syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	0-....: (1 GPs behind) idle=d3b/1/0x4000000000000000 softirq=50212/50213 fqs=3689 
	(t=10500 jiffies g=71009 q=1628)
rcu: rcu_preempt kthread timer wakeup didn't happen for 358 jiffies! g71009 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=38958
rcu: rcu_preempt kthread starved for 359 jiffies! g71009 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->cpu=1
rcu: 	Unless rcu_preempt kthread gets sufficient CPU time, OOM is now expected behavior.
rcu: RCU grace-period kthread stack dump:
task:rcu_preempt     state:I stack:27528 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11bb/0x4390 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x15c/0x280 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x29e/0x11b0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x98/0x350 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4171 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
RIP: 0010:arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
RIP: 0010:kvm_wait+0x141/0x190 arch/x86/kernel/kvm.c:918
Code: 89 df 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0 75 47 0f b6 1f e8 1f e2 49 00 44 38 e3 75 10 66 90 0f 00 2d c1 68 d4 08 fb f4 <e9> 33 ff ff ff fb e9 2d ff ff ff e8 4f df 6d 08 89 f9 80 e1 07 38
RSP: 0018:ffffc90002def6e0 EFLAGS: 00000246
RAX: c6984307c306cc00 RBX: 0000000000000003 RCX: c6984307c306cc00
RDX: dffffc0000000000 RSI: ffffffff8a0b1be0 RDI: ffffffff8a59e800
RBP: ffffc90002def790 R08: dffffc0000000000 R09: fffffbfff1ff5432
R10: fffffbfff1ff5432 R11: 1ffffffff1ff5431 R12: 0000000000000003
R13: ffff8880b913b154 R14: dffffc0000000000 R15: 1ffff920005bdedc
FS:  0000555563a09500(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd7fc8a7f98 CR3: 000000001e9e3000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 pv_wait arch/x86/include/asm/paravirt.h:597 [inline]
 pv_wait_head_or_lock kernel/locking/qspinlock_paravirt.h:470 [inline]
 __pv_queued_spin_lock_slowpath+0x60f/0x9c0 kernel/locking/qspinlock.c:508
 pv_queued_spin_lock_slowpath arch/x86/include/asm/paravirt.h:585 [inline]
 queued_spin_lock_slowpath+0x43/0x50 arch/x86/include/asm/qspinlock.h:51
 queued_spin_lock include/asm-generic/qspinlock.h:85 [inline]
 do_raw_spin_lock+0x217/0x280 kernel/locking/spinlock_debug.c:115
 spin_lock_bh include/linux/spinlock.h:369 [inline]
 lock_sock_nested+0x68/0x100 net/core/sock.c:3262
 lock_sock include/net/sock.h:1731 [inline]
 tcp_recvmsg+0x32e/0x710 net/ipv4/tcp.c:2562
 inet_recvmsg+0x136/0x1e0 net/ipv4/af_inet.c:868
 sock_recvmsg_nosec net/socket.c:968 [inline]
 sock_recvmsg net/socket.c:986 [inline]
 sock_read_iter+0x2a2/0x340 net/socket.c:1067
 call_read_iter include/linux/fs.h:2167 [inline]
 new_sync_read fs/read_write.c:404 [inline]
 vfs_read+0x725/0xcf0 fs/read_write.c:485
 ksys_read+0x14d/0x250 fs/read_write.c:623
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7ff9a9d8d11d
Code: a8 ff ff ff f7 d8 64 89 02 b8 ff ff ff ff eb bd e8 a8 48 00 00 0f 1f 84 00 00 00 00 00 80 3d 41 d4 22 00 00 74 17 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 5b c3 66 2e 0f 1f 84 00 00 00 00 00 48 83 ec
RSP: 002b:00007ffc5b38e188 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 00007ff9a9d8d11d
RDX: 0000000000001280 RSI: 0000555563a2c4fc RDI: 0000000000000003
RBP: 000000000000107c R08: 00000000000002aa R09: 0038221034362464
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc5b38e5b0
R13: 00000000000022fc R14: 0000555563a2b480 R15: 00007ffc5b38e230
 </TASK>
NMI backtrace for cpu 0
CPU: 0 PID: 18861 Comm: syz.2.3911 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <IRQ>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_single_cpu_backtrace include/linux/nmi.h:166 [inline]
 rcu_dump_cpu_stacks+0x22f/0x380 kernel/rcu/tree_stall.h:349
 print_cpu_stall+0x31d/0x5f0 kernel/rcu/tree_stall.h:633
 check_cpu_stall kernel/rcu/tree_stall.h:727 [inline]
 rcu_pending kernel/rcu/tree.c:3936 [inline]
 rcu_sched_clock_irq+0x6d8/0x1110 kernel/rcu/tree.c:2619
 update_process_times+0x193/0x200 kernel/time/timer.c:1818
 tick_sched_handle kernel/time/tick-sched.c:254 [inline]
 tick_sched_timer+0x37d/0x560 kernel/time/tick-sched.c:1473
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4fe/0xc40 kernel/time/hrtimer.c:1749
 hrtimer_interrupt+0x3bb/0x8d0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1097 [inline]
 __sysvec_apic_timer_interrupt+0x137/0x4a0 arch/x86/kernel/apic/apic.c:1114
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1108
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_acquire+0x1f2/0x3f0 kernel/locking/lockdep.c:5627
