/*
* Copyright (C) 2008 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.
*/
/*
* Disable optimization of this file if we are compiling with the address
* sanitizer. This is a mitigation for b/122921367 and can be removed once the
* bug is fixed.
*/
#if __has_feature(address_sanitizer)
#pragma clang optimize off
#endif
#define LOG_TAG "Zygote"
#define ATRACE_TAG ATRACE_TAG_DALVIK
#include <async_safe/log.h>
// sys/mount.h has to come before linux/fs.h due to redefinition of MS_RDONLY, MS_BIND, etc
#include <sys/mount.h>
#include <linux/fs.h>
#include <array>
#include <atomic>
#include <functional>
#include <list>
#include <optional>
#include <sstream>
#include <string>
#include <string_view>
#include <android/fdsan.h>
#include <arpa/inet.h>
#include <fcntl.h>
#include <grp.h>
#include <inttypes.h>
#include <link.h>
#include <malloc.h>
#include <mntent.h>
#include <paths.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/capability.h>
#include <sys/cdefs.h>
#include <sys/eventfd.h>
#include <sys/mman.h>
#include <sys/personality.h>
#include <sys/prctl.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/utsname.h>
#include <sys/wait.h>
#include <unistd.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/file.h>
#include <android-base/stringprintf.h>
#include <android-base/strings.h>
#include <android-base/unique_fd.h>
#include <bionic_malloc.h>
#include <cutils/ashmem.h>
#include <cutils/fs.h>
#include <cutils/multiuser.h>
#include <private/android_filesystem_config.h>
#include <utils/String8.h>
#include <utils/Trace.h>
#include <selinux/android.h>
#include <seccomp_policy.h>
#include <stats_event_list.h>
#include <processgroup/processgroup.h>
#include <processgroup/sched_policy.h>
#include "core_jni_helpers.h"
#include <nativehelper/JNIHelp.h>
#include <nativehelper/ScopedLocalRef.h>
#include <nativehelper/ScopedPrimitiveArray.h>
#include <nativehelper/ScopedUtfChars.h>
#include "fd_utils.h"
#include "nativebridge/native_bridge.h"
namespace {
// TODO (chriswailes): Add a function to initialize native Zygote data.
// TODO (chriswailes): Fix mixed indentation style (2 and 4 spaces).
using namespace std::placeholders;
using android::String8;
using android::base::StringAppendF;
using android::base::StringPrintf;
using android::base::WriteStringToFile;
using android::base::GetBoolProperty;
#define CREATE_ERROR(...) StringPrintf("%s:%d: ", __FILE__, __LINE__). \
append(StringPrintf(__VA_ARGS__))
// This type is duplicated in fd_utils.h
typedef const std::function<void(std::string)>& fail_fn_t;
static pid_t gSystemServerPid = 0;
static constexpr const char* kZygoteClassName = "com/android/internal/os/Zygote";
static jclass gZygoteClass;
static jmethodID gCallPostForkSystemServerHooks;
static jmethodID gCallPostForkChildHooks;
static constexpr const char* kZygoteInitClassName = "com/android/internal/os/ZygoteInit";
static jclass gZygoteInitClass;
static jmethodID gCreateSystemServerClassLoader;
static bool gIsSecurityEnforced = true;
/**
* The maximum number of characters (not including a null terminator) that a
* process name may contain.
*/
static constexpr size_t MAX_NAME_LENGTH = 15;
/**
* The prefix string for environmental variables storing socket FDs created by
* init.
*/
static constexpr std::string_view ANDROID_SOCKET_PREFIX("ANDROID_SOCKET_");
/**
* The file descriptor for the Zygote socket opened by init.
*/
static int gZygoteSocketFD = -1;
/**
* The file descriptor for the unspecialized app process (USAP) pool socket opened by init.
*/
static int gUsapPoolSocketFD = -1;
/**
* The number of USAPs currently in this Zygote's pool.
*/
static std::atomic_uint32_t gUsapPoolCount = 0;
/**
* Event file descriptor used to communicate reaped USAPs to the
* ZygoteServer.
*/
static int gUsapPoolEventFD = -1;
/**
* The maximum value that the gUSAPPoolSizeMax variable may take. This value
* is a mirror of ZygoteServer.USAP_POOL_SIZE_MAX_LIMIT
*/
static constexpr int USAP_POOL_SIZE_MAX_LIMIT = 100;
/**
* A helper class containing accounting information for USAPs.
*/
class UsapTableEntry {
public:
struct EntryStorage {
int32_t pid;
int32_t read_pipe_fd;
bool operator!=(const EntryStorage& other) {
return pid != other.pid || read_pipe_fd != other.read_pipe_fd;
}
};
private:
static constexpr EntryStorage INVALID_ENTRY_VALUE = {-1, -1};
std::atomic<EntryStorage> mStorage;
static_assert(decltype(mStorage)::is_always_lock_free);
public:
constexpr UsapTableEntry() : mStorage(INVALID_ENTRY_VALUE) {}
/**
* If the provided PID matches the one stored in this entry, the entry will
* be invalidated and the associated file descriptor will be closed. If the
* PIDs don't match nothing will happen.
*
* @param pid The ID of the process who's entry we want to clear.
* @return True if the entry was cleared by this call; false otherwise
*/
bool ClearForPID(int32_t pid) {
EntryStorage storage = mStorage.load();
if (storage.pid == pid) {
/*
* There are three possible outcomes from this compare-and-exchange:
* 1) It succeeds, in which case we close the FD
* 2) It fails and the new value is INVALID_ENTRY_VALUE, in which case
* the entry has already been cleared.
* 3) It fails and the new value isn't INVALID_ENTRY_VALUE, in which
* case the entry has already been cleared and re-used.
*
* In all three cases the goal of the caller has been met, but only in
* the first case do we need to decrement the pool count.
*/
if (mStorage.compare_exchange_strong(storage, INVALID_ENTRY_VALUE)) {
close(storage.read_pipe_fd);
return true;
} else {
return false;
}
} else {
return false;
}
}
void Clear() {
EntryStorage storage = mStorage.load();
if (storage != INVALID_ENTRY_VALUE) {
close(storage.read_pipe_fd);
mStorage.store(INVALID_ENTRY_VALUE);
}
}
void Invalidate() {
mStorage.store(INVALID_ENTRY_VALUE);
}
/**
* @return A copy of the data stored in this entry.
*/
std::optional<EntryStorage> GetValues() {
EntryStorage storage = mStorage.load();
if (storage != INVALID_ENTRY_VALUE) {
return storage;
} else {
return std::nullopt;
}
}
/**
* Sets the entry to the given values if it is currently invalid.
*
* @param pid The process ID for the new entry.
* @param read_pipe_fd The read end of the USAP control pipe for this
* process.
* @return True if the entry was set; false otherwise.
*/
bool SetIfInvalid(int32_t pid, int32_t read_pipe_fd) {
EntryStorage new_value_storage;
new_value_storage.pid = pid;
new_value_storage.read_pipe_fd = read_pipe_fd;
EntryStorage expected = INVALID_ENTRY_VALUE;
return mStorage.compare_exchange_strong(expected, new_value_storage);
}
};
/**
* A table containing information about the USAPs currently in the pool.
*
* Multiple threads may be attempting to modify the table, either from the
* signal handler or from the ZygoteServer poll loop. Atomic loads/stores in
* the USAPTableEntry class prevent data races during these concurrent
* operations.
*/
static std::array<UsapTableEntry, USAP_POOL_SIZE_MAX_LIMIT> gUsapTable;
/**
* The list of open zygote file descriptors.
