Comment 2 for bug 1966203

According to our investigation, I found that the issue is caused by the "mount" system call can not be allowed to execute.

And after checking the upstream commit, the issue is introduced by the following patch,

commit ee8f26180d01e3ddd4e5f20b03b81e5e737657ae
Author: Lennart Poettering <email address hidden>
Date: Thu Apr 19 11:04:17 2018 +0200

    units: switch from system call blacklist to whitelist

    This is generally the safer approach, and is what container managers
    (including nspawn) do, hence let's move to this too for our own
    services. This is particularly useful as this this means the new
    @system-service system call filter group will get serious real-life
    testing quickly.

    This also switches from firing SIGSYS on unexpected syscalls to
    returning EPERM. This would have probably been a better default anyway,
    but it's hard to change that these days. When whitelisting system calls
    SIGSYS is highly problematic as system calls that are newly introduced
    to Linux become minefields for services otherwise.

    Note that this enables a system call filter for udev for the first time,
    and will block @clock, @mount and @swap from it. Some downstream
    distributions might want to revert this locally if they want to permit
    unsafe operations on udev rules, but in general this shiuld be mostly
    safe, as we already set MountFlags=shared for udevd, hence at least
    @mount won't change anything.

Before the patch，systemd-udevd.service has not set “SystemCallFilter=”，but after the patch，the “SystemCallFilter=@system-service @module @raw-io” was added

diff --git a/units/systemd-udevd.service.in b/units/systemd-udevd.service.in
index 2b9fa69d9b..6a3814e5d9 100644
--- a/units/systemd-udevd.service.in
+++ b/units/systemd-udevd.service.in
@@ -29,6 +29,8 @@ PrivateMounts=yes
 MemoryDenyWriteExecute=yes
 RestrictRealtime=yes
 RestrictAddressFamilies=AF_UNIX AF_NETLINK AF_INET AF_INET6
+SystemCallFilter=@system-service @module @raw-io
+SystemCallErrorNumber=EPERM
 SystemCallArchitectures=native
 LockPersonality=yes
 IPAddressDeny=any

Because there is no "SystemCallFilter=@system-service @module @raw-io" in the /usr/lib/systemd/system/systemd-udevd.service on UBuntu20.04, we can not experience the same issue, but can reproduce the issue on UBuntu22.04.
If we add "@mount" to "SystemCallFilter=" on UBuntu22.04, the issue can be fixed.

Thanks,
Regards,
Jiwei