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 76C153D1CB0 for ; Tue, 9 Jun 2026 22:53:32 +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=1781045614; cv=none; b=p6+3ys/F34upFkzoeIjA7mXMb8rkpF1AJ6mFpTCaXBvl2tHESDY5h8Ke/NixlLD/sycLlogr+8claDB+g9CMMSZnl7XFlAdVd4qrp3yFDNbfqshbklbUjJ3qh3Tq7fYxwtwkr/X4QHsqOPz0pH09brdKHyqh9CzfsSKj09t62+c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781045614; c=relaxed/simple; bh=acAIGBN8+1G8vv+w4e/sIRF6UpHFufOAg2SSd8QATh8=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=u+KivewENUIcyg7apzqyEcWfXRcr2yoMQqLm8yzIxSOwV1kW5Bj/hcF7yTDw4Ih/EA3UjypzJXlc5Qk3U530FwOaYuq3ceLpfc2bwGT6+dzxQC3Ofl+0f0UWqEobF6odPOyXwAPQQzyudImYPblmsY0nkTC/Vud2xh1WZdhOb/w= 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 46e09a7af769-7e6da8558a6so6580864a34.3 for ; Tue, 09 Jun 2026 15:53:32 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1781045611; x=1781650411; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=0fKaDRWF6t4va2q63hZBT5YQboAcncVcNFLzlcbGkuY=; b=GR7rINmOoMIsZTe9TG5FMGv9ErZ/K4WMc6cwEQf/Ly8/VIPwQOjjqmiXQHBDC5EIYN yKdUsSMfpzoAJ8JiKCqbmZfG/7mq5KSG/fD60Qr4DosxX+hCwgXHGfgEeYi1TjUaDYnX uSu61Cv8BYl85woyc/e7BrPStaT9i/AQrxzmexh697jpXMrv+0/b2wRrBkTT+gHAj05B 74JVLa8mjKMpK7B3jH4nxX0nYxmqhvKgNmJxYjCnGH2vvF+TBZbxoOJkwsYduEYtx0wq 8a/UstZ9IIaHhz5RTUUfoQVrdDQPb4hC1aIqbLbMW1GeNUHaJbKOCE70zjlRuF4k3hLr cX9w== X-Forwarded-Encrypted: i=1; AFNElJ+b1luWPXLH3Ky4AwXLPLZt8kByK8KzNgk9d5w7Hyfl1nPLFUXg9NEOU7KDS7WFN7w/URFj+tXFO6YbuqY=@vger.kernel.org X-Gm-Message-State: AOJu0Yy78OXPd+WZ0m5UitIpyaEfd0acdXTBZbPY5qdU7BX57N8XGV8b YnV7jL/YgVO2KCEupFpSaOpLGr785oHd50/d7GNiEnVvzbNSU1AaYUkJxSUREzTNLFQJUbppsHi EqoLqCAvVubnovXioyjBSGiZvpO+GeWeHsmgEWgH9/lnirrXQ7NG5LVcNFCU= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:83d8:10b0:69b:5486:e85 with SMTP id 006d021491bc7-69e68c19e38mr9307417eaf.36.1781045611493; Tue, 09 Jun 2026 15:53:31 -0700 (PDT) Date: Tue, 09 Jun 2026 15:53:31 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a28996b.39669fcc.33b062.00a7.GAE@google.com> Subject: [syzbot] [kernel?] possible deadlock in worker_thread (4) From: syzbot To: bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@redhat.com, syzkaller-bugs@googlegroups.com, tglx@kernel.org, x86@kernel.org Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 33d8d8ec31b5 Merge tag 'input-for-v7.1-rc6' of git://git.k.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=142af166580000 kernel config: https://syzkaller.appspot.com/x/.config?x=8118209836970b54 dashboard link: https://syzkaller.appspot.com/bug?extid=2085e7afdf5e45082044 compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-33d8d8ec.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/c607cefe3513/vmlinux-33d8d8ec.xz kernel image: https://storage.googleapis.com/syzbot-assets/0c1c158edeeb/bzImage-33d8d8ec.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+2085e7afdf5e45082044@syzkaller.appspotmail.com ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Tainted: G L ------------------------------------------------------ kworker/u33:1/5095 is trying to acquire lock: ffff888029b3d260 (&nbd->config_lock){+.+.}-{4:4}, at: refcount_dec_and_mutex_lock+0x51/0x100 lib/refcount.c:118 but task is already holding lock: ffffc90028a4fd08 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x973/0x1980 kernel/workqueue.c:3290 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 ((work_completion)(&args->work)){+.+.}-{0:0}: process_one_work+0x979/0x1980 kernel/workqueue.c:3290 process_scheduled_works kernel/workqueue.c:3397 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 ((wq_completion)nbd2-recv){+.+.}-{0:0}: touch_wq_lockdep_map+0xad/0x1c0 kernel/workqueue.c:4029 __flush_workqueue+0x131/0x1200 kernel/workqueue.c:4071 nbd_disconnect_and_put+0x9b/0x1c0 drivers/block/nbd.c:2264 nbd_genl_disconnect+0x34b/0x4e0 drivers/block/nbd.c:2303 genl_family_rcv_msg_doit+0x214/0x300 net/netlink/genetlink.c:1114 genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline] genl_rcv_msg+0x560/0x800 net/netlink/genetlink.c:1209 netlink_rcv_skb+0x159/0x420 net/netlink/af_netlink.c:2555 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1899 sock_sendmsg_nosec net/socket.c:787 [inline] __sock_sendmsg net/socket.c:802 [inline] ____sys_sendmsg+0x9e1/0xb70 net/socket.c:2698 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2752 __sys_sendmsg+0x170/0x220 net/socket.c:2784 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&nbd->config_lock){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b1/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1b10 kernel/locking/mutex.c:820 refcount_dec_and_mutex_lock+0x51/0x100 lib/refcount.c:118 nbd_config_put+0x31/0x750 drivers/block/nbd.c:1434 recv_work+0x63a/0x8c0 drivers/block/nbd.c:1026 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314 process_scheduled_works kernel/workqueue.c:3397 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 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: &nbd->config_lock --> (wq_completion)nbd2-recv --> (work_completion)(&args->work) Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock((work_completion)(&args->work)); lock((wq_completion)nbd2-recv); lock((work_completion)(&args->work)); lock(&nbd->config_lock); *** DEADLOCK *** 2 locks held by kworker/u33:1/5095: #0: ffff888029bbc940 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_one_work+0x12d6/0x1980 kernel/workqueue.c:3289 #1: ffffc90028a4fd08 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x973/0x1980 kernel/workqueue.c:3290 stack backtrace: CPU: 1 UID: 0 PID: 5095 Comm: kworker/u33:1 Tainted: G L syzkaller #0 PREEMPT(full) Tainted: [L]=SOFTLOCKUP Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Workqueue: nbd1-recv recv_work Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120 print_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x14b8/0x2630 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x1b1/0x370 kernel/locking/lockdep.c:5825 __mutex_lock_common kernel/locking/mutex.c:646 [inline] __mutex_lock+0x1a4/0x1b10 kernel/locking/mutex.c:820 refcount_dec_and_mutex_lock+0x51/0x100 lib/refcount.c:118 nbd_config_put+0x31/0x750 drivers/block/nbd.c:1434 recv_work+0x63a/0x8c0 drivers/block/nbd.c:1026 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3314 process_scheduled_works kernel/workqueue.c:3397 [inline] worker_thread+0x5ef/0xe50 kernel/workqueue.c:3478 kthread+0x370/0x450 kernel/kthread.c:436 ret_from_fork+0x72b/0xd50 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