linux-kernel - Re: [PATCH] mm: fix incorrect behavior when process virtual address space limit is exceeded

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Message-ID: <20151117190350.GA9790@redhat.com>
Date:	Tue, 17 Nov 2015 20:03:50 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Chris Metcalf <cmetcalf@...hip.com>
Cc:	Piotr Kwapulinski <kwapulinski.piotr@...il.com>,
	akpm@...ux-foundation.org, mszeredi@...e.cz,
	viro@...iv.linux.org.uk, dave@...olabs.net,
	kirill.shutemov@...ux.intel.com, n-horiguchi@...jp.nec.com,
	aarcange@...hat.com, mhocko@...e.com, iamjoonsoo.kim@....com,
	jack@...e.cz, xiexiuqi@...wei.com, vbabka@...e.cz,
	Vineet.Gupta1@...opsys.com, riel@...hat.com,
	gang.chen.5i5j@...il.com, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCH] mm: fix incorrect behavior when process virtual
	address space limit is exceeded

On 11/17, Chris Metcalf wrote:
>
> On 11/17/2015 11:19 AM, Oleg Nesterov wrote:
>> On 11/16, Piotr Kwapulinski wrote:
>>> @@ -1551,7 +1552,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>>>   		 * MAP_FIXED may remove pages of mappings that intersects with
>>>   		 * requested mapping. Account for the pages it would unmap.
>>>   		 */
>>> -		if (!(vm_flags & MAP_FIXED))
>>> +		if (!(flags & MAP_FIXED))
>>>   			return -ENOMEM;
>> And afaics arch/tile/mm/elf.c can use do_mmap(MAP_FIXED ...) rather than
>> mmap_region(), it can be changed by a separate patch. In this case we can
>> unexport mmap_region().
>
> The problem is that we are mapping a region of virtual address space that
> the chip provides for setting up interrupt handlers (at 0xfc000000) but that
> is above the TASK_SIZE cutoff,

Ah, I didn't bother to read the comment in arch_setup_additional_pages().
Thanks for your explanation.

Oleg.

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