On Fri, Apr 21, 2023 at 05:04:02PM +0800, Feng zhou wrote:

From: Feng Zhou zhoufeng.zf@bytedance.com

Add a kfunc that's similar to the bpf_current_task_under_cgroup. The difference is that it is a designated task.

When hook sched related functions, sometimes it is necessary to specify a task instead of the current task.

Signed-off-by: Feng Zhou zhoufeng.zf@bytedance.com

kernel/bpf/helpers.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 00e5fb0682ac..88e3247b5c44 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -2142,6 +2142,24 @@ __bpf_kfunc struct cgroup *bpf_cgroup_from_id(u64 cgid) return NULL; return cgrp; }

+/**

• • bpf_task_under_cgroup - Check whether the task is a given subset of the
• • cgroup2 hierarchy. The cgroup2 to test is assigned by cgrp.

That doesn't read right.

• • @cgrp: assigned cgrp.
• • @task: assigned task.

This is also wrong. Please copy paste from task_under_cgroup_hierarchy.

• */

+__bpf_kfunc int bpf_task_under_cgroup(struct cgroup *cgrp,

• 		      struct task_struct *task)
  

return type needs to be 'long'. 'int' might have issues. Also the args should be task, cgrp to match task_under_cgroup_hierarchy.

+{

• if (unlikely(!cgrp))

• return -EAGAIN;
  

• if (unlikely(!task))

• return -ENOENT;
  

Please do if (unlikely(!cgrp || !task)) return -EINVAL;

• return task_under_cgroup_hierarchy(task, cgrp);

+} #endif /* CONFIG_CGROUPS */ /** @@ -2341,6 +2359,7 @@ BTF_ID_FLAGS(func, bpf_cgroup_acquire, KF_ACQUIRE | KF_RCU | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_cgroup_release, KF_RELEASE) BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | KF_RCU | KF_RET_NULL) BTF_ID_FLAGS(func, bpf_cgroup_from_id, KF_ACQUIRE | KF_RET_NULL) +BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU) #endif BTF_ID_FLAGS(func, bpf_task_from_pid, KF_ACQUIRE | KF_RET_NULL) BTF_SET8_END(generic_btf_ids) -- 2.20.1

On Fri, Apr 21, 2023 at 05:04:03PM +0800, Feng zhou wrote:

From: Feng Zhou zhoufeng.zf@bytedance.com

test_progs: Tests new kfunc bpf_task_under_cgroup().

The bpf program saves the pid which call the getuid syscall within a given cgroup to the remote_pid, which is convenient for the user-mode program to verify the test correctness.

The user-mode program creates its own mount namespace, and mounts the cgroupsv2 hierarchy in there, call the getuid syscall, then check if remote_pid and local_pid are equal.

Signed-off-by: Feng Zhou zhoufeng.zf@bytedance.com

.../bpf/prog_tests/task_under_cgroup.c | 46 +++++++++++++++++++ .../selftests/bpf/progs/cgrp_kfunc_common.h | 1 + .../bpf/progs/test_task_under_cgroup.c | 40 ++++++++++++++++ 3 files changed, 87 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c create mode 100644 tools/testing/selftests/bpf/progs/test_task_under_cgroup.c

diff --git a/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c new file mode 100644 index 000000000000..bd3deb469938 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c @@ -0,0 +1,46 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2023 Bytedance */

+#include <test_progs.h> +#include <cgroup_helpers.h> +#include "test_task_under_cgroup.skel.h"

+#define FOO "/foo"

+void test_task_under_cgroup(void) +{

• struct test_task_under_cgroup *skel;
• int ret, foo = -1;
• foo = test__join_cgroup(FOO);
• if (!ASSERT_OK(foo < 0, "cgroup_join_foo"))

• return;
  

• skel = test_task_under_cgroup__open();
• if (!ASSERT_OK_PTR(skel, "test_task_under_cgroup__open"))

• goto cleanup;
  

• skel->rodata->local_pid = getpid();
• skel->rodata->cgid = get_cgroup_id(FOO);
• ret = test_task_under_cgroup__load(skel);
• if (!ASSERT_OK(ret, "test_task_under_cgroup__load"))

• goto cleanup;
  

• ret = test_task_under_cgroup__attach(skel);
• if (!ASSERT_OK(ret, "test_task_under_cgroup__attach"))

• goto cleanup;
  

• syscall(__NR_getuid);
• test_task_under_cgroup__detach(skel);
• ASSERT_EQ(skel->bss->remote_pid, skel->rodata->local_pid,

•   "test task_under_cgroup");
  

+cleanup:

• if (foo)

• close(foo);
  

Looks wrong. should be if (foo >= 0) ?

• test_task_under_cgroup__destroy(skel);

+} diff --git a/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h b/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h index 22914a70db54..41b3ea231698 100644 --- a/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h +++ b/tools/testing/selftests/bpf/progs/cgrp_kfunc_common.h @@ -26,6 +26,7 @@ struct cgroup *bpf_cgroup_ancestor(struct cgroup *cgrp, int level) __ksym; struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym; void bpf_rcu_read_lock(void) __ksym; void bpf_rcu_read_unlock(void) __ksym; +int bpf_task_under_cgroup(struct cgroup *cgrp, struct task_struct *task) __ksym; static inline struct __cgrps_kfunc_map_value *cgrps_kfunc_map_value_lookup(struct cgroup *cgrp) { diff --git a/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c new file mode 100644 index 000000000000..e2740f9b029d --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c @@ -0,0 +1,40 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2023 Bytedance */

+#include <vmlinux.h> +#include <asm/unistd.h> +#include <bpf/bpf_tracing.h> +#include <bpf/bpf_helpers.h>

+#include "cgrp_kfunc_common.h"

+const volatile int local_pid; +const volatile long cgid; +int remote_pid;

+SEC("tp_btf/sys_enter")

pls narrow down to specific syscall. Like you use in user space part: getuid

Also add this test to denylist.s390. See BPF CI failure.

+int BPF_PROG(sysenter, struct pt_regs *regs, long id) +{

• struct cgroup *cgrp;
• if (id != __NR_getuid)

• return 0;
  

• if (local_pid != (bpf_get_current_pid_tgid() >> 32))

• return 0;
  

• cgrp = bpf_cgroup_from_id(cgid);
• if (!cgrp)

• return 0;
  

• if (!bpf_task_under_cgroup(cgrp, bpf_get_current_task_btf()))

• goto out;
  

• remote_pid = local_pid;

+out:

• bpf_cgroup_release(cgrp);
• return 0;

+}

+char _license[] SEC("license") = "GPL";

2.20.1