| /* |
| * 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 <fcntl.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/statvfs.h> |
| #include <sys/types.h> |
| #include <sys/vfs.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 <android-base/unique_fd.h> |
| #include <ext4_utils/ext4_utils.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(const fstab*) { |
| 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. Right |
| // after 'trigger load_persist_props_action' is done. |
| bool fs_mgr_boot_completed() { |
| return android::base::GetBoolProperty("ro.persistent_properties.ready", false); |
| } |
| |
| 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 ""; |
| } |
| |
| // At less than 1% free space return value of false, |
| // means we will try to wrap with overlayfs. |
| bool fs_mgr_filesystem_has_space(const char* mount_point) { |
| // If we have access issues to find out space remaining, return true |
| // to prevent us trying to override with overlayfs. |
| struct statvfs vst; |
| if (statvfs(mount_point, &vst)) return true; |
| |
| static constexpr int kPercentThreshold = 1; // 1% |
| |
| return (vst.f_bfree >= (vst.f_blocks * kPercentThreshold / 100)); |
| } |
| |
| bool fs_mgr_overlayfs_enabled(const struct fstab_rec* fsrec) { |
| // readonly filesystem, can not be mount -o remount,rw |
| // if squashfs or if free space is (near) zero making such a remount |
| // virtually useless, or if there are shared blocks that prevent remount,rw |
| return ("squashfs"s == fsrec->fs_type) || |
| fs_mgr_has_shared_blocks(fsrec->mount_point, fsrec->blk_device) || |
| !fs_mgr_filesystem_has_space(fsrec->mount_point); |
| } |
| |
| const auto kUpperName = "upper"s; |
| const auto kWorkName = "work"s; |
| const auto kOverlayTopDir = "/overlay"s; |
| |
| std::string fs_mgr_get_overlayfs_candidate(const std::string& mount_point) { |
| if (!fs_mgr_is_dir(mount_point)) return ""; |
| auto dir = |
| kOverlayMountPoint + kOverlayTopDir + "/" + android::base::Basename(mount_point) + "/"; |
| auto upper = dir + kUpperName; |
| if (!fs_mgr_is_dir(upper)) return ""; |
| auto work = dir + kWorkName; |
| if (!fs_mgr_is_dir(work)) return ""; |
| if (!fs_mgr_dir_is_writable(work)) return ""; |
| return dir; |
| } |
| |
| const auto kLowerdirOption = "lowerdir="s; |
| const auto kUpperdirOption = "upperdir="s; |
| |
| // default options for mount_point, returns empty string for none available. |
| std::string fs_mgr_get_overlayfs_options(const std::string& mount_point) { |
| auto candidate = fs_mgr_get_overlayfs_candidate(mount_point); |
| if (candidate.empty()) return ""; |
| |
| auto context = fs_mgr_get_context(mount_point); |
| if (!context.empty()) context = ",rootcontext="s + context; |
| return "override_creds=off,"s + kLowerdirOption + mount_point + "," + kUpperdirOption + |
| candidate + kUpperName + ",workdir=" + candidate + kWorkName + 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; |
| } |
| |
| const char* fs_mgr_mount_point(const fstab* fstab, const char* mount_point) { |
| if (!mount_point) return mount_point; |
| if ("/"s != mount_point) return mount_point; |
| if (!fs_mgr_system_root_image(fstab)) return mount_point; |
| return "/system"; |
| } |
| |
| // 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) { |
| auto save_errno = errno; |
| overlayfs_in_kernel = !access("/sys/module/overlay/parameters/override_creds", F_OK); |
| errno = save_errno; |
| } |
| return overlayfs_in_kernel; |
| } |
| |
| bool fs_mgr_overlayfs_already_mounted(const std::string& mount_point) { |
| std::unique_ptr<fstab, decltype(&fs_mgr_free_fstab)> fstab(fs_mgr_read_fstab("/proc/mounts"), |
| fs_mgr_free_fstab); |
