syzbot

INFO: task syz.3.996:11220 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.3.996       state:D stack:26872 pid:11220 tgid:11219 ppid:5625   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: 0033:0x7f8f3319de59
RSP: 002b:00007f8f34026028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007f8f33425fa0 RCX: 00007f8f3319de59
RDX: 000000000000000a RSI: 0000200000000240 RDI: 0000000000000003
RBP: 00007f8f33233e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8f33426038 R14: 00007f8f33425fa0 R15: 00007ffdbd24e818
 </TASK>
INFO: task syz.3.996:11221 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.3.996       state:D stack:26056 pid:11221 tgid:11219 ppid:5625   task_flags:0x580140 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
 fdget_pos+0x2aa/0x380 fs/file.c:1259
 class_fd_pos_constructor include/linux/file.h:85 [inline]
 ksys_read+0x71/0x250 fs/read_write.c:707
 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: 0033:0x7f8f3319de59
RSP: 002b:00007f8f34005028 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f8f33426090 RCX: 00007f8f3319de59
RDX: 0000000000008080 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f8f33233e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8f33426128 R14: 00007f8f33426090 R15: 00007ffdbd24e818
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/30:
 #0: ffffffff8ebe5f00 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
 #0: ffffffff8ebe5f00 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
 #0: ffffffff8ebe5f00 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
2 locks held by getty/5383:
 #0: ffff8880377110a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc900032332e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14e0 drivers/tty/n_tty.c:2211
2 locks held by syz-executor/5626:
 #0: ffff888026cbe0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff888026cbe0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff888026cbe0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: deactivate_super fs/super.c:509 [inline]
 #0: ffff888026cbe0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: deactivate_super+0xdf/0x110 fs/super.c:506
 #1: ffffffff8f06f220 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:576
4 locks held by kworker/u10:20/8844:
 #0: ffff88801caf6140 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc9000327fd08 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffffffff90a857a8 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xb8/0x920 net/core/net_namespace.c:673
 #3: ffffffff90a9e3c0 (rtnl_mutex){+.+.}-{4:4}, at: cfg80211_pernet_exit+0x17/0x120 net/wireless/core.c:1863
3 locks held by kworker/u10:23/8847:
 #0: ffff888033aac140 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
 #1: ffffc9000339fd08 ((work_completion)(&(&net->ipv6.addr_chk_work)->work)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
 #2: ffffffff90a9e3c0 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #2: ffffffff90a9e3c0 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_verify_work+0x12/0x30 net/ipv6/addrconf.c:4769
2 locks held by syz.1.977/11093:
 #0: ffffffff90b4cfc8 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8f06f220 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xd5/0x1a80 fs/nfsd/nfsctl.c:1964
3 locks held by syz.3.996/11220:
 #0: ffff888037da07f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff88802ae8e450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8f06f220 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
1 lock held by syz.3.996/11221:
 #0: ffff888037da07f0 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
3 locks held by syz.0.1025/11368:
 #0: ffff888077492d30 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
 #1: ffff88807887a450 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x13e/0x340 fs/read_write.c:1104
 #2: ffffffff8f06f220 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x18/0x90 fs/nfsd/export.c:253
2 locks held by syz-executor/11461:
 #0: ffff88807905c0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff88807905c0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff88807905c0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: deactivate_super fs/super.c:509 [inline]
 #0: ffff88807905c0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: deactivate_super+0xdf/0x110 fs/super.c:506
 #1: ffffffff8f06f220 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:576
2 locks held by syz-executor/11642:
 #0: ffff88805b65c0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff88805b65c0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff88805b65c0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: deactivate_super fs/super.c:509 [inline]
 #0: ffff88805b65c0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: deactivate_super+0xdf/0x110 fs/super.c:506
 #1: ffffffff8f06f220 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:576
2 locks held by syz.4.1072/11712:
 #0: ffffffff90b4cfc8 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8f06f220 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xd5/0x1a80 fs/nfsd/nfsctl.c:1964
2 locks held by syz-executor/12081:
 #0: ffff8880462fa0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: __super_lock fs/super.c:58 [inline]
 #0: ffff8880462fa0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: __super_lock_excl fs/super.c:73 [inline]
 #0: ffff8880462fa0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: deactivate_super fs/super.c:509 [inline]
 #0: ffff8880462fa0d8 (&type->s_umount_key#57){+.+.}-{4:4}, at: deactivate_super+0xdf/0x110 fs/super.c:506
 #1: ffffffff8f06f220 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:576
1 lock held by syz-executor/12218:
 #0: ffffffff90a9e3c0 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:641 [inline]
 #0: ffffffff90a9e3c0 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x38/0x220 drivers/net/tun.c:3506
3 locks held by syz.7.1375/13548:
 #0: ffffffff90a857a8 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff90a9e3c0 (rtnl_mutex){+.+.}-{4:4}, at: default_device_exit_batch+0x90/0xc10 net/core/dev.c:13079
 #2: ffffffff8ebf19a8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x27f/0x3c0 kernel/rcu/tree_exp.h:311
2 locks held by syz.7.1375/13550:
 #0: ffffffff90a857a8 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff8ebf1878 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x48/0x6d0 kernel/rcu/tree.c:3857
2 locks held by syz.3.1377/13556:
 #0: ffffffff90a857a8 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff90a9e3c0 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x21e/0x780 net/ipv4/ip_tunnel.c:1149
2 locks held by syz.1.1378/13564:
 #0: ffffffff90a857a8 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:575
 #1: ffffffff90a9e3c0 (rtnl_mutex){+.+.}-{4:4}, at: ip_tunnel_init_net+0x21e/0x780 net/ipv4/ip_tunnel.c:1149

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 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>