linux-kernel - Re: [PATCH 09/14] m68k: drop custom __access

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Date:   Tue, 15 Feb 2022 00:37:41 +0000
From:   Al Viro <viro@...iv.linux.org.uk>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Christoph Hellwig <hch@....de>, linux-arch@...r.kernel.org,
        linux-mm@...ck.org, linux-api@...r.kernel.org, arnd@...db.de,
        linux-kernel@...r.kernel.org, linux@...linux.org.uk,
        will@...nel.org, guoren@...nel.org, bcain@...eaurora.org,
        geert@...ux-m68k.org, monstr@...str.eu, tsbogend@...ha.franken.de,
        nickhu@...estech.com, green.hu@...il.com, dinguyen@...nel.org,
        shorne@...il.com, deller@....de, mpe@...erman.id.au,
        peterz@...radead.org, mingo@...hat.com, mark.rutland@....com,
        hca@...ux.ibm.com, dalias@...c.org, davem@...emloft.net,
        richard@....at, x86@...nel.org, jcmvbkbc@...il.com,
        ebiederm@...ssion.com, akpm@...ux-foundation.org, ardb@...nel.org,
        linux-alpha@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-csky@...r.kernel.org,
        linux-hexagon@...r.kernel.org, linux-ia64@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        openrisc@...ts.librecores.org, linux-parisc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-riscv@...ts.infradead.org,
        linux-s390@...r.kernel.org, linux-sh@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-um@...ts.infradead.org,
        linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCH 09/14] m68k: drop custom __access_ok()

On Mon, Feb 14, 2022 at 05:34:47PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> While most m68k platforms use separate address spaces for user
> and kernel space, at least coldfire does not, and the other
> ones have a TASK_SIZE that is less than the entire 4GB address
> range.
> 
> Using the generic implementation of __access_ok() stops coldfire
> user space from trivially accessing kernel memory, and is probably
> the right thing elsewhere for consistency as well.

Perhaps simply wrap that sucker into #ifdef CONFIG_CPU_HAS_ADDRESS_SPACES
(and trim the comment down to "coldfire and 68000 will pick generic
variant")?

> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/m68k/include/asm/uaccess.h | 13 -------------
>  1 file changed, 13 deletions(-)
> 
> diff --git a/arch/m68k/include/asm/uaccess.h b/arch/m68k/include/asm/uaccess.h
> index d6bb5720365a..64914872a5c9 100644
> --- a/arch/m68k/include/asm/uaccess.h
> +++ b/arch/m68k/include/asm/uaccess.h
> @@ -10,19 +10,6 @@
>  #include <linux/compiler.h>
>  #include <linux/types.h>
>  #include <asm/extable.h>
> -
> -/* We let the MMU do all checking */
> -static inline int __access_ok(const void __user *addr,
> -			    unsigned long size)
> -{
> -	/*
> -	 * XXX: for !CONFIG_CPU_HAS_ADDRESS_SPACES this really needs to check
> -	 * for TASK_SIZE!
> -	 * Removing this helper is probably sufficient.
> -	 */
> -	return 1;
> -}
> -#define __access_ok __access_ok
>  #include <asm-generic/access_ok.h>
>  
>  /*
> -- 
> 2.29.2
>