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platform_system_core/libprocessgroup/task_profiles.cpp
Riddle Hsu a6abd821d5 Allow to drop existing fd cache of cgroup path 
A process can give up the permission to set cgroup. If we still
keep the fd that was cached before losing the permission, when
the process sets scheduling group, it will write to the cached
fd without checking if is accessible and lead to sepolicy denied.

Bug: 123043091
Test: Build and boot.
Test: A new process from zygote set cgroup and drop fd cache, and
      then specializes to app domain. There is no sepolicy denied
      when the process creates new thread.
      (android::thread_data_t::trampoline)

Change-Id: I285ee91424ea965ea9c670fc0f6662948e3e2ce5
2019-06-18 15:53:53 +08:00

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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.
*/
//#define LOG_NDEBUG 0
#define LOG_TAG "libprocessgroup"
#include <fcntl.h>
#include <task_profiles.h>
#include <string>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/stringprintf.h>
#include <android-base/threads.h>
#include <cutils/android_filesystem_config.h>
#include <json/reader.h>
#include <json/value.h>
// To avoid issues in sdk_mac build
#if defined(__ANDROID__)
#include <sys/prctl.h>
#endif
using android::base::GetThreadId;
using android::base::StringPrintf;
using android::base::unique_fd;
using android::base::WriteStringToFile;
#define TASK_PROFILE_DB_FILE "/etc/task_profiles.json"
#define TASK_PROFILE_DB_VENDOR_FILE "/vendor/etc/task_profiles.json"
bool ProfileAttribute::GetPathForTask(int tid, std::string* path) const {
std::string subgroup;
if (!controller()->GetTaskGroup(tid, &subgroup)) {
return false;
}
if (path == nullptr) {
return true;
}
if (subgroup.empty()) {
*path = StringPrintf("%s/%s", controller()->path(), file_name_.c_str());
} else {
*path = StringPrintf("%s/%s/%s", controller()->path(), subgroup.c_str(),
file_name_.c_str());
}
return true;
}
bool SetClampsAction::ExecuteForProcess(uid_t, pid_t) const {
// TODO: add support when kernel supports util_clamp
LOG(WARNING) << "SetClampsAction::ExecuteForProcess is not supported";
return false;
}
bool SetClampsAction::ExecuteForTask(int) const {
// TODO: add support when kernel supports util_clamp
LOG(WARNING) << "SetClampsAction::ExecuteForTask is not supported";
return false;
}
// To avoid issues in sdk_mac build
#if defined(__ANDROID__)
bool SetTimerSlackAction::IsTimerSlackSupported(int tid) {
auto file = StringPrintf("/proc/%d/timerslack_ns", tid);
return (access(file.c_str(), W_OK) == 0);
}
bool SetTimerSlackAction::ExecuteForTask(int tid) const {
static bool sys_supports_timerslack = IsTimerSlackSupported(tid);
// v4.6+ kernels support the /proc/<tid>/timerslack_ns interface.
// TODO: once we've backported this, log if the open(2) fails.
if (sys_supports_timerslack) {
auto file = StringPrintf("/proc/%d/timerslack_ns", tid);
if (!WriteStringToFile(std::to_string(slack_), file)) {
if (errno == ENOENT) {
// This happens when process is already dead
return true;
}
PLOG(ERROR) << "set_timerslack_ns write failed";
}
}
// TODO: Remove when /proc/<tid>/timerslack_ns interface is backported.
if (tid == 0 || tid == GetThreadId()) {
if (prctl(PR_SET_TIMERSLACK, slack_) == -1) {
PLOG(ERROR) << "set_timerslack_ns prctl failed";
}
}
return true;
}
#endif
bool SetAttributeAction::ExecuteForProcess(uid_t, pid_t pid) const {
return ExecuteForTask(pid);
}
bool SetAttributeAction::ExecuteForTask(int tid) const {
std::string path;
if (!attribute_->GetPathForTask(tid, &path)) {
LOG(ERROR) << "Failed to find cgroup for tid " << tid;
return false;
}
if (!WriteStringToFile(value_, path)) {
PLOG(ERROR) << "Failed to write '" << value_ << "' to " << path;
return false;
}
return true;
}
bool SetCgroupAction::IsAppDependentPath(const std::string& path) {
return path.find("<uid>", 0) != std::string::npos || path.find("<pid>", 0) != std::string::npos;
}
SetCgroupAction::SetCgroupAction(const CgroupController& c, const std::string& p)
: controller_(c), path_(p) {
