sctp: Fix sk_ack_backlog wrap-around problem

Consider the scenario:
For a TCP-style socket, while processing the COOKIE_ECHO chunk in
sctp_sf_do_5_1D_ce(), after it has passed a series of sanity check,
a new association would be created in sctp_unpack_cookie(), but afterwards,
some processing maybe failed, and sctp_association_free() will be called to
free the previously allocated association, in sctp_association_free(),
sk_ack_backlog value is decremented for this socket, since the initial
value for sk_ack_backlog is 0, after the decrement, it will be 65535,
a wrap-around problem happens, and if we want to establish new associations
afterward in the same socket, ABORT would be triggered since sctp deem the
accept queue as full.
Fix this issue by only decrementing sk_ack_backlog for associations in
the endpoint's list.

Change-Id: I99853431b7852609412a3d48c8a6e96cd489e9fc
Fix-suggested-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>
Acked-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sctp/associola.c b/net/sctp/associola.c
index cef509985192a041f8d437adc35cd540e32f58bd..f6d6dcd1f97dc708fa2da517bba896dd98948138 100644 (file)
--- a/net/sctp/associola.c
+++ b/net/sctp/associola.c
@@ -375,7 +375,7 @@ void sctp_association_free(struct sctp_association *asoc)
        /* Only real associations count against the endpoint, so
         * don't bother for if this is a temporary association.
         */
-       if (!asoc->temp) {
+       if (!list_empty(&asoc->asocs)) {
                list_del(&asoc->asocs);
 
                /* Decrement the backlog value for a TCP-style listening