[PATCH bpf-next] selftests/bpf: Fix cgroup_mprog_ordering failure due to uninitialized variable

[PATCH bpf-next] selftests/bpf: Fix cgroup_mprog_ordering failure due to uninitialized variable

[Yonghong Song]

On arm64, the cgroup_mprog_ordering selftest failed with test_progs run
when building with clang compiler. The reason is due to socklen_t optlen
not initialized.

In kernel function do_ip_getsockopt(), we have

        if (copy_from_sockptr(&len, optlen, sizeof(int)))
                return -EFAULT;
        if (len < 0)
                return -EINVAL;

The above 'len' variable is a negative value and hence the test failed.

But the test is okay on x86_64. I checked the x86_64 asm code and I didn't
see explicit initialization of 'optlen' but its value is 0 so kernel
didn't return error. This should be a pure luck.

Fix the bug by initializing 'oplen' var properly.

Fixes: e422d5f118e4 ("selftests/bpf: Add two selftests for mprog API based cgroup progs")
Signed-off-by: Yonghong Song <yonghong.song@linux.dev>
---
 tools/testing/selftests/bpf/prog_tests/cgroup_mprog_ordering.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/cgroup_mprog_ordering.c b/tools/testing/selftests/bpf/prog_tests/cgroup_mprog_ordering.c
index 4a4e9710b474..a36d2e968bc5 100644
--- a/tools/testing/selftests/bpf/prog_tests/cgroup_mprog_ordering.c
+++ b/tools/testing/selftests/bpf/prog_tests/cgroup_mprog_ordering.c
@@ -12,7 +12,7 @@ static int run_getsockopt_test(int cg_parent, int sock_fd, bool has_relative_fd)
 	struct cgroup_preorder *skel = NULL;
 	struct bpf_program *prog;
 	__u8 *result, buf;
-	socklen_t optlen;
+	socklen_t optlen = 1;
 	int err = 0;
 
 	skel = cgroup_preorder__open_and_load();
-- 
2.47.1

Re: [PATCH bpf-next] selftests/bpf: Fix cgroup_mprog_ordering failure due to uninitialized variable

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Wed, 11 Jun 2025 09:21:03 -0700 you wrote:
> On arm64, the cgroup_mprog_ordering selftest failed with test_progs run
> when building with clang compiler. The reason is due to socklen_t optlen
> not initialized.
> 
> In kernel function do_ip_getsockopt(), we have
> 
>         if (copy_from_sockptr(&len, optlen, sizeof(int)))
>                 return -EFAULT;
>         if (len < 0)
>                 return -EINVAL;
> 
> [...]

Here is the summary with links:
  - [bpf-next] selftests/bpf: Fix cgroup_mprog_ordering failure due to uninitialized variable
    https://git.kernel.org/bpf/bpf-next/c/517b088a846b

You are awesome, thank you!
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