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

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Date:   Tue, 2 May 2017 10:43:23 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Xishi Qiu <qiuxishi@...wei.com>
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 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.

> ...
> [ 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

-- 
Michal Hocko
SUSE Labs