[Bug 1056756] Re: sshd: preauth child terminated by signal 11

[Serge Hallyn]

Can you please post /etc/ssh/sshd_config, /etc/pamd./sshd on the server?
Is there anything in /var/log/syslog or /var/log/kern.log?

If you have admin rights on the server, you could determine the exact
location of the segfault by installing the openssh-server-dbgsym package
as described in https://wiki.ubuntu.com/DebuggingProgramCrash.

** Changed in: openssh (Ubuntu)
   Importance: Undecided => High

** Changed in: openssh (Ubuntu)
       Status: New => Incomplete

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Title:
  sshd: preauth child terminated by signal 11

Status in “openssh” package in Ubuntu:
  Incomplete

Bug description:
  Can't connect to a local installation of openssh-server.

  ssh localhost fails with "Broken pipe", here's the tail of ssh -vv:

  ...
  debug1: Enabling compression at level 6.
  debug1: Authentication succeeded (publickey).
  Authenticated to localhost ([127.0.0.1]:22).
  debug1: channel 0: new [client-session]
  debug2: channel 0: send open
  debug1: Requesting no-more-sessions at openssh.com
  debug1: Entering interactive session.
  Write failed: Broken pipe

  Those lines are appearing in auth.log:

  Sep 26 14:09:10 natali sshd[6076]: Accepted publickey for wiz from 127.0.0.1 port 48624 ssh2
  Sep 26 14:09:10 natali sshd[6076]: fatal: privsep_preauth: preauth child terminated by signal 11

  Also, any ssh invocation (even -h) ends with "Segmentation fault":

  usage: ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec]
             [-D [bind_address:]port] [-e escape_char] [-F configfile]
             [-I pkcs11] [-i identity_file]
             [-L [bind_address:]port:host:hostport]
             [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]
             [-R [bind_address:]port:host:hostport] [-S ctl_path]
             [-W host:port] [-w local_tun[:remote_tun]]
             [user@]hostname [command]
  Segmentation fault

  ProblemType: Bug
  DistroRelease: Ubuntu 12.10
  Package: openssh-server 1:6.0p1-3ubuntu1
  ProcVersionSignature: Ubuntu 3.5.0-15.22-generic 3.5.4
  Uname: Linux 3.5.0-15-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 2.5.2-0ubuntu4
  Architecture: amd64
  Date: Wed Sep 26 14:01:24 2012
  InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120724.2)
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SSHDConfig: Error: command ['pkexec', '/usr/sbin/sshd', '-T'] failed with exit code -11:
  SourcePackage: openssh
  UpgradeStatus: No upgrade log present (probably fresh install)

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