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Auto merge of #114333 - RalfJung:dangling-ptr-offset, r=oli-obk

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Miri: fix error on dangling pointer inbounds offset

We used to claim that the pointer was "dereferenced", but that is just not true.

Can be reviewed commit-by-commit. The first commit is an unrelated rename that didn't seem worth splitting into its own PR.

r? `@oli-obk`
This commit is contained in:
bors
2023-08-02 09:12:32 +00:00
parent 5cbfee5455 8496292dda
commit 64ad036307
69 changed files with 214 additions and 207 deletions
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4
compiler/rustc_const_eval/src/interpret/intrinsics.rs
View File

@@ -144,7 +144,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
sym::min_align_of_val | sym::size_of_val => {
// Avoid `deref_operand` -- this is not a deref, the ptr does not have to be
// Avoid `deref_pointer` -- this is not a deref, the ptr does not have to be
// dereferenceable!
let place = self.ref_to_mplace(&self.read_immediate(&args[0])?)?;
let (size, align) = self
@@ -225,7 +225,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
self.write_scalar(val, dest)?;
}
sym::discriminant_value => {
let place = self.deref_operand(&args[0])?;
let place = self.deref_pointer(&args[0])?;
let variant = self.read_discriminant(&place)?;
let discr = self.discriminant_for_variant(place.layout, variant)?;
self.write_scalar(discr, dest)?;

23
compiler/rustc_const_eval/src/interpret/memory.rs
View File

@@ -317,7 +317,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
kind = "static_mem"
)
}
None => err_ub!(PointerUseAfterFree(alloc_id)),
None => err_ub!(PointerUseAfterFree(alloc_id, CheckInAllocMsg::MemoryAccessTest)),
}
.into());
};
@@ -380,7 +380,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
M::enforce_alignment(self),
CheckInAllocMsg::MemoryAccessTest,
|alloc_id, offset, prov| {
let (size, align) = self.get_live_alloc_size_and_align(alloc_id)?;
let (size, align) = self
.get_live_alloc_size_and_align(alloc_id, CheckInAllocMsg::MemoryAccessTest)?;
Ok((size, align, (alloc_id, offset, prov)))
},
)
@@ -404,7 +405,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
CheckAlignment::Error,
msg,
|alloc_id, _, _| {
let (size, align) = self.get_live_alloc_size_and_align(alloc_id)?;
let (size, align) = self.get_live_alloc_size_and_align(alloc_id, msg)?;
Ok((size, align, ()))
},
)?;
@@ -414,7 +415,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// Low-level helper function to check if a ptr is in-bounds and potentially return a reference
/// to the allocation it points to. Supports both shared and mutable references, as the actual
/// checking is offloaded to a helper closure. `align` defines whether and which alignment check
/// is done. Returns `None` for size 0, and otherwise `Some` of what `alloc_size` returned.
/// is done.
///
/// If this returns `None`, the size is 0; it can however return `Some` even for size 0.
fn check_and_deref_ptr<T>(
&self,
ptr: Pointer<Option<M::Provenance>>,
@@ -515,7 +518,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
Some(GlobalAlloc::Function(..)) => throw_ub!(DerefFunctionPointer(id)),
Some(GlobalAlloc::VTable(..)) => throw_ub!(DerefVTablePointer(id)),
None => throw_ub!(PointerUseAfterFree(id)),
None => throw_ub!(PointerUseAfterFree(id, CheckInAllocMsg::MemoryAccessTest)),
Some(GlobalAlloc::Static(def_id)) => {
assert!(self.tcx.is_static(def_id));
assert!(!self.tcx.is_thread_local_static(def_id));
@@ -761,11 +764,15 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
}
}
/// Obtain the size and alignment of a live allocation.
pub fn get_live_alloc_size_and_align(&self, id: AllocId) -> InterpResult<'tcx, (Size, Align)> {
/// Obtain the size and alignment of a *live* allocation.
fn get_live_alloc_size_and_align(
&self,
id: AllocId,
msg: CheckInAllocMsg,
) -> InterpResult<'tcx, (Size, Align)> {
let (size, align, kind) = self.get_alloc_info(id);
if matches!(kind, AllocKind::Dead) {
throw_ub!(PointerUseAfterFree(id))
throw_ub!(PointerUseAfterFree(id, msg))
}
Ok((size, align))
}

5
compiler/rustc_const_eval/src/interpret/place.rs
View File

@@ -419,7 +419,7 @@ where
///
/// Only call this if you are sure the place is "valid" (aligned and inbounds), or do not
/// want to ever use the place for memory access!
/// Generally prefer `deref_operand`.
/// Generally prefer `deref_pointer`.
pub fn ref_to_mplace(
&self,
val: &ImmTy<'tcx, M::Provenance>,
@@ -439,8 +439,9 @@ where
}
/// Take an operand, representing a pointer, and dereference it to a place.
/// Corresponds to the `*` operator in Rust.
#[instrument(skip(self), level = "debug")]
pub fn deref_operand(
pub fn deref_pointer(
&self,
src: &impl Readable<'tcx, M::Provenance>,
) -> InterpResult<'tcx, MPlaceTy<'tcx, M::Provenance>> {

2
compiler/rustc_const_eval/src/interpret/projection.rs
View File

@@ -290,7 +290,7 @@ where
OpaqueCast(ty) => base.transmute(self.layout_of(ty)?, self)?,
Field(field, _) => self.project_field(base, field.index())?,
Downcast(_, variant) => self.project_downcast(base, variant)?,
Deref => self.deref_operand(&base.to_op(self)?)?.into(),
Deref => self.deref_pointer(&base.to_op(self)?)?.into(),
Index(local) => {
let layout = self.layout_of(self.tcx.types.usize)?;
let n = self.local_to_op(self.frame(), local, Some(layout))?;

3
compiler/rustc_const_eval/src/interpret/step.rs
View File

@@ -224,8 +224,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
Len(place) => {
let src = self.eval_place(place)?;
let op = self.place_to_op(&src)?;
let len = op.len(self)?;
let len = src.len(self)?;
self.write_scalar(Scalar::from_target_usize(len, self), &dest)?;
}

2
compiler/rustc_const_eval/src/interpret/terminator.rs
View File

@@ -661,7 +661,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let receiver_place = loop {
match receiver.layout.ty.kind() {
ty::Ref(..) | ty::RawPtr(..) => {
// We do *not* use `deref_operand` here: we don't want to conceptually
// We do *not* use `deref_pointer` here: we don't want to conceptually
// create a place that must be dereferenceable, since the receiver might
// be a raw pointer and (for `*const dyn Trait`) we don't need to
// actually access memory to resolve this method.

4
compiler/rustc_const_eval/src/interpret/validity.rs
View File

@@ -345,6 +345,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
value: &OpTy<'tcx, M::Provenance>,
ptr_kind: PointerKind,
) -> InterpResult<'tcx> {
// Not using `deref_pointer` since we do the dereferenceable check ourselves below.
let place = self.ecx.ref_to_mplace(&self.read_immediate(value, ptr_kind.into())?)?;
// Handle wide pointers.
// Check metadata early, for better diagnostics
@@ -515,9 +516,6 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
Ok(true)
}
ty::RawPtr(..) => {
// We are conservative with uninit for integers, but try to
// actually enforce the strict rules for raw pointers (mostly because
// that lets us re-use `ref_to_mplace`).
let place =
self.ecx.ref_to_mplace(&self.read_immediate(value, ExpectedKind::RawPtr)?)?;
if place.layout.is_unsized() {