From: "Serge E. Hallyn" Subject: Re: [RFC][PATCH] sunrpc: fix oops in rpc_create() when the mount namespace is unshared Date: Mon, 8 Sep 2008 10:27:49 -0500 Message-ID: <20080908152749.GA27837@hallyn.com> References: <48C52B29.4020204@fr.ibm.com> <20080908151932.GA19023@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Cedric Le Goater , Andrew Morton , "Eric W. Biederman" , Trond Myklebust , Chuck Lever , Linux Kernel Mailing List , Linux Containers , linux-nfs@vger.kernel.org To: "Serge E. Hallyn" Return-path: Received: from hrndva-omtalb.mail.rr.com ([71.74.56.123]:55166 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751640AbYIHP2F (ORCPT ); Mon, 8 Sep 2008 11:28:05 -0400 In-Reply-To: <20080908151932.GA19023@us.ibm.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: Quoting Serge E. Hallyn (serue@us.ibm.com): > Quoting Cedric Le Goater (clg-NmTC/0ZBporQT0dZR+AlfA@public.gmane.org): > > On a system with nfs mounts, if a task unshares its mount namespace, > > a oops can occur when the system is rebooted if the task is the last > > to unreference the nfs mount. It will try to create a rpc request > > using utsname() which has been invalidated by free_nsproxy(). > > > > The patch fixes the issue by using the global init_utsname() but at > > the same time, it breaks the capability of identifying rpc clients > > per uts namespace. > > > > Any better suggestions ? > > But the utsname gets freed after the mnt_ns, so the analysis seems > wrong somehow. (Oh, you straightened me out on irc - current->nsproxy is already NULL.) > I trust addr2line or whatever verified that rpc_create+0x332/0x42f is > exactly at the call to utsname()? > > -serge > > > BUG: unable to handle kernel NULL pointer dereference at 00000004 > > IP: [] rpc_create+0x332/0x42f > > Oops: 0000 [#1] DEBUG_PAGEALLOC > > > > Pid: 1857, comm: uts-oops Not tainted (2.6.27-rc5-00319-g7686ad5 #4) > > EIP: 0060:[] EFLAGS: 00210287 CPU: 0 > > EIP is at rpc_create+0x332/0x42f > > EAX: 00000000 EBX: df26adf0 ECX: c0251887 EDX: 00000001 > > ESI: df26ae58 EDI: c02f293c EBP: dda0fc9c ESP: dda0fc2c > > DS: 007b ES: 007b FS: 0000 GS: 0000 SS: 0068 > > Process uts-oops (pid: 1857, ti=dda0e000 task=dd9a0778 task.ti=dda0e000) > > Stack: c0104532 dda0fffc dda0fcac dda0e000 dda0e000 dd93b7f0 00000009 c02f2880 > > df26aefc dda0fc68 c01096b7 00000000 c0266ee0 c039a070 c039a070 dda0fc74 > > c012ca67 c039a064 dda0fc8c c012cb20 c03daf74 00000011 00000000 c0275c90 > > Call Trace: > > [] ? dump_trace+0xc2/0xe2 > > [] ? save_stack_trace+0x1c/0x3a > > [] ? save_trace+0x37/0x8c > > [] ? add_lock_to_list+0x64/0x96 > > [] ? rpcb_register_call+0x62/0xbb > > [] ? rpcb_register+0xab/0xb3 > > [] ? svc_register+0xb4/0x128 > > [] ? svc_destroy+0xec/0x103 > > [] ? svc_exit_thread+0x87/0x8d > > [] ? lockd_down+0x61/0x81 > > [] ? nlmclnt_done+0xd/0xf > > [] ? nfs_destroy_server+0x14/0x16 > > [] ? nfs_free_server+0x4c/0xaa > > [] ? nfs_kill_super+0x23/0x27 > > [] ? deactivate_super+0x3f/0x51 > > [] ? mntput_no_expire+0x95/0xb4 > > [] ? release_mounts+0x6b/0x7a > > [] ? __put_mnt_ns+0x62/0x70 > > [] ? free_nsproxy+0x25/0x80 > > [] ? switch_task_namespaces+0x3e/0x43 > > [] ? exit_task_namespaces+0xa/0xc > > [] ? do_exit+0x4fd/0x666 > > [] ? do_group_exit+0x5d/0x83 > > [] ? get_signal_to_deliver+0x2c8/0x2e0 > > [] ? do_notify_resume+0x69/0x700 > > [] ? do_sigaction+0x134/0x145 > > [] ? hrtimer_nanosleep+0x8f/0xce > > [] ? hrtimer_wakeup+0x0/0x1c > > [] ? work_notifysig+0x13/0x1b > > ======================= > > Code: 70 20 68 cb c1 2c c0 e8 75 4e 01 00 8b 83 ac 00 00 00 59 3d 00 f0 ff ff 5f 77 63 eb 57 a1 00 80 2d c0 8b 80 a8 02 00 00 8d 73 68 <8b> 40 04 83 c0 45 e8 41 46 f7 ff ba 20 00 00 00 83 f8 21 0f 4c > > EIP: [] rpc_create+0x332/0x42f SS:ESP 0068:dda0fc2c > > > > Signed-off-by: Cedric Le Goater > > --- > > net/sunrpc/clnt.c | 4 ++-- > > 1 files changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c > > index 76739e9..a59cdf4 100644 > > --- a/net/sunrpc/clnt.c > > +++ b/net/sunrpc/clnt.c > > @@ -213,10 +213,10 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru > > } > > > > /* save the nodename */ > > - clnt->cl_nodelen = strlen(utsname()->nodename); > > + clnt->cl_nodelen = strlen(init_utsname()->nodename); > > if (clnt->cl_nodelen > UNX_MAXNODENAME) > > clnt->cl_nodelen = UNX_MAXNODENAME; > > - memcpy(clnt->cl_nodename, utsname()->nodename, clnt->cl_nodelen); > > + memcpy(clnt->cl_nodename, init_utsname()->nodename, clnt->cl_nodelen); > > rpc_register_client(clnt); > > return clnt; > > > > -- > > 1.5.5.1 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/