[Bug 1306877] [NEW] sshd stops accepting new connections after configuration reload

[TAKAHASHI Shuhei]

Public bug reported:

When upstart is enabled, sshd stops accepting new connections after
reloading configuration by "initctl reload ssh".

It looks like sshd is frozen with SIGSTOP after receiving SIGHUP.

[nya at sora ~]% ps auxww | grep sshd
root     10557  0.0  0.1  61364  3056 ?        Ss   13:46   0:00 /usr/sbin/sshd -D
[nya at sora ~]% sudo strace -p 10557
Process 10557 attached
select(7, [3 4], NULL, NULL, NULL^CProcess 10557 detached
 <detached ...>
[nya at sora ~]% sudo reload ssh
[nya at sora ~]% sudo strace -p 10557
Process 10557 attached
--- stopped by SIGSTOP ---

I guess it's caused by a Debian-specific patch:
debian/patches/sigstop.patch. The patch makes sshd STOP when it's ready
to start and have upstart resume it by specifying "expect stop" in
/etc/init/ssh.conf. On receiving SIGHUP sshd re-executes itself and
STOPs again, but upstart does not perform resume.

Reproduced under Ubuntu 14.04 Trusty
Package version: openssh 1:6.6p1-2

** Affects: openssh (Ubuntu)
     Importance: Undecided
         Status: New

-- 
You received this bug notification because you are a member of Ubuntu
Foundations Bugs, which is subscribed to openssh in Ubuntu.
https://bugs.launchpad.net/bugs/1306877

Title:
  sshd stops accepting new connections after configuration reload

Status in “openssh” package in Ubuntu:
  New

Bug description:
  When upstart is enabled, sshd stops accepting new connections after
  reloading configuration by "initctl reload ssh".

  It looks like sshd is frozen with SIGSTOP after receiving SIGHUP.

  [nya at sora ~]% ps auxww | grep sshd
  root     10557  0.0  0.1  61364  3056 ?        Ss   13:46   0:00 /usr/sbin/sshd -D
  [nya at sora ~]% sudo strace -p 10557
  Process 10557 attached
  select(7, [3 4], NULL, NULL, NULL^CProcess 10557 detached
   <detached ...>
  [nya at sora ~]% sudo reload ssh
  [nya at sora ~]% sudo strace -p 10557
  Process 10557 attached
  --- stopped by SIGSTOP ---

  I guess it's caused by a Debian-specific patch:
  debian/patches/sigstop.patch. The patch makes sshd STOP when it's
  ready to start and have upstart resume it by specifying "expect stop"
  in /etc/init/ssh.conf. On receiving SIGHUP sshd re-executes itself and
  STOPs again, but upstart does not perform resume.

  Reproduced under Ubuntu 14.04 Trusty
  Package version: openssh 1:6.6p1-2

To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/1306877/+subscriptions