Merge changes from topic "squashfs+overlayfs" am: d88b52e7f4 (981b4787) · Commits · e / os / android_system_core

adb/daemon/remount_service.cpp

+19 −9

Original line number	Diff line number	Diff line
		@@ -30,6 +30,7 @@
		#include <sys/vfs.h>
		#include <unistd.h>

		#include <memory>
		#include <set>
		#include <string>
		#include <vector>
		@@ -38,28 +39,30 @@
		#include <bootloader_message/bootloader_message.h>
		#include <cutils/android_reboot.h>
		#include <ext4_utils/ext4_utils.h>
		#include <fs_mgr.h>
		#include <fs_mgr_overlayfs.h>

		#include "adb.h"
		#include "adb_io.h"
		#include "adb_unique_fd.h"
		#include "adb_utils.h"
		#include "fs_mgr.h"
		#include "set_verity_enable_state_service.h"

		// Returns the device used to mount a directory in /proc/mounts.
		// Returns the last device used to mount a directory in /proc/mounts.
		// This will find overlayfs entry where upperdir=lowerdir, to make sure
		// remount is associated with the correct directory.
		static std::string find_proc_mount(const char* dir) {
		std::unique_ptr<FILE, int()(FILE)> fp(setmntent("/proc/mounts", "r"), endmntent);
		if (!fp) {
		return "";
		}
		std::string mnt_fsname;
		if (!fp) return mnt_fsname;

		mntent* e;
		while ((e = getmntent(fp.get())) != nullptr) {
		if (strcmp(dir, e->mnt_dir) == 0) {
		return e->mnt_fsname;
		mnt_fsname = e->mnt_fsname;
		}
		}
		return "";
		return mnt_fsname;
		}

		// Returns the device used to mount a directory in the fstab.
		@@ -81,6 +84,7 @@ static std::string find_mount(const char* dir, bool is_root) {
		}

		bool make_block_device_writable(const std::string& dev) {
		if ((dev == "overlay") \|\| (dev == "overlayfs")) return true;
		int fd = unix_open(dev.c_str(), O_RDONLY \| O_CLOEXEC);
		if (fd == -1) {
		return false;
		@@ -234,6 +238,14 @@ void remount_service(unique_fd fd, const std::string& cmd) {
		partitions.push_back("/system");
		}

		bool verity_enabled = (system_verified \|\| vendor_verified);

		// If we can use overlayfs, lets get it in place first
		// before we struggle with determining deduplication operations.
		if (!verity_enabled && fs_mgr_overlayfs_setup() && fs_mgr_overlayfs_mount_all()) {
		WriteFdExactly(fd.get(), "overlayfs mounted\n");
		}

		// Find partitions that are deduplicated, and can be un-deduplicated.
		std::set<std::string> dedup;
		for (const auto& partition : partitions) {
		@@ -246,8 +258,6 @@ void remount_service(unique_fd fd, const std::string& cmd) {
		}
		}

		bool verity_enabled = (system_verified \|\| vendor_verified);

		// Reboot now if the user requested it (and an operation needs a reboot).
		if (user_requested_reboot) {
		if (!dedup.empty() \|\| verity_enabled) {

adb/daemon/set_verity_enable_state_service.cpp

+43 −5

Original line number	Diff line number	Diff line
		@@ -19,6 +19,7 @@
		#include "set_verity_enable_state_service.h"
		#include "sysdeps.h"

		#include <errno.h>
		#include <fcntl.h>
		#include <inttypes.h>
		#include <libavb_user/libavb_user.h>
		@@ -28,12 +29,14 @@

		#include <android-base/properties.h>
		#include <android-base/stringprintf.h>
		#include <fs_mgr.h>
		#include <fs_mgr_overlayfs.h>
		#include <fstab/fstab.h>
		#include <log/log_properties.h>

		#include "adb.h"
		#include "adb_io.h"
		#include "adb_unique_fd.h"
		#include "fs_mgr.h"
		#include "remount_service.h"

