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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 CC59DC433EF for ; Sun, 19 Sep 2021 13:37:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A73CB6101C for ; Sun, 19 Sep 2021 13:37:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231304AbhISNjI (ORCPT ); Sun, 19 Sep 2021 09:39:08 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:55174 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230520AbhISNjI (ORCPT ); Sun, 19 Sep 2021 09:39:08 -0400 Received: from fsav415.sakura.ne.jp (fsav415.sakura.ne.jp [133.242.250.114]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id 18JDbYo5078668; Sun, 19 Sep 2021 22:37:35 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav415.sakura.ne.jp (F-Secure/fsigk_smtp/550/fsav415.sakura.ne.jp); Sun, 19 Sep 2021 22:37:34 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/fsav415.sakura.ne.jp) Received: from [192.168.1.9] (M106072142033.v4.enabler.ne.jp [106.72.142.33]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id 18JDbYEr078665 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NO); Sun, 19 Sep 2021 22:37:34 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Subject: Re: [syzbot] KASAN: use-after-free Read in bdev_free_inode To: syzbot , axboe@kernel.dk, linux-block@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <0000000000004a5adf05cc593ca9@google.com> From: Tetsuo Handa Message-ID: <41766564-08cb-e7f2-4cb2-9ad102f21324@I-love.SAKURA.ne.jp> Date: Sun, 19 Sep 2021 22:37:34 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: <0000000000004a5adf05cc593ca9@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This seems to be kfree() before RCU grace period. struct block_device *bdev_alloc(struct gendisk *disk, u8 partno) { struct block_device *bdev; struct inode *inode; inode = new_inode(blockdev_superblock); if (!inode) return NULL; inode->i_mode = S_IFBLK; inode->i_rdev = 0; inode->i_data.a_ops = &def_blk_aops; mapping_set_gfp_mask(&inode->i_data, GFP_USER); bdev = I_BDEV(inode); mutex_init(&bdev->bd_fsfreeze_mutex); spin_lock_init(&bdev->bd_size_lock); bdev->bd_disk = disk; // <= Assigns pointer to "disk". bdev->bd_partno = partno; bdev->bd_inode = inode; bdev->bd_stats = alloc_percpu(struct disk_stats); if (!bdev->bd_stats) { iput(inode); // <= Will call bdev_free_inode() via i_callback() after RCU from destroy_inode() from evict() from iput_final() from iput(). return NULL; } return bdev; } struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id, struct lock_class_key *lkclass) { struct gendisk *disk; if (!blk_get_queue(q)) return NULL; disk = kzalloc_node(sizeof(struct gendisk), GFP_KERNEL, node_id); if (!disk) goto out_put_queue; disk->bdi = bdi_alloc(node_id); if (!disk->bdi) goto out_free_disk; disk->part0 = bdev_alloc(disk, 0); if (!disk->part0) goto out_free_bdi; disk->node_id = node_id; mutex_init(&disk->open_mutex); xa_init(&disk->part_tbl); if (xa_insert(&disk->part_tbl, 0, disk->part0, GFP_KERNEL)) goto out_destroy_part_tbl; rand_initialize_disk(disk); disk_to_dev(disk)->class = &block_class; disk_to_dev(disk)->type = &disk_type; device_initialize(disk_to_dev(disk)); inc_diskseq(disk); disk->queue = q; q->disk = disk; lockdep_init_map(&disk->lockdep_map, "(bio completion)", lkclass, 0); #ifdef CONFIG_BLOCK_HOLDER_DEPRECATED INIT_LIST_HEAD(&disk->slave_bdevs); #endif return disk; out_destroy_part_tbl: xa_destroy(&disk->part_tbl); iput(disk->part0->bd_inode); // <= The same race problem exists? out_free_bdi: bdi_put(disk->bdi); out_free_disk: kfree(disk); // <= Releasing "disk" despite "disk->part0->bd_disk == disk" when bdev_free_inode() will dereference ->bd_disk after RCU. out_put_queue: blk_put_queue(q); return NULL; }