| /* |
| * 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. 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 ""; |
| } |
| |
| 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) { |
| 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_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 |