linux-kernel - Re: [REGRESSION] 4.2-rc2: early boot memory corruption from FPU rework

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Date:	Wed, 15 Jul 2015 19:51:18 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Dave Hansen <dave.hansen@...ux.intel.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andy Lutomirski <luto@...capital.net>,
	Borislav Petkov <bp@...en8.de>,
	Fenghua Yu <fenghua.yu@...el.com>,
	"H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>
Subject: Re: [REGRESSION] 4.2-rc2: early boot memory corruption from FPU rework

On Wed, Jul 15, 2015 at 5:34 PM, Dave Hansen
<dave.hansen@...ux.intel.com> wrote:
>
> I understand why you were misled by it, but the old "xsave_hdr_struct"
> was wrong.  Fenghua even posted patches to remove it before the FPU
> rework (you were cc'd):
>
>         https://lkml.org/lkml/2015/4/18/164

Oh, and that patch looks like a good idea.

I wish there was some way to make sure sizeof() fail on it so that
we'd enforce that nobody allocates that thing as-is. I had this dim
memory that an unsized array at the end would do that, but I was
clearly wrong. It's just the array itself you can't do sizeof on, not
the structure that contains it. Is there some magic trick that I'm
forgetting?

                      Linus
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