Serge E. Hallyn wrote: > Quoting Cedric Le Goater (clg@xxxxxxxxxx): >> 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. yes but switch_task_namespaces() assigns ->nsproxy to NULL. the result is the same. > I trust addr2line or whatever verified that rpc_create+0x332/0x42f is > exactly at the call to utsname()? yes. it points to net/sunrpc/clnt.c:216 clnt->cl_nodelen = strlen(utsname()->nodename); Thanks, C. > -serge > >> BUG: unable to handle kernel NULL pointer dereference at 00000004 >> IP: [<c024c9ab>] 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:[<c024c9ab>] 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: >> [<c0104532>] ? dump_trace+0xc2/0xe2 >> [<c01096b7>] ? save_stack_trace+0x1c/0x3a >> [<c012ca67>] ? save_trace+0x37/0x8c >> [<c012cb20>] ? add_lock_to_list+0x64/0x96 >> [<c0256fc4>] ? rpcb_register_call+0x62/0xbb >> [<c02570c8>] ? rpcb_register+0xab/0xb3 >> [<c0252f4d>] ? svc_register+0xb4/0x128 >> [<c0253114>] ? svc_destroy+0xec/0x103 >> [<c02531b2>] ? svc_exit_thread+0x87/0x8d >> [<c01a75cd>] ? lockd_down+0x61/0x81 >> [<c01a577b>] ? nlmclnt_done+0xd/0xf >> [<c01941fe>] ? nfs_destroy_server+0x14/0x16 >> [<c0194328>] ? nfs_free_server+0x4c/0xaa >> [<c019a066>] ? nfs_kill_super+0x23/0x27 >> [<c0158585>] ? deactivate_super+0x3f/0x51 >> [<c01695d1>] ? mntput_no_expire+0x95/0xb4 >> [<c016965b>] ? release_mounts+0x6b/0x7a >> [<c01696cc>] ? __put_mnt_ns+0x62/0x70 >> [<c0127501>] ? free_nsproxy+0x25/0x80 >> [<c012759a>] ? switch_task_namespaces+0x3e/0x43 >> [<c01275a9>] ? exit_task_namespaces+0xa/0xc >> [<c0117fed>] ? do_exit+0x4fd/0x666 >> [<c01181b3>] ? do_group_exit+0x5d/0x83 >> [<c011fa8c>] ? get_signal_to_deliver+0x2c8/0x2e0 >> [<c0102630>] ? do_notify_resume+0x69/0x700 >> [<c011d85a>] ? do_sigaction+0x134/0x145 >> [<c0127205>] ? hrtimer_nanosleep+0x8f/0xce >> [<c0126d1a>] ? hrtimer_wakeup+0x0/0x1c >> [<c0103488>] ? 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: [<c024c9ab>] rpc_create+0x332/0x42f SS:ESP 0068:dda0fc2c >> >> Signed-off-by: Cedric Le Goater <clg@xxxxxxxxxx> >> --- >> 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-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
