selftests/bpf: Add selftests for cgroup1 hierarchy

Add selftests for cgroup1 hierarchy.
The result as follows,

  $ tools/testing/selftests/bpf/test_progs --name=cgroup1_hierarchy
  #36/1    cgroup1_hierarchy/test_cgroup1_hierarchy:OK
  #36/2    cgroup1_hierarchy/test_root_cgid:OK
  #36/3    cgroup1_hierarchy/test_invalid_level:OK
  #36/4    cgroup1_hierarchy/test_invalid_cgid:OK
  #36/5    cgroup1_hierarchy/test_invalid_hid:OK
  #36/6    cgroup1_hierarchy/test_invalid_cgrp_name:OK
  #36/7    cgroup1_hierarchy/test_invalid_cgrp_name2:OK
  #36/8    cgroup1_hierarchy/test_sleepable_prog:OK
  #36      cgroup1_hierarchy:OK
  Summary: 1/8 PASSED, 0 SKIPPED, 0 FAILED

Besides, I also did some stress test similar to the patch #2 in this
series, as follows (with CONFIG_PROVE_RCU_LIST enabled):

- Continuously mounting and unmounting named cgroups in some tasks,
  for example:

  cgrp_name=$1
  while true
  do
      mount -t cgroup -o none,name=$cgrp_name none /$cgrp_name
      umount /$cgrp_name
  done

- Continuously run this selftest concurrently,
  while true; do ./test_progs --name=cgroup1_hierarchy; done

They can ran successfully without any RCU warnings in dmesg.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Link: https://lore.kernel.org/r/20231111090034.4248-7-laoar.shao@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/prog_tests/cgroup1_hierarchy.c

@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2023 Yafang Shao <laoar.shao@gmail.com> */
+
+#include <sys/types.h>
+#include <unistd.h>
+#include <test_progs.h>
+#include "cgroup_helpers.h"
+#include "test_cgroup1_hierarchy.skel.h"
+
+static void bpf_cgroup1(struct test_cgroup1_hierarchy *skel)
+{
+	struct bpf_link *lsm_link, *fentry_link;
+	int err;
+
+	/* Attach LSM prog first */
+	lsm_link = bpf_program__attach_lsm(skel->progs.lsm_run);
+	if (!ASSERT_OK_PTR(lsm_link, "lsm_attach"))
+		return;
+
+	/* LSM prog will be triggered when attaching fentry */
+	fentry_link = bpf_program__attach_trace(skel->progs.fentry_run);
+	ASSERT_NULL(fentry_link, "fentry_attach_fail");
+
+	err = bpf_link__destroy(lsm_link);
+	ASSERT_OK(err, "destroy_lsm");
+}
+
+static void bpf_cgroup1_sleepable(struct test_cgroup1_hierarchy *skel)
+{
+	struct bpf_link *lsm_link, *fentry_link;
+	int err;
+
+	/* Attach LSM prog first */
+	lsm_link = bpf_program__attach_lsm(skel->progs.lsm_s_run);
+	if (!ASSERT_OK_PTR(lsm_link, "lsm_attach"))
+		return;
+
+	/* LSM prog will be triggered when attaching fentry */
+	fentry_link = bpf_program__attach_trace(skel->progs.fentry_run);
+	ASSERT_NULL(fentry_link, "fentry_attach_fail");
+
+	err = bpf_link__destroy(lsm_link);
+	ASSERT_OK(err, "destroy_lsm");
+}
+
+static void bpf_cgroup1_invalid_id(struct test_cgroup1_hierarchy *skel)
+{
+	struct bpf_link *lsm_link, *fentry_link;
+	int err;
+
+	/* Attach LSM prog first */
+	lsm_link = bpf_program__attach_lsm(skel->progs.lsm_run);
+	if (!ASSERT_OK_PTR(lsm_link, "lsm_attach"))
+		return;
+
+	/* LSM prog will be triggered when attaching fentry */
+	fentry_link = bpf_program__attach_trace(skel->progs.fentry_run);
+	if (!ASSERT_OK_PTR(fentry_link, "fentry_attach_success"))
+		goto cleanup;
+
+	err = bpf_link__destroy(fentry_link);
+	ASSERT_OK(err, "destroy_lsm");
+
+cleanup:
+	err = bpf_link__destroy(lsm_link);
+	ASSERT_OK(err, "destroy_fentry");
+}
+
+void test_cgroup1_hierarchy(void)
+{
+	struct test_cgroup1_hierarchy *skel;
+	__u64 current_cgid;
+	int hid, err;
+
+	skel = test_cgroup1_hierarchy__open();
+	if (!ASSERT_OK_PTR(skel, "open"))
+		return;
+
+	skel->bss->target_pid = getpid();
+
+	err = bpf_program__set_attach_target(skel->progs.fentry_run, 0, "bpf_fentry_test1");
+	if (!ASSERT_OK(err, "fentry_set_target"))
+		goto destroy;
+
+	err = test_cgroup1_hierarchy__load(skel);
+	if (!ASSERT_OK(err, "load"))
+		goto destroy;
+
+	/* Setup cgroup1 hierarchy */
+	err = setup_classid_environment();
+	if (!ASSERT_OK(err, "setup_classid_environment"))
+		goto destroy;
+
+	err = join_classid();
+	if (!ASSERT_OK(err, "join_cgroup1"))
+		goto cleanup;
+
+	current_cgid = get_classid_cgroup_id();
+	if (!ASSERT_GE(current_cgid, 0, "cgroup1 id"))
+		goto cleanup;
+
+	hid = get_cgroup1_hierarchy_id("net_cls");
+	if (!ASSERT_GE(hid, 0, "cgroup1 id"))
+		goto cleanup;
+	skel->bss->target_hid = hid;
+
+	if (test__start_subtest("test_cgroup1_hierarchy")) {
+		skel->bss->target_ancestor_cgid = current_cgid;
+		bpf_cgroup1(skel);
+	}
+
+	if (test__start_subtest("test_root_cgid")) {
+		skel->bss->target_ancestor_cgid = 1;
+		skel->bss->target_ancestor_level = 0;
+		bpf_cgroup1(skel);
+	}
+
+	if (test__start_subtest("test_invalid_level")) {
+		skel->bss->target_ancestor_cgid = 1;
+		skel->bss->target_ancestor_level = 1;
+		bpf_cgroup1_invalid_id(skel);
+	}
+
+	if (test__start_subtest("test_invalid_cgid")) {
+		skel->bss->target_ancestor_cgid = 0;
+		bpf_cgroup1_invalid_id(skel);
+	}
+
+	if (test__start_subtest("test_invalid_hid")) {
+		skel->bss->target_ancestor_cgid = 1;
+		skel->bss->target_ancestor_level = 0;
+		skel->bss->target_hid = -1;
+		bpf_cgroup1_invalid_id(skel);
+	}
+
+	if (test__start_subtest("test_invalid_cgrp_name")) {
+		skel->bss->target_hid = get_cgroup1_hierarchy_id("net_cl");
+		skel->bss->target_ancestor_cgid = current_cgid;
+		bpf_cgroup1_invalid_id(skel);
+	}
+
+	if (test__start_subtest("test_invalid_cgrp_name2")) {
+		skel->bss->target_hid = get_cgroup1_hierarchy_id("net_cls,");
+		skel->bss->target_ancestor_cgid = current_cgid;
+		bpf_cgroup1_invalid_id(skel);
+	}
+
+	if (test__start_subtest("test_sleepable_prog")) {
+		skel->bss->target_hid = hid;
+		skel->bss->target_ancestor_cgid = current_cgid;
+		bpf_cgroup1_sleepable(skel);
+	}
+
+cleanup:
+	cleanup_classid_environment();
+destroy:
+	test_cgroup1_hierarchy__destroy(skel);
+}

