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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 C88B7C64E75 for ; Mon, 24 Dec 2018 17:03:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 984DF21850 for ; Mon, 24 Dec 2018 17:03:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725834AbeLXRDR (ORCPT ); Mon, 24 Dec 2018 12:03:17 -0500 Received: from fieldses.org ([173.255.197.46]:55044 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725747AbeLXRDR (ORCPT ); Mon, 24 Dec 2018 12:03:17 -0500 Received: by fieldses.org (Postfix, from userid 2815) id 8DF341DCB; Mon, 24 Dec 2018 12:03:16 -0500 (EST) Date: Mon, 24 Dec 2018 12:03:16 -0500 From: "J. Bruce Fields" To: Vasily Averin Cc: Trond Myklebust , Jeff Layton , Anna Schumaker , Chuck Lever , linux-nfs@vger.kernel.org, Evgenii Shatokhin Subject: Re: [PATCH v4 00/10] use-after-free in svc_process_common() Message-ID: <20181224170316.GB11596@fieldses.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org So you fixed a bug *and* deleted a net 200 lines? Sign me up. I guess I'll plan to take this through my tree for 4.21. The patches look OK to me, I just want to run it through my testing. That make take a couple days due to the holidays. --b. On Mon, Dec 24, 2018 at 02:44:24PM +0300, Vasily Averin wrote: > v4: > - re-split, > - use direct call of svc_tcp_prep_reply_hdr() in svc_process_common() > - removed unused bc_up > - removed useless svc_tcp_bc_class and svc_rdma_bc_class > - removed unused xpo_prep_reply_hdr > > v3: > - first patch was reworked again, > instead of svc_xprt search svc_process_common() now uses > bc_prep_reply_hdr() function pointer saved on per-netns sunrpc_net. > - first patch was splitted into 5 parts. > - comments cleanup > > v2: > - first patch was reworked to satisfy Trond's requirements: > to do not assign rqstp->rq_xprt in svc_process_common() at all, > provide proper xpt_ops reference as a new parameter, > adopt functions potentially called from svc_process_common() > to properly handle rqstp->rq_xprt = NULL case. > > > nfsv41+ clients are still not properly net-namespace-filied. > > OpenVz got report on crash in svc_process_common() > abd founf that bc_svc_process() cannot use serv->sv_bc_xprt as a pointer. > > serv is global structure, but sv_bc_xprt is assigned per-netnamespace. > If nfsv41+ shares (with the same minorversion) are mounted in several containers together > then bc_svc_process() can use wrong backchannel or even access freed memory. > > OpenVz got report on crash svc_process_common(), > and after careful investigations Evgenii Shatokhin have found its reproducer. > Then I've reproduced the problem on last mainline kernel. > > In described scenario you need to have: > - nodeA: VM with 2 interfaces and debug kernel with enabled KASAN. > - nodeB: any other node > - NFS-SRV: NFSv41+ server (4.2 is used in exaple below) > > 1) nodeA: mount nfsv41+ share > # mount -t nfs4 -o vers=4.2 NFS-SRV:/export/ /mnt/ns1 > VvS: here serv->sv_bc_xprt is assigned first time, > in xs_tcp_bc_up() it is assigned to svc_xprt of mount's backchannel > > 2) nodeA: create net namespace, and mount the same (or any other) NFSv41+ share > # ip netns add second > # ip link set ens2 netns second > # ip netns exec second bash > (inside netns second) # dhclient ens2 > VvS: now nets got access to external network > (inside netns second) # mount -t nfs4 -o vers=4.2 NFS-SRV:/export/ /mnt/ns2 > VvS: now serv->sv_bc_xprt is overwritten by reference to svc_xprt of new mount's backchannel > NB: you can mount any other NFS share but minorversion must be the same. > NB2: if hardware allows you can use rdma transport here > NB3: you can access nothing in mounted share, problem's trigger was enabled already. > > 3) NodeA, destroy mount inside netns and then netns itself. > > (inside netns second) # umount /mnt/ns2 > (inside netns second) # ip link set ens2 netns 1 > (inside netns