From 06b93e5c1caf5d36d51132cb85c11a96cbdae023 Mon Sep 17 00:00:00 2001
From: "lihaoxiang (F)" <[email protected]>
Date: Thu, 1 Dec 2022 12:10:49 +0800
Subject: [PATCH] quota-nld: fix open PID file failed when systemd read it

Running quota_nld by systemd might cause the problem that systemd
couldn't open the PID file generated by quota_nld. In fact, the PID
file hasn't existed yet because it originates from the child process
of quota_nld which is a daemon process. As the main process exit,
systemd try to access the PID file but the daemon hadn't create it
that time.

In this situation, we move the procedure of creating PID file into the
parent process to ensure the PID file must existed when quota_nld exit.
After that, the above problem would never occur again.

[JK: Fixed up SIGTERM handling and format strings]

Signed-off-by: lihaoxiang <[email protected]>
Signed-off-by: Jan Kara <[email protected]>
---
 quota_nld.c | 44 ++++++++++++++++++++++++++++++++++----------
 1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/quota_nld.c b/quota_nld.c
index 09c4775..82e60c2 100644
--- a/quota_nld.c
+++ b/quota_nld.c
@@ -413,7 +413,7 @@ static char *build_pid_file_name(void)
 }
 
 /* Store daemon's PID to file */
-static int store_pid(void)
+static int store_pid(pid_t pid)
 {
 	FILE *pid_file;
 	char *pid_name;
@@ -429,7 +429,7 @@ static int store_pid(void)
 		free(pid_name);
 		return -1;
 	}
-	if (fprintf(pid_file, "%jd\n", (intmax_t)getpid()) < 0) {
+	if (fprintf(pid_file, "%d\n", (int)pid) < 0) {
 		errstr(_("Could not write daemon's PID into '%s'.\n"),
 			pid_name);
 		fclose(pid_file);
@@ -460,7 +460,7 @@ static void remove_pid(int signal)
 }
 
 /* Store daemon's PID into file and register its removal on SIGTERM */
-static void use_pid_file(void)
+static void setup_sigterm_handler(void)
 {
 	struct sigaction term_action;
 
@@ -468,8 +468,36 @@ static void use_pid_file(void)
 	term_action.sa_flags = 0;
 	if (sigemptyset(&term_action.sa_mask) || sigaction(SIGTERM, &term_action, NULL))
 		errstr(_("Could not register PID file removal on SIGTERM.\n"));
-	if (store_pid())
-		errstr(_("Could not store my PID %jd.\n"), (intmax_t )getpid());
+}
+
+static void fork_daemon(void)
+{
+	pid_t pid = fork();
+	if (pid < 0) {
+		errstr(_("Failed to daemonize: fork: %s\n"), strerror(errno));
+		exit(1);
+	} else if (pid != 0) {
+		if (store_pid(pid)) {
+			errstr(_("Could not store my PID %d.\n"), (int)pid);
+			kill(pid, SIGKILL);
+		}
+		exit(0);
+	}
+
+	setup_sigterm_handler();
+	if (setsid() < 0) {
+		errstr(_("Failed to daemonize: setsid: %s\n"), strerror(errno));
+		exit(1);
+	}
+	if (chdir("/") < 0)
+		errstr(_("Failed to chdir in daemonize\n"));
+	int fd = open("/dev/null", O_RDWR, 0);
+	if (fd >= 0) {
+		dup2(fd, STDIN_FILENO);
+		dup2(fd, STDOUT_FILENO);
+		dup2(fd, STDERR_FILENO);
+		close(fd);
+	}
 }
 
 int main(int argc, char **argv)
@@ -485,11 +513,7 @@ int main(int argc, char **argv)
 		dhandle = init_dbus();
 	if (!(flags & FL_NODAEMON)) {
 		use_syslog();
-		if (daemon(0, 0)) {
-			errstr(_("Failed to daemonize: %s\n"), strerror(errno));
-			exit(1);
-		};
-		use_pid_file();
+		fork_daemon();
 	}
 	run(nsock);
 	return 0;
-- 
1.8.3.1