From nobody Sat Oct 24 20:19:12 2026 Received: from cvsmtppost17.nm.naver.com (cvsmtppost17.nm.naver.com [114.111.35.33]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2D7BA1A3166 for ; Sun, 11 Oct 2026 16:27:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=114.111.35.33 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791736082; cv=none; b=VcuLEHLZp991Bcovsw7mTp3lUrLJiH0hMJNPEnXesvrjT6QCaCIP8q6KiDq8k9WDdgNVF/tHr2PHfYPR/Pqn2B8gvq0N438cMBWZ3hWkD2u53+FbHcO8QzO7tFbpfCYdHiciobDjKWLB93PM4LPMsGCcC1FMub+pTMCFW9gCS+k= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791736082; c=relaxed/simple; bh=mfRz2zk9VSkKhAjFcY7J3woD/6Sps4QomEr2JVkpR0E=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=WiSrU+rek81UkxL49BI0/EWDHdbkb10QL0Qm+4Y0s6ImntoXNC08/v2sla5qN3WZWLyx2ciN1sWnR3ynKPn4IW4W+Hsj00IP1azSL5eSliWa02dohOKOyFUG1p74VGnDDcGM8LtAlxUzwCDPZ/ILu9UHU+jZ2gp3bHbf6SG6gQo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=naver.com; spf=pass smtp.mailfrom=naver.com; dkim=pass (2048-bit key) header.d=naver.com header.i=@naver.com header.b=GG23faiI; arc=none smtp.client-ip=114.111.35.33 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=naver.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=naver.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=naver.com header.i=@naver.com header.b="GG23faiI" Received: from cvsendbo016.nm ([10.112.24.39]) by cvsmtppost17.nm.naver.com with ESMTP id 1OhAFWX6S02LakH4NEbVAw for ; Sun, 11 Oct 2026 16:27:51 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=naver.com; s=s20171208; t=1791736071; bh=mfRz2zk9VSkKhAjFcY7J3woD/6Sps4QomEr2JVkpR0E=; h=From:To:Subject:Date:Message-Id:From:Subject:Feedback-ID: X-Works-Security; b=GG23faiIDkvzzL9ASf//+PBZ0J78fWOf0B2a3HzDTvRlZj06LY0LdgOgcjy7v/F3G 7/fOWD8Cp85kAO/5B9MieEVH28hRbctRt2andbisnWxUrA4m5O5iQDPW/ksH3ZUYjU xr6iUN8FxdjJn8ll7asG6uTWV++j6DiFJQPcwl55QevEQoYxqhWLeNp0CCzbz+D1HL F/PTJPN2Lad3Lpem1S4OsvfSyB0xMq9GkO0v7HMUtOG8E0zcu6VA/IuZJoauyMNPSD NkAmYd8XATWN2Qz7nt9/f47v3OVjo3DaHeTT7thTyzHGShbnphKwjn1y44AS0D9mre J+QDTgQLoGDVQ== X-Session-ID: NltzlvSiR0Wm6FzDlyrr8Q X-Works-Send-Opt: 0rRoWNkNjHmmKAidp4JZKHmmjAumjAurKAKmKqtwaACYkEljxBmwjAg= X-Works-Smtp-Source: lqKmFqulFqJZ+HmmFqMq+6E= Received: from localhost.localdomain ([125.130.170.186]) by cvnsmtp003.nm.naver.com with ESMTP id NltzlvSiR0Wm6FzDlyrr8Q for (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384); Sun, 11 Oct 2026 16:27:50 -0000 From: Seung Min Shin To: Marcelo Ricardo Leitner , Xin Long Cc: "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-sctp@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH net v2] sctp: hold transport reference across connect wait Date: Sun, 11 Oct 2026 16:27:50 +0000 Message-Id: <20261011162750.1529631-1-guncraft2000@naver.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" sctp_sendmsg_to_asoc() selects a transport before waiting for a new interleaved association to become established. sctp_wait_for_connect() drops the socket lock while sleeping. While the lock is dropped, backlog processing can handle a COOKIE ACK and an ASCONF DEL-IP that removes the selected transport. sctp_assoc_rm_peer() then marks the transport dead and drops its association-owned reference. The transport can be freed through RCU before the send path resumes. After the wait, the stale pointer is assigned to newly created DATA or I-DATA chunks and later dereferenced by sctp_outq_select_transport(). Hold a reference to the selected transport across sctp_wait_for_connect(). After the socket lock is reacquired, abort the send if the transport was marked dead. Callers without a selected transport pass NULL and retain their existing behavior. Cc: stable@vger.kernel.org Fixes: 668c9beb9020 ("sctp: implement assign_number for sctp_stream_interle= ave") Acked-by: Xin Long Assisted-by: LLM Signed-off-by: Seung Min Shin --- Notes (sctp-connect-wait-v2): v2: - Rebase onto current net/main after commit 4f1da630d13de. - Preserve the RCV_SHUTDOWN check added by that commit. - Add the