1 //! Check the validity invariant of a given value, and tell the user
2 //! where in the value it got violated.
3 //! In const context, this goes even further and tries to approximate const safety.
4 //! That's useful because it means other passes (e.g. promotion) can rely on `const`s
5 //! to be const-safe.
6
7 use std::convert::TryFrom;
8 use std::fmt::Write;
9 use std::num::NonZeroUsize;
10
11 use rustc_data_structures::fx::FxHashSet;
12 use rustc_hir as hir;
13 use rustc_middle::mir::interpret::InterpError;
14 use rustc_middle::ty;
15 use rustc_middle::ty::layout::{LayoutOf, TyAndLayout};
16 use rustc_span::symbol::{sym, Symbol};
17 use rustc_target::abi::{Abi, Scalar as ScalarAbi, Size, VariantIdx, Variants, WrappingRange};
18
19 use std::hash::Hash;
20
21 use super::{
22 alloc_range, CheckInAllocMsg, GlobalAlloc, InterpCx, InterpResult, MPlaceTy, Machine,
23 MemPlaceMeta, OpTy, ScalarMaybeUninit, ValueVisitor,
24 };
25
26 macro_rules! throw_validation_failure {
27 ($where:expr, { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )?) => {{
28 let mut msg = String::new();
29 msg.push_str("encountered ");
30 write!(&mut msg, $($what_fmt),+).unwrap();
31 $(
32 msg.push_str(", but expected ");
33 write!(&mut msg, $($expected_fmt),+).unwrap();
34 )?
35 let path = rustc_middle::ty::print::with_no_trimmed_paths(|| {
36 let where_ = &$where;
37 if !where_.is_empty() {
38 let mut path = String::new();
39 write_path(&mut path, where_);
40 Some(path)
41 } else {
42 None
43 }
44 });
45 throw_ub!(ValidationFailure { path, msg })
46 }};
47 }
48
49 /// If $e throws an error matching the pattern, throw a validation failure.
50 /// Other errors are passed back to the caller, unchanged -- and if they reach the root of
51 /// the visitor, we make sure only validation errors and `InvalidProgram` errors are left.
52 /// This lets you use the patterns as a kind of validation list, asserting which errors
53 /// can possibly happen:
54 ///
55 /// ```
56 /// let v = try_validation!(some_fn(), some_path, {
57 /// Foo | Bar | Baz => { "some failure" },
58 /// });
59 /// ```
60 ///
61 /// An additional expected parameter can also be added to the failure message:
62 ///
63 /// ```
64 /// let v = try_validation!(some_fn(), some_path, {
65 /// Foo | Bar | Baz => { "some failure" } expected { "something that wasn't a failure" },
66 /// });
67 /// ```
68 ///
69 /// An additional nicety is that both parameters actually take format args, so you can just write
70 /// the format string in directly:
71 ///
72 /// ```
73 /// let v = try_validation!(some_fn(), some_path, {
74 /// Foo | Bar | Baz => { "{:?}", some_failure } expected { "{}", expected_value },
75 /// });
76 /// ```
77 ///
78 macro_rules! try_validation {
79 ($e:expr, $where:expr,
80 $( $( $p:pat_param )|+ => { $( $what_fmt:expr ),+ } $( expected { $( $expected_fmt:expr ),+ } )? ),+ $(,)?
81 ) => {{
82 match $e {
83 Ok(x) => x,
84 // We catch the error and turn it into a validation failure. We are okay with
85 // allocation here as this can only slow down builds that fail anyway.
86 Err(e) => match e.kind() {
87 $(
88 $($p)|+ =>
89 throw_validation_failure!(
90 $where,
91 { $( $what_fmt ),+ } $( expected { $( $expected_fmt ),+ } )?
92 )
93 ),+,
94 #[allow(unreachable_patterns)]
95 _ => Err::<!, _>(e)?,
96 }
97 }
98 }};
99 }
100
101 /// We want to show a nice path to the invalid field for diagnostics,
102 /// but avoid string operations in the happy case where no error happens.
103 /// So we track a `Vec<PathElem>` where `PathElem` contains all the data we
104 /// need to later print something for the user.
105 #[derive(Copy, Clone, Debug)]
106 pub enum PathElem {
107 Field(Symbol),
108 Variant(Symbol),
109 GeneratorState(VariantIdx),
110 CapturedVar(Symbol),
111 ArrayElem(usize),
112 TupleElem(usize),
113 Deref,
114 EnumTag,
115 GeneratorTag,
116 DynDowncast,
117 }
118
119 /// Extra things to check for during validation of CTFE results.
120 pub enum CtfeValidationMode {
121 /// Regular validation, nothing special happening.
122 Regular,
123 /// Validation of a `const`.
124 /// `inner` says if this is an inner, indirect allocation (as opposed to the top-level const
125 /// allocation). Being an inner allocation makes a difference because the top-level allocation
126 /// of a `const` is copied for each use, but the inner allocations are implicitly shared.
127 /// `allow_static_ptrs` says if pointers to statics are permitted (which is the case for promoteds in statics).
