Patch "sctp: fix missing wake ups in some situations" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

sctp: fix missing wake ups in some situations

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
sctp-fix-missing-wake-ups-in-some-situations.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Marcelo Ricardo Leitner <[email protected]>
Date: Fri, 8 Sep 2017 11:35:21 -0300
Subject: sctp: fix missing wake ups in some situations

From: Marcelo Ricardo Leitner <[email protected]>

[ Upstream commit 7906b00f5cd1cd484fced7fcda892176e3202c8a ]

Commit fb586f25300f ("sctp: delay calls to sk_data_ready() as much as possible") minimized the number of wake ups that are triggered in case the association receives a packet with multiple data chunks on it and/or when io_events are enabled and then commit 0970f5b36659 ("sctp: signal sk_data_ready earlier on data chunks reception") moved the wake up to as soon as possible. It thus relies on the state machine running later to clean the flag that the event was already generated.

The issue is that there are 2 call paths that calls sctp_ulpq_tail_event() outside of the state machine, causing the flag to linger and possibly omitting a needed wake up in the sequence.

One of the call paths is when enabling SCTP_SENDER_DRY_EVENTS via setsockopt(SCTP_EVENTS), as noticed by Harald Welte. The other is when partial reliability triggers removal of chunks from the send queue when the application calls sendmsg().

This commit fixes it by not setting the flag in case the socket is not owned by the user, as it won't be cleaned later. This works for user-initiated calls and also for rx path processing.

---
 net/sctp/ulpqueue.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -265,7 +265,8 @@ int sctp_ulpq_tail_event(struct sctp_ulp
 		sctp_ulpq_clear_pd(ulpq);
 
 	if (queue == &sk->sk_receive_queue && !sp->data_ready_signalled) {
-		sp->data_ready_signalled = 1;
+		if (!sock_owned_by_user(sk))
+			sp->data_ready_signalled = 1;
 		sk->sk_data_ready(sk);
 	}
 	return 1;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/sctp-avoid-out-of-bounds-reads-from-address-storage.patch queue-4.9/sctp-fix-missing-wake-ups-in-some-situations.patch