From 59e038c9d15770323be23f4f12087bdf43db7a7b Mon Sep 17 00:00:00 2001
From: Seiichi Ishitsuka <ishitsuka.sc@ncos.nec.co.jp>
Date: Tue, 29 May 2018 11:43:25 +0900
Subject: [PATCH] netkit-telnet: Fix deadlock on cleanup

Signed-off-by: Seiichi Ishitsuka <ishitsuka.sc@ncos.nec.co.jp>
---
 .../0001-telnetd-Fix-deadlock-on-cleanup.patch     | 107 +++++++++++++++++++++
 .../netkit-telnet/netkit-telnet_0.17.bb            |   1 +
 2 files changed, 108 insertions(+)
 create mode 100644 meta-networking/recipes-netkit/netkit-telnet/files/0001-telnetd-Fix-deadlock-on-cleanup.patch

diff --git a/meta-networking/recipes-netkit/netkit-telnet/files/0001-telnetd-Fix-deadlock-on-cleanup.patch b/meta-networking/recipes-netkit/netkit-telnet/files/0001-telnetd-Fix-deadlock-on-cleanup.patch
new file mode 100644
index 0000000..d6873a5
--- /dev/null
+++ b/meta-networking/recipes-netkit/netkit-telnet/files/0001-telnetd-Fix-deadlock-on-cleanup.patch
@@ -0,0 +1,107 @@
+From cdf8829f743adb3ec72c231ee5843dabed91b30f Mon Sep 17 00:00:00 2001
+From: Seiichi Ishitsuka <ishitsuka.sc@ncos.nec.co.jp>
+Date: Tue, 8 May 2018 09:53:34 +0900
+Subject: [PATCH] telnetd:Fix deadlock on cleanup
+
+the patch comes from:
+https://launchpadlibrarian.net/37882973/0001-telnetd-Fix-deadlock-on-cleanup.patch
+
+The cleanup function in telnetd is called both directly and on SIGCHLD
+signals. This, unfortunately, triggered a deadlock in glibc 2.2 while
+running on a 4.4.32 kernel.
+
+What we were seeing is hangs like these:
+
+(gdb) bt
+ #0  0x489fee6c in __lll_lock_wait_private (futex=0x48a5e9a4 <__libc_utmp_lock>) at ./lowlevellock.c:33
+ #1  0x48a27934 in __utmpname (file=0x48ac1278 "/var/run/utmp") at utmpname.c:42
+ #2  0x48ac0ec0 in logout (line=0x27e9d "pts/11") at logout.c:32
+
+How to reproduce:
+
+Run the script more than once in the background.
+
+ #!/bin/sh
+
+ HOST="host.target"
+ USER="root"
+ PASS="password"
+
+ while :
+ do
+   expect -c "
+   set timeout 10
+   spawn telnet $HOST
+   expect login:\  ; send \"$USER\r\"
+   expect sword:\  ; send \"$PASS\r\"
+   expect \"# \" ; send \"exit\r\"
+ " > /dev/null
+ done
+
+Signed-off-by: Seiichi Ishitsuka <ishitsuka.sc@ncos.nec.co.jp>
+---
+ telnetd/ext.h      |  1 +
+ telnetd/sys_term.c | 17 ++++++++++++++++-
+ telnetd/telnetd.c  |  2 +-
+ 3 files changed, 18 insertions(+), 2 deletions(-)
+
+diff --git a/telnetd/ext.h b/telnetd/ext.h
+index b98d6ec..08f9d07 100644
+--- a/telnetd/ext.h
++++ b/telnetd/ext.h
+@@ -97,6 +97,7 @@ void add_slc(int, int, int);
+ void check_slc(void);
+ void change_slc(int, int, int);
+ void cleanup(int);
++void cleanup_sighandler(int);
+ void clientstat(int, int, int);
+ void copy_termbuf(char *, int);
+ void deferslc(void);
+diff --git a/telnetd/sys_term.c b/telnetd/sys_term.c
+index 5b4aa84..c4fb0f7 100644
+--- a/telnetd/sys_term.c
++++ b/telnetd/sys_term.c
+@@ -719,7 +719,7 @@ static void addarg(struct argv_stuff *avs, const char *val) {
+  * This is the routine to call when we are all through, to
+  * clean up anything that needs to be cleaned up.
+  */
+-void cleanup(int sig) {
++void cleanup_sighandler(int sig) {
+     char *p;
+     (void)sig;
+ 
+@@ -742,3 +742,18 @@ void cleanup(int sig) {
+     shutdown(net, 2);
+     exit(0);
+ }
++
++void cleanup(int sig) {
++    sigset_t mask, oldmask;
++
++    /* Set up the mask of signals to temporarily block. */
++    sigemptyset (&mask);
++    sigaddset (&mask, SIGCHLD);
++
++    /* Block SIGCHLD while running cleanup */
++    sigprocmask (SIG_BLOCK, &mask, &oldmask);
++
++    cleanup_sighandler(sig);
++    /* Technically not needed since cleanup_sighandler exits */
++    sigprocmask (SIG_UNBLOCK, &mask, NULL);
++}
+diff --git a/telnetd/telnetd.c b/telnetd/telnetd.c
+index 9ace838..788919c 100644
+--- a/telnetd/telnetd.c
++++ b/telnetd/telnetd.c
+@@ -833,7 +833,7 @@ void telnet(int f, int p)
+     signal(SIGTTOU, SIG_IGN);
+ #endif
+     
+-    signal(SIGCHLD, cleanup);
++    signal(SIGCHLD, cleanup_sighandler);
+     
+ #ifdef TIOCNOTTY
+     {
+-- 
+2.6.4
+
diff --git a/meta-networking/recipes-netkit/netkit-telnet/netkit-telnet_0.17.bb b/meta-networking/recipes-netkit/netkit-telnet/netkit-telnet_0.17.bb
index 807b566..e1566f8 100644
--- a/meta-networking/recipes-netkit/netkit-telnet/netkit-telnet_0.17.bb
+++ b/meta-networking/recipes-netkit/netkit-telnet/netkit-telnet_0.17.bb
@@ -11,6 +11,7 @@ SRC_URI = "ftp://ftp.uk.linux.org/pub/linux/Networking/netkit/${BP}.tar.gz \
            file://telnet-xinetd \
            file://cross-compile.patch \
            file://0001-telnet-telnetd-Fix-print-format-strings.patch \
+           file://0001-telnetd-Fix-deadlock-on-cleanup.patch \
            "
 
 EXTRA_OEMAKE = "INSTALLROOT=${D} SBINDIR=${sbindir} DAEMONMODE=755 \
-- 
1.8.3.1