From: David Gibson <david@gibson.dropbear.id.au>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
Linus Torvalds <torvalds@osdl.org>
Subject: Re: [BUG] hugetlb MAP_PRIVATE mapping vs /dev/zero
Date: Fri, 2 Jul 2004 11:20:12 +1000 [thread overview]
Message-ID: <20040702012012.GC5937@zax> (raw)
In-Reply-To: <40E43BDE.85C5D670@tv-sign.ru>
On Thu, Jul 01, 2004 at 08:29:18PM +0400, Oleg Nesterov wrote:
> Hello.
>
> Hugetlbfs mmap with MAP_PRIVATE becomes MAP_SHARED
> silently, but vma->vm_flags have no VM_SHARED bit.
> I think it make sense to forbid MAP_PRIVATE in
> hugetlbfs_file_mmap() because it may confuse user
> space applications. But the real bug is that reading
> from /dev/zero into hugetlb will do:
>
> read_zero()
> read_zero_pagealigned()
> if (vma->vm_flags & VM_SHARED)
> break; // OK if MAP_PRIVATE
> zap_page_range();
> zeromap_page_range();
>
> We can fix hugetlbfs_file_mmap() or read_zero_pagealigned()
> or both.
Err... surely we need to fix both, yes?
--
David Gibson | For every complex problem there is a
david AT gibson.dropbear.id.au | solution which is simple, neat and
| wrong.
http://www.ozlabs.org/people/dgibson
next prev parent reply other threads:[~2004-07-02 1:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-01 16:29 [BUG] hugetlb MAP_PRIVATE mapping vs /dev/zero Oleg Nesterov
2004-07-01 16:56 ` William Lee Irwin III
2004-07-01 21:55 ` Andrew Morton
2004-07-02 1:20 ` David Gibson [this message]
2004-07-02 2:44 ` William Lee Irwin III
2004-07-02 3:49 ` David Gibson
2004-07-02 4:12 ` David Gibson
2004-07-02 4:21 ` William Lee Irwin III
-- strict thread matches above, loose matches on Subject: below --
2004-07-02 12:12 Oleg Nesterov
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