syzbot

INFO: task syz.3.2391:16076 blocked for more than 143 seconds.
      Tainted: G     U              6.15.0-rc5-syzkaller-00353-gcd802e7e5f1e #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.2391      state:D stack:27992 pid:16076 tgid:16072 ppid:15308  task_flags:0x400040 flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x116f/0x5de0 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6860
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6917
 __mutex_lock_common kernel/locking/mutex.c:678 [inline]
 __mutex_lock+0x6c7/0xb90 kernel/locking/mutex.c:746
 nfsd_nl_threads_get_doit+0x1c6/0x7c0 fs/nfsd/nfsctl.c:1713
 genl_family_rcv_msg_doit+0x206/0x2f0 net/netlink/genetlink.c:1115
 genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
 genl_rcv_msg+0x55c/0x800 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x16a/0x440 net/netlink/af_netlink.c:2534
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x53a/0x7f0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg net/socket.c:727 [inline]
 ____sys_sendmsg+0xa95/0xc70 net/socket.c:2566
 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2620
 __sys_sendmsg+0x16d/0x220 net/socket.c:2652
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x230 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f7ba0f8e969
RSP: 002b:00007f7b9edd5038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7ba11b6080 RCX: 00007f7ba0f8e969
RDX: 0000000000000004 RSI: 00002000000000c0 RDI: 0000000000000003
RBP: 00007f7ba1010ab1 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f7ba11b6080 R15: 00007fffc0643898
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e3bf400 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e3bf400 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8e3bf400 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6764
3 locks held by kworker/u8:4/63:
 #0: ffff88801b489148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc90001557d18 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffffffff90126f28 (rtnl_mutex){+.+.}-{4:4}, at: linkwatch_event+0x51/0xc0 net/core/link_watch.c:303
1 lock held by dhcpcd/5497:
 #0: ffffffff90126f28 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #0: ffffffff90126f28 (rtnl_mutex){+.+.}-{4:4}, at: inet_rtm_deladdr+0x15d/0x7c0 net/ipv4/devinet.c:671
2 locks held by kworker/u9:3/5834:
 #0: ffff888025feb948 ((wq_completion)nbd0-recv){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc900040bfd18 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
3 locks held by kworker/u8:10/14520:
 #0: ffff88801cff0948 ((wq_completion)cfg80211){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc900108ffd18 ((work_completion)(&(&rdev->dfs_update_channels_wk)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffffffff90126f28 (rtnl_mutex){+.+.}-{4:4}, at: cfg80211_dfs_channels_update_work+0xcf/0x640 net/wireless/mlme.c:1022
2 locks held by getty/16000:
 #0: ffff888031da50a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002f762f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x14f0 drivers/tty/n_tty.c:2222
2 locks held by syz.3.2391/16075:
 #0: ffffffff901c8fd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xdd/0x1a40 fs/nfsd/nfsctl.c:1923
2 locks held by syz.3.2391/16076:
 #0: ffffffff901c8fd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_threads_get_doit+0x1c6/0x7c0 fs/nfsd/nfsctl.c:1713
3 locks held by kworker/u8:40/16389:
 #0: ffff88803166a148 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3213
 #1: ffffc90003d0fd18 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3214
 #2: ffffffff90126f28 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #2: ffffffff90126f28 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x120/0x14e0 net/ipv6/addrconf.c:4198
2 locks held by syz-executor/16599:
 #0: ffff88803207a0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88803207a0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88803207a0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super fs/super.c:505 [inline]
 #0: ffff88803207a0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:502
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:596
2 locks held by syz-executor/16820:
 #0: ffff888070f220e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff888070f220e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff888070f220e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super fs/super.c:505 [inline]
 #0: ffff888070f220e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:502
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:596
2 locks held by syz-executor/17076:
 #0: ffff88806d54e0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88806d54e0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88806d54e0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super fs/super.c:505 [inline]
 #0: ffff88806d54e0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:502
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:596
2 locks held by syz.7.2751/17933:
 #0: ffffffff901c8fd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xdd/0x1a40 fs/nfsd/nfsctl.c:1923
2 locks held by syz-executor/18117:
 #0: ffff88807d4da0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88807d4da0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88807d4da0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super fs/super.c:505 [inline]
 #0: ffff88807d4da0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:502
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:596
2 locks held by syz-executor/18162:
 #0: ffff88804d61c0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88804d61c0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88804d61c0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super fs/super.c:505 [inline]
 #0: ffff88804d61c0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:502
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:596
2 locks held by syz-executor/18230:
 #0: ffff88801e7fe0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88801e7fe0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88801e7fe0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super fs/super.c:505 [inline]
 #0: ffff88801e7fe0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:502
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:596
2 locks held by syz.6.2829/18446:
 #0: ffffffff901c8fd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_threads_set_doit+0x698/0xbf0 fs/nfsd/nfsctl.c:1629
2 locks held by syz-executor/18472:
 #0: ffff88806333c0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
 #0: ffff88806333c0e0 (&type->s_umount_key#51){++++}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
 #0: ffff88806333c0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super fs/super.c:505 [inline]
 #0: ffff88806333c0e0 (&type->s_umount_key#51){++++}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:502
 #1: ffffffff8e7cc028 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:596
1 lock held by syz.3.2873/18978:
 #0: ffffffff8e3ca938 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x1a3/0x3c0 kernel/rcu/tree_exp.h:336
3 locks held by syz.4.2874/18982:
 #0: ffffffff901c8fd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff90126f28 (rtnl_mutex){+.+.}-{4:4}, at: nl80211_pre_doit+0xb4/0xb10 net/wireless/nl80211.c:16693
 #2: ffff88808e308768 (&rdev->wiphy.mtx){+.+.}-{4:4}, at: nl80211_del_interface+0xfb/0x190 net/wireless/nl80211.c:4574
3 locks held by syz.4.2874/18984:
 #0: ffffffff901c8fd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff901c9088 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline]
 #1: ffffffff901c9088 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline]
 #1: ffffffff901c9088 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:57 [inline]
 #1: ffffffff901c9088 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x577/0x800 net/netlink/genetlink.c:1209
 #2: ffffffff90126f28 (rtnl_mutex){+.+.}-{4:4}, at: tipc_nl_node_set_key+0x7d/0xb30 net/tipc/node.c:3045
2 locks held by dhcpcd/19012:
 #0: ffff8880620dca08 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:867 [inline]
 #0: ffff8880620dca08 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: __sock_release+0x86/0x270 net/socket.c:646
 #1: ffffffff8e3ca938 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x1a3/0x3c0 kernel/rcu/tree_exp.h:336
1 lock held by dhcpcd/19013:
 #0: ffff8880620dbe08 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:867 [inline]
 #0: ffff8880620dbe08 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: __sock_release+0x86/0x270 net/socket.c:646
1 lock held by dhcpcd/19014:
 #0: ffff8880620d8208 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: inode_lock include/linux/fs.h:867 [inline]
 #0: ffff8880620d8208 (&sb->s_type->i_mutex_key#11){+.+.}-{4:4}, at: __sock_release+0x86/0x270 net/socket.c:646

=============================================

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Tainted: G     U              6.15.0-rc5-syzkaller-00353-gcd802e7e5f1e #0 PREEMPT(full) 
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:274 [inline]
 watchdog+0xf70/0x12c0 kernel/hung_task.c:437
 kthread+0x3c2/0x780 kernel/kthread.c:464
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>