ACPI: uninitialized static variable causes system to fault when loading acpiphp driver

Initialize the static variable sub_driver to NULL. This causes acp_pci_register_driver to take a page fault when this routine is called as part of loading the acpiphp driver. This patch applies to 2.6.30.

acpiphp: ACPI Hot Plug PCI Controller Driver version: 0.5

Unable to handle kernel paging request at ffffffff886cd330 RIP:  [<ffffffff80192d7b>] acpi_pci_register_driver+0x13/0x58
PGD 203067 PUD 205063 PMD 276f9b067 PTE 0
Oops: 0000 [1] SMP
last sysfs file: /block/ram0/dev
CPU 9
Modules linked in: acpiphp ipt_REJECT xt_tcpudp x_tables bridge autofs4 ipmi_devintf ipmi_si ipmi_msghandler hidp rfcomm l2cap bluetooth lockd sunrpc ib_iser rdma_cm ib_cm iw_cm ib_sa ib_mad ib_core ib_addr iscsi_tcp bnx2i cnic ipv6 xfrm_nalgo crypto_api uio cxgb3i cxgb3 libiscsi_tcp libiscsi2 scsi_transport_iscsi2 scsi_transport_iscsi cpufreq_ondemand acpi_cpufreq freq_table dm_mirror dm_multipath scsi_dh video hwmon backlight sbs i2c_ec button battery asus_acpi acpi_memhotplug ac parport_pc lp parport joydev igb shpchp i2c_i801 8021q i2c_core sg pcspkr dm_raid45 dm_message dm_region_hash dm_log dm_mod dm_mem_cache usb_storage mptsas mptscsih scsi_transport_sas mptbase ahci libata sd_mod scsi_mod ext3 jbd uhci_hcd ohci_hcd ehci_hcd
Pid: 15674, comm: modprobe Not tainted 2.6.18-160.el5 #1
RIP: 0010:[<ffffffff80192d7b>]  [<ffffffff80192d7b>] acpi_pci_register_driver+0x13/0x58
RSP: 0018:ffff81037f98bf08  EFLAGS: 00010286
RAX: ffffffff886cd330 RBX: ffffffff8864f380 RCX: ffff81027fbc5c40
RDX: ffffffff886cd330 RSI: 0000000000000001 RDI: ffffffff8864f330
RBP: ffffffff8864f330 R08: 0000000000000000 R09: ffffffffffffffff
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000012c20
R13: 00002b5effbc7010 R14: 00000000191ef388 R15: 00002b5effbc7010
FS:  00002b5effbc6240(0000) GS:ffff810283bca440(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffffffff886cd330 CR3: 000000027ffba000 CR4: 00000000000006e0
Process modprobe (pid: 15674, threadinfo ffff81037f98a000, task ffff81037fb36040)
Stack:  ffffffff8864f380 00000000191ef0e0 0000000000012c20 ffffffff881fd088
ffffffff8864f380 00000000191ef0e0 0000000200012c20 ffffffff881fd027
ffffffff8864f380 ffffffff800a5a04 00002b5effbc7010 0000000000000000
Call Trace:
[<ffffffff881fd088>] :acpiphp:acpiphp_glue_init+0x42/0x49
[<ffffffff881fd027>] :acpiphp:acpiphp_init+0x27/0x46
[<ffffffff800a5a04>] sys_init_module+0xaf/0x1f2
[<ffffffff8005d28d>] tracesys+0xd5/0xe0

@@ -76,7 +76,7 @@ struct acpi_pci_root {
 

static LIST_HEAD(acpi_pci_roots);

-static struct acpi_pci_driver *sub_driver; +static struct acpi_pci_driver *sub_driver = NULL; static DEFINE_MUTEX(osc_lock);

int acpi_pci_register_driver(struct acpi_pci_driver *driver) --