INFO: task syz.2.2606:16095 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.2606 state:D stack:27064 pid:16095 tgid:16093 ppid:5625 task_flags:0x400140 flags:0x00080002
Call Trace:
context_switch kernel/sched/core.c:5510 [inline]
__schedule+0x17d9/0x56c0 kernel/sched/core.c:7234
__schedule_loop kernel/sched/core.c:7311 [inline]
schedule+0x164/0x2b0 kernel/sched/core.c:7326
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7383
__mutex_lock_common kernel/locking/mutex.c:726 [inline]
__mutex_lock+0x7bf/0x1550 kernel/locking/mutex.c:821
nfsd_nl_expkey_set_reqs_doit+0xfe/0xaf0 fs/nfsd/export.c:561
genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x7bb/0x940 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900
sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775
__sock_sendmsg net/socket.c:790 [inline]
____sys_sendmsg+0x54e/0x850 net/socket.c:2684
___sys_sendmsg+0x2a5/0x360 net/socket.c:2738
__sys_sendmsg net/socket.c:2770 [inline]
__do_sys_sendmsg net/socket.c:2775 [inline]
__se_sys_sendmsg net/socket.c:2773 [inline]
__x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2773
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f811a39de99
RSP: 002b:00007f811b2c5028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f811a625fa0 RCX: 00007f811a39de99
RDX: 0000000004000080 RSI: 0000200000000100 RDI: 0000000000000003
RBP: 00007f811a433eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f811a626038 R14: 00007f811a625fa0 R15: 00007fff123190c8
Showing all locks held in the system:
1 lock held by ksoftirqd/0/15:
#0: ffff8880b863b160 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160 kernel/sched/core.c:667
1 lock held by khungtaskd/30:
#0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
#0: ffffffff8eb59c60 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
1 lock held by udevd/4989:
2 locks held by getty/5381:
#0: ffff888036adf0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc9000322b2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
2 locks held by udevd/15619:
2 locks held by syz.0.2595/16041:
#0: ffffffff9009cba8 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
#1: ffffffff8ee8e620 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0x135/0x1750 fs/nfsd/nfsctl.c:1964
2 locks held by syz.2.2606/16095:
#0: ffffffff9009cba8 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
#1: ffffffff8ee8e620 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_expkey_set_reqs_doit+0xfe/0xaf0 fs/nfsd/export.c:561
5 locks held by syz.6.3624/20059:
#0: ffffffff9009cba8 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
#1: ffffffff9009c9e0 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline]
#1: ffffffff9009c9e0 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline]
#1: ffffffff9009c9e0 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x10b/0x7a0 net/netlink/genetlink.c:1208
#2: ffff888028064a60 (&nbd->config_lock){+.+.}-{4:4}, at: nbd_genl_connect+0x9b4/0x1c10 drivers/block/nbd.c:2169
#3: ffff888027fd2ef0 (&q->q_usage_counter(io)#52){++++}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline]
#3: ffff888027fd2ef0 (&q->q_usage_counter(io)#52){++++}-{0:0}, at: nbd_add_socket+0x87f/0x1250 drivers/block/nbd.c:1299
#4: ffff888027fd2f28 (&q->q_usage_counter(queue)#36){+.+.}-{0:0}, at: blk_mq_freeze_queue include/linux/blk-mq.h:956 [inline]
#4: ffff888027fd2f28 (&q->q_usage_counter(queue)#36){+.+.}-{0:0}, at: nbd_add_socket+0x87f/0x1250 drivers/block/nbd.c:1299
2 locks held by syz.6.3624/20061:
#0: ffffffff9009cba8 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
#1: ffffffff9009c9e0 (genl_mutex){+.+.}-{4:4}, at: genl_lock net/netlink/genetlink.c:35 [inline]
#1: ffffffff9009c9e0 (genl_mutex){+.+.}-{4:4}, at: genl_op_lock net/netlink/genetlink.c:60 [inline]
#1: ffffffff9009c9e0 (genl_mutex){+.+.}-{4:4}, at: genl_rcv_msg+0x10b/0x7a0 net/netlink/genetlink.c:1208
2 locks held by syz.3.3627/20065:
#0: ffffffff9002c340 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:80 [inline]
