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Date: Mon, 13 Nov 2017 16:43:26 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] x86/mm: Do not allow non-MAP_FIXED mapping across
 DEFAULT_MAP_WINDOW border
In-Reply-To: <20171107130539.52676-1-kirill.shutemov@linux.intel.com>
Message-ID: <alpine.DEB.2.20.1711131642370.1851@nanos>
References: <20171107130539.52676-1-kirill.shutemov@linux.intel.com>
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To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>, Linus Torvalds <torvalds@linux-foundation.org>, x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@amacapital.net>, Cyrill Gorcunov <gorcunov@openvz.org>, Nicholas Piggin <npiggin@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org

On Tue, 7 Nov 2017, Kirill A. Shutemov wrote:

> In case of 5-level paging, we don't put any mapping above 47-bit, unless
> userspace explicitly asked for it.
> 
> Userspace can ask for allocation from full address space by specifying
> hint address above 47-bit.
> 
> Nicholas noticed that current implementation violates this interface:
> we can get vma partly in high addresses if we ask for a mapping at very
> end of 47-bit address space.
> 
> Let's make sure that, when consider hint address for non-MAP_FIXED
> mapping, start and end of resulting vma are on the same side of 47-bit
> border.

What happens for mappings with MAP_FIXED which cross the border?

Thanks,

	tglx

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