Replace use of overlayfs' override_creds with overlay_remounter
This new solution does not require the use of non-upstreamed
override_creds patches.
Test: system/core/fs_mgr/tests/adb-remount-test.sh
Bug: 388912628
Change-Id: I2bc86a7171c014f88786c6ab97c8788ad024b264
diff --git a/overlay_remounter/Android.bp b/overlay_remounter/Android.bp
new file mode 100644
index 0000000..d74f7da
--- /dev/null
+++ b/overlay_remounter/Android.bp
@@ -0,0 +1,34 @@
+//
+// Copyright (C) 2025 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+cc_binary {
+ name: "overlay_remounter",
+ srcs: [
+ "overlay_remounter.cpp",
+ ],
+ cflags: [
+ "-D_FILE_OFFSET_BITS=64",
+ "-Wall",
+ "-Werror",
+ ],
+ static_libs: [
+ "libbase",
+ "liblog",
+ ],
+ system_shared_libs: [],
+ static_executable: true,
+ install_in_xbin: true,
+}
diff --git a/overlay_remounter/overlay_remounter.cpp b/overlay_remounter/overlay_remounter.cpp
new file mode 100644
index 0000000..ddf97fa
--- /dev/null
+++ b/overlay_remounter/overlay_remounter.cpp
@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2025 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <sys/mount.h>
+#include <unistd.h>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/strings.h>
+
+int main(int /*argc*/, char** argv) {
+ android::base::InitLogging(argv, &android::base::KernelLogger);
+ LOG(INFO) << "Overlay remounter will remount all overlay mount points in the overlay_remounter "
+ "domain";
+
+ // Remount ouerlayfs
+ std::string contents;
+ auto result = android::base::ReadFileToString("/proc/mounts", &contents, true);
+
+ auto lines = android::base::Split(contents, "\n");
+ for (auto const& line : lines) {
+ if (!android::base::StartsWith(line, "overlay")) {
+ continue;
+ }
+ auto bits = android::base::Split(line, " ");
+ if (int result = umount(bits[1].c_str()); result == -1) {
+ PLOG(FATAL) << "umount FAILED: " << bits[1];
+ }
+ std::string options;
+ for (auto const& option : android::base::Split(bits[3], ",")) {
+ if (option == "ro" || option == "seclabel" || option == "noatime") continue;
+ if (!options.empty()) options += ',';
+ options += option;
+ }
+ result = mount("overlay", bits[1].c_str(), "overlay", MS_RDONLY | MS_NOATIME,
+ options.c_str());
+ if (result == 0) {
+ LOG(INFO) << "mount succeeded: " << bits[1] << " " << options;
+ } else {
+ PLOG(FATAL) << "mount FAILED: " << bits[1] << " " << bits[3];
+ }
+ }
+
+ const char* path = "/system/bin/init";
+ const char* args[] = {path, "second_stage", nullptr};
+ execv(path, const_cast<char**>(args));
+
+ // execv() only returns if an error happened, in which case we
+ // panic and never return from this function.
+ PLOG(FATAL) << "execv(\"" << path << "\") failed";
+
+ return 1;
+}