sqlite: reject reentry into a running statement

SQLite forbids stepping, resetting, or finalizing a statement while that
statement's own user-defined function callback is on the stack. The
callback depth added in 5cef767 is tracked per database, so it cannot
tell reentry into the running statement apart from the common pattern of
querying a different statement from a callback.

Mark the statement being executed and reject step, reset, and finalize on
that statement with ERR_INVALID_STATE. Previously a reentrant
iterator.next() silently consumed rows from the iteration in progress,
and a recursive get() failed with a V8 stack overflow instead of
reporting the constraint. close() and [Symbol.dispose]() are covered too,
since finalizing mid-step frees the running virtual machine. Statements
other than the running one are unaffected.

Assisted-by: claude:opus-5

Author: TrevorBurnham

src/node_sqlite.cc

@@ -2661,12 +2661,17 @@ void StatementSync::Close(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   THROW_AND_RETURN_ON_BAD_STATE(
       env, stmt->IsFinalized(), "statement has been finalized");
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
   stmt->Close();
 }
 
 void StatementSync::Dispose(const FunctionCallbackInfo<Value>& args) {
   StatementSync* stmt;
   ASSIGN_OR_RETURN_UNWRAP(&stmt, args.This());
+  Environment* env = Environment::GetCurrent(args);
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
   stmt->Close();
 }
 
@@ -3111,7 +3116,10 @@ void StatementSync::All(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   THROW_AND_RETURN_ON_BAD_STATE(
       env, stmt->IsFinalized(), "statement has been finalized");
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
   Isolate* isolate = env->isolate();
+  auto stepping = stmt->MarkStepping();
   int r = stmt->ResetStatement();
   CHECK_ERROR_OR_THROW(isolate, stmt->db_.get(), r, SQLITE_OK, void());
 
@@ -3138,6 +3146,8 @@ void StatementSync::Iterate(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   THROW_AND_RETURN_ON_BAD_STATE(
       env, stmt->IsFinalized(), "statement has been finalized");
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
   int r = stmt->ResetStatement();
   CHECK_ERROR_OR_THROW(env->isolate(), stmt->db_.get(), r, SQLITE_OK, void());
 
@@ -3161,6 +3171,9 @@ void StatementSync::Get(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   THROW_AND_RETURN_ON_BAD_STATE(
       env, stmt->IsFinalized(), "statement has been finalized");
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
+  auto stepping = stmt->MarkStepping();
   int r = stmt->ResetStatement();
   CHECK_ERROR_OR_THROW(env->isolate(), stmt->db_.get(), r, SQLITE_OK, void());
 
@@ -3185,6 +3198,9 @@ void StatementSync::Run(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   THROW_AND_RETURN_ON_BAD_STATE(
       env, stmt->IsFinalized(), "statement has been finalized");
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
+  auto stepping = stmt->MarkStepping();
   int r = stmt->ResetStatement();
   CHECK_ERROR_OR_THROW(env->isolate(), stmt->db_.get(), r, SQLITE_OK, void());
 
@@ -3474,6 +3490,9 @@ void SQLTagStore::Run(const FunctionCallbackInfo<Value>& args) {
     return;
   }
 
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
+  auto stepping = stmt->MarkStepping();
   if (!ResetAndBindStatement(env, stmt.get(), args)) {
     return;
   }
@@ -3500,6 +3519,8 @@ void SQLTagStore::Iterate(const FunctionCallbackInfo<Value>& args) {
     return;
   }
 
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
   if (!ResetAndBindStatement(env, stmt.get(), args)) {
     return;
   }
@@ -3528,6 +3549,9 @@ void SQLTagStore::Get(const FunctionCallbackInfo<Value>& args) {
     return;
   }
 
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
+  auto stepping = stmt->MarkStepping();
   if (!ResetAndBindStatement(env, stmt.get(), args)) {
     return;
   }
@@ -3557,6 +3581,9 @@ void SQLTagStore::All(const FunctionCallbackInfo<Value>& args) {
     return;
   }
 
+  THROW_AND_RETURN_ON_BAD_STATE(
+      env, stmt->IsStepping(), "statement is currently being executed");
+  auto stepping = stmt->MarkStepping();
   if (!ResetAndBindStatement(env, stmt.get(), args)) {
     return;
   }
@@ -3769,6 +3796,9 @@ void StatementSyncIterator::Next(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   THROW_AND_RETURN_ON_BAD_STATE(
       env, iter->stmt_->IsFinalized(), "statement has been finalized");
+  THROW_AND_RETURN_ON_BAD_STATE(env,
+                                iter->stmt_->IsStepping(),
+                                "statement is currently being executed");
   Isolate* isolate = env->isolate();
 
   auto iter_template = getLazyIterTemplate(env);
@@ -3791,6 +3821,7 @@ void StatementSyncIterator::Next(const FunctionCallbackInfo<Value>& args) {
       iter->statement_reset_generation_ != iter->stmt_->reset_generation_,
       "iterator was invalidated");
 