// file descriptors for app-dependent paths can't be cached
if (IsAppDependentPath(path_)) {
// file descriptor is not cached
fd_.reset(FDS_APP_DEPENDENT);
return;
}
// file descriptor can be cached later on request
fd_.reset(FDS_NOT_CACHED);
}
void SetCgroupAction::EnableResourceCaching() {
std::lock_guard<std::mutex> lock(fd_mutex_);
if (fd_ != FDS_NOT_CACHED) {
return;
}
std::string tasks_path = controller_.GetTasksFilePath(path_);
if (access(tasks_path.c_str(), W_OK) != 0) {
// file is not accessible
fd_.reset(FDS_INACCESSIBLE);
return;
}
unique_fd fd(TEMP_FAILURE_RETRY(open(tasks_path.c_str(), O_WRONLY | O_CLOEXEC)));
if (fd < 0) {
PLOG(ERROR) << "Failed to cache fd '" << tasks_path << "'";
fd_.reset(FDS_INACCESSIBLE);
return;
}
fd_ = std::move(fd);
}
void SetCgroupAction::DropResourceCaching() {
std::lock_guard<std::mutex> lock(fd_mutex_);
if (fd_ == FDS_NOT_CACHED) {
return;
}
fd_.reset(FDS_NOT_CACHED);
}
bool SetCgroupAction::AddTidToCgroup(int tid, int fd) {
if (tid <= 0) {
return true;
}
std::string value = std::to_string(tid);
if (TEMP_FAILURE_RETRY(write(fd, value.c_str(), value.length())) < 0) {
// If the thread is in the process of exiting, don't flag an error
if (errno != ESRCH) {
PLOG(ERROR) << "AddTidToCgroup failed to write '" << value << "'; fd=" << fd;
return false;
}
}
return true;
}
bool SetCgroupAction::ExecuteForProcess(uid_t uid, pid_t pid) const {
std::lock_guard<std::mutex> lock(fd_mutex_);
if (IsFdValid()) {
// fd is cached, reuse it
if (!AddTidToCgroup(pid, fd_)) {
LOG(ERROR) << "Failed to add task into cgroup";
return false;
}
return true;
}
if (fd_ == FDS_INACCESSIBLE) {
// no permissions to access the file, ignore
return true;
}
// this is app-dependent path and fd is not cached or cached fd can't be used
std::string procs_path = controller()->GetProcsFilePath(path_, uid, pid);
unique_fd tmp_fd(TEMP_FAILURE_RETRY(open(procs_path.c_str(), O_WRONLY | O_CLOEXEC)));
if (tmp_fd < 0) {
PLOG(WARNING) << "Failed to open " << procs_path;
return false;
}
if (!AddTidToCgroup(pid, tmp_fd)) {
LOG(ERROR) << "Failed to add task into cgroup";
return false;
}
return true;
}
bool SetCgroupAction::ExecuteForTask(int tid) const {
std::lock_guard<std::mutex> lock(fd_mutex_);
if (IsFdValid()) {
// fd is cached, reuse it
if (!AddTidToCgroup(tid, fd_)) {
LOG(ERROR) << "Failed to add task into cgroup";
return false;
}
return true;
}
if (fd_ == FDS_INACCESSIBLE) {
// no permissions to access the file, ignore
return true;
}
if (fd_ == FDS_APP_DEPENDENT) {
// application-dependent path can't be used with tid
PLOG(ERROR) << "Application profile can't be applied to a thread";
return false;
}
// fd was not cached because cached fd can't be used
std::string tasks_path = controller()->GetTasksFilePath(path_);
unique_fd tmp_fd(TEMP_FAILURE_RETRY(open(tasks_path.c_str(), O_WRONLY | O_CLOEXEC)));
if (tmp_fd < 0) {
PLOG(WARNING) << "Failed to open " << tasks_path << ": " << strerror(errno);
return false;
}
if (!AddTidToCgroup(tid, tmp_fd)) {
LOG(ERROR) << "Failed to add task into cgroup";
return false;
}
return true;
}
bool TaskProfile::ExecuteForProcess(uid_t uid, pid_t pid) const {
for (const auto& element : elements_) {
if (!element->ExecuteForProcess(uid, pid)) {
return false;
}
}
return true;
}
bool TaskProfile::ExecuteForTask(int tid) const {
if (tid == 0) {
tid = GetThreadId();
}
for (const auto& element : elements_) {
if (!element->ExecuteForTask(tid)) {
return false;
}
}
return true;
}
void TaskProfile::EnableResourceCaching() {
if (res_cached_) {
return;
}
for (auto& element : elements_) {
element->EnableResourceCaching();
}
res_cached_ = true;
}
void TaskProfile::DropResourceCaching() {
if (!res_cached_) {
return;
}
for (auto& element : elements_) {
element->DropResourceCaching();
}
res_cached_ = false;
}
void TaskProfiles::DropResourceCaching() const {
for (auto& iter : profiles_) {
iter.second->DropResourceCaching();
}
}
TaskProfiles& TaskProfiles::GetInstance() {
// Deliberately leak this object to avoid a race between destruction on
// process exit and concurrent access from another thread.
