INFO: task syz.0.5344:32027 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.5344      state:D stack:27736 pid:32027 tgid:32026 ppid:28899  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:7026
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7083
 __mutex_lock_common kernel/locking/mutex.c:676 [inline]
 __mutex_lock+0x818/0x1060 kernel/locking/mutex.c:760
 expkey_flush+0x20/0x90 fs/nfsd/export.c:250
 write_flush.constprop.0+0x2af/0x3d0 net/sunrpc/cache.c:1550
 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:850 [inline]
 do_loop_readv_writev fs/read_write.c:835 [inline]
 vfs_writev+0x5df/0xde0 fs/read_write.c:1059
 do_writev+0x132/0x340 fs/read_write.c:1103
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc6e998eec9
RSP: 002b:00007fc6ea7a1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00007fc6e9be5fa0 RCX: 00007fc6e998eec9
RDX: 000000000000000a RSI: 0000200000000200 RDI: 0000000000000003
RBP: 00007fc6e9a11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc6e9be6038 R14: 00007fc6e9be5fa0 R15: 00007ffe629cead8
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e3c42e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e3c42e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:867 [inline]
 #0: ffffffff8e3c42e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775
1 lock held by klogd/5185:
 #0: ffff8880b843a4d8 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x29/0x130 kernel/sched/core.c:638
2 locks held by syz.6.5341/32010:
 #0: ffffffff901a2390 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e7ecdc8 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xd5/0x1b10 fs/nfsd/nfsctl.c:1880
3 locks held by syz.0.5344/32027:
 #0: ffff888079d2a2b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2a2/0x370 fs/file.c:1232
 #1: ffff88803091a420 (sb_writers#3){.+.+}-{0:0}, at: do_writev+0x132/0x340 fs/read_write.c:1103
 #2: ffffffff8e7ecdc8 (nfsd_mutex){+.+.}-{4:4}, at: expkey_flush+0x20/0x90 fs/nfsd/export.c:250

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:332 [inline]
 watchdog+0xf3f/0x1170 kernel/hung_task.c:495
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x675/0x7d0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:__sanitizer_cov_trace_pc+0x41/0x70 kernel/kcov.c:217
Code: a9 00 01 ff 00 74 1d f6 c4 01 74 43 a9 00 00 0f 00 75 3c a9 00 00 f0 00 75 35 8b 82 7c 16 00 00 85 c0 74 2b 8b 82 58 16 00 00 <83> f8 02 75 20 48 8b 8a 60 16 00 00 8b 92 5c 16 00 00 48 8b 01 48
RSP: 0018:ffffffff8e007cf8 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81a9271d
RDX: ffffffff8e097a00 RSI: ffffffff81a92732 RDI: 0000000000000001
RBP: ffffffff93a46c80 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000010 R11: 0000000000000001 R12: 0000000000000002
R13: ffff8880b84285f8 R14: 0000000000000010 R15: ffff8880b8427d00
FS:  0000000000000000(0000) GS:ffff8881249e1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005576ad85ca38 CR3: 00000000281aa000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 get_target_base kernel/time/hrtimer.c:224 [inline]
 switch_hrtimer_base kernel/time/hrtimer.c:251 [inline]
 __hrtimer_start_range_ns kernel/time/hrtimer.c:1257 [inline]
 hrtimer_start_range_ns+0x532/0xfd0 kernel/time/hrtimer.c:1322
 hrtimer_start_expires include/linux/hrtimer.h:273 [inline]
 tick_nohz_restart kernel/time/tick-sched.c:845 [inline]
 tick_nohz_restart_sched_tick+0x1c4/0x2f0 kernel/time/tick-sched.c:1103
 tick_nohz_idle_update_tick kernel/time/tick-sched.c:1427 [inline]
 tick_nohz_idle_exit+0x21f/0x2e0 kernel/time/tick-sched.c:1470
 do_idle+0x29d/0x500 kernel/sched/idle.c:343
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:428
 rest_init+0x16b/0x2b0 init/main.c:757
 start_kernel+0x3f6/0x4e0 init/main.c:1111
 x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0x130/0x190 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x148
 </TASK>