From 8fcfb99c8e29c73dd8945b6105ef54ca4eeb171e Mon Sep 17 00:00:00 2001
From: Toshi Kani <toshi.kani@hp.com>
Date: Tue, 4 Feb 2014 17:48:28 -0700
Subject: [PATCH] ACPI / hotplug: Fix panic on eject to ejected device

When an eject request is sent to an ejected ACPI device, the following
panic occurs:

 ACPI: \_SB_.SCK3.CPU3: ACPI_NOTIFY_EJECT_REQUEST event
 BUG: unable to handle kernel NULL pointer dereference at 0000000000000070
 IP: [<ffffffff813a7cfe>] acpi_device_hotplug+0x10b/0x33b
	:
 Call Trace:
 [<ffffffff813a24da>] acpi_hotplug_work_fn+0x1c/0x27
 [<ffffffff8109cbe5>] process_one_work+0x175/0x430
 [<ffffffff8109d7db>] worker_thread+0x11b/0x3a0

This is becase device->handler is NULL in acpi_device_hotplug().
This case was used to fail in acpi_hotplug_notify_cb() as the target
had no acpi_deivce.  However, acpi_device now exists after ejection.

Added a check to verify if acpi_device->handler is valid for an
eject request in acpi_hotplug_notify_cb().  Note that handler passed
from an argument is still valid while acpi_device->handler is NULL.

Fixes: 202317a573b2 (ACPI / scan: Add acpi_device objects for all device nodes in the namespace)
Signed-off-by: Toshi Kani <toshi.kani@hp.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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