rust-lang/rust
1
0
Fork 0
Code Issues Pull Requests Actions 2 Packages Projects Releases Wiki Activity

offset, offset_from: allow zero-byte offset on arbitrary pointers

Browse Source
This commit is contained in:
Ralf Jung
2024-05-09 12:35:11 +02:00
parent ba956ef4b0
commit 5c33a5690d
48 changed files with 200 additions and 475 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
compiler/rustc_const_eval/src/interpret/intrinsics.rs
View File

@@ -255,6 +255,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
name = intrinsic_name,
);
}
// This will always return 0.
(a, b)
}
(Err(_), _) | (_, Err(_)) => {

39
compiler/rustc_const_eval/src/interpret/memory.rs
View File

@@ -413,6 +413,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
/// to the allocation it points to. Supports both shared and mutable references, as the actual
/// checking is offloaded to a helper closure.
///
/// `alloc_size` will only get called for non-zero-sized accesses.
///
/// Returns `None` if and only if the size is 0.
fn check_and_deref_ptr<T>(
&self,
@@ -425,18 +427,19 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
M::ProvenanceExtra,
) -> InterpResult<'tcx, (Size, Align, T)>,
) -> InterpResult<'tcx, Option<T>> {
// Everything is okay with size 0.
if size.bytes() == 0 {
return Ok(None);
}
Ok(match self.ptr_try_get_alloc_id(ptr) {
Err(addr) => {
// We couldn't get a proper allocation. This is only okay if the access size is 0,
// and the address is not null.
if size.bytes() > 0 || addr == 0 {
throw_ub!(DanglingIntPointer(addr, msg));
}
None
// We couldn't get a proper allocation.
throw_ub!(DanglingIntPointer(addr, msg));
}
Ok((alloc_id, offset, prov)) => {
let (alloc_size, _alloc_align, ret_val) = alloc_size(alloc_id, offset, prov)?;
// Test bounds. This also ensures non-null.
// Test bounds.
// It is sufficient to check this for the end pointer. Also check for overflow!
if offset.checked_add(size, &self.tcx).map_or(true, |end| end > alloc_size) {
throw_ub!(PointerOutOfBounds {
@@ -447,14 +450,8 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
msg,
})
}
// Ensure we never consider the null pointer dereferenceable.
if M::Provenance::OFFSET_IS_ADDR {
assert_ne!(ptr.addr(), Size::ZERO);
}
// We can still be zero-sized in this branch, in which case we have to
// return `None`.
if size.bytes() == 0 { None } else { Some(ret_val) }
Some(ret_val)
}
})
}
@@ -641,16 +638,18 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
size,
CheckInAllocMsg::MemoryAccessTest,
|alloc_id, offset, prov| {
if !self.memory.validation_in_progress.get() {
// We want to call the hook on *all* accesses that involve an AllocId,
// including zero-sized accesses. That means we have to do it here
// rather than below in the `Some` branch.
M::before_alloc_read(self, alloc_id)?;
}
let alloc = self.get_alloc_raw(alloc_id)?;
Ok((alloc.size(), alloc.align, (alloc_id, offset, prov, alloc)))
},
)?;
// We want to call the hook on *all* accesses that involve an AllocId, including zero-sized
// accesses. That means we cannot rely on the closure above or the `Some` branch below. We
// do this after `check_and_deref_ptr` to ensure some basic sanity has already been checked.
if !self.memory.validation_in_progress.get() {
if let Ok((alloc_id, ..)) = self.ptr_try_get_alloc_id(ptr) {
M::before_alloc_read(self, alloc_id)?;
}
}
if let Some((alloc_id, offset, prov, alloc)) = ptr_and_alloc {
let range = alloc_range(offset, size);

11
compiler/rustc_const_eval/src/interpret/validity.rs
View File

@@ -434,6 +434,10 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
found_bytes: has.bytes()
},
);
// Make sure this is non-null. (ZST references can be dereferenceable and null.)
if self.ecx.scalar_may_be_null(Scalar::from_maybe_pointer(place.ptr(), self.ecx))? {
throw_validation_failure!(self.path, NullPtr { ptr_kind })
}
// Do not allow pointers to uninhabited types.
if place.layout.abi.is_uninhabited() {
let ty = place.layout.ty;
@@ -456,8 +460,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
// `!` is a ZST and we want to validate it.
if let Ok((alloc_id, _offset, _prov)) = self.ecx.ptr_try_get_alloc_id(place.ptr()) {
let mut skip_recursive_check = false;
let alloc_actual_mutbl = mutability(self.ecx, alloc_id);
if let GlobalAlloc::Static(did) = self.ecx.tcx.global_alloc(alloc_id) {
if let Some(GlobalAlloc::Static(did)) = self.ecx.tcx.try_get_global_alloc(alloc_id)
{
let DefKind::Static { nested, .. } = self.ecx.tcx.def_kind(did) else { bug!() };
// Special handling for pointers to statics (irrespective of their type).
assert!(!self.ecx.tcx.is_thread_local_static(did));
@@ -495,6 +499,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
// If this allocation has size zero, there is no actual mutability here.
let (size, _align, _alloc_kind) = self.ecx.get_alloc_info(alloc_id);
if size != Size::ZERO {
let alloc_actual_mutbl = mutability(self.ecx, alloc_id);
// Mutable pointer to immutable memory is no good.
if ptr_expected_mutbl == Mutability::Mut
&& alloc_actual_mutbl == Mutability::Not
@@ -831,6 +836,8 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValueVisitor<'mir, 'tcx, M>
trace!("visit_value: {:?}, {:?}", *op, op.layout);
// Check primitive types -- the leaves of our recursive descent.
// We assume that the Scalar validity range does not restrict these values
// any further than `try_visit_primitive` does!
if self.try_visit_primitive(op)? {
return Ok(());
}