Lint on reference casting to bigger underlying allocation
This commit is contained in:
Urgau
parent
bdc15928c8
commit
915200fbe0
@ -319,6 +319,11 @@ lint_invalid_nan_comparisons_lt_le_gt_ge = incorrect NaN comparison, NaN is not
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lint_invalid_reference_casting_assign_to_ref = assigning to `&T` is undefined behavior, consider using an `UnsafeCell`
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.label = casting happend here
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lint_invalid_reference_casting_bigger_layout = casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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.label = casting happend here
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.alloc = backing allocation comes from here
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.layout = casting from `{$from_ty}` ({$from_size} bytes) to `{$to_ty}` ({$to_size} bytes)
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lint_invalid_reference_casting_borrow_as_mut = casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
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.label = casting happend here
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@ -716,7 +716,7 @@ pub enum InvalidFromUtf8Diag {
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// reference_casting.rs
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#[derive(LintDiagnostic)]
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pub enum InvalidReferenceCastingDiag {
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pub enum InvalidReferenceCastingDiag<'tcx> {
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#[diag(lint_invalid_reference_casting_borrow_as_mut)]
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#[note(lint_invalid_reference_casting_note_book)]
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BorrowAsMut {
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@ -733,6 +733,18 @@ pub enum InvalidReferenceCastingDiag {
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#[note(lint_invalid_reference_casting_note_ty_has_interior_mutability)]
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ty_has_interior_mutability: Option<()>,
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},
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#[diag(lint_invalid_reference_casting_bigger_layout)]
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#[note(lint_layout)]
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BiggerLayout {
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#[label]
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orig_cast: Option<Span>,
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#[label(lint_alloc)]
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alloc: Span,
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from_ty: Ty<'tcx>,
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from_size: u64,
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to_ty: Ty<'tcx>,
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to_size: u64,
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},
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}
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// hidden_unicode_codepoints.rs
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@ -1,6 +1,7 @@
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use rustc_ast::Mutability;
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use rustc_hir::{Expr, ExprKind, UnOp};
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use rustc_middle::ty::{self, TypeAndMut};
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use rustc_middle::ty::layout::LayoutOf as _;
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use rustc_middle::ty::{self, layout::TyAndLayout, TypeAndMut};
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use rustc_span::sym;
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use crate::{lints::InvalidReferenceCastingDiag, LateContext, LateLintPass, LintContext};
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@ -38,13 +39,12 @@
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impl<'tcx> LateLintPass<'tcx> for InvalidReferenceCasting {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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if let Some((e, pat)) = borrow_or_assign(cx, expr) {
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if matches!(pat, PatternKind::Borrow { mutbl: Mutability::Mut } | PatternKind::Assign) {
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let init = cx.expr_or_init(e);
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let init = cx.expr_or_init(e);
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let orig_cast = if init.span != e.span { Some(init.span) } else { None };
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let Some(ty_has_interior_mutability) = is_cast_from_ref_to_mut_ptr(cx, init) else {
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return;
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};
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let orig_cast = if init.span != e.span { Some(init.span) } else { None };
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if matches!(pat, PatternKind::Borrow { mutbl: Mutability::Mut } | PatternKind::Assign)
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&& let Some(ty_has_interior_mutability) = is_cast_from_ref_to_mut_ptr(cx, init)
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{
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let ty_has_interior_mutability = ty_has_interior_mutability.then_some(());
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cx.emit_span_lint(
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@ -63,6 +63,23 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) {
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},
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);
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}
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if let Some((from_ty_layout, to_ty_layout, e_alloc)) =
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is_cast_to_bigger_memory_layout(cx, init)
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{
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cx.emit_span_lint(
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INVALID_REFERENCE_CASTING,
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expr.span,
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InvalidReferenceCastingDiag::BiggerLayout {
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orig_cast,
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alloc: e_alloc.span,
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from_ty: from_ty_layout.ty,
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from_size: from_ty_layout.layout.size().bytes(),
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to_ty: to_ty_layout.ty,
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to_size: to_ty_layout.layout.size().bytes(),
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},
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);
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}
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}
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}
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}
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@ -151,6 +168,48 @@ fn is_cast_from_ref_to_mut_ptr<'tcx>(
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}
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}
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fn is_cast_to_bigger_memory_layout<'tcx>(
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cx: &LateContext<'tcx>,
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orig_expr: &'tcx Expr<'tcx>,
