Re: [PATCH net-next v6] l2tp: fix double dst_release() on sk_dst_cache race

From: Jakub Kicinski

Date: Tue Dec 02 2025 - 14:08:15 EST


On Tue, 2 Dec 2025 21:05:43 +0300 Mikhail Lobanov wrote:
> A reproducible rcuref - imbalanced put() warning is observed under
> IPv6 L2TP (pppol2tp) traffic with blackhole routes, indicating an
> imbalance in dst reference counting for routes cached in
> sk->sk_dst_cache and pointing to a subtle lifetime/synchronization
> issue between the helpers that validate and drop cached dst entries.

Breaks allmodconfig build:

ERROR: modpost: "ip_options_build" [net/l2tp/l2tp_core.ko] undefined!

Please note that net-next is closed for the duration of the merge
window. If you want to repost this (after waiting the customary 24h)
please do so as an RFC.
--
pw-bot: cr