mptcp: be careful on subflows shutdown
When the workqueue disposes of the msk, the subflows can still
receive some data from the peer after __mptcp_close_ssk()
completes.
The above could trigger a race between the msk receive path and the
msk destruction. Acquiring the mptcp_data_lock() in __mptcp_destroy_sock()
will not save the day: the rx path could be reached even after msk
destruction completes.
Instead use the subflow 'disposable' flag to prevent entering
the msk receive path after __mptcp_close_ssk().
Fixes: e16163b6e2b7 ("mptcp: refactor shutdown and close")
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 4e29dcf..2540d82 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -701,6 +701,13 @@ void mptcp_data_ready(struct sock *sk, struct sock *ssk)
int sk_rbuf, ssk_rbuf;
bool wake;
+ /* The peer can send data while we are shutting down this
+ * subflow at msk destruction time, but we must avoid enqueuing
+ * more data to the msk receive queue
+ */
+ if (unlikely(subflow->disposable))
+ return;
+
/* move_skbs_to_msk below can legitly clear the data_avail flag,
* but we will need later to properly woke the reader, cache its
* value
@@ -2119,6 +2126,8 @@ void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
sock_orphan(ssk);
}
+ subflow->disposable = 1;
+
/* if ssk hit tcp_done(), tcp_cleanup_ulp() cleared the related ops
* the ssk has been already destroyed, we just need to release the
* reference owned by msk;
@@ -2126,8 +2135,7 @@ void __mptcp_close_ssk(struct sock *sk, struct sock *ssk,
if (!inet_csk(ssk)->icsk_ulp_ops) {
kfree_rcu(subflow, rcu);
} else {
- /* otherwise ask tcp do dispose of ssk and subflow ctx */
- subflow->disposable = 1;
+ /* otherwise tcp will dispose of the ssk and subflow ctx */
__tcp_close(ssk, 0);
/* close acquired an extra ref */
