linux-kernel - Re: [PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

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Message-ID: <20241031135916.GDZyONNENEDAViMSOZ@fat_crate.local>
Date: Thu, 31 Oct 2024 14:59:16 +0100
From: Borislav Petkov <bp@...en8.de>
To: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, Baoquan He <bhe@...hat.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Tom Lendacky <thomas.lendacky@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Sean Christopherson <seanjc@...gle.com>,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	Kai Huang <kai.huang@...el.com>
Subject: Re: [PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address
 wrap to zero

On Thu, Oct 31, 2024 at 12:11:52PM +0200, Kirill A. Shutemov wrote:
> Do we have magic words for that?

No clue.

> I tried to express that in the second paragraph: "no such users in the
> upstream".

Right, so perhaps better to spell it out explicitly:

"Backporter's note:

This fixes a theoretical issue only and there's no need to backport it to
stable."

at the end of the commit message.

> > And which commit is it fixing?
> > 
> > aece27851d44 ("x86, 64bit, mm: Add generic kernel/ident mapping helper")
> > perhaps?
> 
> This one is closer:
> 
> e4630fdd4763 ("x86/power/64: Always create temporary identity mapping correctly")
> 
> It adds x86_mapping_info::offset.

But aece27851d44 has the faulty check...

-- 
Regards/Gruss,
    Boris.

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