#0: ffffffff9002c340 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:134 [inline]
#0: ffffffff9002c340 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_dellink+0x41b/0x810 net/core/rtnetlink.c:3666
#1: ffffffff8eb5ff68 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:343 [inline]
#1: ffffffff8eb5ff68 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x38d/0x770 kernel/rcu/tree_exp.h:961
=============================================
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 30 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
Call Trace:
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:122
nmi_trigger_cpumask_backtrace+0x17a/0x380 lib/nmi_backtrace.c:65
trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x135/0x170 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
watchdog+0xfd7/0x1030 kernel/hung_task.c:561
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
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 20059 Comm: syz.6.3624 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/25/2026
RIP: 0010:io_serial_in+0x77/0xc0 drivers/tty/serial/8250/8250_port.c:401
Code: e8 0e ab 60 fc 44 89 f9 d3 e3 49 83 c6 40 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 9f 37 ce fc 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f c3 cc cc cc cc cc 44 89 f9 80 e1 07
RSP: 0018:ffffc900063de9c8 EFLAGS: 00000002
RAX: 1ffffffff3559a00 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000000 RDI: 0000000000000020
RBP: dffffc0000000000 R08: ffff888142688237 R09: 1ffff110284d1046
R10: dffffc0000000000 R11: ffffffff8565c6e0 R12: dffffc0000000000
R13: 0000000000000000 R14: ffffffff9aacd0e0 R15: 0000000000000000
FS: 00007fb7523f66c0(0000) GS:ffff888124f5e000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000008abc4000 CR4: 00000000003526f0
Call Trace:
serial_in drivers/tty/serial/8250/8250.h:128 [inline]
serial_lsr_in drivers/tty/serial/8250/8250.h:150 [inline]
wait_for_lsr+0x184/0x2f0 drivers/tty/serial/8250/8250_port.c:1982
serial8250_fifo_wait_for_lsr_thre drivers/tty/serial/8250/8250_port.c:3229 [inline]
serial8250_console_fifo_write drivers/tty/serial/8250/8250_port.c:3294 [inline]
serial8250_console_write+0x12ef/0x1ba0 drivers/tty/serial/8250/8250_port.c:3379
console_emit_next_record kernel/printk/printk.c:3183 [inline]
console_flush_one_record kernel/printk/printk.c:3269 [inline]
console_flush_all+0x6ea/0xaf0 kernel/printk/printk.c:3343
__console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413
vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479
dev_vprintk_emit+0x338/0x400 drivers/base/core.c:4996
dev_printk_emit+0xee/0x140 drivers/base/core.c:5007
_dev_err+0x11e/0x180 drivers/base/core.c:5062
nbd_start_device+0xa29/0xb30 drivers/block/nbd.c:1520
nbd_genl_connect+0x1597/0x1c10 drivers/block/nbd.c:2276
genl_family_rcv_msg_doit+0x233/0x340 net/netlink/genetlink.c:1114
genl_family_rcv_msg net/netlink/genetlink.c:1194 [inline]
genl_rcv_msg+0x614/0x7a0 net/netlink/genetlink.c:1209
netlink_rcv_skb+0x226/0x4a0 net/netlink/af_netlink.c:2556
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
netlink_unicast+0x7bb/0x940 net/netlink/af_netlink.c:1345
netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1900
sock_sendmsg_nosec+0x13a/0x180 net/socket.c:775
__sock_sendmsg net/socket.c:790 [inline]
____sys_sendmsg+0x54e/0x850 net/socket.c:2684
___sys_sendmsg+0x2a5/0x360 net/socket.c:2738
__sys_sendmsg net/socket.c:2770 [inline]
__do_sys_sendmsg net/socket.c:2775 [inline]
__se_sys_sendmsg net/socket.c:2773 [inline]
__x64_sys_sendmsg+0x1b1/0x290 net/socket.c:2773
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb75419de99
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:00007fb7523f6028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb754425fa0 RCX: 00007fb75419de99
RDX: 0000000000004000 RSI: 00002000000027c0 RDI: 0000000000000087
RBP: 00007fb754233eaf R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb754426038 R14: 00007fb754425fa0 R15: 00007ffd52742868