/*
* 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.
*/
#define LOG_TAG "Zygote"
// 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 <list>
#include <sstream>
#include <string>
#include <fcntl.h>
#include <grp.h>
#include <inttypes.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/personality.h>
#include <sys/prctl.h>
#include <sys/resource.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/file.h>
#include <android-base/stringprintf.h>
#include <cutils/fs.h>
#include <cutils/multiuser.h>
#include <cutils/sched_policy.h>
#include <private/android_filesystem_config.h>
#include <utils/String8.h>
#include <selinux/android.h>
#include <seccomp_policy.h>
#include <processgroup/processgroup.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 {
using android::String8;
using android::base::StringPrintf;
using android::base::WriteStringToFile;
#define CREATE_ERROR(...) StringPrintf("%s:%d: ", __FILE__, __LINE__). \
append(StringPrintf(__VA_ARGS__))
static pid_t gSystemServerPid = 0;
static const char kZygoteClassName[] = "com/android/internal/os/Zygote";
static jclass gZygoteClass;
static jmethodID gCallPostForkChildHooks;
static bool g_is_security_enforced = true;
// 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,
};
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;
// 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. In general it is
// not safe to call LOG(...) from a signal handler because of
// possible reentrancy. However, we know a priori that the
// current implementation of LOG() is safe to call from a SIGCHLD
// handler in the zygote process. If the LOG() implementation
// changes its locking strategy or its use of syscalls within the
// lazy-init critical section, its use here may become unsafe.
if (WIFEXITED(status)) {
ALOGI("Process %d exited cleanly (%d)", pid, WEXITSTATUS(status));
} else if (WIFSIGNALED(status)) {
ALOGI("Process %d exited due to signal (%d)", pid, WTERMSIG(status));
if (WCOREDUMP(status)) {
ALOGI("Process %d dumped core.", pid);
}
}
// 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) {
ALOGE("Exit zygote because system server (%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) {
ALOGW("Zygote SIGCHLD error in waitpid: %s", strerror(errno));
}
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, NULL) < 0) {
ALOGW("Error setting SIGCHLD handler: %s", strerror(errno));
}
struct sigaction sig_hup = {};
sig_hup.sa_handler = SIG_IGN;
if (sigaction(SIGHUP, &sig_hup, NULL) < 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, NULL) < 0) {
ALOGW("Error unsetting SIGCHLD handler: %s", strerror(errno));
}
}
// Calls POSIX setgroups() using the int[] object as an argument.
// A NULL argument is tolerated.
static bool SetGids(JNIEnv* env, jintArray javaGids, std::string* error_msg) {
if (javaGids == NULL) {
return true;
}
ScopedIntArrayRO gids(env, javaGids);
if (gids.get() == NULL) {
*error_msg = CREATE_ERROR("Getting gids int array failed");
return false;
}
int rc = setgroups(gids.size(), reinterpret_cast<const gid_t*>(&gids[0]));
if (rc == -1) {
*error_msg = CREATE_ERROR("setgroups failed: %s, gids.size=%zu", strerror(errno), gids.size());
return false;
}
return true;
}
// 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). NULL is
// treated as an empty array.
static bool SetRLimits(JNIEnv* env, jobjectArray javaRlimits, std::string* error_msg) {
if (javaRlimits == NULL) {
return true;
}
rlimit rlim;
memset(&rlim, 0, sizeof(rlim));
for (int i = 0; i < env->GetArrayLength(javaRlimits); ++i) {
ScopedLocalRef<jobject> javaRlimitObject(env, env->GetObjectArrayElement(javaRlimits, i));
ScopedIntArrayRO javaRlimit(env, reinterpret_cast<jintArray>(javaRlimitObject.get()));
if (javaRlimit.size() != 3) {
*error_msg = CREATE_ERROR("rlimits array must have a second dimension of size 3");
return false;
}
rlim.rlim_cur = javaRlimit[1];
rlim.rlim_max = javaRlimit[2];
int rc = setrlimit(javaRlimit[0], &rlim);
if (rc == -1) {
*error_msg = CREATE_ERROR("setrlimit(%d, {%ld, %ld}) failed", javaRlimit[0], rlim.rlim_cur,
rlim.rlim_max);
return false;
}
}
return true;
}
// The debug malloc library needs to know whether it's the zygote or a child.