*/
static FileDescriptorTable* gOpenFdTable = nullptr;
// Must match values in com.android.internal.os.Zygote.
enum MountExternalKind {
MOUNT_EXTERNAL_NONE = 0,
MOUNT_EXTERNAL_DEFAULT = 1,
MOUNT_EXTERNAL_READ = 2,
MOUNT_EXTERNAL_WRITE = 3,
MOUNT_EXTERNAL_LEGACY = 4,
MOUNT_EXTERNAL_INSTALLER = 5,
MOUNT_EXTERNAL_FULL = 6,
};
// Must match values in com.android.internal.os.Zygote.
enum RuntimeFlags : uint32_t {
DEBUG_ENABLE_JDWP = 1,
PROFILE_FROM_SHELL = 1 << 15,
};
// Forward declaration so we don't have to move the signal handler.
static bool RemoveUsapTableEntry(pid_t usap_pid);
static void RuntimeAbort(JNIEnv* env, int line, const char* msg) {
std::ostringstream oss;
oss << __FILE__ << ":" << line << ": " << msg;
env->FatalError(oss.str().c_str());
}
// This signal handler is for zygote mode, since the zygote must reap its children
static void SigChldHandler(int /*signal_number*/) {
pid_t pid;
int status;
int64_t usaps_removed = 0;
// It's necessary to save and restore the errno during this function.
// Since errno is stored per thread, changing it here modifies the errno
// on the thread on which this signal handler executes. If a signal occurs
// between a call and an errno check, it's possible to get the errno set
// here.
// See b/23572286 for extra information.
int saved_errno = errno;
while ((pid = waitpid(-1, &status, WNOHANG)) > 0) {
// Log process-death status that we care about.
if (WIFEXITED(status)) {
async_safe_format_log(ANDROID_LOG_INFO, LOG_TAG,
"Process %d exited cleanly (%d)", pid, WEXITSTATUS(status));
// Check to see if the PID is in the USAP pool and remove it if it is.
if (RemoveUsapTableEntry(pid)) {
++usaps_removed;
}
} else if (WIFSIGNALED(status)) {
async_safe_format_log(ANDROID_LOG_INFO, LOG_TAG,
"Process %d exited due to signal %d (%s)%s", pid,
WTERMSIG(status), strsignal(WTERMSIG(status)),
WCOREDUMP(status) ? "; core dumped" : "");
// If the process exited due to a signal other than SIGTERM, check to see
// if the PID is in the USAP pool and remove it if it is. If the process
// was closed by the Zygote using SIGTERM then the USAP pool entry will
// have already been removed (see nativeEmptyUsapPool()).
if (WTERMSIG(status) != SIGTERM && RemoveUsapTableEntry(pid)) {
++usaps_removed;
}
}
// If the just-crashed process is the system_server, bring down zygote
// so that it is restarted by init and system server will be restarted
// from there.
if (pid == gSystemServerPid) {
async_safe_format_log(ANDROID_LOG_ERROR, LOG_TAG,
"Exit zygote because system server (pid %d) has terminated", pid);
kill(getpid(), SIGKILL);
}
}
// Note that we shouldn't consider ECHILD an error because
// the secondary zygote might have no children left to wait for.
if (pid < 0 && errno != ECHILD) {
async_safe_format_log(ANDROID_LOG_WARN, LOG_TAG,
"Zygote SIGCHLD error in waitpid: %s", strerror(errno));
}
if (usaps_removed > 0) {
if (TEMP_FAILURE_RETRY(write(gUsapPoolEventFD, &usaps_removed, sizeof(usaps_removed))) == -1) {
// If this write fails something went terribly wrong. We will now kill
// the zygote and let the system bring it back up.
async_safe_format_log(ANDROID_LOG_ERROR, LOG_TAG,
"Zygote failed to write to USAP pool event FD: %s",
strerror(errno));
kill(getpid(), SIGKILL);
}
}
errno = saved_errno;
}
// Configures the SIGCHLD/SIGHUP handlers for the zygote process. This is
// configured very late, because earlier in the runtime we may fork() and
// exec() other processes, and we want to waitpid() for those rather than
// have them be harvested immediately.
//
// Ignore SIGHUP because all processes forked by the zygote are in the same
// process group as the zygote and we don't want to be notified if we become
// an orphaned group and have one or more stopped processes. This is not a
// theoretical concern :
// - we can become an orphaned group if one of our direct descendants forks
// and is subsequently killed before its children.
// - crash_dump routinely STOPs the process it's tracing.
//
// See issues b/71965619 and b/25567761 for further details.
//
// This ends up being called repeatedly before each fork(), but there's
// no real harm in that.
static void SetSignalHandlers() {
struct sigaction sig_chld = {};
sig_chld.sa_handler = SigChldHandler;
if (sigaction(SIGCHLD, &sig_chld, nullptr) < 0) {
ALOGW("Error setting SIGCHLD handler: %s", strerror(errno));
}
struct sigaction sig_hup = {};
sig_hup.sa_handler = SIG_IGN;
if (sigaction(SIGHUP, &sig_hup, nullptr) < 0) {
ALOGW("Error setting SIGHUP handler: %s", strerror(errno));
}
}
// Sets the SIGCHLD handler back to default behavior in zygote children.
static void UnsetChldSignalHandler() {
struct sigaction sa;
memset(&sa, 0, sizeof(sa));
sa.sa_handler = SIG_DFL;
if (sigaction(SIGCHLD, &sa, nullptr) < 0) {
ALOGW("Error unsetting SIGCHLD handler: %s", strerror(errno));
}
}
// Calls POSIX setgroups() using the int[] object as an argument.
// A nullptr argument is tolerated.
static void SetGids(JNIEnv* env, jintArray managed_gids, fail_fn_t fail_fn) {
if (managed_gids == nullptr) {
return;
}
ScopedIntArrayRO gids(env, managed_gids);
if (gids.get() == nullptr) {
fail_fn(CREATE_ERROR("Getting gids int array failed"));
}
if (setgroups(gids.size(), reinterpret_cast<const gid_t*>(&gids[0])) == -1) {
fail_fn(CREATE_ERROR("setgroups failed: %s, gids.size=%zu", strerror(errno), gids.size()));
}
}
// Sets the resource limits via setrlimit(2) for the values in the
// two-dimensional array of integers that's passed in. The second dimension
// contains a tuple of length 3: (resource, rlim_cur, rlim_max). nullptr is
// treated as an empty array.
static void SetRLimits(JNIEnv* env, jobjectArray managed_rlimits, fail_fn_t fail_fn) {
if (managed_rlimits == nullptr) {
return;
}
rlimit rlim;
memset(&rlim, 0, sizeof(rlim));
for (int i = 0; i < env->GetArrayLength(managed_rlimits); ++i) {
ScopedLocalRef<jobject>
managed_rlimit_object(env, env->GetObjectArrayElement(managed_rlimits, i));
ScopedIntArrayRO rlimit_handle(env, reinterpret_cast<jintArray>(managed_rlimit_object.get()));
if (rlimit_handle.size() != 3) {
fail_fn(CREATE_ERROR("rlimits array must have a second dimension of size 3"));
}
rlim.rlim_cur = rlimit_handle[1];
rlim.rlim_max = rlimit_handle[2];
if (setrlimit(rlimit_handle[0], &rlim) == -1) {
fail_fn(CREATE_ERROR("setrlimit(%d, {%ld, %ld}) failed",
rlimit_handle[0], rlim.rlim_cur, rlim.rlim_max));
}
}
}
static void EnableDebugger() {
// To let a non-privileged gdbserver attach to this
// process, we must set our dumpable flag.
if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) == -1) {
ALOGE("prctl(PR_SET_DUMPABLE) failed");
}
// A non-privileged native debugger should be able to attach to the debuggable app, even if Yama
// is enabled (see kernel/Documentation/security/Yama.txt).
if (prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0) == -1) {
// if Yama is off prctl(PR_SET_PTRACER) returns EINVAL - don't log in this
// case since it's expected behaviour.
if (errno != EINVAL) {
ALOGE("prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY) failed");
}
}
// Set the core dump size to zero unless wanted (see also coredump_setup in build/envsetup.sh).
if (!GetBoolProperty("persist.zygote.core_dump", false)) {
// Set the soft limit on core dump size to 0 without changing the hard limit.
