From: Paolo Abeni pabeni@redhat.com
This is a partial revert of the blamed commit, with a relevant change: mptcp_subflow_queue_clean() now just change the msk socket status and stop the worker, so that the UaF issue addressed by the blamed commit is not re-introduced.
The above prevents the mptcp worker from running concurrently with inet_csk_listen_stop(), as such race would trigger a warning, as reported by Christoph:
RSP: 002b:00007f784fe09cd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e WARNING: CPU: 0 PID: 25807 at net/ipv4/inet_connection_sock.c:1387 inet_csk_listen_stop+0x664/0x870 net/ipv4/inet_connection_sock.c:1387 RAX: ffffffffffffffda RBX: 00000000006bc050 RCX: 00007f7850afd6a9 RDX: 0000000000000000 RSI: 0000000020000340 RDI: 0000000000000004 Modules linked in: RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006bc05c R13: fffffffffffffea8 R14: 00000000006bc050 R15: 000000000001fe40
</TASK> CPU: 0 PID: 25807 Comm: syz-executor.7 Not tainted 6.2.0-g778e54711659 #7 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014 RIP: 0010:inet_csk_listen_stop+0x664/0x870 net/ipv4/inet_connection_sock.c:1387 RAX: 0000000000000000 RBX: ffff888100dfbd40 RCX: 0000000000000000 RDX: ffff8881363aab80 RSI: ffffffff81c494f4 RDI: 0000000000000005 RBP: ffff888126dad080 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000000 R12: ffff888100dfe040 R13: 0000000000000001 R14: 0000000000000000 R15: ffff888100dfbdd8 FS: 00007f7850a2c800(0000) GS:ffff88813bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000001b32d26000 CR3: 000000012fdd8006 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK> __tcp_close+0x5b2/0x620 net/ipv4/tcp.c:2875 __mptcp_close_ssk+0x145/0x3d0 net/mptcp/protocol.c:2427 mptcp_destroy_common+0x8a/0x1c0 net/mptcp/protocol.c:3277 mptcp_destroy+0x41/0x60 net/mptcp/protocol.c:3304 __mptcp_destroy_sock+0x56/0x140 net/mptcp/protocol.c:2965 __mptcp_close+0x38f/0x4a0 net/mptcp/protocol.c:3057 mptcp_close+0x24/0xe0 net/mptcp/protocol.c:3072 inet_release+0x53/0xa0 net/ipv4/af_inet.c:429 __sock_release+0x4e/0xf0 net/socket.c:651 sock_close+0x15/0x20 net/socket.c:1393 __fput+0xff/0x420 fs/file_table.c:321 task_work_run+0x8b/0xe0 kernel/task_work.c:179 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline] exit_to_user_mode_loop kernel/entry/common.c:171 [inline] exit_to_user_mode_prepare+0x113/0x120 kernel/entry/common.c:203 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] syscall_exit_to_user_mode+0x1d/0x40 kernel/entry/common.c:296 do_syscall_64+0x46/0x90 arch/x86/entry/common.c:86 entry_SYSCALL_64_after_hwframe+0x72/0xdc RIP: 0033:0x7f7850af70dc RAX: 0000000000000000 RBX: 0000000000000004 RCX: 00007f7850af70dc RDX: 00007f7850a2c800 RSI: 0000000000000002 RDI: 0000000000000003 RBP: 00000000006bd980 R08: 0000000000000000 R09: 00000000000018a0 R10: 00000000316338a4 R11: 0000000000000293 R12: 0000000000211e31 R13: 00000000006bc05c R14: 00007f785062c000 R15: 0000000000211af0
Fixes: 0a3f4f1f9c27 ("mptcp: fix UaF in listener shutdown") Cc: stable@vger.kernel.org Reported-by: Christoph Paasch cpaasch@apple.com Link: https://github.com/multipath-tcp/mptcp_net-next/issues/371 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 --- net/mptcp/protocol.c | 6 ++++- net/mptcp/protocol.h | 1 + net/mptcp/subflow.c | 72 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 78 insertions(+), 1 deletion(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c index 06c5872e3b00..5181fb91595b 100644 --- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -2365,8 +2365,12 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk, mptcp_subflow_drop_ctx(ssk); } else { /* otherwise tcp will dispose of the ssk and subflow ctx */ - if (ssk->sk_state == TCP_LISTEN) + if (ssk->sk_state == TCP_LISTEN) { + tcp_set_state(ssk, TCP_CLOSE); + mptcp_subflow_queue_clean(sk, ssk); + inet_csk_listen_stop(ssk); mptcp_event_pm_listener(ssk, MPTCP_EVENT_LISTENER_CLOSED); + }
__tcp_close(ssk, 0);
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h index 339a6f072989..3a2db1b862dd 100644 --- a/net/mptcp/protocol.h +++ b/net/mptcp/protocol.h @@ -629,6 +629,7 @@ void mptcp_close_ssk(struct sock *sk, struct sock *ssk, struct mptcp_subflow_context *subflow); void __mptcp_subflow_send_ack(struct sock *ssk); void mptcp_subflow_reset(struct sock *ssk); +void mptcp_subflow_queue_clean(struct sock *sk, struct sock *ssk); void mptcp_sock_graft(struct sock *sk, struct socket *parent); struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk); bool __mptcp_close(struct sock *sk, long timeout); diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c index d34588850545..bf5e5c72b5ee 100644 --- a/net/mptcp/subflow.c +++ b/net/mptcp/subflow.c @@ -1819,6 +1819,78 @@ 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; + + /* build a list of all unaccepted mptcp sockets */ + 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 */ + msk = mptcp_sk(subflow->conn); + if (msk->dl_next || msk == head) + continue; + + sock_hold(subflow->conn); + msk->dl_next = head; + head = msk; + } + spin_unlock_bh(&queue->rskq_lock); + if (!head) + return; + + /* can't acquire the msk socket lock under the subflow one, + * or will cause ABBA deadlock + */ + release_sock(listener_ssk); + + for (msk = head; msk; msk = next) { + struct sock *sk = (struct sock *)msk; + + lock_sock_nested(sk, SINGLE_DEPTH_NESTING); + next = msk->dl_next; + msk->dl_next = NULL; + + /* prevent the stack from later re-schedule the worker for + * this socket + */ + inet_sk_state_store(sk, TCP_CLOSE); + release_sock(sk); + + /* lockdep will report a false positive ABBA deadlock + * between cancel_work_sync and the listener socket. + * The involved locks belong to different sockets WRT + * the existing AB chain. + * Using a per socket key is problematic as key + * deregistration requires process context and must be + * performed at socket disposal time, in atomic + * context. + * Just tell lockdep to consider the listener socket + * released here. + */ + mutex_release(&listener_sk->sk_lock.dep_map, _RET_IP_); + mptcp_cancel_work(sk); + mutex_acquire(&listener_sk->sk_lock.dep_map, 0, 0, _RET_IP_); + + sock_put(sk); + } + + /* we are still under the listener msk socket lock */ + lock_sock_nested(listener_ssk, SINGLE_DEPTH_NESTING); +} + static int subflow_ulp_init(struct sock *sk) { struct inet_connection_sock *icsk = inet_csk(sk);