Fix unoccupied bitfields

runtime/parachains/src/inclusion.rs

@@ -263,6 +263,14 @@ impl<T: Config> Pallet<T> {
 		// 3. each bitfield has exactly `expected_bits`
 		// 4. signature is valid.
 		let signed_bitfields = {
+			let occupied_bitmask: BitVec<BitOrderLsb0, u8> = assigned_paras_record
+				.iter()
+				.map(|p| {
+					p.as_ref()
+						.map_or(false, |(_id, pending_availability)| pending_availability.is_some())
+				})
+				.collect();
+
 			let mut last_index = None;
 
 			let signing_context = SigningContext {
@@ -289,6 +297,13 @@ impl<T: Config> Pallet<T> {
 					Error::<T>::ValidatorIndexOutOfBounds,
 				);
 
+				// If there is a bit set that shouldn't bet set, we ignore it.
+				if occupied_bitmask.clone() & unchecked_bitfield.unchecked_payload().0.clone() !=
+					unchecked_bitfield.unchecked_payload().0
+				{
+					continue
+				}
+
 				let validator_public =
 					&validators[unchecked_bitfield.unchecked_validator_index().0 as usize];
 
@@ -329,7 +344,7 @@ impl<T: Config> Pallet<T> {
 					}) {
 					*bit = true;
 				} else if cfg!(debug_assertions) {
-					ensure!(false, Error::<T>::InternalError);
+					return Err(Error::<T>::InternalError.into())
 				}
 			}
 
@@ -1412,13 +1427,14 @@ mod tests {
 					bare_bitfield,
 					&signing_context,
 				));
-
-				assert!(ParaInclusion::process_bitfields(
-					expected_bits(),
-					vec![signed.into()],
-					&core_lookup,
-				)
-				.is_err());
+				assert_eq!(
+					ParaInclusion::process_bitfields(
+						expected_bits(),
+						vec![signed.into()],
+						&core_lookup,
+					),
+					Ok(vec![])
+				);
 			}
 
 			// empty bitfield signed: always OK, but kind of useless.