sctp: update frag_point when stream_interleave is set

sctp_assoc_update_frag_point() should be called whenever asoc->pathmtu
changes, but we missed one place in sctp_association_init(). It would
cause frag_point is zero when sending data.

As says in Jakub's reproducer, if sp->pathmtu is set by socketopt, the
new asoc->pathmtu inherits it in sctp_association_init(). Later when
transports are added and their pmtu >= asoc->pathmtu, it will never
call sctp_assoc_update_frag_point() to set frag_point.

This patch is to fix it by updating frag_point after asoc->pathmtu is
set as sp->pathmtu in sctp_association_init(). Note that it moved them
after sctp_stream_init(), as stream->si needs to be set first.

Frag_point's calculation is also related with datachunk's type, so it
needs to update frag_point when stream->si may be changed in
sctp_process_init().

v1->v2:
  - call sctp_assoc_update_frag_point() separately in sctp_process_init
    and sctp_association_init, per Marcelo's suggestion.

Fixes: 2f5e3c9df693 ("sctp: introduce sctp_assoc_update_frag_point")
Reported-by: Jakub Audykowicz <jakub.audykowicz@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 4a4fd1971255..f4ac6c592e13 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -2462,6 +2462,9 @@ int sctp_process_init(struct sctp_association *asoc, struct sctp_chunk *chunk,
 			     asoc->c.sinit_max_instreams, gfp))
 		goto clean_up;
 
+	/* Update frag_point when stream_interleave may get changed. */
+	sctp_assoc_update_frag_point(asoc);
+
 	if (!asoc->temp && sctp_assoc_set_id(asoc, gfp))
 		goto clean_up;