+  auto stepping = iter->stmt_->MarkStepping();
   int r = sqlite3_step(iter->stmt_->statement_);
   if (r != SQLITE_ROW) {
     CHECK_ERROR_OR_THROW(
@@ -3846,6 +3877,9 @@ void StatementSyncIterator::Return(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   THROW_AND_RETURN_ON_BAD_STATE(
       env, iter->stmt_->IsFinalized(), "statement has been finalized");
+  THROW_AND_RETURN_ON_BAD_STATE(env,
+                                iter->stmt_->IsStepping(),
+                                "statement is currently being executed");
   Isolate* isolate = env->isolate();
 
   sqlite3_reset(iter->stmt_->statement_);

src/node_sqlite.h

@@ -291,6 +291,19 @@ class StatementSync : public BaseObject {
   bool GetCachedColumnNames(v8::LocalVector<v8::Name>* keys);
   void Finalize();
   bool IsFinalized();
+  bool IsStepping() const { return stepping_; }
+
+  // SQLite forbids stepping, resetting, or finalizing a statement while that
+  // same statement's user-defined function callback is on the stack. The
+  // callback depth tracked by DatabaseSync is per-database, so it cannot
+  // distinguish reentry into the running statement from the common pattern of
+  // querying a *different* statement from a callback. This flag marks the
+  // statement that is currently being stepped so that only the former is
+  // rejected.
+  inline auto MarkStepping() {
+    stepping_ = true;
+    return OnScopeLeave([this]() { stepping_ = false; });
+  }
 
   SET_MEMORY_INFO_NAME(StatementSync)
   SET_SELF_SIZE(StatementSync)
@@ -304,6 +317,7 @@ class StatementSync : public BaseObject {
   bool use_big_ints_;
   bool allow_bare_named_params_;
   bool allow_unknown_named_params_;
+  bool stepping_ = false;
   uint64_t reset_generation_ = 0;
   std::optional<std::map<std::string, std::string>> bare_named_params_;
   inline int ResetStatement();