128 Const { inner: bool, allow_static_ptrs: bool },
129 }
130
131 /// State for tracking recursive validation of references
132 pub struct RefTracking<T, PATH = ()> {
133 pub seen: FxHashSet<T>,
134 pub todo: Vec<(T, PATH)>,
135 }
136
137 impl<T: Copy + Eq + Hash + std::fmt::Debug, PATH: Default> RefTracking<T, PATH> {
empty() -> Self138 pub fn empty() -> Self {
139 RefTracking { seen: FxHashSet::default(), todo: vec![] }
140 }
new(op: T) -> Self141 pub fn new(op: T) -> Self {
142 let mut ref_tracking_for_consts =
143 RefTracking { seen: FxHashSet::default(), todo: vec![(op, PATH::default())] };
144 ref_tracking_for_consts.seen.insert(op);
145 ref_tracking_for_consts
146 }
147
track(&mut self, op: T, path: impl FnOnce() -> PATH)148 pub fn track(&mut self, op: T, path: impl FnOnce() -> PATH) {
149 if self.seen.insert(op) {
150 trace!("Recursing below ptr {:#?}", op);
151 let path = path();
152 // Remember to come back to this later.
153 self.todo.push((op, path));
154 }
155 }
156 }
157
158 /// Format a path
write_path(out: &mut String, path: &[PathElem])159 fn write_path(out: &mut String, path: &[PathElem]) {
160 use self::PathElem::*;
161
162 for elem in path.iter() {
163 match elem {
164 Field(name) => write!(out, ".{}", name),
165 EnumTag => write!(out, ".<enum-tag>"),
166 Variant(name) => write!(out, ".<enum-variant({})>", name),
167 GeneratorTag => write!(out, ".<generator-tag>"),
168 GeneratorState(idx) => write!(out, ".<generator-state({})>", idx.index()),
169 CapturedVar(name) => write!(out, ".<captured-var({})>", name),
170 TupleElem(idx) => write!(out, ".{}", idx),
171 ArrayElem(idx) => write!(out, "[{}]", idx),
172 // `.<deref>` does not match Rust syntax, but it is more readable for long paths -- and
173 // some of the other items here also are not Rust syntax. Actually we can't
174 // even use the usual syntax because we are just showing the projections,
175 // not the root.
176 Deref => write!(out, ".<deref>"),
177 DynDowncast => write!(out, ".<dyn-downcast>"),
178 }
179 .unwrap()
180 }
181 }
182
183 // Formats such that a sentence like "expected something {}" to mean
184 // "expected something <in the given range>" makes sense.
wrapping_range_format(r: WrappingRange, max_hi: u128) -> String185 fn wrapping_range_format(r: WrappingRange, max_hi: u128) -> String {
186 let WrappingRange { start: lo, end: hi } = r;
187 assert!(hi <= max_hi);
188 if lo > hi {
189 format!("less or equal to {}, or greater or equal to {}", hi, lo)
190 } else if lo == hi {
191 format!("equal to {}", lo)
192 } else if lo == 0 {
193 assert!(hi < max_hi, "should not be printing if the range covers everything");
194 format!("less or equal to {}", hi)
195 } else if hi == max_hi {
196 assert!(lo > 0, "should not be printing if the range covers everything");
197 format!("greater or equal to {}", lo)
198 } else {
199 format!("in the range {:?}", r)
200 }
201 }
202
203 struct ValidityVisitor<'rt, 'mir, 'tcx, M: Machine<'mir, 'tcx>> {
204 /// The `path` may be pushed to, but the part that is present when a function
205 /// starts must not be changed! `visit_fields` and `visit_array` rely on
206 /// this stack discipline.
207 path: Vec<PathElem>,
208 ref_tracking: Option<&'rt mut RefTracking<MPlaceTy<'tcx, M::PointerTag>, Vec<PathElem>>>,
209 /// `None` indicates this is not validating for CTFE (but for runtime).
210 ctfe_mode: Option<CtfeValidationMode>,
211 ecx: &'rt InterpCx<'mir, 'tcx, M>,
212 }
213
214 impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, 'tcx, M> {
aggregate_field_path_elem(&mut self, layout: TyAndLayout<'tcx>, field: usize) -> PathElem215 fn aggregate_field_path_elem(&mut self, layout: TyAndLayout<'tcx>, field: usize) -> PathElem {
216 // First, check if we are projecting to a variant.
217 match layout.variants {
218 Variants::Multiple { tag_field, .. } => {
219 if tag_field == field {
220 return match layout.ty.kind() {
221 ty::Adt(def, ..) if def.is_enum() => PathElem::EnumTag,
222 ty::Generator(..) => PathElem::GeneratorTag,
223 _ => bug!("non-variant type {:?}", layout.ty),
224 };
225 }
226 }
227 Variants::Single { .. } => {}
228 }
229
230 // Now we know we are projecting to a field, so figure out which one.
231 match layout.ty.kind() {
232 // generators and closures.
233 ty::Closure(def_id, _) | ty::Generator(def_id, _, _) => {
234 let mut name = None;
235 // FIXME this should be more descriptive i.e. CapturePlace instead of CapturedVar
236 // https://github.com/rust-lang/project-rfc-2229/issues/46
237 if let Some(local_def_id) = def_id.as_local() {
238 let tables = self.ecx.tcx.typeck(local_def_id);
239 if let Some(captured_place) =
240 tables.closure_min_captures_flattened(*def_id).nth(field)
241 {
242 // Sometimes the index is beyond the number of upvars (seen
243 // for a generator).
