Fix bug #78192 PDO SQLite SegFault when reuse statement after schema has changed

Reset stmt->columns when column count changed on new execution of prepared statement

Author: vincent4vx

NEWS

@@ -2,6 +2,10 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? 2019, PHP 7.2.21
 
+- PDO_Sqlite:
+  . Fixed #78192 (SegFault when reuse statement after schema has changed).
+    (Vincent Quatrevieux)
+
 - XMLRPC:
   . Fixed #78173 (XML-RPC mutates immutable objects during encoding). (Asher
     Baker)

ext/pdo_sqlite/sqlite_statement.c

@@ -43,6 +43,46 @@ static int pdo_sqlite_stmt_dtor(pdo_stmt_t *stmt)
 	return 1;
 }
 
+/**
+ * Change the column count on the statement.
+ *
+ * Since PHP 7.2 sqlite3_prepare_v2 is used which auto recompile prepared statement on schema change.
+ * Instead of raise an error on schema change, the result set will change, and the statement's columns must be updated.
+ *
+ * See bug #78192
+ */
+static void pdo_sqlite_stmt_set_column_count(pdo_stmt_t *stmt, int new_count)
+{
+	/* Columns not yet "described" */
+	if (!stmt->columns) {
+		stmt->column_count = new_count;
+
+		return;
+	}
+
+	/*
+	 * The column count has not changed : no need to reload columns description 
+	 * Note: Do not handle attribute name change, without column count change
+	 */
+	if (new_count == stmt->column_count) {
+		return;
+	}
+
+	/* Free previous columns to force reload description */
+	int i;
+
+	for (i = 0; i < stmt->column_count; i++) {
+		if (stmt->columns[i].name) {
+			zend_string_release(stmt->columns[i].name);
+			stmt->columns[i].name = NULL;
+		}
+	}
+
+	efree(stmt->columns);
+	stmt->columns = NULL;
+	stmt->column_count = new_count;
+}
+
 static int pdo_sqlite_stmt_execute(pdo_stmt_t *stmt)
 {
 	pdo_sqlite_stmt *S = (pdo_sqlite_stmt*)stmt->driver_data;
@@ -55,11 +95,11 @@ static int pdo_sqlite_stmt_execute(pdo_stmt_t *stmt)
 	switch (sqlite3_step(S->stmt)) {
 		case SQLITE_ROW:
 			S->pre_fetched = 1;
-			stmt->column_count = sqlite3_data_count(S->stmt);
+			pdo_sqlite_stmt_set_column_count(stmt, sqlite3_data_count(S->stmt));
 			return 1;
 
 		case SQLITE_DONE:
-			stmt->column_count = sqlite3_column_count(S->stmt);
+			pdo_sqlite_stmt_set_column_count(stmt, sqlite3_column_count(S->stmt));
 			stmt->row_count = sqlite3_changes(S->H->db);
 			sqlite3_reset(S->stmt);
 			S->done = 1;

ext/pdo_sqlite/tests/bug78192.phpt

@@ -0,0 +1,46 @@
+--TEST--
+PDO SQLite Bug #78192 SegFault when reuse statement after schema change
+--SKIPIF--
+<?php
+if (!extension_loaded('pdo_sqlite')) print 'skip not loaded';
+?>
+--FILE--
+<?php
+$connection = new \PDO('sqlite::memory:');
+$connection->setAttribute(\PDO::ATTR_ERRMODE, \PDO::ERRMODE_EXCEPTION);
+$connection->query('CREATE TABLE user (id INTEGER PRIMARY KEY NOT NULL, name VARCHAR(255) NOT NULL)');
+
+$stmt = $connection->prepare('INSERT INTO user (id, name) VALUES(:id, :name)');
+$stmt->execute([
+    'id'   => 10,
+    'name' => 'test',
+]);
+
+$stmt = $connection->prepare('SELECT * FROM user WHERE id = :id');
+$stmt->execute(['id' => 10]);
+var_dump($stmt->fetchAll(\PDO::FETCH_ASSOC));
+
+$connection->query('ALTER TABLE user ADD new_col VARCHAR(255)');
+$stmt->execute(['id' => 10]);
+var_dump($stmt->fetchAll(\PDO::FETCH_ASSOC));
+--EXPECT--
+array(1) {
+  [0]=>
+  array(2) {
+    ["id"]=>
+    string(2) "10"
+    ["name"]=>
+    string(4) "test"
+  }
+}
+array(1) {
+  [0]=>
+  array(3) {
+    ["id"]=>
+    string(2) "10"
+    ["name"]=>
+    string(4) "test"
+    ["new_col"]=>
+    NULL
+  }
+}