linux-kernel - Re: [patch V5 08/12] uaccess: Provide put/get_user

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: <fc087f38-2e14-41d1-8044-c054eb41ad19@csgroup.eu>
Date: Tue, 4 Nov 2025 07:30:32 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Thomas Gleixner <tglx@...utronix.de>, LKML <linux-kernel@...r.kernel.org>
Cc: 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>,
 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>,
 Peter Zijlstra <peterz@...radead.org>, 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 V5 08/12] uaccess: Provide put/get_user_inline()



Le 27/10/2025 à 09:43, Thomas Gleixner a écrit :
> Provide conveniance wrappers around scoped user access similiar to
> put/get_user(), which reduce the usage sites to:
> 
>         if (!get_user_inline(val, ptr))
>         		return -EFAULT;
> 
> Should only be used if there is a demonstrable performance benefit.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>

> ---
> V5: Rename to inline
> V4: Rename to scoped
> ---
>   include/linux/uaccess.h |   50 ++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 50 insertions(+)
> 
> --- a/include/linux/uaccess.h
> +++ b/include/linux/uaccess.h
> @@ -825,6 +825,56 @@ for (bool done = false; !done; done = tr
>   #define scoped_user_rw_access(uptr, elbl)				\
>   	scoped_user_rw_access_size(uptr, sizeof(*(uptr)), elbl)
>   
> +/**
> + * get_user_inline - Read user data inlined
> + * @val:	The variable to store the value read from user memory
> + * @usrc:	Pointer to the user space memory to read from
> + *
> + * Return: 0 if successful, -EFAULT when faulted
> + *
> + * Inlined variant of get_user(). Only use when there is a demonstrable
> + * performance reason.
> + */
> +#define get_user_inline(val, usrc)				\
> +({								\
> +	__label__ efault;					\
> +	typeof(usrc) _tmpsrc = usrc;				\
> +	int _ret = 0;						\
> +								\
> +	scoped_user_read_access(_tmpsrc, efault)		\
> +		unsafe_get_user(val, _tmpsrc, efault);		\
> +	if (0) {						\
> +	efault:							\
> +		_ret = -EFAULT;					\
> +	}							\
> +	_ret;							\
> +})
> +
> +/**
> + * put_user_inline - Write to user memory inlined
> + * @val:	The value to write
> + * @udst:	Pointer to the user space memory to write to
> + *
> + * Return: 0 if successful, -EFAULT when faulted
> + *
> + * Inlined variant of put_user(). Only use when there is a demonstrable
> + * performance reason.
> + */
> +#define put_user_inline(val, udst)				\
> +({								\
> +	__label__ efault;					\
> +	typeof(udst) _tmpdst = udst;				\
> +	int _ret = 0;						\
> +								\
> +	scoped_user_write_access(_tmpdst, efault)		\
> +		unsafe_put_user(val, _tmpdst, efault);		\
> +	if (0) {						\
> +	efault:							\
> +		_ret = -EFAULT;					\
> +	}							\
> +	_ret;							\
> +})
> +
>   #ifdef CONFIG_HARDENED_USERCOPY
>   void __noreturn usercopy_abort(const char *name, const char *detail,
>   			       bool to_user, unsigned long offset,
>