244 let var_hir_id = captured_place.get_root_variable();
245 let node = self.ecx.tcx.hir().get(var_hir_id);
246 if let hir::Node::Binding(pat) = node {
247 if let hir::PatKind::Binding(_, _, ident, _) = pat.kind {
248 name = Some(ident.name);
249 }
250 }
251 }
252 }
253
254 PathElem::CapturedVar(name.unwrap_or_else(|| {
255 // Fall back to showing the field index.
256 sym::integer(field)
257 }))
258 }
259
260 // tuples
261 ty::Tuple(_) => PathElem::TupleElem(field),
262
263 // enums
264 ty::Adt(def, ..) if def.is_enum() => {
265 // we might be projecting *to* a variant, or to a field *in* a variant.
266 match layout.variants {
267 Variants::Single { index } => {
268 // Inside a variant
269 PathElem::Field(def.variants[index].fields[field].ident.name)
270 }
271 Variants::Multiple { .. } => bug!("we handled variants above"),
272 }
273 }
274
275 // other ADTs
276 ty::Adt(def, _) => PathElem::Field(def.non_enum_variant().fields[field].ident.name),
277
278 // arrays/slices
279 ty::Array(..) | ty::Slice(..) => PathElem::ArrayElem(field),
280
281 // dyn traits
282 ty::Dynamic(..) => PathElem::DynDowncast,
283
284 // nothing else has an aggregate layout
285 _ => bug!("aggregate_field_path_elem: got non-aggregate type {:?}", layout.ty),
286 }
287 }
288
with_elem<R>( &mut self, elem: PathElem, f: impl FnOnce(&mut Self) -> InterpResult<'tcx, R>, ) -> InterpResult<'tcx, R>289 fn with_elem<R>(
290 &mut self,
291 elem: PathElem,
292 f: impl FnOnce(&mut Self) -> InterpResult<'tcx, R>,
293 ) -> InterpResult<'tcx, R> {
294 // Remember the old state
295 let path_len = self.path.len();
296 // Record new element
297 self.path.push(elem);
298 // Perform operation
299 let r = f(self)?;
300 // Undo changes
301 self.path.truncate(path_len);
302 // Done
303 Ok(r)
304 }
305
check_wide_ptr_meta( &mut self, meta: MemPlaceMeta<M::PointerTag>, pointee: TyAndLayout<'tcx>, ) -> InterpResult<'tcx>306 fn check_wide_ptr_meta(
307 &mut self,
308 meta: MemPlaceMeta<M::PointerTag>,
309 pointee: TyAndLayout<'tcx>,
310 ) -> InterpResult<'tcx> {
311 let tail = self.ecx.tcx.struct_tail_erasing_lifetimes(pointee.ty, self.ecx.param_env);
312 match tail.kind() {
313 ty::Dynamic(..) => {
314 let vtable = self.ecx.scalar_to_ptr(meta.unwrap_meta());
315 // Direct call to `check_ptr_access_align` checks alignment even on CTFE machines.
316 try_validation!(
317 self.ecx.memory.check_ptr_access_align(
318 vtable,
319 3 * self.ecx.tcx.data_layout.pointer_size, // drop, size, align
320 self.ecx.tcx.data_layout.pointer_align.abi,
321 CheckInAllocMsg::InboundsTest, // will anyway be replaced by validity message
322 ),
323 self.path,
324 err_ub!(DanglingIntPointer(..)) |
325 err_ub!(PointerUseAfterFree(..)) =>
326 { "dangling vtable pointer in wide pointer" },
327 err_ub!(AlignmentCheckFailed { .. }) =>
328 { "unaligned vtable pointer in wide pointer" },
329 err_ub!(PointerOutOfBounds { .. }) =>
330 { "too small vtable" },
331 );
332 try_validation!(
333 self.ecx.read_drop_type_from_vtable(vtable),
334 self.path,
335 err_ub!(DanglingIntPointer(..)) |
336 err_ub!(InvalidFunctionPointer(..)) =>
337 { "invalid drop function pointer in vtable (not pointing to a function)" },
338 err_ub!(InvalidVtableDropFn(..)) =>
339 { "invalid drop function pointer in vtable (function has incompatible signature)" },
340 );
341 try_validation!(
342 self.ecx.read_size_and_align_from_vtable(vtable),
343 self.path,
344 err_ub!(InvalidVtableSize) =>
345 { "invalid vtable: size is bigger than largest supported object" },
346 err_ub!(InvalidVtableAlignment(msg)) =>
347 { "invalid vtable: alignment {}", msg },
348 err_unsup!(ReadPointerAsBytes) => { "invalid size or align in vtable" },
349 );
350 // FIXME: More checks for the vtable.
351 }
352 ty::Slice(..) | ty::Str => {
353 let _len = try_validation!(
354 meta.unwrap_meta().to_machine_usize(self.ecx),
355 self.path,
356 err_unsup!(ReadPointerAsBytes) => { "non-integer slice length in wide pointer" },
357 );
358 // We do not check that `len * elem_size <= isize::MAX`:
359 // that is only required for references, and there it falls out of the
360 // "dereferenceable" check performed by Stacked Borrows.
361 }
362 ty::Foreign(..) => {
363 // Unsized, but not wide.
