On Wed, Mar 18, 2020 at 1:30 AM Marcelo Ricardo Leitner
[off-list ref] wrote:

Hi,

On Tue, Mar 17, 2020 at 11:55:36PM +0800, Qiujun Huang wrote:

quoted

Do accounting for skb's real sk.
In some case skb->sk != asoc->base.sk:

migrate routing        sctp_check_transmitted routing
------------                    ---------------

                                 sctp_close();
                                   lock_sock(sk2);
                                 sctp_primitive_ABORT();
                                 sctp_do_sm();
                                 sctp_cmd_interpreter();
                                 sctp_cmd_process_sack();
                                 sctp_outq_sack();
                                 sctp_check_transmitted();

  lock_sock(sk1);
  sctp_getsockopt_peeloff();
  sctp_do_peeloff();
  sctp_sock_migrate();

quoted

lock_sock_nested(sk2);
                               mv the transmitted skb to
                               the it's local tlist

How can sctp_do_sm() be called in the 2nd column so that it bypasses
the locks in the left column, allowing this mv to happen?

quoted

sctp_for_each_tx_datachunk(
sctp_clear_owner_w);
sctp_assoc_migrate();
sctp_for_each_tx_datachunk(
sctp_set_owner_w);

                               put the skb back to the
                               assoc lists
----------------------------------------------------

The skbs which held bysctp_check_transmitted were not changed
to newsk. They were not dealt with by sctp_for_each_tx_datachunk
(sctp_clear_owner_w/sctp_set_owner_w).

It would make sense but I'm missing one step earlier, I'm not seeing
how the move to local list is allowed/possible in there. It really
shouldn't be possible.

I totally agree that.
My mistake. So I added some log in my test showing the case:
The backtrace:
sctp_close
sctp_primitive_ABORT
sctp_do_sm
sctp_association_free
__sctp_outq_teardown
     /* Throw away unacknowledged chunks. */
    list_for_each_entry(transport, &q->asoc->peer.transport_addr_list,
    transports) {
    printk("[%d]deal with transmitted %#llx from transport %#llx  %s,
%d\n", raw_smp_processor_id(),
   &transport->transmitted, transport, __func__, __LINE__);
   while ((lchunk = sctp_list_dequeue(&transport->transmitted)) != NULL) {

The trouble skb is from another peer sk in the same asoc, but
accounted to the base.sk.