From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <1b38321dd9fcb942a015fd7101606737@isd.dp.ua>
To: 9fans@9fans.net
From: yaroslav <yarikos@gmail.com>
Date: Wed, 26 Jan 2011 17:16:17 +0200
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Subject: [9fans] passwd(1) over ssh fails: race in telnetd
Topicbox-Message-UUID: a16ec942-ead6-11e9-9d60-3106f5b1d025

passwd(1), while started on telnetd-simulated /dev/cons (via ssh),
gets killed for writing on closed pipe after "Confirm:" message.  I
think it is because of close()/open() race in
	/sys/src/cmd/ip/telnetd.c:/^conssim/+/open/+/consctl/.
Readln opens and closes consctl, and when two readln calls are made,
next open may be attempted before the daemon reopens of its end of the
simulated consctl.

A fast workaround is injection of sleep(100) between readln calls in
/sys/src/cmd/auth/passwd.c:102.

Suggestions for the proper fix?

- Iaroslav