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) -> Option<(TyAndLayout<'tcx>, TyAndLayout<'tcx>, Expr<'tcx>)> {
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let end_ty = cx.typeck_results().node_type(orig_expr.hir_id);
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let ty::RawPtr(TypeAndMut { ty: inner_end_ty, mutbl: _ }) = end_ty.kind() else {
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return None;
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};
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let (e, _) = peel_casts(cx, orig_expr);
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let start_ty = cx.typeck_results().node_type(e.hir_id);
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let ty::Ref(_, inner_start_ty, _) = start_ty.kind() else {
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return None;
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};
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// try to find the underlying allocation
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let e_alloc = cx.expr_or_init(e);
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let e_alloc =
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if let ExprKind::AddrOf(_, _, inner_expr) = e_alloc.kind { inner_expr } else { e_alloc };
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let alloc_ty = cx.typeck_results().node_type(e_alloc.hir_id);
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// if we do not find it we bail out, as this may not be UB
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// see https://github.com/rust-lang/unsafe-code-guidelines/issues/256
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if alloc_ty.is_any_ptr() {
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return None;
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}
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let from_layout = cx.layout_of(*inner_start_ty).ok()?;
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let alloc_layout = cx.layout_of(alloc_ty).ok()?;
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let to_layout = cx.layout_of(*inner_end_ty).ok()?;
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if to_layout.layout.size() > from_layout.layout.size()
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&& to_layout.layout.size() > alloc_layout.layout.size()
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{
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Some((from_layout, to_layout, *e_alloc))
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} else {
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None
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}
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}
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fn peel_casts<'tcx>(cx: &LateContext<'tcx>, mut e: &'tcx Expr<'tcx>) -> (&'tcx Expr<'tcx>, bool) {
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let mut gone_trough_unsafe_cell_raw_get = false;
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@ -81,14 +81,14 @@ fn main()
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assert_eq!(u as *const u16, p as *const u16);
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// ptr-ptr-cast (Length vtables)
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let mut l : [u8; 2] = [0,1];
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let w: *mut [u16; 2] = &mut l as *mut [u8; 2] as *mut _;
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let w: *mut [u16] = unsafe {&mut *w};
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let w_u8 : *const [u8] = w as *const [u8];
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assert_eq!(unsafe{&*w_u8}, &l);
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let mut l : [u16; 2] = [0,1];
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let w: *mut [u8; 2] = &mut l as *mut [u16; 2] as *mut _;
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let w: *mut [u8] = unsafe {&mut *w};
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let w_u16 : *const [u16] = w as *const [u16];
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assert_eq!(unsafe{&*w_u16}, &l);
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let s: *mut str = w as *mut str;
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let l_via_str = unsafe{&*(s as *const [u8])};
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let l_via_str = unsafe{&*(s as *const [u16])};
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assert_eq!(&l, l_via_str);
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// ptr-ptr-cast (Length vtables, check length is preserved)
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@ -30,7 +30,7 @@ unsafe fn ref_to_mut() {
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//~^ ERROR casting `&T` to `&mut T` is undefined behavior
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let _num = &mut *(num as *const i32).cast::<i32>().cast_mut().cast_const().cast_mut();
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//~^ ERROR casting `&T` to `&mut T` is undefined behavior
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let _num = &mut *(std::ptr::from_ref(static_u8()) as *mut i32);
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let _num = &mut *(std::ptr::from_ref(static_u8()) as *mut i8);
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//~^ ERROR casting `&T` to `&mut T` is undefined behavior
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let _num = &mut *std::mem::transmute::<_, *mut i32>(num);
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//~^ ERROR casting `&T` to `&mut T` is undefined behavior
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@ -141,6 +141,109 @@ unsafe fn generic_assign_to_ref<T>(this: &T, a: T) {
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}
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}
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#[repr(align(16))]
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struct I64(i64);
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#[repr(C)]
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struct Mat3<T> {
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a: Vec3<T>,
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b: Vec3<T>,
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c: Vec3<T>,
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}
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#[repr(C)]
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struct Vec3<T>(T, T, T);
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unsafe fn bigger_layout() {
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{
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let num = &mut 3i32;
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let _num = &*(num as *const i32 as *const i64);
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//~^ ERROR casting references to a bigger memory layout
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let _num = &mut *(num as *mut i32 as *mut i64);
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//~^ ERROR casting references to a bigger memory layout
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let _num = &mut *(num as *mut i32 as *mut I64);
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//~^ ERROR casting references to a bigger memory layout
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std::ptr::write(num as *mut i32 as *mut i64, 2);
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//~^ ERROR casting references to a bigger memory layout
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let _num = &mut *(num as *mut i32);
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}
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{
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let num = &mut [0i32; 3];
