Date: Thu, 24 Mar 2005 21:37:44 +0100
From: Adrian Bunk <bunk@stusta.de>
To: len.brown@intel.com
Cc: acpi-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org
Subject: drivers/acpi/video.c: null pointer dereference
Message-ID: <20050324203744.GB3966@stusta.de>
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The Coverity checker found the following null pointer dereference in 
drivers/acpi/video.c:

<--  snip  -->

...
static int
acpi_video_switch_output(
...
{
...
        struct acpi_video_device *dev=NULL;
...
        list_for_each_safe(node, next, &video->video_device_list) {
                struct acpi_video_device * dev = container_of(node, struct acpi_video_device, entry);
...
        }
...
        switch (event) {
        case ACPI_VIDEO_NOTIFY_CYCLE:
        case ACPI_VIDEO_NOTIFY_NEXT_OUTPUT:
                acpi_video_device_set_state(dev, 0);
                acpi_video_device_set_state(dev_next, 0x80000001);
                break;
        case ACPI_VIDEO_NOTIFY_PREV_OUTPUT:
                acpi_video_device_set_state(dev, 0);
                acpi_video_device_set_state(dev_prev, 0x80000001);
...

<--  snip  -->


Two different variables of the same name within 40 lines of code are a 
good indication that something's wrong...


The outer "dev" variable is never assigned any value different from 
NULL.

acpi_video_device_set_state dereferences this variable.


cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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