From 560ca69ae833f8493e279c76859f57d915f6867b Mon Sep 17 00:00:00 2001
From: Tom Hempel <tom.hempel2001@gmail.com>
Date: Fri, 12 Jun 2026 22:14:51 +0200
Subject: [PATCH] refactored memfd handling to use FFI for Linux, added
 qdb_close_fd function

---
 lib/read_db_cache.php | 55 +++++++++++++++++++++++++++++++++----------
 1 file changed, 42 insertions(+), 13 deletions(-)

diff --git a/lib/read_db_cache.php b/lib/read_db_cache.php
index 09a1759..6936c8a 100644
--- a/lib/read_db_cache.php
+++ b/lib/read_db_cache.php
@@ -99,24 +99,53 @@ function qdb_read_materialize_decrypted_db(): array {
     return [$pdo, $fallback, -1];
 }
 
+/**
+ * @return FFI|null libc handle with memfd_create + close (Linux only)
+ */
+function qdb_linux_libc_ffi() {
+    static $ffi = null;
+    if ($ffi !== null) {
+        return $ffi;
+    }
+    if (PHP_OS_FAMILY !== 'Linux' || !extension_loaded('ffi')) {
+        return null;
+    }
+    try {
+        $ffi = FFI::cdef(
+            'int memfd_create(const char *name, unsigned int flags);
+             int close(int fd);',
+            'libc.so.6'
+        );
+    } catch (Throwable $e) {
+        error_log('qdb_linux_libc_ffi: ' . $e->getMessage());
+        return null;
+    }
+    return $ffi;
+}
+
+function qdb_close_fd(int $fd): void {
+    if ($fd < 0) {
+        return;
+    }
+    if (function_exists('posix_close')) {
+        @posix_close($fd);
+        return;
+    }
+    $ffi = qdb_linux_libc_ffi();
+    if ($ffi !== null) {
+        $ffi->close($fd);
+    }
+}
+
 /**
  * @return array{0: int, 1: string}|null [fd, /proc/self/fd/N]
  */
 function qdb_memfd_write(string $bytes): ?array {
-    if (PHP_OS_FAMILY !== 'Linux') {
+    $ffi = qdb_linux_libc_ffi();
+    if ($ffi === null) {
         return null;
     }
-    if (!extension_loaded('ffi')) {
-        return null;
-    }
-    static $ffi = null;
     try {
-        if ($ffi === null) {
-            $ffi = FFI::cdef(
-                'int memfd_create(const char *name, unsigned int flags);',
-                'libc.so.6'
-            );
-        }
         $MFD_CLOEXEC = 1;
         $fd = (int)$ffi->memfd_create('qdb_read', $MFD_CLOEXEC);
         if ($fd < 0) {
@@ -124,7 +153,7 @@ function qdb_memfd_write(string $bytes): ?array {
         }
         $written = @file_put_contents('/proc/self/fd/' . $fd, $bytes);
         if ($written === false || $written !== strlen($bytes)) {
-            @close($fd);
+            qdb_close_fd($fd);
             return null;
         }
         return [$fd, '/proc/self/fd/' . $fd];
@@ -204,7 +233,7 @@ function qdb_read_cache_reset(): void {
     $state['signature'] = '';
     $state['pdo'] = null;
     if ($state['memfdFd'] >= 0) {
-        @close($state['memfdFd']);
+        qdb_close_fd($state['memfdFd']);
     }
     $state['memfdFd'] = -1;
     if ($state['memfdPath'] !== '' && is_file($state['memfdPath'])) {