nfit: Fix nfit_intel_shutdown_status() command submission

The implementation is broken in all the ways the unit test did not touch:

1/ The local definition of in_buf and in_obj violated C99 initializer
   expectations for zeroing. By only initializing 2 out of the three
   struct members the compiler was free to zero-initialize the remaining
   entry even though the aliased location in the union was initialized.

2/ The implementation made assumptions about the state of the 'smart'
   payload after command execution that are satisfied by
   acpi_nfit_ctl(), but not acpi_evaluate_dsm().

3/ populate_shutdown_status() is skipped on Intel NVDIMMs due to the early
   return for skipping the common _LS{I,R,W} enabling.

4/ The input length should be zero.

This breakage was missed due to the unit test implementation only
testing the case where nfit_intel_shutdown_status() returns a valid
payload.

Much of this complexity would be saved if acpi_nfit_ctl() could be used, but
that currently requires a 'struct nvdimm *' argument and one is not created
until later in the init process. The health result is needed before the device
is created because the payload gates whether the nmemX/nfit/dirty_shutdown
property is visible in sysfs.

Cc: <stable@vger.kernel.org>
Fixes: 0ead1118 ("acpi, nfit: Collect shutdown status")
Reported-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/acpi/nfit/core.c

@@ -1738,14 +1738,14 @@ static bool acpi_nvdimm_has_method(struct acpi_device *adev, char *method)
 
 __weak void nfit_intel_shutdown_status(struct nfit_mem *nfit_mem)
 {
+	struct device *dev = &nfit_mem->adev->dev;
 	struct nd_intel_smart smart = { 0 };
 	union acpi_object in_buf = {
-		.type = ACPI_TYPE_BUFFER,
-		.buffer.pointer = (char *) &smart,
-		.buffer.length = sizeof(smart),
+		.buffer.type = ACPI_TYPE_BUFFER,
+		.buffer.length = 0,
 	};
 	union acpi_object in_obj = {
-		.type = ACPI_TYPE_PACKAGE,
+		.package.type = ACPI_TYPE_PACKAGE,
 		.package.count = 1,
 		.package.elements = &in_buf,
 	};
@@ -1760,8 +1760,15 @@ __weak void nfit_intel_shutdown_status(struct nfit_mem *nfit_mem)
 		return;
 
 	out_obj = acpi_evaluate_dsm(handle, guid, revid, func, &in_obj);
-	if (!out_obj)
+	if (!out_obj || out_obj->type != ACPI_TYPE_BUFFER
+			|| out_obj->buffer.length < sizeof(smart)) {
+		dev_dbg(dev->parent, "%s: failed to retrieve initial health\n",
+				dev_name(dev));
+		ACPI_FREE(out_obj);
 		return;
+	}
+	memcpy(&smart, out_obj->buffer.pointer, sizeof(smart));
+	ACPI_FREE(out_obj);
 
 	if (smart.flags & ND_INTEL_SMART_SHUTDOWN_VALID) {
 		if (smart.shutdown_state)
@@ -1772,7 +1779,6 @@ __weak void nfit_intel_shutdown_status(struct nfit_mem *nfit_mem)
 		set_bit(NFIT_MEM_DIRTY_COUNT, &nfit_mem->flags);
 		nfit_mem->dirty_shutdown = smart.shutdown_count;
 	}
-	ACPI_FREE(out_obj);
 }
 
 static void populate_shutdown_status(struct nfit_mem *nfit_mem)
@@ -1887,8 +1893,8 @@ static int acpi_nfit_add_dimm(struct acpi_nfit_desc *acpi_desc,
 		| 1 << ND_CMD_SET_CONFIG_DATA;
 	if (family == NVDIMM_FAMILY_INTEL
 			&& (dsm_mask & label_mask) == label_mask)
-		return 0;
-
+		/* skip _LS{I,R,W} enabling */;
+	else {
 		if (acpi_nvdimm_has_method(adev_dimm, "_LSI")
 				&& acpi_nvdimm_has_method(adev_dimm, "_LSR")) {
 			dev_dbg(dev, "%s: has _LSR\n", dev_name(&adev_dimm->dev));
@@ -1900,6 +1906,7 @@ static int acpi_nfit_add_dimm(struct acpi_nfit_desc *acpi_desc,
 			dev_dbg(dev, "%s: has _LSW\n", dev_name(&adev_dimm->dev));
 			set_bit(NFIT_MEM_LSW, &nfit_mem->flags);
 		}
+	}
 
 	populate_shutdown_status(nfit_mem);