init/mount_namespace.cpp - platform/system/core - Git at Google

 /*
  * 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;
     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_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
	/*
	* 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;
	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_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