From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: [PATCH net] net: sctp: fix NULL pointer dereference in af->from_addr_param on malformed packet Date: Tue, 11 Nov 2014 07:05:17 -0500 Message-ID: <20141111120517.GA31973@hmsreliant.think-freely.org> References: <1415638466-20176-1-git-send-email-dborkman@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: davem@davemloft.net, linux-sctp@vger.kernel.org, netdev@vger.kernel.org, Vlad Yasevich To: Daniel Borkmann Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:39504 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751089AbaKKMFb (ORCPT ); Tue, 11 Nov 2014 07:05:31 -0500 Content-Disposition: inline In-Reply-To: <1415638466-20176-1-git-send-email-dborkman@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: On Mon, Nov 10, 2014 at 05:54:26PM +0100, Daniel Borkmann wrote: > An SCTP server doing ASCONF will panic on malformed INIT ping-of-death > in the form of: > > ------------ INIT[PARAM: SET_PRIMARY_IP] ------------> > > While the INIT chunk parameter verification dissects through many things > in order to detect malformed input, it misses to actually check parameters > inside of parameters. E.g. RFC5061, section 4.2.4 proposes a 'set primary > IP address' parameter in ASCONF, which has as a subparameter an address > parameter. > > So an attacker may send a parameter type other than SCTP_PARAM_IPV4_ADDRESS > or SCTP_PARAM_IPV6_ADDRESS, param_type2af() will subsequently return 0 > and thus sctp_get_af_specific() returns NULL, too, which we then happily > dereference unconditionally through af->from_addr_param(). > > The trace for the log: > > BUG: unable to handle kernel NULL pointer dereference at 0000000000000078 > IP: [] sctp_process_init+0x492/0x990 [sctp] > PGD 0 > Oops: 0000 [#1] SMP > [...] > Pid: 0, comm: swapper Not tainted 2.6.32-504.el6.x86_64 #1 Bochs Bochs > RIP: 0010:[] [] sctp_process_init+0x492/0x990 [sctp] > [...] > Call Trace: > > [] ? sctp_bind_addr_copy+0x5d/0xe0 [sctp] > [] sctp_sf_do_5_1B_init+0x21b/0x340 [sctp] > [] sctp_do_sm+0x71/0x1210 [sctp] > [] ? sctp_endpoint_lookup_assoc+0xc9/0xf0 [sctp] > [] sctp_endpoint_bh_rcv+0x116/0x230 [sctp] > [] sctp_inq_push+0x56/0x80 [sctp] > [] sctp_rcv+0x982/0xa10 [sctp] > [] ? ipt_local_in_hook+0x23/0x28 [iptable_filter] > [] ? nf_iterate+0x69/0xb0 > [] ? ip_local_deliver_finish+0x0/0x2d0 > [] ? nf_hook_slow+0x76/0x120 > [] ? ip_local_deliver_finish+0x0/0x2d0 > [...] > > A minimal way to address this is to check for NULL as we do on all > other such occasions where we know sctp_get_af_specific() could > possibly return with NULL. > > Fixes: d6de3097592b ("[SCTP]: Add the handling of "Set Primary IP Address" parameter to INIT") > Signed-off-by: Daniel Borkmann > Cc: Vlad Yasevich > --- > net/sctp/sm_make_chunk.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c > index ab734be..9f32741 100644 > --- a/net/sctp/sm_make_chunk.c > +++ b/net/sctp/sm_make_chunk.c > @@ -2609,6 +2609,9 @@ do_addr_param: > addr_param = param.v + sizeof(sctp_addip_param_t); > > af = sctp_get_af_specific(param_type2af(param.p->type)); > + if (af == NULL) > + break; > + > af->from_addr_param(&addr, addr_param, > htons(asoc->peer.port), 0); > > -- > 1.7.11.7 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-sctp" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Acked-by: Neil Horman