3.10.y regression caused by: lockd: ensure we tear down any live sockets when socket creation fails during lockd_up

[Nikita Yushchenko <nyushchenko@dev.rtsoft.ru>]

With current 3.10.y, if kernel is booted with init=/bin/sh and then nfs mount
is attempted (without portmap or rpcbind running) using busybox mount, following
OOPS happen:

# mount -t nfs 10.30.130.21:/opt /mnt
svc: failed to register lockdv1 RPC service (errno 111).
lockd_up: makesock failed, error=-111
Unable to handle kernel paging request for data at address 0x00000030
Faulting instruction address: 0xc055e65c
Oops: Kernel access of bad area, sig: 11 [#1]
MPC85xx CDS
Modules linked in:
CPU: 0 PID: 1338 Comm: mount Not tainted 3.10.44.cge #117
task: cf29cea0 ti: cf35c000 task.ti: cf35c000
NIP: c055e65c LR: c0566490 CTR: c055e648
REGS: cf35dad0 TRAP: 0300   Not tainted  (3.10.44.cge)
MSR: 00029000 <CE,EE,ME>  CR: 22442488  XER: 20000000
DEAR: 00000030, ESR: 00000000

GPR00: c05606f4 cf35db80 cf29cea0 cf0ded80 cf0dedb8 00000001 1dec3086 00000000 
GPR08: 00000000 c07b1640 00000007 1dec3086 22442482 100b9758 00000000 10090ae8 
GPR16: 00000000 000186a5 00000000 00000000 100c3018 bfa46edc 100b0000 bfa46ef0 
GPR24: cf386ae0 c07834f0 00000000 c0565f88 00000001 cf0dedb8 00000000 cf0ded80 
NIP [c055e65c] call_start+0x14/0x34
LR [c0566490] __rpc_execute+0x70/0x250
Call Trace:
[cf35db80] [00000080] 0x80 (unreliable)
[cf35dbb0] [c05606f4] rpc_run_task+0x9c/0xc4
[cf35dbc0] [c0560840] rpc_call_sync+0x50/0xb8
[cf35dbf0] [c056ee90] rpcb_register_call+0x54/0x84
[cf35dc10] [c056f24c] rpcb_register+0xf8/0x10c
[cf35dc70] [c0569e18] svc_unregister.isra.23+0x100/0x108
[cf35dc90] [c0569e38] svc_rpcb_cleanup+0x18/0x30
[cf35dca0] [c0198c5c] lockd_up+0x1dc/0x2e0
[cf35dcd0] [c0195348] nlmclnt_init+0x2c/0xc8
[cf35dcf0] [c015bb5c] nfs_start_lockd+0x98/0xec
[cf35dd20] [c015ce6c] nfs_create_server+0x1e8/0x3f4
[cf35dd90] [c0171590] nfs3_create_server+0x10/0x44
[cf35dda0] [c016528c] nfs_try_mount+0x158/0x1e4
[cf35de20] [c01670d0] nfs_fs_mount+0x434/0x8c8
[cf35de70] [c00cd3bc] mount_fs+0x20/0xbc
[cf35de90] [c00e4f88] vfs_kern_mount+0x50/0x104
[cf35dec0] [c00e6e0c] do_mount+0x1d0/0x8e0
[cf35df10] [c00e75ac] SyS_mount+0x90/0xd0
[cf35df40] [c000ccf4] ret_from_syscall+0x0/0x3c
--- Exception: c01 at 0xff2acc4
    LR = 0x10048ab8
Instruction dump:
3d20c056 3929e648 91230028 38600001 4e800020 38600000 4e800020 81230014 
8103000c 81490014 394a0001 91490014 <81280030> 81490018 394a0001 91490018 
---[ end trace 033b5b4715cb5452 ]---


This does not happen if

commit 72a6e594497032bd911bd187a88fae4b4473abb3
Author: Jeff Layton <jlayton@redhat.com>
Date:   Tue Mar 25 11:55:26 2014 -0700

    lockd: ensure we tear down any live sockets when socket creation fails during lockd_up
    
    commit 679b033df48422191c4cac52b610d9980e019f9b upstream.

is reverted:

# mount -t nfs 10.30.130.21:/opt /mnt
svc: failed to register lockdv1 RPC service (errno 111).
lockd_up: makesock failed, error=-111
mount: mounting 10.30.130.21:/opt on /mnt failed: Connection refused
#


Physical reason of the OOPS is that:

- addition of svc_shutdown_net() call to error path of make_socks() causes
double call of svc_rpcb_cleanup():
  - first call is from within svc_shutdown_net(), because serv->sv_shutdown
points to svc_rpcb_cleanup() at this time,
  - immediately followed by second call from lockd_up_net()'s error path

- when second svc_rpcb_cleanup() is executed, then at
  svc_unregister() -> __svc_unregister() -> rpcb_register() -> rpcb_register_call()
call path, rpcb_register_call() is called with clnt=NULL.