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Wed, 22 Sep 2021 08:25:00 +0000 Subject: Re: [PATCH v3] ovl: fix null pointer when filesystem doesn't support direct IO To: Chengguang Xu , linux-unionfs@vger.kernel.org, miklos@szeredi.hu, linux-erofs@lists.ozlabs.org, xiang@kernel.org, chao@kernel.org Cc: guoweichao@oppo.com, yh@oppo.com, zhangshiming@oppo.com, guanyuwei@oppo.com, jnhuang95@gmail.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <9ef909de-1854-b4be-d272-2b4cda52329f@oppo.com> <20210922072326.3538-1-huangjianan@oppo.com> From: Huang Jianan Message-ID: <919e929d-6af7-b729-9fd2-954cd1e52999@oppo.com> Date: Wed, 22 Sep 2021 16:24:56 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: HK2PR04CA0080.apcprd04.prod.outlook.com (2603:1096:202:15::24) To SG2PR02MB4108.apcprd02.prod.outlook.com (2603:1096:4:96::19) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from [10.118.7.229] (58.255.79.105) by HK2PR04CA0080.apcprd04.prod.outlook.com (2603:1096:202:15::24) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4544.13 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?dHRISVZLK3VDYWEwOUk3clpUem0xYzJ2bjJCeTNZMWVyeU5wZFBwUWdGdHBm?= =?utf-8?B?ekV4MGVhdFNxWnYvM2VHMXNLOERZZ05NSFNsdjBHTDk2MVYrejV6dmwyc2hP?= =?utf-8?B?eHpWREdteHlhWjQ3WVVOdWZxbXNYQjBscGZiUS9ISlNuc3o4U1ZMLzRLU1Fz?= =?utf-8?B?ZkYwdW9hL1R5N2pXZ2cxbVNyTzVkTFlaUDMzM0Z3andRTWhnSTU0Y3paY25Y?= =?utf-8?B?RHlOR21XZ09QS2JSczN5Wk9yM1NvYkFRc2FKM2pQdUE1dmoxR2VsdjFuNEM1?= =?utf-8?B?VDhMT1c4RlpEK01hSjI1SVpUWVRDc2QwMWFUdVdxQk9LSDZuZWptd002d2Ft?= =?utf-8?B?VldMWmEyTTVnK21BU0VnOEFlMytWbGpxaXFRRTlEc0h0ZE9rYVNxZ1F5cFlh?= =?utf-8?B?MmZpRUhXZllMMUNydFRoNngzckoxMzgvTFg0VEpQcjYvQzAycVd5OW5iMjBN?= =?utf-8?B?Y21vU3BPOEhaQzhoK0dHRVZpSGtiTExDRDRBMzZHa3hIUHRKTmxBZ1VJWGQy?= =?utf-8?B?UlhqZDVNbVJoSnVLTEZsMWhiMFB4U1kvRTJHOStoL084NzNtc3hUT05ReFEx?= =?utf-8?B?WkFaWG1iK0RYL1FDUEIrSGo1N2xxaUlLajk0OVBVTlJCVEV3K0kzdjBZTWtY?= =?utf-8?B?Mjk3MVg0cTVGRFhYZnhaTnF6Z2RTaCt3SEVpT0tJM3ZqSUNsZWp2SVBhaVl0?= =?utf-8?B?bGNxTXRQZitNK2JLZklYOWl0U0xYRDR5bHVSN29KOWFVemMxUDJWOC9sSjV0?= =?utf-8?B?NGpvT2FtSTczTzFtRWo3RjNJV2xpSTl0RllPbXFjRXlSMlNXL0pzYnptQUdB?= =?utf-8?B?bjVCNHoyeExRZFl0OUhvNHc0WHNveldVQTFtTDZDNzB2WlJaZXdZdDhpTnNL?= =?utf-8?B?dmxWWDE5VHZIeGorYm0ybWFRT09YYWN4UzdBUFNYaFpmSlBqdkdodzQ4TCsz?= =?utf-8?B?R0t0TEhtQVpEWk00KzhoVkcyVENaWWlyVWtZVmt2NFRzTnROWkdZMFBiZzlN?= =?utf-8?B?SHNxVXQzVVIyU3pITXoxRWYvSStVRTYyckczdUl0bkFya2xFUDZjVHo1cnZu?= =?utf-8?B?bllmYW9FcHNkbDVUaVdwSmN6OEFGSENQWWxNR2ZrMTNxL21KZGFhemJKd29W?= =?utf-8?B?Q3RkM00zR2xiTnZ3M1lWR3oxb1JKU1U1bHVrR0cxT01DbGUxcVRwa2xHZWxE?= =?utf-8?B?RHBRSHZka0xBWWthZnNRWkt5RjdSRXYwZGRyU1pmVEU0M2JpUUxCaHQzMWQy?= =?utf-8?B?MEk5c1F3VnRjY0NFVXRIY0h6T0NRVGhZbGF0L3NVTWpGaUdzRzdmb1RDeW0r?= =?utf-8?B?Qy9xcFpwWXgrQjZ3aHZpNlVmOXE0cmVVK3dqTmY0R29RS3I3UDVMM2J4QTJI?= =?utf-8?B?QWg5K08rM3J3b0Z4QzN4bUkvWUwzYlpPcFRObUg3ZzlmOExnc0pEM1JDOU55?= =?utf-8?B?bDBMN2NSaVFOMHVIVmwyWGJKckl3eG1sMTg2ekI2Y24vV25Vc0RrWUlpMVVJ?= =?utf-8?B?aDU1MXlrOXFLdzJzY3p0VEZNODlLTGxnM1RvdW9pZkR6ZmZwUnJ5WTFjTGlK?= =?utf-8?B?Zy9EbkZIME5KYUZtQkw2NXBIVWJyTVBvdjRETFdTS0o1NjNpNzF0MCtMSkI4?= =?utf-8?B?a0xpOEdYTHkrR1VoQmlFNVgyK0NnZkJQaWlVTFpVeWp6dkJBRmkySFdLOTdL?