Re: [RFC PATCH -next V2 2/7] arm64: fix page_address return value in copy_highpage

From: Tong Tiangen <tongtiangen@huawei.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Alexander Viro <viro@zeniv.linux.org.uk>, <x86@kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	<linux-arm-kernel@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>,
	Vincenzo Frascino <vincenzo.frascino@arm.com>,
	<james.morse@arm.com>
Subject: Re: [RFC PATCH -next V2 2/7] arm64: fix page_address return value in copy_highpage
Date: Wed, 6 Apr 2022 20:47:12 +0800	[thread overview]
Message-ID: <e269a621-ed0e-c74c-9cf6-f81c44c1fbcd@huawei.com> (raw)
In-Reply-To: <Yk1pz7IYwEyGDVNV@FVFF77S0Q05N>

在 2022/4/6 18:22, Mark Rutland 写道:
> On Wed, Apr 06, 2022 at 09:13:06AM +0000, Tong Tiangen wrote:
>> Function page_address return void, fix it.
>>
>> Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
> 
> This looks like a sensible cleanup, but the commit title and message aren't
> that clear.
> 
> Can you please make this:
> 
> | arm64: fix types in copy_highpage()
> |
> | In copy_highpage() the `kto` and `kfrom` local variables are pointers to
> | struct page, but these are used to hold arbitrary pointers to kernel memory.
> | Each call to page_address() returns a void pointer to memory associated with
> | the relevant page, and copy_page() expects void pointers to this memory.
> |
> | This inconsistency was introduced in commit:
> |
> |   2563776b41c31908 ("arm64: mte: Tags-aware copy_{user_,}highpage() implementations")
> |
> | ... and while this doesn't appear to be harmful in practice it is clearly wrong.
> |
> | Correct this by making `kto` and `kfrom` void pointers.
> |
> | Fixes: 2563776b41c31908 ("arm64: mte: Tags-aware copy_{user_,}highpage() implementations")
> 
> With that:
> 
> Acked-by: Mark Rutland <mark.rutland@arm.com>
> 
> Thanks,
> Mark.
> 

OK, sure , will do in next version.

Thanks.
Tong.

>> ---
>>   arch/arm64/mm/copypage.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c
>> index b5447e53cd73..0dea80bf6de4 100644
>> --- a/arch/arm64/mm/copypage.c
>> +++ b/arch/arm64/mm/copypage.c
>> @@ -16,8 +16,8 @@
>>   
>>   void copy_highpage(struct page *to, struct page *from)
>>   {
>> -	struct page *kto = page_address(to);
>> -	struct page *kfrom = page_address(from);
>> +	void *kto = page_address(to);
>> +	void *kfrom = page_address(from);
>>   
>>   	copy_page(kto, kfrom);
>>   
>> -- 
>> 2.18.0.huawei.25
>>
>>
>> _______________________________________________
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> .