364 }
365 _ => bug!("Unexpected unsized type tail: {:?}", tail),
366 }
367
368 Ok(())
369 }
370
371 /// Check a reference or `Box`.
check_safe_pointer( &mut self, value: &OpTy<'tcx, M::PointerTag>, kind: &str, ) -> InterpResult<'tcx>372 fn check_safe_pointer(
373 &mut self,
374 value: &OpTy<'tcx, M::PointerTag>,
375 kind: &str,
376 ) -> InterpResult<'tcx> {
377 let value = try_validation!(
378 self.ecx.read_immediate(value),
379 self.path,
380 err_unsup!(ReadPointerAsBytes) => { "part of a pointer" } expected { "a proper pointer or integer value" },
381 );
382 // Handle wide pointers.
383 // Check metadata early, for better diagnostics
384 let place = try_validation!(
385 self.ecx.ref_to_mplace(&value),
386 self.path,
387 err_ub!(InvalidUninitBytes(None)) => { "uninitialized {}", kind },
388 );
389 if place.layout.is_unsized() {
390 self.check_wide_ptr_meta(place.meta, place.layout)?;
391 }
392 // Make sure this is dereferenceable and all.
393 let size_and_align = try_validation!(
394 self.ecx.size_and_align_of_mplace(&place),
395 self.path,
396 err_ub!(InvalidMeta(msg)) => { "invalid {} metadata: {}", kind, msg },
397 );
398 let (size, align) = size_and_align
399 // for the purpose of validity, consider foreign types to have
400 // alignment and size determined by the layout (size will be 0,
401 // alignment should take attributes into account).
402 .unwrap_or_else(|| (place.layout.size, place.layout.align.abi));
403 // Direct call to `check_ptr_access_align` checks alignment even on CTFE machines.
404 try_validation!(
405 self.ecx.memory.check_ptr_access_align(
406 place.ptr,
407 size,
408 align,
409 CheckInAllocMsg::InboundsTest, // will anyway be replaced by validity message
410 ),
411 self.path,
412 err_ub!(AlignmentCheckFailed { required, has }) =>
413 {
414 "an unaligned {} (required {} byte alignment but found {})",
415 kind,
416 required.bytes(),
417 has.bytes()
418 },
419 err_ub!(DanglingIntPointer(0, _)) =>
420 { "a null {}", kind },
421 err_ub!(DanglingIntPointer(i, _)) =>
422 { "a dangling {} (address 0x{:x} is unallocated)", kind, i },
423 err_ub!(PointerOutOfBounds { .. }) =>
424 { "a dangling {} (going beyond the bounds of its allocation)", kind },
425 // This cannot happen during const-eval (because interning already detects
426 // dangling pointers), but it can happen in Miri.
427 err_ub!(PointerUseAfterFree(..)) =>
428 { "a dangling {} (use-after-free)", kind },
429 );
430 // Recursive checking
431 if let Some(ref mut ref_tracking) = self.ref_tracking {
432 // Proceed recursively even for ZST, no reason to skip them!
433 // `!` is a ZST and we want to validate it.
434 // Skip validation entirely for some external statics
435 if let Ok((alloc_id, _offset, _ptr)) = self.ecx.memory.ptr_try_get_alloc(place.ptr) {
436 // not a ZST
437 let alloc_kind = self.ecx.tcx.get_global_alloc(alloc_id);
438 if let Some(GlobalAlloc::Static(did)) = alloc_kind {
439 assert!(!self.ecx.tcx.is_thread_local_static(did));
440 assert!(self.ecx.tcx.is_static(did));
441 if matches!(
442 self.ctfe_mode,
443 Some(CtfeValidationMode::Const { allow_static_ptrs: false, .. })
444 ) {
445 // See const_eval::machine::MemoryExtra::can_access_statics for why
446 // this check is so important.
447 // This check is reachable when the const just referenced the static,
448 // but never read it (so we never entered `before_access_global`).
449 throw_validation_failure!(self.path,
450 { "a {} pointing to a static variable", kind }
451 );
452 }
453 // We skip checking other statics. These statics must be sound by
454 // themselves, and the only way to get broken statics here is by using
455 // unsafe code.
456 // The reasons we don't check other statics is twofold. For one, in all
457 // sound cases, the static was already validated on its own, and second, we
458 // trigger cycle errors if we try to compute the value of the other static
459 // and that static refers back to us.
460 // We might miss const-invalid data,
461 // but things are still sound otherwise (in particular re: consts
462 // referring to statics).
463 return Ok(());
464 }
465 }
466 let path = &self.path;
467 ref_tracking.track(place, || {
468 // We need to clone the path anyway, make sure it gets created
469 // with enough space for the additional `Deref`.
470 let mut new_path = Vec::with_capacity(path.len() + 1);
471 new_path.clone_from(path);
472 new_path.push(PathElem::Deref);
473 new_path
474 });
475 }
476 Ok(())
477 }
478
read_scalar( &self, op: &OpTy<'tcx, M::PointerTag>, ) -> InterpResult<'tcx, ScalarMaybeUninit<M::PointerTag>>479 fn read_scalar(
480 &self,
481 op: &OpTy<'tcx, M::PointerTag>,
482 ) -> InterpResult<'tcx, ScalarMaybeUninit<M::PointerTag>> {
483 Ok(try_validation!(
484 self.ecx.read_scalar(op),
485 self.path,
486 err_unsup!(ReadPointerAsBytes) => { "(potentially part of) a pointer" } expected { "plain (non-pointer) bytes" },
487 ))
488 }
489
490 /// Check if this is a value of primitive type, and if yes check the validity of the value
491 /// at that type. Return `true` if the type is indeed primitive.
