From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f77.google.com (mail-ot1-f77.google.com [209.85.210.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2A9353DDDD0 for ; Fri, 29 May 2026 20:24:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.77 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780086265; cv=none; b=UjPvCsJI56GpEjl2WyuXMCthWNKCSD9VB2DRKnimjeeQoFYDSzDJf7eRa5LbuZsniRPpg6mVPp0ywZ1ppxIN1dTwbEwn3wUN2ElTH2lSB4S9IBwIe0zLb02z8BoT0DuAvt6Fuq01q5Qo5eOM8snjwBxu0GBnhIPH9YBsmKbYOp4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780086265; c=relaxed/simple; bh=KV5VMm7/VC1hJWQOBiL4rGD/rH+9kOHRjNhc8r+FI9g=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=DfGCg4JtZkqtHku9gv0fAUhKiodW2aKdTMud5wiWIRS9TQjALMXy8rtmXZ/M4LxpIcDR6sO8aUpuzI3Sg9w4YJJhW8Z5016qTmdbjPl/SQ2Dki4zBUVFctKLIPgV+qmB6h54csPr384NJSQuQISvJqsva5jFkiczMUbgQflbOuE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.210.77 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-ot1-f77.google.com with SMTP id 46e09a7af769-7e6243b98a4so9143709a34.2 for ; Fri, 29 May 2026 13:24:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780086263; x=1780691063; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=X0TQxfICKBbu6glso4OaEWkl0BSNliKzRICC8t754e4=; b=XGcNwGi2ik2AKMBMKDzkGftc9sXqC4A/1lHUMMUiTee1JDkgzKajSokxwvwluiMDL5 6aCPPluEam35YHFpLWpgeLMg4aKBa8GznrZDZ2vULcZnjomJjyaFRb/3qt/ibwrYWnFx JQTotjcLcbdQXAayQdbhlh96GOUXC87tVSoPIdfK33BAe7mdAbRVVdxRyiNEVaEFcg4S +KJnZMQPb+N5g9RT3Owk0qv5/BNhPW8A/E8Y2gHJzZl2sgIlvNcmSsL/N6VqXOd9hNsY egSqOb8hk5IUatWRuKS3Qs+8jS+73gVHkUISncJXvako+iReliecbLUDWtDWcGqwFoyg VQiw== X-Forwarded-Encrypted: i=1; AFNElJ8iWCTRfP+od3FKxg3NfLQljH8dFBwLv/e1bVYYZ7nRoljlcy/NOECKBiNGOxVcSOt9JKtKqFDG2jkWWQ==@vger.kernel.org X-Gm-Message-State: AOJu0YzTRUvS5BLJOCVWIW2ZGpi+ptShFWpzLq56lsHhvKfdXJIlD/xm QfkQjoOvQPA9txYcz+KYB3upb1YFj6wKyEwRvoJ336QNQ09LQj+4kBUZVd9m3dKn4wkEoo8+Ukp 9BqZzYTxc7iRmRavIOfJM/539ZKyD7amf2Jd59KpLmR3qjcqiZGudASImuAo= Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:2904:b0:69d:e555:224f with SMTP id 006d021491bc7-69e1019b557mr458102eaf.6.1780086263124; Fri, 29 May 2026 13:24:23 -0700 (PDT) Date: Fri, 29 May 2026 13:24:23 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a19f5f7.5099cdd9.8e407.0004.GAE@google.com> Subject: [syzbot] [block?] possible deadlock in loop_process_work From: syzbot To: axboe@kernel.dk, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: c1ecb239fa34 Add linux-next specific files for 20260522 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=12fa6336580000 kernel config: https://syzkaller.appspot.com/x/.config?x=77a9211ff284de54 dashboard link: https://syzkaller.appspot.com/bug?extid=78ad2c6a58c0a1faa5f5 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/4cb88c910144/disk-c1ecb239.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/4a9bc938cf88/vmlinux-c1ecb239.xz kernel image: https://storage.googleapis.com/syzbot-assets/684f1e33f264/bzImage-c1ecb239.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+78ad2c6a58c0a1faa5f5@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ kworker/u8:15/1491 is trying to acquire lock: ffff88805e1a6480 (sb_writers#5){.+.+}-{0:0}, at: do_req_filebacked drivers/block/loop.c:433 [inline] ffff88805e1a6480 (sb_writers#5){.+.+}-{0:0}, at: loop_handle_cmd drivers/block/loop.c:1941 [inline] ffff88805e1a6480 (sb_writers#5){.