tools/testing/selftests/bpf/progs/test_cgroup1_hierarchy.c

@@ -0,0 +1,71 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2023 Yafang Shao <laoar.shao@gmail.com> */
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+__u32 target_ancestor_level;
+__u64 target_ancestor_cgid;
+int target_pid, target_hid;
+
+struct cgroup *bpf_task_get_cgroup1(struct task_struct *task, int hierarchy_id) __ksym;
+struct cgroup *bpf_cgroup_ancestor(struct cgroup *cgrp, int level) __ksym;
+void bpf_cgroup_release(struct cgroup *cgrp) __ksym;
+
+static int bpf_link_create_verify(int cmd)
+{
+	struct cgroup *cgrp, *ancestor;
+	struct task_struct *task;
+	int ret = 0;
+
+	if (cmd != BPF_LINK_CREATE)
+		return 0;
+
+	task = bpf_get_current_task_btf();
+
+	/* Then it can run in parallel with others */
+	if (task->pid != target_pid)
+		return 0;
+
+	cgrp = bpf_task_get_cgroup1(task, target_hid);
+	if (!cgrp)
+		return 0;
+
+	/* Refuse it if its cgid or its ancestor's cgid is the target cgid */
+	if (cgrp->kn->id == target_ancestor_cgid)
+		ret = -1;
+
+	ancestor = bpf_cgroup_ancestor(cgrp, target_ancestor_level);
+	if (!ancestor)
+		goto out;
+
+	if (ancestor->kn->id == target_ancestor_cgid)
+		ret = -1;
+	bpf_cgroup_release(ancestor);
+
+out:
+	bpf_cgroup_release(cgrp);
+	return ret;
+}
+
+SEC("lsm/bpf")
+int BPF_PROG(lsm_run, int cmd, union bpf_attr *attr, unsigned int size)
+{
+	return bpf_link_create_verify(cmd);
+}
+
+SEC("lsm.s/bpf")
+int BPF_PROG(lsm_s_run, int cmd, union bpf_attr *attr, unsigned int size)
+{
+	return bpf_link_create_verify(cmd);
+}
+
+SEC("fentry")
+int BPF_PROG(fentry_run)
+{
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";