start: handle setting death signal smarter

src/lxc/start.c

@@ -896,6 +896,32 @@ static int must_drop_cap_sys_boot(struct lxc_conf *conf)
 	return 0;
 }
 
+static int lxc_set_death_signal(int signal)
+{
+	int ret;
+	pid_t ppid;
+
+	ret = prctl(PR_SET_PDEATHSIG, signal, 0, 0, 0);
+
+	/* Check whether we have been orphaned. */
+	ppid = (pid_t)syscall(SYS_getppid);
+	if (ppid == 1) {
+		pid_t self;
+
+		self = lxc_raw_getpid();
+		ret = kill(self, SIGKILL);
+		if (ret < 0)
+			return -1;
+	}
+
+	if (ret < 0) {
+		SYSERROR("Failed to set PR_SET_PDEATHSIG to %d", signal);
+		return -1;
+	}
+
+	return 0;
+}
+
 static int do_start(void *data)
 {
 	int ret;
@@ -907,10 +933,7 @@ static int do_start(void *data)
 	int devnull_fd = -1;
 	struct lxc_handler *handler = data;
 
-	if (sigprocmask(SIG_SETMASK, &handler->oldmask, NULL)) {
-		SYSERROR("Failed to set signal mask.");
-		return -1;
-	}
+	lxc_sync_fini_parent(handler);
 
 	/* This prctl must be before the synchro, so if the parent dies before
 	 * we set the parent death signal, we will detect its death with the
@@ -918,21 +941,26 @@ static int do_start(void *data)
 	 * exit before we set the pdeath signal leading to a unsupervized
 	 * container.
 	 */
-	ret = prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
+	ret = lxc_set_death_signal(SIGKILL);
 	if (ret < 0) {
 		SYSERROR("Failed to set PR_SET_PDEATHSIG to SIGKILL");
-		return -1;
+		goto out_warn_father;
 	}
 
-	lxc_sync_fini_parent(handler);
+	ret = sigprocmask(SIG_SETMASK, &handler->oldmask, NULL);
+	if (ret < 0) {
+		SYSERROR("Failed to set signal mask");
+		goto out_warn_father;
+	}
 
 	/* Don't leak the pinfd to the container. */
 	if (handler->pinfd >= 0) {
 		close(handler->pinfd);
 	}
 
-	if (lxc_sync_wait_parent(handler, LXC_SYNC_STARTUP))
-		return -1;
+	ret = lxc_sync_wait_parent(handler, LXC_SYNC_STARTUP);
+	if (ret < 0)
+		goto out_warn_father;
 
 	/* Unshare CLONE_NEWNET after CLONE_NEWUSER. See
 	 * https://github.com/lxc/lxd/issues/1978.
@@ -980,7 +1008,7 @@ static int do_start(void *data)
 		}
 
 		/* set{g,u}id() clears deathsignal */
-		ret = prctl(PR_SET_PDEATHSIG, SIGKILL, 0, 0, 0);
+		ret = lxc_set_death_signal(SIGKILL);
 		if (ret < 0) {
 			SYSERROR("Failed to set PR_SET_PDEATHSIG to SIGKILL");
 			goto out_warn_father;
@@ -1390,6 +1418,7 @@ static int lxc_spawn(struct lxc_handler *handler)
 		SYSERROR("Failed to clone a new set of namespaces.");
 		goto out_delete_net;
 	}
+	TRACE("Cloned child process %d", handler->pid);
 
 	for (i = 0; i < LXC_NS_MAX; i++)
 		if (flags & ns_info[i].clone_flag)