lxqt-policykit crashes with general protection fault in libgobject-2.0

guiverc@dc7700-lub:~$ strace /usr/bin/lxqt-admin-user 2>lxqt-admin-user_rm_pw_admin_from_sudo.strace

On executing, there is some mouse movement as I drag window to a comfortable position, then I tried to keep movement to a minimum as I selected 'pw_admin' user, properties & tried to remove 'sudo' rights..

the strace in #2 maybe different; I cannot find

`statx(AT_FDCWD, "/usr/local/sbin`

that I can see in screen output when executed without saving output & Authentication box appears just prior to error.popup.

this is comment #2 repeated (after delay to ensure privileges were lost)

I can find

`statx(AT_FDCWD, "/usr/local/sbin/pkexec",`

on this one, which is where I suspect near/where things go wrong..

User @scro on https://discourse.lubuntu.me/t/no-authorization-after-adding-user/1033/11 indicated an opinion that it maybe a regression...

"Interestingly though, when I use a stick with version 19.10 with multiple users and do an update, everything works just fine. It doesn’t work with a new installation though."

Status changed to 'Confirmed' because the bug affects multiple users.

I can confirm this problem when a new Lubuntu 20.04 is installed.

I can confirm this issue after a fresh install of Lubuntu 20.04 on a Medion Akoya P8610, too.

I can confirm the issue after a fresh install of Lubuntu 20.04 on an old Asus X201E.

I could revert the behaviour to normal deleting adm and sudo from second user groups. It seems that Lubuntu 20.04 accepts only one admin...

synaptic starts ok with sudo (don't do this?!) but not with the desktop entry which is basically `pkexec synaptic`. So I think this supports Chris's hypothesis

I'm getting
[ 598.506741] traps: lxqt-policykit-[1687] general protection fault ip:7f1023e0f671 sp:7ffdc0298888 error:0 in libgobject-2.0.so.0.6400.3[7f1023de1000+36000]

After running `synaptic-pkexec` and enter password.

Check this bug (may be related or duplicate) - https://bugs.launchpad.net/ubuntu/+source/lxqt-policykit/+bug/1899782

I can confirm the remedie of removing all other users except one from the sudo group (see psychotrain65 from 2020-06-14):

I had two users as sudo. I removed them alternately. As long as I had only one user in sudo everything worked as expected. It did not matter which user. As soon as two users were in sudo the admin-user action failed.

Why does Lubuntu support one user in sudo only?

So the steps to reproduce this are somewhat unclear, so let me know if I did anything wrong:

 1. Boot fresh installation of Lubuntu 20.04
 2. Use lxqt-admin-user to create a second user (let's call it user2)
 3. Use lxqt-admin-user to add user2 to sudo
 4. Logout and back in again (yes, this is a requirement to reproduce— if you want, you can first remove user2's sudo and it will work, but then add it back and continue on)
 5. User lxqt-admin-user to try to remove user2's membership in the sudo group (fail)
 6. Try running pkexec against something. Since synaptic is well set up for it, this is a good example, so install synaptic and run `synaptic-pkexec` (fail)
 7. Remove user2's membership in the sudo group for sure with `sudo usermod -G "" user2`
 8. Try running the pkexec command again (success)

I did check this also against the adm group and it didn't seem to have an effect.

Anyways, I'm pretty sure the error, if anywhere, exists in lxqt-policykit. It's had like almost zero upstream issues, so that's interesting.

It's also possible this is a pkexec issue of some kind. It has caused many headaches for folks.

I'm updating my machine running off of LXQt's git master and we'll see if it behaves any better.

@wxl:

Yes, your steps to reproduce are correct. Except that I did not try it with pkexec. Instead I tried it with diskmanager, which automatically asks for root privileges. (I do not know which program it invokes.)

Well, I've confirmed this with the latest upstream sources.

BTW I happened to have an Eoan VM laying around and tested it out and found the same problem. so this has actually been long standing. We'll see what upstream says.

According to upstream this bug is fixed in lxqt-policykit 0.17.0. However, there are no Debian or Ubuntu packages to test above 0.16.0.
https://github.com/lxqt/lxqt-policykit/issues/117

This bug was fixed in the package lxqt-policykit - 0.17.0-0ubuntu1

---------------
lxqt-policykit (0.17.0-0ubuntu1) impish; urgency=medium

  * New upstream release 0.17.0 (LP: #1875774)
  * Update debian/control
    - Bump Standards-Version to 4.5.1
    - Use liblxqt0-dev 0.17.0
    - Extend lxqt-policykit-l10n package description
  * Update debian/copyright

 -- apt-ghetto <email address hidden> Fri, 13 Aug 2021 14:41:25 +0200