linux-kernel - Re: [PATCH] mm: get_user_pages(write,force) refuse to COW in shared areas

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]

Date:	Fri, 4 Apr 2014 07:52:47 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	"Kirill A. Shutemov" <kirill@...temov.name>
cc:	Hugh Dickins <hughd@...gle.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kara <jack@...e.cz>, Roland Dreier <roland@...nel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Konstantin Khlebnikov <koct9i@...il.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>,
	Omar Ramirez Luna <omar.ramirez@...itl.com>,
	Inki Dae <inki.dae@...sung.com>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org, linux-rdma@...r.kernel.org,
	linux-media@...r.kernel.org
Subject: Re: [PATCH] mm: get_user_pages(write,force) refuse to COW in shared
 areas

On Fri, 4 Apr 2014, Kirill A. Shutemov wrote:
> 
> There's comment in do_wp_page() which is not true anymore with patch
> applied. It should be fixed.

The * Only catch write-faults on shared writable pages,
    * read-only shared pages can get COWed by
    * get_user_pages(.write=1, .force=1).

Yes, I went back and forth on that: I found it difficult to remove that
comment without also simplifying the VM_WRITE|VM_SHARED test immediately
above it, possibly even looking again at the ordering of those tests.

In the end I decided to leave changing it to when we do the other
little cleanups outside get_user_pages(), after it's become clear
whether the new EFAULT is troublesome or not.  Most of my testing
had been without any change in do_wp_page(), so I left that out.

> 
> Otherwise, looks good to me:
> 
> Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

Thanks,
Hugh
--
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/