		#include "fec/io.h"
		@@ -46,6 +49,10 @@ static const bool kAllowDisableVerity = true;
		static const bool kAllowDisableVerity = false;
		#endif

		void suggest_run_adb_root(int fd) {
		if (getuid() != 0) WriteFdExactly(fd, "Maybe run adb root?\n");
		}

		/* Turn verity on/off */
		static bool set_verity_enabled_state(int fd, const char* block_device, const char* mount_point,
		bool enable) {
		@@ -59,7 +66,7 @@ static bool set_verity_enabled_state(int fd, const char* block_device, const cha

		if (!fh) {
		WriteFdFmt(fd, "Could not open block device %s (%s).\n", block_device, strerror(errno));
		WriteFdFmt(fd, "Maybe run adb root?\n");
		suggest_run_adb_root(fd);
		return false;
		}

		@@ -87,6 +94,17 @@ static bool set_verity_enabled_state(int fd, const char* block_device, const cha
		return false;
		}

		auto change = false;
		errno = 0;
		if (enable ? fs_mgr_overlayfs_teardown(mount_point, &change)
		: fs_mgr_overlayfs_setup(nullptr, mount_point, &change)) {
		if (change) {
		WriteFdFmt(fd, "%s overlayfs for %s\n", enable ? "disabling" : "using", mount_point);
		}
		} else if (errno) {
		WriteFdFmt(fd, "Overlayfs %s for %s failed with error %s\n", enable ? "teardown" : "setup",
		mount_point, strerror(errno));
		}
		WriteFdFmt(fd, "Verity %s on %s\n", enable ? "enabled" : "disabled", mount_point);
		return true;
		}
		@@ -103,6 +121,22 @@ static bool is_avb_device_locked() {
		return android::base::GetProperty("ro.boot.vbmeta.device_state", "") == "locked";
		}

		static bool overlayfs_setup(int fd, bool enable) {
		auto change = false;
		errno = 0;
		if (enable ? fs_mgr_overlayfs_teardown(nullptr, &change)
		: fs_mgr_overlayfs_setup(nullptr, nullptr, &change)) {
		if (change) {
		WriteFdFmt(fd, "%s overlayfs\n", enable ? "disabling" : "using");
		}
		} else if (errno) {
		WriteFdFmt(fd, "Overlayfs %s failed with error %s\n", enable ? "teardown" : "setup",
		strerror(errno));
		suggest_run_adb_root(fd);
		}
		return change;
		}

		/* Use AVB to turn verity on/off */
		static bool set_avb_verity_enabled_state(int fd, AvbOps* ops, bool enable_verity) {
		std::string ab_suffix = get_ab_suffix();
		@@ -128,6 +162,7 @@ static bool set_avb_verity_enabled_state(int fd, AvbOps* ops, bool enable_verity
		return false;
		}

		overlayfs_setup(fd, enable_verity);
		WriteFdFmt(fd, "Successfully %s verity\n", enable_verity ? "enabled" : "disabled");
		return true;
		}
		@@ -150,6 +185,7 @@ void set_verity_enabled_state_service(unique_fd fd, bool enable) {
		}

		if (!android::base::GetBoolProperty("ro.secure", false)) {
		overlayfs_setup(fd, enable);
		WriteFdExactly(fd.get(), "verity not enabled - ENG build\n");
		return;
		}
		@@ -177,13 +213,14 @@ void set_verity_enabled_state_service(unique_fd fd, bool enable) {
		// Not using AVB - assume VB1.0.

