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/*
* 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/unique_fd.h>
#include "util.h"
namespace android {
namespace init {
namespace {
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 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 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;
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();
}
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;
}
}
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
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