Bug 3411 - 8.9 regression: "ssh -XAf localhost xeyes" uses 100% CPU
Summary: 8.9 regression: "ssh -XAf localhost xeyes" uses 100% CPU
Status: CLOSED DUPLICATE of bug 3405
Alias: None
Product: Portable OpenSSH
Classification: Unclassified
Component: ssh (show other bugs)
Version: 8.9p1
Hardware: Other Linux
: P5 normal
Assignee: Assigned to nobody
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2022-03-22 19:51 AEDT by harri
Modified: 2022-04-08 12:12 AEST (History)
2 users (show)

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Description harri 2022-03-22 19:51:24 AEDT 
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
Comment 1 harri 2022-03-22 19:56:34 AEDT 
Better command line to reproduce the problem:

xterm -e 'ssh -XAf localhost xeyes'
Comment 2 Damien Miller 2022-03-23 10:43:14 AEDT 
I couldn't reproduce this, but does the patch attached to bug #3405 help? https://bugzilla.mindrot.org/attachment.cgi?id=3581
Comment 3 harri 2022-03-23 17:11:28 AEDT 
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.
Comment 4 Damien Miller 2022-03-31 08:26:54 AEDT 

*** This bug has been marked as a duplicate of bug 3405 ***
Comment 5 Damien Miller 2022-04-08 12:12:54 AEST 
closing bug resolved during openssh-9.0 release cycle