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Specialize does not need to close logd_fd

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topjohnwu 2022-09-06 03:01:39 -07:00
parent 6e299018a4
commit 4e14dab60a
1 changed files with 76 additions and 80 deletions
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156
native/src/zygisk/hook.cpp
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@ -33,6 +33,7 @@ enum {
SERVER_FORK_AND_SPECIALIZE,
DO_REVERT_UNMOUNT,
CAN_UNLOAD_ZYGISK,
SKIP_CLOSE_LOGD_FD,
FLAG_MAX
};
@ -41,6 +42,8 @@ enum {
void name##_pre(); \
void name##_post();
#define MAX_FD_SIZE 1024
struct HookContext {
JNIEnv *env;
union {
@ -55,12 +58,12 @@ struct HookContext {
int pid;
bitset<FLAG_MAX> flags;
uint32_t info_flags;
bitset<MAX_FD_SIZE> allowed_fds;
HookContext() : env(nullptr), args{nullptr}, process(nullptr), pid(-1), info_flags(0) {}
static void pre_specialize_start(DIR *dir, bitset<1024> &allowed_fds);
void pre_specialize_end(DIR *dir, bitset<1024> &allowed_fds);
bool setup_fd_ignore(bitset<1024> *allowed_fds = nullptr);
void setup_fd_ignore();
void sanitize_fds();
void run_modules_pre(const vector<int> &fds);
void run_modules_post();
@ -149,7 +152,6 @@ DCL_HOOK_FUNC(int, jniRegisterNativeMethods,
}
// Skip actual fork and return cached result if applicable
// Also unload first stage zygisk if necessary
DCL_HOOK_FUNC(int, fork) {
return (g_ctx && g_ctx->pid >= 0) ? g_ctx->pid : old_fork();
}
@ -174,12 +176,18 @@ DCL_HOOK_FUNC(int, unshare, int flags) {
return res;
}
// A place to clean things up before zygote evaluates fd table
// Close logd_fd if necessary to prevent crashing
// For more info, check comments in zygisk_log_write
DCL_HOOK_FUNC(void, android_log_close) {
if (g_ctx == nullptr || !g_ctx->flags[APP_SPECIALIZE]) {
// Close fd to prevent crashing.
// For more info, check comments in zygisk_log_write.
if (g_ctx == nullptr || g_ctx->pid > 0) {
// This happens either in the zygote daemon or during nativeForkApp, nativeForkUsap etc.
close(logd_fd.exchange(-1));
// Do NOT revert back to android logging
} else if (!g_ctx->flags[SKIP_CLOSE_LOGD_FD]) {
close(logd_fd.exchange(-1));
// Switch to plain old android logging because we cannot talk
// to magiskd to fetch our log pipe afterwards anyways.
android_logging();
}
old_android_log_close();
}
@ -381,81 +389,98 @@ uint32_t ZygiskModule::getFlags() {
// -----------------------------------------------------------------
bool HookContext::setup_fd_ignore(bitset<1024> *allowed_fds) {
if (flags[APP_SPECIALIZE]) {
void HookContext::setup_fd_ignore() {
if (flags[APP_FORK_AND_SPECIALIZE]) {
if (args.app->fds_to_ignore == nullptr) {
// The field fds_to_ignore don't exist if
// - Running before Android 8.0
// - Called by nativeSpecializeAppProcess
// In either case, FDs are not checked, so we can simply skip
return true;
// The field fds_to_ignore don't exist before Android 8.0, which FDs are not checked
flags[SKIP_CLOSE_LOGD_FD] = true;
return;
}
bool success = false;
if (jintArray fdsToIgnore = *args.app->fds_to_ignore) {
int *arr = env->GetIntArrayElements(fdsToIgnore, nullptr);
int len = env->GetArrayLength(fdsToIgnore);
if (allowed_fds) {
for (int i = 0; i < len; ++i) {
int fd = arr[i];
if (fd >= 0 && fd < 1024) {
(*allowed_fds)[fd] = true;
}
for (int i = 0; i < len; ++i) {
int fd = arr[i];
if (fd >= 0 && fd < MAX_FD_SIZE) {
allowed_fds[fd] = true;
}
}
jintArray newFdList = nullptr;
if (logd_fd >= 0 && (newFdList = env->NewIntArray(len + 1))) {
success = true;
env->SetIntArrayRegion(newFdList, 0, len, arr);
int fd = logd_fd;
env->SetIntArrayRegion(newFdList, len, 1, &fd);
*args.app->fds_to_ignore = newFdList;
success = true;
}
env->ReleaseIntArrayElements(fdsToIgnore, arr, JNI_ABORT);
} else {
jintArray newFdList = nullptr;
if (logd_fd >= 0 && (newFdList = env->NewIntArray(1))) {
success = true;
int fd = logd_fd;
env->SetIntArrayRegion(newFdList, 0, 1, &fd);
*args.app->fds_to_ignore = newFdList;
success = true;
}
}
return success;
}
return false;
}
void HookContext::pre_specialize_start(DIR *dir, bitset<1024> &allowed_fds) {
// Record all open fds