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f6 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0018:ffffc90000006740 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: c910313d19f29b00
RDX: 0000000000000000 RSI: ffffffff8a0b2e80 RDI: ffffffff8a59e800
RBP: ffffc90000006858 R08: dffffc0000000000 R09: fffffbfff1ff5419
R10: fffffbfff1ff5419 R11: 1ffffffff1ff5418 R12: ffffffff8c11c720
R13: 1ffff92000000cf4 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 nf_hook+0x9f/0x350 include/linux/netfilter.h:226
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip_output+0x1ea/0x2b0 net/ipv4/ip_output.c:430
 dst_output include/net/dst.h:452 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 __ip_queue_xmit+0x11c3/0x1c00 net/ipv4/ip_output.c:532
 __tcp_transmit_skb+0x1ced/0x31c0 net/ipv4/tcp_output.c:1404
 tcp_validate_incoming+0x13aa/0x1e10 net/ipv4/tcp_input.c:-1
 tcp_rcv_established+0x87a/0x1cb0 net/ipv4/tcp_input.c:6053
 tcp_v4_do_rcv+0x44b/0x9b0 net/ipv4/tcp_ipv4.c:1731
 tcp_v4_rcv+0x268f/0x2cb0 net/ipv4/tcp_ipv4.c:2143
 ip_protocol_deliver_rcu+0x3ad/0x770 net/ipv4/ip_input.c:204
 ip_local_deliver_finish+0x1d5/0x320 net/ipv4/ip_input.c:231
 NF_HOOK+0x2d6/0x360 include/linux/netfilter.h:302
 dst_input include/net/dst.h:462 [inline]
 ip_sublist_rcv_finish net/ipv4/ip_input.c:577 [inline]
 ip_list_rcv_finish net/ipv4/ip_input.c:628 [inline]
 ip_sublist_rcv+0xa1f/0xce0 net/ipv4/ip_input.c:636
 ip_list_rcv+0x3df/0x430 net/ipv4/ip_input.c:671
 __netif_receive_skb_list_ptype net/core/dev.c:5568 [inline]
 __netif_receive_skb_list_core+0x574/0x740 net/core/dev.c:5616
 __netif_receive_skb_list net/core/dev.c:5668 [inline]
 netif_receive_skb_list_internal+0x871/0xb90 net/core/dev.c:5759
 gro_normal_list net/core/dev.c:5913 [inline]
 gro_normal_one net/core/dev.c:5926 [inline]
 napi_skb_finish net/core/dev.c:6263 [inline]
 napi_gro_receive+0x4ef/0xa60 net/core/dev.c:6293
 receive_buf+0x3793/0x5780 drivers/net/virtio_net.c:1240
 virtnet_receive drivers/net/virtio_net.c:1504 [inline]
 virtnet_poll+0x546/0xef0 drivers/net/virtio_net.c:1617
 __napi_poll+0xc0/0x430 net/core/dev.c:7075
 napi_poll net/core/dev.c:7142 [inline]
 net_rx_action+0x4a8/0x9c0 net/core/dev.c:7232
 handle_softirqs+0x328/0x820 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x12f/0x220 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:finish_lock_switch+0x134/0x280 kernel/sched/core.c:4804
Code: be ff ff ff ff e8 ec 75 4e 08 85 c0 74 4a 4d 85 ff 75 66 0f 1f 44 00 00 48 89 df e8 96 da 57 08 e8 11 76 2a 00 fb 48 83 c4 08 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 48 89 df e8 d9 0f fe ff 43 80 3c
RSP: 0018:ffffc900035cf248 EFLAGS: 00000286
RAX: c910313d19f29b00 RBX: ffff8880b903a340 RCX: c910313d19f29b00
RDX: dffffc0000000000 RSI: ffffffff8a0b1be0 RDI: ffffffff8a59e800
RBP: 1ffff11017207613 R08: dffffc0000000000 R09: fffffbfff1ff541a
R10: fffffbfff1ff541a R11: 1ffffffff1ff5419 R12: 1ffff110172075c1
R13: dffffc0000000000 R14: ffff8880b903ae08 R15: 0000000000000000
 finish_task_switch+0x12f/0x640 kernel/sched/core.c:4921
 context_switch kernel/sched/core.c:5052 [inline]
 __schedule+0x11c3/0x4390 kernel/sched/core.c:6395
 preempt_schedule_irq+0xb1/0x150 kernel/sched/core.c:6799
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_acquire+0x1f2/0x3f0 kernel/locking/lockdep.c:5627
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f6 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 66 43 c7 44 3d 09 00 00 43 c6 44 3d 0b
RSP: 0018:ffffc900035cf620 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: c910313d19f29b00
RDX: 0000000000000000 RSI: ffffffff8a0b2e80 RDI: ffffffff8a59e800
RBP: ffffc900035cf740 R08: dffffc0000000000 R09: fffffbfff1ff5419
R10: fffffbfff1ff5419 R11: 1ffffffff1ff5418 R12: ffffffff8c11c720
R13: 1ffff920006b9ed0 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 inet_twsk_purge+0x119/0x810 net/ipv4/inet_timewait_sock.c:268
 ops_exit_list net/core/net_namespace.c:177 [inline]
 setup_net+0x822/0x9f0 net/core/net_namespace.c:365
 copy_net_ns+0x348/0x5b0 net/core/net_namespace.c:503
 create_new_namespaces+0x3d3/0x6f0 kernel/nsproxy.c:110
 copy_namespaces+0x37d/0x3e0 kernel/nsproxy.c:178
 copy_process+0x180f/0x3e00 kernel/fork.c:2293
 kernel_clone+0x219/0x930 kernel/fork.c:2679
 __do_sys_clone kernel/fork.c:2796 [inline]
 __se_sys_clone kernel/fork.c:2780 [inline]
 __x64_sys_clone+0x170/0x1c0 kernel/fork.c:2780
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f8dcd031749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f8dcb297fe8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f8dcd287fa0 RCX: 00007f8dcd031749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000042164000
RBP: 00007f8dcd0b5f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f8dcd288038 R14: 00007f8dcd287fa0 R15: 00007ffd6fcf3ce8
 </TASK>