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core: limit number of LogExtraFields (#41044)

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We have two places where those fields can be set: config and the dbus
interface. Let's clamp down on the number in both places. But in
principle, we could also be upgrading (through
serialization/deserialization) from an older systemd which didn't
enforce this limit, so also check on deserialization. A user could have
a unit with lots and lots of ExtraFields, but not enough to cause the
issue in #40916. To handle this gracefully, ignore the extra fields,
like we do in the parser. Where the field is used, assert that we are
within the expected bounds.

Fixes #40916.

Reproducer:
```console
$ python3 -c 'from pydbus import SystemBus; from gi.repository import GLib; SystemBus().get("org.freedesktop.systemd1", "/org/freedesktop/systemd1").StartTransientUnit("crash.service", "fail", [("ExecStart", GLib.Variant("a(sasb)", [("/bin/true", ["/bin/true"], False)])), ("LogExtraFields", GLib.Variant("aay", [b"F%d=x" % i for i in range(140000)]))], [])' Traceback (most recent call last):
  File "<string>", line 1, in <module>
    from pydbus import SystemBus; from gi.repository import GLib; SystemBus().get("org.freedesktop.systemd1", "/org/freedesktop/systemd1").StartTransientUnit("crash.service", "fail", [("ExecStart", GLib.Variant("a(sasb)", [("/bin/true", ["/bin/true"], False)])), ("LogExtraFields", GLib.Variant("aay", [b"F%d=x" % i for i in range(140000)]))], [])
                                                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3.14/site-packages/pydbus/proxy_method.py", line 102, in __call__
    raise error
  File "/usr/lib/python3.14/site-packages/pydbus/proxy_method.py", line 97, in __call__
    result = instance._bus.con.call_sync(*call_args)
gi.repository.GLib.GError: g-dbus-error-quark: GDBus.Error:org.freedesktop.DBus.Error.InvalidArgs: Too many extra log fields. (16)
```
This commit is contained in:
Luca Boccassi
2026-03-11 19:40:43 +00:00
committed by GitHub
parent 4b551035b4 18031b17f8
commit 415663a13a
6 changed files with 72 additions and 23 deletions
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test/units/TEST-07-PID1.issue-40916.sh
Executable
+38
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#!/usr/bin/env bash
# SPDX-License-Identifier: LGPL-2.1-or-later
set -eux
set -o pipefail
# shellcheck source=test/units/util.sh
. "$(dirname "$0")"/util.sh
# Units with excessive numbers of fields in LogExtraFields=.
# Issue: https://github.com/systemd/systemd/issues/40916
UNIT=test-07-pid1-issue-40916.service
cleanup() {
rm -f /run/systemd/system/"$UNIT"
systemctl daemon-reload
}
trap cleanup EXIT
cat >/run/systemd/system/"$UNIT" <<EOF
[Service]
ExecStart=true
EOF
for i in {1..2000}; do
echo "LogExtraFields=FIELD_$i=$i"
done >>/run/systemd/system/"$UNIT"
systemctl start --wait "$UNIT"
systemctl show -p LogExtraFields "$UNIT" | grep FIELD_1000
(! systemctl show -p LogExtraFields "$UNIT" | grep FIELD_1500)
# Now try setting the properties dynamically
(! systemd-run --wait -u test-07-pid1-issue-40916-1.service -pLogExtraFields=FD{1..2000}=1 true)
systemd-run --wait -u test-07-pid1-issue-40916-1.service -pLogExtraFields=FD{1..1000}=1 true