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>

diff --git a/drivers/platform/x86/acer-wmi.c b/drivers/platform/x86/acer-wmi.c
index 06f4eb7..ff0a866 100644 (file)
--- 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);