Added FD reopener

.gitmodules

@@ -7,3 +7,6 @@
 [submodule "module/jni/system_properties"]
 	path = module/jni/system_properties
 	url = https://github.com/topjohnwu/system_properties
+[submodule "module/jni/aosp_fd_utils"]
+	path = module/jni/aosp_fd_utils
+	url = https://github.com/snake-4/aosp_fd_utils.git

module/jni/Android.mk

@@ -3,10 +3,11 @@ LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/include $(LOCAL_PATH)/elfio
 LOCAL_MODULE := zygisk
-LOCAL_SRC_FILES := utils.cpp map_parser.cpp mountinfo_parser.cpp modules.cpp main.cpp
-LOCAL_STATIC_LIBRARIES := libcxx libsystemproperties
+LOCAL_SRC_FILES := fd_reopener.cpp utils.cpp map_parser.cpp mountinfo_parser.cpp modules.cpp main.cpp
+LOCAL_STATIC_LIBRARIES := libcxx libsystemproperties libfdutils
 LOCAL_LDLIBS := -llog
 include $(BUILD_SHARED_LIBRARY)
 
 include jni/libcxx/Android.mk
-include jni/system_properties/Android.mk
+include jni/system_properties/Android.mk
+include jni/aosp_fd_utils/Android.mk

module/jni/fd_reopener.cpp

@@ -0,0 +1,33 @@
+#include "fd_reopener.hpp"
+#include <fd_utils.h>
+#include <string>
+#include <utility>
+#include "logging.hpp"
+
+FDReopener::ScopedRegularReopener::ScopedRegularReopener()
+{
+    auto pFdSet = GetOpenFds([](const std::string &error)
+                             { LOGE("GetOpenFds: %s", error.c_str()); });
+    if (pFdSet)
+    {
+        for (const auto &fd : *pFdSet)
+        {
+            auto pFDI = FileDescriptorInfo::CreateFromFd(fd, [fd](const std::string &error)
+                                                         { LOGE("CreateFromFd(%d): %s", fd, error.c_str()); });
+
+            // Only process regular files that are not memfds
+            if (pFDI && !pFDI->is_sock && !pFDI->file_path.starts_with("/memfd:"))
+                fdi_vector.emplace_back(std::move(pFDI));
+        }
+    }
+}
+
+FDReopener::ScopedRegularReopener::~ScopedRegularReopener()
+{
+    for (const auto &pFDI : fdi_vector)
+    {
+        LOGD("Reopening FD %d with %s", pFDI->fd, pFDI->file_path.c_str());
+        pFDI->ReopenOrDetach([fd = pFDI->fd](const std::string &error)
+                             { LOGE("ReopenOrDetach(%d): %s", fd, error.c_str()); });
+    }
+}

module/jni/include/fd_reopener.hpp

@@ -0,0 +1,19 @@
+#pragma once
+#include "fd_utils.h"
+#include <vector>
+#include <memory>
+
+namespace FDReopener
+{
+    class ScopedRegularReopener
+    {
+    public:
+        ScopedRegularReopener();
+        ~ScopedRegularReopener();
+
+    private:
+        ScopedRegularReopener(const ScopedRegularReopener &);
+        void operator=(const ScopedRegularReopener &);
+        std::vector<std::unique_ptr<FileDescriptorInfo>> fdi_vector;
+    };
+}

module/jni/main.cpp

@@ -9,6 +9,7 @@
 #include "logging.hpp"
 #include "utils.hpp"
 #include "modules.hpp"
+#include "fd_reopener.hpp"
 
 using zygisk::Api;
 using zygisk::AppSpecializeArgs;
@@ -46,6 +47,8 @@ DCL_HOOK_FUNC(static int, unshare, int flags)
 /*
  * The reason why we hook setresuid is because so far it has been unconditionally called
  * and we still have CAP_SYS_ADMIN during this call.
+ * Also, KSU hooks setuid and unmounts some overlays
+ * so we have to run our code before the syscall.
  */
 DCL_HOOK_FUNC(static int, setresuid, uid_t ruid, uid_t euid, uid_t suid)
 {
@@ -97,6 +100,8 @@ class ZygiskModule : public zygisk::ModuleBase
 
         callbackFunction = [fd = companionFd]()
         {
+            FDReopener::ScopedRegularReopener srr;
+
             bool result = false;
             if (fd != -1)
             {