On Tue, Sep 01, 2020 at 11:00:07AM +0200, Petr Malat wrote:

Command SCTP_CMD_PART_DELIVER issued under memory pressure calls
sctp_ulpq_partial_delivery(), which tries to fetch and partially deliver
the first message it finds without checking if the message is longer than
SCTP_PARTIAL_DELIVERY_POINT. According to the RFC 6458 paragraph 8.1.21.
such a behavior is invalid. Fix it by returning the first message only if
its part currently available is longer than SCTP_PARTIAL_DELIVERY_POINT.

Okay but AFAICT this patch then violates the basic idea behind partial
delivery. It will cause such small message to just not be delivered
anymore, and keep using the receive buffer which it is trying to free
some bits at this moment.

Btw, you also need to Cc netdev@vger.kernel.org for patches to
actually get applied by DaveM.

  Marcelo