Use validate_region in get_region

Author: webmaster128

CHANGELOG.md

@@ -11,6 +11,9 @@
 **cosmwasm-vm**
 
 - Remove unused cache size argument from `CosmCache`.
+- Add checks to `get_region` for failing early when the contract sends a Region
+  pointer to the VM that is not backed by a plausible Region. This helps
+  development of standard libraries.
 
 ## 0.9.3 (2020-07-08)
 

packages/vm/src/memory.rs

@@ -137,7 +137,11 @@ fn get_region(ctx: &Ctx, ptr: u32) -> CommunicationResult<Region> {
     let memory = ctx.memory(0);
     let wptr = WasmPtr::<Region>::new(ptr);
     match wptr.deref(memory) {
-        Some(cell) => Ok(cell.get()),
+        Some(cell) => {
+            let region = cell.get();
+            validate_region(&region)?;
+            Ok(region)
+        }
         None => Err(CommunicationError::deref_err(
             ptr,
             "Could not dereference this pointer to a Region",