linux-kernel - Re: [PATCH 4/9] x86/gup: Replace ACCESS_ONCE with READ

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: <20141204001051.GA25340@linux.vnet.ibm.com>
Date:	Wed, 3 Dec 2014 16:10:51 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Christian Borntraeger <borntraeger@...ibm.com>
Cc:	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
	torvalds@...ux-foundation.org
Subject: Re: [PATCH 4/9] x86/gup: Replace ACCESS_ONCE with READ_ONCE

On Wed, Dec 03, 2014 at 11:30:16PM +0100, Christian Borntraeger wrote:
> ACCESS_ONCE does not work reliably on non-scalar types. For
> example gcc 4.6 and 4.7 might remove the volatile tag for such
> accesses during the SRA (scalar replacement of aggregates) step
> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145)
> 
> Change the gup code to replace ACCESS_ONCE with READ_ONCE.
> 
> Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>

Acked-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

> ---
>  arch/x86/mm/gup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
> index 207d9aef..d754782 100644
> --- a/arch/x86/mm/gup.c
> +++ b/arch/x86/mm/gup.c
> @@ -15,7 +15,7 @@
>  static inline pte_t gup_get_pte(pte_t *ptep)
>  {
>  #ifndef CONFIG_X86_PAE
> -	return ACCESS_ONCE(*ptep);
> +	return READ_ONCE(*ptep);
>  #else
>  	/*
>  	 * With get_user_pages_fast, we walk down the pagetables without taking
> -- 
> 1.9.3
> 

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/