linux-kernel - Re: [patch V3 12/12] select: Convert to scoped masked user access

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Message-ID: <20251017103554.GY4067720@noisy.programming.kicks-ass.net>
Date: Fri, 17 Oct 2025 12:35:54 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
	linux-fsdevel@...r.kernel.org, kernel test robot <lkp@...el.com>,
	Russell King <linux@...linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org,
	Linus Torvalds <torvalds@...ux-foundation.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>,
	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>
Subject: Re: [patch V3 12/12] select: Convert to scoped masked user access

On Fri, Oct 17, 2025 at 12:09:18PM +0200, Thomas Gleixner wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> Replace the open coded implementation with the scoped masked user access
> guard.
> 
> No functional change intended.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Cc: Alexander Viro <viro@...iv.linux.org.uk>
> Cc: Christian Brauner <brauner@...nel.org>
> Cc: Jan Kara <jack@...e.cz>
> Cc: linux-fsdevel@...r.kernel.org
> ---
> V3: Adopt to scope changes
> ---
>  fs/select.c |   12 ++++--------
>  1 file changed, 4 insertions(+), 8 deletions(-)
> ---
> --- a/fs/select.c
> +++ b/fs/select.c
> @@ -776,17 +776,13 @@ static inline int get_sigset_argpack(str
>  {
>  	// the path is hot enough for overhead of copy_from_user() to matter
>  	if (from) {
> -		if (can_do_masked_user_access())
> -			from = masked_user_access_begin(from);
> -		else if (!user_read_access_begin(from, sizeof(*from)))
> -			return -EFAULT;
> -		unsafe_get_user(to->p, &from->p, Efault);
> -		unsafe_get_user(to->size, &from->size, Efault);
> -		user_read_access_end();
> +		scoped_masked_user_rw_access(from, Efault) {

Should this not be: scoped_masked_user_read_access() ?

> +			unsafe_get_user(to->p, &from->p, Efault);
> +			unsafe_get_user(to->size, &from->size, Efault);
> +		}
>  	}
>  	return 0;
>  Efault:
> -	user_read_access_end();
>  	return -EFAULT;
>  }
>  
>