Subject: Re: [PATCH] mm: fix incorrect behavior when process virtual address
 space limit is exceeded
To: Oleg Nesterov <oleg@redhat.com>,
        Piotr Kwapulinski <kwapulinski.piotr@gmail.com>
References: <1447695379-14526-1-git-send-email-kwapulinski.piotr@gmail.com>
 <20151117161928.GA9611@redhat.com>
CC: <akpm@linux-foundation.org>, <mszeredi@suse.cz>, <viro@zeniv.linux.org.uk>,
        <dave@stgolabs.net>, <kirill.shutemov@linux.intel.com>,
        <n-horiguchi@ah.jp.nec.com>, <aarcange@redhat.com>, <mhocko@suse.com>,
        <iamjoonsoo.kim@lge.com>, <jack@suse.cz>, <xiexiuqi@huawei.com>,
        <vbabka@suse.cz>, <Vineet.Gupta1@synopsys.com>, <riel@redhat.com>,
        <gang.chen.5i5j@gmail.com>, <linux-kernel@vger.kernel.org>,
        <linux-mm@kvack.org>
From: Chris Metcalf <cmetcalf@ezchip.com>
Message-ID: <564B6605.8080808@ezchip.com>
Date: Tue, 17 Nov 2015 12:38:13 -0500
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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, so do_mmap() would fail the call in
get_unmapped_area().

-- 
Chris Metcalf, EZChip Semiconductor
http://www.ezchip.com

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