linux-kernel - Re: [PATCH] platform/mellanox: Add a null pointer check in mlxbf_pmc_create

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Date:   Fri, 1 Dec 2023 11:20:48 +0800
From:   Kunwu Chan <chentao@...inos.cn>
To:     Vadim Pasternak <vadimp@...dia.com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        David Thompson <davthompson@...dia.com>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        Shravan Ramani <shravankr@...dia.com>,
        "kunwu.chan@...mail.com" <kunwu.chan@...mail.com>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] platform/mellanox: Add a null pointer check in
 mlxbf_pmc_create_groups

Hi Vadim,
Thanks for your reply.

I will follw your suggestions and add some ‘fixes’ label in v2 patch.

Thanks again,
Kunwu


On 2023/12/1 00:01, Vadim Pasternak wrote:
> Hi Ilpo!
> 
>> -----Original Message-----
>> From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
>> Sent: Thursday, 30 November 2023 17:26
>> To: Kunwu Chan <chentao@...inos.cn>; Vadim Pasternak
>> <vadimp@...dia.com>
>> Cc: Hans de Goede <hdegoede@...hat.com>; jiri@...nulli.us; Shravan
>> Ramani <shravankr@...dia.com>; kunwu.chan@...mail.com; platform-
>> driver-x86@...r.kernel.org; LKML <linux-kernel@...r.kernel.org>
>> Subject: Re: [PATCH] platform/mellanox: Add a null pointer check in
>> mlxbf_pmc_create_groups
>>
>> Hi Vadim,
>>
>> Could you please take a look at this and give advice to Kunwu so we can get all
>> of them squashed in one go.
> 
> It seems there are six calls devm_kasprintf(), which requires checking pointer.
> 
> I guess, it is correct to return '-ENOMEM' for any failure.
> 
> I see there is another problem in mlxbf_pmc_probe() - it lacks error flow for:
> 	pmc->hwmon_dev = devm_hwmon_device_register_with_groups(
> 		dev, "bfperf", pmc, pmc->groups);
> 	
> Need to add:
> 	if (IS_ERR(pmc->hwmon_dev))
> 		return PTR_ERR(pmc->hwmon_dev);
> 
> Sharvan, David,
> Could you, please, have look?
> 
>>
>> On Thu, 30 Nov 2023, Kunwu Chan wrote:
>>
>>> Thanks for your reply.
>>>
>>> Cause i don't know how to deal with in some scenario，such as in
>>> 'mlxbf_pmc_init_perftype_counter', when 'attr->dev_attr.attr.name' is
>>> null, should return '-ENOMEM' or 'continue' the loop?
>>
>> I'd have thought returning -ENOMEM would be safe because it just ends up
>> failing probe()? ...And it's not that likely to occur in the first place.
>>
>> --
>>   i.
>>
>>>
>>> So I'm going to solve it one by one.
>>>
>>> Thanks again,
>>> Kunwu
>>>
>>> On 2023/11/28 17:51, Ilpo Järvinen wrote:
>>>> On Mon, 27 Nov 2023, Kunwu Chan wrote:
>>>>
>>>>> devm_kasprintf() returns a pointer to dynamically allocated memory
>>>>> which can be NULL upon failure.
>>>>>
>>>>> Fixes: 1a218d312e65 ("platform/mellanox: mlxbf-pmc: Add Mellanox
>>>>> BlueField PMC driver")
>>>>> Signed-off-by: Kunwu Chan <chentao@...inos.cn>
>>>>> ---
>>>>>    drivers/platform/mellanox/mlxbf-pmc.c | 2 ++
>>>>>    1 file changed, 2 insertions(+)
>>>>>
>>>>> diff --git a/drivers/platform/mellanox/mlxbf-pmc.c
>>>>> b/drivers/platform/mellanox/mlxbf-pmc.c
>>>>> index 0b427fc24a96..59bbe5e13f6b 100644
>>>>> --- a/drivers/platform/mellanox/mlxbf-pmc.c
>>>>> +++ b/drivers/platform/mellanox/mlxbf-pmc.c
>>>>> @@ -1882,6 +1882,8 @@ static int mlxbf_pmc_create_groups(struct
>>>>> device *dev, int blk_num)
>>>>>    	pmc->block[blk_num].block_attr_grp.attrs =
>>>>> pmc->block[blk_num].block_attr;
>>>>>    	pmc->block[blk_num].block_attr_grp.name = devm_kasprintf(
>>>>>    		dev, GFP_KERNEL, pmc->block_name[blk_num]);
>>>>> +	if (!pmc->block[blk_num].block_attr_grp.name)
>>>>> +		return -ENOMEM;
>>>>>    	pmc->groups[pmc->group_num] = &pmc-
>>> block[blk_num].block_attr_grp;
>>>>>    	pmc->group_num++;
>>>>
>>>> I'm totally lost, why did you fix only one devm_kasprintf() location?
>>>> Don't all of them need this check?
>>>>
>>>