linux-kernel - Re: [PATCH -next v5 2/3] x86/mce: set MCE_IN_KERNEL_COPYIN for DEFAULT_MCE

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Date: Wed, 27 Mar 2024 23:05:11 +0100
From: Borislav Petkov <bp@...en8.de>
To: Tong Tiangen <tongtiangen@...wei.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	wangkefeng.wang@...wei.com,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, Tony Luck <tony.luck@...el.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Naoya Horiguchi <naoya.horiguchi@....com>,
	linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
	linux-mm@...ck.org, Guohanjun <guohanjun@...wei.com>
Subject: Re: [PATCH -next v5 2/3] x86/mce: set MCE_IN_KERNEL_COPYIN for
 DEFAULT_MCE_SAFE exception

On Sun, Feb 18, 2024 at 06:08:14PM +0800, Tong Tiangen wrote:
> 1. The copy_mc_to_kernel() is used in the coredump, KSM, and COW
> scenarios, in these scenarios, the src mem stores the user data and the
> kernel use kernel address to access the src mem(using kmap()).
> 
> 2. the src mem of copy_mc_to_user() is currently only used by the DAX:

You mean just because it currently is used somewhere which probably is
ok - no clue what DAX does - and even if the source address is still
*kernel* memory and even at the danger that someone else might use it in
the future and think the handling on a potential #MC is ok, you're still
arguing that this is the right thing to do perhaps because it fits your
use case?!

Sorry Tiangen, not gonna happen.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette