acer-wmi: fix obj is NULL but dereferenced

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>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>

1 files changed, 25 insertions, 21 deletions

diff --git a/drivers/platform/x86/acer-wmi.c b/drivers/platform/x86/acer-wmi.c
index 06f4eb7ab87e..ff0a866791ca 100644
--- a/drivers/platform/x86/acer-wmi.c
+++ b/drivers/platform/x86/acer-wmi.c
@@ -875,7 +875,7 @@ 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);
@@ -884,14 +884,14 @@ 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)
@@ -1193,12 +1193,14 @@ 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;
@@ -1946,12 +1948,14 @@ 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);