-
Notifications
You must be signed in to change notification settings - Fork 1.6k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Add a new lint for catching unbound lifetimes in return values
This lint is based on some unsoundness found in Libra during security audits. Some function signatures can look sound, but based on the concrete types that end up being used, lifetimes may be unbound instead of anchored to the references of the arguments or the fields of a struct. When combined with unsafe code, this can cause transmuted lifetimes to be not what was intended.
- Loading branch information
Showing
12 changed files
with
310 additions
and
25 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,182 @@ | ||
| use if_chain::if_chain; | ||
| use rustc::declare_lint_pass; | ||
| use rustc::hir::intravisit::*; | ||
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; | ||
| use rustc_hir::*; | ||
| use rustc_session::declare_tool_lint; | ||
|
|
||
| use crate::utils::span_lint; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// **What it does:** Checks for lifetime annotations on return values | ||
| /// which might not always get bound. | ||
| /// | ||
| /// **Why is this bad?** If the function contains unsafe code which | ||
| /// transmutes to the lifetime, the resulting lifetime may live longer | ||
| /// than was intended. | ||
| /// | ||
| /// **Known problems*: None. | ||
| /// | ||
| /// **Example:** | ||
| /// ```rust | ||
| /// struct WrappedStr(str); | ||
| /// | ||
| /// // Bad: unbound return lifetime causing unsoundness (e.g. when x is String) | ||
| /// fn unbound<'a>(x: impl AsRef<str> + 'a) -> &'a WrappedStr { | ||
| /// let s = x.as_ref(); | ||
| /// unsafe { &*(s as *const str as *const WrappedStr) } | ||
| /// } | ||
| /// | ||
| /// // Good: bound return lifetime is sound | ||
| /// fn bound<'a>(x: &'a str) -> &'a WrappedStr { | ||
| /// unsafe { &*(x as *const str as *const WrappedStr) } | ||
| /// } | ||
| /// ``` | ||
| pub UNBOUND_RETURN_LIFETIMES, | ||
| correctness, | ||
| "unbound lifetimes in function return values" | ||
| } | ||
|
|
||
| declare_lint_pass!(UnboundReturnLifetimes => [UNBOUND_RETURN_LIFETIMES]); | ||
|
|
||
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnboundReturnLifetimes { | ||
| fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'tcx>) { | ||
| if let ItemKind::Fn(ref sig, ref generics, _id) = item.kind { | ||
| check_fn_inner(cx, &sig.decl, generics, None); | ||
| } | ||
| } | ||
|
|
||
| fn check_impl_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx ImplItem<'tcx>) { | ||
| if let ImplItemKind::Method(ref sig, _) = item.kind { | ||
| let parent_generics = impl_generics(cx, item.hir_id); | ||
| check_fn_inner(cx, &sig.decl, &item.generics, parent_generics); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn check_fn_inner<'a, 'tcx>( | ||
| cx: &LateContext<'a, 'tcx>, | ||
| decl: &'tcx FnDecl<'tcx>, | ||
| generics: &'tcx Generics<'tcx>, | ||
| parent_data: Option<(&'tcx Generics<'tcx>, &'tcx Ty<'tcx>)>, | ||
| ) { | ||
| let output_type = if let FunctionRetTy::Return(ref output_type) = decl.output { | ||
| output_type | ||
| } else { | ||
| return; | ||
| }; | ||
|
|
||
| let lt = if let TyKind::Rptr(ref lt, _) = output_type.kind { | ||
| lt | ||
| } else { | ||
| return; | ||
| }; | ||
|
|
||