try_visit_primitive( &mut self, value: &OpTy<'tcx, M::PointerTag>, ) -> InterpResult<'tcx, bool>492 fn try_visit_primitive(
493 &mut self,
494 value: &OpTy<'tcx, M::PointerTag>,
495 ) -> InterpResult<'tcx, bool> {
496 // Go over all the primitive types
497 let ty = value.layout.ty;
498 match ty.kind() {
499 ty::Bool => {
500 let value = self.read_scalar(value)?;
501 try_validation!(
502 value.to_bool(),
503 self.path,
504 err_ub!(InvalidBool(..)) | err_ub!(InvalidUninitBytes(None)) =>
505 { "{}", value } expected { "a boolean" },
506 );
507 Ok(true)
508 }
509 ty::Char => {
510 let value = self.read_scalar(value)?;
511 try_validation!(
512 value.to_char(),
513 self.path,
514 err_ub!(InvalidChar(..)) | err_ub!(InvalidUninitBytes(None)) =>
515 { "{}", value } expected { "a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)" },
516 );
517 Ok(true)
518 }
519 ty::Float(_) | ty::Int(_) | ty::Uint(_) => {
520 let value = self.read_scalar(value)?;
521 // NOTE: Keep this in sync with the array optimization for int/float
522 // types below!
523 if M::enforce_number_validity(self.ecx) {
524 // Integers/floats in CTFE: Must be scalar bits, pointers are dangerous
525 let is_bits = value.check_init().map_or(false, |v| v.try_to_int().is_ok());
526 if !is_bits {
527 throw_validation_failure!(self.path,
528 { "{}", value } expected { "initialized plain (non-pointer) bytes" }
529 )
530 }
531 }
532 Ok(true)
533 }
534 ty::RawPtr(..) => {
535 // We are conservative with uninit for integers, but try to
536 // actually enforce the strict rules for raw pointers (mostly because
537 // that lets us re-use `ref_to_mplace`).
538 let place = try_validation!(
539 self.ecx.read_immediate(value).and_then(|ref i| self.ecx.ref_to_mplace(i)),
540 self.path,
541 err_ub!(InvalidUninitBytes(None)) => { "uninitialized raw pointer" },
542 err_unsup!(ReadPointerAsBytes) => { "part of a pointer" } expected { "a proper pointer or integer value" },
543 );
544 if place.layout.is_unsized() {
545 self.check_wide_ptr_meta(place.meta, place.layout)?;
546 }
547 Ok(true)
548 }
549 ty::Ref(_, ty, mutbl) => {
550 if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { .. }))
551 && *mutbl == hir::Mutability::Mut
552 {
553 // A mutable reference inside a const? That does not seem right (except if it is
554 // a ZST).
555 let layout = self.ecx.layout_of(ty)?;
556 if !layout.is_zst() {
557 throw_validation_failure!(self.path, { "mutable reference in a `const`" });
558 }
559 }
560 self.check_safe_pointer(value, "reference")?;
561 Ok(true)
562 }
563 ty::Adt(def, ..) if def.is_box() => {
564 self.check_safe_pointer(value, "box")?;
565 Ok(true)
566 }
567 ty::FnPtr(_sig) => {
568 let value = try_validation!(
569 self.ecx.read_immediate(value),
570 self.path,
571 err_unsup!(ReadPointerAsBytes) => { "part of a pointer" } expected { "a proper pointer or integer value" },
572 );
573 // Make sure we print a `ScalarMaybeUninit` (and not an `ImmTy`) in the error
574 // message below.
575 let value = value.to_scalar_or_uninit();
576 let _fn = try_validation!(
577 value.check_init().and_then(|ptr| self.ecx.memory.get_fn(self.ecx.scalar_to_ptr(ptr))),
578 self.path,
579 err_ub!(DanglingIntPointer(..)) |
580 err_ub!(InvalidFunctionPointer(..)) |
581 err_ub!(InvalidUninitBytes(None)) =>
582 { "{}", value } expected { "a function pointer" },
583 );
584 // FIXME: Check if the signature matches
585 Ok(true)
586 }
587 ty::Never => throw_validation_failure!(self.path, { "a value of the never type `!`" }),
588 ty::Foreign(..) | ty::FnDef(..) => {
589 // Nothing to check.
590 Ok(true)
591 }
592 // The above should be all the primitive types. The rest is compound, we
593 // check them by visiting their fields/variants.
594 ty::Adt(..)
595 | ty::Tuple(..)
596 | ty::Array(..)
597 | ty::Slice(..)
598 | ty::Str
599 | ty::Dynamic(..)
600 | ty::Closure(..)
601 | ty::Generator(..) => Ok(false),
602 // Some types only occur during typechecking, they have no layout.
603 // We should not see them here and we could not check them anyway.
604 ty::Error(_)
605 | ty::Infer(..)
606 | ty::Placeholder(..)
607 | ty::Bound(..)
608 | ty::Param(..)
609 | ty::Opaque(..)
610 | ty::Projection(..)
