In the Linux kernel, the following vulnerability has been resolved: net/sched: reject overly deep qdisc hierarchies Deep qdisc hierarchies can lead to excessive recursion in qdisc tree walkers and exhaust the kernel stack. The existing loop check does not cover the create-and-graft path, so a hierarchy can still be extended by creating a new child qdisc below an already deep parent. Store the hierarchy depth in struct Qdisc and update it when qdiscs are grafted. Reject new child qdiscs once the parent is already at the maximum allowed depth.
https://git.kernel.org/stable/c/e2d658c6427844cee5bc654b436ca68d680b6148
https://git.kernel.org/stable/c/dedd34b0f2310e28c5f6d4875cfbf4b7ed821c01
https://git.kernel.org/stable/c/a4b14a4df29d36458a943f9b521ddd0f940363cc
https://git.kernel.org/stable/c/9f69bb9fdaa2fe64b68bb62fb84d405784bee540
https://git.kernel.org/stable/c/8ca8cdb74939581339e1ae370193c0adb5a85336
https://git.kernel.org/stable/c/2759acf08a3454866660edcd3ef4e64139f254a6