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=-3.7 required=3.0 tests=BAYES_00,FROM_LOCAL_HEX, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 18E66C432BE for ; Fri, 30 Jul 2021 08:28:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED6C760F0F for ; Fri, 30 Jul 2021 08:28:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238042AbhG3I22 (ORCPT ); Fri, 30 Jul 2021 04:28:28 -0400 Received: from mail-il1-f197.google.com ([209.85.166.197]:48737 "EHLO mail-il1-f197.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237956AbhG3I2V (ORCPT ); Fri, 30 Jul 2021 04:28:21 -0400 Received: by mail-il1-f197.google.com with SMTP id p6-20020a056e021446b0290205af2e2342so4624029ilo.15 for ; Fri, 30 Jul 2021 01:28:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:date:in-reply-to:message-id:subject :from:to; bh=GISeRZqB/e3Oljoo9ObPCdPOxhxBhMkqAwYWd8XUGME=; b=J4YztPKgvd+fNumuKi9K1SYQH486ubKFj369KBtrbe1/mvi3c6hOiR0kF+3ZPyMjUC h8eyVdIl1ZD0FOGbGmFGN1WUQBphNJRBdoj+mo0OXn3+W7dizMm6iJiqKoFiNl2cis4R MtpyJjqHJNokWjwfHN3jJronx7TucyiohgFTUTq5mEGKFV8Qj/c6U9wCK6HpY/aL8bln XO8l8e70KHVCvugBaZerPicYIHVuCWK+dbgbY+iRv8SEWAdaOf/+P2wPn+qIJns9CTa9 CAEGgs+9/jU8nmX38N8ysknGavxdzu95wHFq7adOp96SRcTPvMKnThsaiZPJdEWJO00c KNfA== X-Gm-Message-State: AOAM533/fky/c+1qqxCTOsyS5BBGDZ+3Attx7q74cfUmpTYuH3x6RE/x nI8ljnnI9WIziUASVwJxh4Benm5zejJOPYHJ9BeXjB95R2OB X-Google-Smtp-Source: ABdhPJzzjWCRaOM7xD8AfBtQ/XRWqmHCiFjnQk+DT8rgvtzJ38XwWm2r0bULYRZWLY5piamtdzOnQAW+3fef5RiKOzQXmIOvrq59 MIME-Version: 1.0 X-Received: by 2002:a05:6602:2424:: with SMTP id g4mr722705iob.189.1627633697367; Fri, 30 Jul 2021 01:28:17 -0700 (PDT) Date: Fri, 30 Jul 2021 01:28:17 -0700 In-Reply-To: <000000000000458e0c05c6928ee2@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <0000000000005b27b805c853007b@google.com> Subject: Re: [syzbot] possible deadlock in __loop_clr_fd (2) From: syzbot To: axboe@kernel.dk, hdanton@sina.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org syzbot has found a reproducer for the following issue on: HEAD commit: 4ccc9e2db7ac Add linux-next specific files for 20210729 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=169b8d7a300000 kernel config: https://syzkaller.appspot.com/x/.config?x=75a5bed89b5c0fd2 dashboard link: https://syzkaller.appspot.com/bug?extid=f61766d5763f9e7a118f compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12b87a8e300000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13d20adc300000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+f61766d5763f9e7a118f@syzkaller.appspotmail.com loop0: detected capacity change from 0 to 4096 EXT4-fs error (device loop0): ext4_fill_super:4953: inode #2: comm syz-executor258: iget: root inode unallocated EXT4-fs (loop0): get root inode failed EXT4-fs (loop0): mount failed ====================================================== WARNING: possible circular locking dependency detected 5.14.0-rc3-next-20210729-syzkaller #0 Not tainted ------------------------------------------------------ syz-executor258/6697 is trying to acquire lock: ffff88807dbec138 ((wq_completion)loop0){+.+.