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[144.76.156.219]) by smtp.gmail.com with ESMTPSA id o10-20020a5d474a000000b003141a3c4353sm253167wrs.30.2023.08.03.09.27.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Aug 2023 09:27:51 -0700 (PDT) From: Matthieu Baerts Date: Thu, 03 Aug 2023 18:27:30 +0200 Subject: [PATCH net 4/4] mptcp: fix disconnect vs accept race Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20230803-upstream-net-20230803-misc-fixes-6-5-v1-4-6671b1ab11cc@tessares.net> References: <20230803-upstream-net-20230803-misc-fixes-6-5-v1-0-6671b1ab11cc@tessares.net> In-Reply-To: <20230803-upstream-net-20230803-misc-fixes-6-5-v1-0-6671b1ab11cc@tessares.net> To: mptcp@lists.linux.dev, Mat Martineau , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Shuah Khan , Geliang Tang Cc: Andrea Claudi , netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Matthieu Baerts , stable@vger.kernel.org, Christoph Paasch X-Mailer: b4 0.12.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=6350; i=matthieu.baerts@tessares.net; h=from:subject:message-id; bh=aKcow2E15Tjek3grxJIpgMFsqze4hMw1QTBvn16JVm8=; b=owEBbQKS/ZANAwAIAfa3gk9CaaBzAcsmYgBky9WCZ/PIlkegmWQ+oRn1/er9lZ7+r/US1BaBo xry6wrvOpyJAjMEAAEIAB0WIQToy4X3aHcFem4n93r2t4JPQmmgcwUCZMvVggAKCRD2t4JPQmmg c6r+EADDM4nK4HHbE8VttqzJEu2kc7hBHUe/O1+iQPG3XmqMkMORrSJP1OjRnmYV0NBnKGARiKJ /drfsn60O8gpJoMpBhOuoWhUvlXaWNTURDne8QvBuY+b04dhjLQ/K4+im9U0FQiPDRC7JMbtu/N VRdEBWbcSVTcLPrxqtXljnPYlpXxAGQU0UAoYA0phciVxwJkRCbXnl3pcRZqH4DW+L71cIxAGpk dcuuzpfXakNQ4NwWvg1kMYhgM74q9DVuVRhsvOFgfouWWg4eYk2KZBN0hF09wYUapzilA56mN0P o0dYXp0+OohL2LG5BzeyAjFyC/LSNbHrxkUgbR/Q2s/bQlR+OBtW74z8JrR3dq5v9ovYwxAGjLn Hm51kzqOkgIg8n45zIgF9X7vLzwTY04kdRmsA+kKrXen0hQlrCRS9wWGy+PIiVtXJTWS9d7D4LH mztuedwS5jh4zK77CJQGydo2XCwvqe3cpR5+RdsSTvXfNUa5HhCCE8n8sJM62BbNCe4bXpLg0sE DhBUkMig9XxKur3bdZmrdF+NE9rqmLWmn9LDbs7RfPs+4a1pXL0RWLDeFdwMSzB6QT1ST8oJPPt lRWH8NfWhlbwrbglyp3pMK3TRtAsgoiQefToVlOc/vzh03SIwGz40Ih4PJF41EM9c1PXCAsqLFJ +qc+0oELhN/D9jA== X-Developer-Key: i=matthieu.baerts@tessares.net; a=openpgp; fpr=E8CB85F76877057A6E27F77AF6B7824F4269A073 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_BLOCKED, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net X-Patchwork-Delegate: kuba@kernel.org From: Paolo Abeni Despite commit 0ad529d9fd2b ("mptcp: fix possible divide by zero in recvmsg()"), the mptcp protocol is still prone to a race between disconnect() (or shutdown) and accept. The root cause is that the mentioned commit checks the msk-level flag, but mptcp_stream_accept() does acquire the msk-level lock, as it can rely directly on the first subflow lock. As reported by Christoph than can lead to a race where an msk socket is accepted after that mptcp_subflow_queue_clean() releases the listener socket lock and just before it takes destructive actions leading to the following splat: BUG: kernel NULL pointer dereference, address: 0000000000000012 PGD 5a4ca067 P4D 5a4ca067 PUD 37d4c067 PMD 0 Oops: 0000 [#1] PREEMPT SMP CPU: 2 PID: 10955 Comm: syz-executor.5 Not tainted 6.5.0-rc1-gdc7b257ee5dd #37 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 RIP: 0010:mptcp_stream_accept+0x1ee/0x2f0 include/net/inet_sock.h:330 Code: 0a 09 00 48 8b 1b 4c 39 e3 74 07 e8 bc 7c 7f fe eb a1 e8 b5 7c 7f fe 4c 8b 6c 24 08 eb 05 e8 a9 7c 7f fe 49 8b 85 d8 09 00 00 <0f> b6 40 12 88 44 24 07 0f b6 6c 24 07 bf 07 00 00 00 89 ee e8 89 RSP: 0018:ffffc90000d07dc0 EFLAGS: 00010293 RAX: 0000000000000000 RBX: ffff888037e8d020 RCX: ffff88803b093300 RDX: 0000000000000000 RSI: ffffffff833822c5 RDI: ffffffff8333896a RBP: 0000607f82031520 R08: ffff88803b093300 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000003e83 R12: ffff888037e8d020 R13: ffff888037e8c680 R14: ffff888009af7900 R15: ffff888009af6880 FS: 00007fc26d708640(0000) GS:ffff88807dd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000012 CR3: 0000000066bc5001 CR4: 0000000000370ee0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: do_accept+0x1ae/0x260 net/socket.c:1872 __sys_accept4+0x9b/0x110 net/socket.c:1913 __do_sys_accept4 net/socket.c:1954 [inline] __se_sys_accept4 net/socket.c:1951 [inline] __x64_sys_accept4+0x20/0x30 net/socket.c:1951 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x47/0xa0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x6e/0xd8 Address the issue by temporary removing the pending request socket from the accept queue, so that racing accept() can't touch them. After depleting the msk - the ssk still exists, as plain TCP sockets, re-insert them into the accept queue, so that later inet_csk_listen_stop() will complete the tcp socket disposal. Fixes: 2a6a870e44dd ("mptcp: stops worker on unaccepted sockets at listener close") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/423 Signed-off-by: Paolo Abeni Reviewed-by: Matthieu Baerts Signed-off-by: Matthieu Baerts --- net/mptcp/protocol.h | 1 - net/mptcp/subflow.c | 60 ++++++++++++++++++++++++++-------------------------- 2 files changed, 30 insertions(+), 31 deletions(-) diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 37fbe22e2433..ba2a873a4d2e 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -325,7 +325,6 @@ struct mptcp_sock { u32 subflow_id; u32 setsockopt_seq; char ca_name[TCP_CA_NAME_MAX]; - struct mptcp_sock *dl_next; }; #define mptcp_data_lock(sk) spin_lock_bh(&(sk)->sk_lock.slock) diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index 9ee3b7abbaf6..94ae7dd01c65 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1793,34 +1793,21 @@ static void subflow_state_change(struct sock *sk) void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_ssk) { struct request_sock_queue *queue = &inet_csk(listener_ssk)->icsk_accept_queue; - struct mptcp_sock *msk, *next, *head = NULL; - struct request_sock *req; - struct sock *sk; + struct request_sock *req, *head, *tail; + struct mptcp_subflow_context *subflow; + struct sock *sk, *ssk; - /* build a list of all unaccepted mptcp sockets */ + /* Due to lock dependencies no relevant lock can be acquired under rskq_lock. + * Splice the req list, so that accept() can not reach the pending ssk after + * the listener socket is released below. + */ spin_lock_bh(&queue->rskq_lock); - for (req = queue->rskq_accept_head; req; req = req->dl_next) { - struct mptcp_subflow_context *subflow; - struct sock *ssk = req->sk; - - if (!sk_is_mptcp(ssk)) - continue; - - subflow = mptcp_subflow_ctx(ssk); - if (!subflow || !subflow->conn) - continue; - - /* skip if already in list */ - sk = subflow->conn; - msk = mptcp_sk(sk); - if (msk->dl_next || msk == head) - continue; - - sock_hold(sk); - msk->dl_next = head; - head = msk; - } + head = queue->rskq_accept_head; + tail = queue->rskq_accept_tail; + queue->rskq_accept_head = NULL; + queue->rskq_accept_tail = NULL; spin_unlock_bh(&queue->rskq_lock); + if (!head) return; @@ -1829,13 +1816,19 @@ void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_s */ release_sock(listener_ssk); - for (msk = head; msk; msk = next) { - sk = (struct sock *)msk; + for (req = head; req; req = req->dl_next) { + ssk = req->sk; + if (!sk_is_mptcp(ssk)) + continue; + + subflow = mptcp_subflow_ctx(ssk); + if (!subflow || !subflow->conn) + continue; + + sk = subflow->conn; + sock_hold(sk); lock_sock_nested(sk, SINGLE_DEPTH_NESTING); - next = msk->dl_next; - msk->dl_next = NULL; - __mptcp_unaccepted_force_close(sk); release_sock(sk); @@ -1859,6 +1852,13 @@ void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_s /* we are still under the listener msk socket lock */ lock_sock_nested(listener_ssk, SINGLE_DEPTH_NESTING); + + /* restore the listener queue, to let the TCP code clean it up */ + spin_lock_bh(&queue->rskq_lock); + WARN_ON_ONCE(queue->rskq_accept_head); + queue->rskq_accept_head = head; + queue->rskq_accept_tail = tail; + spin_unlock_bh(&queue->rskq_lock); } static int subflow_ulp_init(struct sock *sk)