Fork once only

Right now there are three threads (process)
1. Main thread in parent: monitor logcat
2. Second thread in parent: monitor hidelist
3. Children: switch namespace and unmounts

jni/magiskhide.c

@@ -18,8 +18,8 @@
 #define HIDELIST 	"/magisk/.core/magiskhide/hidelist"
 
 FILE *logfile;
-int i, list_size;
+int i, list_size, pipefd[2];
-char **hide_list = NULL, cache_block[256];
+char **hide_list = NULL;
 pthread_mutex_t mutex;
 
 char **file_to_str_arr(FILE *fp, int *size) {
@@ -55,34 +55,28 @@ void lazy_unmount(const char* mountpoint) {
 		fprintf(logfile, "MagiskHide: Unmount Failed (%s)\n", mountpoint);
 }
 
-//WARNING: Calling this will change our current namespace
+int hideMagisk() {
-//We don't care because we don't want to run from here anyway
+	int pid;
-int hideMagisk(int pid, int uid) {
+	char path[256], cache_block[256];
-	// struct stat info;
+	cache_block[0] = 0;
-	char path[256];
-	// snprintf(path, 256, "/proc/%d", pid);
-	// if (stat(path, &info) == -1) {
-	// 	fprintf(logfile, "MagiskHide: Unable to get info for pid=%d\n", pid);
-	// 	return 1;
-	// }
-	// if (info.st_uid != uid) {
-	// 	fprintf(logfile, "MagiskHide: Incorrect uid=%d, expect uid=%d\n", info.st_uid, uid);
-	// 	return 1;
-	// }
 
+	close(pipefd[1]);
+	while(1) {
+		read(pipefd[0], &pid, sizeof(pid));
+		if(pid == -1) break;
 		snprintf(path, 256, "/proc/%d/ns/mnt", pid);
 		int fd = open(path, O_RDONLY);
-	if(fd == -1) return 2; // Maybe process died..
+		if(fd == -1) continue; // Maybe process died..
 		if(setns(fd, 0) == -1) {
 			fprintf(logfile, "MagiskHide: Unable to change namespace for pid=%d\n", pid);
-		return 3;
+			continue;
 		}
 
 		snprintf(path, 256, "/proc/%d/mounts", pid);
 		FILE *mount_fp = fopen(path, "r");
 		if (mount_fp == NULL) {
 			fprintf(logfile, "MagiskHide: Error opening mount list!\n");
-		return 4;
+			continue;
 		}
 
 		int mount_size;
@@ -102,7 +96,7 @@ int hideMagisk(int pid, int uid) {
 		for(i = mount_size - 1; i >= 0; --i) {
 			if (strstr(mount_list[i], "tmpfs /system/") || strstr(mount_list[i], "tmpfs /vendor/")
 				|| (strstr(mount_list[i], cache_block) && strstr(mount_list[i], "/system")) ) {
-			sscanf(mount_list[i], "%256s %256s", mountpoint, mountpoint);
+				sscanf(mount_list[i], "%*s %256s", mountpoint);
 				lazy_unmount(mountpoint);
 			}
 			free(mount_list[i]);
@@ -118,15 +112,31 @@ int hideMagisk(int pid, int uid) {
 		// Unmount loop mounts
 		for(i = mount_size - 1; i >= 0; --i) {
 			if (strstr(mount_list[i], "/dev/block/loop")) {
-			sscanf(mount_list[i], "%256s %256s", mountpoint, mountpoint);
+				sscanf(mount_list[i], "%*s %256s", mountpoint);
 				lazy_unmount(mountpoint);
 			}
 			free(mount_list[i]);
 		}
 		// Free memory
 		free(mount_list);
+	}
 
-	return 0;
+	// Should never go here
+	return 1;
+
+	// Below are UID checks, not used now but I'll leave it here
+
+	// struct stat info;
+	
+	// snprintf(path, 256, "/proc/%d", pid);
+	// if (stat(path, &info) == -1) {
+	// 	fprintf(logfile, "MagiskHide: Unable to get info for pid=%d\n", pid);
+	// 	return 1;
+	// }
+	// if (info.st_uid != uid) {
+	// 	fprintf(logfile, "MagiskHide: Incorrect uid=%d, expect uid=%d\n", info.st_uid, uid);
+	// 	return 1;
+	// }
 }
 
 void update_list(const char *listpath) {
@@ -202,11 +212,18 @@ int main(int argc, char **argv, char **envp) {
 		logfile = fopen(LOGFILE, "a+");
 		setbuf(logfile, NULL);
 
-		// Set cache block to null
+		// Fork a child to handle namespace switches and unmounts
-		cache_block[0] = 0;
+		pipe(pipefd);
+		forkpid = fork();
+		if (forkpid < 0)
+			return 1;
+		if (forkpid == 0)
+			return hideMagisk();
 
+		close(pipefd[0]);
+
+		// Start a thread to constantly check the hide list
 		pthread_t list_monitor;
-
 		pthread_mutex_init(&mutex, NULL);
 		pthread_create(&list_monitor, NULL, monitor_list, HIDELIST);
 
@@ -238,25 +255,22 @@ int main(int argc, char **argv, char **envp) {
 			for (i = 0; i < list_size; ++i) {
 				if(strstr(processName, hide_list[i])) {
 					fprintf(logfile, "MagiskHide: Disabling for process=%s, PID=%d, UID=%d\n", processName, pid, uid);
-					forkpid = fork();
+					write(pipefd[1], &pid, sizeof(pid));
-					if (forkpid < 0)
-						break;
-					if (forkpid == 0) {
-						hideMagisk(pid, uid);
-						return 0;
-					}
-					waitpid(forkpid, NULL, 0);
-					kill(forkpid, SIGTERM);
-					break;
 				}
 			}
 		}
 
+		// Close the logcat monitor
 		pclose(p);
 
+		// Close the config list monitor
 		pthread_kill(list_monitor, SIGQUIT);
 		pthread_mutex_destroy(&mutex);
 
+		// Terminate our children
+		i = -1;
+		write(pipefd[1], &i, sizeof(i));
+
 		fprintf(logfile, "MagiskHide: Cannot read from logcat, abort...\n");
 		fclose(logfile);