From: Paolo Abeni pabeni@redhat.com
commit c2b2ae3925b65070adb27d5a31a31c376f26dec7 upstream.
Currently the mptcp code has assumes that disconnect() can fail only at mptcp_sendmsg_fastopen() time - to avoid a deadlock scenario - and don't even bother returning an error code.
Soon mptcp_disconnect() will handle more error conditions: let's track them explicitly.
As a bonus, explicitly annotate TCP-level disconnect as not failing: the mptcp code never blocks for event on the subflows.
Fixes: 7d803344fdc3 ("mptcp: fix deadlock in fastopen error path") Cc: stable@vger.kernel.org Signed-off-by: Paolo Abeni pabeni@redhat.com Tested-by: Christoph Paasch cpaasch@apple.com Reviewed-by: Matthieu Baerts matthieu.baerts@tessares.net Signed-off-by: Matthieu Baerts matthieu.baerts@tessares.net Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/mptcp/protocol.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)
--- a/net/mptcp/protocol.c +++ b/net/mptcp/protocol.c @@ -1708,7 +1708,13 @@ static int mptcp_sendmsg_fastopen(struct if (ret && ret != -EINPROGRESS && ret != -ERESTARTSYS && ret != -EINTR) *copied_syn = 0; } else if (ret && ret != -EINPROGRESS) { - mptcp_disconnect(sk, 0); + /* The disconnect() op called by tcp_sendmsg_fastopen()/ + * __inet_stream_connect() can fail, due to looking check, + * see mptcp_disconnect(). + * Attempt it again outside the problematic scope. + */ + if (!mptcp_disconnect(sk, 0)) + sk->sk_socket->state = SS_UNCONNECTED; }
return ret; @@ -2375,7 +2381,10 @@ static void __mptcp_close_ssk(struct soc
need_push = (flags & MPTCP_CF_PUSH) && __mptcp_retransmit_pending_data(sk); if (!dispose_it) { - tcp_disconnect(ssk, 0); + /* The MPTCP code never wait on the subflow sockets, TCP-level + * disconnect should never fail + */ + WARN_ON_ONCE(tcp_disconnect(ssk, 0)); msk->subflow->state = SS_UNCONNECTED; mptcp_subflow_ctx_reset(subflow); release_sock(ssk); @@ -2799,7 +2808,7 @@ void mptcp_subflow_shutdown(struct sock break; fallthrough; case TCP_SYN_SENT: - tcp_disconnect(ssk, O_NONBLOCK); + WARN_ON_ONCE(tcp_disconnect(ssk, O_NONBLOCK)); break; default: if (__mptcp_check_fallback(mptcp_sk(sk))) { @@ -3053,11 +3062,10 @@ static int mptcp_disconnect(struct sock
/* We are on the fastopen error path. We can't call straight into the * subflows cleanup code due to lock nesting (we are already under - * msk->firstsocket lock). Do nothing and leave the cleanup to the - * caller. + * msk->firstsocket lock). */ if (msk->fastopening) - return 0; + return -EBUSY;
inet_sk_state_store(sk, TCP_CLOSE);