SSHD causes 100% CPU load

[Takashi Yano]

On Fri, 6 Aug 2021 11:11:05 +0200
Corinna Vinschen wrote:
> On Aug  6 10:55, Takashi Yano via Cygwin wrote:
> > Hi Corinna,
> > 
> > On Fri, 6 Aug 2021 01:43:31 +0900
> > Takashi Yano wrote:
> > > Hi Corinna,
> > > 
> > > On Thu, 5 Aug 2021 17:07:24 +0200
> > > Corinna Vinschen wrote:
> > > > Could you perhaps bisect the issue on your machine?
> > > 
> > > In my environment, this does not happen with 8.4p1-1 and 8.4p1-2.
> > > However it happens with 8.5p1-1.
> > > [...]
> > I looked into the openssh code and might find a calprit.
> > I guess the following patch solves the issue.
> > 
> > --- serverloop.c.orig	2021-03-02 19:31:47.000000000 +0900
> > +++ serverloop.c	2021-08-06 10:41:55.439357200 +0900
> > @@ -333,7 +333,7 @@
> >  			return -1;
> >  		} else if (len == -1) {
> >  			if (errno == EINTR || errno == EAGAIN ||
> > -			    errno != EWOULDBLOCK)
> > +			    errno == EWOULDBLOCK)
> >  				return 0;
> >  			verbose("Read error from remote host %s port %d: %s",
> >  			    ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
> > 
> > 
> > This seems to be a upstream bug which has been already fixed.
> > 
> > Please refer to:
> > https://github.com/openssh/openssh-portable/commit/2dc328023f60212cd29504fc05d849133ae47355
> 
> Gosh, looks like I totally missed the 8.6p1 release!
> 
> I'll build and upload 8.6p1 ASAP.

I have confirmed that the issue has been fixed in 8.6p1-1.

Thansk.

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>