linux-kernel - Re: [patch V4 10/12] futex: Convert to scoped user access

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAHk-=wgLAJuJ8SP8NiSGbXJQMdxiPkBN32EvAy9R8kCnva4dfg@mail.gmail.com>
Date: Wed, 22 Oct 2025 05:16:40 -1000
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Darren Hart <dvhart@...radead.org>, Davidlohr Bueso <dave@...olabs.net>, 
	André Almeida <andrealmeid@...lia.com>, 
	kernel test robot <lkp@...el.com>, Russell King <linux@...linux.org.uk>, 
	linux-arm-kernel@...ts.infradead.org, x86@...nel.org, 
	Madhavan Srinivasan <maddy@...ux.ibm.com>, Michael Ellerman <mpe@...erman.id.au>, 
	Nicholas Piggin <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>, 
	linuxppc-dev@...ts.ozlabs.org, Paul Walmsley <pjw@...nel.org>, 
	Palmer Dabbelt <palmer@...belt.com>, linux-riscv@...ts.infradead.org, 
	Heiko Carstens <hca@...ux.ibm.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Sven Schnelle <svens@...ux.ibm.com>, linux-s390@...r.kernel.org, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Andrew Cooper <andrew.cooper3@...rix.com>, 
	David Laight <david.laight.linux@...il.com>, Julia Lawall <Julia.Lawall@...ia.fr>, 
	Nicolas Palix <nicolas.palix@...g.fr>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, linux-fsdevel@...r.kernel.org
Subject: Re: [patch V4 10/12] futex: Convert to scoped user access

On Wed, 22 Oct 2025 at 02:49, Thomas Gleixner <tglx@...utronix.de> wrote:
>
> From: Thomas Gleixner <tglx@...utronix.de>
>
> Replace the open coded implementation with the new get/put_user_scoped()
> helpers.

Well, "scoped" here makes no sense in the name, since it isn't scoped
in any way, it just uses the scoped helpers.

I also wonder if we should just get rid of the futex_get/put_value()
macros entirely. I did those masked user access things them long ago
because that code used "__get_user()" and "__put_user()", and I was
removing those helpers and making it match the pattern elsewhere, but
I do wonder if there is any advantage left to them all.

On x86, just using "get_user()" and "put_user()" should work fine now.
Yes, they check the address, but these days *those* helpers use that
masked user address trick too, so there is no real cost to it.

The only cost would be the out-of-line function call, I think. Maybe
that is a sufficiently big cost here.

             Linus