TOCTOU: File creation followed by setting permissions

What it does

Detect when a file is being created and then the same file path is used to set file permissions. This is a classic source of Time Of Check, Time Of Use bugs.

Advantage

The recommended code creates the file and sets its attributes in a single syscall, avoiding TOCTOU bugs.

Drawbacks

No response

Example

    // Create with default permissions
    fs::create_dir(&path)?;
    // Fix up permissions
    fs::set_permissions(&path, Permissions::from_mode(0o700))?;

Could be written using OpenOptions::mode() and DirBuilderExt::mode().

Comparison with existing lints

No response

Additional Context

This is one of the bugs found in uutils during Canonical's audit: https://corrode.dev/blog/bugs-rust-wont-catch/#set-permissions-at-creation-time-not-after