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Sat, 18 Sep 2021 12:13:55 +0000 From: Huang Jianan To: linux-unionfs@vger.kernel.org, miklos@szeredi.hu, linux-erofs@lists.ozlabs.org, xiang@kernel.org, chao@kernel.org Cc: huangjianan@oppo.com, guoweichao@oppo.com, yh@oppo.com, zhangshiming@oppo.com, guanyuwei@oppo.com, jnhuang95@gmail.com, linux-kernel@vger.kernel.org Subject: [PATCH] ovl: fix null pointer when filesystem doesn't support direct IO Date: Sat, 18 Sep 2021 20:13:46 +0800 Message-Id: <20210918121346.12084-1-huangjianan@oppo.com> X-Mailer: git-send-email 2.25.1 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: HK2PR04CA0050.apcprd04.prod.outlook.com (2603:1096:202:14::18) To SG2PR02MB4108.apcprd02.prod.outlook.com (2603:1096:4:96::19) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from PC80253450.adc.com (58.252.5.73) by HK2PR04CA0050.apcprd04.prod.outlook.com (2603:1096:202:14::18) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4523.14 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?tO5qu+ZUo0sfh90uxAKQxZJ1tn84Qm40nSrADFubdrYsL9nVvuVhCHi/Wg0r?= =?us-ascii?Q?VG9MYoyfmUc//KqQks3U4JeiaJRbE9PtbbPkjmBF4OWxF0fOf7oW65A0ATQh?= =?us-ascii?Q?TTiRNPekShxlKoLlAFZ7QL/Tt5Pkv27pRBOVlaj4VRAcBaZQyzMUXL3IDsyO?= =?us-ascii?Q?n259DTum1NF6OeGuuKcbqh4+uCXsPtwUDG7Pl3JZQz7BXDOuFu8XUw79LK1G?= =?us-ascii?Q?A+R2kBZxauG4Tf1zrkU9gvWi9RmaEOWrvTOLcOHcKajB4jKeZER8G2UmQYbn?= =?us-ascii?Q?wuIuXHcytuWq4YNb0yHJk3sttEu3/vwzSTxH56auK6czRBnMVl09NVGf9bqV?= =?us-ascii?Q?C6Q4ZPkVw9yJY5jibKWfPGmWkpHGZuPHz27Rn3RibqEh2Fax5cPLUF8LGATs?= =?us-ascii?Q?mYMaDk2CXs64Tv04PQVwwPAN+nEvSrWuYx80KH9fXvaHXyN0GGSDquwfpVTi?= =?us-ascii?Q?Lvk/cVzmbi8XG9ZBlINlfPI40eHo0pHhZRmalJMswUuT3gSZoTzDzi1d9KhP?= =?us-ascii?Q?On8j1p9H4OGZ8rHc4hBthALCTNGD1Wcf9sFPc5y5KIIn19mr0ea9Iwzjb8JG?= =?us-ascii?Q?01GZLrsv/SoOkkRx20rRkI0w8f2xhgrS6dgJP323YQ8iUBKN+6o/4nztcyDe?= =?us-ascii?Q?YWsHZ3c28o8TwtR6JIYSIStiXDRBD1vDI+ZnAmJrte0llE+MdGa4NhTxHTez?= =?us-ascii?Q?MPRK60wLogPB3nz78QG7L9WXRq8JvOVG1SzrIRfq1kMt9fPKiUpPn/P+wKvj?= =?us-ascii?Q?7mb1+r2yVbCPDvU8QKXu5bvvzTGY+29bhP2EW6Q/Ve4WTSTCeU4oECvxdjCW?= =?us-ascii?Q?8jBc/MkXUEUaFv6pL8PVW3UyoYxvvUFIWSqWdz8zl+tVEm0WhFlgdW4vueD/?= =?us-ascii?Q?B3CY0rm6i2tM9m0wXNYsEFrEjob0UWslCj6zOZgjDNbP3mTTzChq6Art5QA7?= =?us-ascii?Q?cAsCqlYsSc/RSJ8ME08ybGY9goXLvX0PAkGYXbDNc4e2ttzs5MAFfziK7gPQ?= =?us-ascii?Q?65dOmtNWPc0R0zln/4wNdlWXilfU1EPTO06fIUmDYt/q/gNA4JPHJfpPNVf9?= =?us-ascii?Q?PKbnO8HKxxrqRurrg4LwBt5DRVevC0pARglD3DpM1oI8HBs7RW/uerO9xDKQ?= =?us-ascii?Q?tqgH67i/pipcBAOgSOGK3+xQBpLv9XTez+HaBTkl2pBOc8xXEg7bvWGOjj2R?= =?us-ascii?Q?mMSCyYaPZph1O7jLeAJZYMUgTC2xqTnI+wrFSrfNfzhXLBVoIhXJjNBIE9Dl?= =?us-ascii?Q?fq6SIWERZfE14NBSY++zG2Qcso9sXfUixM0KpOXfowowYt2+DAMp7ZgZQ5km?= =?us-ascii?Q?fSXL8KKPETOiR5TcIckGbbQG?= X-OriginatorOrg: oppo.com X-MS-Exchange-CrossTenant-Network-Message-Id: d2adc654-6f73-4144-ea0a-08d97a9dc901 X-MS-Exchange-CrossTenant-AuthSource: SG2PR02MB4108.apcprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Sep 2021 12:13:55.3903 (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: 14mGS0BO90najrx2XVdURIig9AL9k64T2vrY+ATfocleiGGAtplQVz0Vqe5y8ZN0NUAuBpx0Jb3Hf0aLl5nb6Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SG2PR02MB2558 Precedence: bulk List-ID: X-Mailing-List: linux-unionfs@vger.kernel.org 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: 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 fall back to buffered io only 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 --- fs/overlayfs/file.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index d081faa55e83..998c60770b81 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -296,6 +296,10 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter) if (ret) return ret; + if ((iocb->ki_flags & IOCB_DIRECT) && (!real.file->f_mapping->a_ops || + !real.file->f_mapping->a_ops->direct_IO)) + iocb->ki_flags &= ~IOCB_DIRECT; + old_cred = ovl_override_creds(file_inode(file)->i_sb); if (is_sync_kiocb(iocb)) { ret = vfs_iter_read(real.file, iter, &iocb->ki_pos, -- 2.25.1 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=-18.7 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,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT 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 1B916C433F5 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: 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 fall back to buffered io only 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 --- fs/overlayfs/file.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c index d081faa55e83..998c60770b81 100644 --- a/fs/overlayfs/file.c +++ b/fs/overlayfs/file.c @@ -296,6 +296,10 @@ static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter) if (ret) return ret; + if ((iocb->ki_flags & IOCB_DIRECT) && (!real.file->f_mapping->a_ops || + !real.file->f_mapping->a_ops->direct_IO)) + iocb->ki_flags &= ~IOCB_DIRECT; + old_cred = ovl_override_creds(file_inode(file)->i_sb); if (is_sync_kiocb(iocb)) { ret = vfs_iter_read(real.file, iter, &iocb->ki_pos, -- 2.25.1