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Date: Thu, 1 Jul 2004 09:56:55 -0700
From: William Lee Irwin III <wli@holomorphy.com>
To: Oleg Nesterov <oleg@tv-sign.ru>
Cc: linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>,
       David Gibson <david@gibson.dropbear.id.au>,
       Linus Torvalds <torvalds@osdl.org>
Subject: Re: [BUG] hugetlb MAP_PRIVATE mapping vs /dev/zero
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	Oleg Nesterov <oleg@tv-sign.ru>, linux-kernel@vger.kernel.org,
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On Thu, Jul 01, 2004 at 08:29:18PM +0400, Oleg Nesterov wrote:
> 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.

Best to fix hugetlbfs_file_mmap().


-- wli