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mptcp: be careful on subflows shutdown

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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: e16163b6e2 ("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>
This commit is contained in:
Paolo Abeni 2020-12-09 12:03:31 +01:00 committed by David S. Miller
parent 0597d0f8e0
commit d7b1bfd083
1 changed files with 10 additions and 2 deletions
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12
net/mptcp/protocol.c
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@ -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 */