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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 16898C433E1 for ; Thu, 11 Jun 2020 00:14:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DAE3F207ED for ; Thu, 11 Jun 2020 00:14:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="D3iX9xrR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726924AbgFKAOO (ORCPT ); Wed, 10 Jun 2020 20:14:14 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:35046 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726820AbgFKAOO (ORCPT ); Wed, 10 Jun 2020 20:14:14 -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 05B0D4m3119079; Thu, 11 Jun 2020 00:13:58 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2020-01-29; bh=VSQ9eS7gkSGb0v4ligtQhmEu3fEZRdfYfrfA7KqdkF0=; b=D3iX9xrRX5rW/U7VEa6vX2dgh89GLylVg3Uk1+g203IjaylRs2i7LG8bwLZVUKojwOjt /AYoqERKgLbPzSnoUhgXH1bPqlBOoIXdOE2wnEXMvP49FYXRX+HNWfqqUbYLQl/z3Id5 mFQhAYL8S6XGPi3avU4HtmjS5Jix9UBz+pfz6erdgweq62iB/SyX3eB438X1+L56oWVj I9IDVnrgCdNx61VVygWLbJ2y3ACfGHXfTllk/Pmzx/aziGVNIgJWEZM3D6s0TAQfn2uA xmQ7h1qpv9gYspYBTQ18Xnt5Y2WiEXbe2O2airz2bDXLX0EKn48f8C/aqClr5UxLWGrD 0A== Received: from aserp3020.oracle.com (aserp3020.oracle.com [141.146.126.70]) by aserp2120.oracle.com with ESMTP id 31jepnxyag-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Thu, 11 Jun 2020 00:13:58 +0000 Received: from pps.filterd (aserp3020.oracle.com [127.0.0.1]) by aserp3020.oracle.com (8.16.0.42/8.16.0.42) with SMTP id 05B0CUSx056589; Thu, 11 Jun 2020 00:13:58 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3020.oracle.com with ESMTP id 31gn2af3py-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 11 Jun 2020 00:13:58 +0000 Received: from abhmp0016.oracle.com (abhmp0016.oracle.com [141.146.116.22]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 05B0DsrQ003884; Thu, 11 Jun 2020 00:13:55 GMT Received: from [192.168.2.112] (/50.38.35.18) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 10 Jun 2020 17:13:54 -0700 Subject: Re: [PATCH v2] ovl: provide real_file() and overlayfs get_unmapped_area() To: Miklos Szeredi Cc: kbuild test robot , kbuild-all@lists.01.org, Colin Walters , syzbot , Andrew Morton , Linux Memory Management List , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs , Al Viro , overlayfs References: <4ebd0429-f715-d523-4c09-43fa2c3bc338@oracle.com> <202005281652.QNakLkW3%lkp@intel.com> <365d83b8-3af7-2113-3a20-2aed51d9de91@oracle.com> From: Mike Kravetz Message-ID: Date: Wed, 10 Jun 2020 17:13:52 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9648 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 suspectscore=0 mlxscore=0 phishscore=0 adultscore=0 bulkscore=0 malwarescore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006100173 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9648 signatures=668680 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 lowpriorityscore=0 suspectscore=0 priorityscore=1501 bulkscore=0 clxscore=1015 phishscore=0 impostorscore=0 malwarescore=0 mlxscore=0 cotscore=-2147483648 adultscore=0 spamscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2006100173 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 6/4/20 2:16 AM, Miklos Szeredi wrote: > On Thu, May 28, 2020 at 11:01 PM Mike Kravetz wrote: >> >> Well yuck! get_unmapped_area is not part of mm_struct if !CONFIG_MMU. >> >> Miklos, would adding '#ifdef CONFIG_MMU' around the overlayfs code be too >> ugly for you? Another option is to use real_file() in the mmap code as >> done in [1]. > > I think the proper fix is to add an inline helper > (call_get_unmapped_area()?) in linux/mm.h, and make that work properly > for the NOMMU case as well. > I'm ignoring the above issue for now. There may be a more fundamental issue that I do not know how to solve without adding another memeber to file_operations. Why? In order to go from file -> realfile, one needs to do something like the code you provided. while (file->f_op == &ovl_file_operations) file = file->private_data; return file; The problem is that this needs to be called from core kernel code (is_file_hugepages in mmap). ovl_file_operations is obviously only defined in the overlayfs code. Since overlayfs can be built as a module, I do not know of a way to reference ovl_file_operations which will only become available