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bugzilla-daemon at mindrot.org

2013-Oct-08 18:39 UTC

[Bug 2158] New: Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

            Bug ID: 2158
           Summary: Race condition in receiving SIGTERM
           Product: Portable OpenSSH
           Version: 6.2p1
          Hardware: All
                OS: Linux
            Status: NEW
          Severity: minor
          Priority: P5
         Component: sshd
          Assignee: unassigned-bugs at mindrot.org
          Reporter: ben.maurer at gmail.com

To handle sigterm, openssh uses this handler:

static void
sigterm_handler(int sig)
{
    received_sigterm = sig;
}

in the select loop, it checks this flag

ret = select(maxfd+1, fdset, NULL, NULL, NULL);
...
if (received_sigterm) {


select() will return -1 with an EINTR when it gets a signal. Therefore,
in most cases this successfully shuts down the process. However, if SSH
were executing something other than this select call (eg, accepting a
new connection) it would never notice the sigterm until a new event
came in.

This created a race condition in a large, real world deployment. The
default init script in the openssh package sends a SIGTERM in order to
kill the process. On a small fraction of servers, the race condition
mentioned here occurred. The new openssh process was launched while the
old one still ran. When the new process attempted to bind() to a port,
it failed.

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bugzilla-daemon at mindrot.org

2013-Oct-08 18:44 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

--- Comment #1 from Ben Maurer <ben.maurer at gmail.com> ---
Some potential strategies that come to mind to prevent this:

(1) handle the termination in the signal handler. The signal handler
doesn't appear to use malloc, it just closes the listening ports and
removes the PID file. This could be done inside the signal handler

(2) Create a pipe which signal handlers can write to in order to wake
up the select loop.

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bugzilla-daemon at mindrot.org

2014-Jan-04 12:11 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

Tiago Cunha <tcunha at gmx.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tcunha at gmx.com

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bugzilla-daemon at mindrot.org

2014-Jul-03 04:58 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |djm at mindrot.org
             Blocks|                            |2226

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bugzilla-daemon at mindrot.org

2014-Aug-29 18:38 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |2266

--- Comment #2 from Damien Miller <djm at mindrot.org> ---
Retarget incomplete bugs to 6.8 release.

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bugzilla-daemon at mindrot.org

2014-Aug-29 18:40 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|2226                        |

--- Comment #3 from Damien Miller <djm at mindrot.org> ---
These bugs are no longer targeted at the imminent 6.7 release

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bugzilla-daemon at mindrot.org

2015-Mar-02 20:59 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|2266                        |

--- Comment #4 from Damien Miller <djm at mindrot.org> ---
OpenSSH 6.8 is approaching release and closed for major work. Retarget
these bugs for the next release.

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bugzilla-daemon at mindrot.org

2015-Mar-02 21:01 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |2360

--- Comment #5 from Damien Miller <djm at mindrot.org> ---
Retarget to 6.9

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bugzilla-daemon at mindrot.org

2015-Jun-05 03:57 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|2360                        |2403

--- Comment #6 from Damien Miller <djm at mindrot.org> ---
Retarget to 7.0 release, we'll probably add a notification fd

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bugzilla-daemon at mindrot.org

2015-Aug-11 12:59 UTC

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[Bug 2158] Race condition in receiving SIGTERM

https://bugzilla.mindrot.org/show_bug.cgi?id=2158

Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |2443

--- Comment #7 from Damien Miller <djm at mindrot.org> ---
Retarget pending bugs to openssh-7.1

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bugzilla-daemon at mindrot.org

2015-Aug-11 13:00 UTC

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