linux-kernel - Re: [PATCH v4 1/2] clk: hisilicon: Use correct return value about hisi_reset

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Date:   Fri, 29 May 2020 14:44:20 +0800
From:   Tiezhu Yang <yangtiezhu@...ngson.cn>
To:     Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>
Cc:     linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>
Subject: Re: [PATCH v4 1/2] clk: hisilicon: Use correct return value about
 hisi_reset_init()

On 05/29/2020 12:31 PM, Stephen Boyd wrote:
> Quoting Tiezhu Yang (2020-05-28 21:02:05)
>> On 05/29/2020 11:58 AM, Stephen Boyd wrote:
>>> Quoting Tiezhu Yang (2020-05-28 19:03:54)
>>>> On 05/29/2020 07:15 AM, Stephen Boyd wrote:
>>>>> Quoting Tiezhu Yang (2020-05-27 19:27:42)
>>>>>> On 05/28/2020 03:06 AM, Stephen Boyd wrote:
>>>>>>> Quoting Tiezhu Yang (2020-05-27 07:39:21)
>>>>>>>> The return value about hisi_reset_init() is not correct, fix it.
>>>>>>>>
>>>>>>>> Fixes: e9a2310fb689 ("reset: hisilicon: fix potential NULL pointer dereference")
>>>>>>> hisi_reset_init() returns NULL on error in that commit. This patch
>>>>>>> doesn't make sense.
>>>>>> Hi Stephen,
>>>>>>
>>>>>> The initial aim of this patch is to use correct return value about
>>>>>> hisi_reset_init(), maybe NULL is OK, but the return value in this
>>>>>> patch is more accurate.
>>>>> The implementation of hisi_reset_init() that I see is this:
>>>>>
>>>>>
>>>>>         struct hisi_reset_controller *rstc;
>>>>>
>>>>>         rstc = devm_kmalloc(&pdev->dev, sizeof(*rstc), GFP_KERNEL);
>>>>>         if (!rstc)
>>>>>                 return NULL;
>>>>>
>>>>>         rstc->membase = devm_platform_ioremap_resource(pdev, 0);
>>>>>         if (IS_ERR(rstc->membase))
>>>>>                 return NULL;
>>>>>
>>>>>         spin_lock_init(&rstc->lock);
>>>>>         rstc->rcdev.owner = THIS_MODULE;
>>>>>         rstc->rcdev.ops = &hisi_reset_ops;
>>>>>         rstc->rcdev.of_node = pdev->dev.of_node;
>>>>>         rstc->rcdev.of_reset_n_cells = 2;
>>>>>         rstc->rcdev.of_xlate = hisi_reset_of_xlate;
>>>>>         reset_controller_register(&rstc->rcdev);
>>>>>
>>>>>         return rstc;
>>>>>
>>>>> And that returns NULL on an error and a valid pointer on success.
>>>>> Changing the code to check the return value of hisi_reset_init() for an
>>>>> error pointer is simply wrong without updating hisi_reset_init() to
>>>>> return an error pointer on error. Where is the patch that changes
>>>>> hisi_reset_init() to return an error pointer?
>>>> Hi Stephen,
>>>>
>>>> Do you mean the following changes?
>>> Yes where is this change?
>> ERR_PTR(-ENOMEM) and ERR_CAST(rstc->membase)
>>
> I think you didn't understand my question. I'm asking where is this
> patch applied to the kernel and what commit is it? I don't see it in the
> clk tree.

Sorry for that, actually I do not quite understand what you mean.

In my opinion, after the following commit,  when devm_ioremap_resource()
is called in hisi_reset_init(), hisi_reset_init() still returns NULL and 
it only returns
-ENOMEM when call hisi_reset_init() failed, I think it may returns 
-EINVAL, -EBUSY
or -ENOMEM if failed, this is what I want to fix.

"reset: hisilicon: fix potential NULL pointer dereference"
https://git.kernel.org/pub/scm/linux/kernel/git/clk/linux.git/commit/drivers/clk/hisilicon/reset.c?h=clk-next&id=e9a2310fb689151166df7fd9971093362d34bd79