		// read all fstab entries at once from all sources
		fstab = fs_mgr_read_fstab_default();
		if (!fstab) fstab = fs_mgr_read_fstab_default();
		if (!fstab) {
		WriteFdExactly(fd.get(), "Failed to read fstab\nMaybe run adb root?\n");
		WriteFdExactly(fd.get(), "Failed to read fstab\n");
		suggest_run_adb_root(fd.get());
		return;
		}

		// Loop through entries looking for ones that vold manages.
		// Loop through entries looking for ones that verity manages.
		for (int i = 0; i < fstab->num_entries; i++) {
		if (fs_mgr_is_verified(&fstab->recs[i])) {
		if (set_verity_enabled_state(fd.get(), fstab->recs[i].blk_device,
		@@ -193,6 +230,7 @@ void set_verity_enabled_state_service(unique_fd fd, bool enable) {
		}
		}
		}
		if (!any_changed) any_changed = overlayfs_setup(fd, enable);

		if (any_changed) {
		WriteFdExactly(fd.get(), "Now reboot your device for settings to take effect\n");

fs_mgr/Android.bp

+1 −0

Original line number	Diff line number	Diff line
		@@ -43,6 +43,7 @@ cc_library {
		"fs_mgr_avb.cpp",
		"fs_mgr_avb_ops.cpp",
		"fs_mgr_dm_linear.cpp",
		"fs_mgr_overlayfs.cpp",
		],
		shared_libs: [
		"libfec",

fs_mgr/fs_mgr.cpp

+7 −1

Original line number	Diff line number	Diff line
		@@ -14,6 +14,8 @@
		* limitations under the License.
		*/

		#include "fs_mgr.h"

		#include <ctype.h>
		#include <dirent.h>
		#include <errno.h>
		@@ -51,6 +53,7 @@
		#include <ext4_utils/ext4_sb.h>
		#include <ext4_utils/ext4_utils.h>
		#include <ext4_utils/wipe.h>
		#include <fs_mgr_overlayfs.h>
		#include <libdm/dm.h>
		#include <linux/fs.h>
		#include <linux/loop.h>
		@@ -58,7 +61,6 @@
		#include <log/log_properties.h>
		#include <logwrap/logwrap.h>

		#include "fs_mgr.h"
		#include "fs_mgr_avb.h"
		#include "fs_mgr_priv.h"

		@@ -1035,6 +1037,10 @@ int fs_mgr_mount_all(struct fstab *fstab, int mount_mode)
		}
		}

		#if ALLOW_ADBD_DISABLE_VERITY == 1 // "userdebug" build
		fs_mgr_overlayfs_mount_all();
		#endif

		if (error_count) {
		return FS_MGR_MNTALL_FAIL;
		} else {

fs_mgr/fs_mgr_overlayfs.cpp

0 → 100644

+478 −0

Original line number	Diff line number	Diff line
		/*
		* Copyright (C) 2018 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 <dirent.h>
		#include <errno.h>
		#include <linux/fs.h>
		#include <selinux/selinux.h>
		#include <stdio.h>
		#include <string.h>
		#include <sys/mount.h>
		#include <sys/param.h>
		#include <sys/stat.h>
		#include <sys/types.h>
		#include <unistd.h>

		#include <map>
		#include <memory>
		#include <string>
		#include <vector>

		#include <android-base/file.h>
		#include <android-base/macros.h>
		#include <android-base/properties.h>
		#include <android-base/strings.h>
		#include <fs_mgr_overlayfs.h>
		#include <fstab/fstab.h>

		#include "fs_mgr_priv.h"

		using namespace std::literals;

		#if ALLOW_ADBD_DISABLE_VERITY == 0 // If we are a user build, provide stubs

		bool fs_mgr_overlayfs_mount_all() {
		return false;
		}

		bool fs_mgr_overlayfs_setup(const char, const char, bool* change) {
		if (change) change = false;
		return false;
		}

		bool fs_mgr_overlayfs_teardown(const char, bool change) {
		if (change) change = false;
		return false;
		}

		#else // ALLOW_ADBD_DISABLE_VERITY == 0

		namespace {

		// acceptable overlayfs backing storage
		const auto kOverlayMountPoint = "/cache"s;

