syzbot

INFO: task syz.4.2788:20043 blocked for more than 143 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.2788      state:D stack:26056 pid:20043 tgid:20036 ppid:19122  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0xdd/0x2c0 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+0xccc/0x1bd0 kernel/locking/mutex.c:821
 expkey_flush+0x18/0x90 fs/nfsd/export.c:253
 write_flush.isra.0+0x2af/0x3d0 net/sunrpc/cache.c:1543
 pde_write fs/proc/inode.c:330 [inline]
 proc_reg_write+0x240/0x330 fs/proc/inode.c:342
 do_loop_readv_writev fs/read_write.c:851 [inline]
 do_loop_readv_writev fs/read_write.c:836 [inline]
 vfs_writev+0x5ed/0xdd0 fs/read_write.c:1060
 do_writev+0x13e/0x340 fs/read_write.c:1104
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff21a99ce59
RSP: 002b:00007ff21b8e7028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007ff21ac16180 RCX: 00007ff21a99ce59
RDX: 000000000000000a RSI: 0000200000000240 RDI: 0000000000000007
RBP: 00007ff21aa32e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff21ac16218 R14: 00007ff21ac16180 R15: 00007ffc860b76a8
 </TASK>
INFO: task syz.1.2807:20147 blocked for more than 144 seconds.
      Tainted: G             L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.2807      state:D stack:26056 pid:20147 tgid:20143 ppid:17830  task_flags:0x400140 flags:0x00080006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5510 [inline]
 __schedule+0x125c/0x6730 kernel/sched/core.c:7234
 __schedule_loop kernel/sched/core.c:7311 [inline]
 schedule+0xdd/0x2c0 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+0xccc/0x1bd0 kernel/locking/mutex.c:821
 nfsd_nl_threads_set_doit+0x8c8/0x1100 fs/nfsd/nfsctl.c:1660
 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:2556
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x585/0x850 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1900
 sock_sendmsg_nosec net/socket.c:775 [inline]
 __sock_sendmsg net/socket.c:790 [inline]
 ____sys_sendmsg+0xa4d/0xbe0 net/socket.c:2684
 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2738
 __sys_sendmsg+0x160/0x210 net/socket.c:2770
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x115/0x840 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1c4e79ce59
RSP: 002b:00007f1c4f5ab028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f1c4ea16090 RCX: 00007f1c4e79ce59
RDX: 000000000000c840 RSI: 0000200000000480 RDI: 000000000000000b
RBP: 00007f1c4e832e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1c4ea16128 R14: 00007f1c4ea16090 R15: 00007ffe782e78f8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e7e5ec0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8e7e5ec0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8e7e5ec0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
2 locks held by getty/5383:
 #0: ffff8880333a90a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000322b2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14e0 drivers/tty/n_tty.c:2211
2 locks held by kworker/u8:35/11435:
 #0: ffff8880203dd940 ((wq_completion)iou_exit){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc90003cd7d08 ((work_completion)(&ctx->exit_work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
3 locks held by kworker/u8:37/11438:
 #0: ffff888033336140 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc900038c7d08 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffffffff9063edc0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #2: ffffffff9063edc0 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_verify_work+0x12/0x30 net/ipv6/addrconf.c:4769
4 locks held by kworker/u8:48/16946:
 #0: ffff88801c6c6140 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc90003b2fd08 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffffffff906261c8 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xb8/0x920 net/core/net_namespace.c:673
 #3: ffffffff9063edc0 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline]
 #3: ffffffff9063edc0 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x7ec/0xab0 net/core/net_namespace.c:248
2 locks held by syz.0.2785/20024:
 #0: ffffffff906ed668 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xd5/0x1a80 fs/nfsd/nfsctl.c:1964
3 locks held by syz.4.2788/20043:
 #0: ffff8880475b77b0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff88804dc02450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
2 locks held by syz.1.2807/20147:
 #0: ffffffff906ed668 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_threads_set_doit+0x8c8/0x1100 fs/nfsd/nfsctl.c:1660
3 locks held by syz.2.2825/20395:
 #0: ffff888033dd2ef0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff88803519e450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
3 locks held by syz.7.2819/20474:
 #0: ffff88803ed92630 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff888079ece450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
3 locks held by syz.5.2842/20503:
 #0: ffff88807fa7c0f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff88807c16c450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
3 locks held by syz.6.2849/20536:
 #0: ffff888078283270 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff88802b356450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
2 locks held by syz-executor/20630:
 #0: ffff88807a42c0d8 (&type->s_umount_key#55){+.+.}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff88807a42c0d8 (&type->s_umount_key#55){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff88807a42c0d8 (&type->s_umount_key#55){+.+.}-{4:4}, at: deactivate_super fs/super.c:509 [inline]
 #0: ffff88807a42c0d8 (&type->s_umount_key#55){+.+.}-{4:4}, at: deactivate_super+0xdf/0x110 fs/super.c:506
 #1: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:576
3 locks held by syz.0.2883/20990:
 #0: ffff88807828b0b0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff88802b266450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
3 locks held by syz.9.2896/21087:
 #0: ffff88802b307430 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff888047cf2450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
3 locks held by syz.8.2919/21222:
 #0: ffff8880782bad30 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff888027672450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
2 locks held by syz-executor/21244:
 #0: ffff8880994b80d8 (&type->s_umount_key#55){+.+.}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff8880994b80d8 (&type->s_umount_key#55){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff8880994b80d8 (&type->s_umount_key#55){+.+.}-{4:4}, at: deactivate_super fs/super.c:509 [inline]
 #0: ffff8880994b80d8 (&type->s_umount_key#55){+.+.}-{4:4}, at: deactivate_super+0xdf/0x110 fs/super.c:506
 #1: ffffffff8ec6f080 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:576
5 locks held by syz-executor/21363:
 #0: ffff88809c8a8ea0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_do_close+0x26/0xb0 net/bluetooth/hci_core.c:497
 #1: ffff88809c8a80b8 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x37e/0x13c0 net/bluetooth/hci_sync.c:5393
 #2: ffffffff908c9520 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2148 [inline]
 #2: ffffffff908c9520 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_hash_flush+0xbb/0x280 net/bluetooth/hci_conn.c:2733
 #3: ffff88809fdefaf8 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x95/0x710 net/bluetooth/l2cap_core.c:1778
 #4: ffffffff8e7f1968 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x19e/0x3c0 kernel/rcu/tree_exp.h:343
2 locks held by syz.4.3004/21782:
 #0: ffffffff906261c8 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff9063edc0 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline]
 #1: ffffffff9063edc0 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x7ec/0xab0 net/core/net_namespace.c:248
3 locks held by syz.4.3004/21783:
 #0: ffffffff906261c8 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff9063edc0 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline]
 #1: ffffffff9063edc0 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x7ec/0xab0 net/core/net_namespace.c:248
 #2: ffffffff8e7f1968 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x27f/0x3c0 kernel/rcu/tree_exp.h:311

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
 nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:122
 nmi_trigger_cpumask_backtrace+0x21c/0x2a0 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+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xcb1/0x1030 kernel/hung_task.c:561
 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
 </TASK>