New lint: Unix permissions set to a non-octal value

[xTibor]

What it does

Checks if the following functions expecting Unix permission bits only called with octal literals:

• PermissionsExt::set_mode
• PermissionsExt::from_mode
• OpenOptionsExt::mode
• DirBuilderExt::mode

Categories

• Kind: clippy::correctness

Drawbacks

False positives maybe.

Example

let mut options = OpenOptions::new();
options.mode(440);

This example tries to set the file permissions to 440 (r,r,-) however it ends up as 0o670 (rw,rwx,-) due to the decimal/octal confusion, giving unintended write/execute permissions in the process.

Clippy should suggest rewriting that line as options.mode(0o440);.

[ebobrow]

@rustbot claim

[ebobrow]

@giraffate Can I get a little help on this one? I need to be able to check if the method mode, for example, is being called on an object of type OpenOptions. Currently, my lint would apply to any object calling any method with the name mode. Sorry, I wasn't sure who to tag here.

[giraffate]

@ebobrow Thanks for working on this!

I think these codes may help you to detect a receiver type of OpenOptions:

rust-clippy/clippy_lints/src/open_options.rs

Lines 32 to 43 in 0743e84

	impl<'tcx> LateLintPass<'tcx> for OpenOptions {
	fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
	if let ExprKind::MethodCall(ref path, _, ref arguments, _) = e.kind {
	let obj_ty = cx.typeck_results().expr_ty(&arguments[0]).peel_refs();
	if path.ident.name == sym!(open) && match_type(cx, obj_ty, &paths::OPEN_OPTIONS) {
	let mut options = Vec::new();
	get_open_options(cx, &arguments[0], &mut options);
	check_open_options(cx, &options, e.span);
	}
	}
	}
	}

[ebobrow]

Thank you so much!