rlimit rl;
if (getrlimit(RLIMIT_CORE, &rl) == -1) {
ALOGE("getrlimit(RLIMIT_CORE) failed");
} else {
rl.rlim_cur = 0;
if (setrlimit(RLIMIT_CORE, &rl) == -1) {
ALOGE("setrlimit(RLIMIT_CORE) failed");
}
}
}
}
static void PreApplicationInit() {
// The child process sets this to indicate it's not the zygote.
android_mallopt(M_SET_ZYGOTE_CHILD, nullptr, 0);
// Set the jemalloc decay time to 1.
mallopt(M_DECAY_TIME, 1);
}
static void SetUpSeccompFilter(uid_t uid, bool is_child_zygote) {
if (!gIsSecurityEnforced) {
ALOGI("seccomp disabled by setenforce 0");
return;
}
// Apply system or app filter based on uid.
if (uid >= AID_APP_START) {
if (is_child_zygote) {
set_app_zygote_seccomp_filter();
} else {
set_app_seccomp_filter();
}
} else {
set_system_seccomp_filter();
}
}
static void EnableKeepCapabilities(fail_fn_t fail_fn) {
if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) == -1) {
fail_fn(CREATE_ERROR("prctl(PR_SET_KEEPCAPS) failed: %s", strerror(errno)));
}
}
static void DropCapabilitiesBoundingSet(fail_fn_t fail_fn) {
for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {;
if (prctl(PR_CAPBSET_DROP, i, 0, 0, 0) == -1) {
if (errno == EINVAL) {
ALOGE("prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify "
"your kernel is compiled with file capabilities support");
} else {
fail_fn(CREATE_ERROR("prctl(PR_CAPBSET_DROP, %d) failed: %s", i, strerror(errno)));
}
}
}
}
static void SetInheritable(uint64_t inheritable, fail_fn_t fail_fn) {
__user_cap_header_struct capheader;
memset(&capheader, 0, sizeof(capheader));
capheader.version = _LINUX_CAPABILITY_VERSION_3;
capheader.pid = 0;
__user_cap_data_struct capdata[2];
if (capget(&capheader, &capdata[0]) == -1) {
fail_fn(CREATE_ERROR("capget failed: %s", strerror(errno)));
}
capdata[0].inheritable = inheritable;
capdata[1].inheritable = inheritable >> 32;
if (capset(&capheader, &capdata[0]) == -1) {
fail_fn(CREATE_ERROR("capset(inh=%" PRIx64 ") failed: %s", inheritable, strerror(errno)));
}
}
static void SetCapabilities(uint64_t permitted, uint64_t effective, uint64_t inheritable,
fail_fn_t fail_fn) {
__user_cap_header_struct capheader;
memset(&capheader, 0, sizeof(capheader));
capheader.version = _LINUX_CAPABILITY_VERSION_3;
capheader.pid = 0;
__user_cap_data_struct capdata[2];
memset(&capdata, 0, sizeof(capdata));
capdata[0].effective = effective;
capdata[1].effective = effective >> 32;
capdata[0].permitted = permitted;
capdata[1].permitted = permitted >> 32;
capdata[0].inheritable = inheritable;
capdata[1].inheritable = inheritable >> 32;
if (capset(&capheader, &capdata[0]) == -1) {
fail_fn(CREATE_ERROR("capset(perm=%" PRIx64 ", eff=%" PRIx64 ", inh=%" PRIx64 ") "
"failed: %s", permitted, effective, inheritable, strerror(errno)));
}
}
static void SetSchedulerPolicy(fail_fn_t fail_fn) {
errno = -set_sched_policy(0, SP_DEFAULT);
if (errno != 0) {
fail_fn(CREATE_ERROR("set_sched_policy(0, SP_DEFAULT) failed: %s", strerror(errno)));
}
}
static int UnmountTree(const char* path) {
ATRACE_CALL();
size_t path_len = strlen(path);
FILE* fp = setmntent("/proc/mounts", "r");
if (fp == nullptr) {
ALOGE("Error opening /proc/mounts: %s", strerror(errno));
return -errno;
}
// Some volumes can be stacked on each other, so force unmount in
// reverse order to give us the best chance of success.
std::list<std::string> to_unmount;
mntent* mentry;
while ((mentry = getmntent(fp)) != nullptr) {
if (strncmp(mentry->mnt_dir, path, path_len) == 0) {
to_unmount.push_front(std::string(mentry->mnt_dir));
}
}
endmntent(fp);
for (const auto& path : to_unmount) {
if (umount2(path.c_str(), MNT_DETACH)) {
ALOGW("Failed to unmount %s: %s", path.c_str(), strerror(errno));
}
}
return 0;
}
// Create a private mount namespace and bind mount appropriate emulated
// storage for the given user.
static void MountEmulatedStorage(uid_t uid, jint mount_mode,
bool force_mount_namespace,
fail_fn_t fail_fn) {
// See storage config details at http://source.android.com/tech/storage/
ATRACE_CALL();
String8 storage_source;
if (mount_mode == MOUNT_EXTERNAL_DEFAULT) {
storage_source = "/mnt/runtime/default";
} else if (mount_mode == MOUNT_EXTERNAL_READ) {
storage_source = "/mnt/runtime/read";
} else if (mount_mode == MOUNT_EXTERNAL_WRITE
|| mount_mode == MOUNT_EXTERNAL_LEGACY
|| mount_mode == MOUNT_EXTERNAL_INSTALLER) {
storage_source = "/mnt/runtime/write";
} else if (mount_mode == MOUNT_EXTERNAL_FULL) {
storage_source = "/mnt/runtime/full";
} else if (mount_mode == MOUNT_EXTERNAL_NONE && !force_mount_namespace) {
// Sane default of no storage visible
return;
}
// Create a second private mount namespace for our process
if (unshare(CLONE_NEWNS) == -1) {
fail_fn(CREATE_ERROR("Failed to unshare(): %s", strerror(errno)));
}
// Handle force_mount_namespace with MOUNT_EXTERNAL_NONE.
if (mount_mode == MOUNT_EXTERNAL_NONE) {
return;
}
if (TEMP_FAILURE_RETRY(mount(storage_source.string(), "/storage", nullptr,
MS_BIND | MS_REC | MS_SLAVE, nullptr)) == -1) {
fail_fn(CREATE_ERROR("Failed to mount %s to /storage: %s",
storage_source.string(),
strerror(errno)));
}
// Mount user-specific symlink helper into place
userid_t user_id = multiuser_get_user_id(uid);
const String8 user_source(String8::format("/mnt/user/%d", user_id));
if (fs_prepare_dir(user_source.string(), 0751, 0, 0) == -1) {
fail_fn(CREATE_ERROR("fs_prepare_dir failed on %s",
user_source.string()));
}
if (TEMP_FAILURE_RETRY(mount(user_source.string(), "/storage/self",
nullptr, MS_BIND, nullptr)) == -1) {
fail_fn(CREATE_ERROR("Failed to mount %s to /storage/self: %s",
user_source.string(), strerror(errno)));
}
}
static bool NeedsNoRandomizeWorkaround() {
#if !defined(__arm__)
return false;
#else
int major;
int minor;
struct utsname uts;
if (uname(&uts) == -1) {
return false;
}
if (sscanf(uts.release, "%d.%d", &major, &minor) != 2) {
return false;
}
// Kernels before 3.4.* need the workaround.
return (major < 3) || ((major == 3) && (minor < 4));
#endif
}
// Utility to close down the Zygote socket file descriptors while
// the child is still running as root with Zygote's privileges. Each
// descriptor (if any) is closed via dup3(), replacing it with a valid
// (open) descriptor to /dev/null.
