[4/4] video: Remove stack VLA usage

Commit Message

Tycho Andersen March 9, 2018, 6:11 a.m. UTC

On Thu, Mar 08, 2018 at 10:01:07PM -0800, Joe Perches wrote:
> On Fri, 2018-03-09 at 16:50 +1100, Tobin C. Harding wrote:
> > The kernel would like to have all stack VLA usage removed[1].  The
> > arrays are fixed here (declared with a const variable) but they appear
> > like VLAs to the compiler.  We can use a pre-processor define to fix the
> > warning.  
> []
> > diff --git a/drivers/video/fbdev/via/via_aux_sii164.c b/drivers/video/fbdev/via/via_aux_sii164.c
> []
> > @@ -27,6 +27,9 @@
> >  
> >  static const char *name = "SiI 164 PanelLink Transmitter";
> >  
> > +/* check vendor id and device id */
> > +const u8 id[] = {0x01, 0x00, 0x06, 0x00};
> 
> It seems id is now global in multiple places.
> Perhaps these should be static.

Does it even need to be global? Why not just get rid of the indirection and use
ARRAY_SIZE where we mean it? This seems to work for me,


Cheers,

Tycho

Comments

Gustavo A. R. Silva March 9, 2018, 6:16 a.m. UTC | #1

I sent a patch for this six hours ago:

https://patchwork.kernel.org/patch/10268591/

--
Gustavo

On 03/09/2018 12:11 AM, Tycho Andersen wrote:
> On Thu, Mar 08, 2018 at 10:01:07PM -0800, Joe Perches wrote:
>> On Fri, 2018-03-09 at 16:50 +1100, Tobin C. Harding wrote:
>>> The kernel would like to have all stack VLA usage removed[1].  The
>>> arrays are fixed here (declared with a const variable) but they appear
>>> like VLAs to the compiler.  We can use a pre-processor define to fix the
>>> warning.
>> []
>>> diff --git a/drivers/video/fbdev/via/via_aux_sii164.c b/drivers/video/fbdev/via/via_aux_sii164.c
>> []
>>> @@ -27,6 +27,9 @@
>>>   
>>>   static const char *name = "SiI 164 PanelLink Transmitter";
>>>   
>>> +/* check vendor id and device id */
>>> +const u8 id[] = {0x01, 0x00, 0x06, 0x00};
>>
>> It seems id is now global in multiple places.
>> Perhaps these should be static.
> 
> Does it even need to be global? Why not just get rid of the indirection and use
> ARRAY_SIZE where we mean it? This seems to work for me,
> 
> diff --git a/drivers/video/fbdev/via/via_aux_sii164.c b/drivers/video/fbdev/via/via_aux_sii164.c
> index ca1b35f033b1..87db6c98d680 100644
> --- a/drivers/video/fbdev/via/via_aux_sii164.c
> +++ b/drivers/video/fbdev/via/via_aux_sii164.c
> @@ -35,10 +35,10 @@ static void probe(struct via_aux_bus *bus, u8 addr)
>                  .addr   =       addr,
>                  .name   =       name};
>          /* check vendor id and device id */
> -       const u8 id[] = {0x01, 0x00, 0x06, 0x00}, len = ARRAY_SIZE(id);
> -       u8 tmp[len];
> +       const u8 id[] = {0x01, 0x00, 0x06, 0x00};
> +       u8 tmp[ARRAY_SIZE(id)];
>   
> -       if (!via_aux_read(&drv, 0x00, tmp, len) || memcmp(id, tmp, len))
> +       if (!via_aux_read(&drv, 0x00, tmp, sizeof(tmp)) || memcmp(id, tmp, sizeof(tmp)))
>                  return;
>   
>          printk(KERN_INFO "viafb: Found %s at address 0x%x\n", name, addr);
> 
> Cheers,
> 
> Tycho
>

Tobin Harding March 9, 2018, 6:28 a.m. UTC | #2

On Fri, Mar 09, 2018 at 12:16:21AM -0600, Gustavo A. R. Silva wrote:
> 
> I sent a patch for this six hours ago:
> 
> https://patchwork.kernel.org/patch/10268591/
> 
> --
> Gustavo

lol, I knew there would be a race on to fix these :)  And you got it
right, bonus points. Let's drop this one then.


thanks,
Tobin.

Patch

diff --git a/drivers/video/fbdev/via/via_aux_sii164.c b/drivers/video/fbdev/via/via_aux_sii164.c
index ca1b35f033b1..87db6c98d680 100644
--- a/drivers/video/fbdev/via/via_aux_sii164.c
+++ b/drivers/video/fbdev/via/via_aux_sii164.c
@@ -35,10 +35,10 @@  static void probe(struct via_aux_bus *bus, u8 addr)
                .addr   =       addr,
                .name   =       name};
        /* check vendor id and device id */
-       const u8 id[] = {0x01, 0x00, 0x06, 0x00}, len = ARRAY_SIZE(id);
-       u8 tmp[len];
+       const u8 id[] = {0x01, 0x00, 0x06, 0x00};
+       u8 tmp[ARRAY_SIZE(id)];
 
-       if (!via_aux_read(&drv, 0x00, tmp, len) || memcmp(id, tmp, len))
+       if (!via_aux_read(&drv, 0x00, tmp, sizeof(tmp)) || memcmp(id, tmp, sizeof(tmp)))
                return;
 
        printk(KERN_INFO "viafb: Found %s at address 0x%x\n", name, addr);