linux-kernel - Re: [PATCH v2] rmap: fix theoretical race between do_wp_page and shrink_active

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] [day] [month] [year] [list]

Message-ID: <20150513080823.GH17628@esperanza>
Date:	Wed, 13 May 2015 11:08:23 +0300
From:	Vladimir Davydov <vdavydov@...allels.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Rik van Riel <riel@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
Subject: Re: [PATCH v2] rmap: fix theoretical race between do_wp_page and
 shrink_active_list

On Tue, May 12, 2015 at 03:28:40PM -0700, Andrew Morton wrote:
> Please let's not put things like WRITE_ONCE() in there without
> documenting them - otherwise it's terribly hard for readers to work out
> why it was added.
> 
> How's this look?
> 
> --- a/mm/rmap.c~rmap-fix-theoretical-race-between-do_wp_page-and-shrink_active_list-fix
> +++ a/mm/rmap.c
> @@ -950,6 +950,11 @@ void page_move_anon_rmap(struct page *pa
>  	VM_BUG_ON_PAGE(page->index != linear_page_index(vma, address), page);
>  
>  	anon_vma = (void *) anon_vma + PAGE_MAPPING_ANON;
> +	/*
> +	 * Ensure that anon_vma and the PAGE_MAPPING_ANON bit are written
> +	 * simultaneously, so a concurrent reader (eg shrink_active_list) will
> +	 * not see one without the other.
> +	 */
>  	WRITE_ONCE(page->mapping, (struct address_space *) anon_vma);
>  }

Looks good to me.

Thanks,
Vladimir
--
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/