Validate code when scheduling upgrades from registrar

polkadot/runtime/common/src/paras_registrar/mod.rs

@@ -1032,6 +1032,51 @@ mod tests {
 		});
 	}
 
+	#[test]
+	fn schedule_code_upgrade_validates_code() {
+		new_test_ext().execute_with(|| {
+			const START_SESSION_INDEX: SessionIndex = 1;
+			run_to_session(START_SESSION_INDEX);
+
+			let para_id = LOWEST_PUBLIC_ID;
+			assert!(!Parachains::is_parathread(para_id));
+
+			let validation_code = test_validation_code(32);
+			assert_ok!(Registrar::reserve(RuntimeOrigin::signed(1)));
+			assert_eq!(Balances::reserved_balance(&1), <Test as Config>::ParaDeposit::get());
+			assert_ok!(Registrar::register(
+				RuntimeOrigin::signed(1),
+				para_id,
+				test_genesis_head(32),
+				validation_code.clone(),
+			));
+			conclude_pvf_checking::<Test>(&validation_code, VALIDATORS, START_SESSION_INDEX);
+
+			run_to_session(START_SESSION_INDEX + 2);
+			assert!(Parachains::is_parathread(para_id));
+
+			let new_code = test_validation_code(0);
+			assert_noop!(
+				Registrar::schedule_code_upgrade(
+					RuntimeOrigin::signed(1),
+					para_id,
+					new_code.clone(),
+				),
+				paras::Error::<Test>::EmptyCode
+			);
+
+			let new_code = test_validation_code(max_code_size() as usize + 1);
+			assert_noop!(
+				Registrar::schedule_code_upgrade(
+					RuntimeOrigin::signed(1),
+					para_id,
+					new_code.clone(),
+				),
+				paras::Error::<Test>::CodeTooLarge
+			);
+		});
+	}
+
 	#[test]
 	fn register_handles_basic_errors() {
 		new_test_ext().execute_with(|| {

polkadot/runtime/parachains/src/paras/mod.rs

@@ -679,6 +679,10 @@ pub mod pallet {
 		PvfCheckSubjectInvalid,
 		/// Parachain cannot currently schedule a code upgrade.
 		CannotUpgradeCode,
+		/// Invalid validation code size.
+		CodeTooLarge,
+		/// Validation code cannot be empty.
+		EmptyCode,
 	}
 
 	/// All currently active PVF pre-checking votes.
@@ -1230,6 +1234,10 @@ impl<T: Config> Pallet<T> {
 		// Check that we can schedule an upgrade at all.
 		ensure!(Self::can_upgrade_validation_code(id), Error::<T>::CannotUpgradeCode);
 		let config = configuration::Pallet::<T>::config();
+		// Validation code sanity checks:
+		ensure!(new_code.0.len() > 0, Error::<T>::EmptyCode);
+		ensure!(new_code.0.len() <= config.max_code_size as usize, Error::<T>::CodeTooLarge);
+
 		let current_block = frame_system::Pallet::<T>::block_number();
 		// Schedule the upgrade with a delay just like if a parachain triggered the upgrade.
 		let upgrade_block = current_block.saturating_add(config.validation_upgrade_delay);

prdoc/pr_3232.prdoc

@@ -0,0 +1,13 @@
+# Schema: Polkadot SDK PRDoc Schema (prdoc) v1.0.0
+# See doc at https://raw.githubusercontent.com/paritytech/polkadot-sdk/master/prdoc/schema_user.json
+
+title: Validate code when scheduling uprades
+
+doc:
+  - audience: Runtime User
+    description: |
+      Adds checks to ensure that the validation code is valid before scheduling
+      a code upgrade.
+
+crates: 
+  - name: polkadot-runtime-parachains