SSHD causes 100% CPU load

[Corinna Vinschen]

On Aug  5 19:12, Takashi Yano via Cygwin wrote:
> Hi everyone,
> 
> On Wed, 28 Apr 2021 07:23:02 +0300
> Andrey Repin <anrdaemon@yandex.ru> wrote:
> 
> > Greetings, Christoph Lüders!
> > 
> > > I run cygwin 32-bit on Windows 10 Pro Build 19042.  Cygwin is 3.2.0-1,
> > > openssh is 8.5p1-1.
> > 
> > > I use sshd to access the machine from afar.  I notice (often multiple)
> > > processes of sshd.exe with 100% CPU load.
> > 
> > https://cygwin.com/pipermail/cygwin/2021-April/248299.html
> > https://cygwin.com/pipermail/cygwin/2021-April/248309.html
> > 
> > > A stack shown with procexp has function names like
> > > "cygwin1.dll!acl_get_perm" and "cygwin1.dll!_assert".
> > 
> > > Can anyone give me some advice how to proceed further?  I have updated
> > > to the latest cygwin multiple times; reboot doesn't help either.
> 
> I have finally found how to reproduce this problem in my
> environment. The reproduce steps are as follows.
> 
> 1. Install cygwin sshd as a service and start it.
> 2. Connect to sshd by 'ssh user@localhost ls' using **Windows** ssh.exe.
> 3. Check if sshd remains with high CPU load.
> 
> I have confirmed that this issue happens in a few my PCs.
> 
> Corinna, could you please have a look?

Could you perhaps bisect the issue on your machine?

The fact that using Windows ssh is an issue makes me wonder if this is
some kind of pty problem.

The stack info seems fishy to me.  sshd doesn't use any ACL functions.


Corinna