linux-kernel - Re: [x86] copy_from{to}

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Message-Id: <6ABF6137-251E-47EF-B824-AC77C9C9AB24@gmail.com>
Date:	Mon, 17 Aug 2015 11:27:01 +0800
From:	yalin wang <yalin.wang2010@...il.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
	hpa@...or.com, x86@...nel.org,
	open list <linux-kernel@...r.kernel.org>,
	Will Deacon <will.deacon@....com>
Subject: Re: [x86] copy_from{to}_user question


> On Aug 14, 2015, at 00:43, Borislav Petkov <bp@...e.de> wrote:
> 
> On Thu, Aug 13, 2015 at 06:04:54PM +0800, yalin wang wrote:
>> we store type into one fix register, for example r12 ,
>> then in fix up code, we can know the exception is caused by copy_from
>> copy_to or copy_in user function by check r12 value(0 , 1 ,2 value), then if 
>> it is copy_from, we only allow read fault, if the exception is write fault, panic() .
>> 
>> the same rules also apply to copy_to / copy_in function .
>> 
>> is it possible to change it like this ?
> 
> ... and we'll do all that jumping through hoops to fix what actual,
> real-life problem exactly?
i just want the x86 copy_from{to,in}_user() function have 
the same behaviour as other platforms.
and can disclose potential BUGs in kernel, if do like this.

Thanks.

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