linux-kernel - Re: [PATCH] x86/mm/mem_encrypt_identity : fix error useage to sizeof

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Date:   Tue, 15 Jan 2019 11:35:29 +0100
From:   Juergen Gross <jgross@...e.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     peng.hao2@....com.cn, bp@...en8.de, dave.hansen@...ux.intel.com,
        peterz@...radead.org, luto@...nel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/mm/mem_encrypt_identity : fix error useage to sizeof

On 15/01/2019 11:25, Thomas Gleixner wrote:
> On Tue, 15 Jan 2019, Juergen Gross wrote:
>> On 15/01/2019 11:13, Thomas Gleixner wrote:
>>> On Mon, 7 Jan 2019, peng.hao2@....com.cn wrote:
>>>
>>>>>> Fix error usage to sizeof. It should not use sizeof to pointer.
>>>>>
>>>>> .... because?
>>>>>
>>>>> The commit message needs to explain what the potential issue could be
>>>>> and why it doesn't matter in this case.
>>>> I see the definition of pte_t may be more than sizeof(unsigned long).
>>>> So I think sizeof(pte_t) is safer.
>>>
>>> What exactly is the difference between:
>>>
>>> 	pte_t	*p;
>>>
>>> 	sizeof(*p)
>>>
>>> and
>>>
>>> 	sizeof(pte_t)
>>>
>>> and what is safer about the latter?
>>
>> Please note that the current code is using sizeof(p) instead of sizeof(*p).
> 
> Ooops. That's wrong indeed, but we should not change it to sizeof(pte_t)
> and change it to sizeof(*p) instead.

And that's what the patch does.


Juergen