interpret: make isize::MAX the limit for dynamic value sizes

Author: RalfJung

compiler/rustc_const_eval/src/interpret/eval_context.rs

@@ -23,8 +23,8 @@ use rustc_target::abi::{call::FnAbi, Align, HasDataLayout, Size, TargetDataLayou
 
 use super::{
     AllocCheck, AllocId, GlobalId, Immediate, InterpErrorInfo, InterpResult, MPlaceTy, Machine,
-    MemPlace, MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, Pointer, Provenance,
-    Scalar, ScalarMaybeUninit, StackPopJump,
+    MemPlace, MemPlaceMeta, Memory, MemoryKind, Operand, Place, PlaceTy, Pointer,
+    PointerArithmetic, Provenance, Scalar, ScalarMaybeUninit, StackPopJump,
 };
 use crate::transform::validate::equal_up_to_regions;
 
@@ -678,7 +678,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let size = size.align_to(align);
 
                 // Check if this brought us over the size limit.
-                if size.bytes() >= self.tcx.data_layout.obj_size_bound() {
+                if size > self.max_size_of_val() {
                     throw_ub!(InvalidMeta("total size is bigger than largest supported object"));
                 }
                 Ok(Some((size, align)))
@@ -694,9 +694,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 let elem = layout.field(self, 0);
 
                 // Make sure the slice is not too big.
-                let size = elem.size.checked_mul(len, self).ok_or_else(|| {
-                    err_ub!(InvalidMeta("slice is bigger than largest supported object"))
-                })?;
+                let size = elem.size * len;
+                if size > self.max_size_of_val() {
+                    throw_ub!(InvalidMeta("slice is bigger than largest supported object"));
+                }
                 Ok(Some((size, elem.align.abi)))
             }
 

compiler/rustc_const_eval/src/interpret/traits.rs

@@ -110,16 +110,17 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
             .read_ptr_sized(pointer_size * u64::try_from(COMMON_VTABLE_ENTRIES_SIZE).unwrap())?
             .check_init()?;
         let size = size.to_machine_usize(self)?;
+        let size = Size::from_bytes(size);
         let align = vtable
             .read_ptr_sized(pointer_size * u64::try_from(COMMON_VTABLE_ENTRIES_ALIGN).unwrap())?
             .check_init()?;
         let align = align.to_machine_usize(self)?;
         let align = Align::from_bytes(align).map_err(|e| err_ub!(InvalidVtableAlignment(e)))?;
 
-        if size >= self.tcx.data_layout.obj_size_bound() {
+        if size > self.max_size_of_val() {
             throw_ub!(InvalidVtableSize);
         }
-        Ok((Size::from_bytes(size), align))
+        Ok((size, align))
     }
 
     pub fn read_new_vtable_after_trait_upcasting_from_vtable(

compiler/rustc_middle/src/mir/interpret/pointer.rs

@@ -18,6 +18,11 @@ pub trait PointerArithmetic: HasDataLayout {
         self.data_layout().pointer_size
     }
 
+    #[inline(always)]
+    fn max_size_of_val(&self) -> Size {
+        Size::from_bytes(self.machine_isize_max())
+    }
+
     #[inline]
     fn machine_usize_max(&self) -> u64 {
         self.pointer_size().unsigned_int_max().try_into().unwrap()