From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f69.google.com (mail-wm0-f69.google.com [74.125.82.69]) by kanga.kvack.org (Postfix) with ESMTP id 94A706B0350 for ; Tue, 2 May 2017 05:34:18 -0400 (EDT) Received: by mail-wm0-f69.google.com with SMTP id z129so1003960wmb.23 for ; Tue, 02 May 2017 02:34:18 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [45.249.212.189]) by mx.google.com with ESMTPS id j16si19529732wrb.230.2017.05.02.02.34.16 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 02 May 2017 02:34:17 -0700 (PDT) Message-ID: <590851CC.2070402@huawei.com> Date: Tue, 2 May 2017 17:30:52 +0800 From: Xishi Qiu MIME-Version: 1.0 Subject: Re: [RFC] dev/mem: "memtester -p 0x6c80000000000 10G" cause crash References: <59083C5B.5080204@huawei.com> <20170502084323.GG14593@dhcp22.suse.cz> <590848B0.2000801@huawei.com> <20170502091630.GH14593@dhcp22.suse.cz> In-Reply-To: <20170502091630.GH14593@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Andrew Morton , Mel Gorman , Vlastimil Babka , Joonsoo Kim , Johannes Weiner , Rik van Riel , Shakeel Butt , Linux MM , LKML , zhong jiang On 2017/5/2 17:16, Michal Hocko wrote: > On Tue 02-05-17 16:52:00, Xishi Qiu wrote: >> 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. > > OK, I only now looked at the value. It is beyond addressable limit > (for 47b address space). None of the checks seems to stop this because > range_is_allowed() resp. its devmem_is_allowed() will allow it as a > non RAM (!page_is_ram check). I am not really sure how to fix this or > whether even we should try to fix this particular problem. As I've said > /dev/mem is dangerous and you should better know what you are doing when > accessing it. > OK, I know, thank you! Thanks, Xishi Qiu -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org