| /* |
| * Copyright (C) 2019 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 "mount_namespace.h" |
| |
| #include <sys/mount.h> |
| |
| #include <string> |
| #include <vector> |
| |
| #include <ApexProperties.sysprop.h> |
| #include <android-base/file.h> |
| #include <android-base/logging.h> |
| #include <android-base/properties.h> |
| #include <android-base/result.h> |
| #include <android-base/unique_fd.h> |
| #include <apex_manifest.pb.h> |
| |
| #include "util.h" |
| |
| namespace android { |
| namespace init { |
| namespace { |
| |
| static bool BindMount(const std::string& source, const std::string& mount_point, |
| bool recursive = false) { |
| unsigned long mountflags = MS_BIND; |
| if (recursive) { |
| mountflags |= MS_REC; |
| } |
| if (mount(source.c_str(), mount_point.c_str(), nullptr, mountflags, nullptr) == -1) { |
| PLOG(ERROR) << "Failed to bind mount " << source; |
| return false; |
| } |
| return true; |
| } |
| |
| static bool MakeShared(const std::string& mount_point, bool recursive = false) { |
| unsigned long mountflags = MS_SHARED; |
| if (recursive) { |
| mountflags |= MS_REC; |
| } |
| if (mount(nullptr, mount_point.c_str(), nullptr, mountflags, nullptr) == -1) { |
| PLOG(ERROR) << "Failed to change propagation type to shared"; |
| return false; |
| } |
| return true; |
| } |
| |
| static bool MakeSlave(const std::string& mount_point, bool recursive = false) { |
| unsigned long mountflags = MS_SLAVE; |
| if (recursive) { |
| mountflags |= MS_REC; |
| } |
| if (mount(nullptr, mount_point.c_str(), nullptr, mountflags, nullptr) == -1) { |
| PLOG(ERROR) << "Failed to change propagation type to slave"; |
| return false; |
| } |
| return true; |
| } |
| |
| static bool MakePrivate(const std::string& mount_point, bool recursive = false) { |
| unsigned long mountflags = MS_PRIVATE; |
| if (recursive) { |
| mountflags |= MS_REC; |
| } |
| if (mount(nullptr, mount_point.c_str(), nullptr, mountflags, nullptr) == -1) { |
| PLOG(ERROR) << "Failed to change propagation type to private"; |
| return false; |
| } |
| return true; |
| } |
| |
| static int OpenMountNamespace() { |
| int fd = open("/proc/self/ns/mnt", O_RDONLY | O_CLOEXEC); |
| if (fd < 0) { |
| PLOG(ERROR) << "Cannot open fd for current mount namespace"; |
| } |
| return fd; |
| } |
| |
| static std::string GetMountNamespaceId() { |
| std::string ret; |
| if (!android::base::Readlink("/proc/self/ns/mnt", &ret)) { |
| PLOG(ERROR) << "Failed to read namespace ID"; |
| return ""; |
| } |
| return ret; |
| } |
| |
| static bool IsApexUpdatable() { |
| static bool updatable = android::sysprop::ApexProperties::updatable().value_or(false); |
| return updatable; |
| } |
| |
| static Result<void> MountDir(const std::string& path, const std::string& mount_path) { |
| if (int ret = mkdir(mount_path.c_str(), 0755); ret != 0 && errno != EEXIST) { |
| return ErrnoError() << "Could not create mount point " << mount_path; |
| } |
| if (mount(path.c_str(), mount_path.c_str(), nullptr, MS_BIND, nullptr) != 0) { |
| return ErrnoError() << "Could not bind mount " << path << " to " << mount_path; |
| } |
| return {}; |
| } |
| |
| static Result<std::string> GetApexName(const std::string& apex_dir) { |
| const std::string manifest_path = apex_dir + "/apex_manifest.pb"; |
| std::string content; |
| if (!android::base::ReadFileToString(manifest_path, &content)) { |
| return Error() << "Failed to read manifest file: " << manifest_path; |
| } |
| apex::proto::ApexManifest manifest; |
| if (!manifest.ParseFromString(content)) { |
| return Error() << "Can't parse manifest file: " << manifest_path; |
| } |
| return manifest.name(); |
| } |
| |
| static Result<void> ActivateFlattenedApexesFrom(const std::string& from_dir, |