		// return true if everything is mounted, but before adb is started. At
		// 'trigger firmware_mounts_complete' after 'trigger load_persist_props_action'.
		bool fs_mgr_boot_completed() {
		return !android::base::GetProperty("ro.boottime.init", "").empty() &&
		!!access("/dev/.booting", F_OK);
		}

		bool fs_mgr_is_dir(const std::string& path) {
		struct stat st;
		return !stat(path.c_str(), &st) && S_ISDIR(st.st_mode);
		}

		// Similar test as overlayfs workdir= validation in the kernel for read-write
		// validation, except we use fs_mgr_work. Covers space and storage issues.
		bool fs_mgr_dir_is_writable(const std::string& path) {
		auto test_directory = path + "/fs_mgr_work";
		rmdir(test_directory.c_str());
		auto ret = !mkdir(test_directory.c_str(), 0700);
		return ret \| !rmdir(test_directory.c_str());
		}

		std::string fs_mgr_get_context(const std::string& mount_point) {
		char* ctx = nullptr;
		auto len = getfilecon(mount_point.c_str(), &ctx);
		if ((len > 0) && ctx) {
		std::string context(ctx, len);
		free(ctx);
		return context;
		}
		return "";
		}

		bool fs_mgr_overlayfs_enabled(const struct fstab_rec* fsrec) {
		// readonly filesystem, can not be mount -o remount,rw
		return "squashfs"s == fsrec->fs_type;
		}

		constexpr char upper_name[] = "upper";
		constexpr char work_name[] = "work";

		std::string fs_mgr_get_overlayfs_candidate(const std::string& mount_point) {
		if (!fs_mgr_is_dir(mount_point)) return "";
		auto dir = kOverlayMountPoint + "/overlay/" + android::base::Basename(mount_point) + "/";
		auto upper = dir + upper_name;
		if (!fs_mgr_is_dir(upper)) return "";
		auto work = dir + work_name;
		if (!fs_mgr_is_dir(work)) return "";
		if (!fs_mgr_dir_is_writable(work)) return "";
		return dir;
		}

		constexpr char lowerdir_option[] = "lowerdir=";
		constexpr char upperdir_option[] = "upperdir=";

		// default options for mount_point, returns empty string for none available.
		std::string fs_mgr_get_overlayfs_options(const char* mount_point) {
		auto fsrec_mount_point = std::string(mount_point);
		auto candidate = fs_mgr_get_overlayfs_candidate(fsrec_mount_point);
		if (candidate.empty()) return "";

		auto context = fs_mgr_get_context(fsrec_mount_point);
		if (!context.empty()) context = ",rootcontext="s + context;
		return "override_creds=off,"s + lowerdir_option + fsrec_mount_point + "," + upperdir_option +
		candidate + upper_name + ",workdir=" + candidate + work_name + context;
		}

		bool fs_mgr_system_root_image(const fstab* fstab) {
		if (!fstab) { // can not happen?
		// This will return empty on init first_stage_mount,
		// hence why we prefer checking the fstab instead.
		return android::base::GetBoolProperty("ro.build.system_root_image", false);
		}
		for (auto i = 0; i < fstab->num_entries; i++) {
		const auto fsrec = &fstab->recs[i];
		auto fsrec_mount_point = fsrec->mount_point;
		if (!fsrec_mount_point) continue;
		if ("/system"s == fsrec_mount_point) return false;
		}
		return true;
		}

		std::string fs_mgr_get_overlayfs_options(const fstab* fstab, const char* mount_point) {
		if (fs_mgr_system_root_image(fstab) && ("/"s == mount_point)) mount_point = "/system";

		return fs_mgr_get_overlayfs_options(mount_point);
		}

		// return true if system supports overlayfs
		bool fs_mgr_wants_overlayfs() {
		// This will return empty on init first_stage_mount, so speculative
		// determination, empty (unset) _or_ "1" is true which differs from the
		// official ro.debuggable policy. ALLOW_ADBD_DISABLE_VERITY == 0 should
		// protect us from false in any case, so this is insurance.
		auto debuggable = android::base::GetProperty("ro.debuggable", "1");
		if (debuggable != "1") return false;

