf_id and expected_attach_type
would make more sense to be done next to each other as in the current
code.
Acked-by: Martin KaFai Lau <kafai@xxxxxx>
