linux-kernel - Re: [PATCH v4 1/3] x86/mce: Use is_copy_from_user() to determine copy-from-user context

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Message-ID: <0f4dfbde-74a5-451d-8764-cc7767596654@linux.alibaba.com>
Date: Sat, 8 Mar 2025 19:27:26 +0800
From: Shuai Xue <xueshuai@...ux.alibaba.com>
To: Borislav Petkov <bp@...en8.de>, "Luck, Tony" <tony.luck@...el.com>
Cc: "peterz@...radead.org" <peterz@...radead.org>,
 "catalin.marinas@....com" <catalin.marinas@....com>,
 "yazen.ghannam@....com" <yazen.ghannam@....com>,
 "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
 "linmiaohe@...wei.com" <linmiaohe@...wei.com>,
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 "tglx@...utronix.de" <tglx@...utronix.de>,
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 "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
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 "baolin.wang@...ux.alibaba.com" <baolin.wang@...ux.alibaba.com>,
 "tianruidong@...ux.alibaba.com" <tianruidong@...ux.alibaba.com>
Subject: Re: [PATCH v4 1/3] x86/mce: Use is_copy_from_user() to determine
 copy-from-user context



在 2025/3/8 07:22, Borislav Petkov 写道:
> On Fri, Mar 07, 2025 at 11:11:26PM +0000, Luck, Tony wrote:
>> As for "explicit markup" I don't think it would be better to decorate
>> every get_user() and copy_from_user() with some "this one can
>> recover from #MC"
> 
> I don't mean every function - I mean what we had there with EX_TYPE_UACCESS.
> That is explicit and unambiguous. Proving that is_copy_from_user() is always
> correct is a lot harder.
> 
>> Note also that "what we had recently" was fragile, broke, and resulted
>> in this regression.
> 
> Because those exception types got renamed? Oh well, that should've been
> reverted actually but no one involved realized that MCE is using those.
> 
> And I'm not saying this is the only way to solve this. We could do something
> like collecting all addresses on which an MCE can be recoverable, for example.
> We haven't considered it that important... yet.
> 
> Looks like we're going to try this new is_copy_from_user() thing now and then
> see where it gets us.
> 
> So, after the commit message has been fixed:
> 
> Acked-by: Borislav Petkov (AMD) <bp@...en8.de>
> 
> I'm presuming, this is going through akpm...
> 

Thanks.
Shuai