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(129-219-8-31.nat.asu.edu. [129.219.8.31]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-3339b024715sm2416474eec.17.2026.09.03.17.58.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2026 17:58:59 -0700 (PDT) From: Xiang Mei To: Eric Dumazet , Neal Cardwell , Kuniyuki Iwashima , "David S . Miller" , Jakub Kicinski , Paolo Abeni , Simon Horman Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Dmitry Safonov <0x7f454c46@gmail.com>, Salam Noureddine , Francesco Ruggeri , David Ahern , co+2c72469dbbec34af@bugs.sh, stable@vger.kernel.org, Xiang Mei Subject: [PATCH net] net/tcp-ao: transfer tcp_ao_info to the TIME_WAIT socket Date: Thu, 3 Sep 2026 17:58:51 -0700 Message-ID: <20260904005851.149071-1-xmei5@asu.edu> 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: quoted-printable Content-Type: text/plain; charset="utf-8" tcp_ao_time_wait() gives the TIME_WAIT socket a reference to the full socket's tcp_ao_info but leaves tp->ao_info pointing at the same object. That is only safe if the full socket is going away. On the tcp_fin() FIN_WAIT2 path (and TCP_CLOSING in tcp_rcv_state_process()) tcp_done() skips inet_csk_destroy_sock(), so the socket lives on in TCP_CLOSE with its fd open while the hashed TIME_WAIT socket reads the same tcp_ao_info from softirq, serialised against nothing. An unprivileged user can turn that into a NULL deref: tcp_disconnect() does not clear ao_info, so connect(AF_UNSPEC) + listen() reaches TCP_LISTEN where TCP_AO_DEL_KEY accepts del_async=3D1 and NULLs ao_info->rnext_key, which tcp_v4_timewait_ack() then dereferences unchecked. The triggering segment need not be authenticated, as tcp_v4_rcv()'s do_time_wait: path skips tcp_inbound_hash(). The refcount keeps the object allocated for both sockets, but nothing keeps its contents coherent: the setsockopt writers hold the full socket's lock while the TIME_WAIT reader runs in softirq, and no lock spans the two. Make the transition a handover, as the sk_omem_alloc charge moved here already implies: clear tp->ao_info instead of taking a second reference, leaving the TIME_WAIT socket as sole owner. Such a socket no longer exposes TCP-AO state (TCP_AO_INFO and TCP_AO_DEL_KEY return -ENOENT); that state describes the finished connection and belongs to the TIME_WAIT socket that keeps updating it. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000010: 0000 [#1] SMP KASAN NOPTI KASAN: null-ptr-deref in range [0x0000000000000080-0x0000000000000087] RIP: 0010:tcp_v4_rcv (net/ipv4/tcp_ipv4.c:1055 net/ipv4/tcp_ipv4.c:2333) Call Trace: ip_protocol_deliver_rcu (net/ipv4/ip_input.c:207) ip_local_deliver_finish (net/ipv4/ip_input.c:241) ip_local_deliver (net/ipv4/ip_input.c:262) ip_rcv (net/ipv4/ip_input.c:612) __netif_receive_skb_one_core (net/core/dev.c:6264) process_backlog (net/core/dev.c:6728) __napi_poll (net/core/dev.c:7787) net_rx_action (net/core/dev.c:8007) handle_softirqs (kernel/softirq.c:645) do_softirq.part.0 (kernel/softirq.c:546) __local_bh_enable_ip (kernel/softirq.c:473) __dev_queue_xmit (net/core/dev.c:4961) ip_finish_output2 (net/ipv4/ip_output.c:236) ip_output (net/ipv4/ip_output.c:437) __ip_queue_xmit (net/ipv4/ip_output.c:533) __tcp_transmit_skb (net/ipv4/tcp_output.c:1716) tcp_connect (net/ipv4/tcp_output.c:4383) tcp_v4_connect (net/ipv4/tcp_ipv4.c:345) __inet_stream_connect (net/ipv4/af_inet.c:684) inet_stream_connect (net/ipv4/af_inet.c:755) __sys_connect (net/socket.c:2183) __x64_sys_connect (net/socket.c:2189) do_syscall_64 (arch/x86/entry/syscall_64.c:84) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) Kernel panic - not syncing: Fatal exception in interrupt Fixes: decde2586b34 ("net/tcp: Add TCP-AO sign to twsk") Cc: stable@vger.kernel.org Reported-by: co+2c72469dbbec34af@bugs.sh Closes: https://lore.kernel.org/all/YG9s0PiBKJZcXAKld3MToa1IVRJOUoKiaA57%40= bugs.sh/ Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei --- net/ipv4/tcp_ao.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp_ao.c b/net/ipv4/tcp_ao.c index bb7bbc20ba3f..27525f90398b 100644 --- a/net/ipv4/tcp_ao.c +++ b/net/ipv4/tcp_ao.c @@ -428,7 +428,7 @@ void tcp_ao_time_wait(struct tcp_timewait_sock *tcptw, = struct tcp_sock *tp) omem +=3D tcp_ao_sizeof_key(key); } =20 - refcount_inc(&ao_info->refcnt); + rcu_assign_pointer(tp->ao_info, NULL); atomic_sub(omem, &(((struct sock *)tp)->sk_omem_alloc)); rcu_assign_pointer(tcptw->ao_info, ao_info); } else { --=20 2.43.0