sctp: use right member as the param of list_for_each_entry

Commit d04adf1b ("sctp: reset owner sk for data chunks on out queues
when migrating a sock") made a mistake that using 'list' as the param of
list_for_each_entry to traverse the retransmit, sacked and abandoned
queues, while chunks are using 'transmitted_list' to link into these
queues.

It could cause NULL dereference panic if there are chunks in any of these
queues when peeling off one asoc.

So use the chunk member 'transmitted_list' instead in this patch.

Fixes: d04adf1b ("sctp: reset owner sk for data chunks on out queues when migrating a sock")
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Acked-by: NMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: NNeil Horman <nhorman@tuxdriver.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -188,13 +188,13 @@ static void sctp_for_each_tx_datachunk(struct sctp_association *asoc,
 		list_for_each_entry(chunk, &t->transmitted, transmitted_list)
 			cb(chunk);
 
-	list_for_each_entry(chunk, &q->retransmit, list)
+	list_for_each_entry(chunk, &q->retransmit, transmitted_list)
 		cb(chunk);
 
-	list_for_each_entry(chunk, &q->sacked, list)
+	list_for_each_entry(chunk, &q->sacked, transmitted_list)
 		cb(chunk);
 
-	list_for_each_entry(chunk, &q->abandoned, list)
+	list_for_each_entry(chunk, &q->abandoned, transmitted_list)
 		cb(chunk);
 
 	list_for_each_entry(chunk, &q->out_chunk_list, list)