From 74085cc28deb9d95867ad7c350efd11ea722a552 Mon Sep 17 00:00:00 2001
From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Sun, 7 Apr 2024 17:04:37 +0800
Subject: [PATCH] jobs: Allow monitor mode without a tty in non-interactive
 mode

When a tty is unavailable, or the shell is in the background,
job control could still be used for the purpose of setting
process groups.

This is based on work by Jilles Tjoelker from FreeBSD and Steffen
Nurpmeso.

Reported-by: Steffen Nurpmeso <steffen@sdaoden.eu>
Reported-by: Ganael Laplanche <ganael.laplanche@martymac.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
---
 src/jobs.c | 53 +++++++++++++++++++++++++++++++++++------------------
 1 file changed, 35 insertions(+), 18 deletions(-)

diff --git a/src/jobs.c b/src/jobs.c
index a0f4d47..2a2fe22 100644
--- a/src/jobs.c
+++ b/src/jobs.c
@@ -187,11 +187,21 @@ set_curjob(struct job *jp, unsigned mode)
 
 int jobctl;
 
+static void xxtcsetpgrp(pid_t pgrp)
+{
+	int fd = ttyfd;
+
+	if (fd < 0)
+		return;
+
+	xtcsetpgrp(fd, pgrp);
+}
+
 void
 setjobctl(int on)
 {
+	int pgrp = -1;
 	int fd;
-	int pgrp;
 
 	if (on == jobctl || rootshell == 0)
 		return;
@@ -207,36 +217,43 @@ setjobctl(int on)
 		fd = savefd(fd, ofd);
 		do { /* while we are in the background */
 			if ((pgrp = tcgetpgrp(fd)) < 0) {
+close:
+				close(fd);
+				fd = -1;
 out:
+				if (!iflag)
+					break;
 				sh_warnx("can't access tty; job control turned off");
 				mflag = on = 0;
-				goto close;
+				return;
 			}
 			if (pgrp == getpgrp())
 				break;
+			if (!iflag)
+				goto close;
 			killpg(0, SIGTTIN);
 		} while (1);
 		initialpgrp = pgrp;
-
-		setsignal(SIGTSTP);
-		setsignal(SIGTTOU);
-		setsignal(SIGTTIN);
 		pgrp = rootpid;
-		setpgid(0, pgrp);
-		xtcsetpgrp(fd, pgrp);
 	} else {
 		/* turning job control off */
 		fd = ttyfd;
 		pgrp = initialpgrp;
-		xtcsetpgrp(fd, pgrp);
+	}
+
+	setsignal(SIGTSTP);
+	setsignal(SIGTTOU);
+	setsignal(SIGTTIN);
+	if (fd >= 0) {
 		setpgid(0, pgrp);
-		setsignal(SIGTSTP);
-		setsignal(SIGTTOU);
-		setsignal(SIGTTIN);
-close:
-		close(fd);
-		fd = -1;
+		xtcsetpgrp(fd, pgrp);
+
+		if (!on) {
+			close(fd);
+			fd = -1;
+		}
 	}
+
 	ttyfd = fd;
 	jobctl = on;
 }
@@ -391,7 +408,7 @@ restartjob(struct job *jp, int mode)
 	jp->state = JOBRUNNING;
 	pgid = jp->ps->pid;
 	if (mode == FORK_FG)
-		xtcsetpgrp(ttyfd, pgid);
+		xxtcsetpgrp(pgid);
 	killpg(pgid, SIGCONT);
 	ps = jp->ps;
 	i = jp->nprocs;
@@ -874,7 +891,7 @@ static void forkchild(struct job *jp, union node *n, int mode)
 		/* This can fail because we are doing it in the parent also */
 		(void)setpgid(0, pgrp);
 		if (mode == FORK_FG)
-			xtcsetpgrp(ttyfd, pgrp);
+			xxtcsetpgrp(pgrp);
 		setsignal(SIGTSTP);
 		setsignal(SIGTTOU);
 	} else
@@ -1014,7 +1031,7 @@ waitforjob(struct job *jp)
 	st = getstatus(jp);
 #if JOBS
 	if (jp->jobctl) {
-		xtcsetpgrp(ttyfd, rootpid);
+		xxtcsetpgrp(rootpid);
 		/*
 		 * This is truly gross.
 		 * If we're doing job control, then we did a TIOCSPGRP which
-- 
2.11.4.GIT