| const std::string& to_dir) { |
| std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(from_dir.c_str()), closedir); |
| if (!dir) { |
| return {}; |
| } |
| dirent* entry; |
| while ((entry = readdir(dir.get())) != nullptr) { |
| if (entry->d_name[0] == '.') continue; |
| if (entry->d_type == DT_DIR) { |
| const std::string apex_path = from_dir + "/" + entry->d_name; |
| const auto apex_name = GetApexName(apex_path); |
| if (!apex_name.ok()) { |
| LOG(ERROR) << apex_path << " is not an APEX directory: " << apex_name.error(); |
| continue; |
| } |
| const std::string mount_path = to_dir + "/" + (*apex_name); |
| if (auto result = MountDir(apex_path, mount_path); !result.ok()) { |
| return result; |
| } |
| } |
| } |
| return {}; |
| } |
| |
| static bool ActivateFlattenedApexesIfPossible() { |
| if (IsRecoveryMode() || IsApexUpdatable()) { |
| return true; |
| } |
| |
| const std::string kApexTop = "/apex"; |
| const std::vector<std::string> kBuiltinDirsForApexes = { |
| "/system/apex", |
| "/system_ext/apex", |
| "/product/apex", |
| "/vendor/apex", |
| }; |
| |
| for (const auto& dir : kBuiltinDirsForApexes) { |
| if (auto result = ActivateFlattenedApexesFrom(dir, kApexTop); !result.ok()) { |
| LOG(ERROR) << result.error(); |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| static Result<void> MountLinkerConfigForDefaultNamespace() { |
| // No need to mount linkerconfig for default mount namespace if the path does not exist (which |
| // would mean it is already mounted) |
| if (access("/linkerconfig/default", 0) != 0) { |
| return {}; |
| } |
| |
| if (mount("/linkerconfig/default", "/linkerconfig", nullptr, MS_BIND | MS_REC, nullptr) != 0) { |
| return ErrnoError() << "Failed to mount linker configuration for default mount namespace."; |
| } |
| |
| return {}; |
| } |
| |
| static android::base::unique_fd bootstrap_ns_fd; |
| static android::base::unique_fd default_ns_fd; |
| |
| static std::string bootstrap_ns_id; |
| static std::string default_ns_id; |
| |
| } // namespace |
| |
| bool SetupMountNamespaces() { |
| // Set the propagation type of / as shared so that any mounting event (e.g. |
| // /data) is by default visible to all processes. When private mounting is |
| // needed for /foo/bar, then we will make /foo/bar as a mount point (by |
| // bind-mounting by to itself) and set the propagation type of the mount |
| // point to private. |
| if (!MakeShared("/", true /*recursive*/)) return false; |
| |
| // /apex is a private mountpoint to give different sets of APEXes for |
| // the bootstrap and default mount namespaces. The processes running with |
| // the bootstrap namespace get APEXes from the read-only partition. |
| if (!(MakePrivate("/apex"))) return false; |
| |
| // /linkerconfig is a private mountpoint to give a different linker configuration |
| // based on the mount namespace. Subdirectory will be bind-mounted based on current mount |
| // namespace |
| if (!(MakePrivate("/linkerconfig"))) return false; |
| |
| // The two mount namespaces present challenges for scoped storage, because |
| // vold, which is responsible for most of the mounting, lives in the |
| // bootstrap mount namespace, whereas most other daemons and all apps live |
| // in the default namespace. Scoped storage has a need for a |
| // /mnt/installer view that is a slave bind mount of /mnt/user - in other |
| // words, all mounts under /mnt/user should automatically show up under |
| // /mnt/installer. However, additional mounts done under /mnt/installer |
| // should not propagate back to /mnt/user. In a single mount namespace |
| // this is easy to achieve, by simply marking the /mnt/installer a slave |
| // bind mount. Unfortunately, if /mnt/installer is only created and |
