| /* |
| * 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 "util.h" |
| |
| #ifndef RECOVERY |
| #define ACTIVATE_FLATTENED_APEX 1 |
| #endif |
| |
| #ifdef ACTIVATE_FLATTENED_APEX |
| #include <apex_manifest.pb.h> |
| #include <com_android_apex.h> |
| #include <selinux/android.h> |
| #endif // ACTIVATE_FLATTENED_APEX |
| |
| namespace android { |
| namespace init { |
| namespace { |
| |
| static bool BindMount(const std::string& source, const std::string& mount_point) { |
| if (mount(source.c_str(), mount_point.c_str(), nullptr, MS_BIND | MS_REC, nullptr) == -1) { |
| PLOG(ERROR) << "Failed to bind mount " << source; |
| return false; |
| } |
| return true; |
| } |
| |
| static bool ChangeMount(const std::string& mount_point, unsigned long mountflags) { |
| if (mount(nullptr, mount_point.c_str(), nullptr, mountflags, nullptr) == -1) { |
| PLOG(ERROR) << "Failed to remount " << mount_point << " as " << std::hex << mountflags; |
| 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; |
| } |
| |
| // In case we have two sets of APEXes (non-updatable, updatable), we need two separate mount |
| // namespaces. |
| static bool NeedsTwoMountNamespaces() { |
| if (!IsApexUpdatable()) return false; |
| if (IsRecoveryMode()) return false; |
| // In microdroid, there's only one set of APEXes in built-in directories include block devices. |
| if (IsMicrodroid()) return false; |
| return true; |
| } |
| |
| 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 (!ChangeMount("/", MS_SHARED | MS_REC)) 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 (!(ChangeMount("/apex", MS_PRIVATE))) 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 (!(ChangeMount("/linkerconfig", MS_PRIVATE))) 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. |
| // /mnt/androidwritable is similar to /mnt/installer but serves for |
| // MOUNT_EXTERNAL_ANDROID_WRITABLE apps. |
| if (!mkdir_recursive("/mnt/user", 0755)) return false; |
| if (!mkdir_recursive("/mnt/installer", 0755)) return false; |
| if (!mkdir_recursive("/mnt/androidwritable", 0755)) return false; |
| if (!(BindMount("/mnt/user", "/mnt/installer"))) return false; |
| if (!(BindMount("/mnt/user", "/mnt/androidwritable"))) return false; |
| // First, make /mnt/installer and /mnt/androidwritable a slave bind mount |
| if (!(ChangeMount("/mnt/installer", MS_SLAVE))) return false; |
| if (!(ChangeMount("/mnt/androidwritable", MS_SLAVE))) return false; |
| // Then, make it shared again - effectively creating a new peer group, that |
| // will be inherited by new mount namespaces. |
| if (!(ChangeMount("/mnt/installer", MS_SHARED))) return false; |
| if (!(ChangeMount("/mnt/androidwritable", MS_SHARED))) 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 (NeedsTwoMountNamespaces()) { |
| // 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(); |
| } |
| |
| LOG(INFO) << "SetupMountNamespaces done"; |
| return success; |
| } |
| |
| // Switch the mount namespace of the current process from bootstrap to default OR from default to |
| // bootstrap. If the current mount namespace is neither bootstrap nor default, keep it that way. |
| Result<void> SwitchToMountNamespaceIfNeeded(MountNamespace target_mount_namespace) { |
| if (IsRecoveryMode() || !IsApexUpdatable()) { |
| // we don't have multiple namespaces in recovery mode or if apex is not updatable |
| return {}; |
| } |
| |
| const std::string current_namespace_id = GetMountNamespaceId(); |
| MountNamespace current_mount_namespace; |
| if (current_namespace_id == bootstrap_ns_id) { |
| current_mount_namespace = NS_BOOTSTRAP; |
| } else if (current_namespace_id == default_ns_id) { |
| current_mount_namespace = NS_DEFAULT; |
| } else { |
| // services with `namespace mnt` start in its own mount namespace. So we need to keep it. |
| return {}; |
| } |
| |
| // We're already in the target mount namespace. |
| if (current_mount_namespace == target_mount_namespace) { |
| return {}; |
| } |
| |
| const auto& ns_fd = target_mount_namespace == NS_BOOTSTRAP ? bootstrap_ns_fd : default_ns_fd; |
| const auto& ns_name = target_mount_namespace == NS_BOOTSTRAP ? "bootstrap" : "default"; |
| if (ns_fd.get() != -1) { |
| if (setns(ns_fd.get(), CLONE_NEWNS) == -1) { |
| return ErrnoError() << "Failed to switch to " << ns_name << " mount namespace."; |
| } |
| } |
| return {}; |
| } |
| |
| base::Result<MountNamespace> GetCurrentMountNamespace() { |
| std::string current_namespace_id = GetMountNamespaceId(); |
| if (current_namespace_id == "") { |
| return Error() << "Failed to get current mount namespace ID"; |
| } |
| |
| if (current_namespace_id == bootstrap_ns_id) { |
| return NS_BOOTSTRAP; |
| } else if (current_namespace_id == default_ns_id) { |
| return NS_DEFAULT; |
| } |
| |
| return Error() << "Failed to find current mount namespace"; |
| } |
| |
| } // namespace init |
| } // namespace android |