syzbot

INFO: task syz.2.4556:29367 blocked for more than 143 seconds.
      Tainted: G     U              syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.4556      state:D stack:27208 pid:29367 tgid:29364 ppid:17872  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
 nfsd_nl_rpc_status_get_dumpit+0xb6/0x1170 fs/nfsd/nfsctl.c:1516
 genl_dumpit+0x125/0x230 net/netlink/genetlink.c:1027
 netlink_dump+0x536/0xd30 net/netlink/af_netlink.c:2327
 __netlink_dump_start+0x6d6/0x990 net/netlink/af_netlink.c:2442
 genl_family_rcv_msg_dumpit+0x1e2/0x2e0 net/netlink/genetlink.c:1076
 genl_family_rcv_msg net/netlink/genetlink.c:1192 [inline]
 genl_rcv_msg+0x46e/0x800 net/netlink/genetlink.c:1210
 netlink_rcv_skb+0x155/0x420 net/netlink/af_netlink.c:2552
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
 netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
 netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346
 netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1896
 sock_sendmsg_nosec net/socket.c:714 [inline]
 __sock_sendmsg net/socket.c:729 [inline]
 ____sys_sendmsg+0xa95/0xc70 net/socket.c:2617
 ___sys_sendmsg+0x134/0x1d0 net/socket.c:2671
 __sys_sendmsg+0x16d/0x220 net/socket.c:2703
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fdda1d8eec9
RSP: 002b:00007fdda2bf4038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fdda1fe5fa0 RCX: 00007fdda1d8eec9
RDX: 0000000020000000 RSI: 0000200000000140 RDI: 0000000000000003
RBP: 00007fdda1e11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fdda1fe6038 R14: 00007fdda1fe5fa0 R15: 00007ffd41cc9938
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e1c3320 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e1c3320 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8e1c3320 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6775
3 locks held by kworker/u8:8/1163:
 #0: ffff88801bef6948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc90003dbfd10 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
 #2: ffffffff8feb53d0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xad/0x8b0 net/core/net_namespace.c:669
3 locks held by kworker/1:2/1700:
 #0: ffff88801b081148 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffff8880b8724088 (psi_seq){-.-.}-{0:0}, at: psi_sched_switch kernel/sched/stats.h:220 [inline]
 #1: ffff8880b8724088 (psi_seq){-.-.}-{0:0}, at: __schedule+0x1861/0x5de0 kernel/sched/core.c:6923
 #2: ffff8880b8725b18 (&base->lock){-.-.}-{2:2}, at: lock_timer_base+0x127/0x1d0 kernel/time/timer.c:1004
1 lock held by udevd/5210:
2 locks held by kworker/u9:3/5848:
 #0: ffff888143b78148 ((wq_completion)nbd0-recv){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc9000433fd10 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
3 locks held by kworker/u8:13/14503:
 #0: ffff8880302e1948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc900191d7d10 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
 #2: ffffffff8fecb788 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:130 [inline]
 #2: ffffffff8fecb788 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x120/0x14e0 net/ipv6/addrconf.c:4194
2 locks held by kworker/u9:4/20041:
 #0: ffff888143be8148 ((wq_completion)nbd1-recv){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc900049e7d10 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
2 locks held by syz.3.4384/26790:
 #0: ffffffff8ff6edd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e5e4d68 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xd5/0x1b10 fs/nfsd/nfsctl.c:1919
2 locks held by kworker/u9:0/28781:
 #0: ffff888025c16148 ((wq_completion)nbd2-recv){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc90013acfd10 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
3 locks held by syz.2.4556/29367:
 #0: ffffffff8ff6edd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffff8880623456d8 (nlk_cb_mutex-GENERIC){+.+.}-{4:4}, at: __netlink_dump_start+0x150/0x990 net/netlink/af_netlink.c:2406
 #2: ffffffff8e5e4d68 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_rpc_status_get_dumpit+0xb6/0x1170 fs/nfsd/nfsctl.c:1516
2 locks held by kworker/u9:2/29594:
 #0: ffff888025d3e148 ((wq_completion)nbd3-recv){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc90013d0fd10 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
2 locks held by syz-executor/30143:
 #0: ffff8880405ea0e0 (&type->s_umount_key#52){++++}-{4:4}, at: __super_lock fs/super.c:57 [inline]
 #0: ffff8880405ea0e0 (&type->s_umount_key#52){++++}-{4:4}, at: __super_lock_excl fs/super.c:72 [inline]