611 | ty::GeneratorWitness(..) => bug!("Encountered invalid type {:?}", ty),
612 }
613 }
614
visit_scalar( &mut self, op: &OpTy<'tcx, M::PointerTag>, scalar_layout: ScalarAbi, ) -> InterpResult<'tcx>615 fn visit_scalar(
616 &mut self,
617 op: &OpTy<'tcx, M::PointerTag>,
618 scalar_layout: ScalarAbi,
619 ) -> InterpResult<'tcx> {
620 if scalar_layout.valid_range.is_full_for(op.layout.size) {
621 // Nothing to check
622 return Ok(());
623 }
624 // At least one value is excluded.
625 let valid_range = scalar_layout.valid_range;
626 let WrappingRange { start, end } = valid_range;
627 let max_value = op.layout.size.unsigned_int_max();
628 assert!(end <= max_value);
629 // Determine the allowed range
630 let value = self.read_scalar(op)?;
631 let value = try_validation!(
632 value.check_init(),
633 self.path,
634 err_ub!(InvalidUninitBytes(None)) => { "{}", value }
635 expected { "something {}", wrapping_range_format(valid_range, max_value) },
636 );
637 let bits = match value.try_to_int() {
638 Err(_) => {
639 // So this is a pointer then, and casting to an int failed.
640 // Can only happen during CTFE.
641 let ptr = self.ecx.scalar_to_ptr(value);
642 if start == 1 && end == max_value {
643 // Only null is the niche. So make sure the ptr is NOT null.
644 if self.ecx.memory.ptr_may_be_null(ptr) {
645 throw_validation_failure!(self.path,
646 { "a potentially null pointer" }
647 expected {
648 "something that cannot possibly fail to be {}",
649 wrapping_range_format(valid_range, max_value)
650 }
651 )
652 }
653 return Ok(());
654 } else {
655 // Conservatively, we reject, because the pointer *could* have a bad
656 // value.
657 throw_validation_failure!(self.path,
658 { "a pointer" }
659 expected {
660 "something that cannot possibly fail to be {}",
661 wrapping_range_format(valid_range, max_value)
662 }
663 )
664 }
665 }
666 Ok(int) => int.assert_bits(op.layout.size),
667 };
668 // Now compare. This is slightly subtle because this is a special "wrap-around" range.
669 if valid_range.contains(bits) {
670 Ok(())
671 } else {
672 throw_validation_failure!(self.path,
673 { "{}", bits }
674 expected { "something {}", wrapping_range_format(valid_range, max_value) }
675 )
676 }
677 }
678 }
679
680 impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
681 for ValidityVisitor<'rt, 'mir, 'tcx, M>
682 {
683 type V = OpTy<'tcx, M::PointerTag>;
684
685 #[inline(always)]
ecx(&self) -> &InterpCx<'mir, 'tcx, M>686 fn ecx(&self) -> &InterpCx<'mir, 'tcx, M> {
687 &self.ecx
688 }
689
read_discriminant( &mut self, op: &OpTy<'tcx, M::PointerTag>, ) -> InterpResult<'tcx, VariantIdx>690 fn read_discriminant(
691 &mut self,
692 op: &OpTy<'tcx, M::PointerTag>,
693 ) -> InterpResult<'tcx, VariantIdx> {
694 self.with_elem(PathElem::EnumTag, move |this| {
695 Ok(try_validation!(
696 this.ecx.read_discriminant(op),
697 this.path,
698 err_ub!(InvalidTag(val)) =>
699 { "{}", val } expected { "a valid enum tag" },
700 err_ub!(InvalidUninitBytes(None)) =>
701 { "uninitialized bytes" } expected { "a valid enum tag" },
702 err_unsup!(ReadPointerAsBytes) =>
703 { "a pointer" } expected { "a valid enum tag" },
704 )
705 .1)
706 })
707 }
708
709 #[inline]
visit_field( &mut self, old_op: &OpTy<'tcx, M::PointerTag>, field: usize, new_op: &OpTy<'tcx, M::PointerTag>, ) -> InterpResult<'tcx>710 fn visit_field(
711 &mut self,
712 old_op: &OpTy<'tcx, M::PointerTag>,
713 field: usize,
714 new_op: &OpTy<'tcx, M::PointerTag>,
715 ) -> InterpResult<'tcx> {
716 let elem = self.aggregate_field_path_elem(old_op.layout, field);
717 self.with_elem(elem, move |this| this.visit_value(new_op))
718 }
719
720 #[inline]
visit_variant( &mut self, old_op: &OpTy<'tcx, M::PointerTag>, variant_id: VariantIdx, new_op: &OpTy<'tcx, M::PointerTag>, ) -> InterpResult<'tcx>721 fn visit_variant(
722 &mut self,
723 old_op: &OpTy<'tcx, M::PointerTag>,
724 variant_id: VariantIdx,
725 new_op: &OpTy<'tcx, M::PointerTag>,
726 ) -> InterpResult<'tcx> {
727 let name = match old_op.layout.ty.kind() {
728 ty::Adt(adt, _) => PathElem::Variant(adt.variants[variant_id].ident.name),
729 // Generators also have variants
730 ty::Generator(..) => PathElem::GeneratorState(variant_id),
731 _ => bug!("Unexpected type with variant: {:?}", old_op.layout.ty),
732 };
733 self.with_elem(name, move |this| this.visit_value(new_op))
734 }
735
736 #[inline(always)]
visit_union( &mut self, _op: &OpTy<'tcx, M::PointerTag>, _fields: NonZeroUsize, ) -> InterpResult<'tcx>737 fn visit_union(
738 &mut self,
739 _op: &OpTy<'tcx, M::PointerTag>,
740 _fields: NonZeroUsize,
741 ) -> InterpResult<'tcx> {
742 Ok(())
743 }
744
745 #[inline]
visit_value(&mut self, op: &OpTy<'tcx, M::PointerTag>) -> InterpResult<'tcx>746 fn visit_value(&mut self, op: &OpTy<'tcx, M::PointerTag>) -> InterpResult<'tcx> {
747 trace!("visit_value: {:?}, {:?}", *op, op.layout);
748
749 // Check primitive types -- the leafs of our recursive descend.
