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CTFE validation: catch ReadPointerAsBytes and better error #82061

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merged 1 commit into from
Feb 16, 2021
Merged

CTFE validation: catch ReadPointerAsBytes and better error #82061

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42 changes: 29 additions & 13 deletions compiler/rustc_mir/src/interpret/validity.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,7 +21,7 @@ use std::hash::Hash;

use super::{
CheckInAllocMsg, GlobalAlloc, InterpCx, InterpResult, MPlaceTy, Machine, MemPlaceMeta, OpTy,
ValueVisitor,
ScalarMaybeUninit, ValueVisitor,
};

macro_rules! throw_validation_failure {
Expand Down Expand Up @@ -378,7 +378,11 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
value: OpTy<'tcx, M::PointerTag>,
kind: &str,
) -> InterpResult<'tcx> {
let value = self.ecx.read_immediate(value)?;
let value = try_validation!(
self.ecx.read_immediate(value),
self.path,
err_unsup!(ReadPointerAsBytes) => { "part of a pointer" } expected { "a proper pointer or integer value" },
);
// Handle wide pointers.
// Check metadata early, for better diagnostics
let place = try_validation!(
Expand Down Expand Up @@ -485,6 +489,17 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
Ok(())
}

fn read_scalar(
&self,
op: OpTy<'tcx, M::PointerTag>,
) -> InterpResult<'tcx, ScalarMaybeUninit<M::PointerTag>> {
Ok(try_validation!(
self.ecx.read_scalar(op),
self.path,
err_unsup!(ReadPointerAsBytes) => { "(potentially part of) a pointer" } expected { "plain (non-pointer) bytes" },
))
}

/// Check if this is a value of primitive type, and if yes check the validity of the value
/// at that type. Return `true` if the type is indeed primitive.
fn try_visit_primitive(
Expand All @@ -495,7 +510,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
let ty = value.layout.ty;
match ty.kind() {
ty::Bool => {
let value = self.ecx.read_scalar(value)?;
let value = self.read_scalar(value)?;
try_validation!(
value.to_bool(),
self.path,
Expand All @@ -505,7 +520,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
Ok(true)
}
ty::Char => {
let value = self.ecx.read_scalar(value)?;
let value = self.read_scalar(value)?;
try_validation!(
value.to_char(),
self.path,
Expand All @@ -515,11 +530,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
Ok(true)
}
ty::Float(_) | ty::Int(_) | ty::Uint(_) => {
let value = try_validation!(
self.ecx.read_scalar(value),
self.path,
err_unsup!(ReadPointerAsBytes) => { "read of part of a pointer" },
);
let value = self.read_scalar(value)?;
// NOTE: Keep this in sync with the array optimization for int/float
// types below!
if self.ctfe_mode.is_some() {
Expand All @@ -541,9 +552,10 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
// actually enforce the strict rules for raw pointers (mostly because
// that lets us re-use `ref_to_mplace`).
let place = try_validation!(
self.ecx.ref_to_mplace(self.ecx.read_immediate(value)?),
self.ecx.read_immediate(value).and_then(|i| self.ecx.ref_to_mplace(i)),
self.path,
err_ub!(InvalidUninitBytes(None)) => { "uninitialized raw pointer" },
err_unsup!(ReadPointerAsBytes) => { "part of a pointer" } expected { "a proper pointer or integer value" },
);
if place.layout.is_unsized() {
self.check_wide_ptr_meta(place.meta, place.layout)?;
Expand All @@ -569,9 +581,13 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
Ok(true)
}
ty::FnPtr(_sig) => {
let value = self.ecx.read_scalar(value)?;
let value = try_validation!(
self.ecx.read_immediate(value),
self.path,
err_unsup!(ReadPointerAsBytes) => { "part of a pointer" } expected { "a proper pointer or integer value" },
);
let _fn = try_validation!(
value.check_init().and_then(|ptr| self.ecx.memory.get_fn(ptr)),
value.to_scalar().and_then(|ptr| self.ecx.memory.get_fn(ptr)),
self.path,
err_ub!(DanglingIntPointer(..)) |
err_ub!(InvalidFunctionPointer(..)) |
Expand Down Expand Up @@ -615,7 +631,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
op: OpTy<'tcx, M::PointerTag>,
scalar_layout: &Scalar,
) -> InterpResult<'tcx> {
let value = self.ecx.read_scalar(op)?;
let value = self.read_scalar(op)?;
let valid_range = &scalar_layout.valid_range;
let (lo, hi) = valid_range.clone().into_inner();
// Determine the allowed range
Expand Down
2 changes: 1 addition & 1 deletion src/test/ui/consts/issue-79690.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@ error[E0080]: it is undefined behavior to use this value
--> $DIR/issue-79690.rs:29:1
|
LL | const G: Fat = unsafe { Transmute { t: FOO }.u };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered read of part of a pointer at .1.<deref>.size.foo
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered (potentially part of) a pointer at .1.<deref>.size.foo, but expected plain (non-pointer) bytes
|
= note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.

Expand Down