[PATCH bpf-next v5 0/2] Introduce a new kfunc of bpf_task_under_cgroup

[PATCH bpf-next v5 0/2] Introduce a new kfunc of bpf_task_under_cgroup

[Feng zhou]

From: Feng Zhou <zhoufeng.zf@bytedance.com>

Trace sched related functions, such as enqueue_task_fair, it is necessary to
specify a task instead of the current task which within a given cgroup.

Feng Zhou (2):
  bpf: Add bpf_task_under_cgroup() kfunc
  selftests/bpf: Add testcase for bpf_task_under_cgroup

Changelog:
v4->v5: Addressed comments from Yonghong Song
- Some code format modifications.
Details in here:
https://lore.kernel.org/all/20230428071737.43849-1-zhoufeng.zf@bytedance.com/

v3->v4: Addressed comments from Yonghong Song
- Modify test cases and test other tasks, not the current task.
Details in here:
https://lore.kernel.org/all/20230427023019.73576-1-zhoufeng.zf@bytedance.com/

v2->v3: Addressed comments from Alexei Starovoitov
- Modify the comment information of the function.
- Narrow down the testcase's hook point
Details in here:
https://lore.kernel.org/all/20230421090403.15515-1-zhoufeng.zf@bytedance.com/

v1->v2: Addressed comments from Alexei Starovoitov
- Add kfunc instead.
Details in here:
https://lore.kernel.org/all/20230420072657.80324-1-zhoufeng.zf@bytedance.com/

 kernel/bpf/helpers.c                          | 20 +++++++
 tools/testing/selftests/bpf/DENYLIST.s390x    |  1 +
 .../bpf/prog_tests/task_under_cgroup.c        | 54 +++++++++++++++++++
 .../bpf/progs/test_task_under_cgroup.c        | 51 ++++++++++++++++++
 4 files changed, 126 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

-- 
2.20.1

[PATCH bpf-next v5 1/2] bpf: Add bpf_task_under_cgroup() kfunc

[Feng zhou]

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 | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index bb6b4637ebf2..453cbd312366 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2149,6 +2149,25 @@ __bpf_kfunc struct cgroup *bpf_cgroup_from_id(u64 cgid)
 		return NULL;
 	return cgrp;
 }
+
+/**
+ * bpf_task_under_cgroup - wrap task_under_cgroup_hierarchy() as a kfunc, test
+ * task's membership of cgroup ancestry.
+ * @task: the task to be tested
+ * @ancestor: possible ancestor of @task's cgroup
+ *
+ * Tests whether @task's default cgroup hierarchy is a descendant of @ancestor.
+ * It follows all the same rules as cgroup_is_descendant, and only applies
+ * to the default hierarchy.
+ */
+__bpf_kfunc long bpf_task_under_cgroup(struct task_struct *task,
+				       struct cgroup *ancestor)
+{
+	if (unlikely(!ancestor || !task))
+		return -EINVAL;
+
+	return task_under_cgroup_hierarchy(task, ancestor);
+}
 #endif /* CONFIG_CGROUPS */
 
 /**
@@ -2400,6 +2419,7 @@ 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

Re: [PATCH bpf-next v5 1/2] bpf: Add bpf_task_under_cgroup() kfunc

[Yonghong Song]

On 5/3/23 8:15 PM, 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>

You can carry my Ack from previous revision since there
is no change to the patch.

Acked-by: Yonghong Song <yhs@fb.com>

Re: Re: [PATCH bpf-next v5 1/2] bpf: Add bpf_task_under_cgroup() kfunc

[Feng Zhou]

在 2023/5/4 22:29, Yonghong Song 写道:
> 
> 
> On 5/3/23 8:15 PM, 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>
> 
> You can carry my Ack from previous revision since there
> is no change to the patch.
> 
> Acked-by: Yonghong Song <yhs@fb.com>

Will do

[PATCH bpf-next v5 2/2] selftests/bpf: Add testcase for bpf_task_under_cgroup

[Feng zhou]

From: Feng Zhou <zhoufeng.zf@bytedance.com>

test_progs:
Tests new kfunc bpf_task_under_cgroup().

The bpf program saves the new task's pid 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 fork syscall, then check if
remote_pid and local_pid are unequal.

Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
---
 tools/testing/selftests/bpf/DENYLIST.s390x    |  1 +
 .../bpf/prog_tests/task_under_cgroup.c        | 54 +++++++++++++++++++
 .../bpf/progs/test_task_under_cgroup.c        | 51 ++++++++++++++++++
 3 files changed, 106 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/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
index c7463f3ec3c0..5061d9e24c16 100644
--- a/tools/testing/selftests/bpf/DENYLIST.s390x
+++ b/tools/testing/selftests/bpf/DENYLIST.s390x
@@ -26,3 +26,4 @@ user_ringbuf                             # failed to find kernel BTF type ID of
 verif_stats                              # trace_vprintk__open_and_load unexpected error: -9                           (?)
 xdp_bonding                              # failed to auto-attach program 'trace_on_entry': -524                        (trampoline)
 xdp_metadata                             # JIT does not support calling kernel function                                (kfunc)
+test_task_under_cgroup                   # JIT does not support calling kernel function                                (kfunc)
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..fa3a98eae5ef
--- /dev/null
+++ b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Bytedance */
+
+#include <sys/syscall.h>
+#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;
+	pid_t pid;
+
+	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->bss->remote_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;
+
+	pid = fork();
+	if (pid == 0)
+		exit(0);
+
+	ret = (pid == -1);
+	if (ASSERT_OK(ret, "fork process"))
+		wait(NULL);
+
+	test_task_under_cgroup__detach(skel);
+
+	ASSERT_NEQ(skel->bss->remote_pid, skel->rodata->local_pid,
+		   "test task_under_cgroup");
+
+cleanup:
+	close(foo);
+
+	test_task_under_cgroup__destroy(skel);
+}
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..79d98e65c7eb
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2023 Bytedance */
+
+#include <vmlinux.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_helpers.h>
+
+#include "bpf_misc.h"
+
+struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
+long bpf_task_under_cgroup(struct task_struct *task, struct cgroup *ancestor) __ksym;
+void bpf_cgroup_release(struct cgroup *p) __ksym;
+struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
+void bpf_task_release(struct task_struct *p) __ksym;
+
+const volatile int local_pid;
+const volatile __u64 cgid;
+int remote_pid;
+
+SEC("tp_btf/task_newtask")
+int BPF_PROG(handle__task_newtask, struct task_struct *task, u64 clone_flags)
+{
+	struct cgroup *cgrp = NULL;
+	struct task_struct *acquired;
+
+	if (local_pid != (bpf_get_current_pid_tgid() >> 32))
+		return 0;
+
+	acquired = bpf_task_acquire(task);
+	if (!acquired)
+		return 0;
+
+	if (local_pid == acquired->tgid)
+		goto out;
+
+	cgrp = bpf_cgroup_from_id(cgid);
+	if (!cgrp)
+		goto out;
+
+	if (bpf_task_under_cgroup(acquired, cgrp))
+		remote_pid = acquired->tgid;
+
+out:
+	if (acquired)
+		bpf_task_release(acquired);
+	if (cgrp)
+		bpf_cgroup_release(cgrp);
+	return 0;
+}
+
+char _license[] SEC("license") = "GPL";
-- 
2.20.1

Re: [PATCH bpf-next v5 2/2] selftests/bpf: Add testcase for bpf_task_under_cgroup

[Yonghong Song]

On 5/3/23 8:15 PM, Feng zhou wrote:
> From: Feng Zhou <zhoufeng.zf@bytedance.com>
> 
> test_progs:
> Tests new kfunc bpf_task_under_cgroup().
> 
> The bpf program saves the new task's pid 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 fork syscall, then check if
> remote_pid and local_pid are unequal.
> 
> Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>

Ack with a few nits below. You can carry my Ack in the
next revision.

Acked-by: Yonghong Song <yhs@fb.com>


> ---
>   tools/testing/selftests/bpf/DENYLIST.s390x    |  1 +
>   .../bpf/prog_tests/task_under_cgroup.c        | 54 +++++++++++++++++++
>   .../bpf/progs/test_task_under_cgroup.c        | 51 ++++++++++++++++++
>   3 files changed, 106 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/DENYLIST.s390x b/tools/testing/selftests/bpf/DENYLIST.s390x
> index c7463f3ec3c0..5061d9e24c16 100644
> --- a/tools/testing/selftests/bpf/DENYLIST.s390x
> +++ b/tools/testing/selftests/bpf/DENYLIST.s390x
> @@ -26,3 +26,4 @@ user_ringbuf                             # failed to find kernel BTF type ID of
>   verif_stats                              # trace_vprintk__open_and_load unexpected error: -9                           (?)
>   xdp_bonding                              # failed to auto-attach program 'trace_on_entry': -524                        (trampoline)
>   xdp_metadata                             # JIT does not support calling kernel function                                (kfunc)
> +test_task_under_cgroup                   # JIT does not support calling kernel function                                (kfunc)
> 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..fa3a98eae5ef
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
> @@ -0,0 +1,54 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2023 Bytedance */
> +
> +#include <sys/syscall.h>
> +#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;

You do not need to initialize 'foo' here.

