[PATCH -next] selftests/landlock: Fix selftest ptrace_test run fail

[limin]

cat /proc/cmdline

BOOT_IMAGE=/vmlinuz-6.1.0-next-20221116 
root=UUID=a65b3a79-dc02-4728-8a0c-5cf24f4ae08b ro 
systemd.unified_cgroup_hierarchy=1 cgroup_no_v1=all


On 2022/11/29 19:03, Mickaël Salaün wrote:
> I tested with next-20221116 and all tests are OK. Could you share your 
> kernel configuration with a link? What is the content of /proc/cmdline?
>
> On 29/11/2022 02:42, limin wrote:
>> I run test on Linux ubuntu2204 6.1.0-next-20221116
>>
>> I did't use yama.
>>
>> you can reproduce by this step:
>>
>> cd kernel_src
>>
>> cd tools/testing/selftests/landlock/
>> make
>> ./ptrace_test
>>
>>
>>
>>
>> On 2022/11/29 3:44, Mickaël Salaün wrote:
>>> This patch changes the test semantic and then cannot work on my test
>>> environment. On which kernel did you run test? Do you use Yama or
>>> something similar?
>>>
>>> On 28/11/2022 03:04, limin wrote:
>>>> Tests PTRACE_ATTACH and PTRACE_MODE_READ on the parent,
>>>> trace parent return -1 when child== 0
>>>> How to reproduce warning:
>>>> $ make -C tools/testing/selftests TARGETS=landlock run_tests
>>>>
>>>> Signed-off-by: limin <limin100 at huawei.com>
>>>> ---
>>>>    tools/testing/selftests/landlock/ptrace_test.c | 5 ++---
>>>>    1 file changed, 2 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/tools/testing/selftests/landlock/ptrace_test.c
>>>> b/tools/testing/selftests/landlock/ptrace_test.c
>>>> index c28ef98ff3ac..88c4dc63eea0 100644
>>>> --- a/tools/testing/selftests/landlock/ptrace_test.c
>>>> +++ b/tools/testing/selftests/landlock/ptrace_test.c
>>>> @@ -267,12 +267,11 @@ TEST_F(hierarchy, trace)
>>>>            /* Tests PTRACE_ATTACH and PTRACE_MODE_READ on the 
>>>> parent. */
>>>>            err_proc_read = test_ptrace_read(parent);
>>>>            ret = ptrace(PTRACE_ATTACH, parent, NULL, 0);
>>>> +        EXPECT_EQ(-1, ret);
>>>> +        EXPECT_EQ(EPERM, errno);
>>>>            if (variant->domain_child) {
>>>> -            EXPECT_EQ(-1, ret);
>>>> -            EXPECT_EQ(EPERM, errno);
>>>>                EXPECT_EQ(EACCES, err_proc_read);
>>>>            } else {
>>>> -            EXPECT_EQ(0, ret);
>>>>                EXPECT_EQ(0, err_proc_read);
>>>>            }
>>>>            if (ret == 0) {