extern "C" int gMallocLeakZygoteChild;
static void PreApplicationInit() {
// The child process sets this to indicate it's not the zygote.
gMallocLeakZygoteChild = 1;
// Set the jemalloc decay time to 1.
mallopt(M_DECAY_TIME, 1);
}
static void SetUpSeccompFilter(uid_t uid) {
if (!g_is_security_enforced) {
ALOGI("seccomp disabled by setenforce 0");
return;
}
// Apply system or app filter based on uid.
if (uid >= AID_APP_START) {
set_app_seccomp_filter();
} else {
set_system_seccomp_filter();
}
}
static bool EnableKeepCapabilities(std::string* error_msg) {
int rc = prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0);
if (rc == -1) {
*error_msg = CREATE_ERROR("prctl(PR_SET_KEEPCAPS) failed: %s", strerror(errno));
return false;
}
return true;
}
static bool DropCapabilitiesBoundingSet(std::string* error_msg) {
for (int i = 0; prctl(PR_CAPBSET_READ, i, 0, 0, 0) >= 0; i++) {
int rc = prctl(PR_CAPBSET_DROP, i, 0, 0, 0);
if (rc == -1) {
if (errno == EINVAL) {
ALOGE("prctl(PR_CAPBSET_DROP) failed with EINVAL. Please verify "
"your kernel is compiled with file capabilities support");
} else {
*error_msg = CREATE_ERROR("prctl(PR_CAPBSET_DROP, %d) failed: %s", i, strerror(errno));
return false;
}
}
}
return true;
}
static bool SetInheritable(uint64_t inheritable, std::string* error_msg) {
__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) {
*error_msg = CREATE_ERROR("capget failed: %s", strerror(errno));
return false;
}
capdata[0].inheritable = inheritable;
capdata[1].inheritable = inheritable >> 32;
if (capset(&capheader, &capdata[0]) == -1) {
*error_msg = CREATE_ERROR("capset(inh=%" PRIx64 ") failed: %s", inheritable, strerror(errno));
return false;
}
return true;
}
static bool SetCapabilities(uint64_t permitted, uint64_t effective, uint64_t inheritable,
std::string* error_msg) {
__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) {
*error_msg = CREATE_ERROR("capset(perm=%" PRIx64 ", eff=%" PRIx64 ", inh=%" PRIx64 ") "
"failed: %s", permitted, effective, inheritable, strerror(errno));
return false;
}
return true;
}
static bool SetSchedulerPolicy(std::string* error_msg) {
errno = -set_sched_policy(0, SP_DEFAULT);
if (errno != 0) {
*error_msg = CREATE_ERROR("set_sched_policy(0, SP_DEFAULT) failed: %s", strerror(errno));
return false;
}
return true;
}
static int UnmountTree(const char* path) {
size_t path_len = strlen(path);
FILE* fp = setmntent("/proc/mounts", "r");
if (fp == NULL) {
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> toUnmount;
mntent* mentry;
while ((mentry = getmntent(fp)) != NULL) {
if (strncmp(mentry->mnt_dir, path, path_len) == 0) {
toUnmount.push_front(std::string(mentry->mnt_dir));
}
}
endmntent(fp);
for (auto path : toUnmount) {
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 bool MountEmulatedStorage(uid_t uid, jint mount_mode,
bool force_mount_namespace, std::string* error_msg) {
// See storage config details at http://source.android.com/tech/storage/
String8 storageSource;
if (mount_mode == MOUNT_EXTERNAL_DEFAULT) {
storageSource = "/mnt/runtime/default";
} else if (mount_mode == MOUNT_EXTERNAL_READ) {
storageSource = "/mnt/runtime/read";
} else if (mount_mode == MOUNT_EXTERNAL_WRITE) {
storageSource = "/mnt/runtime/write";
} else if (!force_mount_namespace) {
// Sane default of no storage visible
return true;
}
// Create a second private mount namespace for our process
if (unshare(CLONE_NEWNS) == -1) {
*error_msg = CREATE_ERROR("Failed to unshare(): %s", strerror(errno));
return false;
}
// Handle force_mount_namespace with MOUNT_EXTERNAL_NONE.
