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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Xiang Mei , Weiming Shi Subject: [PATCH] atm: fix skb leak in sigd_send() on a closing listen socket Date: Fri, 12 Jun 2026 00:38:06 +0800 Message-ID: <20260611163805.2151734-2-bestswngs@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit In the as_indicate path, sigd_send() pins the listening socket with find_get_vcc() and queues the skb on its receive queue under lock_sock(). It does not check whether the socket is being torn down. If the listener is closed concurrently, vcc_destroy_socket() purges the receive queue once under lock_sock() and removes the socket from vcc_hash; the final free goes __sk_destruct() -> vcc_sock_destruct(), which does not purge. A skb queued after that purge is therefore leaked. Recheck ATM_VF_CLOSE under lock_sock() before queuing and drop the skb if the socket is closing. ATM_VF_CLOSE is set by vcc_destroy_socket() under the same lock, so the check is serialised against the purge. Reaching this requires an attached signalling daemon (CAP_NET_ADMIN and CAP_SYS_RAWIO), as only the daemon emits as_indicate. Fixes: ae88a5d2f29b ("net: atm: fix crash due to unvalidated vcc pointer in sigd_send()") Tested-by: Xiang Mei Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Weiming Shi Link: https://lore.kernel.org/all/aigrk5B3VzaWgKIF@Air.local/ --- net/atm/signaling.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/net/atm/signaling.c b/net/atm/signaling.c index 358fbe5e4d1d0..cb80b5a9d8452 100644 --- a/net/atm/signaling.c +++ b/net/atm/signaling.c @@ -150,6 +150,11 @@ static int sigd_send(struct atm_vcc *vcc, struct sk_buff *skb) sk = sk_atm(vcc); pr_debug("as_indicate!!!\n"); lock_sock(sk); + /* Don't queue onto a closing listener; the skb would leak. */ + if (test_bit(ATM_VF_CLOSE, &vcc->flags)) { + dev_kfree_skb(skb); + goto as_indicate_complete; + } if (sk_acceptq_is_full(sk)) { sigd_enq(NULL, as_reject, vcc, NULL, NULL); dev_kfree_skb(skb); -- 2.43.0