Re: [patch v2] cx231xx: card->driver "Conexant cx231xx Audio" too

[walter harms <wharms@bfs.de>]

Takashi Iwai schrieb:
> At Mon, 22 Mar 2010 18:18:04 +0100,
> walter harms wrote:
>>
>>
>> Takashi Iwai schrieb:
>>> At Mon, 22 Mar 2010 08:43:47 -0700,
>>> Joe Perches wrote:
>>>> On Mon, 2010-03-22 at 18:39 +0300, Dan Carpenter wrote:
>>>>> card->driver is 15 characters and a NULL, the original code could 
>>>>> cause a buffer overflow.
>>>>> In version 2, I used a better name that Takashi Iwai suggested.
>>>> Perhaps it's better to use strncpy as well.
>>> strlcpy() would be safer :)
>>>
>>> But, in such a case, we want rather that the error is notified at
>>> build time.
>>>
>>> Maybe a macro like below would be helpful to catch such bugs?
>>>
>>> #define COPY_STRING(buf, src)						\
>>> 	do {								\
>>> 		if (__builtin_constant_p(src))				\
>>> 			BUILD_BUG_ON(strlen(src) >= sizeof(buf));	\
>>> 		strcpy(buf, src);					\
>>> 	} while (0)
>>>
>>> and used like:
>>>
>>> struct foo {
>>> 	char foo[5];
>>> } x;
>>>
>>> COPY_STRING(x.foo, "OK"); // OK
>>> COPY_STRING(x.foo, "1234567890"); // NG
>>>
>>>
>>> Takashi
>>> --
>>
>> did i miss something ?
> 
> Yes :)
> 
>> why not change  card->driver int char * ? a simple card->driver="name"
>> would solve the problem.
> 
> The length is fixed because it's used for ioctl.
> 
> 

I am not sure that i understand that, users can change the name ?
ok who do you prevent an overflow there ? (I could not find the code)
Perhaps you will simply cut the user string ? if you do that you can
simply use strncpy here.

thx for fast answer,
ntl i will go offline for the next weeks

re,
 wh