static void DetachDescriptors(JNIEnv* env,
const std::vector<int>& fds_to_close,
fail_fn_t fail_fn) {
if (fds_to_close.size() > 0) {
android::base::unique_fd devnull_fd(open("/dev/null", O_RDWR | O_CLOEXEC));
if (devnull_fd == -1) {
fail_fn(std::string("Failed to open /dev/null: ").append(strerror(errno)));
}
for (int fd : fds_to_close) {
ALOGV("Switching descriptor %d to /dev/null", fd);
if (dup3(devnull_fd, fd, O_CLOEXEC) == -1) {
fail_fn(StringPrintf("Failed dup3() on descriptor %d: %s", fd, strerror(errno)));
}
}
}
}
void SetThreadName(const std::string& thread_name) {
bool hasAt = false;
bool hasDot = false;
for (const char str_el : thread_name) {
if (str_el == '.') {
hasDot = true;
} else if (str_el == '@') {
hasAt = true;
}
}
const char* name_start_ptr = thread_name.c_str();
if (thread_name.length() >= MAX_NAME_LENGTH && !hasAt && hasDot) {
name_start_ptr += thread_name.length() - MAX_NAME_LENGTH;
}
// pthread_setname_np fails rather than truncating long strings.
char buf[16]; // MAX_TASK_COMM_LEN=16 is hard-coded into bionic
strlcpy(buf, name_start_ptr, sizeof(buf) - 1);
errno = pthread_setname_np(pthread_self(), buf);
if (errno != 0) {
ALOGW("Unable to set the name of current thread to '%s': %s", buf, strerror(errno));
}
// Update base::logging default tag.
android::base::SetDefaultTag(buf);
}
/**
* A failure function used to report fatal errors to the managed runtime. This
* function is often curried with the process name information and then passed
* to called functions.
*
* @param env Managed runtime environment
* @param process_name A native representation of the process name
* @param managed_process_name A managed representation of the process name
* @param msg The error message to be reported
*/
[[noreturn]]
static void ZygoteFailure(JNIEnv* env,
const char* process_name,
jstring managed_process_name,
const std::string& msg) {
std::unique_ptr<ScopedUtfChars> scoped_managed_process_name_ptr = nullptr;
if (managed_process_name != nullptr) {
scoped_managed_process_name_ptr.reset(new ScopedUtfChars(env, managed_process_name));
if (scoped_managed_process_name_ptr->c_str() != nullptr) {
process_name = scoped_managed_process_name_ptr->c_str();
}
}
const std::string& error_msg =
(process_name == nullptr) ? msg : StringPrintf("(%s) %s", process_name, msg.c_str());
env->FatalError(error_msg.c_str());
__builtin_unreachable();
}
/**
* A helper method for converting managed strings to native strings. A fatal
* error is generated if a problem is encountered in extracting a non-null
* string.
*
* @param env Managed runtime environment
* @param process_name A native representation of the process name
* @param managed_process_name A managed representation of the process name
* @param managed_string The managed string to extract
*
* @return An empty option if the managed string is null. A optional-wrapped
* string otherwise.
*/
static std::optional<std::string> ExtractJString(JNIEnv* env,
const char* process_name,
jstring managed_process_name,
jstring managed_string) {
if (managed_string == nullptr) {
return std::nullopt;
} else {
ScopedUtfChars scoped_string_chars(env, managed_string);
if (scoped_string_chars.c_str() != nullptr) {
return std::optional<std::string>(scoped_string_chars.c_str());
} else {
ZygoteFailure(env, process_name, managed_process_name, "Failed to extract JString.");
}
}
}
/**
* A helper method for converting managed string arrays to native vectors. A
* fatal error is generated if a problem is encountered in extracting a non-null array.
*
* @param env Managed runtime environment
* @param process_name A native representation of the process name
* @param managed_process_name A managed representation of the process name
* @param managed_array The managed integer array to extract
*
* @return An empty option if the managed array is null. A optional-wrapped
* vector otherwise.
*/
static std::optional<std::vector<int>> ExtractJIntArray(JNIEnv* env,
const char* process_name,
jstring managed_process_name,
jintArray managed_array) {
if (managed_array == nullptr) {
return std::nullopt;
} else {
ScopedIntArrayRO managed_array_handle(env, managed_array);
if (managed_array_handle.get() != nullptr) {
std::vector<int> native_array;
native_array.reserve(managed_array_handle.size());
for (size_t array_index = 0; array_index < managed_array_handle.size(); ++array_index) {
native_array.push_back(managed_array_handle[array_index]);
}
return std::move(native_array);
} else {
ZygoteFailure(env, process_name, managed_process_name, "Failed to extract JIntArray.");
}
}
}
/**
* A utility function for blocking signals.
*
* @param signum Signal number to block
* @param fail_fn Fatal error reporting function
*
* @see ZygoteFailure
*/
static void BlockSignal(int signum, fail_fn_t fail_fn) {
sigset_t sigs;
sigemptyset(&sigs);
sigaddset(&sigs, signum);
if (sigprocmask(SIG_BLOCK, &sigs, nullptr) == -1) {
fail_fn(CREATE_ERROR("Failed to block signal %s: %s", strsignal(signum), strerror(errno)));
}
}
/**
* A utility function for unblocking signals.
*
* @param signum Signal number to unblock
* @param fail_fn Fatal error reporting function
*
* @see ZygoteFailure
*/
static void UnblockSignal(int signum, fail_fn_t fail_fn) {
sigset_t sigs;
sigemptyset(&sigs);
sigaddset(&sigs, signum);
if (sigprocmask(SIG_UNBLOCK, &sigs, nullptr) == -1) {
fail_fn(CREATE_ERROR("Failed to un-block signal %s: %s", strsignal(signum), strerror(errno)));
}
}
static void ClearUsapTable() {
for (UsapTableEntry& entry : gUsapTable) {
entry.Clear();
}
gUsapPoolCount = 0;
}
// Utility routine to fork a process from the zygote.
static pid_t ForkCommon(JNIEnv* env, bool is_system_server,
const std::vector<int>& fds_to_close,
const std::vector<int>& fds_to_ignore) {
SetSignalHandlers();
// Curry a failure function.
auto fail_fn = std::bind(ZygoteFailure, env, is_system_server ? "system_server" : "zygote",
nullptr, _1);
// Temporarily block SIGCHLD during forks. The SIGCHLD handler might
// log, which would result in the logging FDs we close being reopened.
// This would cause failures because the FDs are not whitelisted.
//
// Note that the zygote process is single threaded at this point.
BlockSignal(SIGCHLD, fail_fn);
// Close any logging related FDs before we start evaluating the list of
// file descriptors.
__android_log_close();
stats_log_close();
// If this is the first fork for this zygote, create the open FD table. If
// it isn't, we just need to check whether the list of open files has changed
// (and it shouldn't in the normal case).
if (gOpenFdTable == nullptr) {
gOpenFdTable = FileDescriptorTable::Create(fds_to_ignore, fail_fn);
} else {
gOpenFdTable->Restat(fds_to_ignore, fail_fn);
}
android_fdsan_error_level fdsan_error_level = android_fdsan_get_error_level();
pid_t pid = fork();
if (pid == 0) {
// The child process.
PreApplicationInit();
// Clean up any descriptors which must be closed immediately
DetachDescriptors(env, fds_to_close, fail_fn);
// Invalidate the entries in the USAP table.
ClearUsapTable();
// Re-open all remaining open file descriptors so that they aren't shared
// with the zygote across a fork.
gOpenFdTable->ReopenOrDetach(fail_fn);
// Turn fdsan back on.
android_fdsan_set_error_level(fdsan_error_level);
} else {
ALOGD("Forked child process %d", pid);
}
// We blocked SIGCHLD prior to a fork, we unblock it here.
