Bug#423014: console's last three lines become inaccessible once xdm start up
Package: xdm
Version: 1:1.1.4-3
Severity: critical
Tags: security
Justification: breaks unrelated software
When I start up xdm, the console starts to imagine that there are
three more lines available than actually exist. The console actually
has 25 lines; but the console ttys think it has 28 lines. The resize
command reports LINES=28. Even if I export LINES=25 and then fire up
screen, my shell within screen has LINES=28.
This means that I can't see the last three lines of output, once
output gets to the bottom of the screen; it means that the emacs
minibuffer and the aptitude dialog area are invisible; these don't
even scroll into view after it's too late. This makes both emacs and
aptitude almost impossible to use (hence: breaks unrelated software)
and makes it almost impossible for root to do anything (hence:
critical) if I follow the cautious policy of never letting root do
anything in a window under X. The console becomes extremely difficult
(and dangerous - see below) to use.
It means that, when dpkg is installing a package, I'm apt to be asked
some question I can't see and given a prompt I can't see and left
waiting for the program to do something, so I end up hitting return
and getting whatever the default was for the question I never saw
being asked (on account of this last, I have added "security" as a
tag); after that, dpkg begins producing more output and the entire
dialog in which I have just played my blind part scrolls into view.
Obviously, dpkg is not the only software (reportbug springs to mind)
that relies on me to respond to prompts, after producing enough output
that it's apt to be in the last three lines of the screen; nor is dpkg
the only one for which random answers to unseen prompts may result in
security-relevant disasters.
The problem is *not* that the screen is mis-sized; if I shrink
vertical on the screen, I still don't see the missing lines, though
the lines I do see now fit into a smaller vertical span on my screen.
In any case, if I suppress xdm's start-up (by adding an early exit 0
to /etc/init.d/xdm) I see normal console behaviour. It would not,
however, surprise me if the problem is really with something else (xdm
is merely triggering it); there may be some package doing something
clever with the frame-buffer (bug I don't have a logo visible on
screen). The problem *may* (but I'd be surprised) be related to the
fact that my xorg.conf Display sections say
Modes "1280x1024" "1152x864" "1024x768" "832x624" "800x600" "720x400" "640x480" "1600x1200"
with the highest-resolution last (when I put it first, xdm failed to
start up, albeit taking three tries at it before giving up; moving it
to the end lets xdm start, after which Ctrl+Alt+keypad(-) suffices to
get me to the highest resolution; leaving it on the default doesn't
help the console, though).
About three months ago, I saw this same problem, tried to find its
cause, gave up and then was surprised, upon running the euro-test
script (which failed) to find the problem had gone away. Today I
moved desks, so re-booted (for the first time since the power outage
three months ago - I love stable software ;-); and euro-test now
passes, without fixing this problem. The fact that euro-test used to
be able to fix it does imply that there must be some way to work
around the problem (I'd be delighted if anyone can identify what; I've
been carefully through euro-test without finding what it did that
solved the problem). I tried /etc/init.d/console-screen.sh, invoked
the same way euro-test was doing so three months ago, but that wasn't
what was solving the problem.
-- System Information:
Debian Release: lenny/sid
APT prefers testing
APT policy: (500, 'testing'), (500, 'stable'), (1, 'experimental')
Architecture: i386 (i686)
Kernel: Linux 2.6.18-4-686 (SMP w/2 CPU cores)
Locale: LANG=en_GB.ISO-8859-15, LC_CTYPE=en_GB.ISO-8859-15 (charmap=ISO-8859-15)
Shell: /bin/sh linked to /bin/bash
Versions of packages xdm depends on:
ii cpp 4:4.1.1-15 The GNU C preprocessor (cpp)
ii debconf [debconf-2.0] 1.5.13 Debian configuration management sy
ii libc6 2.3.6.ds1-13 GNU C Library: Shared libraries
ii libice6 1:1.0.3-2 X11 Inter-Client Exchange library
ii libpam0g 0.79-4 Pluggable Authentication Modules l
ii libselinux1 1.32-3 SELinux shared libraries
ii libsm6 1:1.0.2-2 X11 Session Management library
ii libx11-6 2:1.0.3-7 X11 client-side library
ii libxau6 1:1.0.1-2 X11 authorisation library
ii libxaw7 1:1.0.2-4 X11 Athena Widget library
ii libxdmcp6 1:1.0.2-2 X11 Display Manager Control Protoc
ii libxext6 1:1.0.1-2 X11 miscellaneous extension librar
ii libxinerama1 1:1.0.1-4.1 X11 Xinerama extension library
ii libxmu6 1:1.0.2-2 X11 miscellaneous utility library
ii libxpm4 1:3.5.5-2 X11 pixmap library
ii libxt6 1:1.0.5-2 X11 toolkit intrinsics library
ii x11-common 1:7.1.0-18 X Window System (X.Org) infrastruc
ii xbase-clients 1:7.1.ds1-2 miscellaneous X clients
xdm recommends no packages.
-- debconf information:
* shared/default-x-display-manager: xdm
xdm/stop_running_server_with_children: false
xdm/daemon_name: /usr/bin/X11/xdm
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