linux-kernel - Re: [RFC] dev/mem: "memtester -p 0x6c80000000000 10G" cause crash

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Message-ID: <590848B0.2000801@huawei.com>
Date:   Tue, 2 May 2017 16:52:00 +0800
From:   Xishi Qiu <qiuxishi@...wei.com>
To:     Michal Hocko <mhocko@...nel.org>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Joonsoo Kim <js1304@...il.com>,
        "Johannes Weiner" <hannes@...xchg.org>,
        Rik van Riel <riel@...hat.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        zhong jiang <zhongjiang@...wei.com>
Subject: Re: [RFC] dev/mem: "memtester -p 0x6c80000000000 10G" cause crash

On 2017/5/2 16:43, Michal Hocko wrote:

> On Tue 02-05-17 15:59:23, Xishi Qiu wrote:
>> Hi, I use "memtester -p 0x6c80000000000 10G" to test physical address 0x6c80000000000
>> Because this physical address is invalid, and valid_mmap_phys_addr_range()
>> always return 1, so it causes crash.
>>
>> My question is that should the user assure the physical address is valid?
> 
> We already seem to be checking range_is_allowed(). What is your
> CONFIG_STRICT_DEVMEM setting? The code seems to be rather confusing but
> my assumption is that you better know what you are doing when mapping
> this file.
> 

HI Michal,

CONFIG_STRICT_DEVMEM=y, and range_is_allowed() will skip memory, but
0x6c80000000000 is not memory, it is just a invalid address, so it cause
crash. 
You mean the user should assure the physical address is valid, right?

Thanks,
Xishi Qiu

>> ...
>> [ 169.147578] ? panic+0x1f1/0x239
>> [ 169.150789] oops_end+0xb8/0xd0
>> [ 169.153910] pgtable_bad+0x8a/0x95
>> [ 169.157294] __do_page_fault+0x3aa/0x4a0
>> [ 169.161194] do_page_fault+0x30/0x80
>> [ 169.164750] ? do_syscall_64+0x175/0x180
>> [ 169.168649] page_fault+0x28/0x30
>>
>> Thanks,
>> Xishi Qiu
>