SIGSTOP any possible process ASAP

Shut down any UID matching process and resume if it turns out not to
be our target. Since we will record every single process we have ever
paused, this means that the same process will not be paused erroneously
for another time.

This is an optimization to hijack the app as soon as possible.

native/jni/magiskhide/proc_monitor.cpp

@@ -46,6 +46,7 @@ static inline void lazy_unmount(const char* mountpoint) {
 		LOGD("hide_daemon: Unmounted (%s)\n", mountpoint);
 }
 
+#if 0
 static inline int parse_ppid(const int pid) {
 	char path[32];
 	int ppid;
@@ -61,6 +62,7 @@ static inline int parse_ppid(const int pid) {
 
 	return ppid;
 }
+#endif
 
 static void hide_daemon(int pid) {
 	RunFinally fin([=]() -> void {
@@ -132,21 +134,26 @@ static bool check_pid(int pid, int uid) {
 	if (uid != get_uid(pid))
 		return true;
 
-	struct stat ns, pns;
+	struct stat ns;
-	int ppid;
+	if (read_ns(pid, &ns))
-
-	// Make sure we can read mount namespace
-	if ((ppid = parse_ppid(pid)) < 0 || read_ns(pid, &ns) || read_ns(ppid, &pns))
-		return true;
-	// mount namespace is not separated, we only unmount once
-	if (ns.st_dev == pns.st_dev && ns.st_ino == pns.st_ino)
 		return true;
 
-	// Check if it's a process we haven't already hijacked
+	// Check if we have already seen it before
 	auto pos = pid_ns_map.find(pid);
 	if (pos != pid_ns_map.end() && pos->second == ns.st_ino)
 		return true;
 
+	// Will rather kill all just for one
+	if (kill(pid, SIGSTOP) == -1)
+		return true;
+	// Auto send resume signal if return
+	RunFinally resume([=]() -> void {
+		kill(pid, SIGCONT);
+	});
+
+	// Record this PID
+	pid_ns_map[pid] = ns.st_ino;
+
 	// Check whether process name match hide list
 	const char *process = nullptr;
 	for (auto &proc : uid_proc_map[uid])
@@ -156,20 +163,14 @@ static bool check_pid(int pid, int uid) {
 	if (!process)
 		return true;
 
-	// Send pause signal ASAP
-	if (kill(pid, SIGSTOP) == -1)
-		return true;
-
-	pid_ns_map[pid] = ns.st_ino;
 	LOGI("proc_monitor: [%s] UID=[%d] PID=[%d] ns=[%llu]\n", process, uid, pid, ns.st_ino);
 
-	/*
+	// Disable auto resume PID, and let the daemon do it
-	 * The setns system call do not support multithread processes
+	resume.disable();
-	 * We have to fork a new process, setns, then do the unmounts
-	 */
 	if (fork_dont_care() == 0)
 		hide_daemon(pid);
 
+	// We found what we want, stop traversal
 	return false;
 }
 

native/jni/utils/include/utils.h

@@ -162,10 +162,12 @@ class RunFinally {
 public:
 	explicit RunFinally(std::function<void()> &&fn): fn(std::move(fn)) {}
 
-	~RunFinally() { fn(); }
+	void disable() { fn = nullptr; }
+
+	~RunFinally() { if (fn) fn(); }
 
 private:
-	const std::function<void ()> fn;
+	std::function<void ()> fn;
 };
 
 // file.cpp