317 lines
11 KiB
C++
317 lines
11 KiB
C++
/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "service_utils.h"
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#include <fcntl.h>
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#include <grp.h>
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#include <sys/mount.h>
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#include <sys/prctl.h>
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#include <sys/wait.h>
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#include <unistd.h>
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#include <android-base/file.h>
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#include <android-base/logging.h>
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#include <android-base/properties.h>
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#include <android-base/stringprintf.h>
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#include <android-base/strings.h>
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#include <cutils/android_get_control_file.h>
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#include <cutils/sockets.h>
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#include <processgroup/processgroup.h>
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#include "mount_namespace.h"
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#include "util.h"
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using android::base::GetProperty;
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using android::base::StartsWith;
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using android::base::StringPrintf;
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using android::base::unique_fd;
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using android::base::WriteStringToFile;
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namespace android {
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namespace init {
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namespace {
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Result<void> EnterNamespace(int nstype, const char* path) {
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auto fd = unique_fd{open(path, O_RDONLY | O_CLOEXEC)};
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if (fd == -1) {
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return ErrnoError() << "Could not open namespace at " << path;
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}
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if (setns(fd, nstype) == -1) {
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return ErrnoError() << "Could not setns() namespace at " << path;
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}
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return {};
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}
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Result<void> SetUpMountNamespace(bool remount_proc, bool remount_sys) {
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constexpr unsigned int kSafeFlags = MS_NODEV | MS_NOEXEC | MS_NOSUID;
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// Recursively remount / as slave like zygote does so unmounting and mounting /proc
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// doesn't interfere with the parent namespace's /proc mount. This will also
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// prevent any other mounts/unmounts initiated by the service from interfering
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// with the parent namespace but will still allow mount events from the parent
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// namespace to propagate to the child.
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if (mount("rootfs", "/", nullptr, (MS_SLAVE | MS_REC), nullptr) == -1) {
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return ErrnoError() << "Could not remount(/) recursively as slave";
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}
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// umount() then mount() /proc and/or /sys
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// Note that it is not sufficient to mount with MS_REMOUNT.
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if (remount_proc) {
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if (umount("/proc") == -1) {
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return ErrnoError() << "Could not umount(/proc)";
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}
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if (mount("", "/proc", "proc", kSafeFlags, "") == -1) {
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return ErrnoError() << "Could not mount(/proc)";
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}
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}
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if (remount_sys) {
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if (umount2("/sys", MNT_DETACH) == -1) {
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return ErrnoError() << "Could not umount(/sys)";
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}
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if (mount("", "/sys", "sysfs", kSafeFlags, "") == -1) {
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return ErrnoError() << "Could not mount(/sys)";
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}
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}
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return {};
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}
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Result<void> SetUpPidNamespace(const char* name) {
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if (prctl(PR_SET_NAME, name) == -1) {
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return ErrnoError() << "Could not set name";
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}
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pid_t child_pid = fork();
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if (child_pid == -1) {
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return ErrnoError() << "Could not fork init inside the PID namespace";
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}
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if (child_pid > 0) {
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// So that we exit with the right status.
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static int init_exitstatus = 0;
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signal(SIGTERM, [](int) { _exit(init_exitstatus); });
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pid_t waited_pid;
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int status;
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while ((waited_pid = wait(&status)) > 0) {
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// This loop will end when there are no processes left inside the
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// PID namespace or when the init process inside the PID namespace
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// gets a signal.
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if (waited_pid == child_pid) {
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init_exitstatus = status;
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}
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}
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if (!WIFEXITED(init_exitstatus)) {
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_exit(EXIT_FAILURE);
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}
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_exit(WEXITSTATUS(init_exitstatus));
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}
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return {};
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}
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void SetupStdio(bool stdio_to_kmsg) {
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auto fd = unique_fd{open("/dev/null", O_RDWR | O_CLOEXEC)};
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dup2(fd, STDIN_FILENO);
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if (stdio_to_kmsg) {
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fd.reset(open("/dev/kmsg_debug", O_WRONLY | O_CLOEXEC));
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if (fd == -1) fd.reset(open("/dev/null", O_WRONLY | O_CLOEXEC));
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}
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dup2(fd, STDOUT_FILENO);
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dup2(fd, STDERR_FILENO);
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}
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void OpenConsole(const std::string& console) {
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auto fd = unique_fd{open(console.c_str(), O_RDWR | O_CLOEXEC)};
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if (fd == -1) fd.reset(open("/dev/null", O_RDWR | O_CLOEXEC));
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ioctl(fd, TIOCSCTTY, 0);
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dup2(fd, 0);
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dup2(fd, 1);
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dup2(fd, 2);
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}
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} // namespace
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void Descriptor::Publish() const {
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auto published_name = name_;
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for (auto& c : published_name) {
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c = isalnum(c) ? c : '_';
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}
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int fd = fd_.get();
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// For safety, the FD is created as CLOEXEC, so that must be removed before publishing.
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auto fd_flags = fcntl(fd, F_GETFD);
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fd_flags &= ~FD_CLOEXEC;
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if (fcntl(fd, F_SETFD, fd_flags) != 0) {
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PLOG(ERROR) << "Failed to remove CLOEXEC from '" << published_name << "'";
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}
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std::string val = std::to_string(fd);
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setenv(published_name.c_str(), val.c_str(), 1);
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}
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Result<Descriptor> SocketDescriptor::Create(const std::string& global_context) const {
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const auto& socket_context = context.empty() ? global_context : context;
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auto result = CreateSocket(name, type | SOCK_CLOEXEC, passcred, perm, uid, gid, socket_context);
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if (!result.ok()) {
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return result.error();
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}
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return Descriptor(ANDROID_SOCKET_ENV_PREFIX + name, unique_fd(*result));
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}
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Result<Descriptor> FileDescriptor::Create() const {
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int flags = (type == "r") ? O_RDONLY : (type == "w") ? O_WRONLY : O_RDWR;
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// Make sure we do not block on open (eg: devices can chose to block on carrier detect). Our
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// intention is never to delay launch of a service for such a condition. The service can
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// perform its own blocking on carrier detect.