UnblockSignal(SIGCHLD, fail_fn);
return pid;
}
// Utility routine to specialize a zygote child process.
static void SpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray gids,
jint runtime_flags, jobjectArray rlimits,
jlong permitted_capabilities, jlong effective_capabilities,
jint mount_external, jstring managed_se_info,
jstring managed_nice_name, bool is_system_server,
bool is_child_zygote, jstring managed_instruction_set,
jstring managed_app_data_dir) {
const char* process_name = is_system_server ? "system_server" : "zygote";
auto fail_fn = std::bind(ZygoteFailure, env, process_name, managed_nice_name, _1);
auto extract_fn = std::bind(ExtractJString, env, process_name, managed_nice_name, _1);
auto se_info = extract_fn(managed_se_info);
auto nice_name = extract_fn(managed_nice_name);
auto instruction_set = extract_fn(managed_instruction_set);
auto app_data_dir = extract_fn(managed_app_data_dir);
// Keep capabilities across UID change, unless we're staying root.
if (uid != 0) {
EnableKeepCapabilities(fail_fn);
}
SetInheritable(permitted_capabilities, fail_fn);
DropCapabilitiesBoundingSet(fail_fn);
bool use_native_bridge = !is_system_server &&
instruction_set.has_value() &&
android::NativeBridgeAvailable() &&
android::NeedsNativeBridge(instruction_set.value().c_str());
if (use_native_bridge && !app_data_dir.has_value()) {
// The app_data_dir variable should never be empty if we need to use a
// native bridge. In general, app_data_dir will never be empty for normal
// applications. It can only happen in special cases (for isolated
// processes which are not associated with any app). These are launched by
// the framework and should not be emulated anyway.
use_native_bridge = false;
ALOGW("Native bridge will not be used because managed_app_data_dir == nullptr.");
}
MountEmulatedStorage(uid, mount_external, use_native_bridge, fail_fn);
// If this zygote isn't root, it won't be able to create a process group,
// since the directory is owned by root.
if (!is_system_server && getuid() == 0) {
const int rc = createProcessGroup(uid, getpid());
if (rc == -EROFS) {
ALOGW("createProcessGroup failed, kernel missing CONFIG_CGROUP_CPUACCT?");
} else if (rc != 0) {
ALOGE("createProcessGroup(%d, %d) failed: %s", uid, /* pid= */ 0, strerror(-rc));
}
}
SetGids(env, gids, fail_fn);
SetRLimits(env, rlimits, fail_fn);
if (use_native_bridge) {
// Due to the logic behind use_native_bridge we know that both app_data_dir
// and instruction_set contain values.
android::PreInitializeNativeBridge(app_data_dir.value().c_str(),
instruction_set.value().c_str());
}
if (setresgid(gid, gid, gid) == -1) {
fail_fn(CREATE_ERROR("setresgid(%d) failed: %s", gid, strerror(errno)));
}
// Must be called when the new process still has CAP_SYS_ADMIN, in this case,
// before changing uid from 0, which clears capabilities. The other
// alternative is to call prctl(PR_SET_NO_NEW_PRIVS, 1) afterward, but that
// breaks SELinux domain transition (see b/71859146). As the result,
// privileged syscalls used below still need to be accessible in app process.
SetUpSeccompFilter(uid, is_child_zygote);
if (setresuid(uid, uid, uid) == -1) {
fail_fn(CREATE_ERROR("setresuid(%d) failed: %s", uid, strerror(errno)));
}
// The "dumpable" flag of a process, which controls core dump generation, is
// overwritten by the value in /proc/sys/fs/suid_dumpable when the effective
// user or group ID changes. See proc(5) for possible values. In most cases,
// the value is 0, so core dumps are disabled for zygote children. However,
// when running in a Chrome OS container, the value is already set to 2,
// which allows the external crash reporter to collect all core dumps. Since
// only system crashes are interested, core dump is disabled for app
// processes. This also ensures compliance with CTS.
int dumpable = prctl(PR_GET_DUMPABLE);
if (dumpable == -1) {
ALOGE("prctl(PR_GET_DUMPABLE) failed: %s", strerror(errno));
RuntimeAbort(env, __LINE__, "prctl(PR_GET_DUMPABLE) failed");
}
if (dumpable == 2 && uid >= AID_APP) {
if (prctl(PR_SET_DUMPABLE, 0, 0, 0, 0) == -1) {
ALOGE("prctl(PR_SET_DUMPABLE, 0) failed: %s", strerror(errno));
RuntimeAbort(env, __LINE__, "prctl(PR_SET_DUMPABLE, 0) failed");
}
}
// Set process properties to enable debugging if required.
if ((runtime_flags & RuntimeFlags::DEBUG_ENABLE_JDWP) != 0) {
EnableDebugger();
}
if ((runtime_flags & RuntimeFlags::PROFILE_FROM_SHELL) != 0) {
// simpleperf needs the process to be dumpable to profile it.
if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) == -1) {
ALOGE("prctl(PR_SET_DUMPABLE) failed: %s", strerror(errno));
RuntimeAbort(env, __LINE__, "prctl(PR_SET_DUMPABLE, 1) failed");
}
}
if (NeedsNoRandomizeWorkaround()) {
// Work around ARM kernel ASLR lossage (http://b/5817320).
int old_personality = personality(0xffffffff);
int new_personality = personality(old_personality | ADDR_NO_RANDOMIZE);
if (new_personality == -1) {
ALOGW("personality(%d) failed: %s", new_personality, strerror(errno));
}
}
SetCapabilities(permitted_capabilities, effective_capabilities, permitted_capabilities, fail_fn);
SetSchedulerPolicy(fail_fn);
__android_log_close();
stats_log_close();
const char* se_info_ptr = se_info.has_value() ? se_info.value().c_str() : nullptr;
const char* nice_name_ptr = nice_name.has_value() ? nice_name.value().c_str() : nullptr;
if (selinux_android_setcontext(uid, is_system_server, se_info_ptr, nice_name_ptr) == -1) {
fail_fn(CREATE_ERROR("selinux_android_setcontext(%d, %d, \"%s\", \"%s\") failed",
uid, is_system_server, se_info_ptr, nice_name_ptr));
}
// Make it easier to debug audit logs by setting the main thread's name to the
// nice name rather than "app_process".
if (nice_name.has_value()) {
SetThreadName(nice_name.value());
} else if (is_system_server) {
SetThreadName("system_server");
}
// Unset the SIGCHLD handler, but keep ignoring SIGHUP (rationale in SetSignalHandlers).
UnsetChldSignalHandler();
if (is_system_server) {
env->CallStaticVoidMethod(gZygoteClass, gCallPostForkSystemServerHooks);
if (env->ExceptionCheck()) {
fail_fn("Error calling post fork system server hooks.");
}
// Prefetch the classloader for the system server. This is done early to
// allow a tie-down of the proper system server selinux domain.
env->CallStaticVoidMethod(gZygoteInitClass, gCreateSystemServerClassLoader);
if (env->ExceptionCheck()) {
// Be robust here. The Java code will attempt to create the classloader
// at a later point (but may not have rights to use AoT artifacts).
env->ExceptionClear();
}
// TODO(oth): Remove hardcoded label here (b/117874058).
