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Be more careful with signals

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Fix #4040
This commit is contained in:
topjohnwu 2021-03-18 03:28:02 -07:00
parent d4e2f2df6e
commit 336f1687c1
1 changed files with 33 additions and 8 deletions
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41
native/jni/magiskhide/proc_monitor.cpp
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@ -145,13 +145,21 @@ static void inotify_event(int) {
check_zygote();
}
// Workaround for the lack of pthread_cancel
static void term_thread(int) {
LOGD("proc_monitor: cleaning up\n");
zygote_map.clear();
attaches.reset();
close(inotify_fd);
inotify_fd = -1;
// Restore all signal handlers that was set
sigset_t set;
sigfillset(&set);
pthread_sigmask(SIG_BLOCK, &set, nullptr);
struct sigaction act{};
act.sa_handler = SIG_DFL;
sigaction(SIGTERMTHRD, &act, nullptr);
sigaction(SIGIO, &act, nullptr);
sigaction(SIGALRM, &act, nullptr);
LOGD("proc_monitor: terminate\n");
pthread_exit(nullptr);
}
@ -276,16 +284,29 @@ static void new_zygote(int pid) {
#define DETACH_AND_CONT { detach_pid(pid); continue; }
void proc_monitor() {
// Unblock some signals
sigset_t block_set;
sigemptyset(&block_set);
sigaddset(&block_set, SIGTERMTHRD);
sigaddset(&block_set, SIGIO);
sigaddset(&block_set, SIGALRM);
pthread_sigmask(SIG_UNBLOCK, &block_set, nullptr);
monitor_thread = pthread_self();
// Backup original mask
sigset_t orig_mask;
pthread_sigmask(SIG_SETMASK, nullptr, &orig_mask);
sigset_t unblock_set;
sigemptyset(&unblock_set);
sigaddset(&unblock_set, SIGTERMTHRD);
sigaddset(&unblock_set, SIGIO);
sigaddset(&unblock_set, SIGALRM);
struct sigaction act{};
sigfillset(&act.sa_mask);
act.sa_handler = SIG_IGN;
sigaction(SIGTERMTHRD, &act, nullptr);
sigaction(SIGIO, &act, nullptr);
sigaction(SIGALRM, &act, nullptr);
// Temporary unblock to clear pending signals
pthread_sigmask(SIG_UNBLOCK, &unblock_set, nullptr);
pthread_sigmask(SIG_SETMASK, &orig_mask, nullptr);
act.sa_handler = term_thread;
sigaction(SIGTERMTHRD, &act, nullptr);
act.sa_handler = inotify_event;
@ -305,6 +326,8 @@ void proc_monitor() {
}
for (int status;;) {
pthread_sigmask(SIG_UNBLOCK, &unblock_set, nullptr);
const int pid = waitpid(-1, &status, __WALL | __WNOTHREAD);
if (pid < 0) {
if (errno == ECHILD) {
@ -319,6 +342,8 @@ void proc_monitor() {
continue;
}
pthread_sigmask(SIG_SETMASK, &orig_mask, nullptr);
if (!WIFSTOPPED(status) /* Ignore if not ptrace-stop */)
DETACH_AND_CONT;