Fix #81720: Uninitialized array in pg_query_params() leading to RCE

We must not free parameters which we haven't initialized yet.

We also fix the not directly related issue, that we checked for the
wrong value being `NULL`, potentially causing a segfault.

ext/pgsql/pgsql.c

@@ -1201,7 +1201,7 @@ PHP_FUNCTION(pg_query_params)
 			} else {
 				zend_string *param_str = zval_try_get_string(tmp);
 				if (!param_str) {
-					_php_pgsql_free_params(params, num_params);
+					_php_pgsql_free_params(params, i);
 					RETURN_THROWS();
 				}
 				params[i] = estrndup(ZSTR_VAL(param_str), ZSTR_LEN(param_str));
@@ -3918,8 +3918,8 @@ PHP_FUNCTION(pg_send_execute)
 				params[i] = NULL;
 			} else {
 				zend_string *tmp_str = zval_try_get_string(tmp);
-				if (UNEXPECTED(!tmp)) {
-					_php_pgsql_free_params(params, num_params);
+				if (UNEXPECTED(!tmp_str)) {
+					_php_pgsql_free_params(params, i);
 					return;
 				}
 				params[i] = estrndup(ZSTR_VAL(tmp_str), ZSTR_LEN(tmp_str));

ext/pgsql/tests/bug81720.phpt

@@ -0,0 +1,27 @@
+--TEST--
+Bug #81720 (Uninitialized array in pg_query_params() leading to RCE)
+--SKIPIF--
+<?php include("skipif.inc"); ?>
+--FILE--
+<?php
+include('config.inc');
+
+$conn = pg_connect($conn_str);
+
+try {
+    pg_query_params($conn, 'SELECT $1, $2', [1, new stdClass()]);
+} catch (Throwable $ex) {
+    echo $ex->getMessage(), PHP_EOL;
+}
+
+try {
+    pg_send_prepare($conn, "my_query", 'SELECT $1, $2');
+    pg_get_result($conn);
+    pg_send_execute($conn, "my_query", [1, new stdClass()]);
+} catch (Throwable $ex) {
+    echo $ex->getMessage(), PHP_EOL;
+}
+?>
+--EXPECT--
+Object of class stdClass could not be converted to string
+Object of class stdClass could not be converted to string