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let _num = &mut *(num as *mut _ as *mut [i64; 2]);
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//~^ ERROR casting references to a bigger memory layout
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std::ptr::write_unaligned(num as *mut _ as *mut [i32; 4], [0, 0, 1, 1]);
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//~^ ERROR casting references to a bigger memory layout
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let _num = &mut *(num as *mut _ as *mut [u32; 3]);
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let _num = &mut *(num as *mut _ as *mut [u32; 2]);
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}
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{
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let num = &mut [0i32; 3] as &mut [i32];
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let _num = &mut *(num as *mut _ as *mut i128);
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//~^ ERROR casting references to a bigger memory layout
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let _num = &mut *(num as *mut _ as *mut [i64; 4]);
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//~^ ERROR casting references to a bigger memory layout
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let _num = &mut *(num as *mut _ as *mut [u32]);
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let _num = &mut *(num as *mut _ as *mut [i16]);
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}
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{
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let mat3 = Mat3 { a: Vec3(0i32, 0, 0), b: Vec3(0, 0, 0), c: Vec3(0, 0, 0) };
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let _num = &mut *(&mat3 as *const _ as *mut [[i64; 3]; 3]);
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//~^ ERROR casting `&T` to `&mut T`
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//~^^ ERROR casting references to a bigger memory layout
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let _num = &*(&mat3 as *const _ as *mut [[i64; 3]; 3]);
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//~^ ERROR casting references to a bigger memory layout
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let _num = &*(&mat3 as *const _ as *mut [[i32; 3]; 3]);
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}
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{
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let mut l: [u8; 2] = [0,1];
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let w: *mut [u16; 2] = &mut l as *mut [u8; 2] as *mut _;
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let w: *mut [u16] = unsafe {&mut *w};
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//~^ ERROR casting references to a bigger memory layout
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}
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{
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fn foo() -> [i32; 1] { todo!() }
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let num = foo();
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let _num = &*(&num as *const i32 as *const i64);
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//~^ ERROR casting references to a bigger memory layout
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let _num = &*(&foo() as *const i32 as *const i64);
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//~^ ERROR casting references to a bigger memory layout
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}
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{
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fn bar(_a: &[i32; 2]) -> &[i32; 1] { todo!() }
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let num = bar(&[0, 0]);
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let _num = &*(num as *const i32 as *const i64);
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let _num = &*(bar(&[0, 0]) as *const i32 as *const i64);
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}
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{
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fn foi<T>() -> T { todo!() }
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let num = foi::<i32>();
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let _num = &*(&num as *const i32 as *const i64);
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//~^ ERROR casting references to a bigger memory layout
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}
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unsafe fn from_ref(this: &i32) -> &i64 {
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&*(this as *const i32 as *const i64)
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}
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}
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const RAW_PTR: *mut u8 = 1 as *mut u8;
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unsafe fn no_warn() {
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let num = &3i32;
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@ -66,8 +66,8 @@ LL | let _num = &mut *(num as *const i32).cast::<i32>().cast_mut().cast_cons
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error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
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--> $DIR/reference_casting.rs:33:16
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LL | let _num = &mut *(std::ptr::from_ref(static_u8()) as *mut i32);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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LL | let _num = &mut *(std::ptr::from_ref(static_u8()) as *mut i8);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
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@ -373,5 +373,164 @@ LL | *(this as *const _ as *mut _) = a;
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= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
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error: aborting due to 42 previous errors
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:161:20
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LL | let num = &mut 3i32;
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| ---- backing allocation comes from here
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LL |
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LL | let _num = &*(num as *const i32 as *const i64);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: casting from `i32` (4 bytes) to `i64` (8 bytes)
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:163:20
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LL | let num = &mut 3i32;
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| ---- backing allocation comes from here
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...
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LL | let _num = &mut *(num as *mut i32 as *mut i64);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: casting from `i32` (4 bytes) to `i64` (8 bytes)
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:165:20
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LL | let num = &mut 3i32;
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| ---- backing allocation comes from here
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...
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LL | let _num = &mut *(num as *mut i32 as *mut I64);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: casting from `i32` (4 bytes) to `I64` (16 bytes)
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:167:9
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LL | let num = &mut 3i32;
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| ---- backing allocation comes from here
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...
