[systemd-devel] WSL Ubuntu creates XDG_RUNTIME_DIR with incorrect permissions

Wed Nov 29 21:50:57 UTC 2023

On Wed, Nov 29, 2023, 20:59 Thomas Larsen Wessel <mrvelle at gmail.com> wrote:

> Thanks both of you! :)
>
> I have taken some time to digest your answers. And in particular I have
> tried to investigate this line closer:
>
> *Nov 27 12:34:22 tumbleweed unknown: WSL (2): Creating login session for
> andrei*
>
> I have found the equivalent log line on my WSL Ubuntu. I was hoping I
> could find out more about where its coming from; ie which process / service
> prints this. But journalctl does not tell me much about the origin.
>
>
>
>
>
>
>
>
>
>
> *journalctl -b --grep "Creating login session for velle" -o verboseWed
> 2023-11-29 18:41:19.982271 CET
> [s=d318bdab5d1f4ad7a48a947e6fff4a01;i=2d53;b=c8682ff139cf40da8326fd63d7c34d7c;m=1649>
>   _TRANSPORT=kernel    _MACHINE_ID=967980c77d4743298ceaeb5d512bf388
> _HOSTNAME=ELCON45223    PRIORITY=6    SYSLOG_FACILITY=1    MESSAGE=WSL (2):
> Creating login session for velle
> _BOOT_ID=c8682ff139cf40da8326fd63d7c34d7c
> _SOURCE_MONOTONIC_TIMESTAMP=23368229*
>
> Most log entries in journalctl has a _PID field, but some don't, and this
> one does not. Why? What does it tell, that a log entry has no _PID? As far
> as I know ever process has an PID, even systemd itself has a PID (which is
> always 1). Or am I wrong about that? I see now reason why those PIDs are
> not saved together with the log entries.
>

According to _TRANSPORT the message went through the kernel log (dmesg),
i.e. it was either kernel-generated (no PID) or it was written by the
process to /dev/kmsg (PID information not preserved) rather than being sent
the usual way through syslog. There might have been a PID but journald had
no way to obtain it.

That aside, another thing about WSL2 is that the entire VM actually boots a
"system distro" first and the user-facing Ubuntu distro is started as a
container. So there are several processes that run within the VM but exist
outside of the container's PID namespace and therefore don't have PIDs from
the Ubuntu container's PoV; only the "host" namespace has PIDs for them.

(Consider how a container's "PID 1" looks from outside the container...)

>
>
> On Mon, Nov 27, 2023 at 10:37 AM Andrei Borzenkov <arvidjaar at gmail.com>
> wrote:
>
>> On Mon, Nov 27, 2023 at 1:06 AM Thomas Larsen Wessel <mrvelle at gmail.com>
>> wrote:
>> >>
>> >> WSL does not use systemd by default.
>> >
>> >
>> > According to this article, it systemd has been default on WSL Ubuntu
>> since june 2023. https://learn.microsoft.com/en-us/windows/wsl/systemd
>> >
>> > "Systemd is now the default for the current version of Ubuntu that will
>> be installed using the wsl --install command default."
>> >
>> > Also when I look in the /var/log/auth.log, there are many lines with
>> systemd, e.g.:
>> >
>> > Nov 25 22:30:14 ELCON45223 systemd-logind[155]: New session 6 of user
>> velle.
>> > Nov 25 22:30:14 ELCON45223 systemd: pam_unix(systemd-user:session):
>> session opened for user velle(uid=1000) by (uid=0)
>> >
>> > Could someone please help me understand exactly which part creates this
>> XDG_RUNTIME_DIR folder?
>>
>> /run/user/$UID for the "console" session (the one you get when
>> starting a WSL instance) is created by WSL before systemd. Adding "ls
>> -l /run/user" to user-runtime-dir at 1000.service ExecStartPre:
>>
>> Nov 27 12:34:22 tumbleweed unknown: WSL (2) ERROR:
>> WaitForBootProcess:3237: /sbin/init failed to start within 10000
>> Nov 27 12:34:22 tumbleweed unknown: ms
>> Nov 27 12:34:22 tumbleweed unknown: WSL (2): Creating login session for
>> andrei
>> ...
>> Nov 27 12:34:22 tumbleweed systemd[1]: Created slice User Slice of UID
>> 1000.
>> Nov 27 12:34:22 tumbleweed systemd[1]: Starting User Runtime Directory
>> /run/user/1000...
>> Nov 27 12:34:22 tumbleweed ls[520]: total 0
>> Nov 27 12:34:22 tumbleweed ls[520]: drwxr-xr-x 4 andrei users 120 Nov
>> 27 12:34 1000
>> Nov 27 12:34:22 tumbleweed systemd-logind[160]: New session 11 of user
>> andrei.
>> Nov 27 12:34:22 tumbleweed systemd[1]: Finished User Runtime Directory
>> /run/user/1000.
>>
>> So logind invokes user-runtime-dir at 1000.service, but it sees the
>> existing directory and does nothing. I would suggest asking this
>> question on WSL support channels.
>>
>> > Is it part of the systemd repo or not? And if the answer is (or may be)
>> different between Ubuntu and WSL Ubuntu, I would be happy if you share what
>> you know about any any of those cases :) Right now, I barely know where to
>> report this issue.
>> >
>> >
>> > On Sun, Nov 26, 2023 at 10:07 AM Andrei Borzenkov <arvidjaar at gmail.com>
>> wrote:
>> >>
>> >> On 26.11.2023 02:39, Thomas Larsen Wessel wrote:
>> >> > I set up WSL on Windows 10 and created an instance from the default
>> Ubuntu
>> >> > 22.04 image.
>> >> >
>> >> > I ran some (non-GUI) software that somehow relies on Qt, and
>> apparently Qt
>> >> > does some checks on the XDG environment, so I got the following.
>> >> >
>> >> > *Warning: QStandardPaths: wrong permissions on runtime directory
>> >> > /run/user/1000/, 0755 instead of 0700*
>> >> >
>> >> > And yes, all the user folders are set to 755, including much of their
>> >> > content, which violates the XDG Base Directory Specification.
>> (screenshot:
>> >> > https://i.imgur.com/ISn3ebh.png).
>> >> >
>> >> > As far as I can understand, its some part of systemd, that creates
>> this
>> >> > folder. So is this an issue with systemd?
>> >> >
>> >>
>> >> WSL does not use systemd by default.
>> >>
>> >> > The validate_runtime_directory in pam_systemd already does a number
>> of
>> >> > checks on XDG_RUNTIME_DIR. How about also checking if the
>> permissions are
>> >> > correct/valid?
>> >> >
>> >> > Sincerely, Thomas
>> >> >
>> >>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/systemd-devel/attachments/20231129/680ca4bf/attachment-0001.htm>