In the Linux kernel, the following vulnerability has been resolved:
netsched: Prevent creation of classes with TCH_ROOT
The function qdisctreereducebacklog() uses TCHROOT as a termination condition when traversing up the qdisc tree to update parent backlog counters. However, if a class is created with classid TCH_ROOT, the traversal terminates prematurely at this class instead of reaching the actual root qdisc, causing parent statistics to be incorrectly maintained. In case of DRR, this could lead to a crash as reported by Mingi Cho.
Prevent the creation of any Qdisc class with classid TCHROOT (0xFFFFFFFF) across all qdisc types, as suggested by Jamal.