		// Overlayfs available in the kernel, and patched for override_creds?
		static signed char overlayfs_in_kernel = -1; // cache for constant condition
		if (overlayfs_in_kernel == -1) {
		overlayfs_in_kernel = !access("/sys/module/overlay/parameters/override_creds", F_OK);
		}
		return overlayfs_in_kernel;
		}

		bool fs_mgr_wants_overlayfs(const fstab_rec* fsrec) {
		if (!fsrec) return false;

		auto fsrec_mount_point = fsrec->mount_point;
		if (!fsrec_mount_point) return false;

		if (!fsrec->fs_type) return false;

		// Don't check entries that are managed by vold.
		if (fsrec->fs_mgr_flags & (MF_VOLDMANAGED \| MF_RECOVERYONLY)) return false;

		// Only concerned with readonly partitions.
		if (!(fsrec->flags & MS_RDONLY)) return false;

		// If unbindable, do not allow overlayfs as this could expose us to
		// security issues. On Android, this could also be used to turn off
		// the ability to overlay an otherwise acceptable filesystem since
		// /system and /vendor are never bound(sic) to.
		if (fsrec->flags & MS_UNBINDABLE) return false;

		if (!fs_mgr_overlayfs_enabled(fsrec)) return false;

		// Verity enabled?
		const auto basename_mount_point(android::base::Basename(fsrec_mount_point));
		auto found = false;
		fs_mgr_update_verity_state(
		[&basename_mount_point, &found](fstab_rec, const char mount_point, int, int) {
		if (mount_point && (basename_mount_point == mount_point)) found = true;
		});
		return !found;
		}

		bool fs_mgr_rm_all(const std::string& path, bool* change = nullptr) {
		auto save_errno = errno;
		std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(path.c_str()), closedir);
		if (!dir) {
		if (errno == ENOENT) {
		errno = save_errno;
		return true;
		}
		PERROR << "overlayfs open " << path;
		return false;
		}
		dirent* entry;
		auto ret = true;
		while ((entry = readdir(dir.get()))) {
		if (("."s == entry->d_name) \|\| (".."s == entry->d_name)) continue;
		auto file = path + "/" + entry->d_name;
		if (entry->d_type == DT_UNKNOWN) {
		struct stat st;
		if (!lstat(file.c_str(), &st) && (st.st_mode & S_IFDIR)) entry->d_type = DT_DIR;
		}
		if (entry->d_type == DT_DIR) {
		ret &= fs_mgr_rm_all(file, change);
		if (!rmdir(file.c_str())) {
		if (change) *change = true;
		} else {
		ret = false;
		PERROR << "overlayfs rmdir " << file;
		}
		continue;
		}
		if (!unlink(file.c_str())) {
		if (change) *change = true;
		} else {
		ret = false;
		PERROR << "overlayfs rm " << file;
		}
		}
		return ret;
		}

		bool fs_mgr_overlayfs_setup_one(const std::string& overlay, const std::string& mount_point,
		bool* change) {
		auto ret = true;
		auto fsrec_mount_point = overlay + android::base::Basename(mount_point) + "/";
		auto save_errno = errno;
		if (!mkdir(fsrec_mount_point.c_str(), 0755)) {
		if (change) *change = true;
		} else if (errno != EEXIST) {
		ret = false;
		PERROR << "overlayfs mkdir " << fsrec_mount_point;
		} else {
		errno = save_errno;
		}

		save_errno = errno;
		if (!mkdir((fsrec_mount_point + work_name).c_str(), 0755)) {
		if (change) *change = true;
		} else if (errno != EEXIST) {
		ret = false;
		PERROR << "overlayfs mkdir " << fsrec_mount_point << work_name;
		} else {
		errno = save_errno;
		}

