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bpf: Enforce that struct_ops programs be GPL-only

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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. Since 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: 0baf26b0fc ("bpf: tcp: Support tcp_congestion_ops in bpf")
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210326100314.121853-1-toke@redhat.com
This commit is contained in:
Toke Høiland-Jørgensen 2021-03-26 11:03:13 +01:00 committed by Daniel Borkmann
parent 6032ebb54c
commit 12aa8a9467
1 changed files with 5 additions and 0 deletions
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5
kernel/bpf/verifier.c
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@ -12158,6 +12158,11 @@ static int check_struct_ops_btf_id(struct bpf_verifier_env *env)
u32 btf_id, member_idx;
const char *mname;
if (!prog->gpl_compatible) {
verbose(env, "struct ops programs must have a GPL compatible license\n");
return -EINVAL;
}
btf_id = prog->aux->attach_btf_id;
st_ops = bpf_struct_ops_find(btf_id);
if (!st_ops) {