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 <[email protected]>
Cc: Matthew Garrett <[email protected]>
Cc: Dmitry Torokhov <[email protected]>
Cc: Corentin Chary <[email protected]>
Cc: Thomas Renninger <[email protected]>
Signed-off-by: Lee, Chun-Yi <[email protected]>
---
 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 07d5f96..11fe00b 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

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