Re: [PATCH 06/10] Input: sparcspkr - use cleanup facility for device_node

[Javier Carrasco]

On 10/10/2024 23:43, Al Viro wrote:
> On Thu, Oct 10, 2024 at 11:25:56PM +0200, Javier Carrasco wrote:
>>
>> diff --git a/drivers/input/misc/sparcspkr.c b/drivers/input/misc/sparcspkr.c
>> index 20020cbc0752..bb1c732c8f95 100644
>> --- a/drivers/input/misc/sparcspkr.c
>> +++ b/drivers/input/misc/sparcspkr.c
>> @@ -188,7 +188,6 @@ static int bbc_beep_probe(struct platform_device *op)
>>  {
>>  	struct sparcspkr_state *state;
>>  	struct bbc_beep_info *info;
>> -	struct device_node *dp;
>>  	int err = -ENOMEM;
>>  
>>  	state = kzalloc(sizeof(*state), GFP_KERNEL);
>> @@ -199,14 +198,13 @@ static int bbc_beep_probe(struct platform_device *op)
>>  	state->event = bbc_spkr_event;
>>  	spin_lock_init(&state->lock);
>>  
>> -	dp = of_find_node_by_path("/");
>>  	err = -ENODEV;
>> +	struct device_node *dp __free(device_node) = of_find_node_by_path("/");
>>  	if (!dp)
>>  		goto out_free;
> 
> Sigh...  See that
>         state = kzalloc(sizeof(*state), GFP_KERNEL);
> 	if (!state)
> 		goto out_err;
> above?
> 
> IOW, this will quietly generate broken code if built with gcc (and refuse to
> compile with clang).  Yeah, this one is trivially fixed (return -ENOMEM instead
> of a goto), but...
> 
> __cleanup() can be useful, but it's really *not* safe for blind use; you
> need to watch out for changed scopes (harmless in case of device_node)
> and for gotos (broken here).

Hi Al Viro,

sorry, but I think I don't get you. First, I don't see sparc64 as a
supported architecture for clang in the Linux documentation. Maybe the
documentation is not up-to-date, but I tried to compile with clang and
it seems to be true that it is not supported. Anyway, that is not the
issue here.

Second, I might be missing something about the scopes you are
mentioning. 'state' gets allocated before the device_node is declared,
and when the device_node is declared and its initialization fails, it
should jump to 'out_free' to free 'state', shouldn't it? Sorry if I have
overlooked something here.

Thank your for your feedback and best regards,
Javier Carrasco