Staging: vt6656: fix the memory free bug in vntwusb_disconnect()

Staging: vt6656: fix the memory free bug in vntwusb_disconnect()

This patch is used to solve the memory bug when people plug out the wusb card then plug in.
Error logs are following:

root@smdk2440:~# ifdown eth1
AP deauthed me, reason=2.
Config_FileOperation file Not exist
Zone=[1][J][P]!!
WPA: Terminating
root@smdk2440:~#  ----> !!!!!!!!!!!!!!here plug out the wusbcard
usb 1-1: USB disconnect, address 4
----> !!!!!!!!!!!!!!!!!!!here plug in the wusb card
usb 1-1: new full speed USB device using s3c2410-ohci and address 5
usb 1-1: New USB device found, idVendor=160a, idProduct=3184
usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
usb 1-1: Product: VNT USB-802.11 Wireless LAN Adapter
usb 1-1: Manufacturer: VIA Networking Technologies, Inc.
usb 1-1: configuration #1 chosen from 1 choice
VIA Networking Wireless LAN USB Driver Ver. 1.19_12
Copyright (c) 2004 VIA Networking Technologies, Inc.
kernel BUG at mm/slab.c:2974!
Unable to handle kernel NULL pointer dereference at virtual address 00000000
pgd = c0004000
[00000000] *pgd=00000000
Internal error: Oops: 817 [#1] PREEMPT
Modules linked in: vt6656_stage
CPU: 0    Not tainted  (2.6.32-rc2 #14)
PC is at __bug+0x1c/0x28
LR is at __bug+0x18/0x28
pc : [<c002fb10>]    lr : [<c002fb0c>]    psr: 40000093
sp : c3867c68  ip : c3867bd0  fp : c3866000
r10: c3800600  r9 : c3802430  r8 : 00000004
r7 : c3802428  r6 : c3802660  r5 : c3802420  r4 : a0000013
r3 : 00000000  r2 : c3866000  r1 : 00000003  r0 : 00000024
Flags: nZcv  IRQs off  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
Control: 0000717f  Table: 330a8000  DAC: 00000017
Process khubd (pid: 152, stack limit = 0xc3866270)
Stack: (0xc3867c68 to 0xc3868000)
7c60:                   c0093fdc c0094088 000000d0 000000d0 00000000 000080d0
7c80: 00000000 a0000013 c39ebec0 c3800600 000080d0 00000001 c03f13cc 00000006
7ca0: c02b36f0 c0094574 c0043428 0001c9de c39ebec0 c39ebea0 c3000c00 c02a6a84
7cc0: 89705f41 c3000c00 c39ebec0 c39ebea0 c3000c00 bf036f24 c39ebec8 00000006
7ce0: 00000000 c3000c00 c39ebec0 c39ebea0 c3000c00 bf036f24 c39ebec8 00000006
7d00: 00000000 bf003398 c00aa514 c3867d20 0000a1ff c00e1448 c39d9f84 c39aabe8
7d20: c3867d50 c00e1888 c39aabe8 c39ebea0 c39ebec0 bf036ebc c3000c00 bf036f24
7d40: 0000bec8 01000000 00000000 c39ebea0 c39ebec0 bf036ebc c3000c00 bf036f24
7d60: c39ebec8 00000000 00000000 c0223798 c39ebec0 c01daa14 bf036eec c3867da0
7d80: c045a4f8 c01da6e4 c39ebec0 00000000 c01daa14 c39ebec0 c3867da0 c01d9870
7da0: c38331a8 c39fcb94 c005b3b4 c39ebec0 c39ebec0 c39ebef4 00000000 c01da890
7dc0: c39ebec0 c39ebec0 c3000c00 c01d97f4 00000000 c01d8470 c39ebea0 c3000c68
7de0: 00000000 c3000c68 c3218a00 c3abcd20 00000001 c39ebec0 c39ebea0 c3000c00
7e00: 00000000 c3000c68 c3218a00 c3abcd20 00000001 c0221ee8 00000001 00000000
7e20: 00000000 00000000 00001388 00000000 c3000c04 c3000c68 c3bc29c0 00000001
7e40: c3bc29c4 00000001 c03f4af8 00000000 c39fe780 c3000c00 00000001 c045ab04
7e60: c3867eb8 c045a3bc c3000c70 00000000 00000000 c0229238 c3000c68 c0223210