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LL | std::ptr::write(num as *mut i32 as *mut i64, 2);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: casting from `i32` (4 bytes) to `i64` (8 bytes)
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:176:20
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LL | let num = &mut [0i32; 3];
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| --------- backing allocation comes from here
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LL |
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LL | let _num = &mut *(num as *mut _ as *mut [i64; 2]);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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|
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= note: casting from `[i32; 3]` (12 bytes) to `[i64; 2]` (16 bytes)
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:178:9
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LL | let num = &mut [0i32; 3];
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| --------- backing allocation comes from here
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...
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LL | std::ptr::write_unaligned(num as *mut _ as *mut [i32; 4], [0, 0, 1, 1]);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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|
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= note: casting from `[i32; 3]` (12 bytes) to `[i32; 4]` (16 bytes)
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:188:20
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LL | let num = &mut [0i32; 3] as &mut [i32];
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| --------- backing allocation comes from here
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LL |
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LL | let _num = &mut *(num as *mut _ as *mut i128);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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|
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= note: casting from `[i32; 3]` (12 bytes) to `i128` (16 bytes)
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:190:20
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LL | let num = &mut [0i32; 3] as &mut [i32];
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| --------- backing allocation comes from here
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...
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LL | let _num = &mut *(num as *mut _ as *mut [i64; 4]);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: casting from `[i32; 3]` (12 bytes) to `[i64; 4]` (32 bytes)
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error: casting `&T` to `&mut T` is undefined behavior, even if the reference is unused, consider instead using an `UnsafeCell`
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--> $DIR/reference_casting.rs:200:20
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LL | let _num = &mut *(&mat3 as *const _ as *mut [[i64; 3]; 3]);
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: for more information, visit <https://doc.rust-lang.org/book/ch15-05-interior-mutability.html>
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error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
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--> $DIR/reference_casting.rs:200:20
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LL | let _num = &mut *(&mat3 as *const _ as *mut [[i64; 3]; 3]);
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| ^^^^^^^^----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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| |
|
||||
| backing allocation comes from here
|
||||
|
|
||||
= note: casting from `Mat3<i32>` (36 bytes) to `[[i64; 3]; 3]` (72 bytes)
|
||||
|
||||
error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
|
||||
--> $DIR/reference_casting.rs:203:20
|
||||
|
|
||||
LL | let _num = &*(&mat3 as *const _ as *mut [[i64; 3]; 3]);
|
||||
| ^^^^----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
| |
|
||||
| backing allocation comes from here
|
||||
|
|
||||
= note: casting from `Mat3<i32>` (36 bytes) to `[[i64; 3]; 3]` (72 bytes)
|
||||
|
||||
error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
|
||||
--> $DIR/reference_casting.rs:212:37
|
||||
|
|
||||
LL | let w: *mut [u16; 2] = &mut l as *mut [u8; 2] as *mut _;
|
||||
| --------------------------------
|
||||
| | |
|
||||
| | backing allocation comes from here
|
||||
| casting happend here
|
||||
LL | let w: *mut [u16] = unsafe {&mut *w};
|
||||
| ^^^^^^^
|
||||
|
|
||||
= note: casting from `[u8; 2]` (2 bytes) to `[u16; 2]` (4 bytes)
|
||||
|
||||
error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
|
||||
--> $DIR/reference_casting.rs:220:20
|
||||
|
|
||||
LL | let _num = &*(&num as *const i32 as *const i64);
|
||||
| ^^^^---^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
| |
|
||||
| backing allocation comes from here
|
||||
|
|
||||
= note: casting from `[i32; 1]` (4 bytes) to `i64` (8 bytes)
|
||||
|
||||
error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
|
||||
--> $DIR/reference_casting.rs:222:20
|
||||
|
|
||||
LL | let _num = &*(&foo() as *const i32 as *const i64);
|
||||
| ^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
| |
|
||||
| backing allocation comes from here
|
||||
|
|
||||
= note: casting from `[i32; 1]` (4 bytes) to `i64` (8 bytes)
|
||||
|
||||
error: casting references to a bigger memory layout than the backing allocation is undefined behavior, even if the reference is unused
|
||||
--> $DIR/reference_casting.rs:238:20
|
||||
|
|
||||
LL | let _num = &*(&num as *const i32 as *const i64);
|
||||
| ^^^^---^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
||||
| |
|
||||
| backing allocation comes from here
|
||||
|
|
||||
= note: casting from `i32` (4 bytes) to `i64` (8 bytes)
|
||||
|
||||
error: aborting due to 57 previous errors
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user