stable list now that the issue is public. =20 v1: https://lore.kernel.org/netdev/20260928152132.3705137-1-guncraft200= 0@naver.com/ =20 Tested on net/main af32da41b032 with CONFIG_KASAN=3Dy on x86-64. =20 Before the patch, the reproducer triggered a KASAN slab-use-after-free = in sctp_outq_select_transport() on its first run. After the patch, 64 atte= mpts completed without a KASAN, refcount, BUG, WARNING, oops, or panic repor= t. A diagnostic run returned ESRCH in all 64 attempts and left the associati= on in SCTP_ESTABLISHED state. A normal interleaved connect/send smoke test pa= ssed. net/sctp/socket.c | 26 +++++++++++++++++++------- 1 file changed, 19 insertions(+), 7 deletions(-) diff --git a/net/sctp/socket.c b/net/sctp/socket.c index e35692dd8d30..189b89a40d46 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -75,7 +75,8 @@ static int sctp_wait_for_sndbuf(struct sctp_association *= asoc, struct sctp_transport *transport, long *timeo_p, size_t msg_len); static int sctp_wait_for_packet(struct sock *sk, int *err, long *timeo_p); -static int sctp_wait_for_connect(struct sctp_association *, long *timeo_p); +static int sctp_wait_for_connect(struct sctp_association *, + struct sctp_transport *, long *timeo_p); static int sctp_wait_for_accept(struct sock *sk, long timeo); static void sctp_wait_for_close(struct sock *sk, long timeo); static void sctp_destruct_sock(struct sock *sk); @@ -1245,7 +1246,7 @@ static int __sctp_connect(struct sock *sk, struct soc= kaddr *kaddrs, *assoc_id =3D asoc->assoc_id; =20 timeo =3D sock_sndtimeo(sk, flags & O_NONBLOCK); - return sctp_wait_for_connect(asoc, &timeo); + return sctp_wait_for_connect(asoc, NULL, &timeo); =20 out_free: pr_debug("%s: took out_free path with asoc:%p kaddrs:%p err:%d\n", @@ -1843,7 +1844,7 @@ static int sctp_sendmsg_to_asoc(struct sctp_associati= on *asoc, =20 if (asoc->ep->intl_enable) { timeo =3D sock_sndtimeo(sk, 0); - err =3D sctp_wait_for_connect(asoc, &timeo); + err =3D sctp_wait_for_connect(asoc, transport, &timeo); if (err || sk->sk_shutdown & RCV_SHUTDOWN) { err =3D -ESRCH; goto err; @@ -1881,7 +1882,7 @@ static int sctp_sendmsg_to_asoc(struct sctp_associati= on *asoc, =20 if (unlikely(wait_connect)) { timeo =3D sock_sndtimeo(sk, msg->msg_flags & MSG_DONTWAIT); - sctp_wait_for_connect(asoc, &timeo); + sctp_wait_for_connect(asoc, NULL, &timeo); } =20 err =3D msg_len; @@ -9381,7 +9382,9 @@ static bool sctp_writeable(const struct sock *sk) /* Wait for an association to go into ESTABLISHED state. If timeout is 0, * returns immediately with EINPROGRESS. */ -static int sctp_wait_for_connect(struct sctp_association *asoc, long *time= o_p) +static int sctp_wait_for_connect(struct sctp_association *asoc, + struct sctp_transport *transport, + long *timeo_p) { struct sock *sk =3D asoc->base.sk; int err =3D 0; @@ -9390,12 +9393,16 @@ static int sctp_wait_for_connect(struct sctp_associ= ation *asoc, long *timeo_p) =20 pr_debug("%s: asoc:%p, timeo:%ld\n", __func__, asoc, *timeo_p); =20 - /* Increment the association's refcnt. */ + /* Hold references while the socket lock is dropped. */ + if (transport) + sctp_transport_hold(transport); sctp_association_hold(asoc); =20 for (;;) { prepare_to_wait_exclusive(&asoc->wait, &wait, TASK_INTERRUPTIBLE); + if (transport && transport->dead) + goto do_transport_dead; if (!*timeo_p) goto do_nonblock; if (sk->sk_shutdown & RCV_SHUTDOWN) @@ -9424,7 +9431,8 @@ static int sctp_wait_for_connect(struct sctp_associat= ion *asoc, long *timeo_p) out: finish_wait(&asoc->wait, &wait); =20 - /* Release the association's refcnt. */ + if (transport) + sctp_transport_put(transport); sctp_association_put(asoc); =20 return err; @@ -9443,6 +9451,10 @@ static int sctp_wait_for_connect(struct sctp_associa= tion *asoc, long *timeo_p) do_nonblock: err =3D -EINPROGRESS; goto out; + +do_transport_dead: + err =3D -EAGAIN; + goto out; } =20 static int sctp_wait_for_accept(struct sock *sk, long timeo) base-commit: af32da41b0327b9c6a37856ba82b6760d6c8d10e --=20 2.34.1