7e80: c3000c00 c045aaf0 c045ab04 c0223230 c3000c68 c01daa14 c045ab04 c01da6e4
7ea0: c3000c68 00000000 c01daa14 c3000c68 c3867eb8 c01d9870 c38331a8 c3862f54
7ec0: c005b3b4 c3000c68 c3000c68 c3000c9c 00000002 c01da890 c3867ef9 c3000c68
7ee0: c3829f60 c01d97f4 00000000 c01d8470 c38918e0 c3aaf468 39383102 c300343a
7f00: 00000001 c0219660 c03f1768 c3000c00 00000000 c3000c68 00000002 c3aaf814
7f20: 00000001 00000101 c38918e0 c021b6e0 00000002 00000000 00000000 c3000c00
7f40: c38917c0 c021c418 00000064 00000064 00000101 c3867f60 c005b920 c3867f94
7f60: c3891830 c3aaf400 c3866000 c3aaf400 c3aaf800 00000000 c38918e0 c3aaf400
7f80: 00000012 00000000 00000000 c3837920 c00574a0 c3867f94 c3867f94 00000101
7fa0: 01010001 c3867fd4 c381bf48 c3867fd4 c381bf48 00000000 c021ba3c 00000000
7fc0: 00000000 00000000 00000000 c00573dc 00000000 00000000 c3867fd8 c3867fd8
7fe0: 00000000 00000000 00000000 00000000 00000000 c002ce88 00000000 ffff0000
[<c002fb10>] (__bug+0x1c/0x28) from [<c0094088>] (cache_alloc_refill+0x13c/0x594)
[<c0094088>] (cache_alloc_refill+0x13c/0x594) from [<c0094574>] (__kmalloc+0x94/0xd0)
[<c0094574>] (__kmalloc+0x94/0xd0) from [<c02a6a84>] (alloc_netdev_mq+0x48/0x1b0)
[<c02a6a84>] (alloc_netdev_mq+0x48/0x1b0) from [<bf003398>] (vntwusb_found1+0x58/0x53c [vt6656_stage])
[<bf003398>] (vntwusb_found1+0x58/0x53c [vt6656_stage]) from [<c0223798>] (usb_probe_interface+0x130/0x180)
[<c0223798>] (usb_probe_interface+0x130/0x180) from [<c01da6e4>] (driver_probe_device+0xac/0x164)
[<c01da6e4>] (driver_probe_device+0xac/0x164) from [<c01d9870>] (bus_for_each_drv+0x50/0x90)
[<c01d9870>] (bus_for_each_drv+0x50/0x90) from [<c01da890>] (device_attach+0x50/0x68)
[<c01da890>] (device_attach+0x50/0x68) from [<c01d97f4>] (bus_probe_device+0x28/0x54)
[<c01d97f4>] (bus_probe_device+0x28/0x54) from [<c01d8470>] (device_add+0x3b4/0x4f0)
[<c01d8470>] (device_add+0x3b4/0x4f0) from [<c0221ee8>] (usb_set_configuration+0x524/0x5b8)
[<c0221ee8>] (usb_set_configuration+0x524/0x5b8) from [<c0229238>] (generic_probe+0x5c/0xa0)
[<c0229238>] (generic_probe+0x5c/0xa0) from [<c0223230>] (usb_probe_device+0x48/0x54)
[<c0223230>] (usb_probe_device+0x48/0x54) from [<c01da6e4>] (driver_probe_device+0xac/0x164)
[<c01da6e4>] (driver_probe_device+0xac/0x164) from [<c01d9870>] (bus_for_each_drv+0x50/0x90)
[<c01d9870>] (bus_for_each_drv+0x50/0x90) from [<c01da890>] (device_attach+0x50/0x68)
[<c01da890>] (device_attach+0x50/0x68) from [<c01d97f4>] (bus_probe_device+0x28/0x54)
[<c01d97f4>] (bus_probe_device+0x28/0x54) from [<c01d8470>] (device_add+0x3b4/0x4f0)
[<c01d8470>] (device_add+0x3b4/0x4f0) from [<c021b6e0>] (usb_new_device+0x100/0x174)
[<c021b6e0>] (usb_new_device+0x100/0x174) from [<c021c418>] (hub_thread+0x9dc/0xeec)
[<c021c418>] (hub_thread+0x9dc/0xeec) from [<c00573dc>] (kthread+0x78/0x80)
[<c00573dc>] (kthread+0x78/0x80) from [<c002ce88>] (kernel_thread_exit+0x0/0x8)
Code: e1a01000 e59f000c eb005014 e3a03000 (e5833000)
---[ end trace 2a51e0dbab9e4fbe ]---
note: khubd[152] exited with preempt_count 1

Signed-off-by: miaofng <miaofng@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>