static const char* kSystemServerLabel = "u:r:system_server:s0";
if (selinux_android_setcon(kSystemServerLabel) != 0) {
fail_fn(CREATE_ERROR("selinux_android_setcon(%s)", kSystemServerLabel));
}
}
env->CallStaticVoidMethod(gZygoteClass, gCallPostForkChildHooks, runtime_flags,
is_system_server, is_child_zygote, managed_instruction_set);
if (env->ExceptionCheck()) {
fail_fn("Error calling post fork hooks.");
}
}
static uint64_t GetEffectiveCapabilityMask(JNIEnv* env) {
__user_cap_header_struct capheader;
memset(&capheader, 0, sizeof(capheader));
capheader.version = _LINUX_CAPABILITY_VERSION_3;
capheader.pid = 0;
__user_cap_data_struct capdata[2];
if (capget(&capheader, &capdata[0]) == -1) {
ALOGE("capget failed: %s", strerror(errno));
RuntimeAbort(env, __LINE__, "capget failed");
}
return capdata[0].effective | (static_cast<uint64_t>(capdata[1].effective) << 32);
}
static jlong CalculateCapabilities(JNIEnv* env, jint uid, jint gid, jintArray gids,
bool is_child_zygote) {
jlong capabilities = 0;
/*
* Grant the following capabilities to the Bluetooth user:
* - CAP_WAKE_ALARM
* - CAP_NET_ADMIN
* - CAP_NET_RAW
* - CAP_NET_BIND_SERVICE (for DHCP client functionality)
* - CAP_SYS_NICE (for setting RT priority for audio-related threads)
*/
if (multiuser_get_app_id(uid) == AID_BLUETOOTH) {
capabilities |= (1LL << CAP_WAKE_ALARM);
capabilities |= (1LL << CAP_NET_ADMIN);
capabilities |= (1LL << CAP_NET_RAW);
capabilities |= (1LL << CAP_NET_BIND_SERVICE);
capabilities |= (1LL << CAP_SYS_NICE);
}
if (multiuser_get_app_id(uid) == AID_NETWORK_STACK) {
capabilities |= (1LL << CAP_NET_ADMIN);
capabilities |= (1LL << CAP_NET_BROADCAST);
capabilities |= (1LL << CAP_NET_BIND_SERVICE);
capabilities |= (1LL << CAP_NET_RAW);
}
/*
* Grant CAP_BLOCK_SUSPEND to processes that belong to GID "wakelock"
*/
bool gid_wakelock_found = false;
if (gid == AID_WAKELOCK) {
gid_wakelock_found = true;
} else if (gids != nullptr) {
jsize gids_num = env->GetArrayLength(gids);
ScopedIntArrayRO native_gid_proxy(env, gids);
if (native_gid_proxy.get() == nullptr) {
RuntimeAbort(env, __LINE__, "Bad gids array");
}
for (int gids_index = 0; gids_index < gids_num; ++gids_index) {
if (native_gid_proxy[gids_index] == AID_WAKELOCK) {
gid_wakelock_found = true;
break;
}
}
}
if (gid_wakelock_found) {
capabilities |= (1LL << CAP_BLOCK_SUSPEND);
}
/*
* Grant child Zygote processes the following capabilities:
* - CAP_SETUID (change UID of child processes)
* - CAP_SETGID (change GID of child processes)
* - CAP_SETPCAP (change capabilities of child processes)
*/
if (is_child_zygote) {
capabilities |= (1LL << CAP_SETUID);
capabilities |= (1LL << CAP_SETGID);
capabilities |= (1LL << CAP_SETPCAP);
}
/*
* Containers run without some capabilities, so drop any caps that are not
* available.
*/
return capabilities & GetEffectiveCapabilityMask(env);
}
/**
* Adds the given information about a newly created unspecialized app
* processes to the Zygote's USAP table.
*
* @param usap_pid Process ID of the newly created USAP
* @param read_pipe_fd File descriptor for the read end of the USAP
* reporting pipe. Used in the ZygoteServer poll loop to track USAP
* specialization.
*/
static void AddUsapTableEntry(pid_t usap_pid, int read_pipe_fd) {
static int sUsapTableInsertIndex = 0;
int search_index = sUsapTableInsertIndex;
do {
if (gUsapTable[search_index].SetIfInvalid(usap_pid, read_pipe_fd)) {
// Start our next search right after where we finished this one.
sUsapTableInsertIndex = (search_index + 1) % gUsapTable.size();
return;
}
search_index = (search_index + 1) % gUsapTable.size();
} while (search_index != sUsapTableInsertIndex);
// Much like money in the banana stand, there should always be an entry
// in the USAP table.
__builtin_unreachable();
}
/**
* Invalidates the entry in the USAPTable corresponding to the provided
* process ID if it is present. If an entry was removed the USAP pool
* count is decremented.
*
* @param usap_pid Process ID of the USAP entry to invalidate
* @return True if an entry was invalidated; false otherwise
*/
static bool RemoveUsapTableEntry(pid_t usap_pid) {
for (UsapTableEntry& entry : gUsapTable) {
if (entry.ClearForPID(usap_pid)) {
--gUsapPoolCount;
return true;
}
}
return false;
}
/**
* @return A vector of the read pipe FDs for each of the active USAPs.
*/
std::vector<int> MakeUsapPipeReadFDVector() {
std::vector<int> fd_vec;
fd_vec.reserve(gUsapTable.size());
for (UsapTableEntry& entry : gUsapTable) {
auto entry_values = entry.GetValues();
if (entry_values.has_value()) {
fd_vec.push_back(entry_values.value().read_pipe_fd);
}
}
return fd_vec;
}
static void UnmountStorageOnInit(JNIEnv* env) {
// Zygote process unmount root storage space initially before every child processes are forked.
// Every forked child processes (include SystemServer) only mount their own root storage space
// and no need unmount storage operation in MountEmulatedStorage method.
// Zygote process does not utilize root storage spaces and unshares its mount namespace below.
// See storage config details at http://source.android.com/tech/storage/
// Create private mount namespace shared by all children
if (unshare(CLONE_NEWNS) == -1) {
RuntimeAbort(env, __LINE__, "Failed to unshare()");
return;
}
// Mark rootfs as being a slave so that changes from default
// namespace only flow into our children.
if (mount("rootfs", "/", nullptr, (MS_SLAVE | MS_REC), nullptr) == -1) {
RuntimeAbort(env, __LINE__, "Failed to mount() rootfs as MS_SLAVE");
return;
}
// Create a staging tmpfs that is shared by our children; they will
// bind mount storage into their respective private namespaces, which
// are isolated from each other.
const char* target_base = getenv("EMULATED_STORAGE_TARGET");
if (target_base != nullptr) {
#define STRINGIFY_UID(x) __STRING(x)
if (mount("tmpfs", target_base, "tmpfs", MS_NOSUID | MS_NODEV,
"uid=0,gid=" STRINGIFY_UID(AID_SDCARD_R) ",mode=0751") == -1) {
ALOGE("Failed to mount tmpfs to %s", target_base);
RuntimeAbort(env, __LINE__, "Failed to mount tmpfs");
return;
}
#undef STRINGIFY_UID
}
UnmountTree("/storage");
}
} // anonymous namespace
namespace android {
static void com_android_internal_os_Zygote_nativePreApplicationInit(JNIEnv*, jclass) {
PreApplicationInit();
}
static jint com_android_internal_os_Zygote_nativeForkAndSpecialize(
JNIEnv* env, jclass, jint uid, jint gid, jintArray gids,
jint runtime_flags, jobjectArray rlimits,
jint mount_external, jstring se_info, jstring nice_name,
jintArray managed_fds_to_close, jintArray managed_fds_to_ignore, jboolean is_child_zygote,
jstring instruction_set, jstring app_data_dir) {
jlong capabilities = CalculateCapabilities(env, uid, gid, gids, is_child_zygote);
if (UNLIKELY(managed_fds_to_close == nullptr)) {
ZygoteFailure(env, "zygote", nice_name, "Zygote received a null fds_to_close vector.");
}
std::vector<int> fds_to_close =
ExtractJIntArray(env, "zygote", nice_name, managed_fds_to_close).value();
std::vector<int> fds_to_ignore =
ExtractJIntArray(env, "zygote", nice_name, managed_fds_to_ignore)
.value_or(std::vector<int>());
std::vector<int> usap_pipes = MakeUsapPipeReadFDVector();
fds_to_close.insert(fds_to_close.end(), usap_pipes.begin(), usap_pipes.end());
fds_to_ignore.insert(fds_to_ignore.end(), usap_pipes.begin(), usap_pipes.end());
fds_to_close.push_back(gUsapPoolSocketFD);
if (gUsapPoolEventFD != -1) {
fds_to_close.push_back(gUsapPoolEventFD);
fds_to_ignore.push_back(gUsapPoolEventFD);
}
pid_t pid = ForkCommon(env, false, fds_to_close, fds_to_ignore);
if (pid == 0) {
SpecializeCommon(env, uid, gid, gids, runtime_flags, rlimits,
capabilities, capabilities,
mount_external, se_info, nice_name, false,
is_child_zygote == JNI_TRUE, instruction_set, app_data_dir);
}
return pid;
}
static jint com_android_internal_os_Zygote_nativeForkSystemServer(
JNIEnv* env, jclass, uid_t uid, gid_t gid, jintArray gids,
jint runtime_flags, jobjectArray rlimits, jlong permitted_capabilities,
jlong effective_capabilities) {
std::vector<int> fds_to_close(MakeUsapPipeReadFDVector()),
fds_to_ignore(fds_to_close);
fds_to_close.push_back(gUsapPoolSocketFD);
if (gUsapPoolEventFD != -1) {
fds_to_close.push_back(gUsapPoolEventFD);
fds_to_ignore.push_back(gUsapPoolEventFD);
}
pid_t pid = ForkCommon(env, true,
fds_to_close,
fds_to_ignore);
if (pid == 0) {
SpecializeCommon(env, uid, gid, gids, runtime_flags, rlimits,
permitted_capabilities, effective_capabilities,
MOUNT_EXTERNAL_DEFAULT, nullptr, nullptr, true,
false, nullptr, nullptr);
} else if (pid > 0) {
// The zygote process checks whether the child process has died or not.