> +	pid_t pid;
> +
> +	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->bss->remote_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;
> +
> +	pid = fork();
> +	if (pid == 0)
> +		exit(0);
> +
> +	ret = (pid == -1);
> +	if (ASSERT_OK(ret, "fork process"))
> +		wait(NULL);
> +
> +	test_task_under_cgroup__detach(skel);
> +
> +	ASSERT_NEQ(skel->bss->remote_pid, skel->rodata->local_pid,
> +		   "test task_under_cgroup");
> +
> +cleanup:
> +	close(foo);
> +
> +	test_task_under_cgroup__destroy(skel);

Let us just do:
cleanup:
	test_task_under_cgroup__destroy(skel);
	close(foo);

This is the reverse order of test__join_cgroup() and 
test_task_under_cgroup__open().

> +}
> 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..79d98e65c7eb
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
> @@ -0,0 +1,51 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2023 Bytedance */
> +
> +#include <vmlinux.h>
> +#include <bpf/bpf_tracing.h>
> +#include <bpf/bpf_helpers.h>
> +
> +#include "bpf_misc.h"
> +
> +struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
> +long bpf_task_under_cgroup(struct task_struct *task, struct cgroup *ancestor) __ksym;
> +void bpf_cgroup_release(struct cgroup *p) __ksym;
> +struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
> +void bpf_task_release(struct task_struct *p) __ksym;
> +
> +const volatile int local_pid;
> +const volatile __u64 cgid;
> +int remote_pid;
> +
> +SEC("tp_btf/task_newtask")
> +int BPF_PROG(handle__task_newtask, struct task_struct *task, u64 clone_flags)
> +{
> +	struct cgroup *cgrp = NULL;
> +	struct task_struct *acquired;
> +
> +	if (local_pid != (bpf_get_current_pid_tgid() >> 32))
> +		return 0;
> +
> +	acquired = bpf_task_acquire(task);
> +	if (!acquired)
> +		return 0;
> +
> +	if (local_pid == acquired->tgid)
> +		goto out;
> +
> +	cgrp = bpf_cgroup_from_id(cgid);
> +	if (!cgrp)
> +		goto out;
> +
> +	if (bpf_task_under_cgroup(acquired, cgrp))
> +		remote_pid = acquired->tgid;
> +
> +out:
> +	if (acquired)
> +		bpf_task_release(acquired);
> +	if (cgrp)
> +		bpf_cgroup_release(cgrp);

Let us do:
out:
	if (cgrp)
		bpf_cgroup_release(cgrp);
	bpf_task_release(acquired);

> +	return 0;
> +}
> +
> +char _license[] SEC("license") = "GPL";

Re: Re: [PATCH bpf-next v5 2/2] selftests/bpf: Add testcase for bpf_task_under_cgroup

[Feng Zhou]

在 2023/5/4 22:46, Yonghong Song 写道:
> 
> 
> On 5/3/23 8:15 PM, Feng zhou wrote:
>> From: Feng Zhou <zhoufeng.zf@bytedance.com>
>>
>> test_progs:
>> Tests new kfunc bpf_task_under_cgroup().
>>
>> The bpf program saves the new task's pid 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 fork syscall, then check if
>> remote_pid and local_pid are unequal.
>>
>> Signed-off-by: Feng Zhou <zhoufeng.zf@bytedance.com>
> 
> Ack with a few nits below. You can carry my Ack in the
> next revision.
> 
> Acked-by: Yonghong Song <yhs@fb.com>
> 
> 