= =?utf-8?B?a1E3OFdsZHBJOHBNVCt4UFBmQytjdS9zNmQrbmI0aHluR0hobm82ZldEa25R?= =?utf-8?Q?h8c2zJ0ho+SD7f7vHQ1IKHDKD72ds5M2cA9cfzf?= X-OriginatorOrg: oppo.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2697be2a-a0b2-46ed-5004-08d97da27785 X-MS-Exchange-CrossTenant-AuthSource: SG2PR02MB4108.apcprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 22 Sep 2021 08:25:00.1200 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: f1905eb1-c353-41c5-9516-62b4a54b5ee6 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: WYrDVhGtI8/7dKatXCEwacqVNp3fdxkvn/GBkJONVoeAol3qfYDKGoogYkGNQjBctSKV3pHIgwzDs6w+4zkOHQ== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SG2PR02MB2860 Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org 在 2021/9/22 16:06, Chengguang Xu 写道: > 在 2021/9/22 15:23, Huang Jianan 写道: >> From: Huang Jianan >> >> At present, overlayfs provides overlayfs inode to users. Overlayfs >> inode provides ovl_aops with noop_direct_IO to avoid open failure >> with O_DIRECT. But some compressed filesystems, such as erofs and >> squashfs, don't support direct_IO. >> >> Users who use f_mapping->a_ops->direct_IO to check O_DIRECT support, >> will read file through this way. This will cause overlayfs to access >> a non-existent direct_IO function and cause panic due to null pointer: > > I just looked around the code more closely, in open_with_fake_path(), > > do_dentry_open() has already checked O_DIRECT open flag and > a_ops->direct_IO of underlying real address_space. > > Am I missing something? > > It seems that loop_update_dio will set lo->use_dio after open file without set O_DIRECT. loop_update_dio will check f_mapping->a_ops->direct_IO but it deal with ovl_aops with noop _direct_IO. So I think we still need a new aops? Thanks, Jianan > Thanks, > > Chengguang > > >> >> Kernel panic - not syncing: CFI failure (target: 0x0) >> CPU: 6 PID: 247 Comm: loop0 >> Call Trace: >>   panic+0x188/0x45c >>   __cfi_slowpath+0x0/0x254 >>   __cfi_slowpath+0x200/0x254 >>   generic_file_read_iter+0x14c/0x150 >>   vfs_iocb_iter_read+0xac/0x164 >>   ovl_read_iter+0x13c/0x2fc >>   lo_rw_aio+0x2bc/0x458 >>   loop_queue_work+0x4a4/0xbc0 >>   kthread_worker_fn+0xf8/0x1d0 >>   loop_kthread_worker_fn+0x24/0x38 >>   kthread+0x29c/0x310 >>   ret_from_fork+0x10/0x30 >> >> The filesystem may only support direct_IO for some file types. For >> example, erofs supports direct_IO for uncompressed files. So return >> -EINVAL when the file doesn't support direct_IO to fix this problem. >> >> Fixes: 5b910bd615ba ("ovl: fix GPF in swapfile_activate of file from >> overlayfs over xfs") >> Signed-off-by: Huang Jianan >> --- >> change since v2: >>   - Return error in ovl_open directly. (Chengguang Xu) >> >> Change since v1: >>   - Return error to user rather than fall back to buffered io. >> (Chengguang Xu) >> >>   fs/overlayfs/file.c | 4 ++++ >>   1 file changed, 4 insertions(+) >> >> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c >> index d081faa55e83..a0c99ea35daf 100644 >> --- a/fs/overlayfs/file.c >> +++ b/fs/overlayfs/file.c >> @@ -157,6 +157,10 @@ static int ovl_open(struct inode *inode, struct >> file *file) >>       if (IS_ERR(realfile)) >>           return PTR_ERR(realfile); >>   +    if ((f->f_flags & O_DIRECT) && (!realfile->f_mapping->a_ops || >> +        !realfile->f_mapping->a_ops->direct_IO)) >> +        return -EINVAL; >> + >>       file->private_data = realfile; >>         return 0; > 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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MSGID_FROM_MTA_HEADER,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,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 10B15C433EF for ; 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Overlayfs >> inode provides ovl_aops with noop_direct_IO to avoid open failure >> with O_DIRECT. But some compressed filesystems, such as erofs and >> squashfs, don't support direct_IO. >> >> Users who use f_mapping->a_ops->direct_IO to check O_DIRECT support, >> will read file through this way. This will cause overlayfs to access >> a non-existent direct_IO function and cause panic due to null pointer: > > I just looked around the code more closely, in open_with_fake_path(), > > do_dentry_open() has already checked O_DIRECT open flag and > a_ops->direct_IO of underlying real address_space. > > Am I missing something? > > It seems that loop_update_dio will set lo->use_dio after open file without set O_DIRECT. loop_update_dio will check f_mapping->a_ops->direct_IO but it deal with ovl_aops with noop _direct_IO. So I think we still need a new aops? Thanks, Jianan > Thanks, > > Chengguang > > >> >> Kernel panic - not syncing: CFI failure (target: 0x0) >> CPU: 6 PID: 247 Comm: loop0 >> Call Trace: >>   panic+0x188/0x45c >>   __cfi_slowpath+0x0/0x254 >>   __cfi_slowpath+0x200/0x254 >>   generic_file_read_iter+0x14c/0x150 >>   vfs_iocb_iter_read+0xac/0x164 >>   ovl_read_iter+0x13c/0x2fc >>   lo_rw_aio+0x2bc/0x458 >>   loop_queue_work+0x4a4/0xbc0 >>   kthread_worker_fn+0xf8/0x1d0 >>   loop_kthread_worker_fn+0x24/0x38 >>   kthread+0x29c/0x310 >>   ret_from_fork+0x10/0x30 >> >> The filesystem may only support direct_IO for some file types. For >> example, erofs supports direct_IO for uncompressed files. So return >> -EINVAL when the file doesn't support direct_IO to fix this problem. >> >> Fixes: 5b910bd615ba ("ovl: fix GPF in swapfile_activate of file from >> overlayfs over xfs") >> Signed-off-by: Huang Jianan >> --- >> change since v2: >>   - Return error in ovl_open directly. (Chengguang Xu) >> >> Change since v1: >>   - Return error to user rather than fall back to buffered io. >> (Chengguang Xu) >> >>   fs/overlayfs/file.c | 4 ++++ >>   1 file changed, 4 insertions(+) >> >> diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c >> index d081faa55e83..a0c99ea35daf 100644 >> --- a/fs/overlayfs/file.c >> +++ b/fs/overlayfs/file.c >> @@ -157,6 +157,10 @@ static int ovl_open(struct inode *inode, struct >> file *file) >>       if (IS_ERR(realfile)) >>           return PTR_ERR(realfile); >>   +    if ((f->f_flags & O_DIRECT) && (!realfile->f_mapping->a_ops || >> +        !realfile->f_mapping->a_ops->direct_IO)) >> +        return -EINVAL; >> + >>       file->private_data = realfile; >>         return 0; >