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    Subject[PATCH] ACPI hotplug: Fix panic on eject to ejected device
    Date
    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.

    Signed-off-by: Toshi Kani <toshi.kani@hp.com>
    ---
    drivers/acpi/scan.c | 5 +++--
    1 file changed, 3 insertions(+), 2 deletions(-)

    diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
    index 7384158..5cf6adf 100644
    --- a/drivers/acpi/scan.c
    +++ b/drivers/acpi/scan.c
    @@ -484,7 +484,6 @@ static void acpi_device_hotplug(void *data, u32 src)
    static void acpi_hotplug_notify_cb(acpi_handle handle, u32 type, void *data)
    {
    u32 ost_code = ACPI_OST_SC_NON_SPECIFIC_FAILURE;
    - struct acpi_scan_handler *handler = data;
    struct acpi_device *adev;
    acpi_status status;

    @@ -500,7 +499,9 @@ static void acpi_hotplug_notify_cb(acpi_handle handle, u32 type, void *data)
    break;
    case ACPI_NOTIFY_EJECT_REQUEST:
    acpi_handle_debug(handle, "ACPI_NOTIFY_EJECT_REQUEST event\n");
    - if (!handler->hotplug.enabled) {
    + if (!adev->handler)
    + goto err_out;
    + if (!adev->handler->hotplug.enabled) {
    acpi_handle_err(handle, "Eject disabled\n");
    ost_code = ACPI_OST_SC_EJECT_NOT_SUPPORTED;
    goto err_out;

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