Bug 39128 (openssh_hang)

From Bugzilla Helper:
User-Agent: Mozilla/4.73 [en] (X11; U; Linux 2.2.19 i586)

Description of problem:


How reproducible:
Always

Steps to Reproduce:
1. ssh somehost
2. sleep 20&
3. exit
	

Additional info:

I have developed a patch to fix the notorious hanging bug when exiting from
recent versions of open-ssh in the presence of active background processes.

There has been alot of frustration and misinformation about this bug posted
on the net (eg. see RedHat's openssh-closing.txt from
openssh-2.5.2p2-5.src.rpm).  The supposed workaround "shopt -s huponexit"
mentioned in the openssh FAQ apparently only works with bash2, not with
bash1.

In any case huponexit is not a workaround at all: it is frequently
desirable to
launch a long simulation in the background and then log out, leaving the
program running in the background. Normally, backgrounded processes should
not be killed by ssh.

Below I have attached a new patch (to openssh-2.9p1) that doesn't appear to
break ssh or scp, unlike previous attempts in openssh-2.3.0p1. It passes
repeated tests of the form (bash syntax) on both linux-i386 and linux-alpha
architectures running RedHat 6.2:

while [ 1 ] ; do \
	ssh somehost "dd if=/dev/zero bs=8192 count=10" | wc -c ; \
done

-- John Bowman

diff -ur openssh-2.9p1/clientloop.c openssh-2.9p1J/clientloop.c
--- openssh-2.9p1/clientloop.c	Fri Apr 20 06:50:51 2001
+++ openssh-2.9p1J/clientloop.c	Wed May  2 16:21:16 2001
@@ -440,9 +440,13 @@
 		len = read(connection_in, buf, sizeof(buf));
 		if (len == 0) {
 			/* Received EOF.  The remote host has closed the connection. */
-			snprintf(buf, sizeof buf, "Connection to %.300s closed by remote
host.\r\n",
-				 host);
-			buffer_append(&stderr_buffer, buf, strlen(buf));
+/* 
+ * This message duplicates the one already in client_loop().
+ *
+ *			snprintf(buf, sizeof buf, "Connection to %.300s closed by remote
host.\r\n",
+ *				 host);
+ *			buffer_append(&stderr_buffer, buf, strlen(buf));
+ */			
 			quit_pending = 1;
 			return;
 		}
diff -ur openssh-2.9p1/nchan.c openssh-2.9p1J/nchan.c
--- openssh-2.9p1/nchan.c	Tue Apr  3 07:02:48 2001
+++ openssh-2.9p1J/nchan.c	Wed May  2 16:19:11 2001
@@ -56,7 +56,7 @@
 
 /* helper */
 static void	chan_shutdown_write(Channel *c);
-static void	chan_shutdown_read(Channel *c);
+void		chan_shutdown_read(Channel *c);
 
 /*
  * SSH1 specific implementation of event functions
@@ -479,7 +479,7 @@
 		c->wfd = -1;
 	}
 }
-static void
+void
 chan_shutdown_read(Channel *c)
 {
 	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
diff -ur openssh-2.9p1/nchan.h openssh-2.9p1J/nchan.h
--- openssh-2.9p1/nchan.h	Sun Mar  4 23:16:12 2001
+++ openssh-2.9p1J/nchan.h	Wed May  2 16:19:11 2001
@@ -88,4 +88,5 @@
 
 void    chan_init_iostates(Channel * c);
 void	chan_init(void);
+void	chan_shutdown_read(Channel *c);
 #endif
diff -ur openssh-2.9p1/session.c openssh-2.9p1J/session.c
--- openssh-2.9p1/session.c	Wed Apr 18 09:29:34 2001
+++ openssh-2.9p1J/session.c	Wed May  2 16:20:04 2001
@@ -1960,6 +1960,8 @@
 	 */
 	if (c->ostate != CHAN_OUTPUT_CLOSED)
 		chan_write_failed(c);
+	if (c->istate != CHAN_INPUT_CLOSED)
+		chan_shutdown_read(c);
 	s->chanid = -1;
 }