Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
selftests/sched_ext: Add non_scx_kfunc_deny test
Verify that the BPF verifier rejects a non-SCX struct_ops program
(tcp_congestion_ops) that attempts to call an SCX kfunc (scx_bpf_kick_cpu).
The test expects the load to fail with -EACCES from scx_kfunc_context_filter.
Signed-off-by: Cheng-Yang Chou <yphbchou0911@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
authored by
Cheng-Yang Chou
and committed by
Tejun Heo
5897ca15
2d2b026c
+92
+1
tools/testing/selftests/sched_ext/Makefile
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tools/testing/selftests/sched_ext/Makefile
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tools/testing/selftests/sched_ext/non_scx_kfunc_deny.bpf.c
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tools/testing/selftests/sched_ext/non_scx_kfunc_deny.bpf.c
···
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Verify that context-sensitive SCX kfuncs (even "unlocked" ones) are
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* restricted to only SCX struct_ops programs. Non-SCX struct_ops programs,
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* such as TCP congestion control programs, should be rejected by the BPF
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* verifier when attempting to call these kfuncs.
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*
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* Copyright (C) 2026 Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>
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* Copyright (C) 2026 Cheng-Yang Chou <yphbchou0911@gmail.com>
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*/
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#include <vmlinux.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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/* SCX kfunc from scx_kfunc_ids_any set */
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void scx_bpf_kick_cpu(s32 cpu, u64 flags) __ksym;
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SEC("struct_ops/ssthresh")
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__u32 BPF_PROG(tcp_ca_ssthresh, struct sock *sk)
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{
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/*
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* This call should be rejected by the verifier because this is a
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* TCP congestion control program (non-SCX struct_ops).
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*/
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scx_bpf_kick_cpu(0, 0);
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return 2;
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}
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SEC("struct_ops/cong_avoid")
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void BPF_PROG(tcp_ca_cong_avoid, struct sock *sk, __u32 ack, __u32 acked) {}
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SEC("struct_ops/undo_cwnd")
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__u32 BPF_PROG(tcp_ca_undo_cwnd, struct sock *sk) { return 2; }
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SEC(".struct_ops")
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struct tcp_congestion_ops tcp_non_scx_ca = {
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.ssthresh = (void *)tcp_ca_ssthresh,
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.cong_avoid = (void *)tcp_ca_cong_avoid,
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.undo_cwnd = (void *)tcp_ca_undo_cwnd,
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.name = "tcp_kfunc_deny",
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};
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char _license[] SEC("license") = "GPL";
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tools/testing/selftests/sched_ext/non_scx_kfunc_deny.c
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tools/testing/selftests/sched_ext/non_scx_kfunc_deny.c
···
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/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Verify that context-sensitive SCX kfuncs (even "unlocked" ones) are
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* restricted to only SCX struct_ops programs. Non-SCX struct_ops programs,
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* such as TCP congestion control programs, should be rejected by the BPF
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* verifier when attempting to call these kfuncs.
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*
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* Copyright (C) 2026 Ching-Chun (Jim) Huang <jserv@ccns.ncku.edu.tw>
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* Copyright (C) 2026 Cheng-Yang Chou <yphbchou0911@gmail.com>
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*/
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#include <bpf/bpf.h>
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#include <scx/common.h>
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#include <unistd.h>
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#include <errno.h>
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#include <stdio.h>
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#include "non_scx_kfunc_deny.bpf.skel.h"
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#include "scx_test.h"
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static enum scx_test_status run(void *ctx)
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{
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struct non_scx_kfunc_deny *skel;
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int err;
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skel = non_scx_kfunc_deny__open();
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if (!skel) {
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SCX_ERR("Failed to open skel");
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return SCX_TEST_FAIL;
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}
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err = non_scx_kfunc_deny__load(skel);
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non_scx_kfunc_deny__destroy(skel);
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if (err == 0) {
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SCX_ERR("non-SCX BPF program loaded when it should have been rejected");
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return SCX_TEST_FAIL;
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}
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return SCX_TEST_PASS;
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}
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struct scx_test non_scx_kfunc_deny = {
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.name = "non_scx_kfunc_deny",
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.description = "Verify that non-SCX struct_ops programs cannot call SCX kfuncs",
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.run = run,
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};
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REGISTER_SCX_TEST(&non_scx_kfunc_deny)