[HttpFoundation] Break infinite loop in PdoSessionHandler when MySQL …

…is in loose mode

Session/Storage/Handler/PdoSessionHandler.php

@@ -494,6 +494,7 @@ private function doRead($sessionId)
         $selectSql = $this->getSelectSql();
         $selectStmt = $this->pdo->prepare($selectSql);
         $selectStmt->bindParam(':id', $sessionId, \PDO::PARAM_STR);
+        $insertStmt = null;
 
         do {
             $selectStmt->execute();
@@ -509,6 +510,11 @@ private function doRead($sessionId)
                 return is_resource($sessionRows[0][0]) ? stream_get_contents($sessionRows[0][0]) : $sessionRows[0][0];
             }
 
+            if (null !== $insertStmt) {
+                $this->rollback();
+                throw new \RuntimeException('Failed to read session: INSERT reported a duplicate id but next SELECT did not return any data.');
+            }
+
             if (self::LOCK_TRANSACTIONAL === $this->lockMode && 'sqlite' !== $this->driver) {
                 // Exclusive-reading of non-existent rows does not block, so we need to do an insert to block
                 // until other connections to the session are committed.