linux-kernel - Re: [PATCHv2 1/2] x86/mm: Do not allow non-MAP_FIXED mapping across DEFAULT_MAP

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Message-ID: <20171114202102.crpgiwgv2lu5aboq@node.shutemov.name>
Date:   Tue, 14 Nov 2017 23:21:02 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        Nicholas Piggin <npiggin@...il.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 1/2] x86/mm: Do not allow non-MAP_FIXED mapping across
 DEFAULT_MAP_WINDOW border

On Tue, Nov 14, 2017 at 05:01:50PM +0100, Thomas Gleixner wrote:
> @@ -198,11 +199,14 @@ arch_get_unmapped_area_topdown(struct fi
>  	/* requesting a specific address */
>  	if (addr) {
>  		addr = PAGE_ALIGN(addr);
> +		if (!mmap_address_hint_valid(addr, len))
> +			goto get_unmapped_area;
> +

Here and in hugetlb_get_unmapped_area(), we should align the addr after
the check, not before. Otherwise the alignment itself can bring us over
the borderline as we align up.

-- 
 Kirill A. Shutemov