OpenExecutable permission check prevents uprobe attachment to shared libraries without execute bit

[isubuz]

Describe the bug

OpenExecutable in v0.21.0 rejects files without the execute permission bit:

if info.Mode()&permExec == 0 {
    return nil, fmt.Errorf("file %s is not executable", path)
}

This breaks uprobe attachment to shared libraries that don't have +x. A common case is pip-installed CUDA libraries (e.g. libcudart.so.12) which ship with 0644 permissions.

PR #1938 moved ELF type validation into address() so that callers providing UprobeOptions.Address can skip it entirely, but the permExec check in OpenExecutable runs before Uprobe() is ever called, so the lazy validation is unreachable for these files.

Removing the permission check would match the intent described in #1938.

Or am I missing something?

How to reproduce

Calling link.OpenExecutable(<path to .so file w/o +x>)

Version information

github.com/cilium/ebpf v0.21.0

[ti-mo]

Yeah, I don't think there's a strong reason to check for the executable bit. Just checking if the path exists should be fine. We try to be as helpful as we can to the user, but in doing so we've added an extra constraint.

@isubuz Would you be up for sending a patch to remove the check?

[isubuz]

Sure, will do.

[shaunduncan]

Hi, I ran into this issue earlier today and had rollback and pin my version to v0.20.0. The change looked straightforward enough so I submitted PR #1969 that hopefully clears the issue up.

[mmat11]

@dylandreimerink @ti-mo should we release a patch after #1969 is merged?

[ti-mo]

@mmat11 Yep, we'll release 0.21.1 when that PR goes in.