bpf: Allow LSM programs to use bpf spin locks (9e7a4d98) · Commits · 戴 / test

Usage of spin locks was not allowed for tracing programs due to insufficient preemption checks. The verifier does not currently prevent LSM programs from using spin locks, but the helpers are not exposed via bpf_lsm_func_proto. Based on the discussion in [1], non-sleepable LSM programs should be able to use bpf_spin_{lock, unlock}. Sleepable LSM programs can be preempted which means that allowng spin locks will need more work (disabling preemption and the verifier ensuring that no sleepable helpers are called when a spin lock is held). [1]: https://lore.kernel.org/bpf/20201103153132.2717326-1-kpsingh@chromium.org/T/#md601a053229287659071600d3483523f752cd2fb Signed-off-by:

KP Singh <kpsingh@google.com> Signed-off-by:

Alexei Starovoitov <ast@kernel.org> Acked-by:

Song Liu <songliubraving@fb.com> Acked-by:

Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20201106103747.2780972-2-kpsingh@chromium.org

kernel/bpf/bpf_lsm.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -59,6 +59,10 @@ bpf_lsm_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
		return &bpf_sk_storage_get_proto;
		case BPF_FUNC_sk_storage_delete:
		return &bpf_sk_storage_delete_proto;
		case BPF_FUNC_spin_lock:
		return &bpf_spin_lock_proto;
		case BPF_FUNC_spin_unlock:
		return &bpf_spin_unlock_proto;
		default:
		return tracing_prog_func_proto(func_id, prog);
		}

kernel/bpf/verifier.c

+15 −5

Original line number	Diff line number	Diff line
		@@ -9719,13 +9719,23 @@ static int check_map_prog_compatibility(struct bpf_verifier_env *env,
		verbose(env, "trace type programs with run-time allocated hash maps are unsafe. Switch to preallocated hash maps.\n");
		}

		if ((is_tracing_prog_type(prog_type) \|\|
		prog_type == BPF_PROG_TYPE_SOCKET_FILTER) &&
		map_value_has_spin_lock(map)) {
		if (map_value_has_spin_lock(map)) {
		if (prog_type == BPF_PROG_TYPE_SOCKET_FILTER) {
		verbose(env, "socket filter progs cannot use bpf_spin_lock yet\n");
		return -EINVAL;
		}

		if (is_tracing_prog_type(prog_type)) {
		verbose(env, "tracing progs cannot use bpf_spin_lock yet\n");
		return -EINVAL;
		}

		if (prog->aux->sleepable) {
		verbose(env, "sleepable progs cannot use bpf_spin_lock yet\n");
		return -EINVAL;
		}
		}

		if ((bpf_prog_is_dev_bound(prog->aux) \|\| bpf_map_is_dev_bound(map)) &&
		!bpf_offload_prog_map_match(prog, map)) {
		verbose(env, "offload device mismatch between prog and map\n");

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