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unique_fd fd(TEMP_FAILURE_RETRY(open(name.c_str(), flags | O_NONBLOCK | O_CLOEXEC)));
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if (fd < 0) {
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return ErrnoError() << "Failed to open file '" << name << "'";
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}
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// Fixup as we set O_NONBLOCK for open, the intent for fd is to block reads.
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fcntl(fd, F_SETFL, flags);
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LOG(INFO) << "Opened file '" << name << "', flags " << flags;
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return Descriptor(ANDROID_FILE_ENV_PREFIX + name, std::move(fd));
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}
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Result<void> EnterNamespaces(const NamespaceInfo& info, const std::string& name, bool pre_apexd) {
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for (const auto& [nstype, path] : info.namespaces_to_enter) {
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if (auto result = EnterNamespace(nstype, path.c_str()); !result.ok()) {
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return result;
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}
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}
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#if defined(__ANDROID__)
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if (pre_apexd) {
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if (!SwitchToBootstrapMountNamespaceIfNeeded()) {
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return Error() << "could not enter into the bootstrap mount namespace";
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}
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}
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#endif
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if (info.flags & CLONE_NEWNS) {
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bool remount_proc = info.flags & CLONE_NEWPID;
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bool remount_sys =
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std::any_of(info.namespaces_to_enter.begin(), info.namespaces_to_enter.end(),
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[](const auto& entry) { return entry.first == CLONE_NEWNET; });
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if (auto result = SetUpMountNamespace(remount_proc, remount_sys); !result.ok()) {
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return result;
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}
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}
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if (info.flags & CLONE_NEWPID) {
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// This will fork again to run an init process inside the PID namespace.
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if (auto result = SetUpPidNamespace(name.c_str()); !result.ok()) {
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return result;
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}
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}
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return {};
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}
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Result<void> SetProcessAttributes(const ProcessAttributes& attr) {
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if (attr.ioprio_class != IoSchedClass_NONE) {
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if (android_set_ioprio(getpid(), attr.ioprio_class, attr.ioprio_pri)) {
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PLOG(ERROR) << "failed to set pid " << getpid() << " ioprio=" << attr.ioprio_class
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<< "," << attr.ioprio_pri;
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}
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}
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if (!attr.console.empty()) {
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setsid();
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OpenConsole(attr.console);
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} else {
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if (setpgid(0, getpid()) == -1) {
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return ErrnoError() << "setpgid failed";
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}
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SetupStdio(attr.stdio_to_kmsg);
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}
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for (const auto& rlimit : attr.rlimits) {
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if (setrlimit(rlimit.first, &rlimit.second) == -1) {
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return ErrnoErrorf("setrlimit({}, {{rlim_cur={}, rlim_max={}}}) failed", rlimit.first,
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rlimit.second.rlim_cur, rlimit.second.rlim_max);
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}
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}
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if (attr.gid) {
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if (setgid(attr.gid) != 0) {
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return ErrnoError() << "setgid failed";
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}
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}
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if (setgroups(attr.supp_gids.size(), const_cast<gid_t*>(&attr.supp_gids[0])) != 0) {
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return ErrnoError() << "setgroups failed";
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}
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if (attr.uid) {
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if (setuid(attr.uid) != 0) {
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return ErrnoError() << "setuid failed";
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}
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}
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if (attr.priority != 0) {
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if (setpriority(PRIO_PROCESS, 0, attr.priority) != 0) {
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return ErrnoError() << "setpriority failed";
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}
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}
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return {};
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}
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Result<void> WritePidToFiles(std::vector<std::string>* files) {
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// See if there were "writepid" instructions to write to files under cpuset path.
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std::string cpuset_path;
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if (CgroupGetControllerPath("cpuset", &cpuset_path)) {
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auto cpuset_predicate = [&cpuset_path](const std::string& path) {
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return StartsWith(path, cpuset_path + "/");
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};
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auto iter = std::find_if(files->begin(), files->end(), cpuset_predicate);
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if (iter == files->end()) {
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// There were no "writepid" instructions for cpusets, check if the system default
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// cpuset is specified to be used for the process.
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std::string default_cpuset = GetProperty("ro.cpuset.default", "");
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if (!default_cpuset.empty()) {
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// Make sure the cpuset name starts and ends with '/'.
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// A single '/' means the 'root' cpuset.
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if (default_cpuset.front() != '/') {
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default_cpuset.insert(0, 1, '/');
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}
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if (default_cpuset.back() != '/') {
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default_cpuset.push_back('/');
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}
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files->push_back(
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StringPrintf("%s%stasks", cpuset_path.c_str(), default_cpuset.c_str()));
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}
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}
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} else {
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LOG(ERROR) << "cpuset cgroup controller is not mounted!";
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}
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std::string pid_str = std::to_string(getpid());
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for (const auto& file : *files) {
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if (!WriteStringToFile(pid_str, file)) {
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return ErrnoError() << "couldn't write " << pid_str << " to " << file;
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}
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}
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return {};
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}
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} // namespace init
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} // namespace android
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