From: Toke Høiland-Jørgensen toke@redhat.com
commit 12aa8a9467b354ef893ce0fc5719a4de4949a9fb upstream.
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: 0baf26b0fcd7 ("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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- kernel/bpf/verifier.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -11429,6 +11429,11 @@ static int check_struct_ops_btf_id(struc 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) {