test/parallel/test-sqlite-udf-statement-reentry.js

@@ -0,0 +1,210 @@
+'use strict';
+
+const { skipIfSQLiteMissing, mustCall } = require('../common');
+skipIfSQLiteMissing();
+const assert = require('node:assert');
+const { suite, test } = require('node:test');
+const { DatabaseSync } = require('node:sqlite');
+
+const reentryError = {
+  code: 'ERR_INVALID_STATE',
+  message: 'statement is currently being executed',
+};
+
+function newDbWithRows() {
+  const db = new DatabaseSync(':memory:');
+  db.exec(`
+    CREATE TABLE data (value INTEGER);
+    INSERT INTO data VALUES (1), (2), (3);
+  `);
+  return db;
+}
+
+suite('reentry into the running statement is rejected', () => {
+  for (const method of ['all', 'get', 'run']) {
+    test(`statement.${method}() from its own UDF`, () => {
+      const db = newDbWithRows();
+      let statement;
+      db.function('reenter', mustCall((value) => {
+        assert.throws(() => statement[method](), reentryError);
+        return value;
+      }));
+
+      statement = db.prepare('SELECT reenter(value) AS value FROM data LIMIT 1');
+      assert.deepStrictEqual(statement.get(), { __proto__: null, value: 1 });
+      assert.strictEqual(db.isOpen, true);
+    });
+  }
+
+  test('iterator next() from its own UDF', () => {
+    const db = newDbWithRows();
+    let iterator;
+    db.function('reenter', mustCall((value) => {
+      assert.throws(() => iterator.next(), reentryError);
+      return value;
+    }, 3));
+
+    iterator = db.prepare('SELECT reenter(value) AS value FROM data').iterate();
+    assert.deepStrictEqual([...iterator].map((row) => row.value), [1, 2, 3]);
+    assert.strictEqual(db.isOpen, true);
+  });
+
+  test('iterator return() from its own UDF', () => {
+    const db = newDbWithRows();
+    let iterator;
+    db.function('reenter', mustCall((value) => {
+      assert.throws(() => iterator.return(), reentryError);
+      return value;
+    }));
+
+    iterator = db.prepare('SELECT reenter(value) AS value FROM data').iterate();
+    assert.strictEqual(iterator.next().done, false);
+    iterator.return();
+    assert.strictEqual(db.isOpen, true);
+  });
+
+  test('recursive get() reports the reentry rather than overflowing the stack',
+       () => {
+         const db = new DatabaseSync(':memory:');
+         let statement;
+         db.function('reenter', mustCall(() => {
+           assert.throws(() => statement.get(), reentryError);
+           return 1;
+         }));
+
+         statement = db.prepare('SELECT reenter() AS value');
+         assert.deepStrictEqual(statement.get(), { __proto__: null, value: 1 });
+       });
+
+  test('statement.close() from its own UDF', () => {
+    const db = newDbWithRows();
+    let statement;
+    db.function('reenter', mustCall((value) => {
+      assert.throws(() => statement.close(), reentryError);
+      return value;
+    }));
+
+    statement = db.prepare('SELECT reenter(value) AS value FROM data LIMIT 1');
+    assert.deepStrictEqual(statement.get(), { __proto__: null, value: 1 });
+    statement.close();
+  });
+
+  test('statement[Symbol.dispose]() from its own UDF', () => {
+    const db = newDbWithRows();
+    let statement;
+    db.function('reenter', mustCall((value) => {
+      assert.throws(() => statement[Symbol.dispose](), reentryError);
+      return value;
+    }));
+
+    statement = db.prepare('SELECT reenter(value) AS value FROM data LIMIT 1');
+    assert.deepStrictEqual(statement.get(), { __proto__: null, value: 1 });
+    statement[Symbol.dispose]();
+  });
+
+  test('statement is usable again after the callback returns', () => {
+    const db = newDbWithRows();
+    let statement;
+    db.function('reenter', mustCall((value) => {
+      assert.throws(() => statement.all(), reentryError);
+      return value;
+    }, 2));
+
+    statement = db.prepare('SELECT reenter(value) AS value FROM data LIMIT 1');
+    assert.deepStrictEqual(statement.all(), [{ __proto__: null, value: 1 }]);
+    assert.deepStrictEqual(statement.all(), [{ __proto__: null, value: 1 }]);
+  });
+});
+
+suite('a different statement remains usable from a callback', () => {
+  test('the lookup pattern still works', () => {
+    const db = newDbWithRows();
+    db.exec('CREATE TABLE names (value INTEGER, name TEXT);' +
+            "INSERT INTO names VALUES (1, 'one'), (2, 'two'), (3, 'three');");
+    const lookup = db.prepare('SELECT name FROM names WHERE value = ?');
+
+    db.function('name_of', mustCall((value) => lookup.get(value).name, 3));
+
+    assert.deepStrictEqual(
+      db.prepare('SELECT name_of(value) AS name FROM data').all(),
+      [
+        { __proto__: null, name: 'one' },
+        { __proto__: null, name: 'two' },
+        { __proto__: null, name: 'three' },
+      ],
+    );
+  });
+
+  test('a nested iterator over a different statement still works', () => {
+    const db = newDbWithRows();
+    const inner = db.prepare('SELECT value FROM data');
+
+    db.function('sum_all', mustCall(() => {
+      let total = 0;
+      for (const row of inner.iterate()) {
+        total += row.value;
+      }
+      return total;
+    }));
+
+    assert.deepStrictEqual(
+      db.prepare('SELECT sum_all() AS total LIMIT 1').get(),
+      { __proto__: null, total: 6 },
+    );
+  });
+});
+
+suite('SQL tag store reentry is rejected', () => {
+  for (const method of ['all', 'get', 'run']) {
+    test(`tag store ${method} re-executing the same tag`, () => {
+      const db = newDbWithRows();
+      const sql = db.createTagStore(4);
+      db.function('reenter', mustCall((value) => {
+        assert.throws(
+          () => sql[method]`SELECT reenter(value) AS value FROM data LIMIT 1`,
+          reentryError,
+        );
+        return value;
+      }));
+
+      assert.deepStrictEqual(
+        sql.get`SELECT reenter(value) AS value FROM data LIMIT 1`,
+        { __proto__: null, value: 1 },
+      );
+      assert.strictEqual(db.isOpen, true);
+    });
+  }
+});
+
+suite('aggregate functions', () => {
+  test('reentry from an aggregate step is rejected', () => {
+    const db = newDbWithRows();
+    let statement;
+    db.aggregate('reenter_agg', {
+      start: 0,
+      step: mustCall((total, value) => {
+        assert.throws(() => statement.get(), reentryError);
+        return total + value;
+      }, 3),
+    });
+
+    statement = db.prepare('SELECT reenter_agg(value) AS total FROM data');
+    assert.deepStrictEqual(statement.get(), { __proto__: null, total: 6 });
+  });
+
+  test('reentry from an aggregate result is rejected', () => {
+    const db = newDbWithRows();
+    let statement;
+    db.aggregate('reenter_result', {
+      start: 0,
+      step: (total, value) => total + value,
+      result: mustCall((total) => {
+        assert.throws(() => statement.get(), reentryError);
+        return total;
+      }),
+    });
+
+    statement = db.prepare('SELECT reenter_result(value) AS total FROM data');
+    assert.deepStrictEqual(statement.get(), { __proto__: null, total: 6 });
+  });
+});