ALOGI("System server process %d has been created", pid);
gSystemServerPid = pid;
// There is a slight window that the system server process has crashed
// but it went unnoticed because we haven't published its pid yet. So
// we recheck here just to make sure that all is well.
int status;
if (waitpid(pid, &status, WNOHANG) == pid) {
ALOGE("System server process %d has died. Restarting Zygote!", pid);
RuntimeAbort(env, __LINE__, "System server process has died. Restarting Zygote!");
}
if (UsePerAppMemcg()) {
// Assign system_server to the correct memory cgroup.
// Not all devices mount memcg so check if it is mounted first
// to avoid unnecessarily printing errors and denials in the logs.
if (!SetTaskProfiles(pid, std::vector<std::string>{"SystemMemoryProcess"})) {
ALOGE("couldn't add process %d into system memcg group", pid);
}
}
}
return pid;
}
/**
* A JNI function that forks an unspecialized app process from the Zygote while
* ensuring proper file descriptor hygiene.
*
* @param env Managed runtime environment
* @param read_pipe_fd The read FD for the USAP reporting pipe. Manually closed by blastlas
* in managed code.
* @param write_pipe_fd The write FD for the USAP reporting pipe. Manually closed by the
* zygote in managed code.
* @param managed_session_socket_fds A list of anonymous session sockets that must be ignored by
* the FD hygiene code and automatically "closed" in the new USAP.
* @return
*/
static jint com_android_internal_os_Zygote_nativeForkUsap(JNIEnv* env,
jclass,
jint read_pipe_fd,
jint write_pipe_fd,
jintArray managed_session_socket_fds) {
std::vector<int> fds_to_close(MakeUsapPipeReadFDVector()),
fds_to_ignore(fds_to_close);
std::vector<int> session_socket_fds =
ExtractJIntArray(env, "USAP", nullptr, managed_session_socket_fds)
.value_or(std::vector<int>());
// The USAP Pool Event FD is created during the initialization of the
// USAP pool and should always be valid here.
fds_to_close.push_back(gZygoteSocketFD);
fds_to_close.push_back(gUsapPoolEventFD);
fds_to_close.insert(fds_to_close.end(), session_socket_fds.begin(), session_socket_fds.end());
fds_to_ignore.push_back(gZygoteSocketFD);
fds_to_ignore.push_back(gUsapPoolSocketFD);
fds_to_ignore.push_back(gUsapPoolEventFD);
fds_to_ignore.push_back(read_pipe_fd);
fds_to_ignore.push_back(write_pipe_fd);
fds_to_ignore.insert(fds_to_ignore.end(), session_socket_fds.begin(), session_socket_fds.end());
pid_t usap_pid = ForkCommon(env, /* is_system_server= */ false, fds_to_close, fds_to_ignore);
if (usap_pid != 0) {
++gUsapPoolCount;
AddUsapTableEntry(usap_pid, read_pipe_fd);
}
return usap_pid;
}
static void com_android_internal_os_Zygote_nativeAllowFileAcrossFork(
JNIEnv* env, jclass, jstring path) {
ScopedUtfChars path_native(env, path);
const char* path_cstr = path_native.c_str();
if (!path_cstr) {
RuntimeAbort(env, __LINE__, "path_cstr == nullptr");
}
FileDescriptorWhitelist::Get()->Allow(path_cstr);
}
static void com_android_internal_os_Zygote_nativeInstallSeccompUidGidFilter(
JNIEnv* env, jclass, jint uidGidMin, jint uidGidMax) {
if (!gIsSecurityEnforced) {
ALOGI("seccomp disabled by setenforce 0");
return;
}
bool installed = install_setuidgid_seccomp_filter(uidGidMin, uidGidMax);
if (!installed) {
RuntimeAbort(env, __LINE__, "Could not install setuid/setgid seccomp filter.");
}
}
/**
* Called from an unspecialized app process to specialize the process for a
* given application.
*
* @param env Managed runtime environment
* @param uid User ID of the new application
* @param gid Group ID of the new application
* @param gids Extra groups that the process belongs to
* @param runtime_flags Flags for changing the behavior of the managed runtime
* @param rlimits Resource limits
* @param mount_external The mode (read/write/normal) that external storage will be mounted with
* @param se_info SELinux policy information
* @param nice_name New name for this process
* @param is_child_zygote If the process is to become a WebViewZygote
* @param instruction_set The instruction set expected/requested by the new application
* @param app_data_dir Path to the application's data directory
*/
static void com_android_internal_os_Zygote_nativeSpecializeAppProcess(
JNIEnv* env, jclass, jint uid, jint gid, jintArray gids,
jint runtime_flags, jobjectArray rlimits,
jint mount_external, jstring se_info, jstring nice_name,
jboolean is_child_zygote, jstring instruction_set, jstring app_data_dir) {
jlong capabilities = CalculateCapabilities(env, uid, gid, gids, is_child_zygote);
SpecializeCommon(env, uid, gid, gids, runtime_flags, rlimits,
capabilities, capabilities,
mount_external, se_info, nice_name, false,
is_child_zygote == JNI_TRUE, instruction_set, app_data_dir);
}
/**
* A helper method for fetching socket file descriptors that were opened by init from the
* environment.
*
* @param env Managed runtime environment
* @param is_primary If this process is the primary or secondary Zygote; used to compute the name
* of the environment variable storing the file descriptors.
*/
static void com_android_internal_os_Zygote_nativeInitNativeState(JNIEnv* env, jclass,
jboolean is_primary) {
/*
* Obtain file descriptors created by init from the environment.
*/
std::string android_socket_prefix(ANDROID_SOCKET_PREFIX);
std::string env_var_name = android_socket_prefix + (is_primary ? "zygote" : "zygote_secondary");
char* env_var_val = getenv(env_var_name.c_str());
if (env_var_val != nullptr) {
gZygoteSocketFD = atoi(env_var_val);
ALOGV("Zygote:zygoteSocketFD = %d", gZygoteSocketFD);
} else {
ALOGE("Unable to fetch Zygote socket file descriptor");
}
env_var_name = android_socket_prefix + (is_primary ? "usap_pool_primary" : "usap_pool_secondary");
env_var_val = getenv(env_var_name.c_str());
if (env_var_val != nullptr) {
gUsapPoolSocketFD = atoi(env_var_val);
ALOGV("Zygote:usapPoolSocketFD = %d", gUsapPoolSocketFD);
} else {
ALOGE("Unable to fetch USAP pool socket file descriptor");
}
/*
* Security Initialization
*/
// security_getenforce is not allowed on app process. Initialize and cache
// the value before zygote forks.
gIsSecurityEnforced = security_getenforce();
selinux_android_seapp_context_init();
/*
* Storage Initialization
*/
UnmountStorageOnInit(env);
/*
* Performance Initialization
*/
if (!SetTaskProfiles(0, {})) {
ZygoteFailure(env, "zygote", nullptr, "Zygote SetTaskProfiles failed");
}
/*
* ashmem initialization to avoid dlopen overhead
*/
ashmem_init();
}
/**
* @param env Managed runtime environment
* @return A managed array of raw file descriptors for the read ends of the USAP reporting
* pipes.
