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mptcp: fix disconnect vs accept race
Despite commit0ad529d9fd
("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: <TASK> 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:2a6a870e44
("mptcp: stops worker on unaccepted sockets at listener close") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch <cpaasch@apple.com> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/423 Signed-off-by: Paolo Abeni <pabeni@redhat.com> Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net> Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net> Link: https://lore.kernel.org/r/20230803-upstream-net-20230803-misc-fixes-6-5-v1-4-6671b1ab11cc@tessares.net Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
parent
ff18f9ef30
commit
511b90e392
2 changed files with 30 additions and 31 deletions
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@ -325,7 +325,6 @@ struct mptcp_sock {
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u32 subflow_id;
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u32 setsockopt_seq;
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char ca_name[TCP_CA_NAME_MAX];
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struct mptcp_sock *dl_next;
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};
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#define mptcp_data_lock(sk) spin_lock_bh(&(sk)->sk_lock.slock)
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@ -1793,34 +1793,21 @@ static void subflow_state_change(struct sock *sk)
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void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_ssk)
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{
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struct request_sock_queue *queue = &inet_csk(listener_ssk)->icsk_accept_queue;
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struct mptcp_sock *msk, *next, *head = NULL;
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struct request_sock *req;
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struct sock *sk;
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struct request_sock *req, *head, *tail;
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struct mptcp_subflow_context *subflow;
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struct sock *sk, *ssk;
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/* build a list of all unaccepted mptcp sockets */
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/* Due to lock dependencies no relevant lock can be acquired under rskq_lock.
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* Splice the req list, so that accept() can not reach the pending ssk after
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* the listener socket is released below.
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*/
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spin_lock_bh(&queue->rskq_lock);
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for (req = queue->rskq_accept_head; req; req = req->dl_next) {
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struct mptcp_subflow_context *subflow;
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struct sock *ssk = req->sk;
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if (!sk_is_mptcp(ssk))
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continue;
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subflow = mptcp_subflow_ctx(ssk);
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if (!subflow || !subflow->conn)
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continue;
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/* skip if already in list */
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sk = subflow->conn;
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msk = mptcp_sk(sk);
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if (msk->dl_next || msk == head)
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continue;
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sock_hold(sk);
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msk->dl_next = head;
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head = msk;
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}
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head = queue->rskq_accept_head;
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tail = queue->rskq_accept_tail;
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queue->rskq_accept_head = NULL;
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queue->rskq_accept_tail = NULL;
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spin_unlock_bh(&queue->rskq_lock);
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if (!head)
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return;
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@ -1829,13 +1816,19 @@ void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_s
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*/
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release_sock(listener_ssk);
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for (msk = head; msk; msk = next) {
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sk = (struct sock *)msk;
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for (req = head; req; req = req->dl_next) {
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ssk = req->sk;
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if (!sk_is_mptcp(ssk))
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continue;
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subflow = mptcp_subflow_ctx(ssk);
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if (!subflow || !subflow->conn)
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continue;
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sk = subflow->conn;
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sock_hold(sk);
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lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
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next = msk->dl_next;
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msk->dl_next = NULL;
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__mptcp_unaccepted_force_close(sk);
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release_sock(sk);
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@ -1859,6 +1852,13 @@ void mptcp_subflow_queue_clean(struct sock *listener_sk, struct sock *listener_s
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/* we are still under the listener msk socket lock */
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lock_sock_nested(listener_ssk, SINGLE_DEPTH_NESTING);
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/* restore the listener queue, to let the TCP code clean it up */
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spin_lock_bh(&queue->rskq_lock);
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WARN_ON_ONCE(queue->rskq_accept_head);
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queue->rskq_accept_head = head;
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queue->rskq_accept_tail = tail;
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spin_unlock_bh(&queue->rskq_lock);
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}
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static int subflow_ulp_init(struct sock *sk)
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