[PATCH v1 1/2] ACPI: bus: Adjust error handling in acpi_run_osc()

["Rafael J. Wysocki" <rafael@kernel.org>]

From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Some platform firmware incorrectly sets the OSC_CAPABILITIES_MASK_ERROR
bit in its _OSC return buffer even if no support bits have been actually
masked, which causes acpi_run_osc() to return an error when executed
with OSC_QUERY_ENABLE clear in the OC capabilities buffer.  As a result,
the OS assumes that the _OSC evaluation has failed and the platform has
not acknowledged any capabilities, while the platform assumes that it
actually has acknowledged some of them.  This confusion may lead to
missing functionality (and possibly other issues) down the road.

To address this problem, adjust acpi_run_osc() to avoid returning an
error when OSC_CAPABILITIES_MASK_ERROR is set in the return buffer
and OSC_QUERY_ENABLE is clear in the OC capabilities, but all of the
bits in the support mask supplied by the OS are also set in the bit
mask returned by the platform firmware.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 drivers/acpi/bus.c |   23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -240,9 +240,13 @@ acpi_status acpi_run_osc(acpi_handle han
 		status = AE_TYPE;
 		goto out_kfree;
 	}
+	if (out_obj->buffer.length <= OSC_SUPPORT_DWORD) {
+		status = AE_BAD_DATA;
+		goto out_kfree;
+	}
 	/* Need to ignore the bit0 in result code */
 	errors = *((u32 *)out_obj->buffer.pointer) & ~(1 << 0);
-	if (errors) {
+	if (errors & ~OSC_CAPABILITIES_MASK_ERROR) {
 		if (errors & OSC_REQUEST_ERROR)
 			acpi_print_osc_error(handle, context,
 				"_OSC request failed");
@@ -252,17 +256,20 @@ acpi_status acpi_run_osc(acpi_handle han
 		if (errors & OSC_INVALID_REVISION_ERROR)
 			acpi_print_osc_error(handle, context,
 				"_OSC invalid revision");
-		if (errors & OSC_CAPABILITIES_MASK_ERROR) {
-			if (((u32 *)context->cap.pointer)[OSC_QUERY_DWORD]
-			    & OSC_QUERY_ENABLE)
-				goto out_success;
+		status = AE_ERROR;
+		goto out_kfree;
+	}
+	if (errors) {
+		u32 retbuf = ((u32 *)out_obj->buffer.pointer)[OSC_SUPPORT_DWORD];
+		u32 capbuf = ((u32 *)context->cap.pointer)[OSC_SUPPORT_DWORD];
+		u32 querybuf = ((u32 *)context->cap.pointer)[OSC_QUERY_DWORD];
+
+		/* OSC_CAPABILITIES_MASK_ERROR is set in errors. */
+		if (!(querybuf & OSC_QUERY_ENABLE) && (capbuf & retbuf) != capbuf) {
 			status = AE_SUPPORT;
 			goto out_kfree;
 		}
-		status = AE_ERROR;
-		goto out_kfree;
 	}
-out_success:
 	context->ret.length = out_obj->buffer.length;
 	context->ret.pointer = kmemdup(out_obj->buffer.pointer,
 				       context->ret.length, GFP_KERNEL);