From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f198.google.com (mail-oi1-f198.google.com [209.85.167.198]) (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 91E0536D4EC for ; Tue, 17 Feb 2026 19:49:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771357774; cv=none; b=cVW52DYPihnIIF26f9qy2mWMy9v1S3wTRLsLYE5N426Pekcx9Mai0m+W0g+5RQXMxkN6pLKuP5JUPMGXSS/TGlM9siB5/PEP9EReajVPAfgBbckWHOt8NiyU5kOIfz+xpo0ijwaDxNkSbAkQmeMTw3WVsSdrC5lEf0uMQPRw8QM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771357774; c=relaxed/simple; bh=HTnMAddskUhHkKMIpW73k9V8tiGUfdqbQilYYA73G/s=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=EVP45Z5idQYEdeCC1XfMal1Ntli/wScQC0A1NLEY7frATeP6EUOS8s0cB5l3e+UsCzTLOzuuBuk/cRk1An240jZq6GFKS3Qxt5tICgEX/SkY30RoO4qqDE1egCfk3ZdkQQbRKPCVuVZzWeqWB5/5GxItrARhydYzX/ISx83IGXM= 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=209.85.167.198 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-oi1-f198.google.com with SMTP id 5614622812f47-45f16aa81a8so2532690b6e.1 for ; Tue, 17 Feb 2026 11:49:32 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771357771; x=1771962571; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=J7oG1PEXR6aRwD08qjBpn3IaU8PvlEnIDt61McOrYLU=; b=giea8Y6oYgEkKWHJMGGd6LdWn8QPIsNZdczB0vV5sx5avJYYDQN6BtRdF81b0TMMeK 3QQ6wTxW0n1UrnpI+z6CnNLh6UgipReMgGrroLCM+kgM4skY2bAJ5+XKd9or/3QgGl0a HE9HJIlyKdjVxXlfJ7KBu4/4GMyRKIKCoi+0qwc4/PaL4EqotiAR+MuLauaRMGbKHotj KCTIpfGZNiyquPWeu9ExKLONmh3xWgXA5fqkbpskHGXkgyjsXW2Efj1j/wHFPG60UP7A Xk5kQ6G7w6kkRYXXUqrnAceAzlNnpXVwFE/qUwbgF+3ViZf3QajkBVGiYq9rN7dkuH9p PFaw== X-Forwarded-Encrypted: i=1; AJvYcCWI5TTShks5wwQ+hgH7Ds08A5JjiZMXzaObg78Bw3zzqxshRTAn17vpnW6Yv2X9xOJ+/laMCar6+4pzMA==@vger.kernel.org X-Gm-Message-State: AOJu0YyeHW8S0n/N3pI3KscAEd1lsU+oCZapeQaTYw3CO5ELmDi7OUVV Ov0JawbaREbCsAJFNzE1Yfh68MdZawzvCLjjcylaYlbE+mfG434Yjc2Ni14nUMa7eS2SgHdUHED wRlLdRnhNpU7dCTBYXkis+lMw+DgVOWJoKoOBK+QOwEfcSMkcm2MIeZzuhco= Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:86d7:b0:464:5a7:7cd6 with SMTP id 5614622812f47-46405a7c2famr715814b6e.15.1771357771631; Tue, 17 Feb 2026 11:49:31 -0800 (PST) Date: Tue, 17 Feb 2026 11:49:31 -0800 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6994c64b.a70a0220.2c38d7.010a.GAE@google.com> Subject: [syzbot] [nbd?] possible deadlock in nbd_disconnect_and_put From: syzbot To: axboe@kernel.dk, josef@toxicpanda.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, nbd@other.debian.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 635c467cc14e Add linux-next specific files for 20260213 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=136df15a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=61690c38d1398936 dashboard link: https://syzkaller.appspot.com/bug?extid=3add0454d5a2619b8e80 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/78b3d15ca8e6/disk-635c467c.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/a95f3d108ef4/vmlinux-635c467c.xz kernel image: https://storage.googleapis.com/syzbot-assets/e58086838b24/bzImage-635c467c.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+3add0454d5a2619b8e80@syzkaller.appspotmail.com block nbd1: NBD_DISCONNECT block nbd1: Disconnected due to user request. block nbd1: shutting down sockets ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.1.1462/9805 is trying to acquire lock: ffff8880271c7948 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: touch_wq_lockdep_map+0xb5/0x180 kernel/workqueue.c:3994 but task is already holding lock: ffff888027014278 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_disconnect_and_put+0x2f/0x2c0 drivers/block/nbd.c:2256 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&nbd->config_lock){+.+.