syzbot

INFO: task syz.1.1026:10703 blocked for more than 143 seconds.
      Tainted: G     U    I  L      syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.1026      state:D stack:27464 pid:10703 tgid:10702 ppid:5822   task_flags:0x400040 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5298 [inline]
 __schedule+0xfee/0x6120 kernel/sched/core.c:6911
 __schedule_loop kernel/sched/core.c:6993 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7008
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:7065
 __mutex_lock_common kernel/locking/mutex.c:692 [inline]
 __mutex_lock+0xc9a/0x1b90 kernel/locking/mutex.c:776
 nfsd_nl_version_get_doit+0x18c/0x7f0 fs/nfsd/nfsctl.c:1818
 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:2550
 genl_rcv+0x28/0x40 net/netlink/genetlink.c:1218
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x8b0/0xda0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x9e1/0xb70 net/socket.c:2592
 ___sys_sendmsg+0x190/0x1e0 net/socket.c:2646
 __sys_sendmsg+0x170/0x220 net/socket.c:2678
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x106/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd27099c799
RSP: 002b:00007fd271879028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd270c15fa0 RCX: 00007fd27099c799
RDX: 0000000020008040 RSI: 00002000000000c0 RDI: 0000000000000002
RBP: 00007fd270a32c99 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd270c16038 R14: 00007fd270c15fa0 R15: 00007ffe42dab638
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e7e74e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 #0: ffffffff8e7e74e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
 #0: ffffffff8e7e74e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
2 locks held by getty/5579:
 #0: ffff8880389f20a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000332b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x1500 drivers/tty/n_tty.c:2211
4 locks held by kworker/u8:10/7469:
 #0: ffff88801c6ae948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x1310/0x19a0 kernel/workqueue.c:3251
 #1: ffffc9000445fd08 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x988/0x19a0 kernel/workqueue.c:3252
 #2: ffffffff905fbbd0 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xb8/0x920 net/core/net_namespace.c:675
 #3: ffffffff90614428 (rtnl_mutex){+.+.}-{4:4}, at: ops_exit_rtnl_list net/core/net_namespace.c:173 [inline]
 #3: ffffffff90614428 (rtnl_mutex){+.+.}-{4:4}, at: ops_undo_list+0x7ec/0xab0 net/core/net_namespace.c:248
2 locks held by syz.0.1017/10652:
 #0: ffffffff906c0790 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8ec58228 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_threads_set_doit+0x6c1/0xc00 fs/nfsd/nfsctl.c:1597
2 locks held by syz.1.1026/10703:
 #0: ffffffff906c0790 (cb_lock){++++}-{4:4}, at: genl_rcv+0x19/0x40 net/netlink/genetlink.c:1217
 #1: ffffffff8ec58228 (nfsd_mutex){+.+.}-{4:4}, at: nfsd_nl_version_get_doit+0x18c/0x7f0 fs/nfsd/nfsctl.c:1818
2 locks held by syz.2.1556/13521:
 #0: ffffffff905fbbd0 (pernet_ops_rwsem){++++}-{4:4}, at: copy_net_ns+0x451/0x7c0 net/core/net_namespace.c:577
 #1: ffffffff90614428 (rtnl_mutex){+.+.}-{4:4}, at: caif_exit_net+0x60/0x3a0 net/caif/caif_dev.c:528
2 locks held by syz.3.1562/13546:
 #0: ffffffff90614428 (rtnl_mutex){+.+.}-{4:4}, at: ppp_release+0x16f/0x230 drivers/net/ppp/ppp_generic.c:413
 #1: ffffffff8e7f30f8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x27f/0x3c0 kernel/rcu/tree_exp.h:311

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Tainted: G     U    I  L      syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER, [I]=FIRMWARE_WORKAROUND, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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:113