+.+}-{0:0}, at: loop_process_work+0x637/0x11b0 drivers/block/loop.c:1976 but task is already holding lock: ffffc90006e27c40 ((work_completion)(&worker->work)){+.+.}-{0:0}, at: process_one_work+0x8be/0x1630 kernel/workqueue.c:3294 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #7 ((work_completion)(&worker->work)){+.+.}-{0:0}: process_one_work+0x8d7/0x1630 kernel/workqueue.c:3294 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #6 ((wq_completion)loop4){+.+.}-{0:0}: touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:4033 __flush_workqueue+0x14b/0x14f0 kernel/workqueue.c:4075 drain_workqueue+0xd3/0x390 kernel/workqueue.c:4239 __loop_clr_fd drivers/block/loop.c:1130 [inline] lo_release+0x287/0x8f0 drivers/block/loop.c:1767 bdev_release+0x541/0x660 block/bdev.c:-1 blkdev_release+0x15/0x20 block/fops.c:705 __fput+0x461/0xa70 fs/file_table.c:510 fput_close_sync+0x11f/0x240 fs/file_table.c:615 __do_sys_close fs/open.c:1511 [inline] __se_sys_close fs/open.c:1496 [inline] __x64_sys_close+0x7e/0x110 fs/open.c:1496 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #5 (&disk->open_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578 __del_gendisk+0x127/0x980 block/genhd.c:710 del_gendisk+0xe7/0x160 block/genhd.c:823 nbd_dev_remove drivers/block/nbd.c:268 [inline] nbd_dev_remove_work+0x47/0xe0 drivers/block/nbd.c:284 process_one_work+0x98b/0x1630 kernel/workqueue.c:3318 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #4 (&set->update_nr_hwq_lock){++++}-{4:4}: down_read+0x97/0x200 kernel/locking/rwsem.c:1568 add_disk_fwnode+0xe7/0x480 block/genhd.c:596 add_disk include/linux/blkdev.h:794 [inline] nbd_dev_add+0x72c/0xb50 drivers/block/nbd.c:1984 nbd_genl_connect+0x965/0x1c80 drivers/block/nbd.c:2125 genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2551 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x780/0x920 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1895 sock_sendmsg_nosec+0x112/0x150 net/socket.c:797 __sock_sendmsg net/socket.c:812 [inline] ____sys_sendmsg+0x55c/0x870 net/socket.c:2716 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2770 __sys_sendmsg net/socket.c:2802 [inline] __do_sys_sendmsg net/socket.c:2807 [inline] __se_sys_sendmsg net/socket.c:2805 [inline] __x64_sys_sendmsg+0x1c3/0x2a0 net/socket.c:2805 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #3 (genl_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578 genl_lock net/netlink/genetlink.c:35 [inline] genl_lock_all net/netlink/genetlink.c:48 [inline] genl_register_family+0x7b9/0x17b0 net/netlink/genetlink.c:784 vdpa_init+0x39/0x70 drivers/vdpa/vdpa.c:1565 do_one_initcall+0x250/0x870 init/main.c:1347 do_initcall_level+0x104/0x190 init/main.c:1409 do_initcalls+0x59/0xa0 init/main.c:1425 kernel_init_freeable+0x2a6/0x3e0 init/main.c:1658 kernel_init+0x1d/0x1d0 init/main.c:1548 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #2 (cb_lock){++++}-{4:4}: down_read+0x97/0x200 kernel/locking/rwsem.c:1568 genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline] netlink_unicast+0x780/0x920 net/netlink/af_netlink.c:1345 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1895 sock_sendmsg_nosec+0x112/0x150 net/socket.c:797 __sock_sendmsg net/socket.c:812 [inline] sock_sendmsg+0x1ca/0x2d0 net/socket.c:835 splice_to_socket+0xae5/0x11f0 fs/splice.c:884 do_splice_from