Description of the problem: 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. A remote attacker can block further connection to the particular sctp server socket by sending a specially crafted sctp packet. Upstream patch: https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=d3217b15a19a4779c39b212358a5c71d725822ee diff --git a/net/sctp/associola.c b/net/sctp/associola.c index 9e0509c..9de23a2 100644 --- a/net/sctp/associola.c +++ b/net/sctp/associola.c @@ -331,7 +331,7 @@ 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 References: https://bugzilla.redhat.com/show_bug.cgi?id=1113967 Thanks, -- Petr Matousek / Red Hat Product Security