750 if self.try_visit_primitive(op)? {
751 return Ok(());
752 }
753 // Sanity check: `builtin_deref` does not know any pointers that are not primitive.
754 assert!(op.layout.ty.builtin_deref(true).is_none());
755
756 // Special check preventing `UnsafeCell` in the inner part of constants
757 if let Some(def) = op.layout.ty.ty_adt_def() {
758 if matches!(self.ctfe_mode, Some(CtfeValidationMode::Const { inner: true, .. }))
759 && Some(def.did) == self.ecx.tcx.lang_items().unsafe_cell_type()
760 {
761 throw_validation_failure!(self.path, { "`UnsafeCell` in a `const`" });
762 }
763 }
764
765 // Recursively walk the value at its type.
766 self.walk_value(op)?;
767
768 // *After* all of this, check the ABI. We need to check the ABI to handle
769 // types like `NonNull` where the `Scalar` info is more restrictive than what
770 // the fields say (`rustc_layout_scalar_valid_range_start`).
771 // But in most cases, this will just propagate what the fields say,
772 // and then we want the error to point at the field -- so, first recurse,
773 // then check ABI.
774 //
775 // FIXME: We could avoid some redundant checks here. For newtypes wrapping
776 // scalars, we do the same check on every "level" (e.g., first we check
777 // MyNewtype and then the scalar in there).
778 match op.layout.abi {
779 Abi::Uninhabited => {
780 throw_validation_failure!(self.path,
781 { "a value of uninhabited type {:?}", op.layout.ty }
782 );
783 }
784 Abi::Scalar(scalar_layout) => {
785 self.visit_scalar(op, scalar_layout)?;
786 }
787 Abi::ScalarPair { .. } | Abi::Vector { .. } => {
788 // These have fields that we already visited above, so we already checked
789 // all their scalar-level restrictions.
790 // There is also no equivalent to `rustc_layout_scalar_valid_range_start`
791 // that would make skipping them here an issue.
792 }
793 Abi::Aggregate { .. } => {
794 // Nothing to do.
795 }
796 }
797
798 Ok(())
799 }
800
visit_aggregate( &mut self, op: &OpTy<'tcx, M::PointerTag>, fields: impl Iterator<Item = InterpResult<'tcx, Self::V>>, ) -> InterpResult<'tcx>801 fn visit_aggregate(
802 &mut self,
803 op: &OpTy<'tcx, M::PointerTag>,
804 fields: impl Iterator<Item = InterpResult<'tcx, Self::V>>,
805 ) -> InterpResult<'tcx> {
806 match op.layout.ty.kind() {
807 ty::Str => {
808 let mplace = op.assert_mem_place(); // strings are never immediate
809 let len = mplace.len(self.ecx)?;
810 try_validation!(
811 self.ecx.memory.read_bytes(mplace.ptr, Size::from_bytes(len)),
812 self.path,
813 err_ub!(InvalidUninitBytes(..)) => { "uninitialized data in `str`" },
814 err_unsup!(ReadPointerAsBytes) => { "a pointer in `str`" },
815 );
816 }
817 ty::Array(tys, ..) | ty::Slice(tys)
818 // This optimization applies for types that can hold arbitrary bytes (such as
819 // integer and floating point types) or for structs or tuples with no fields.
820 // FIXME(wesleywiser) This logic could be extended further to arbitrary structs
821 // or tuples made up of integer/floating point types or inhabited ZSTs with no
822 // padding.
823 if matches!(tys.kind(), ty::Int(..) | ty::Uint(..) | ty::Float(..))
824 =>
825 {
826 // Optimized handling for arrays of integer/float type.
827
828 // Arrays cannot be immediate, slices are never immediate.
829 let mplace = op.assert_mem_place();
830 // This is the length of the array/slice.
831 let len = mplace.len(self.ecx)?;
832 // This is the element type size.
833 let layout = self.ecx.layout_of(tys)?;
834 // This is the size in bytes of the whole array. (This checks for overflow.)
835 let size = layout.size * len;
836
837 // Optimization: we just check the entire range at once.
838 // NOTE: Keep this in sync with the handling of integer and float
839 // types above, in `visit_primitive`.
840 // In run-time mode, we accept pointers in here. This is actually more
841 // permissive than a per-element check would be, e.g., we accept
842 // a &[u8] that contains a pointer even though bytewise checking would
843 // reject it. However, that's good: We don't inherently want
844 // to reject those pointers, we just do not have the machinery to
845 // talk about parts of a pointer.
846 // We also accept uninit, for consistency with the slow path.
847 let alloc = match self.ecx.memory.get(mplace.ptr, size, mplace.align)? {
848 Some(a) => a,
849 None => {
850 // Size 0, nothing more to check.
