From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 15DBAECE58D for ; Wed, 9 Oct 2019 15:28:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE229218DE for ; Wed, 9 Oct 2019 15:28:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731829AbfJIP2D (ORCPT ); Wed, 9 Oct 2019 11:28:03 -0400 Received: from charlotte.tuxdriver.com ([70.61.120.58]:33116 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731822AbfJIP2B (ORCPT ); Wed, 9 Oct 2019 11:28:01 -0400 Received: from cpe-2606-a000-111b-43ee-0-0-0-115f.dyn6.twc.com ([2606:a000:111b:43ee::115f] helo=localhost) by smtp.tuxdriver.com with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.63) (envelope-from ) id 1iIDsV-000651-EY; Wed, 09 Oct 2019 11:27:58 -0400 Date: Wed, 9 Oct 2019 11:27:46 -0400 From: Neil Horman To: Xin Long Cc: network dev , linux-sctp@vger.kernel.org, davem@davemloft.net, Marcelo Ricardo Leitner , omosnace@redhat.com Subject: Re: [PATCH net] sctp: add chunks to sk_backlog when the newsk sk_socket is not set Message-ID: <20191009152746.GA25555@hmswarspite.think-freely.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Oct 08, 2019 at 07:09:23PM +0800, Xin Long wrote: > This patch is to fix a NULL-ptr deref in selinux_socket_connect_helper: > > [...] kasan: GPF could be caused by NULL-ptr deref or user memory access > [...] RIP: 0010:selinux_socket_connect_helper+0x94/0x460 > [...] Call Trace: > [...] selinux_sctp_bind_connect+0x16a/0x1d0 > [...] security_sctp_bind_connect+0x58/0x90 > [...] sctp_process_asconf+0xa52/0xfd0 [sctp] > [...] sctp_sf_do_asconf+0x785/0x980 [sctp] > [...] sctp_do_sm+0x175/0x5a0 [sctp] > [...] sctp_assoc_bh_rcv+0x285/0x5b0 [sctp] > [...] sctp_backlog_rcv+0x482/0x910 [sctp] > [...] __release_sock+0x11e/0x310 > [...] release_sock+0x4f/0x180 > [...] sctp_accept+0x3f9/0x5a0 [sctp] > [...] inet_accept+0xe7/0x720 > > It was caused by that the 'newsk' sk_socket was not set before going to > security sctp hook when processing asconf chunk with SCTP_PARAM_ADD_IP > or SCTP_PARAM_SET_PRIMARY: > > inet_accept()-> > sctp_accept(): > lock_sock(): > lock listening 'sk' > do_softirq(): > sctp_rcv(): <-- [1] > asconf chunk arrives and > enqueued in 'sk' backlog > sctp_sock_migrate(): > set asoc's sk to 'newsk' > release_sock(): > sctp_backlog_rcv(): > lock 'newsk' > sctp_process_asconf() <-- [2] > unlock 'newsk' > sock_graft(): > set sk_socket <-- [3] > > As it shows, at [1] the asconf chunk would be put into the listening 'sk' > backlog, as accept() was holding its sock lock. Then at [2] asconf would > get processed with 'newsk' as asoc's sk had been set to 'newsk'. However, > 'newsk' sk_socket is not set until [3], while selinux_sctp_bind_connect() > would deref it, then kernel crashed. > > Here to fix it by adding the chunk to sk_backlog until newsk sk_socket is > set when .accept() is done. > > Note that sk->sk_socket can be NULL when the sock is closed, so SOCK_DEAD > flag is also needed to check in sctp_newsk_ready(). > > Thanks to Ondrej for reviewing the code. > > Fixes: d452930fd3b9 ("selinux: Add SCTP support") > Reported-by: Ying Xu > Suggested-by: Marcelo Ricardo Leitner > Signed-off-by: Xin Long > --- > include/net/sctp/sctp.h | 5 +++++ > net/sctp/input.c | 12 +++++++++--- > 2 files changed, 14 insertions(+), 3 deletions(-) > > diff --git a/include/net/sctp/sctp.h b/include/net/sctp/sctp.h > index 5d60f13..3ab5c6b 100644 > --- a/include/net/sctp/sctp.h > +++ b/include/net/sctp/sctp.h > @@ -610,4 +610,9 @@ static inline __u32 sctp_min_frag_point(struct sctp_sock *sp, __u16 datasize) > return sctp_mtu_payload(sp, SCTP_DEFAULT_MINSEGMENT, datasize); > } > > +static inline bool sctp_newsk_ready(const struct sock *sk) > +{ > + return sock_flag(sk, SOCK_DEAD) || sk->sk_socket; > +} > + > #endif /* __net_sctp_h__ */ > diff --git a/net/sctp/input.c b/net/sctp/input.c > index 5a070fb..f277137 100644 > --- a/net/sctp/input.c > +++ b/net/sctp/input.c > @@ -243,7 +243,7 @@ int sctp_rcv(struct sk_buff *skb) > bh_lock_sock(sk); > } > > - if (sock_owned_by_user(sk)) { > + if (sock_owned_by_user(sk) || !sctp_newsk_ready(sk)) { > if (sctp_add_backlog(sk, skb)) { > bh_unlock_sock(sk); > sctp_chunk_free(chunk); > @@ -321,7 +321,7 @@ int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb) > local_bh_disable(); > bh_lock_sock(sk); > > - if (sock_owned_by_user(sk)) { > + if (sock_owned_by_user(sk) || !sctp_newsk_ready(sk)) { > if (sk_add_backlog(sk, skb, sk->sk_rcvbuf)) > sctp_chunk_free(chunk); > else > @@ -336,7 +336,13 @@ int sctp_backlog_rcv(struct sock *sk, struct sk_buff *skb) > if (backloged) > return 0; > } else { > - sctp_inq_push(inqueue, chunk); > + if (!sctp_newsk_ready(sk)) { > + if (!sk_add_backlog(sk, skb, sk->sk_rcvbuf)) > + return 0; > + sctp_chunk_free(chunk); > + } else { > + sctp_inq_push(inqueue, chunk); > + } > } > > done: > -- > 2.1.0 > > Acked-by: Neil Horman