4.9-stable review patch.  If anyone has any objections, please let me know.


From: Xin Long <lucien....@gmail.com>

[ Upstream commit d30fc5126efb0c33b7adf5966d3051db2c3d7721 ]

Now outstanding_bytes is only increased when appending chunks into one
packet and sending it at 1st time, while decreased when it is about to
move into retransmit queue. It means outstanding_bytes value is already
decreased for all chunks in retransmit queue.

However sctp_prsctp_prune_sent is a common function to check the chunks
in both transmitted and retransmit queue, it decrease outstanding_bytes
when moving a chunk into abandoned queue from either of them.

It could cause outstanding_bytes underflow, as it also decreases it's
value for the chunks in retransmit queue.

This patch fixes it by only updating outstanding_bytes for transmitted
queue when pruning queues for prsctp prio policy, the same fix is also
needed in sctp_check_transmitted.

Fixes: 8dbdf1f5b09c ("sctp: implement prsctp PRIO policy")
Signed-off-by: Xin Long <lucien....@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
 net/sctp/outqueue.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/sctp/outqueue.c
+++ b/net/sctp/outqueue.c
@@ -364,7 +364,8 @@ static int sctp_prsctp_prune_sent(struct
-               if (!chk->tsn_gap_acked) {
+               if (queue != &asoc->outqueue.retransmit &&
+                   !chk->tsn_gap_acked) {
                        if (chk->transport)
                                chk->transport->flight_size -=
@@ -1409,7 +1410,8 @@ static void sctp_check_transmitted(struc
                        /* If this chunk has not been acked, stop
                         * considering it as 'outstanding'.
-                       if (!tchunk->tsn_gap_acked) {
+                       if (transmitted_queue != &q->retransmit &&
+                           !tchunk->tsn_gap_acked) {
                                if (tchunk->transport)
                                        tchunk->transport->flight_size -=

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