blob: ec48cde021f4da8ad2577ce8cd00fc107231bbe4 [file] [log] [blame]
/*
* 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;
}
#ifdef ACTIVATE_FLATTENED_APEX
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<apex::proto::ApexManifest> GetApexManifest(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;
}
template <typename Fn>
static Result<void> ActivateFlattenedApexesFrom(const std::string& from_dir,
const std::string& to_dir, Fn on_activate) {
std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(from_dir.c_str()), closedir);
if (!dir) {
return {};
}
dirent* entry;
std::vector<std::string> entries;
while ((entry = readdir(dir.get())) != nullptr) {
if (entry->d_name[0] == '.') continue;
if (entry->d_type == DT_DIR) {
entries.push_back(entry->d_name);
}
}
std::sort(entries.begin(), entries.end());
for (const auto& name : entries) {
const std::string apex_path = from_dir + "/" + name;
const auto apex_manifest = GetApexManifest(apex_path);
if (!apex_manifest.ok()) {
LOG(ERROR) << apex_path << " is not an APEX directory: " << apex_manifest.error();
continue;
}
const std::string mount_path = to_dir + "/" + apex_manifest->name();
if (auto result = MountDir(apex_path, mount_path); !result.ok()) {
return result;
}
on_activate(apex_path, *apex_manifest);
}
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",
};
std::vector<com::android::apex::ApexInfo> apex_infos;
auto on_activate = [&](const std::string& apex_path,
const apex::proto::ApexManifest& apex_manifest) {
apex_infos.emplace_back(apex_manifest.name(), apex_path, apex_path, apex_manifest.version(),
apex_manifest.versionname(), /*isFactory=*/true, /*isActive=*/true);
};
for (const auto& dir : kBuiltinDirsForApexes) {
if (auto result = ActivateFlattenedApexesFrom(dir, kApexTop, on_activate); !result.ok()) {
LOG(ERROR) << result.error();
return false;
}
}
std::ostringstream oss;
com::android::apex::ApexInfoList apex_info_list(apex_infos);
com::android::apex::write(oss, apex_info_list);
const std::string kApexInfoList = kApexTop + "/apex-info-list.xml";
if (!android::base::WriteStringToFile(oss.str(), kApexInfoList)) {
PLOG(ERROR) << "Failed to write " << kApexInfoList;
return false;
}
if (selinux_android_restorecon(kApexInfoList.c_str(), 0) != 0) {
PLOG(ERROR) << "selinux_android_restorecon(" << kApexInfoList << ") failed";
}
return true;
}
#endif // ACTIVATE_FLATTENED_APEX
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 (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();
}
#ifdef ACTIVATE_FLATTENED_APEX
success &= ActivateFlattenedApexesIfPossible();
#endif
LOG(INFO) << "SetupMountNamespaces done";
return success;
}
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 auto& ns_id = target_mount_namespace == NS_BOOTSTRAP ? bootstrap_ns_id : default_ns_id;
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_id != GetMountNamespaceId() && ns_fd.get() != -1) {
if (setns(ns_fd.get(), CLONE_NEWNS) == -1) {
return ErrnoError() << "Failed to switch to " << ns_name << " mount namespace.";
}
}
return {};
}
} // namespace init
} // namespace android