From: Aaron Ma <aaron...@canonical.com>

commit 720ef73d1a239e33c3ad8fac356b9b1348e68aaf upstream.

Evaluating ACPI _BCL could fail, then ACPI buffer size will be set to 0.
When reuse this ACPI buffer, AE_BUFFER_OVERFLOW will be triggered.

Re-initialize buffer size will make ACPI evaluate successfully.

Fixes: 46445b6b896fd ("thinkpad-acpi: fix handle locate for video and query of 
_BCL")
Signed-off-by: Aaron Ma <aaron...@canonical.com>
Signed-off-by: Andy Shevchenko <andriy.shevche...@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/platform/x86/thinkpad_acpi.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/platform/x86/thinkpad_acpi.c
+++ b/drivers/platform/x86/thinkpad_acpi.c
@@ -6362,8 +6362,10 @@ static int __init tpacpi_query_bcl_level
        list_for_each_entry(child, &device->children, node) {
                acpi_status status = acpi_evaluate_object(child->handle, "_BCL",
                                                          NULL, &buffer);
-               if (ACPI_FAILURE(status))
+               if (ACPI_FAILURE(status)) {
+                       buffer.length = ACPI_ALLOCATE_BUFFER;
                        continue;
+               }
 
                obj = (union acpi_object *)buffer.pointer;
                if (!obj || (obj->type != ACPI_TYPE_PACKAGE)) {


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