On Wed, 20 May 2020, Marcelo Ricardo Leitner wrote:

> On Wed, May 20, 2020 at 06:15:31PM +0300, Jere Leppänen wrote:
> > Commit bdf6fa52f01b ("sctp: handle association restarts when the
> > socket is closed.") starts shutdown when an association is restarted,
> > if in SHUTDOWN-PENDING state and the socket is closed. However, the
> > rationale stated in that commit applies also when in SHUTDOWN-SENT
> > state - we don't want to move an association to ESTABLISHED state when
> > the socket has been closed, because that results in an association
> > that is unreachable from user space.
> > 
> > The problem scenario:
> > 
> > 1.  Client crashes and/or restarts.
> > 
> > 2.  Server (using one-to-one socket) calls close(). SHUTDOWN is lost.
> > 
> > 3.  Client reconnects using the same addresses and ports.
> > 
> > 4.  Server's association is restarted. The association and the socket
> >     move to ESTABLISHED state, even though the server process has
> >     closed its descriptor.
> > 
> > Also, after step 4 when the server process exits, some resources are
> > leaked in an attempt to release the underlying inet sock structure in
> > ESTABLISHED state:
> > 
> >     IPv4: Attempt to release TCP socket in state 1 00000000377288c7
> > 
> > Fix by acting the same way as in SHUTDOWN-PENDING state. That is, if
> > an association is restarted in SHUTDOWN-SENT state and the socket is
> > closed, then start shutdown and don't move the association or the
> > socket to ESTABLISHED state.
> > 
> > Fixes: bdf6fa52f01b ("sctp: handle association restarts when the socket is closed.")
> > Signed-off-by: Jere Leppänen <jere.leppanen@nokia.com>
> > ---
> >  net/sctp/sm_statefuns.c | 9 +++++----
> >  1 file changed, 5 insertions(+), 4 deletions(-)
> > 
> > diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
> > index 26788f4a3b9e..e86620fbd90f 100644
> > --- a/net/sctp/sm_statefuns.c
> > +++ b/net/sctp/sm_statefuns.c
> > @@ -1856,12 +1856,13 @@ static enum sctp_disposition sctp_sf_do_dupcook_a(
> >  	/* Update the content of current association. */
> >  	sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));
> >  	sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
> > -	if (sctp_state(asoc, SHUTDOWN_PENDING) &&
> > +	if ((sctp_state(asoc, SHUTDOWN_PENDING) ||
> > +	     sctp_state(asoc, SHUTDOWN_SENT)) &&
> >  	    (sctp_sstate(asoc->base.sk, CLOSING) ||
> >  	     sock_flag(asoc->base.sk, SOCK_DEAD))) {
> > -		/* if were currently in SHUTDOWN_PENDING, but the socket
> > -		 * has been closed by user, don't transition to ESTABLISHED.
> > -		 * Instead trigger SHUTDOWN bundled with COOKIE_ACK.
> > +		/* If the socket has been closed by user, don't
> > +		 * transition to ESTABLISHED. Instead trigger SHUTDOWN
> > +		 * bundled with COOKIE_ACK.
> >  		 */
> >  		sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
> >  		return sctp_sf_do_9_2_start_shutdown(net, ep, asoc,
> > 
> > base-commit: 20a785aa52c82246055a089e55df9dac47d67da1
> 
> This last line is not standard, but git didn't complain about it here.

The git format-patch --base option. It's mentioned in the docs:

https://www.kernel.org/doc/html/v5.6/process/submitting-patches.html#providing-base-tree-information

> 
> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>

Thanks for the speedy ack, Marcelo.