if (mount_mode == MOUNT_EXTERNAL_NONE) {
return true;
}
if (TEMP_FAILURE_RETRY(mount(storageSource.string(), "/storage",
NULL, MS_BIND | MS_REC | MS_SLAVE, NULL)) == -1) {
*error_msg = CREATE_ERROR("Failed to mount %s to /storage: %s",
storageSource.string(),
strerror(errno));
return false;
}
// Mount user-specific symlink helper into place
userid_t user_id = multiuser_get_user_id(uid);
const String8 userSource(String8::format("/mnt/user/%d", user_id));
if (fs_prepare_dir(userSource.string(), 0751, 0, 0) == -1) {
*error_msg = CREATE_ERROR("fs_prepare_dir failed on %s", userSource.string());
return false;
}
if (TEMP_FAILURE_RETRY(mount(userSource.string(), "/storage/self",
NULL, MS_BIND, NULL)) == -1) {
*error_msg = CREATE_ERROR("Failed to mount %s to /storage/self: %s",
userSource.string(),
strerror(errno));
return false;
}
return true;
}
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 dup2(), replacing it with a valid
// (open) descriptor to /dev/null.
static bool DetachDescriptors(JNIEnv* env, jintArray fdsToClose, std::string* error_msg) {
if (!fdsToClose) {
return true;
}
jsize count = env->GetArrayLength(fdsToClose);
ScopedIntArrayRO ar(env, fdsToClose);
if (ar.get() == NULL) {
*error_msg = "Bad fd array";
return false;
}
jsize i;
int devnull;
for (i = 0; i < count; i++) {
devnull = open("/dev/null", O_RDWR);
if (devnull < 0) {
*error_msg = std::string("Failed to open /dev/null: ").append(strerror(errno));
return false;
}
ALOGV("Switching descriptor %d to /dev/null: %s", ar[i], strerror(errno));
if (dup2(devnull, ar[i]) < 0) {
*error_msg = StringPrintf("Failed dup2() on descriptor %d: %s", ar[i], strerror(errno));
return false;
}
close(devnull);
}
return true;
}
void SetThreadName(const char* thread_name) {
bool hasAt = false;
bool hasDot = false;
const char* s = thread_name;
while (*s) {
if (*s == '.') {
hasDot = true;
} else if (*s == '@') {
hasAt = true;
}
s++;
}
const int len = s - thread_name;
if (len < 15 || hasAt || !hasDot) {
s = thread_name;
} else {
s = thread_name + len - 15;
}
// pthread_setname_np fails rather than truncating long strings.
char buf[16]; // MAX_TASK_COMM_LEN=16 is hard-coded into bionic
strlcpy(buf, s, 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);
}
// The list of open zygote file descriptors.
static FileDescriptorTable* gOpenFdTable = NULL;
static bool FillFileDescriptorVector(JNIEnv* env,
jintArray java_fds,
std::vector<int>* fds,
std::string* error_msg) {
CHECK(fds != nullptr);
if (java_fds != nullptr) {
ScopedIntArrayRO ar(env, java_fds);
if (ar.get() == nullptr) {
*error_msg = "Bad fd array";
return false;
}
fds->reserve(ar.size());
for (size_t i = 0; i < ar.size(); ++i) {
fds->push_back(ar[i]);
}
}
return true;
}
// Utility routine to fork zygote and specialize the child process.
