[PATCH 2/3] acer-wmi: fix obj is NULL but dereferenced

["Lee, Chun-Yi" <joeyli.kernel@gmail.com>]

Fengguang Wu run coccinelle and warns about:
  drivers/platform/x86/acer-wmi.c:1200:17-21: ERROR: obj is NULL but dereferenced.
  drivers/platform/x86/acer-wmi.c:891:17-21: ERROR: obj is NULL but dereferenced.
  drivers/platform/x86/acer-wmi.c:1953:17-21: ERROR: obj is NULL but dereferenced.

It causes by the code in patch 987dfbaa65b2c3568b85e29d2598da08a011ee09 doesn't check
obj variable should not be NULL. There have risk for dereference a NULL obj, so add
this patch to fix.

Cc: Carlos Corbacho <carlos@strangeworlds.co.uk>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Dmitry Torokhov <dtor@mail.ru>
Cc: Corentin Chary <corentincj@iksaif.net>
Cc: Thomas Renninger <trenn@suse.de>
Signed-off-by: Lee, Chun-Yi <jlee@suse.com>
---
 drivers/platform/x86/acer-wmi.c |   46 +++++++++++++++++++++-----------------
 1 files changed, 25 insertions(+), 21 deletions(-)

diff --git a/drivers/platform/x86/acer-wmi.c b/drivers/platform/x86/acer-wmi.c
index 00d8c39..5ff493e 100644
--- a/drivers/platform/x86/acer-wmi.c
+++ b/drivers/platform/x86/acer-wmi.c
@@ -884,7 +884,7 @@ WMI_execute_u32(u32 method_id, u32 in, u32 *out)
 	struct acpi_buffer input = { (acpi_size) sizeof(u32), (void *)(&in) };
 	struct acpi_buffer result = { ACPI_ALLOCATE_BUFFER, NULL };
 	union acpi_object *obj;
-	u32 tmp;
+	u32 tmp = 0;
 	acpi_status status;
 
 	status = wmi_evaluate_method(WMID_GUID1, 1, method_id, &input, &result);
@@ -893,14 +893,14 @@ WMI_execute_u32(u32 method_id, u32 in, u32 *out)
 		return status;
 
 	obj = (union acpi_object *) result.pointer;
-	if (obj && obj->type == ACPI_TYPE_BUFFER &&
-		(obj->buffer.length == sizeof(u32) ||
-		obj->buffer.length == sizeof(u64))) {
-		tmp = *((u32 *) obj->buffer.pointer);
-	} else if (obj->type == ACPI_TYPE_INTEGER) {
-		tmp = (u32) obj->integer.value;
-	} else {
-		tmp = 0;
+	if (obj) {
+		if (obj->type == ACPI_TYPE_BUFFER &&
+			(obj->buffer.length == sizeof(u32) ||
+			obj->buffer.length == sizeof(u64))) {
+			tmp = *((u32 *) obj->buffer.pointer);
+		} else if (obj->type == ACPI_TYPE_INTEGER) {
+			tmp = (u32) obj->integer.value;
+		}
 	}
 
 	if (out)
@@ -1202,12 +1202,14 @@ static acpi_status WMID_set_capabilities(void)
 		return status;
 
 	obj = (union acpi_object *) out.pointer;
-	if (obj && obj->type == ACPI_TYPE_BUFFER &&
-		(obj->buffer.length == sizeof(u32) ||
-		obj->buffer.length == sizeof(u64))) {
-		devices = *((u32 *) obj->buffer.pointer);
-	} else if (obj->type == ACPI_TYPE_INTEGER) {
-		devices = (u32) obj->integer.value;
+	if (obj) {
+		if (obj->type == ACPI_TYPE_BUFFER &&
+			(obj->buffer.length == sizeof(u32) ||
+			obj->buffer.length == sizeof(u64))) {
+			devices = *((u32 *) obj->buffer.pointer);
+		} else if (obj->type == ACPI_TYPE_INTEGER) {
+			devices = (u32) obj->integer.value;
+		}
 	} else {
 		kfree(out.pointer);
 		return AE_ERROR;
@@ -1955,12 +1957,14 @@ static u32 get_wmid_devices(void)
 		return 0;
 
 	obj = (union acpi_object *) out.pointer;
-	if (obj && obj->type == ACPI_TYPE_BUFFER &&
-		(obj->buffer.length == sizeof(u32) ||
-		obj->buffer.length == sizeof(u64))) {
-		devices = *((u32 *) obj->buffer.pointer);
-	} else if (obj->type == ACPI_TYPE_INTEGER) {
-		devices = (u32) obj->integer.value;
+	if (obj) {
+		if (obj->type == ACPI_TYPE_BUFFER &&
+			(obj->buffer.length == sizeof(u32) ||
+			obj->buffer.length == sizeof(u64))) {
+			devices = *((u32 *) obj->buffer.pointer);
+		} else if (obj->type == ACPI_TYPE_INTEGER) {
+			devices = (u32) obj->integer.value;
+		}
 	}
 
 	kfree(out.pointer);
-- 
1.6.0.2