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

[Mickaël Salaün]

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) {