linux-kernel - Re: [PATCH v4] x86/fpu: Fix NULL dereference in avx512

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Message-ID: <f6f7a962-eae8-45e0-a8a5-ead0b9f37575@intel.com>
Date: Mon, 11 Aug 2025 13:16:08 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: Dave Hansen <dave.hansen@...el.com>, Dave Hansen
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>
CC: Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>, "Thomas
 Gleixner" <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "Sean
 Christopherson" <seanjc@...gle.com>, Peter Zijlstra <peterz@...radead.org>,
	Vignesh Balasubramanian <vigbalas@....com>, Rick Edgecombe
	<rick.p.edgecombe@...el.com>, Oleg Nesterov <oleg@...hat.com>, "Chang S .
 Bae" <chang.seok.bae@...el.com>, Brian Gerst <brgerst@...il.com>, "Eric
 Biggers" <ebiggers@...gle.com>, Kees Cook <kees@...nel.org>, Chao Gao
	<chao.gao@...el.com>, Christoph Hellwig <hch@...radead.org>, Fushuai Wang
	<wangfushuai@...du.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] x86/fpu: Fix NULL dereference in avx512_status()

On 8/11/2025 12:22 PM, Dave Hansen wrote:
> 
> The changelog also isn't really converging, so I gave it a go to
> rewrite it. Is this missing anything?
> 

Thank you! Your changelog covers the essentials and makes it concise.
The dual nature of x86_task_fpu() was making it hard to write for me.

A couple of typos:

> This is because the AVX-512 timestamp code uses x86_task_fpu() doesn't
								^^^but> check it for NULL.

Missing "but"

> If anyone ever wants to track kernel thread AVX-512 use, the can come
> back later and do it properly, separate from this bug fix.

s/the/they

> https://git.kernel.org/pub/scm/linux/kernel/git/daveh/devel.git/commit/?h=testme&id=d61828dcbcff4ac80b91f5071ba6d21ef6c97347

It probably doesn't matter, but the documentation suggests ordering
Co-developed-by and Signed-off-by tags a bit differently.

"...every Co-developed-by: must be immediately followed by a
Signed-off-by: of the associated co-author."

https://www.kernel.org/doc/html/latest/process/submitting-patches.html#when-to-use-acked-by-cc-and-co-developed-by

Example of a patch submitted by a Co-developed-by: author:

From: From Author <from@...hor.example.org>

<changelog>

Co-developed-by: Random Co-Author <random@...uthor.example.org>
Signed-off-by: Random Co-Author <random@...uthor.example.org>
Signed-off-by: From Author <from@...hor.example.org>
Co-developed-by: Submitting Co-Author <sub@...uthor.example.org>
Signed-off-by: Submitting Co-Author <sub@...uthor.example.org>