second) # exit > VvS: return to init_net > # ip netns del second > VvS: now second NFS mount and second net namespace was destroyed. > > 4) Node A: prepare backchannel event > # echo test1 > /mnt/ns1/test1.txt > # echo test2 > /mnt/ns1/test2.txt > # python > >>> fl=open('/mnt/ns1/test1.txt','r') > >>> > > 4) Node B: replace file open by NodeA > # mount -t nfs -o vers=4.2 NFS-SRV:/export/ /mnt/ > # mv /mnt/test2.txt /mnt/test1.txt > > ===> KASAN on nodeA detect an access to already freed memory. > (see dmesg example in attach of v1 patch version) > > svc_process_common() > /* Setup reply header */ > rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr(rqstp); <<< HERE > > svc_process_common() uses already freed rqstp->rq_xprt, > it was assigned in bc_svc_process() where it was taken from serv->sv_bc_xprt. > > serv->sv_bc_xprt cannot be used as a pointer, > it can be assigned per net-namespace, either in svc_bc_tcp_create() > or in xprt_rdma_bc_up(). > > According to Trond, the whole "let's set up rqstp->rq_xprt > for the back channel" is nothing but a giant hack in order > to work around the fact that svc_process_common() uses it > to find the xpt_ops, and perform a couple of (meaningless > for the back channel) tests of xpt_flags. > > All we really need in svc_process_common() is to be able to run > rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr() > > Bruce J Fields points that this xpo_prep_reply_hdr() call > is an awfully roundabout way just to do "svc_putnl(resv, 0);" > in the tcp case. > > To fix the problem svc_process_common() checks svc_rqstp->rq_prot > inherited from incoming request and if required calls > svc_tcp_prep_reply_hdr() directly. > > It was also required to store a pointer to struct net in the > struct svc_rqst so that functions called from inside > svc_process_common() (nfs4_callback_compound(), > svcauth_gss_accept() and some other) can find it. > Some other functions was adopted to handle empty rqstp->rq_xprt > > First patch switches svnauth_gss-* function to use SVC_NET() > 2nd patch fixes use-after-free itself: > to adjust reply header svc_process_common() checks prot of incoming request > and if required calls svc_tcp_prep_reply_hdr() directly > function called from svc_process_common() are adopted to properly handle > rqstp->rq_xprt = NULL > 3rd patch replaces sv_bc_xprt use in in svc_is_backchannel() > by simple boolean flag > 4rd patch removes unused bc_up calls > > 5th and 6th patches removes unused fake "transports", svc_tcp/rdma_bc_class > 7th patch removes unused xpo_prep_reply_hdr callback > Rest of patches are minor cleanup. > > Vasily Averin (10): > sunrpc: use SVC_NET() in svcauth_gss_* functions > sunrpc: use-after-free in svc_process_common() > sunrpc: replace svc_serv->sv_bc_xprt by boolean flag > sunrpc: remove unused bc_up operation from rpc_xprt_ops > sunrpc: remove svc_tcp_bc_class > sunrpc: remove svc_rdma_bc_class > sunrpc: remove unused xpo_prep_reply_hdr callback > sunrpc: make visible processing error in bc_svc_process() > sunrpc: fix debug message in svc_create_xprt() > nfs: minor typo in nfs4_callback_up_net() > > fs/nfs/callback.c | 10 +- > include/linux/sunrpc/bc_xprt.h | 10 +- > include/linux/sunrpc/svc.h | 7 +- > include/linux/sunrpc/svc_rdma.h | 1 - > include/linux/sunrpc/svc_xprt.h | 1 - > include/linux/sunrpc/xprt.h | 1 - > include/trace/events/sunrpc.h | 6 +- > net/sunrpc/auth_gss/svcauth_gss.c | 8 +- > net/sunrpc/svc.c | 24 +++-- > net/sunrpc/svc_xprt.c | 9 +- > net/sunrpc/svcsock.c | 120 ----------------------- > net/sunrpc/xprtrdma/backchannel.c | 20 ---- > net/sunrpc/xprtrdma/svc_rdma.c | 6 -- > net/sunrpc/xprtrdma/svc_rdma_sendto.c | 4 - > net/sunrpc/xprtrdma/svc_rdma_transport.c | 59 ----------- > net/sunrpc/xprtrdma/transport.c | 1 - > net/sunrpc/xprtrdma/xprt_rdma.h | 1 - > net/sunrpc/xprtsock.c | 12 --- > 18 files changed, 46 insertions(+), 254 deletions(-) > > -- > 2.17.1