dell-wmi, hp-wmi, msi-wmi: check wmi_get_event_data() return value

dell-wmi, hp-wmi, msi-wmi: check wmi_get_event_data() return value

commit fda11e61ff8a4e3a8ebbd434e46560b67cc0ca9d upstream

[ backport to 2.6.32 ]

When acpi_evaluate_object() is passed ACPI_ALLOCATE_BUFFER,
the caller must kfree the returned buffer if AE_OK is returned.

The callers of wmi_get_event_data() pass ACPI_ALLOCATE_BUFFER,
and thus must check its return value before accessing
or kfree() on the buffer.

Signed-off-by: Len Brown <len.brown@intel.com>
Cc: Chuck Ebbert <cebbert@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>