625077264b
Devices referred to by `DeviceAllow=` sandboxing are resolved into their corresponding major numbers when the unit is loaded by looking at `/proc/devices`. If a reference is made to a device which is not yet available, the `DeviceAllow` is ignored and the unit's processes cannot access that device. In both logind and nspawn, we have `DeviceAllow=` lines, and `modprobe` in `ExecStartPre=` to load some kernel modules. Those kernel modules cause device nodes to become available when they are loaded: the device nodes may not exist when the unit itself is loaded. This means that the unit's processes will not be able to access the device since the `DeviceAllow=` will have been resolved earlier and denied it. One way to fix this would be to re-evaluate the available devices and re-apply the policy to the cgroup, but this cannot work atomically on cgroupsv1. So we fall back to a second approach: instead of running `modprobe` via `ExecStartPre`, we move this out to a separate unit and order it before the units which want the module. Closes #14322. Fixes: #13943.
51 lines
1.7 KiB
SYSTEMD
51 lines
1.7 KiB
SYSTEMD
# SPDX-License-Identifier: LGPL-2.1+
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#
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# This file is part of systemd.
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#
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# systemd is free software; you can redistribute it and/or modify it
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# under the terms of the GNU Lesser General Public License as published by
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# the Free Software Foundation; either version 2.1 of the License, or
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# (at your option) any later version.
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[Unit]
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Description=Container %i
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Documentation=man:systemd-nspawn(1)
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Wants=modprobe@tun.service modprobe@loop.service modprobe@dm-mod.service
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PartOf=machines.target
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Before=machines.target
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After=network.target systemd-resolved.service modprobe@tun.service modprobe@loop.service modprobe@dm-mod.service
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RequiresMountsFor=/var/lib/machines
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[Service]
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# Make sure the DeviceAllow= lines below can properly resolve the 'block-loop' expression (and others)
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ExecStart=@bindir@/systemd-nspawn --quiet --keep-unit --boot --link-journal=try-guest --network-veth -U --settings=override --machine=%i
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KillMode=mixed
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Type=notify
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RestartForceExitStatus=133
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SuccessExitStatus=133
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Slice=machine.slice
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Delegate=yes
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TasksMax=16384
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@SERVICE_WATCHDOG@
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# Enforce a strict device policy, similar to the one nspawn configures when it
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# allocates its own scope unit. Make sure to keep these policies in sync if you
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# change them!
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DevicePolicy=closed
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DeviceAllow=/dev/net/tun rwm
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DeviceAllow=char-pts rw
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# nspawn itself needs access to /dev/loop-control and /dev/loop, to implement
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# the --image= option. Add these here, too.
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DeviceAllow=/dev/loop-control rw
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DeviceAllow=block-loop rw
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DeviceAllow=block-blkext rw
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# nspawn can set up LUKS encrypted loopback files, in which case it needs
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# access to /dev/mapper/control and the block devices /dev/mapper/*.
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DeviceAllow=/dev/mapper/control rw
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DeviceAllow=block-device-mapper rw
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[Install]
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WantedBy=machines.target
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