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Wed, 15 Oct 2025 16:04:25 -0400 (EDT) Date: Wed, 15 Oct 2025 22:04:23 +0200 From: Sabrina Dubroca To: Eric Dumazet Cc: "David S . Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman , Willem de Bruijn , netdev@vger.kernel.org, eric.dumazet@gmail.com, Michal Kubecek , Florian Westphal Subject: Re: [PATCH v3 net] udp: do not use skb_release_head_state() before skb_attempt_defer_free() Message-ID: References: <20251015052715.4140493-1-edumazet@google.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20251015052715.4140493-1-edumazet@google.com> 2025-10-15, 05:27:15 +0000, Eric Dumazet wrote: > Michal reported and bisected an issue after recent adoption > of skb_attempt_defer_free() in UDP. > > The issue here is that skb_release_head_state() is called twice per skb, > one time from skb_consume_udp(), then a second time from skb_defer_free_flush() > and napi_consume_skb(). > > As Sabrina suggested, remove skb_release_head_state() call from > skb_consume_udp(). > > Add a DEBUG_NET_WARN_ON_ONCE(skb_nfct(skb)) in skb_attempt_defer_free() > > Many thanks to Michal, Sabrina, Paolo and Florian for their help. > > Fixes: 6471658dc66c ("udp: use skb_attempt_defer_free()") > Reported-and-bisected-by: Michal Kubecek > Closes: https://lore.kernel.org/netdev/gpjh4lrotyephiqpuldtxxizrsg6job7cvhiqrw72saz2ubs3h@g6fgbvexgl3r/ > Signed-off-by: Eric Dumazet > Tested-by: Michal Kubecek > Cc: Sabrina Dubroca > Cc: Florian Westphal Reviewed-by: Sabrina Dubroca Thanks Eric. -- Sabrina