Return-Path: linux-nfs-owner@vger.kernel.org Received: from mail-vc0-f179.google.com ([209.85.220.179]:56084 "EHLO mail-vc0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750839AbbAYVzW convert rfc822-to-8bit (ORCPT ); Sun, 25 Jan 2015 16:55:22 -0500 Received: by mail-vc0-f179.google.com with SMTP id la4so1806184vcb.10 for ; Sun, 25 Jan 2015 13:55:21 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20150125220604.090121ae@neptune.home> References: <20150125220604.090121ae@neptune.home> Date: Sun, 25 Jan 2015 16:55:20 -0500 Message-ID: Subject: Re: [Patch] sunrpc: NULL utsname dereference on NFS umount during namespace cleanup From: Trond Myklebust To: =?UTF-8?Q?Bruno_Pr=C3=A9mont?= Cc: "J. Bruce Fields" , "Eric W. Biederman" , Linux Kernel Mailing List , Linux NFS Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-nfs-owner@vger.kernel.org List-ID: On Sun, Jan 25, 2015 at 4:06 PM, Bruno Prémont wrote: > On a system running home-brown container (mntns, utsns, pidns, netns) > with NFS mount-point bind-mounted into the container I hit the following > trace if nfs filesystem is first umount()ed in init ns and then later > umounted from container when the container exists. > > [51397.767310] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008 > [51397.770671] IP: [] rpc_new_client+0x193/0x2b0 > [51397.773967] PGD 0 > [51397.777218] Oops: 0000 [#1] SMP > [51397.780490] Modules linked in: > [51397.783751] CPU: 0 PID: 1711 Comm: image-starter Not tainted 3.19.0-rc2-kvm+ #7 > [51397.787123] Hardware name: Gigabyte Technology Co., Ltd. GA-A75M-UD2H/GA-A75M-UD2H, BIOS F6 09/28/2012 > [51397.790606] task: ffff8800c9fcbac0 ti: ffff8801fe754000 task.ti: ffff8801fe754000 > [51397.794149] RIP: 0010:[] [] rpc_new_client+0x193/0x2b0 > [51397.797798] RSP: 0018:ffff8801fe757908 EFLAGS: 00010246 > [51397.801444] RAX: 0000000000000000 RBX: ffff88009dafb240 RCX: 0000000000000180 > [51397.805174] RDX: 000000000000bae0 RSI: 0000000000001770 RDI: ffff88009dafb308 > [51397.808913] RBP: ffff8801fe757948 R08: ffff88009daf92d8 R09: ffff88009dafb458 > [51397.812673] R10: ffff88009dafb458 R11: ffff88020ec15bc0 R12: ffff8801fe757a40 > [51397.816456] R13: ffffffff81b9d800 R14: ffff8800c6e31030 R15: 0000000000000000 > [51397.820270] FS: 00007f335a3a1700(0000) GS:ffff88020ec00000(0000) knlGS:00000000f7287700 > [51397.824168] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > [51397.828066] CR2: 0000000000000008 CR3: 00000001fc54d000 CR4: 00000000000007f0 > [51397.832017] Stack: > [51397.835924] 000000000000000a ffffffff81b9d770 ffffffff81826450 ffff8801fe757a40 > [51397.840023] ffff8801fe757a40 ffff8800cf08d500 ffffffff81826450 ffffffff820f4728 > [51397.844130] ffff8801fe757978 ffffffff81828815 ffff8801fe757978 ffffffff8182aad8 > [51397.848224] Call Trace: > [51397.852221] [] ? call_start+0x20/0x20 > [51397.856273] [] ? call_start+0x20/0x20 > [51397.860295] [] rpc_create_xprt+0x15/0xb0 > [51397.864324] [] ? xprt_create_transport+0x108/0x1b0 > [51397.868428] [] rpc_create+0xc1/0x190 > [51397.872574] [] ? internal_add_timer+0x66/0x80 > [51397.876733] [] ? mod_timer+0x109/0x1e0 > [51397.880877] [] rpcb_create+0x6e/0x90 > [51397.884999] [] rpcb_getport_async+0x15a/0x330 > [51397.889118] [] ? rpc_malloc+0x3a/0x70 > [51397.893240] [] ? __kmalloc+0xc2/0x170 > [51397.897354] [] ? call_reserveresult+0x110/0x110 > [51397.901490] [] ? call_start+0x20/0x20 > [51397.905606] [] ? call_start+0x20/0x20 > [51397.909662] [] call_bind+0x3e/0x40 > [51397.913709] [] __rpc_execute+0x79/0x330 > [51397.917778] [] rpc_execute+0x5d/0xa0 > [51397.921871] [] rpc_run_task+0x6b/0x90 > [51397.925989] [] rpc_call_sync+0x3e/0xa0 > [51397.930108] [] nsm_mon_unmon+0xb9/0xd0 > [51397.934191] [] ? call_rcu_bh+0x20/0x20 > [51397.938235] [] nsm_unmonitor+0x8c/0x140 > [51397.942309] [] nlm_destroy_host_locked+0x63/0xa0 > [51397.946442] [] nlmclnt_release_host+0x7c/0x130 > [51397.950591] [] nlmclnt_done+0x15/0x30 > [51397.954773] [] nfs_destroy_server+0x12/0x20 > [51397.958934] [] nfs_free_server+0x22/0xa0 > [51397.963053] [] nfs_kill_super+0x1d/0x30 > [51397.967158] [] deactivate_locked_super+0x4c/0x70 > [51397.971286] [] deactivate_super+0x49/0x70 > [51397.975398] [] cleanup_mnt+0x3e/0x90 > [51397.979499] [] __cleanup_mnt+0xd/0x10 > [51397.983598] [] task_work_run+0xbc/0xe0 > [51397.987697] [] do_exit+0x295/0xaf0 > [51397.991812] [] ? ____fput+0x9/0x10 > [51397.995937] [] ? task_work_run+0xa4/0xe0 > [51398.000070] [] do_group_exit+0x3a/0xa0 > [51398.004201] [] SyS_exit_group+0xf/0x10 > [51398.008315] [] system_call_fastpath+0x12/0x17 > [51398.012438] Code: 43 78 48 8d bb c8 00 00 00 48 89 7b 70 48 8b 30 e8 63 2d 01 00 c7 03 01 00 00 00 65 48 8b 04 25 00 aa 00 00 48 8b 80 c0 09 00 00 <4c> 8b 68 08 49 83 c5 45 4 > [51398.022378] RIP [] rpc_new_client+0x193/0x2b0 > [51398.026732] RSP > [51398.031025] CR2: 0000000000000008 > [51398.035326] ---[ end trace b701b037bc457620 ]--- > [51398.058223] Fixing recursive fault but reboot is needed! > > > The code executed in rpc_new_client() tries to dereference the > struct new_utsname * returned by utsname() which has already been > released at this time. > > Cc: # 3.18 > Signed-off-by: Bruno Prémont > --- > I've seen this trace on 3.18.x as well as 3.19-rc. > > > This patch fixes the NULL dereference but I'm not sure this is the > right fix. > Should init uts_ns be referred to or what is the impact of using a random > string to satisfy rpc_clnt_set_nodename()? > > Thanks, > Bruno > --- > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c > index 05da12a..0246e94 100644 > --- a/net/sunrpc/clnt.c > +++ b/net/sunrpc/clnt.c > @@ -365,6 +365,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, > const struct rpc_version *version; > struct rpc_clnt *clnt = NULL; > const struct rpc_timeout *timeout; > + const struct new_utsname *uts_name; > int err; > > /* sanity check the name before trying to print it */ > @@ -421,7 +422,8 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, > atomic_set(&clnt->cl_count, 1); > > /* save the nodename */ > - rpc_clnt_set_nodename(clnt, utsname()->nodename); > + uts_name = utsname(); > + rpc_clnt_set_nodename(clnt, uts_name ? uts_name->nodename : ""); > > err = rpc_client_register(clnt, args->authflavor, args->client_name); > if (err) We should rather change rpcb_create() to pass the nodename from the parent. The point is that the rpc_clnt->cl_nodename is used in various different contexts (for instance in the AUTH_SYS credential) where it isn't always appropriate to have it set to an empty string. -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@primarydata.com