| if (!fstab) return false; |
| const auto lowerdir = kLowerdirOption + 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 (mount_point != fsrec_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; |
| } |
| |
| bool fs_mgr_overlayfs_verity_enabled(const std::string& basename_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_wants_overlayfs(const fstab_rec* fsrec) { |
| if (!fsrec) return false; |
| |
| auto fsrec_mount_point = fsrec->mount_point; |
| if (!fsrec_mount_point || !fsrec_mount_point[0]) return false; |
| if (!fsrec->blk_device) 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; |
| |
| return !fs_mgr_overlayfs_verity_enabled(android::base::Basename(fsrec_mount_point)); |
| } |
| |
| 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 << "opendir " << 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 << "rmdir " << file; |
| } |
| continue; |
| } |
| if (!unlink(file.c_str())) { |
| if (change) *change = true; |
| } else { |
| ret = false; |
| PERROR << "rm " << file; |
| } |
| } |
| return ret; |
| } |
| |
| constexpr char kOverlayfsFileContext[] = "u:object_r:overlayfs_file:s0"; |
| |
| 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) + "/"; |
| |
| if (setfscreatecon(kOverlayfsFileContext)) { |
| ret = false; |
| PERROR << "setfscreatecon " << kOverlayfsFileContext; |
| } |
| auto save_errno = errno; |
| if (!mkdir(fsrec_mount_point.c_str(), 0755)) { |
| if (change) *change = true; |
| } else if (errno != EEXIST) { |
| ret = false; |
| PERROR << "mkdir " << fsrec_mount_point; |
| } else { |
| errno = save_errno; |
| } |
| |
| save_errno = errno; |
| if (!mkdir((fsrec_mount_point + kWorkName).c_str(), 0755)) { |
| if (change) *change = true; |
| } else if (errno != EEXIST) { |
| ret = false; |
| PERROR << "mkdir " << fsrec_mount_point << kWorkName; |
| } else { |
| errno = save_errno; |
| } |
| setfscreatecon(nullptr); |
| |
| auto new_context = fs_mgr_get_context(mount_point); |
| if (!new_context.empty() && setfscreatecon(new_context.c_str())) { |
| ret = false; |
| PERROR << "setfscreatecon " << new_context; |
| } |
| auto upper = fsrec_mount_point + kUpperName; |
| save_errno = errno; |
| if (!mkdir(upper.c_str(), 0755)) { |
| if (change) *change = true; |
| } else if (errno != EEXIST) { |
| ret = false; |
| PERROR << "mkdir " << upper; |
| } else { |
| errno = save_errno; |
| } |
| if (!new_context.empty()) setfscreatecon(nullptr); |
| |
| return ret; |
| } |
| |
| bool fs_mgr_overlayfs_mount(const std::string& mount_point) { |
| auto options = fs_mgr_get_overlayfs_options(mount_point); |
| if (options.empty()) return false; |
| |
| // hijack __mount() report format to help triage |
| auto report = "__mount(source=overlay,target="s + mount_point + ",type=overlay"; |
| const auto opt_list = android::base::Split(options, ","); |
| for (const auto opt : opt_list) { |
| if (android::base::StartsWith(opt, kUpperdirOption)) { |
| report = report + "," + opt; |
| break; |
| } |
| } |
| report = report + ")="; |
| |
| auto ret = mount("overlay", mount_point.c_str(), "overlay", MS_RDONLY | MS_RELATIME, |
| options.c_str()); |
| if (ret) { |
| PERROR << report << ret; |
| return false; |
| } else { |
| LINFO << report << ret; |
| return true; |
| } |
| } |
| |
| std::vector<std::string> fs_mgr_candidate_list(const fstab* fstab, |
| const char* mount_point = nullptr) { |
| std::vector<std::string> mounts; |
| if (!fstab) return mounts; |
| |
| for (auto i = 0; i < fstab->num_entries; i++) { |
| const auto fsrec = &fstab->recs[i]; |
| if (!fs_mgr_wants_overlayfs(fsrec)) continue; |
| std::string new_mount_point(fs_mgr_mount_point(fstab, fsrec->mount_point)); |