 #0: ffff8880405ea0e0 (&type->s_umount_key#52){++++}-{4:4}, at: deactivate_super fs/super.c:506 [inline]
 #0: ffff8880405ea0e0 (&type->s_umount_key#52){++++}-{4:4}, at: deactivate_super+0xd6/0x100 fs/super.c:503
 #1: ffffffff8e5e4d68 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_shutdown_threads+0x5b/0xf0 fs/nfsd/nfssvc.c:596
2 locks held by getty/32715:
 #0: ffff88814d3d30a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc900032a42f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x14f0 drivers/tty/n_tty.c:2222
1 lock held by syz-executor/32742:
 #0: ffffffff8fecb788 (rtnl_mutex){+.+.}-{4:4}, at: tun_detach drivers/net/tun.c:634 [inline]
 #0: ffffffff8fecb788 (rtnl_mutex){+.+.}-{4:4}, at: tun_chr_close+0x38/0x230 drivers/net/tun.c:3436
3 locks held by kworker/0:5/1962:
 #0: ffff88801b080d48 ((wq_completion)events#2){+.+.}-{0:0}, at: process_one_work+0x12a2/0x1b70 kernel/workqueue.c:3238
 #1: ffffc9000dbdfd10 ((fqdir_free_work).work){+.+.}-{0:0}, at: process_one_work+0x929/0x1b70 kernel/workqueue.c:3239
 #2: ffffffff8e1ce780 (rcu_state.barrier_mutex){+.+.}-{4:4}, at: rcu_barrier+0x48/0x6e0 kernel/rcu/tree.c:3815
2 locks held by syz.1.4871/2807:
 #0: ffffffff8ff6edd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e5e4d68 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xd5/0x1b10 fs/nfsd/nfsctl.c:1919
2 locks held by syz.1.4871/2819:
 #0: ffffffff8ff6edd0 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1218
 #1: ffffffff8e5e4d68 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_listener_set_doit+0xd5/0x1b10 fs/nfsd/nfsctl.c:1919
1 lock held by syz-executor/3474:
 #0: ffffffff8e1ce8b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x1a3/0x3c0 kernel/rcu/tree_exp.h:343
1 lock held by syz.4.4940/4229:
 #0: ffffffff8feb53d0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x2d6/0x690 net/core/net_namespace.c:576

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Tainted: G     U              syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
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:328 [inline]
 watchdog+0xf0e/0x1260 kernel/hung_task.c:491
 kthread+0x3c2/0x780 kernel/kthread.c:463
 ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148
 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: 14502 Comm: kworker/u8:12 Tainted: G     U              syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:match_held_lock+0x5f/0xc0 kernel/locking/lockdep.c:5307
Code: 28 5c 8f 48 2d 60 39 81 95 48 c1 f8 03 48 0f af c2 0f b7 53 20 5b 81 e2 ff 1f 00 00 48 39 d0 0f 94 c0 0f b6 c0 e9 c1 01 03 00 <b8> 01 00 00 00 5b c3 cc cc cc cc 31 f6 e8 2f fe ff ff 48 85 c0 75
RSP: 0018:ffffc900191f75f0 EFLAGS: 00000046
RAX: 0000000000000014 RBX: ffff88802c524850 RCX: ffffc900191f763c
RDX: 0000000000000005 RSI: ffffffff8e1c3320 RDI: ffff88802c524850
RBP: 0000000000000004 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000004 R11: 000000000005e4b3 R12: ffffffff8e1c3320
R13: ffffc900191f763c R14: 0000000000000005 R15: 0000000000000005
FS:  0000000000000000(0000) GS:ffff888124e79000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b310e5ff8 CR3: 000000007dd96000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 find_held_lock+0x2b/0x80 kernel/locking/lockdep.c:5350
 __lock_release kernel/locking/lockdep.c:5535 [inline]
 lock_release+0xe4/0x2f0 kernel/locking/lockdep.c:5889
 rcu_lock_release include/linux/rcupdate.h:341 [inline]
 rcu_read_unlock include/linux/rcupdate.h:871 [inline]
 class_rcu_destructor include/linux/rcupdate.h:1169 [inline]
 unwind_next_frame+0x3f9/0x20a0 arch/x86/kernel/unwind_orc.c:479
 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
 kasan_save_track+0x14/0x30 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:330 [inline]
 __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:356
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4191 [inline]
 slab_alloc_node mm/slub.c:4240 [inline]
 kmem_cache_alloc_node_noprof+0x1d5/0x3b0 mm/slub.c:4292
 __alloc_skb+0x2b2/0x380 net/core/skbuff.c:659
 alloc_skb include/linux/skbuff.h:1336 [inline]
 nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:763 [inline]
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:820 [inline]
 nsim_dev_trap_report_work+0x2b1/0xcf0 drivers/net/netdevsim/dev.c:866
 process_one_work+0x9cf/0x1b70 kernel/workqueue.c:3263
 process_scheduled_works kernel/workqueue.c:3346 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3427
 kthread+0x3c2/0x780 kernel/kthread.c:463
 ret_from_fork+0x56d/0x730 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>