}-{4:4}: __mutex_lock_common kernel/locking/mutex.c:614 [inline] __mutex_lock+0x19f/0x1300 kernel/locking/mutex.c:776 refcount_dec_and_mutex_lock+0x30/0xa0 lib/refcount.c:118 nbd_config_put+0x2c/0x580 drivers/block/nbd.c:1434 recv_work+0x1cc1/0x1d90 drivers/block/nbd.c:1026 process_one_work+0x949/0x1650 kernel/workqueue.c:3279 process_scheduled_works kernel/workqueue.c:3362 [inline] worker_thread+0xb46/0x1140 kernel/workqueue.c:3443 kthread+0x388/0x470 kernel/kthread.c:467 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #1 ((work_completion)(&args->work)#3){+.+.}-{0:0}: process_one_work+0x895/0x1650 kernel/workqueue.c:3255 process_scheduled_works kernel/workqueue.c:3362 [inline] worker_thread+0xb46/0x1140 kernel/workqueue.c:3443 kthread+0x388/0x470 kernel/kthread.c:467 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 ((wq_completion)nbd1-recv){+.+.}-{0:0}: 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:3994 __flush_workqueue+0x14b/0x14f0 kernel/workqueue.c:4036 nbd_disconnect_and_put+0x9e/0x2c0 drivers/block/nbd.c:2264 nbd_genl_disconnect+0x4a9/0x590 drivers/block/nbd.c:2303 genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec+0x18f/0x1d0 net/socket.c:737 __sock_sendmsg net/socket.c:752 [inline] ____sys_sendmsg+0x589/0x8c0 net/socket.c:2610 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2664 __sys_sendmsg net/socket.c:2696 [inline] __do_sys_sendmsg net/socket.c:2701 [inline] __se_sys_sendmsg net/socket.c:2699 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2699 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: (wq_completion)nbd1-recv --> (work_completion)(&args->work)#3 --> &nbd->config_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&nbd->config_lock); lock((work_completion)(&args->work)#3); lock(&nbd->config_lock); lock((wq_completion)nbd1-recv); *** DEADLOCK *** 3 locks held by syz.1.1462/9805: #0: ffffffff8fe5ba70 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218 #1: ffffffff8fe5b888 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline] #1: ffffffff8fe5b888 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline] #1: ffffffff8fe5b888 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x10b/0x7a0 net/netlink/genetlink.c:1209 #2: ffff888027014278 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_disconnect_and_put+0x2f/0x2c0 drivers/block/nbd.c:2256 stack backtrace: CPU: 0 UID: 0 PID: 9805 Comm: syz.1.1462 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 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+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 touch_wq_lockdep_map+0xcb/0x180 kernel/workqueue.c:3994 __flush_workqueue+0x14b/0x14f0 kernel/workqueue.c:4036 nbd_disconnect_and_put+0x9e/0x2c0 drivers/block/nbd.c:2264 nbd_genl_disconnect+0x4a9/0x590 drivers/block/nbd.c:2303 genl_family_rcv_msg_doit+0x22a/0x330 net/netlink/genetlink.c:1115 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline] genl_rcv_msg+0x61c/0x7a0 net/netlink/genetlink.c:1210 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x80f/0x9b0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec+0x18f/0x1d0 net/socket.c:737 __sock_sendmsg net/socket.c:752 [inline] ____sys_sendmsg+0x589/0x8c0 net/socket.c:2610 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2664 __sys_sendmsg net/socket.c:2696 [inline] __do_sys_sendmsg net/socket.c:2701 [inline] __se_sys_sendmsg net/socket.c:2699 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2699 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f496959bf79 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f496a4cd028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f4969816090 RCX: 00007f496959bf79 RDX: 00000000000000c0 RSI: 0000200000000280 RDI: 0000000000000004 RBP: 00007f49696327e0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f4969816128 R14: 00007f4969816090 R15: 00007ffd35895958 --- 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