		auto new_context = fs_mgr_get_context(mount_point);
		if (!new_context.empty() && setfscreatecon(new_context.c_str())) {
		ret = false;
		PERROR << "overlayfs setfscreatecon " << new_context;
		}
		auto upper = fsrec_mount_point + upper_name;
		save_errno = errno;
		if (!mkdir(upper.c_str(), 0755)) {
		if (change) *change = true;
		} else if (errno != EEXIST) {
		ret = false;
		PERROR << "overlayfs mkdir " << upper;
		} else {
		errno = save_errno;
		}
		if (!new_context.empty()) setfscreatecon(nullptr);

		return ret;
		}

		bool fs_mgr_overlayfs_mount(const fstab* fstab, const fstab_rec* fsrec) {
		if (!fs_mgr_wants_overlayfs(fsrec)) return false;
		auto fsrec_mount_point = fsrec->mount_point;
		if (!fsrec_mount_point \|\| !fsrec_mount_point[0]) return false;
		auto options = fs_mgr_get_overlayfs_options(fstab, fsrec_mount_point);
		if (options.empty()) return false;

		// hijack __mount() report format to help triage
		auto report = "__mount(source=overlay,target="s + fsrec_mount_point + ",type=overlay";
		const auto opt_list = android::base::Split(options, ",");
		for (const auto opt : opt_list) {
		if (android::base::StartsWith(opt, upperdir_option)) {
		report = report + "," + opt;
		break;
		}
		}
		report = report + ")=";

		auto ret = mount("overlay", fsrec_mount_point, "overlay", MS_RDONLY \| MS_RELATIME,
		options.c_str());
		if (ret) {
		PERROR << report << ret;
		return false;
		} else {
		LINFO << report << ret;
		return true;
		}
		}

		bool fs_mgr_overlayfs_already_mounted(const char* mount_point) {
		if (!mount_point) return false;
		std::unique_ptr<struct fstab, decltype(&fs_mgr_free_fstab)> fstab(
		fs_mgr_read_fstab("/proc/mounts"), fs_mgr_free_fstab);
		if (!fstab) return false;
		const auto lowerdir = std::string(lowerdir_option) + mount_point;
		for (auto i = 0; i < fstab->num_entries; ++i) {
		const auto fsrec = &fstab->recs[i];
		const auto fs_type = fsrec->fs_type;
		if (!fs_type) continue;
		if (("overlay"s != fs_type) && ("overlayfs"s != fs_type)) continue;
		auto fsrec_mount_point = fsrec->mount_point;
		if (!fsrec_mount_point) continue;
		if (strcmp(fsrec_mount_point, mount_point)) continue;
		const auto fs_options = fsrec->fs_options;
		if (!fs_options) continue;
		const auto options = android::base::Split(fs_options, ",");
		for (const auto opt : options) {
		if (opt == lowerdir) {
		return true;
		}
		}
		}
		return false;
		}

		} // namespace

		bool fs_mgr_overlayfs_mount_all() {
		auto ret = false;

		if (!fs_mgr_wants_overlayfs()) return ret;

		std::unique_ptr<struct fstab, decltype(&fs_mgr_free_fstab)> fstab(fs_mgr_read_fstab_default(),
		fs_mgr_free_fstab);
		if (!fstab) return ret;

		for (auto i = 0; i < fstab->num_entries; i++) {
		const auto fsrec = &fstab->recs[i];
		auto fsrec_mount_point = fsrec->mount_point;
		if (!fsrec_mount_point) continue;
		if (fs_mgr_overlayfs_already_mounted(fsrec_mount_point)) continue;

		if (fs_mgr_overlayfs_mount(fstab.get(), fsrec)) ret = true;
		}
		return ret;
		}