| if (mount_point && (new_mount_point != mount_point)) continue; |
| auto duplicate_or_more_specific = false; |
| for (auto it = mounts.begin(); it != mounts.end();) { |
| if ((*it == new_mount_point) || |
| (android::base::StartsWith(new_mount_point, *it + "/"))) { |
| duplicate_or_more_specific = true; |
| break; |
| } |
| if (android::base::StartsWith(*it, new_mount_point + "/")) { |
| it = mounts.erase(it); |
| } else { |
| ++it; |
| } |
| } |
| if (!duplicate_or_more_specific) mounts.emplace_back(new_mount_point); |
| } |
| // if not itemized /system or /, system as root, fake up |
| // fs_mgr_wants_overlayfs evaluation of /system as candidate. |
| |
| if ((std::find(mounts.begin(), mounts.end(), "/system") == mounts.end()) && |
| !fs_mgr_get_entry_for_mount_point(const_cast<struct fstab*>(fstab), "/") && |
| !fs_mgr_get_entry_for_mount_point(const_cast<struct fstab*>(fstab), "/system") && |
| !fs_mgr_overlayfs_verity_enabled("system")) { |
| mounts.emplace_back("/system"); |
| } |
| return mounts; |
| } |
| |
| } // namespace |
| |
| bool fs_mgr_overlayfs_mount_all(const fstab* fstab) { |
| auto ret = false; |
| |
| if (!fs_mgr_wants_overlayfs()) return ret; |
| |
| if (!fstab) return ret; |
| |
| for (const auto& mount_point : fs_mgr_candidate_list(fstab)) { |
| if (fs_mgr_overlayfs_already_mounted(mount_point)) continue; |
| if (fs_mgr_overlayfs_mount(mount_point)) 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 << "setup"; |
| return ret; |
| } |
| |
| std::unique_ptr<fstab, decltype(&fs_mgr_free_fstab)> fstab(fs_mgr_read_fstab_default(), |
| fs_mgr_free_fstab); |
| if (fstab && !fs_mgr_get_entry_for_mount_point(fstab.get(), kOverlayMountPoint)) return ret; |
| auto mounts = fs_mgr_candidate_list(fstab.get(), fs_mgr_mount_point(fstab.get(), mount_point)); |
| if (fstab && mounts.empty()) return ret; |
| |
| if (setfscreatecon(kOverlayfsFileContext)) { |
| PERROR << "setfscreatecon " << kOverlayfsFileContext; |
| } |
| auto overlay = kOverlayMountPoint + kOverlayTopDir; |
| auto save_errno = errno; |
| if (!mkdir(overlay.c_str(), 0755)) { |
| if (change) *change = true; |
| } else if (errno != EEXIST) { |
| PERROR << "mkdir " << overlay; |
| } else { |
| errno = save_errno; |
| } |
| setfscreatecon(nullptr); |
| 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; |
| mount_point = fs_mgr_mount_point(std::unique_ptr<fstab, decltype(&fs_mgr_free_fstab)>( |
| fs_mgr_read_fstab_default(), fs_mgr_free_fstab) |
| .get(), |
| mount_point); |
| auto ret = true; |
| const auto overlay = kOverlayMountPoint + kOverlayTopDir; |
| const auto oldpath = overlay + (mount_point ? "/"s + mount_point : ""s); |
| 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 << "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 << "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 << "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 << "teardown"; |
| ret = false; |
| } |
| return ret; |
| } |
| |
| #endif // ALLOW_ADBD_DISABLE_VERITY != 0 |
| |
| bool fs_mgr_has_shared_blocks(const std::string& mount_point, const std::string& dev) { |
| struct statfs fs; |
| if ((statfs((mount_point + "/lost+found").c_str(), &fs) == -1) || |
| (fs.f_type != EXT4_SUPER_MAGIC)) { |
| return false; |
| } |
| |
| android::base::unique_fd fd(open(dev.c_str(), O_RDONLY | O_CLOEXEC)); |
| if (fd < 0) return false; |
| |
| struct ext4_super_block sb; |
| if ((TEMP_FAILURE_RETRY(lseek64(fd, 1024, SEEK_SET)) < 0) || |
| (TEMP_FAILURE_RETRY(read(fd, &sb, sizeof(sb))) < 0)) { |
| return false; |
| } |
| |
| struct fs_info info; |
| if (ext4_parse_sb(&sb, &info) < 0) return false; |
| |
| return (info.feat_ro_compat & EXT4_FEATURE_RO_COMPAT_SHARED_BLOCKS) != 0; |
| } |