linux-kernel - Re: [PATCH net-next v6] l2tp: fix double dst_release() on sk_dst

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Message-ID: <20251202110805.765fa71d@kernel.org>
Date: Tue, 2 Dec 2025 11:08:05 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Mikhail Lobanov <m.lobanov@...a.ru>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Simon Horman
 <horms@...nel.org>, David Bauer <mail@...id-bauer.net>, James Chapman
 <jchapman@...alix.com>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, lvc-project@...uxtesting.org
Subject: Re: [PATCH net-next v6] l2tp: fix double dst_release() on
 sk_dst_cache race

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