From 68e14d3d5f4116ad3aca0e392d008645ea90cf70 Mon Sep 17 00:00:00 2001
From: Goldwyn Rodrigues <rgoldwyn@suse.com>
Date: Fri, 8 Dec 2023 09:04:39 -0600
Subject: [PATCH] more: exit if POLLERR and POLLHUP on stdin is received

more command continues to run in case stdin have closed the file and it
takes 100% of CPU. This is because revents on stdin send
POLLIN | POLLHUP | POLLERR once stdin is closed. more receives it even
though it is not requested in events. This is common Linux behaviour to
never mask out POLLHUP or POLLERR. The loop in more_key_command() runs
infinitely because more_poll() returns 0 and read_command() reads 0
bytes.

Check for POLLERR and POLLHUP, and exit more in case of an error.

Steps to reproduce:
1. Setup /etc/systemd/logind.conf with KillUserProcesses=no
2. Add config "Defaults use_pty" in /etc/sudoers
3. Start an ssh session to the machine
4. # sudo su -
5. # more <big enough file>
6. kill the parent ssh process, say close the tab

At this time "more" runs with 100% CPU utilization.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 text-utils/more.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/text-utils/more.c b/text-utils/more.c
index d4db3d5eb..a49acbc3e 100644
--- a/text-utils/more.c
+++ b/text-utils/more.c
@@ -1392,6 +1392,11 @@ static int more_poll(struct more_control *ctl, int timeout)
 			abort();
 		}
 	}
+
+	/* Check for POLLERR and POLLHUP in stdin revents */
+	if ((pfd[1].revents & POLLERR) && (pfd[1].revents & POLLHUP))
+		more_exit(ctl);
+
 	if (pfd[1].revents == 0)
 		return 1;
 	return 0;
-- 
2.33.0