static auto* instance = new TaskProfiles;
return *instance;
}
TaskProfiles::TaskProfiles() {
// load system task profiles
if (!Load(CgroupMap::GetInstance(), TASK_PROFILE_DB_FILE)) {
LOG(ERROR) << "Loading " << TASK_PROFILE_DB_FILE << " for [" << getpid() << "] failed";
}
// load vendor task profiles if the file exists
if (!access(TASK_PROFILE_DB_VENDOR_FILE, F_OK) &&
!Load(CgroupMap::GetInstance(), TASK_PROFILE_DB_VENDOR_FILE)) {
LOG(ERROR) << "Loading " << TASK_PROFILE_DB_VENDOR_FILE << " for [" << getpid()
<< "] failed";
}
}
bool TaskProfiles::Load(const CgroupMap& cg_map, const std::string& file_name) {
std::string json_doc;
if (!android::base::ReadFileToString(file_name, &json_doc)) {
LOG(ERROR) << "Failed to read task profiles from " << file_name;
return false;
}
Json::Reader reader;
Json::Value root;
if (!reader.parse(json_doc, root)) {
LOG(ERROR) << "Failed to parse task profiles: " << reader.getFormattedErrorMessages();
return false;
}
const Json::Value& attr = root["Attributes"];
for (Json::Value::ArrayIndex i = 0; i < attr.size(); ++i) {
std::string name = attr[i]["Name"].asString();
std::string controller_name = attr[i]["Controller"].asString();
std::string file_attr = attr[i]["File"].asString();
if (attributes_.find(name) == attributes_.end()) {
auto controller = cg_map.FindController(controller_name);
if (controller.HasValue()) {
attributes_[name] = std::make_unique<ProfileAttribute>(controller, file_attr);
} else {
LOG(WARNING) << "Controller " << controller_name << " is not found";
}
} else {
LOG(WARNING) << "Attribute " << name << " is already defined";
}
}
std::map<std::string, std::string> params;
const Json::Value& profiles_val = root["Profiles"];
for (Json::Value::ArrayIndex i = 0; i < profiles_val.size(); ++i) {
const Json::Value& profile_val = profiles_val[i];
std::string profile_name = profile_val["Name"].asString();
const Json::Value& actions = profile_val["Actions"];
auto profile = std::make_unique<TaskProfile>();
for (Json::Value::ArrayIndex act_idx = 0; act_idx < actions.size(); ++act_idx) {
const Json::Value& action_val = actions[act_idx];
std::string action_name = action_val["Name"].asString();
const Json::Value& params_val = action_val["Params"];
if (action_name == "JoinCgroup") {
std::string controller_name = params_val["Controller"].asString();
std::string path = params_val["Path"].asString();
auto controller = cg_map.FindController(controller_name);
if (controller.HasValue()) {
profile->Add(std::make_unique<SetCgroupAction>(controller, path));
} else {
LOG(WARNING) << "JoinCgroup: controller " << controller_name << " is not found";
}
} else if (action_name == "SetTimerSlack") {
std::string slack_value = params_val["Slack"].asString();
char* end;
unsigned long slack;
slack = strtoul(slack_value.c_str(), &end, 10);
if (end > slack_value.c_str()) {
profile->Add(std::make_unique<SetTimerSlackAction>(slack));
} else {
LOG(WARNING) << "SetTimerSlack: invalid parameter: " << slack_value;
}
} else if (action_name == "SetAttribute") {
std::string attr_name = params_val["Name"].asString();
std::string attr_value = params_val["Value"].asString();
auto iter = attributes_.find(attr_name);
if (iter != attributes_.end()) {
profile->Add(
std::make_unique<SetAttributeAction>(iter->second.get(), attr_value));
} else {
LOG(WARNING) << "SetAttribute: unknown attribute: " << attr_name;
}
} else if (action_name == "SetClamps") {
std::string boost_value = params_val["Boost"].asString();
std::string clamp_value = params_val["Clamp"].asString();
char* end;
unsigned long boost;
boost = strtoul(boost_value.c_str(), &end, 10);
if (end > boost_value.c_str()) {
unsigned long clamp = strtoul(clamp_value.c_str(), &end, 10);
if (end > clamp_value.c_str()) {
profile->Add(std::make_unique<SetClampsAction>(boost, clamp));
} else {
LOG(WARNING) << "SetClamps: invalid parameter " << clamp_value;
}
} else {
LOG(WARNING) << "SetClamps: invalid parameter: " << boost_value;
}
} else {
LOG(WARNING) << "Unknown profile action: " << action_name;
}
}
profiles_[profile_name] = std::move(profile);
}
return true;
}
TaskProfile* TaskProfiles::GetProfile(const std::string& name) const {
auto iter = profiles_.find(name);
if (iter != profiles_.end()) {
return iter->second.get();
}
return nullptr;
}
const ProfileAttribute* TaskProfiles::GetAttribute(const std::string& name) const {
auto iter = attributes_.find(name);
if (iter != attributes_.end()) {
return iter->second.get();
}
return nullptr;
}
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