gsd-power 3.27.91 crashed with SIGFPE

[Jeremy Bícha]

Test Case
=========
From Ubuntu 18.04, add the GNOME3 Staging PPA.
Log out and log back in.

Open gnome-control-center to the Power panel.
Close gnome-control-center
Open gnome-control-center

(gnome-control-center 3.27.91 will automatically open the last opened panel, which is Power here).

gnome-settings-daemon crashes which crashes the entire session and logs you out.

Other Info
==========
The GNOME3 Staging PPA has gnome-control-center 3.27.90.

I could not reproduce this crash with bionic's gnome-settings-daemon 3.26.2.

I was still able to reproduce the crash after applying this patch:
https://gitlab.gnome.org/GNOME/gnome-settings-daemon/commit/a72c928a

ProblemType: Crash
DistroRelease: Ubuntu 18.04
Package: gnome-settings-daemon 3.27.91-0ubuntu0~bionic1 [origin: LP-PPA-gnome3-team-gnome3-staging]
ProcVersionSignature: Ubuntu 4.15.0-10.11-generic 4.15.3
Uname: Linux 4.15.0-10-generic x86_64
ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Mon Feb 26 19:42:15 2018
ExecutablePath: /usr/lib/gnome-settings-daemon/gsd-power
InstallationDate: Installed on 2017-10-13 (136 days ago)
InstallationMedia: Ubuntu 17.10 "Artful Aardvark" - Beta amd64 (20171012)
ProcCmdline: /usr/lib/gnome-settings-daemon/gsd-power
Signal: 8
SourcePackage: gnome-settings-daemon
StacktraceTop:
 ()
 ()
 () at /usr/lib/x86_64-linux-gnu/libgio-2.0.so.0
 g_main_context_dispatch () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
 () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
Title: gsd-power crashed with SIGFPE
UpgradeStatus: Upgraded to bionic on 2017-11-24 (94 days ago)
UserGroups: adm cdrom dip lpadmin lxd plugdev sambashare sbuild sudo

[Tim Lunn (darkxst)]

Reproduced as per test case.
Here is a backtrace:

Core was generated by `/usr/lib/gnome-settings-daemon/gsd-power'.
Program terminated with signal SIGFPE, Arithmetic exception.
#0 0x000056134e7068d8 in gsd_power_backlight_abs_to_percentage (
    min=min@entry=0, max=<optimised out>, value=<optimised out>)
    at ../plugins/power/gpm-common.c:61
61 ../plugins/power/gpm-common.c: No such file or directory.
[Current thread is 1 (Thread 0x7f49b27d80c0 (LWP 2070))]
(gdb) bt
#0 0x000056134e7068d8 in gsd_power_backlight_abs_to_percentage (
    min=min@entry=0, max=<optimised out>, value=<optimised out>)
    at ../plugins/power/gpm-common.c:61
#1 0x000056134e70c207 in handle_get_property_other (error=0x0,
    property_name=0x561350569bd0 "Brightness",
    interface_name=0x561350569480 "org.gnome.SettingsDaemon.Power.Keyboard",
    manager=0x561350568150) at ../plugins/power/gsd-power-manager.c:2924
#2 handle_get_property (connection=<optimised out>, sender=<optimised out>,
    object_path=object_path@entry=0x7f4998011ad0 "/org/gnome/SettingsDaemon/Power",
    interface_name=interface_name@entry=0x561350569480 "org.gnome.SettingsDaemon.Power.Keyboard",
    property_name=property_name@entry=0x561350569bd0 "Brightness",
    error=error@entry=0x0, user_data=0x561350568150)
    at ../plugins/power/gsd-power-manager.c:2957
#3 0x00007f49b0d8caf8 in invoke_get_all_properties_in_idle_cb (
    _data=0x7f499803b920) at ../../../../gio/gdbusconnection.c:4494
#4 0x00007f49b07aef85 in g_main_dispatch (context=0x56135052e800)
    at ../../../../glib/gmain.c:3177
#5 g_main_context_dispatch (context=context@entry=0x56135052e800)
    at ../../../../glib/gmain.c:3830
#6 0x00007f49b07af350 in g_main_context_iterate (context=0x56135052e800,
    block=block@entry=1, dispatch=dispatch@entry=1, self=<optimised out>)
---Type <return> to continue, or q <return> to quit---
   ../../../glib/gmain.c:3903
#7 0x00007f49b07af662 in g_main_loop_run (loop=0x561350595b10) at ../../../../glib/gmain.c:4099
#8 0x00007f49b15a9455 in gtk_main () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0
#9 0x000056134e705fca in main (argc=<optimised out>, argv=<optimised out>) at ../plugins/common/daemon-skeleton-gtk.h:246

[Tim Lunn (darkxst)]

I can not reproduce this on my laptop that actually has a backlit keyboard, so suspect it only affects machines without.

Could be a divide-by-0 error, though the code seems to guard against that.

[Tim Lunn (darkxst)]

I poked at this with gdb:
#0 gsd_power_backlight_abs_to_percentage (min=min@entry=0, max=0, value=-1) at ../plugins/power/gpm-common.c:61

that should trigger g_return_val_if_fail (max > min, -1) to return, however the g_return_val_if_fail's seem to have been compiled out ;(

I will file an upstream bug for this

[Tim Lunn (darkxst)]

https://gitlab.gnome.org/GNOME/gnome-settings-daemon/issues/8

seems Launchpad hasnt learnt about gitlab URL's yet?

[Jeremy Bícha (jbicha)]

Here's the Launchpad bug for GitLab bugs: LP: #1745210 (I believe no one's working on it yet.)