static pid_t ForkAndSpecializeCommon(JNIEnv* env, uid_t uid, gid_t gid, jintArray javaGids,
jint runtime_flags, jobjectArray javaRlimits,
jlong permittedCapabilities, jlong effectiveCapabilities,
jint mount_external,
jstring java_se_info, jstring java_se_name,
bool is_system_server, jintArray fdsToClose,
jintArray fdsToIgnore, bool is_child_zygote,
jstring instructionSet, jstring dataDir) {
SetSignalHandlers();
sigset_t sigchld;
sigemptyset(&sigchld);
sigaddset(&sigchld, SIGCHLD);
auto fail_fn = [env, java_se_name, is_system_server](const std::string& msg)
__attribute__ ((noreturn)) {
const char* se_name_c_str = nullptr;
std::unique_ptr<ScopedUtfChars> se_name;
if (java_se_name != nullptr) {
se_name.reset(new ScopedUtfChars(env, java_se_name));
se_name_c_str = se_name->c_str();
}
if (se_name_c_str == nullptr && is_system_server) {
se_name_c_str = "system_server";
}
const std::string& error_msg = (se_name_c_str == nullptr)
? msg
: StringPrintf("(%s) %s", se_name_c_str, msg.c_str());
env->FatalError(error_msg.c_str());
__builtin_unreachable();
};
// 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.
if (sigprocmask(SIG_BLOCK, &sigchld, nullptr) == -1) {
fail_fn(CREATE_ERROR("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)));
}
// Close any logging related FDs before we start evaluating the list of
// file descriptors.
__android_log_close();
std::string error_msg;
// 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).
std::vector<int> fds_to_ignore;
if (!FillFileDescriptorVector(env, fdsToIgnore, &fds_to_ignore, &error_msg)) {
fail_fn(error_msg);
}
if (gOpenFdTable == NULL) {
gOpenFdTable = FileDescriptorTable::Create(fds_to_ignore, &error_msg);
if (gOpenFdTable == NULL) {
fail_fn(error_msg);
}
} else if (!gOpenFdTable->Restat(fds_to_ignore, &error_msg)) {
fail_fn(error_msg);
}
pid_t pid = fork();
if (pid == 0) {
PreApplicationInit();
// Clean up any descriptors which must be closed immediately
if (!DetachDescriptors(env, fdsToClose, &error_msg)) {
fail_fn(error_msg);
}
// Re-open all remaining open file descriptors so that they aren't shared
// with the zygote across a fork.
if (!gOpenFdTable->ReopenOrDetach(&error_msg)) {
fail_fn(error_msg);
}
if (sigprocmask(SIG_UNBLOCK, &sigchld, nullptr) == -1) {
fail_fn(CREATE_ERROR("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)));
}
// Keep capabilities across UID change, unless we're staying root.
if (uid != 0) {
if (!EnableKeepCapabilities(&error_msg)) {
fail_fn(error_msg);
}
}
if (!SetInheritable(permittedCapabilities, &error_msg)) {
fail_fn(error_msg);
}
if (!DropCapabilitiesBoundingSet(&error_msg)) {
fail_fn(error_msg);
}
bool use_native_bridge = !is_system_server && (instructionSet != NULL)
&& android::NativeBridgeAvailable();
if (use_native_bridge) {
ScopedUtfChars isa_string(env, instructionSet);
use_native_bridge = android::NeedsNativeBridge(isa_string.c_str());
}
if (use_native_bridge && dataDir == NULL) {
// dataDir should never be null if we need to use a native bridge.
// In general, dataDir will never be null 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 dataDir == NULL.");
}
if (!MountEmulatedStorage(uid, mount_external, use_native_bridge, &error_msg)) {
ALOGW("Failed to mount emulated storage: %s (%s)", error_msg.c_str(), strerror(errno));
if (errno == ENOTCONN || errno == EROFS) {
// When device is actively encrypting, we get ENOTCONN here
// since FUSE was mounted before the framework restarted.