}-{0:0}, at: flush_workqueue+0xe1/0x1600 kernel/workqueue.c:2784 but task is already holding lock: ffff88801d535468 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0xaf/0x15e0 drivers/block/loop.c:1350 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #6 (&lo->lo_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:957 [inline] __mutex_lock+0x131/0x1300 kernel/locking/mutex.c:1096 loop_control_remove drivers/block/loop.c:2449 [inline] loop_control_ioctl+0x22f/0x450 drivers/block/loop.c:2494 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:866 [inline] __se_sys_ioctl fs/ioctl.c:852 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:852 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #5 (loop_ctl_mutex){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:957 [inline] __mutex_lock+0x131/0x1300 kernel/locking/mutex.c:1096 loop_add+0x9c/0x940 drivers/block/loop.c:2314 loop_probe+0x6a/0x80 drivers/block/loop.c:2426 blk_request_module+0x111/0x1d0 block/genhd.c:673 blkdev_get_no_open+0x178/0x1e0 fs/block_dev.c:1298 blkdev_get_by_dev.part.0+0x23/0xd40 fs/block_dev.c:1362 blkdev_get_by_dev fs/block_dev.c:1471 [inline] blkdev_open+0x295/0x300 fs/block_dev.c:1477 do_dentry_open+0x4c8/0x11d0 fs/open.c:826 do_open fs/namei.c:3374 [inline] path_openat+0x1c23/0x27f0 fs/namei.c:3507 do_filp_open+0x1aa/0x400 fs/namei.c:3534 do_sys_openat2+0x16d/0x420 fs/open.c:1204 do_sys_open fs/open.c:1220 [inline] __do_sys_open fs/open.c:1228 [inline] __se_sys_open fs/open.c:1224 [inline] __x64_sys_open+0x119/0x1c0 fs/open.c:1224 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #4 (major_names_lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:957 [inline] __mutex_lock+0x131/0x1300 kernel/locking/mutex.c:1096 blkdev_show+0x27/0x160 block/genhd.c:197 devinfo_show+0xc1/0xf0 fs/proc/devices.c:22 seq_read_iter+0xbb0/0x1240 fs/seq_file.c:272 proc_reg_read_iter+0x1fb/0x2d0 fs/proc/inode.c:300 call_read_iter include/linux/fs.h:2146 [inline] new_sync_read+0x41e/0x6e0 fs/read_write.c:415 vfs_read+0x35c/0x570 fs/read_write.c:496 ksys_read+0x12d/0x250 fs/read_write.c:634 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #3 (&p->lock){+.+.}-{3:3}: __mutex_lock_common kernel/locking/mutex.c:957 [inline] __mutex_lock+0x131/0x1300 kernel/locking/mutex.c:1096 seq_read_iter+0xdf/0x1240 fs/seq_file.c:182 call_read_iter include/linux/fs.h:2146 [inline] generic_file_splice_read+0x450/0x6c0 fs/splice.c:311 do_splice_to+0x1bf/0x250 fs/splice.c:796 splice_direct_to_actor+0x2c2/0x8c0 fs/splice.c:870 do_splice_direct+0x1b3/0x280 fs/splice.c:979 do_sendfile+0x9f0/0x1120 fs/read_write.c:1260 __do_sys_sendfile64 fs/read_write.c:1325 [inline] __se_sys_sendfile64 fs/read_write.c:1311 [inline] __x64_sys_sendfile64+0x1cc/0x210 fs/read_write.c:1311 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae -> #2 (sb_writers#3){.+.+}-{0:0}: percpu_down_read include/linux/percpu-rwsem.h:51 [inline] __sb_start_write include/linux/fs.h:1801 [inline] sb_start_write include/linux/fs.h:1871 [inline] file_start_write include/linux/fs.h:3080 [inline] lo_write_bvec+0x3b6/0x6d0 drivers/block/loop.c:327 lo_write_simple drivers/block/loop.c:350 [inline] do_req_filebacked drivers/block/loop.c:668 [inline] loop_handle_cmd drivers/block/loop.c:2202 [inline] loop_process_work+0xc60/0x24e0 drivers/block/loop.c:2242 process_one_work+0x98d/0x1630 kernel/workqueue.c:2276 worker_thread+0x658/0x11f0 kernel/workqueue.c:2422 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 -> #1 ((work_completion)(&lo->rootcg_work)){+.