Firejail on Kubuntu 21.10 not working (missing SUID bit)

[MrFrank17]

Description

After upgrading from Kubuntu 21.04 to Kubuntu 21.10 firejail is not working anymore

Steps to Reproduce

What I tried so far:
sudo firecfg --clean and sudo firecfg to recreate the symlinks.
However starting a firejailed program, even as firejail --noprofile kate gets me the message:

Error mkdir: util.c:1019 create_empty_dir_as_root: Permission denied

This does not work as well - so maybe something is wrong with the Kubuntu setup? However creating symlinks as root worked beforehand.
firejail --version

Error mkdir: util.c:1019 create_empty_dir_as_root: Permission denied

Thanks!

[rusty-snake]

Can you run firejail --noprofile --debug true to see where it dies.

[MrFrank17]

Same effect:

firejail --noprofile --debug true kate
Error mkdir: util.c:1019 create_empty_dir_as_root: Permission denied

[rusty-snake]

If I'm right, this happens at main->preproc_build_firejail_dir->create_empty_dir_as_root.
Has there anything changed in ubu with /run? I don't think so. Sounds more like #4367 maybe. What does ls -l /usr/bin/firejail show?

How did you installed firejail?

[MrFrank17]

That's the output:

ls -l /usr/bin/firejail -rwxr-xr-x 1 root root 458416 Feb 27 2021 /usr/bin/firejail

I installed it with the old version of the distribution, 21.04 or even before - I guess I used KDE Discover back then

[rusty-snake]

I installed it with the old version of the distribution, 21.04 or even before - I guess I used KDE Discover back then

From the package sources or from the PPA or from the website?

-rwxr-xr-x

#4367 (comment)

[MrFrank17]

From the official Ubuntu repository.

Setting SUID worked!

Thanks