when/if overlayfs is loaded. Is there a way to do that? If there is no other way to do this, then I think we need to add another member to file_operations as is done in the following patch. I hope there is another way, because adding another file_op seems like overkill. >From 6d22c93284263b5ddcc2199adc1bcceb233f1499 Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Wed, 10 Jun 2020 16:23:46 -0700 Subject: [PATCH v3] ovl: add f_real file_operation and supporting code for overlayfs If a file is on a union/overlay, then the 'struct file *' will have overlayfs file operations. The routine is_file_hugepages() compares f->f_op to hugetlbfs_file_operations to determine if it is a hugetlbfs file. If a hugetlbfs file is on a union/overlay, this comparison is false and is_file_hugepages() incorrectly indicates the underlying file is not hugetlbfs. One result of this is a BUG as shown in [1]. mmap uses is_file_hugepages() to identify hugetlbfs file and potentially round up length because hugetlbfs files have different alignment restrictions. This is defined/expected behavior. In addition, mmap code would like to use the filesystem specific get_unmapped_area() routine if one is defined. To address this issue, - Add a new file operation f_real while will return the underlying file. Only overlayfs provides a function for this operation. - Add a new routine real_file() which can be used by core code get an underlying file. - Update is_file_hugepages to get the real file. - Add get_unmapped_area f_op to oerrlayfs to call underlying routine. [1] https://lore.kernel.org/linux-mm/000000000000b4684e05a2968ca6@google.com/ Reported-by: syzbot+d6ec23007e951dadf3de@syzkaller.appspotmail.com Signed-off-by: Miklos Szeredi Signed-off-by: Mike Kravetz --- fs/overlayfs/file.c | 23 +++++++++++++++++++++++ include/linux/fs.h | 8 ++++++++ include/linux/hugetlb.h | 2 ++ 3 files changed, 33 insertions(+) diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index 87c362f65448..eb870fc3912f 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -757,6 +757,27 @@ static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in, remap_flags, op); } +#ifdef CONFIG_MMU +static unsigned long ovl_get_unmapped_area(struct file *file, + unsigned long uaddr, unsigned long len, + unsigned long pgoff, unsigned long flags) +{ + file = real_file(file); + + return (file->f_op->get_unmapped_area ?: + current->mm->get_unmapped_area)(file, uaddr, len, pgoff, flags); +} +#else +#define ovl_get_unmapped_area NULL +#endif + +static struct file *ovl_f_real(struct file *file) +{ + while (file->f_op == &ovl_file_operations) + file = file->private_data; + return file; +} + const struct file_operations ovl_file_operations = { .open = ovl_open, .release = ovl_release, @@ -771,9 +792,11 @@ const struct file_operations ovl_file_operations = { .compat_ioctl = ovl_compat_ioctl, .splice_read = ovl_splice_read, .splice_write = ovl_splice_write, + .f_real = ovl_f_real, .copy_file_range = ovl_copy_file_range, .remap_file_range = ovl_remap_file_range, + .get_unmapped_area = ovl_get_unmapped_area, }; int __init ovl_aio_request_cache_init(void) diff --git a/include/linux/fs.h b/include/linux/fs.h index 45cc10cdf6dd..59a969549aec 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1863,6 +1863,7 @@ struct file_operations { struct file *file_out, loff_t pos_out, loff_t len, unsigned int remap_flags); int (*fadvise)(struct file *, loff_t, loff_t, int); + struct file * (*f_real)(struct file *file); } __randomize_layout; struct inode_operations { @@ -1895,6 +1896,13 @@ struct inode_operations { int (*set_acl)(struct inode *, struct posix_acl *, int); } ____cacheline_aligned; +static inline struct file *real_file(struct file *file) +{ + if (unlikely(file->f_op->f_real)) + return file->f_op->f_real(file); + return file; +} + static inline ssize_t call_read_iter(struct file *file, struct kiocb *kio, struct iov_iter *iter) { diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 43a1cef8f0f1..528b07145414 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -437,6 +437,8 @@ struct file *hugetlb_file_setup(const char *name, size_t size, vm_flags_t acct, static inline bool is_file_hugepages(struct file *file) { + file = real_file(file); + if (file->f_op == &hugetlbfs_file_operations) return true; -- 2.25.4