// When encrypted device is booting, we get EROFS since
// FUSE hasn't been created yet by init.
// In either case, continue without external storage.
} else {
fail_fn(error_msg);
}
}
// 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) {
int rc = createProcessGroup(uid, getpid());
if (rc != 0) {
if (rc == -EROFS) {
ALOGW("createProcessGroup failed, kernel missing CONFIG_CGROUP_CPUACCT?");
} else {
ALOGE("createProcessGroup(%d, %d) failed: %s", uid, pid, strerror(-rc));
}
}
}
std::string error_msg;
if (!SetGids(env, javaGids, &error_msg)) {
fail_fn(error_msg);
}
if (!SetRLimits(env, javaRlimits, &error_msg)) {
fail_fn(error_msg);
}
if (use_native_bridge) {
ScopedUtfChars isa_string(env, instructionSet);
ScopedUtfChars data_dir(env, dataDir);
android::PreInitializeNativeBridge(data_dir.c_str(), isa_string.c_str());
}
int rc = setresgid(gid, gid, gid);
if (rc == -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);
rc = setresuid(uid, uid, uid);
if (rc == -1) {
fail_fn(CREATE_ERROR("setresuid(%d) failed: %s", uid, strerror(errno)));
}
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));
}
}
if (!SetCapabilities(permittedCapabilities, effectiveCapabilities, permittedCapabilities,
&error_msg)) {
fail_fn(error_msg);
}
if (!SetSchedulerPolicy(&error_msg)) {
fail_fn(error_msg);
}
const char* se_info_c_str = NULL;
ScopedUtfChars* se_info = NULL;
if (java_se_info != NULL) {
se_info = new ScopedUtfChars(env, java_se_info);
se_info_c_str = se_info->c_str();
if (se_info_c_str == NULL) {
fail_fn("se_info_c_str == NULL");
}
}
const char* se_name_c_str = NULL;
ScopedUtfChars* se_name = NULL;
if (java_se_name != NULL) {
se_name = new ScopedUtfChars(env, java_se_name);
se_name_c_str = se_name->c_str();
if (se_name_c_str == NULL) {
fail_fn("se_name_c_str == NULL");
}
}
rc = selinux_android_setcontext(uid, is_system_server, se_info_c_str, se_name_c_str);
if (rc == -1) {
fail_fn(CREATE_ERROR("selinux_android_setcontext(%d, %d, \"%s\", \"%s\") failed", uid,
is_system_server, se_info_c_str, se_name_c_str));
}
// Make it easier to debug audit logs by setting the main thread's name to the
// nice name rather than "app_process".
if (se_name_c_str == NULL && is_system_server) {
se_name_c_str = "system_server";
}
if (se_name_c_str != NULL) {
SetThreadName(se_name_c_str);
}
delete se_info;
delete se_name;
// Unset the SIGCHLD handler, but keep ignoring SIGHUP (rationale in SetSignalHandlers).
UnsetChldSignalHandler();
env->CallStaticVoidMethod(gZygoteClass, gCallPostForkChildHooks, runtime_flags,
is_system_server, is_child_zygote, instructionSet);
if (env->ExceptionCheck()) {
fail_fn("Error calling post fork hooks.");
}
} else if (pid > 0) {
// the parent process
// We blocked SIGCHLD prior to a fork, we unblock it here.
if (sigprocmask(SIG_UNBLOCK, &sigchld, nullptr) == -1) {
fail_fn(CREATE_ERROR("sigprocmask(SIG_SETMASK, { SIGCHLD }) failed: %s", strerror(errno)));
}
}
return pid;
}
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);
}
} // anonymous namespace
namespace android {
static void com_android_internal_os_Zygote_nativeSecurityInit(JNIEnv*, jclass) {
// security_getenforce is not allowed on app process. Initialize and cache the value before
// zygote forks.
g_is_security_enforced = security_getenforce();
}
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 se_name,
jintArray fdsToClose, jintArray fdsToIgnore, jboolean is_child_zygote,
jstring instructionSet, jstring appDataDir) {
jlong capabilities = 0;
// Grant CAP_WAKE_ALARM to the Bluetooth process.
