[patch 08/56] eeepc-laptop: fix oops when changing backlight brightness during eeepc-laptop init

Greg KH
2009-02-11T00:30:54Z

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2.6.27-stable review patch. If anyone has any objections, please let us know.
------------------

From: Darren Salt <linux@youmustbejoking.demon.co.uk>

commit 7695fb04aca62e2d8a7ca6ede50f6211e1d71e53 upstream.

I got the following oops while changing the backlight brightness during
startup. When it happens, it prevents use of the hotkeys, Fn-Fx, and the
lid button.

It's a clear use-before-init, as I verified by testing with an
appropriately-placed "else printk".

BUG: unable to handle kernel NULL pointer dereference at 00000000
*pde = 00000000
Oops: 0002 [#1] PREEMPT SMP
Pid: 160, comm: kacpi_notify Not tainted (2.6.28.1-eee901 #4) 901
EIP: 0060:[<c0264e68>] [<c0264e68>] eeepc_hotk_notify+26/da
EFLAGS: 00010246 CPU: 1
Using defaults from ksymoops -t elf32-i386 -a i386
EAX: 00000009 EBX: 00000000 ECX: 00000009 EDX: f70dbf64
ESI: 00000029 EDI: f7335188 EBP: c02112c9 ESP: f70dbf80
DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068
f70731e0 f73acd50 c02164ac f7335180 f70aa040 c02112e6 f733518c c012b62f
f70aa044 f70aa040 c012bdba f70aa04c 00000000 c012be6e 00000000 f70bdf80
c012e198 f70dbfc4 f70dbfc4 f70aa040 c012bdba 00000000 c012e0c9 c012e091
Call Trace:
[<c02164ac>] ? acpi_ev_notify_dispatch+4c/55
[<c02112e6>] ? acpi_os_execute_deferred+1d/25
[<c012b62f>] ? run_workqueue+71/f1
[<c012bdba>] ? worker_thread+0/bf
[<c012be6e>] ? worker_thread+b4/bf
[<c012e198>] ? autoremove_wake_function+0/2b
[<c012bdba>] ? worker_thread+0/bf
[<c012e0c9>] ? kthread+38/5f
[<c012e091>] ? kthread+0/5f
[<c0103abf>] ? kernel_thread_helper+7/10
Code: 00 00 00 00 c3 83 3d 60 5c 50 c0 00 56 89 d6 53 0f 84 c4 00 00 00 8d 42
e0 83 f8 0f 77 0f 8b 1d 68 5c 50 c0 89 d8 e8 a9 fa ff ff <89> 03 8b 1d 60 5c
50 c0 89 f2 83 e2 7f 0f b7 4c 53 10 8d 41 01

Signed-off-by: Darren Salt <linux@youmustbejoking.demon.co.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
drivers/misc/eeepc-laptop.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/misc/eeepc-laptop.c
+++ b/drivers/misc/eeepc-laptop.c
@@ -381,7 +381,8 @@ static void notify_wlan(u32 *event)
static void notify_brn(void)
{
struct backlight_device *bd = eeepc_backlight_device;
- bd->props.brightness = read_brightness(bd);
+ if (bd)
+ bd->props.brightness = read_brightness(bd);
}

static void eeepc_hotk_notify(acpi_handle handle, u32 event, void *data)