From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AED09C433E1 for ; Fri, 15 May 2020 22:15:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 847B420756 for ; Fri, 15 May 2020 22:15:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="wgYl/oLl" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726212AbgEOWPt (ORCPT ); Fri, 15 May 2020 18:15:49 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:36588 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726183AbgEOWPs (ORCPT ); Fri, 15 May 2020 18:15:48 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 04FMBnZM029431; Fri, 15 May 2020 22:15:40 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : from : to : cc : references : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=2kGRzsjaRGAXe1KvMIuG2Z2gwGj3Jnd8bvP3/TCsvXU=; b=wgYl/oLleBEBHiZhkcCodEzbVKC/Otg3zgV3+oHjt3VUQ+Q1u6k3vdeA3pg0yl9ZSKU8 GeZ0feNYYp6T01DDM7+NAHf6u8PjUbyoYUi2LL5pJsyzTKldX9EPRs+IX2I9VeHowq6k OCFWd0gT8FwS1JRn6IdNPrwSecJU8ChgN8qDcxC6Q28Y0S2VpwLMDUfzWOCn5MomRdBe rQrspoj3gK5H8ypDU4OsCvgg7kMrjxqzh6OLapzvOHAeJ6NUF/I2XTHKgqKrmIa41Rnc Pbw/4dd5N6RRo+n4dtsrdC/oARZoeBqljrnlUam9Jm3qtzOXPiyAMx638vDXCLdNW23/ Rg== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2120.oracle.com with ESMTP id 3100xwx2vh-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 15 May 2020 22:15:40 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 04FMCpqE165873; Fri, 15 May 2020 22:15:39 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by userp3020.oracle.com with ESMTP id 3100ysb9jq-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 15 May 2020 22:15:39 +0000 Received: from abhmp0007.oracle.com (abhmp0007.oracle.com [141.146.116.13]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 04FMFaqC003865; Fri, 15 May 2020 22:15:37 GMT Received: from [192.168.2.157] (/50.38.34.50) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 15 May 2020 15:15:36 -0700 Subject: Re: kernel BUG at mm/hugetlb.c:LINE! From: Mike Kravetz To: Miklos Szeredi Cc: syzbot , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Miklos Szeredi , syzkaller-bugs , Al Viro References: <000000000000b4684e05a2968ca6@google.com> Message-ID: <86c504b3-52c9-55f6-13db-ab55b2f6980e@oracle.com> Date: Fri, 15 May 2020 15:15:35 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9622 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 adultscore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 suspectscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005150186 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9622 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 lowpriorityscore=0 suspectscore=0 mlxlogscore=999 clxscore=1015 cotscore=-2147483648 mlxscore=0 phishscore=0 adultscore=0 impostorscore=0 bulkscore=0 malwarescore=0 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005150186 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 5/12/20 11:11 AM, Mike Kravetz wrote: > On 5/12/20 8:04 AM, Miklos Szeredi wrote: >> On Tue, Apr 7, 2020 at 12:06 AM Mike Kravetz wrote: >>> On 4/5/20 8:06 PM, syzbot wrote: >>> >>> The routine is_file_hugepages() is just comparing the file ops to huegtlbfs: >>> >>> if (file->f_op == &hugetlbfs_file_operations) >>> return true; >>> >>> Since the file is in an overlayfs, file->f_op == ovl_file_operations. >>> Therefore, length will not be rounded up to huge page size and we create a >>> mapping with incorrect size which leads to the BUG. >>> >>> Because of the code in mmap, the hugetlbfs mmap() routine assumes length is >>> rounded to a huge page size. I can easily add a check to hugetlbfs mmap >>> to validate length and return -EINVAL. However, I think we really want to >>> do the 'round up' earlier in mmap. This is because the man page says: >>> >>> Huge page (Huge TLB) mappings >>> For mappings that employ huge pages, the requirements for the arguments >>> of mmap() and munmap() differ somewhat from the requirements for map‐ >>> pings that use the native system page size. >>> >>> For mmap(), offset must be a multiple of the underlying huge page size. >>> The system automatically aligns length to be a multiple of the underly‐ >>> ing huge page size. >>> >>> Since the location for the mapping is chosen BEFORE getting to the hugetlbfs >>> mmap routine, we can not wait until then to round up the length. Is there a >>> defined way to go from a struct file * to the underlying filesystem so we >>> can continue to do the 'round up' in early mmap code? >> >> That's easy enough: >> >> static inline struct file *real_file(struct file *file) >> { >> return file->f_op != ovl_file_operations ? file : file->private_data; >> } >> >> But adding more filesystem specific code to generic code does not >> sound like the cleanest way to solve this... > > We can incorporate the above 'real_file' functionality in the filesystem > specific routine is_file_hugepages(), and I think that would address this > specific issue. I'll code that up. > >>> One other thing I noticed with overlayfs is that it does not contain a >>> specific get_unmapped_area file_operations routine. I would expect it to at >>> least check for and use the get_unmapped_area of the underlying filesystem? >>> Can someone comment if this is by design? >> >> Not sure. What exactly is f_op->get_unmapped_area supposed to do? >> > > IIUC, filesystems can define their own routines to get addresses for mmap > operations. Quite a few filesystems define get_unmapped_area. > > The generic mmap code does the following, > > get_area = current->mm->get_unmapped_area; > if (file) { > if (file->f_op->get_unmapped_area) > get_area = file->f_op->get_unmapped_area; > } else if (flags & MAP_SHARED) { > /* > * mmap_region() will call shmem_zero_setup() to create a file, > * so use shmem's get_unmapped_area in case it can be huge. > * do_mmap_pgoff() will clear pgoff, so match alignment. > */ > pgoff = 0; > get_area = shmem_get_unmapped_area; > } > > addr = get_area(file, addr, len, pgoff, flags); > > If the filesystem provides a get_unmapped_area, it will use it. I beleive > overlayfs prevents this from happening for the underlying filesystem. > > Perhaps we do need to add something like a call 'real_file' to this generic > code? I can't think of any other way to get to the underlying filesystem > get_unmapped_area here. I started going down the path of creating a get_unmapped_area f_op for overlayfs. That is pretty straight forward and works well. But that did not take care of the is_file_hugepages() routine. Recall that is_file_hugepages simply does if (file->f_op == &hugetlbfs_file_operations). I suppose I could add a specific overlayfs check like real_file here. But, that does not seem like a clean solution. I also discovered other routines doing comparisons like if (file->f_op == ), they are: is_dma_buf_file() is_file_shm_hugepages() get_pipe_info() is_file_epoll() So, it seems that these routines are also impacted if operating on files in an overlayfs? Any suggestions on how to move forward? It seems like there may be the need for a real_file() routine? I see a d_real dentry_op was added to deal with this issue for dentries. Might we need something similiar for files (f_real)? Looking for suggestions as I do not normally work with this code. -- Mike Kravetz