| if matches!(lt.name, LifetimeName::Param(_)) { | ||
| let target_lt = lt; | ||
|
|
||
| // check function generics | ||
| // the target lifetime parameter must appear on the left of some outlives relation | ||
| if lifetime_outlives_something(target_lt, generics) { | ||
| return; | ||
| } | ||
|
|
||
| // check parent generics | ||
| // the target lifetime parameter must appear on the left of some outlives relation | ||
| if let Some((ref parent_generics, _)) = parent_data { | ||
| if lifetime_outlives_something(target_lt, parent_generics) { | ||
| return; | ||
| } | ||
| } | ||
|
|
||
| // check type generics | ||
| // the target lifetime parameter must be included in the type | ||
| if let Some((_, ref parent_ty)) = parent_data { | ||
| if TypeVisitor::type_contains_lifetime(parent_ty, target_lt) { | ||
| return; | ||
| } | ||
| } | ||
|
|
||
| // check arguments the target lifetime parameter must be included as a | ||
| // lifetime of a reference, either directly or through the gneric | ||
| // parameters of the argument type. | ||
| for input in decl.inputs.iter() { | ||
| if TypeVisitor::type_contains_lifetime(input, target_lt) { | ||
| return; | ||
| } | ||
| } | ||
|
|
||
| span_lint( | ||
| cx, | ||
| UNBOUND_RETURN_LIFETIMES, | ||
| target_lt.span, | ||
| "lifetime is unconstrained", | ||
| ); | ||
| } | ||
| } | ||
|
|
||
| struct TypeVisitor<'tcx> { | ||
| found: bool, | ||
| target_lt: &'tcx Lifetime, | ||
| } | ||
|
|
||
| impl<'tcx> TypeVisitor<'tcx> { | ||
| fn type_contains_lifetime(ty: &Ty<'_>, target_lt: &'tcx Lifetime) -> bool { | ||
| let mut visitor = TypeVisitor { | ||
| found: false, | ||
| target_lt, | ||
| }; | ||
| walk_ty(&mut visitor, ty); | ||
| visitor.found | ||
| } | ||
| } | ||
|
|
||
| impl<'tcx> Visitor<'tcx> for TypeVisitor<'tcx> { | ||
| fn visit_lifetime(&mut self, lt: &'tcx Lifetime) { | ||
| if lt.name == self.target_lt.name { | ||
| self.found = true; | ||
| } | ||
| } | ||
|
|
||
| fn visit_ty(&mut self, ty: &'tcx Ty<'_>) { | ||
| match ty.kind { | ||
| TyKind::Rptr(ref lt, _) => { | ||
| if lt.name == self.target_lt.name { | ||
| self.found = true; | ||
| } | ||
| }, | ||
| TyKind::Path(ref qpath) => { | ||
| if !self.found { | ||
| walk_qpath(self, qpath, ty.hir_id, ty.span); | ||
| } | ||
| }, | ||
| _ => (), | ||
| } | ||
| } | ||
|
|
||
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { | ||
| NestedVisitorMap::None | ||
| } | ||
| } | ||
|
|
||
| fn lifetime_outlives_something<'tcx>(target_lt: &'tcx Lifetime, generics: &'tcx Generics<'tcx>) -> bool { | ||
| if let Some(param) = generics.get_named(target_lt.name.ident().name) { | ||
| if param.bounds.iter().any(|b| matches!(b, GenericBound::Outlives(_))) { | ||
| return true; | ||
| } | ||
| } | ||
| false | ||
| } | ||
|
|
||
| fn impl_generics<'tcx>(cx: &LateContext<'_, 'tcx>, hir_id: HirId) -> Option<(&'tcx Generics<'tcx>, &'tcx Ty<'tcx>)> { | ||
| let parent_impl = cx.tcx.hir().get_parent_item(hir_id); | ||
| if_chain! { | ||
| if parent_impl != CRATE_HIR_ID; | ||
| if let Node::Item(item) = cx.tcx.hir().get(parent_impl); | ||
| if let ItemKind::Impl(_, _, _, ref parent_generics, _, ref ty, _) = item.kind; | ||
| then { | ||
| return Some((parent_generics, ty)) | ||
| } | ||
| } | ||
| None | ||
| } |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Oops, something went wrong.