Re: [PATCH net v2 1/2] net/sched: reject overly deep qdisc hierarchies

[Victor Nogueira]

On 01/08/2026 10:42, Ren Wei wrote:
> From: Zijie Huang <milkory@xxxxxxxxxxx>
>
> 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.
>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Cc: stable@xxxxxxxxxxxxxxx
> Reported-by: Vega <vega@xxxxxxxxxx>
> Assisted-by: Codex:gpt-5.4
> Signed-off-by: Zijie Huang <milkory@xxxxxxxxxxx>
> Signed-off-by: Ren Wei <enjou1224z@xxxxxxxxx>

Reviewed-by: Victor Nogueira <victor@xxxxxxxxxxxx>