From: Paolo Abeni <pabeni@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Tested-by: Christoph Paasch <cpaasch@xxxxxxxxx>
Reviewed-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
Signed-off-by: Matthieu Baerts <matthieu.baerts@xxxxxxxxxxxx>
---
net/mptcp/protocol.c | 20 ++++++++++++++------
1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 67311e7d5b21..86f8a7621aff 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1727,7 +1727,13 @@ static int mptcp_sendmsg_fastopen(struct sock *sk, struct msghdr *msg,
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;
}
inet_sk(sk)->defer_connect = 0;
@@ -2389,7 +2395,10 @@ static void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
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);
@@ -2812,7 +2821,7 @@ void mptcp_subflow_shutdown(struct sock *sk, struct sock *ssk, int how)
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))) {
@@ -3075,11 +3084,10 @@ static int mptcp_disconnect(struct sock *sk, int flags)
/* 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;
mptcp_listen_inuse_dec(sk);
inet_sk_state_store(sk, TCP_CLOSE);
--
2.40.1
