From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from NAM01-BN3-obe.outbound.protection.outlook.com (mail-bn3nam01on070d.outbound.protection.outlook.com [IPv6:2a01:111:f400:fe41::70d]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ml01.01.org (Postfix) with ESMTPS id F1AC81A1DE9 for ; Tue, 23 Aug 2016 16:47:42 -0700 (PDT) From: "Kani, Toshimitsu" Subject: Re: [PATCH] memremap: Fix NULL pointer BUG in get_zone_device_page() Date: Tue, 23 Aug 2016 23:47:39 +0000 Message-ID: <1471996023.1532.6.camel@hpe.com> References: <1471977800-12688-1-git-send-email-toshi.kani@hpe.com> In-Reply-To: Content-Language: en-US Content-ID: <4E67E24F580E834DB5BFC47721541CF6@NAMPRD84.PROD.OUTLOOK.COM> MIME-Version: 1.0 List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: linux-nvdimm-bounces@lists.01.org Sender: "Linux-nvdimm" To: "dan.j.williams@intel.com" Cc: "ard.biesheuvel@linaro.org" , "Mulumudi, Abhilash Kumar , linux-nvdimm@lists.01.org" , "linux-kernel@vger.kernel.org" , "akpm@linux-foundation.org" , "brian.starkey@arm.com" List-ID: T24gVHVlLCAyMDE2LTA4LTIzIGF0IDE1OjMyIC0wNzAwLCBEYW4gV2lsbGlhbXMgd3JvdGU6DQo+ IE9uIFR1ZSwgQXVnIDIzLCAyMDE2IGF0IDExOjQzIEFNLCBUb3NoaSBLYW5pIDx0b3NoaS5rYW5p QGhwZS5jb20+DQo+IHdyb3RlOg0KwqA6DQo+IEknbSBub3Qgc3VyZSBhYm91dCB0aGlzIGZpeC7C oMKgVGhlIHBvaW50IG9mIGhvbm9yaW5nwqANCj4gdm1lbV9hbHRtYXBfb2Zmc2V0KCkgaXMgYmVj YXVzZSBhIHBvcnRpb24gb2YgdGhlIHJlc291cmNlIHRoYXQgaXMNCj4gcGFzc2VkIHRvIGRldm1f bWVtcmVtYXBfcGFnZXMoKSBhbHNvIGNvbnRhaW5zIHRoZSBtZXRhZGF0YSBpbmZvIGJsb2NrDQo+ IGZvciB0aGUgZGV2aWNlLsKgwqBUaGUgb2Zmc2V0IHNheXMgInVzZSBldmVyeXRoaW5nIHBhc3Qg dGhpcyBwb2ludCBmb3INCj4gcGFnZXMiLsKgwqBUaGlzIG1heSB3b3JrIGZvciBhdm9pZGluZyBh IGNyYXNoLCBidXQgaXQgbWF5IGNvcnJ1cHQgaW5mbw0KPiBibG9jayBtZXRhZGF0YSBpbiB0aGUg cHJvY2Vzcy7CoMKgQ2FuIHlvdSBwcm92aWRlIG1vcmUgaW5mb3JtYXRpb24NCj4gYWJvdXQgdGhl 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SFV:NSPM;SFS:(10019020)(6009001)(7916002)(189002)(24454002)(199003)(377424004)(377454003)(6116002)(66066001)(8676002)(36756003)(122556002)(81166006)(81156014)(3660700001)(68736007)(97736004)(2501003)(99286002)(3280700002)(54356999)(50986999)(8936002)(76176999)(92566002)(11100500001)(7736002)(2900100001)(105586002)(10400500002)(4326007)(106116001)(101416001)(5002640100001)(2906002)(305945005)(2950100001)(77096005)(103116003)(110136002)(189998001)(2351001)(33646002)(7846002)(19580405001)(3846002)(5660300001)(87936001)(19580395003)(5640700001)(586003)(102836003)(86362001)(106356001);DIR:OUT;SFP:1102;SCL:1;SRVR:CS1PR84MB0053;H:CS1PR84MB0005.NAMPRD84.PROD.OUTLOOK.COM;FPR:;SPF:None;PTR:InfoNoRecords;MX:1;A:1;LANG:en; spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="utf-8" Content-ID: <4E67E24F580E834DB5BFC47721541CF6@NAMPRD84.PROD.OUTLOOK.COM> MIME-Version: 1.0 X-OriginatorOrg: hpe.com X-MS-Exchange-CrossTenant-originalarrivaltime: 23 Aug 2016 23:47:39.3616 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 105b2061-b669-4b31-92ac-24d304d195dc X-MS-Exchange-Transport-CrossTenantHeadersStamped: CS1PR84MB0053 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id u7O03fZa026709 On Tue, 2016-08-23 at 15:32 -0700, Dan Williams wrote: > On Tue, Aug 23, 2016 at 11:43 AM, Toshi Kani > wrote:  : > I'm not sure about this fix.  The point of honoring  > vmem_altmap_offset() is because a portion of the resource that is > passed to devm_memremap_pages() also contains the metadata info block > for the device.  