ACPI / dock: Take ACPI scan lock in write_undock()

Since commit 3757b94 (ACPI / hotplug: Fix concurrency issues and
memory leaks) acpi_bus_scan() and acpi_bus_trim() must always be
called under acpi_scan_lock, but currently the following scenario
violating that requirement is possible:

 write_undock()
  handle_eject_request()
   hotplug_dock_devices()
    dock_remove_acpi_device()
     acpi_bus_trim()

Fix that by making write_undock() acquire acpi_scan_lock before
calling handle_eject_request() as appropriate (begin_undock() is
under the lock too in analogy with acpi_dock_deferred_cb()).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: 3.9+ <stable@vger.kernel.org>
Acked-by: Toshi Kani <toshi.kani@hp.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/acpi/dock.c b/drivers/acpi/dock.c
index 4fdea381ef21..ec117c6c996c 100644
--- a/drivers/acpi/dock.c
+++ b/drivers/acpi/dock.c
@@ -868,8 +868,10 @@ static ssize_t write_undock(struct device *dev, struct device_attribute *attr,
         if (!count)
                 return -EINVAL;
 
+        acpi_scan_lock_acquire();
         begin_undock(dock_station);
         ret = handle_eject_request(dock_station, ACPI_NOTIFY_EJECT_REQUEST);
+        acpi_scan_lock_release();
         return ret ? ret: count;
 }
 static DEVICE_ATTR(undock, S_IWUSR, NULL, write_undock);