 nmi_trigger_cpumask_backtrace+0x1d7/0x230 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+0x141/0x190 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:346 [inline]
 watchdog+0xd25/0x1050 kernel/hung_task.c:515
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x754/0xd80 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: 13549 Comm: syz.3.1562 Tainted: G     U    I  L      syzkaller #0 PREEMPT(full) 
Tainted: [U]=USER, [I]=FIRMWARE_WORKAROUND, [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:trace_local_timer_exit arch/x86/include/asm/trace/irq_vectors.h:40 [inline]
RIP: 0010:__sysvec_apic_timer_interrupt+0x13f/0x490 arch/x86/kernel/apic/apic.c:1063
Code: 83 fb 07 0f 87 69 02 00 00 48 89 d8 be 08 00 00 00 48 c1 e8 06 48 8d 3c c5 10 c0 d9 90 e8 c9 bb be 00 48 0f a3 1d a1 c9 24 0f <0f> 82 4b 02 00 00 48 c7 c7 80 e5 aa 8b e8 8f 8e d8 09 48 c7 c7 c0
RSP: 0018:ffffc90000007fd8 EFLAGS: 00000047
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff81b4f667
RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffffff90d9c010
RBP: 0000000000000000 R08: 0000000000000000 R09: fffffbfff21b3802
R10: ffffffff90d9c017 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88812434a000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000005bd000 CR3: 0000000031c08000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1056
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__raw_spin_unlock_irq include/linux/spinlock_api_smp.h:188 [inline]
RIP: 0010:_raw_spin_unlock_irq+0x29/0x50 kernel/locking/spinlock.c:202
Code: 90 f3 0f 1e fa 53 48 8b 74 24 08 48 89 fb 48 83 c7 18 e8 7a 11 54 f6 48 89 df e8 62 61 54 f6 e8 0d c7 7f f6 fb bf 01 00 00 00 <e8> a2 85 44 f6 65 8b 05 cb 0e 7d 08 85 c0 74 06 5b c3 cc cc cc cc
RSP: 0018:ffffc90006f27338 EFLAGS: 00000206
RAX: 00000000000013d1 RBX: ffff88806ceaaa78 RCX: 0000000000000040
RDX: 0000000000000000 RSI: ffffffff8de7fbba RDI: 0000000000000001
RBP: ffff88806ceaaa70 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: ffff88806ceaaa78
R13: 0000000000000000 R14: 0000000000000000 R15: 000000000000000f
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 filemap_remove_folio+0x104/0x270 mm/filemap.c:258
 truncate_inode_folio+0x49/0x70 mm/truncate.c:176
 shmem_undo_range+0x3ae/0x1570 mm/shmem.c:1145
 shmem_truncate_range mm/shmem.c:1277 [inline]
 shmem_evict_inode+0x39e/0xbd0 mm/shmem.c:1407
 evict+0x3c2/0xad0 fs/inode.c:846
 iput_final fs/inode.c:1966 [inline]
 iput.part.0+0x605/0xf50 fs/inode.c:2015
 iput+0x35/0x40 fs/inode.c:1981
 dentry_unlink_inode+0x2a1/0x490 fs/dcache.c:467
 __dentry_kill+0x1d0/0x600 fs/dcache.c:670
 finish_dput+0x76/0x480 fs/dcache.c:879
 dput.part.0+0x456/0x570 fs/dcache.c:928
 dput+0x1f/0x30 fs/dcache.c:920
 __fput+0x519/0xb40 fs/file_table.c:477
 task_work_run+0x150/0x240 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x8b8/0x2b60 kernel/exit.c:976
 do_group_exit+0xd5/0x2a0 kernel/exit.c:1118
 get_signal+0x1ec7/0x21e0 kernel/signal.c:3034
 arch_do_signal_or_restart+0x91/0x770 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x4a0 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x668/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f055dd9c799
Code: Unable to access opcode bytes at 0x7f055dd9c76f.
RSP: 002b:00007f055ec270e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f055e016098 RCX: 00007f055dd9c799
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f055e016098
RBP: 00007f055e016090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f055e016128 R14: 00007ffd05ac1d00 R15: 00007ffd05ac1de8
 </TASK>