		// Returns false if setup not permitted, errno set to last error.
		// If something is altered, set *change.
		bool fs_mgr_overlayfs_setup(const char* backing, const char* mount_point, bool* change) {
		if (change) *change = false;
		auto ret = false;
		if (backing && (kOverlayMountPoint != backing)) {
		errno = EINVAL;
		return ret;
		}
		if (!fs_mgr_wants_overlayfs()) return ret;
		if (!fs_mgr_boot_completed()) {
		errno = EBUSY;
		PERROR << "overlayfs setup";
		return ret;
		}

		std::unique_ptr<struct fstab, decltype(&fs_mgr_free_fstab)> fstab(fs_mgr_read_fstab_default(),
		fs_mgr_free_fstab);
		std::vector<std::string> mounts;
		if (fstab) {
		if (!fs_mgr_get_entry_for_mount_point(fstab.get(), kOverlayMountPoint)) return ret;
		for (auto i = 0; i < fstab->num_entries; i++) {
		const auto fsrec = &fstab->recs[i];
		auto fsrec_mount_point = fsrec->mount_point;
		if (!fsrec_mount_point) continue;
		if (mount_point && strcmp(fsrec_mount_point, mount_point)) continue;
		if (!fs_mgr_wants_overlayfs(fsrec)) continue;
		mounts.emplace_back(fsrec_mount_point);
		}
		if (mounts.empty()) return ret;
		}

		if (mount_point && ("/"s == mount_point) && fs_mgr_system_root_image(fstab.get())) {
		mount_point = "/system";
		}
		auto overlay = kOverlayMountPoint + "/overlay/";
		auto save_errno = errno;
		if (!mkdir(overlay.c_str(), 0755)) {
		if (change) *change = true;
		} else if (errno != EEXIST) {
		PERROR << "overlayfs mkdir " << overlay;
		} else {
		errno = save_errno;
		}
		if (!fstab && mount_point && fs_mgr_overlayfs_setup_one(overlay, mount_point, change)) {
		ret = true;
		}
		for (const auto& fsrec_mount_point : mounts) {
		ret \|= fs_mgr_overlayfs_setup_one(overlay, fsrec_mount_point, change);
		}
		return ret;
		}

		// Returns false if teardown not permitted, errno set to last error.
		// If something is altered, set *change.
		bool fs_mgr_overlayfs_teardown(const char* mount_point, bool* change) {
		if (change) *change = false;
		if (mount_point && ("/"s == mount_point)) {
		std::unique_ptr<struct fstab, decltype(&fs_mgr_free_fstab)> fstab(
		fs_mgr_read_fstab_default(), fs_mgr_free_fstab);
		if (fs_mgr_system_root_image(fstab.get())) mount_point = "/system";
		}
		auto ret = true;
		const auto overlay = kOverlayMountPoint + "/overlay";
		const auto oldpath = overlay + (mount_point ?: "");
		const auto newpath = oldpath + ".teardown";
		ret &= fs_mgr_rm_all(newpath);
		auto save_errno = errno;
		if (rename(oldpath.c_str(), newpath.c_str())) {
		if (change) *change = true;
		} else if (errno != ENOENT) {
		ret = false;
		PERROR << "overlayfs mv " << oldpath << " " << newpath;
		} else {
		errno = save_errno;
		}
		ret &= fs_mgr_rm_all(newpath, change);
		save_errno = errno;
		if (!rmdir(newpath.c_str())) {
		if (change) *change = true;
		} else if (errno != ENOENT) {
		ret = false;
		PERROR << "overlayfs rmdir " << newpath;
		} else {
		errno = save_errno;
		}
		if (mount_point) {
		save_errno = errno;
		if (!rmdir(overlay.c_str())) {
		if (change) *change = true;
		} else if ((errno != ENOENT) && (errno != ENOTEMPTY)) {
		ret = false;
		PERROR << "overlayfs rmdir " << overlay;
		} else {
		errno = save_errno;
		}
		}
		if (!fs_mgr_wants_overlayfs()) {
		// After obligatory teardown to make sure everything is clean, but if
		// we didn't want overlayfs in the the first place, we do not want to
		// waste time on a reboot (or reboot request message).
		if (change) *change = false;
		}
		// And now that we did what we could, lets inform
		// caller that there may still be more to do.
		if (!fs_mgr_boot_completed()) {
		errno = EBUSY;
		PERROR << "overlayfs teardown";
		ret = false;
		}
		return ret;
		}

		#endif // ALLOW_ADBD_DISABLE_VERITY != 0