[PATCH 4.19 019/142] sctp: update frag_point when stream_interleave is set

From: Greg Kroah-Hartman
Date: Fri Dec 14 2018 - 07:02:37 EST

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


From: Xin Long <lucien.xin@xxxxxxxxx>

[ Upstream commit 4135cce7fd0a0d755665c02728578c7c5afe4726 ]

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

- 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@xxxxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
Acked-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
net/sctp/associola.c | 7 ++++---
net/sctp/sm_make_chunk.c | 3 +++
2 files changed, 7 insertions(+), 3 deletions(-)

--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -118,9 +118,6 @@ static struct sctp_association *sctp_ass
asoc->flowlabel = sp->flowlabel;
asoc->dscp = sp->dscp;

- /* Initialize default path MTU. */
- asoc->pathmtu = sp->pathmtu;
/* Set association default SACK delay */
asoc->sackdelay = msecs_to_jiffies(sp->sackdelay);
asoc->sackfreq = sp->sackfreq;
@@ -252,6 +249,10 @@ static struct sctp_association *sctp_ass
0, gfp))
goto fail_init;

+ /* Initialize default path MTU. */
+ asoc->pathmtu = sp->pathmtu;
+ sctp_assoc_update_frag_point(asoc);
/* Assume that peer would support both address types unless we are
* told otherwise.
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -2462,6 +2462,9 @@ int sctp_process_init(struct sctp_associ
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;