| // bind mounted after the two namespaces are created below, we end up |
| // with the following situation: |
| // /mnt/user and /mnt/installer share the same peer group in both the |
| // bootstrap and default namespaces. Marking /mnt/installer slave in either |
| // namespace means that it won't propagate events to the /mnt/installer in |
| // the other namespace, which is still something we require - vold is the |
| // one doing the mounting under /mnt/installer, and those mounts should |
| // show up in the default namespace as well. |
| // |
| // The simplest solution is to do the bind mount before the two namespaces |
| // are created: the effect is that in both namespaces, /mnt/installer is a |
| // slave to the /mnt/user mount, and at the same time /mnt/installer in the |
| // bootstrap namespace shares a peer group with /mnt/installer in the |
| // default namespace. |
| if (!mkdir_recursive("/mnt/user", 0755)) return false; |
| if (!mkdir_recursive("/mnt/installer", 0755)) return false; |
| if (!(BindMount("/mnt/user", "/mnt/installer", true))) return false; |
| // First, make /mnt/installer a slave bind mount |
| if (!(MakeSlave("/mnt/installer"))) return false; |
| // Then, make it shared again - effectively creating a new peer group, that |
| // will be inherited by new mount namespaces. |
| if (!(MakeShared("/mnt/installer"))) return false; |
| |
| bootstrap_ns_fd.reset(OpenMountNamespace()); |
| bootstrap_ns_id = GetMountNamespaceId(); |
| |
| // When APEXes are updatable (e.g. not-flattened), we create separate mount |
| // namespaces for processes that are started before and after the APEX is |
| // activated by apexd. In the namespace for pre-apexd processes, small |
| // number of essential APEXes (e.g. com.android.runtime) are activated. |
| // In the namespace for post-apexd processes, all APEXes are activated. |
| bool success = true; |
| if (IsApexUpdatable() && !IsRecoveryMode()) { |
| // Creating a new namespace by cloning, saving, and switching back to |
| // the original namespace. |
| if (unshare(CLONE_NEWNS) == -1) { |
| PLOG(ERROR) << "Cannot create mount namespace"; |
| return false; |
| } |
| default_ns_fd.reset(OpenMountNamespace()); |
| default_ns_id = GetMountNamespaceId(); |
| |
| if (setns(bootstrap_ns_fd.get(), CLONE_NEWNS) == -1) { |
| PLOG(ERROR) << "Cannot switch back to bootstrap mount namespace"; |
| return false; |
| } |
| } else { |
| // Otherwise, default == bootstrap |
| default_ns_fd.reset(OpenMountNamespace()); |
| default_ns_id = GetMountNamespaceId(); |
| } |
| |
| success &= ActivateFlattenedApexesIfPossible(); |
| |
| LOG(INFO) << "SetupMountNamespaces done"; |
| return success; |
| } |
| |
| bool SwitchToDefaultMountNamespace() { |
| if (IsRecoveryMode()) { |
| // we don't have multiple namespaces in recovery mode |
| return true; |
| } |
| if (default_ns_id != GetMountNamespaceId()) { |
| if (setns(default_ns_fd.get(), CLONE_NEWNS) == -1) { |
| PLOG(ERROR) << "Failed to switch back to the default mount namespace."; |
| return false; |
| } |
| |
| if (auto result = MountLinkerConfigForDefaultNamespace(); !result.ok()) { |
| LOG(ERROR) << result.error(); |
| return false; |
| } |
| } |
| |
| LOG(INFO) << "Switched to default mount namespace"; |
| return true; |
| } |
| |
| bool SwitchToBootstrapMountNamespaceIfNeeded() { |
| if (IsRecoveryMode()) { |
| // we don't have multiple namespaces in recovery mode |
| return true; |
| } |
| if (bootstrap_ns_id != GetMountNamespaceId() && bootstrap_ns_fd.get() != -1 && |
| IsApexUpdatable()) { |
| if (setns(bootstrap_ns_fd.get(), CLONE_NEWNS) == -1) { |
| PLOG(ERROR) << "Failed to switch to bootstrap mount namespace."; |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| } // namespace init |
| } // namespace android |