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=-1.0 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS 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 DFA7FC43387 for ; Fri, 21 Dec 2018 17:31:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AB8EC21917 for ; Fri, 21 Dec 2018 17:31:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390160AbeLURbb (ORCPT ); Fri, 21 Dec 2018 12:31:31 -0500 Received: from relay.sw.ru ([185.231.240.75]:40664 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731522AbeLURbb (ORCPT ); Fri, 21 Dec 2018 12:31:31 -0500 Received: from [172.16.24.21] by relay.sw.ru with esmtp (Exim 4.91) (envelope-from ) id 1gaOdv-0004s8-4h; Fri, 21 Dec 2018 20:31:23 +0300 From: Vasily Averin Subject: [PATCH v3 0/8] use-after-free in svc_process_common() To: Trond Myklebust , Anna Schumaker Cc: "J. Bruce Fields" , Jeff Layton , Chuck Lever , linux-nfs@vger.kernel.org, Evgenii Shatokhin Message-ID: <3c84476a-ce26-1171-b6e3-42d6ca3dc6e5@virtuozzo.com> Date: Fri, 21 Dec 2018 20:31:22 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.2.1 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org 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(). (Hopefully both transports cannot be used together in the same netns) To fix this problem I've added new callback to struct rpc_xprt_ops, it calls svc_find_xprt with proper name of transport's backchannel. 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. Trond proposed to pass in the xpt_ops as a new parameter to svc_process_common(), and make those xpt_flags tests check for whether or not rqstp->rq_xprt is actually non-NULL. It 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 now switches svnauth_gss-* function to use SVC_NET() 2nd patch introduces svc_rqst->rq_bc_net used during processing of back channel requests 3rd patch introduces sunrpc_net->bc_prep_reply_hdr function pointer 4rd patch is fix of use-after-free 5th patch replaces sv_bc_xprt pointer to boolean flag, serv->sv_bc_xprt is used in svc_is_backchannel() too. Here this field is used not as pointer but as some mark of back channel-compatible svc servers. Rest of patches are minor cleanup. Vasily Averin (8): sunrpc: use SVC_NET() in svcauth_gss_* functions sunrpc: introduce svc_rqst->rq_bc_net sunrpc: introduce per-netns sunrpc_net->bc_prep_reply_hdr() sunrpc: use-after-free in svc_process_common() nfs: remove sv_bc_enabled using in svc_is_backchannel() 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 | 2 +- include/linux/sunrpc/bc_xprt.h | 10 ++++------ include/linux/sunrpc/svc.h | 8 +++++--- include/trace/events/sunrpc.h | 6 ++++-- net/sunrpc/auth_gss/svcauth_gss.c | 8 ++++---- net/sunrpc/netns.h | 2 ++ net/sunrpc/svc.c | 22 +++++++++++++++------- net/sunrpc/svc_xprt.c | 14 ++++++++++---- net/sunrpc/svcsock.c | 5 ++++- net/sunrpc/xprtrdma/svc_rdma_transport.c | 2 +- 10 files changed, 50 insertions(+), 29 deletions(-) -- 2.17.1