fs/splice.c:936 [inline] do_splice+0xef8/0x1940 fs/splice.c:1349 __do_splice fs/splice.c:1431 [inline] __do_sys_splice fs/splice.c:1634 [inline] __se_sys_splice+0x353/0x490 fs/splice.c:1616 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&pipe->mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:559 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:578 iter_file_splice_write+0x1f3/0x10f0 fs/splice.c:682 do_splice_from fs/splice.c:936 [inline] do_splice+0xef8/0x1940 fs/splice.c:1349 __do_splice fs/splice.c:1431 [inline] __do_sys_splice fs/splice.c:1634 [inline] __se_sys_splice+0x353/0x490 fs/splice.c:1616 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0x560 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (sb_writers#5){.+.+}-{0:0}: check_prev_add kernel/locking/lockdep.c:3167 [inline] check_prevs_add kernel/locking/lockdep.c:3286 [inline] validate_chain kernel/locking/lockdep.c:3910 [inline] __lock_acquire+0x15a5/0x2d10 kernel/locking/lockdep.c:5239 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline] __sb_start_write include/linux/fs/super.h:19 [inline] sb_start_write include/linux/fs/super.h:125 [inline] kiocb_start_write include/linux/fs.h:2767 [inline] lo_rw_aio+0xb1b/0xf00 drivers/block/loop.c:401 do_req_filebacked drivers/block/loop.c:433 [inline] loop_handle_cmd drivers/block/loop.c:1941 [inline] loop_process_work+0x637/0x11b0 drivers/block/loop.c:1976 process_one_work+0x98b/0x1630 kernel/workqueue.c:3318 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 other info that might help us debug this: Chain exists of: sb_writers#5 --> (wq_completion)loop4 --> (work_completion)(&worker->work) Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((work_completion)(&worker->work)); lock((wq_completion)loop4); lock((work_completion)(&worker->work)); rlock(sb_writers#5); *** DEADLOCK *** 2 locks held by kworker/u8:15/1491: #0: ffff888022729938 ((wq_completion)loop5){+.+.}-{0:0}, at: process_one_work+0x897/0x1630 kernel/workqueue.c:3293 #1: ffffc90006e27c40 ((work_completion)(&worker->work)){+.+.}-{0:0}, at: process_one_work+0x8be/0x1630 kernel/workqueue.c:3294 stack backtrace: CPU: 0 UID: 0 PID: 1491 Comm: kworker/u8:15 Tainted: G L syzkaller #0 PREEMPT_{RT,(full)} Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Workqueue: loop5 loop_workfn Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2045 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2177 check_prev_add kernel/locking/lockdep.c:3167 [inline] check_prevs_add kernel/locking/lockdep.c:3286 [inline] validate_chain kernel/locking/lockdep.c:3910 [inline] __lock_acquire+0x15a5/0x2d10 kernel/locking/lockdep.c:5239 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5870 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline] __sb_start_write include/linux/fs/super.h:19 [inline] sb_start_write include/linux/fs/super.h:125 [inline] kiocb_start_write include/linux/fs.h:2767 [inline] lo_rw_aio+0xb1b/0xf00 drivers/block/loop.c:401 do_req_filebacked drivers/block/loop.c:433 [inline] loop_handle_cmd drivers/block/loop.c:1941 [inline] loop_process_work+0x637/0x11b0 drivers/block/loop.c:1976 process_one_work+0x98b/0x1630 kernel/workqueue.c:3318 process_scheduled_works kernel/workqueue.c:3401 [inline] worker_thread+0xb49/0x1140 kernel/workqueue.c:3482 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup