syzbot

INFO: task syz.5.1900:15422 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.5.1900      state:D stack:27496 pid:15422 tgid:15421 ppid:9898   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5260 [inline]
 __schedule+0x1138/0x5ee0 kernel/sched/core.c:6867
 __schedule_loop kernel/sched/core.c:6949 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6964
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7021
 __mutex_lock_common kernel/locking/mutex.c:692 [inline]
 __mutex_lock+0xc69/0x1ca0 kernel/locking/mutex.c:776
 nfsd_nl_listener_get_doit+0x13e/0x7b0 fs/nfsd/nfsctl.c:2036
 genl_family_rcv_msg_doit+0x209/0x2f0 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+0x158/0x420 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+0x5aa/0x870 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8c8/0xdd0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0xa5d/0xc30 net/socket.c:2592
 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2646
 __sys_sendmsg+0x16d/0x220 net/socket.c:2678
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f300958f7c9
RSP: 002b:00007f300a3e1038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f30097e5fa0 RCX: 00007f300958f7c9
RDX: 0000000000000000 RSI: 0000200000001240 RDI: 0000000000000004
RBP: 00007f3009613f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f30097e6038 R14: 00007f30097e5fa0 R15: 00007ffd6c60d3d8
 </TASK>

Showing all locks held in the system:
3 locks held by kworker/u8:0/12:
1 lock held by khungtaskd/31:
 #0: ffffffff8e3c94a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e3c94a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #0: ffffffff8e3c94a0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775
5 locks held by kworker/u8:38/10280:
 #0: ffff8880b843add8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:647 [inline]
 #0: ffff8880b843add8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x7e/0x130 kernel/sched/core.c:632
 #1: ffff8880b8524608 (psi_seq){-.-.}-{0:0}, at: psi_sched_switch kernel/sched/stats.h:225 [inline]
 #1: ffff8880b8524608 (psi_seq){-.-.}-{0:0}, at: __schedule+0x198b/0x5ee0 kernel/sched/core.c:6861
 #2: ffff8880b843add8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:647 [inline]
 #2: ffff8880b843add8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x7e/0x130 kernel/sched/core.c:632
 #3: ffffffff9aec3498 (&obj_hash[i].lock){-.-.}-{2:2}, at: debug_object_activate+0x14c/0x4c0 lib/debugobjects.c:818
 #4: ffffffff8e3c94a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #4: ffffffff8e3c94a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #4: ffffffff8e3c94a0 (rcu_read_lock){....}-{1:3}, at: class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 #4: ffffffff8e3c94a0 (rcu_read_lock){....}-{1:3}, at: unwind_next_frame+0xbd/0x20b0 arch/x86/kernel/unwind_orc.c:495
2 locks held by syz.0.1842/15053:
 #0: ffffffff901ec210 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e801508 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_threads_set_doit+0x687/0xbc0 fs/nfsd/nfsctl.c:1596
2 locks held by syz.5.1900/15422:
 #0: ffffffff901ec210 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e801508 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_get_doit+0x13e/0x7b0 fs/nfsd/nfsctl.c:2036
2 locks held by syz.7.1967/15786:
 #0: ffff88806789e0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff88806789e0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff88806789e0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super fs/super.c:506 [inline]
 #0: ffff88806789e0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:503
 #1: ffffffff8e801508 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:575
1 lock held by syz.7.1967/15788:
 #0: ffff88806789e0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff88806789e0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: super_lock+0x17d/0x3f0 fs/super.c:121
2 locks held by syz-executor/16012:
 #0: ffff88823bfda0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff88823bfda0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff88823bfda0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super fs/super.c:506 [inline]
 #0: ffff88823bfda0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:503
 #1: ffffffff8e801508 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:575
2 locks held by syz.3.2019/16049:
 #0: ffff88803a7500e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff88803a7500e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff88803a7500e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super fs/super.c:506 [inline]
 #0: ffff88803a7500e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:503
 #1: ffffffff8e801508 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:575
2 locks held by syz-executor/16204:
 #0: ffff88807a83c0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff88807a83c0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff88807a83c0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super fs/super.c:506 [inline]
 #0: ffff88807a83c0e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:503
 #1: ffffffff8e801508 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:575
2 locks held by syz.4.2237/17284:
 #0: ffff88802aa840e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff88802aa840e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff88802aa840e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super fs/super.c:506 [inline]
 #0: ffff88802aa840e0 (&type->s_umount_key#56){+.+.}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:503
 #1: ffffffff8e801508 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:575
2 locks held by getty/17410:
 #0: ffff88803121c0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000d32d2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x1510 drivers/tty/n_tty.c:2211
1 lock held by syz.0.2276/17880:
1 lock held by syz.1.2319/17926:
1 lock held by syz.6.2322/17938:
 #0: ffffffff8e3d4bf8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x284/0x3c0 kernel/rcu/tree_exp.h:311
4 locks held by syz.2.2324/17959:
 #0: ffff888030ae0ec0 (&hdev->req_lock){+.+.}-{4:4}, at: hci_dev_do_close+0x26/0xc0 net/bluetooth/hci_core.c:499
 #1: ffff888030ae00c0 (&hdev->lock){+.+.}-{4:4}, at: hci_dev_close_sync+0x3af/0x1260 net/bluetooth/hci_sync.c:5315
 #2: ffffffff903c3708 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_disconn_cfm include/net/bluetooth/hci_core.h:2143 [inline]
 #2: ffffffff903c3708 (hci_cb_list_lock){+.+.}-{4:4}, at: hci_conn_hash_flush+0xbb/0x290 net/bluetooth/hci_conn.c:2637
 #3: ffff888098c85b38 (&conn->lock#2){+.+.}-{4:4}, at: l2cap_conn_del+0x80/0x760 net/bluetooth/l2cap_core.c:1763
3 locks held by syz.0.2325/17955:
 #0: ffffffff9012f010 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x333/0x7c0 net/core/net_namespace.c:577
 #1: ffffffff90145ae8 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline]
 #1: ffffffff90145ae8 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x7e9/0xab0 net/core/net_namespace.c:248
 #2: ffffffff8e3d4bf8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x1a3/0x3c0 kernel/rcu/tree_exp.h:343

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

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 10/25/2025
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:161 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x133/0x180 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
 watchdog+0xe66/0x1180 kernel/hung_task.c:515
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 17880 Comm: syz.0.2276 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:native_save_fl arch/x86/include/asm/irqflags.h:26 [inline]
RIP: 0010:arch_local_save_flags arch/x86/include/asm/irqflags.h:109 [inline]
RIP: 0010:check_preemption_disabled+0x2c/0xe0 lib/smp_processor_id.c:19
Code: 55 53 48 83 ec 08 65 8b 1d d5 61 3c 08 65 8b 05 ca 61 3c 08 a9 ff ff ff 7f 74 0f 48 83 c4 08 89 d8 5b 5d 41 5c c3 cc cc cc cc <9c> 58 f6 c4 02 74 ea 48 89 fd 65 48 8b 05 8a 61 3c 08 f6 40 2f 04
RSP: 0018:ffffc9000d0870c0 EFLAGS: 00000046
RAX: 0000000080000000 RBX: 0000000000000001 RCX: 0000000068c1bacb
RDX: 0000000000000000 RSI: ffffffff8daa5da7 RDI: ffffffff8bf2b400
RBP: 0000000000000002 R08: 00000000ffffffff R09: 00000000ffffffff
R10: 0000000000000002 R11: ffff888064c5c830 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881249f8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1401789e9c CR3: 000000003237e000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 lockdep_recursion_finish kernel/locking/lockdep.c:470 [inline]
 lock_acquire kernel/locking/lockdep.c:5870 [inline]
 lock_acquire+0x189/0x330 kernel/locking/lockdep.c:5825
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:867 [inline]
 __page_table_check_zero+0xe9/0x4a0 mm/page_table_check.c:138
 page_table_check_free include/linux/page_table_check.h:43 [inline]
 free_pages_prepare mm/page_alloc.c:1434 [inline]
 free_unref_folios+0xa40/0x1610 mm/page_alloc.c:3030
 folios_put_refs+0x4be/0x750 mm/swap.c:1002
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x58f/0x1140 mm/shmem.c:1137
 shmem_truncate_range mm/shmem.c:1249 [inline]
 shmem_evict_inode+0x39e/0xbe0 mm/shmem.c:1379
 evict+0x3c2/0xad0 fs/inode.c:837
 iput_final fs/inode.c:1954 [inline]
 iput.part.0+0x621/0x1190 fs/inode.c:2006
 iput+0x35/0x40 fs/inode.c:1969
 dentry_unlink_inode+0x29c/0x480 fs/dcache.c:467
 __dentry_kill+0x1d0/0x600 fs/dcache.c:670
 finish_dput+0x76/0x480 fs/dcache.c:879
 dput.part.0+0x451/0x570 fs/dcache.c:928
 dput+0x1f/0x30 fs/dcache.c:920
 __fput+0x51c/0xb70 fs/file_table.c:476
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x87f/0x2bd0 kernel/exit.c:971
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1112
 get_signal+0x2671/0x26d0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x8f/0x7a0 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:75 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline]
 irqentry_exit+0x38a/0x8c0 kernel/entry/common.c:196
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x7fbefbb8f7d1
Code: Unable to access opcode bytes at 0x7fbefbb8f7a7.
RSP: 002b:0000000000000007 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007fbefbde5fa0 RCX: 00007fbefbb8f7c9
RDX: 00002000000018c0 RSI: 0000000000000007 RDI: 0000000000000000
RBP: 00007fbefbc13f91 R08: 0000000000000009 R09: 0000000000000000
R10: 0000200000001900 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fbefbde6038 R14: 00007fbefbde5fa0 R15: 00007ffe37e17ae8
 </TASK>