+.}-{0:0}: process_one_work+0x8fc/0x1630 kernel/workqueue.c:2252 worker_thread+0x658/0x11f0 kernel/workqueue.c:2422 kthread+0x3e5/0x4d0 kernel/kthread.c:319 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 -> #0 ((wq_completion)loop0){+.+.}-{0:0}: check_prev_add kernel/locking/lockdep.c:3051 [inline] check_prevs_add kernel/locking/lockdep.c:3174 [inline] validate_chain kernel/locking/lockdep.c:3789 [inline] __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015 lock_acquire kernel/locking/lockdep.c:5625 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 flush_workqueue+0x110/0x1600 kernel/workqueue.c:2787 drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2952 destroy_workqueue+0x71/0x800 kernel/workqueue.c:4389 __loop_clr_fd+0x212/0x15e0 drivers/block/loop.c:1368 loop_clr_fd drivers/block/loop.c:1494 [inline] lo_ioctl+0x3c3/0x1880 drivers/block/loop.c:1850 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:587 block_ioctl+0xf9/0x140 fs/block_dev.c:1569 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:866 [inline] __se_sys_ioctl fs/ioctl.c:852 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:852 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Chain exists of: (wq_completion)loop0 --> loop_ctl_mutex --> &lo->lo_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&lo->lo_mutex); lock(loop_ctl_mutex); lock(&lo->lo_mutex); lock((wq_completion)loop0); *** DEADLOCK *** 1 lock held by syz-executor258/6697: #0: ffff88801d535468 (&lo->lo_mutex){+.+.}-{3:3}, at: __loop_clr_fd+0xaf/0x15e0 drivers/block/loop.c:1350 stack backtrace: CPU: 1 PID: 6697 Comm: syz-executor258 Not tainted 5.14.0-rc3-next-20210729-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:105 check_noncircular+0x25f/0x2e0 kernel/locking/lockdep.c:2131 check_prev_add kernel/locking/lockdep.c:3051 [inline] check_prevs_add kernel/locking/lockdep.c:3174 [inline] validate_chain kernel/locking/lockdep.c:3789 [inline] __lock_acquire+0x2a07/0x54a0 kernel/locking/lockdep.c:5015 lock_acquire kernel/locking/lockdep.c:5625 [inline] lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5590 flush_workqueue+0x110/0x1600 kernel/workqueue.c:2787 drain_workqueue+0x1a5/0x3c0 kernel/workqueue.c:2952 destroy_workqueue+0x71/0x800 kernel/workqueue.c:4389 __loop_clr_fd+0x212/0x15e0 drivers/block/loop.c:1368 loop_clr_fd drivers/block/loop.c:1494 [inline] lo_ioctl+0x3c3/0x1880 drivers/block/loop.c:1850 blkdev_ioctl+0x2a1/0x6d0 block/ioctl.c:587 block_ioctl+0xf9/0x140 fs/block_dev.c:1569 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:866 [inline] __se_sys_ioctl fs/ioctl.c:852 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:852 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x444717 Code: 3c 1c 48 f7 d8 49 39 c4 72 b8 e8 44 3a 02 00 85 c0 78 bd 48 83 c4 08 4c 89 e0 5b 41 5c c3 0f 1f 44 00 00 b8 10 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fffab8ca568 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 00000000016232c0 RCX: 0000000000444717 RDX: 0000000000000000 RSI: 0000000000004c01 RDI: 0000000000000007 RBP: 0000000000000075 R08: 00007fffab8ca5c0 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00000000200002a8 R13: 0000000000000006 R14: 0000000000000007 R15: 0000000000000007