for (dirent *entry; (entry = xreaddir(dir));) {
int fd = parse_int(entry->d_name);
if (fd < 0 || fd >= 1024) {
close(fd);
continue;
}
allowed_fds[fd] = true;
flags[SKIP_CLOSE_LOGD_FD] = success;
}
}
void HookContext::pre_specialize_end(DIR *dir, bitset<1024> &allowed_fds) {
bool disable_zygisk_logging = !setup_fd_ignore(&allowed_fds);
void HookContext::sanitize_fds() {
setup_fd_ignore();
// Close all forbidden fds to prevent crashing
rewinddir(dir);
for (dirent *entry; (entry = xreaddir(dir));) {
auto dir = xopen_dir("/proc/self/fd");
rewinddir(dir.get());
int dfd = dirfd(dir.get());
for (dirent *entry; (entry = xreaddir(dir.get()));) {
int fd = parse_int(entry->d_name);
if (fd < 0 || fd >= 1024 || !allowed_fds[fd]) {
if ((fd < 0 || fd >= MAX_FD_SIZE || !allowed_fds[fd]) && fd != dfd) {
close(fd);
}
}
}
if (disable_zygisk_logging) {
close(logd_fd.exchange(-1));
android_logging();
int sigmask(int how, int signum) {
sigset_t set;
sigemptyset(&set);
sigaddset(&set, signum);
return sigprocmask(how, &set, nullptr);
}
void HookContext::fork_pre() {
g_ctx = this;
// Do our own fork before loading any 3rd party code
// First block SIGCHLD, unblock after original fork is done
sigmask(SIG_BLOCK, SIGCHLD);
pid = old_fork();
if (pid == 0) {
// Record all open fds
auto dir = xopen_dir("/proc/self/fd");
for (dirent *entry; (entry = xreaddir(dir.get()));) {
int fd = parse_int(entry->d_name);
if (fd < 0 || fd >= MAX_FD_SIZE) {
close(fd);
continue;
}
allowed_fds[fd] = true;
}
// The dirfd should not be allowed
allowed_fds[dirfd(dir.get())] = false;
}
}
void HookContext::fork_post() {
// Unblock SIGCHLD in case the original method didn't
sigmask(SIG_UNBLOCK, SIGCHLD);
g_ctx = nullptr;
unload_zygisk();
}
void HookContext::run_modules_pre(const vector<int> &fds) {
// Because the data structure stored in the vector is self referencing, in order to prevent
// dangling pointers, the vector has to be pre-allocated to ensure reallocation does not occur
@ -528,12 +553,10 @@ void HookContext::nativeSpecializeAppProcess_pre() {
ZLOGV("pre forkAndSpecialize [%s]\n", process);
} else {
ZLOGV("pre specialize [%s]\n", process);
// App specialize does not check FD
flags[SKIP_CLOSE_LOGD_FD] = true;
}
bitset<1024> allowed_fds;
auto dir = open_dir("/proc/self/fd");
pre_specialize_start(dir.get(), allowed_fds);
vector<int> module_fds;
int fd = remote_get_info(args.app->uid, process, &info_flags, module_fds);
if ((info_flags & UNMOUNT_MASK) == UNMOUNT_MASK) {
@ -543,8 +566,6 @@ void HookContext::nativeSpecializeAppProcess_pre() {
run_modules_pre(module_fds);
}
close(fd);
pre_specialize_end(dir.get(), allowed_fds);
}
void HookContext::nativeSpecializeAppProcess_post() {
@ -577,10 +598,6 @@ void HookContext::nativeForkSystemServer_pre() {
ZLOGV("pre forkSystemServer\n");
bitset<1024> allowed_fds;
auto dir = open_dir("/proc/self/fd");
pre_specialize_start(dir.get(), allowed_fds);
vector<int> module_fds;
int fd = remote_get_info(1000, "system_server", &info_flags, module_fds);
if (fd >= 0) {
@ -602,7 +619,7 @@ void HookContext::nativeForkSystemServer_pre() {
close(fd);
}
pre_specialize_end(dir.get(), allowed_fds);
sanitize_fds();
}
void HookContext::nativeForkSystemServer_post() {
@ -618,8 +635,9 @@ void HookContext::nativeForkAndSpecialize_pre() {
flags[APP_FORK_AND_SPECIALIZE] = true;
if (pid == 0) {
nativeSpecializeAppProcess_pre();
} else if (!setup_fd_ignore()) {
close(logd_fd.exchange(-1));
sanitize_fds();
} else {
setup_fd_ignore();
}
}
@ -630,28 +648,6 @@ void HookContext::nativeForkAndSpecialize_post() {
fork_post();
}
int sigmask(int how, int signum) {
sigset_t set;
sigemptyset(&set);
sigaddset(&set, signum);
return sigprocmask(how, &set, nullptr);
}
// Do our own fork before loading any 3rd party code
// First block SIGCHLD, unblock after original fork is done
void HookContext::fork_pre() {
g_ctx = this;
sigmask(SIG_BLOCK, SIGCHLD);
pid = old_fork();
}
// Unblock SIGCHLD in case the original method didn't
void HookContext::fork_post() {
sigmask(SIG_UNBLOCK, SIGCHLD);
g_ctx = nullptr;
unload_zygisk();
}
} // namespace
static bool hook_refresh() {