The offset says "use everything past this point for > pages".  This may work for avoiding a crash, but it may corrupt info > block metadata in the process.  Can you provide more information > about the failing scenario to be sure that we are not triggering a > fault on an address that is not meant to have a page mapping?  I.e. > what is the host physical address of the page that caused this fault, > and is it valid? The fault address in question was the 2nd page of an NVDIMM range.  I assumed this fault address was valid and needed to be handled.  Here is some info about the base and patched cases.  Let me know if you need more info. Base ==== The following NVDIMM range was set to /dev/dax. /proc/iomem 480000000-87fffffff : Persistent Memory devm_memremap_pages() initialized struct page from 0x490200-0x87ffff. This left 0x48000-0x4901ff uninitialized for page->pgmap.  devm_memremap_pages: pgmap 0xffff88046d0453f0  [0]  : pfn 0x490200, page ffffea0012408000, pgmap ffff88046d0453f0  [1]  : pfn 0x490201, page ffffea0012408040, pgmap ffff88046d0453f0  [2]  : pfn 0x490202, page ffffea0012408080, pgmap ffff88046d0453f0  [3]  : pfn 0x490203, page ffffea00124080c0, pgmap ffff88046d0453f0  [4]  : pfn 0x490204, page ffffea0012408100, pgmap ffff88046d0453f0   :  [E+1]: pfn 0x880000, page ffffea0021ffffc0, pgmap ffff88046d0453f0 The faulted page was pfn 0x480001, which was the 2nd page in the NVDIMM range and did not have valid pgmap.  This led the BUG.  pfn              0x480001  page             0xffffea0012000040  page->pgmap      0xffffea0012000060  page->pgmap->ref (null) Patch ===== With the patch, devm_memremap_pages() initializes as follows.  devm_memremap_pages: pgmap ffff880462b3b4b0  [0]  : pfn 0x480000, page ffffea0012000000, pgmap ffff880462b3b4b0  [1]  : pfn 0x480001, page ffffea0012000040, pgmap ffff880462b3b4b0  [2]  : pfn 0x480002, page ffffea0012000080, pgmap ffff880462b3b4b0  [3]  : pfn 0x480003, page ffffea00120000c0, pgmap ffff880462b3b4b0  [4]  : pfn 0x480004, page ffffea0012000100, pgmap ffff880462b3b4b0   :  [E+1]: pfn 0x880000, page ffffea0021ffffc0, pgmap ffff880462b3b4b0 A page fault to pfn 0x480001 is handled as it has valid pgmap.  pfn              0x480001  page             0xffffea0012000040  page->pgmap      0xffff880462b3b4b0  page->pgmap->ref 0xffff880462b3b530 Its dev_pagemap and vmem_altmap are as follows. crash> p {struct dev_pagemap} 0xffff880462b3b4b0 $2 = {   altmap = 0xffff880462b3b4d0,   res = 0xffff880462b3b468,   ref = 0xffff880462b3b530,   dev = 0xffff880463e37010 } crash> p {struct vmem_altmap} 0xffff880462b3b4d0 $3 = {   base_pfn = 0x480000,   reserve = 0x2,   free = 0x101fe,   align = 0x1fe,   alloc = 0x10000 } This page entry is physically located at 0x480200040. crash> vtop 0xffffea0012000040 VIRTUAL           PHYSICAL ffffea0012000040  480200040 PML4 DIRECTORY: ffffffff81c06000 PAGE DIRECTORY: 47ffe6067    PUD: 47ffe6000 => 47ffe5067    PMD: 47ffe5480 => 80000004802001e3   PAGE: 480200000  (2MB)       PTE         PHYSICAL   FLAGS 80000004802001e3  480200000  (PRESENT|RW|ACCESSED|DIRTY|PSE|GLOBAL|NX)       PAGE        PHYSICAL      MAPPING       INDEX CNT FLAGS ffffea0012008000 480200000                0        0  1 4fffe000000400 reserved Thanks, -Toshi