Will do

>> ---
>>   tools/testing/selftests/bpf/DENYLIST.s390x    |  1 +
>>   .../bpf/prog_tests/task_under_cgroup.c        | 54 +++++++++++++++++++
>>   .../bpf/progs/test_task_under_cgroup.c        | 51 ++++++++++++++++++
>>   3 files changed, 106 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/DENYLIST.s390x 
>> b/tools/testing/selftests/bpf/DENYLIST.s390x
>> index c7463f3ec3c0..5061d9e24c16 100644
>> --- a/tools/testing/selftests/bpf/DENYLIST.s390x
>> +++ b/tools/testing/selftests/bpf/DENYLIST.s390x
>> @@ -26,3 +26,4 @@ user_ringbuf                             # failed to 
>> find kernel BTF type ID of
>>   verif_stats                              # 
>> trace_vprintk__open_and_load unexpected error: 
>> -9                           (?)
>>   xdp_bonding                              # failed to auto-attach 
>> program 'trace_on_entry': -524                        (trampoline)
>>   xdp_metadata                             # JIT does not support 
>> calling kernel function                                (kfunc)
>> +test_task_under_cgroup                   # JIT does not support 
>> calling kernel function                                (kfunc)
>> 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..fa3a98eae5ef
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/prog_tests/task_under_cgroup.c
>> @@ -0,0 +1,54 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2023 Bytedance */
>> +
>> +#include <sys/syscall.h>
>> +#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;
> 
> You do not need to initialize 'foo' here.
> 
>> +    pid_t pid;
>> +
>> +    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->bss->remote_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;
>> +
>> +    pid = fork();
>> +    if (pid == 0)
>> +        exit(0);
>> +
>> +    ret = (pid == -1);
>> +    if (ASSERT_OK(ret, "fork process"))
>> +        wait(NULL);
>> +
>> +    test_task_under_cgroup__detach(skel);
>> +
>> +    ASSERT_NEQ(skel->bss->remote_pid, skel->rodata->local_pid,
>> +           "test task_under_cgroup");
>> +
>> +cleanup:
>> +    close(foo);
>> +
>> +    test_task_under_cgroup__destroy(skel);
> 
> Let us just do:
> cleanup:
>      test_task_under_cgroup__destroy(skel);
>      close(foo);
> 
> This is the reverse order of test__join_cgroup() and 
> test_task_under_cgroup__open().
> 
>> +}
>> 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..79d98e65c7eb
>> --- /dev/null
>> +++ b/tools/testing/selftests/bpf/progs/test_task_under_cgroup.c
>> @@ -0,0 +1,51 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/* Copyright (c) 2023 Bytedance */
>> +
>> +#include <vmlinux.h>
>> +#include <bpf/bpf_tracing.h>
>> +#include <bpf/bpf_helpers.h>
>> +
>> +#include "bpf_misc.h"
>> +
>> +struct cgroup *bpf_cgroup_from_id(u64 cgid) __ksym;
>> +long bpf_task_under_cgroup(struct task_struct *task, struct cgroup 
>> *ancestor) __ksym;
>> +void bpf_cgroup_release(struct cgroup *p) __ksym;
>> +struct task_struct *bpf_task_acquire(struct task_struct *p) __ksym;
>> +void bpf_task_release(struct task_struct *p) __ksym;
>> +
>> +const volatile int local_pid;
>> +const volatile __u64 cgid;
>> +int remote_pid;
>> +
>> +SEC("tp_btf/task_newtask")
>> +int BPF_PROG(handle__task_newtask, struct task_struct *task, u64 
>> clone_flags)
>> +{
>> +    struct cgroup *cgrp = NULL;
>> +    struct task_struct *acquired;
>> +
>> +    if (local_pid != (bpf_get_current_pid_tgid() >> 32))
>> +        return 0;
>> +
>> +    acquired = bpf_task_acquire(task);
>> +    if (!acquired)
>> +        return 0;
>> +
>> +    if (local_pid == acquired->tgid)
>> +        goto out;
>> +
>> +    cgrp = bpf_cgroup_from_id(cgid);
>> +    if (!cgrp)
>> +        goto out;
>> +
>> +    if (bpf_task_under_cgroup(acquired, cgrp))
>> +        remote_pid = acquired->tgid;
>> +
>> +out:
>> +    if (acquired)
>> +        bpf_task_release(acquired);
>> +    if (cgrp)
>> +        bpf_cgroup_release(cgrp);
> 
> Let us do:
> out:
>      if (cgrp)
>          bpf_cgroup_release(cgrp);
>      bpf_task_release(acquired);
> 
>> +    return 0;
>> +}
>> +
>> +char _license[] SEC("license") = "GPL";