Re: [Intel-wired-lan] [PATCH v3] net: ethernet: fix uninitialized pointers with free attribute

[Alexander Lobakin <aleksander.lobakin@intel.com>]

From: Dan Carpenter <dan.carpenter@linaro.org>
Date: Mon, 17 Nov 2025 16:11:32 +0300

> On Thu, Nov 06, 2025 at 03:07:26PM +0100, Alexander Lobakin wrote:
>>> diff --git a/drivers/net/ethernet/intel/ice/ice_flow.c b/drivers/net/ethernet/intel/ice/ice_flow.c
>>> index 6d5c939dc8a515c252cd2b77d155b69fa264ee92..3590dacf3ee57879b3809d715e40bb290e40c4aa 100644
>>> --- a/drivers/net/ethernet/intel/ice/ice_flow.c
>>> +++ b/drivers/net/ethernet/intel/ice/ice_flow.c
>>> @@ -1573,12 +1573,13 @@ ice_flow_set_parser_prof(struct ice_hw *hw, u16 dest_vsi, u16 fdir_vsi,
>>>  			 struct ice_parser_profile *prof, enum ice_block blk)
>>>  {
>>>  	u64 id = find_first_bit(prof->ptypes, ICE_FLOW_PTYPE_MAX);
>>> -	struct ice_flow_prof_params *params __free(kfree);
>>>  	u8 fv_words = hw->blk[blk].es.fvw;
>>>  	int status;
>>>  	int i, idx;
>>>  
>>> -	params = kzalloc(sizeof(*params), GFP_KERNEL);
>>> +	struct ice_flow_prof_params *params __free(kfree) =
>>> +		kzalloc(sizeof(*params), GFP_KERNEL);
>>
>> Please don't do it that way. It's not C++ with RAII and
>> declare-where-you-use.
>> Just leave the variable declarations where they are, but initialize them
>> with `= NULL`.
>>
>> Variable declarations must be in one block and sorted from the longest
>> to the shortest.
>>
> 
> These days, with __free the trend is to say yes this is RAII and we
> should declare it where you use it.  I personally don't have a strong

Sorta, but we can't "declare it where you use it" since we don't allow
declaration-after-statement in the kernel.

> opinion on this either way, but other maintainers do and will NAK the
> `= NULL` approach.
> 
> The documentation says you should do it that way and avoid the `= NULL`
> as well.  The issue is with lock ordering.  It's a FILO ordering, so if
> we require a specific unlock order then declaring variables at the top
> could mess things up.
> 
> The counter argument is that if you declare a variable after a goto
> then that's undefined behavior as well.  Clang will detect that bug so
> it be detected before it hits actual users.
> 
> regards,
> dan carpenter

Thanks,
Olek