Make sure logcat process does not become a zombie

native/jni/core/bootstages.cpp

@@ -645,11 +645,23 @@ static void dump_logs() {
 	if (test != 0)
 		return;
 	rename(LOGFILE, LOGFILE ".bak");
-	int fd = xopen(LOGFILE, O_WRONLY | O_APPEND | O_CREAT | O_CLOEXEC, 0644);
-	exec_t exec { .fd = fd };
-	exec_command(exec, "/system/bin/logcat", "-s", "Magisk");
 	log_dump = true;
-	close(fd);
+	// Start a daemon thread and wait indefinitely
+	new_daemon_thread([](auto) -> void* {
+		int fd = xopen(LOGFILE, O_WRONLY | O_APPEND | O_CREAT | O_CLOEXEC, 0644);
+		exec_t exec {
+			.fd = fd,
+			.fork = fork_no_zombie
+		};
+		int pid = exec_command(exec, "/system/bin/logcat", "-s", "Magisk");
+		close(fd);
+		if (pid < 0) {
+			log_dump = false;
+			return nullptr;
+		}
+		waitpid(pid, nullptr, 0);
+		return nullptr;
+	});
 }
 
 /****************

native/jni/core/daemon.cpp

@@ -140,20 +140,17 @@ static void main_daemon() {
 	pthread_sigmask(SIG_SETMASK, &block_set, nullptr);
 
 	// Loop forever to listen for requests
-	while(true) {
+	for (;;) {
 		int *client = new int;
 		*client = xaccept4(fd, nullptr, nullptr, SOCK_CLOEXEC);
-		pthread_t thread;
-		xpthread_create(&thread, nullptr, request_handler, client);
-		// Detach the thread, we will never join it
-		pthread_detach(thread);
+		new_daemon_thread(request_handler, client);
 	}
 }
 
 int switch_mnt_ns(int pid) {
 	char mnt[32];
 	snprintf(mnt, sizeof(mnt), "/proc/%d/ns/mnt", pid);
-	if(access(mnt, R_OK) == -1) return 1; // Maybe process died..
+	if (access(mnt, R_OK) == -1) return 1; // Maybe process died..
 
 	int fd, ret;
 	fd = xopen(mnt, O_RDONLY);

native/jni/magiskhide/hide_utils.cpp

@@ -366,11 +366,9 @@ void auto_start_magiskhide() {
 	db_settings dbs;
 	get_db_settings(&dbs, HIDE_CONFIG);
 	if (dbs[HIDE_CONFIG]) {
-		pthread_t thread;
-		xpthread_create(&thread, nullptr, [](void*) -> void* {
+		new_daemon_thread([](auto) -> void* {
 			launch_magiskhide(-1);
 			return nullptr;
-		}, nullptr);
-		pthread_detach(thread);
+		});
 	}
 }

native/jni/utils/include/utils.h

@@ -82,6 +82,7 @@ unsigned get_shell_uid();
 unsigned get_system_uid();
 unsigned get_radio_uid();
 int fork_dont_care();
+int fork_no_zombie();
 void gen_rand_str(char *buf, int len);
 int strend(const char *s1, const char *s2);
 
@@ -147,6 +148,9 @@ std::vector<std::string> file_to_vector(const char *filename);
 
 // misc.cpp
 
+int new_daemon_thread(void *(*start_routine) (void *), void *arg = nullptr,
+		const pthread_attr_t *attr = nullptr);
+
 struct exec_t {
 	bool err = false;
 	int fd = -2;

native/jni/utils/misc.cpp

@@ -10,6 +10,7 @@
 #include <syscall.h>
 #include <sys/types.h>
 #include <sys/wait.h>
+#include <sys/prctl.h>
 #include <sys/sysmacros.h>
 
 #include <logging.h>
@@ -50,6 +51,20 @@ int fork_dont_care() {
 	return 0;
 }
 
+int fork_no_zombie() {
+	int pid = xfork();
+	if (pid)
+		return pid;
+	// Unblock all signals
+	sigset_t block_set;
+	sigfillset(&block_set);
+	pthread_sigmask(SIG_UNBLOCK, &block_set, nullptr);
+	prctl(PR_SET_PDEATHSIG, SIGTERM);
+	if (getppid() == 1)
+		exit(1);
+	return 0;
+}
+
 void gen_rand_str(char *buf, int len) {
 	const char base[] = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
 	int urandom;
@@ -201,3 +216,11 @@ int exec_command_sync(exec_t &exec) {
 	return WEXITSTATUS(status);
 }
 
+int new_daemon_thread(void *(*start_routine) (void *), void *arg, const pthread_attr_t *attr) {
+	pthread_t thread;
+	int ret = xpthread_create(&thread, attr, start_routine, arg);
+	if (ret == 0)
+		pthread_detach(thread);
+	return ret;
+}
+