*/
static jintArray com_android_internal_os_Zygote_nativeGetUsapPipeFDs(JNIEnv* env, jclass) {
std::vector<int> usap_fds = MakeUsapPipeReadFDVector();
jintArray managed_usap_fds = env->NewIntArray(usap_fds.size());
env->SetIntArrayRegion(managed_usap_fds, 0, usap_fds.size(), usap_fds.data());
return managed_usap_fds;
}
/**
* A JNI wrapper around RemoveUsapTableEntry.
*
* @param env Managed runtime environment
* @param usap_pid Process ID of the USAP entry to invalidate
* @return True if an entry was invalidated; false otherwise.
*/
static jboolean com_android_internal_os_Zygote_nativeRemoveUsapTableEntry(JNIEnv* env, jclass,
jint usap_pid) {
return RemoveUsapTableEntry(usap_pid);
}
/**
* Creates the USAP pool event FD if it doesn't exist and returns it. This is used by the
* ZygoteServer poll loop to know when to re-fill the USAP pool.
*
* @param env Managed runtime environment
* @return A raw event file descriptor used to communicate (from the signal handler) when the
* Zygote receives a SIGCHLD for a USAP
*/
static jint com_android_internal_os_Zygote_nativeGetUsapPoolEventFD(JNIEnv* env, jclass) {
if (gUsapPoolEventFD == -1) {
if ((gUsapPoolEventFD = eventfd(0, 0)) == -1) {
ZygoteFailure(env, "zygote", nullptr, StringPrintf("Unable to create eventfd: %s", strerror(errno)));
}
}
return gUsapPoolEventFD;
}
/**
* @param env Managed runtime environment
* @return The number of USAPs currently in the USAP pool
*/
static jint com_android_internal_os_Zygote_nativeGetUsapPoolCount(JNIEnv* env, jclass) {
return gUsapPoolCount;
}
/**
* Kills all processes currently in the USAP pool and closes their read pipe
* FDs.
*
* @param env Managed runtime environment
*/
static void com_android_internal_os_Zygote_nativeEmptyUsapPool(JNIEnv* env, jclass) {
for (auto& entry : gUsapTable) {
auto entry_storage = entry.GetValues();
if (entry_storage.has_value()) {
kill(entry_storage.value().pid, SIGTERM);
// Clean up the USAP table entry here. This avoids a potential race
// where a newly created USAP might not be able to find a valid table
// entry if signal handler (which would normally do the cleanup) doesn't
// run between now and when the new process is created.
close(entry_storage.value().read_pipe_fd);
// Avoid a second atomic load by invalidating instead of clearing.
entry.Invalidate();
--gUsapPoolCount;
}
}
}
static int disable_execute_only(struct dl_phdr_info *info, size_t size, void *data) {
// Search for any execute-only segments and mark them read+execute.
for (int i = 0; i < info->dlpi_phnum; i++) {
if ((info->dlpi_phdr[i].p_type == PT_LOAD) && (info->dlpi_phdr[i].p_flags == PF_X)) {
mprotect(reinterpret_cast<void*>(info->dlpi_addr + info->dlpi_phdr[i].p_vaddr),
info->dlpi_phdr[i].p_memsz, PROT_READ | PROT_EXEC);
}
}
// Return non-zero to exit dl_iterate_phdr.
return 0;
}
/**
* @param env Managed runtime environment
* @return True if disable was successful.
*/
static jboolean com_android_internal_os_Zygote_nativeDisableExecuteOnly(JNIEnv* env, jclass) {
return dl_iterate_phdr(disable_execute_only, nullptr) == 0;
}
static void com_android_internal_os_Zygote_nativeBlockSigTerm(JNIEnv* env, jclass) {
auto fail_fn = std::bind(ZygoteFailure, env, "usap", nullptr, _1);
BlockSignal(SIGTERM, fail_fn);
}
static void com_android_internal_os_Zygote_nativeUnblockSigTerm(JNIEnv* env, jclass) {
auto fail_fn = std::bind(ZygoteFailure, env, "usap", nullptr, _1);
UnblockSignal(SIGTERM, fail_fn);
}
static const JNINativeMethod gMethods[] = {
{ "nativeForkAndSpecialize",
"(II[II[[IILjava/lang/String;Ljava/lang/String;[I[IZLjava/lang/String;Ljava/lang/String;)I",
(void *) com_android_internal_os_Zygote_nativeForkAndSpecialize },
{ "nativeForkSystemServer", "(II[II[[IJJ)I",
(void *) com_android_internal_os_Zygote_nativeForkSystemServer },
{ "nativeAllowFileAcrossFork", "(Ljava/lang/String;)V",
(void *) com_android_internal_os_Zygote_nativeAllowFileAcrossFork },
{ "nativePreApplicationInit", "()V",
(void *) com_android_internal_os_Zygote_nativePreApplicationInit },
{ "nativeInstallSeccompUidGidFilter", "(II)V",
(void *) com_android_internal_os_Zygote_nativeInstallSeccompUidGidFilter },
{ "nativeForkUsap", "(II[I)I",
(void *) com_android_internal_os_Zygote_nativeForkUsap },
{ "nativeSpecializeAppProcess",
"(II[II[[IILjava/lang/String;Ljava/lang/String;ZLjava/lang/String;Ljava/lang/String;)V",
(void *) com_android_internal_os_Zygote_nativeSpecializeAppProcess },
{ "nativeInitNativeState", "(Z)V",
(void *) com_android_internal_os_Zygote_nativeInitNativeState },
{ "nativeGetUsapPipeFDs", "()[I",
(void *) com_android_internal_os_Zygote_nativeGetUsapPipeFDs },
{ "nativeRemoveUsapTableEntry", "(I)Z",
(void *) com_android_internal_os_Zygote_nativeRemoveUsapTableEntry },
{ "nativeGetUsapPoolEventFD", "()I",
(void *) com_android_internal_os_Zygote_nativeGetUsapPoolEventFD },
{ "nativeGetUsapPoolCount", "()I",
(void *) com_android_internal_os_Zygote_nativeGetUsapPoolCount },
{ "nativeEmptyUsapPool", "()V",
(void *) com_android_internal_os_Zygote_nativeEmptyUsapPool },
{ "nativeDisableExecuteOnly", "()Z",
(void *) com_android_internal_os_Zygote_nativeDisableExecuteOnly },
{ "nativeBlockSigTerm", "()V",
(void* ) com_android_internal_os_Zygote_nativeBlockSigTerm },
{ "nativeUnblockSigTerm", "()V",
(void* ) com_android_internal_os_Zygote_nativeUnblockSigTerm }
};
int register_com_android_internal_os_Zygote(JNIEnv* env) {
gZygoteClass = MakeGlobalRefOrDie(env, FindClassOrDie(env, kZygoteClassName));
gCallPostForkSystemServerHooks = GetStaticMethodIDOrDie(env, gZygoteClass,
"callPostForkSystemServerHooks",
"()V");
gCallPostForkChildHooks = GetStaticMethodIDOrDie(env, gZygoteClass, "callPostForkChildHooks",
"(IZZLjava/lang/String;)V");
gZygoteInitClass = MakeGlobalRefOrDie(env, FindClassOrDie(env, kZygoteInitClassName));
gCreateSystemServerClassLoader = GetStaticMethodIDOrDie(env, gZygoteInitClass,
"createSystemServerClassLoader",
"()V");
RegisterMethodsOrDie(env, "com/android/internal/os/Zygote", gMethods, NELEM(gMethods));
return JNI_OK;
}
} // namespace android