Re: [PATCH] staging: greybus: fix possible null-ptr-deref in gb_audio_manager_get_module()

[Alex Elder <elder@ieee.org>]

On 10/28/24 9:58 PM, yiyang (D) wrote:
> 
> On 2024/10/28 20:46, Alex Elder wrote:
>> On 10/26/24 5:50 AM, Dan Carpenter wrote:
>>> On Sat, Oct 26, 2024 at 08:11:53AM +0000, Yi Yang wrote:
>>>> The gb_audio_manager_get_module() is EXPORT_SYMBOL, and will return 
>>>> NULL
>>>> when incoming parameter id < 0, fix possible null-ptr-deref by add 
>>>> check
>>>> for return value.
>>>>
>>>> Fixes: 8db00736d365 ("greybus: audio: Add Audio Manager")
>>>> Signed-off-by: Yi Yang <yiyang13@huawei.com>
>>>
>>> Where is gb_audio_manager_get_module() called from?  So far as I can 
>>> see it's
>>> never used.  Why not just delete it?
>>>
>>> regards,
>>> dan carpenter
>>
>> I agree with this.  I suspected all callers might have guaranteed
>> that the "id" value passed would be always valid, but... there are
>> no callers.
>>
>> It is a simple function, and could be added back again if it is
>> needed in the future (possibly even by reverting the commit that
>> removes it).
>>
>> If you do this, please remove gb_audio_put_module() in the same
>> patch.  It too has no callers.
>>
>> Thank you.
>>
>>                      -Alex
>>
>> .
> 
> I tried to find the caller before I modified it, but unfortunately I 
> didn't find the caller, so I suspect some non-kernel driver code will 
> try to call this functions.
> 
> I just found this problem while reading the code and I'm not sure if I 
> should remove the function.

The Linux kernel is a unified whole.  This means that if you have the
current version of the kernel source code, it will incorporate *all*
possible callers of a given function (or more generally, references to
or users of a given symbol).  The only possible exception might be
out-of-tree code, but that is not our concern.

If you can't find any callers, none exist.  It's fine to propose
removing the function.  And if the maintainer accepts it, it's a
good change.

					-Alex

> 
> regards,
> Yiyang