851 return Ok(());
852 }
853 };
854
855 let allow_uninit_and_ptr = !M::enforce_number_validity(self.ecx);
856 match alloc.check_bytes(
857 alloc_range(Size::ZERO, size),
858 allow_uninit_and_ptr,
859 ) {
860 // In the happy case, we needn't check anything else.
861 Ok(()) => {}
862 // Some error happened, try to provide a more detailed description.
863 Err(err) => {
864 // For some errors we might be able to provide extra information.
865 // (This custom logic does not fit the `try_validation!` macro.)
866 match err.kind() {
867 err_ub!(InvalidUninitBytes(Some((_alloc_id, access)))) => {
868 // Some byte was uninitialized, determine which
869 // element that byte belongs to so we can
870 // provide an index.
871 let i = usize::try_from(
872 access.uninit_offset.bytes() / layout.size.bytes(),
873 )
874 .unwrap();
875 self.path.push(PathElem::ArrayElem(i));
876
877 throw_validation_failure!(self.path, { "uninitialized bytes" })
878 }
879 err_unsup!(ReadPointerAsBytes) => {
880 throw_validation_failure!(self.path, { "a pointer" } expected { "plain (non-pointer) bytes" })
881 }
882
883 // Propagate upwards (that will also check for unexpected errors).
884 _ => return Err(err),
885 }
886 }
887 }
888 }
889 // Fast path for arrays and slices of ZSTs. We only need to check a single ZST element
890 // of an array and not all of them, because there's only a single value of a specific
891 // ZST type, so either validation fails for all elements or none.
892 ty::Array(tys, ..) | ty::Slice(tys) if self.ecx.layout_of(tys)?.is_zst() => {
893 // Validate just the first element (if any).
894 self.walk_aggregate(op, fields.take(1))?
895 }
896 _ => {
897 self.walk_aggregate(op, fields)? // default handler
898 }
899 }
900 Ok(())
901 }
902 }
903
904 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
validate_operand_internal( &self, op: &OpTy<'tcx, M::PointerTag>, path: Vec<PathElem>, ref_tracking: Option<&mut RefTracking<MPlaceTy<'tcx, M::PointerTag>, Vec<PathElem>>>, ctfe_mode: Option<CtfeValidationMode>, ) -> InterpResult<'tcx>905 fn validate_operand_internal(
906 &self,
907 op: &OpTy<'tcx, M::PointerTag>,
908 path: Vec<PathElem>,
909 ref_tracking: Option<&mut RefTracking<MPlaceTy<'tcx, M::PointerTag>, Vec<PathElem>>>,
910 ctfe_mode: Option<CtfeValidationMode>,
911 ) -> InterpResult<'tcx> {
912 trace!("validate_operand_internal: {:?}, {:?}", *op, op.layout.ty);
913
914 // Construct a visitor
915 let mut visitor = ValidityVisitor { path, ref_tracking, ctfe_mode, ecx: self };
916
917 // Run it.
918 match visitor.visit_value(&op) {
919 Ok(()) => Ok(()),
920 // Pass through validation failures.
921 Err(err) if matches!(err.kind(), err_ub!(ValidationFailure { .. })) => Err(err),
922 // Also pass through InvalidProgram, those just indicate that we could not
923 // validate and each caller will know best what to do with them.
924 Err(err) if matches!(err.kind(), InterpError::InvalidProgram(_)) => Err(err),
925 // Avoid other errors as those do not show *where* in the value the issue lies.
926 Err(err) => {
927 err.print_backtrace();
928 bug!("Unexpected error during validation: {}", err);
929 }
930 }
931 }
932
933 /// This function checks the data at `op` to be const-valid.
934 /// `op` is assumed to cover valid memory if it is an indirect operand.
935 /// It will error if the bits at the destination do not match the ones described by the layout.
936 ///
937 /// `ref_tracking` is used to record references that we encounter so that they
938 /// can be checked recursively by an outside driving loop.
939 ///
940 /// `constant` controls whether this must satisfy the rules for constants:
941 /// - no pointers to statics.
942 /// - no `UnsafeCell` or non-ZST `&mut`.
943 #[inline(always)]
const_validate_operand( &self, op: &OpTy<'tcx, M::PointerTag>, path: Vec<PathElem>, ref_tracking: &mut RefTracking<MPlaceTy<'tcx, M::PointerTag>, Vec<PathElem>>, ctfe_mode: CtfeValidationMode, ) -> InterpResult<'tcx>944 pub fn const_validate_operand(
945 &self,
946 op: &OpTy<'tcx, M::PointerTag>,
947 path: Vec<PathElem>,
948 ref_tracking: &mut RefTracking<MPlaceTy<'tcx, M::PointerTag>, Vec<PathElem>>,
949 ctfe_mode: CtfeValidationMode,
950 ) -> InterpResult<'tcx> {
951 self.validate_operand_internal(op, path, Some(ref_tracking), Some(ctfe_mode))
952 }
953
954 /// This function checks the data at `op` to be runtime-valid.
955 /// `op` is assumed to cover valid memory if it is an indirect operand.
956 /// It will error if the bits at the destination do not match the ones described by the layout.
957 #[inline(always)]
validate_operand(&self, op: &OpTy<'tcx, M::PointerTag>) -> InterpResult<'tcx>958 pub fn validate_operand(&self, op: &OpTy<'tcx, M::PointerTag>) -> InterpResult<'tcx> {
959 self.validate_operand_internal(op, vec![], None, None)
960 }
961 }
962