openssh bugs - Mar 2022 - [Bug 3411] New: 8.9 regression: "ssh -XAf localhost xeyes" uses 100% CPU

https://bugzilla.mindrot.org/show_bug.cgi?id=3411

            Bug ID: 3411
           Summary: 8.9 regression: "ssh -XAf localhost xeyes" uses
100%
                    CPU
           Product: Portable OpenSSH
           Version: 8.9p1
          Hardware: Other
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P5
         Component: ssh
          Assignee: unassigned-bugs at mindrot.org
          Reporter: harri at afaics.de

Hi folks,

a simple ssh command like

        ssh -XAf localhost xeyes

uses 100% CPU when the terminal goes away. There is no such problem for
openssh 8.8 (or for using nohup).

Same problem for other apps instead of xeyes (e.g. xterm) and for
remote hosts instead of localhost.

configure command line:

./configure --prefix=/usr/local/stow/openssh-8.9p1
--with-privsep-path=/tmp/empty

I got the same problem using Debian's ssh client, see
https://bugs.debian.org/1007822


Regards

Harri

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--- Comment #1 from harri at afaics.de ---
Better command line to reproduce the problem:

xterm -e 'ssh -XAf localhost xeyes'

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Damien Miller <djm at mindrot.org> changed:

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

--- Comment #2 from Damien Miller <djm at mindrot.org> ---
I couldn't reproduce this, but does the patch attached to bug #3405
help? https://bugzilla.mindrot.org/attachment.cgi?id=3581

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--- Comment #3 from harri at afaics.de ---
Seems to be an improvement. The high CPU load is gone. strace shows
that ssh isn't polling anymore. Moving back to the old ssh: Problem is
back.

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post+bugzilla.mindrot.org at ralfj.de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |post+bugzilla.mindrot.org at r
                   |                            |alfj.de

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #4 from Damien Miller <djm at mindrot.org> ---


*** This bug has been marked as a duplicate of bug 3405 ***

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Damien Miller <djm at mindrot.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |CLOSED

--- Comment #5 from Damien Miller <djm at mindrot.org> ---
closing bug resolved during openssh-9.0 release cycle

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