From 3842ea671bfb98b2a7a42edbd31c5bac89078024 Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Wed, 11 Sep 2024 16:39:07 +0200 Subject: miri: fix overflow detection for unsigned pointer offset --- compiler/rustc_const_eval/src/interpret/operator.rs | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'compiler/rustc_const_eval/src') diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs index e9ba12dbcc4..b390bb87789 100644 --- a/compiler/rustc_const_eval/src/interpret/operator.rs +++ b/compiler/rustc_const_eval/src/interpret/operator.rs @@ -303,8 +303,10 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { let pointee_layout = self.layout_of(pointee_ty)?; assert!(pointee_layout.abi.is_sized()); - // We cannot overflow i64 as a type's size must be <= isize::MAX. + // The size always fits in `i64` as it can be at most `isize::MAX`. let pointee_size = i64::try_from(pointee_layout.size.bytes()).unwrap(); + // This uses the same type as `right`, which can be `isize` or `usize`. + // `pointee_size` is guaranteed to fit into both types. let pointee_size = ImmTy::from_int(pointee_size, right.layout); // Multiply element size and element count. let (val, overflowed) = self @@ -316,6 +318,11 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { } let offset_bytes = val.to_target_isize(self)?; + if !right.layout.abi.is_signed() && offset_bytes < 0 { + // We were supposed to do an unsigned offset but the result is negative -- this + // can only mean that the cast wrapped around. + throw_ub!(PointerArithOverflow) + } let offset_ptr = self.ptr_offset_inbounds(ptr, offset_bytes)?; Ok(ImmTy::from_scalar(Scalar::from_maybe_pointer(offset_ptr, self), left.layout)) } -- cgit 1.4.1-3-g733a5