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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Aaron Ma <aaron.ma@canonical.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: [PATCH 4.14 39/70] platform/x86: thinkpad_acpi: re-initialize ACPI buffer size when reuse
Date:   Mon, 12 Oct 2020 15:26:55 +0200
Message-Id: <20201012132632.060315100@linuxfoundation.org>
In-Reply-To: <20201012132630.201442517@linuxfoundation.org>
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From: Aaron Ma <aaron.ma@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.ma@canonical.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@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
@@ -6749,8 +6749,10 @@ 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)) {