linux-kernel - Re: [patch V4 07/12] uaccess: Provide scoped user access regions

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Message-ID: <20251022142359.GQ4067720@noisy.programming.kicks-ass.net>
Date: Wed, 22 Oct 2025 16:23:59 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: David Laight <david.laight.linux@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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>, 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,
	Julia Lawall <Julia.Lawall@...ia.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Darren Hart <dvhart@...radead.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	André Almeida <andrealmeid@...lia.com>,
	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 07/12] uaccess: Provide scoped user access regions

On Wed, Oct 22, 2025 at 03:20:06PM +0100, David Laight wrote:

> I think that 'feature' should be marked as a 'bug', consider code like:
> 	for (; len >= sizeof (*uaddr); uaddr++; len -= sizeof (*uaddr)) {
> 		scoped_user_read_access(uaddr, Efault) {
> 			int frag_len;
> 			unsafe_get_user(frag_len, &uaddr->len, Efault);
> 			if (!frag_len)
> 				break;
> 			...
> 		}
> 		...
> 	}
> 

All the scoped_* () things are for loops. break is a valid way to
terminate them.