// Additionally, allow bluetooth to open packet sockets so it can start the DHCP client.
// Grant CAP_SYS_NICE to allow Bluetooth to set RT priority for
// audio-related threads.
// TODO: consider making such functionality an RPC to netd.
if (multiuser_get_app_id(uid) == AID_BLUETOOTH) {
capabilities |= (1LL << CAP_WAKE_ALARM);
capabilities |= (1LL << CAP_NET_RAW);
capabilities |= (1LL << CAP_NET_BIND_SERVICE);
capabilities |= (1LL << CAP_SYS_NICE);
}
// 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 != NULL) {
jsize gids_num = env->GetArrayLength(gids);
ScopedIntArrayRO ar(env, gids);
if (ar.get() == NULL) {
RuntimeAbort(env, __LINE__, "Bad gids array");
}
for (int i = 0; i < gids_num; i++) {
if (ar[i] == AID_WAKELOCK) {
gid_wakelock_found = true;
break;
}
}
}
if (gid_wakelock_found) {
capabilities |= (1LL << CAP_BLOCK_SUSPEND);
}
// If forking a child zygote process, that zygote will need to be able to change
// the UID and GID of processes it forks, as well as drop those capabilities.
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.
capabilities &= GetEffectiveCapabilityMask(env);
return ForkAndSpecializeCommon(env, uid, gid, gids, runtime_flags,
rlimits, capabilities, capabilities, mount_external, se_info,
se_name, false, fdsToClose, fdsToIgnore, is_child_zygote == JNI_TRUE,
instructionSet, appDataDir);
}
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 permittedCapabilities,
jlong effectiveCapabilities) {
pid_t pid = ForkAndSpecializeCommon(env, uid, gid, gids,
runtime_flags, rlimits,
permittedCapabilities, effectiveCapabilities,
MOUNT_EXTERNAL_DEFAULT, NULL, NULL, true, NULL,
NULL, false, NULL, NULL);
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!");
}
// Assign system_server to the correct memory cgroup.
// Not all devices mount /dev/memcg so check for the file first
// to avoid unnecessarily printing errors and denials in the logs.
if (!access("/dev/memcg/system/tasks", F_OK) &&
!WriteStringToFile(StringPrintf("%d", pid), "/dev/memcg/system/tasks")) {
ALOGE("couldn't write %d to /dev/memcg/system/tasks", pid);
}
}
return 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 == NULL");
}
FileDescriptorWhitelist::Get()->Allow(path_cstr);
}
static void com_android_internal_os_Zygote_nativeUnmountStorageOnInit(JNIEnv* env, jclass) {
// 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");
}
static const JNINativeMethod gMethods[] = {
{ "nativeSecurityInit", "()V",
(void *) com_android_internal_os_Zygote_nativeSecurityInit },
{ "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 },
{ "nativeUnmountStorageOnInit", "()V",
(void *) com_android_internal_os_Zygote_nativeUnmountStorageOnInit },
{ "nativePreApplicationInit", "()V",
(void *) com_android_internal_os_Zygote_nativePreApplicationInit }
};
int register_com_android_internal_os_Zygote(JNIEnv* env) {
gZygoteClass = MakeGlobalRefOrDie(env, FindClassOrDie(env, kZygoteClassName));
gCallPostForkChildHooks = GetStaticMethodIDOrDie(env, gZygoteClass, "callPostForkChildHooks",
"(IZZLjava/lang/String;)V");
return RegisterMethodsOrDie(env, "com/android/internal/os/Zygote", gMethods, NELEM(gMethods));
}
} // namespace android