Kernel BUG/Oops: tc qdisc delete with tc filter action xt -j CONNMARK

[Guido Sarducci]

Overview:
=========

Several uses of "tc filter .. action xt" work as expected and also allow final qdisc/filter deletion: e.g. xt_DSCP and xt_CLASSIFY.

However, trying to delete a qdisc/filter using xt_CONNMARK results in a kernel oops or hang/crash on all platforms and kernel versions tested.

Steps to Reproduce:
===================

# tc qdisc add dev lo clsact
# tc filter add dev lo egress protocol ip matchall action xt -j CONNMARK --save-mark
# tc qdisc del dev lo clsact
<Kernel Oops>

Systems Tested:
===============

Ubuntu 18.04 LTS (mainline kernel 5.2.6-050206-generic/x86_64, iptables 1.6.1, iproute2 4.15)
(Kernel build: https://kernel.ubuntu.com/~kernel-ppa/mainline/v5.2.6/)

Ubuntu 18.04 LTS (distro kernel 4.15.0-58-generic/x86_64, iptables 1.6.1, iproute2 4.15)

External Tracking:
==================

This bug is also tracked upstream at https://bugzilla.kernel.org/show_bug.cgi?id=204681, with logs.
There is also a proposed fix.

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:

apport-collect 1841397

and then change the status of the bug to 'Confirmed'.

If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.

This change has been made by an automated script, maintained by the Ubuntu Kernel Team.

[Guido Sarducci (gsarducci)]

The bug has already been confirmed by upstream kernel maintainers, and the Ubuntu logs are available at the "External Tracking" links above.