syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4591
	(detected by 0, t=10502 jiffies, g=13585, q=531)
task:syz.1.84        state:R  running task     stack:22576 pid: 4591 ppid:  4186 flags:0x0000400e
Call Trace:
 <TASK>
 </TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10499 jiffies! g13585 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: 	Possible timer handling issue on cpu=1 timer-softirq=7496
rcu: rcu_preempt kthread starved for 10500 jiffies! g13585 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:27888 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:2117
 rcu_gp_fqs_loop+0x2be/0x11d0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9b/0x370 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: 4591 Comm: syz.1.84 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:preempt_count_sub+0x4f/0x160 kernel/sched/core.c:5541
Code: 36 4d db 14 00 75 25 65 8b 05 75 0d b0 7e 89 c1 81 e1 ff ff ff 7f 39 cf 7f 25 81 ff ff 00 00 00 0f 93 c1 84 c0 0f 95 c0 08 c8 <74> 53 65 8b 05 50 0d b0 7e f7 df 65 01 3d 47 0d b0 7e 5b 5d c3 e8
RSP: 0018:ffffc90000dd0ca8 EFLAGS: 00000002
RAX: 0000000000010101 RBX: dffffc0000000000 RCX: 0000000000010101
RDX: 1ffffffff1e1d208 RSI: ffffffff8a79f960 RDI: 0000000000010000
RBP: ffffc90000dd0d48 R08: ffffffff8f0e9048 R09: ffffffff8f0e9058
R10: ffffffff8f0e9050 R11: ffffffff8f0e9043 R12: dffffc0000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 1ffff920001ba198
FS:  00007f001c9386c0(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3108f7 CR3: 0000000076c50000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 __irq_exit_rcu+0xa3/0x230 kernel/softirq.c:657
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_irq_work arch/x86/kernel/irq_work.c:17 [inline]
 sysvec_irq_work+0x4f/0xc0 arch/x86/kernel/irq_work.c:17
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:ffs arch/x86/include/asm/bitops.h:297 [inline]
RIP: 0010:handle_softirqs+0x1a9/0x830 kernel/softirq.c:564
Code: 24 78 44 89 64 24 28 0f b7 db 48 c7 c7 80 0f 2a 8a e8 5b 38 73 08 65 66 c7 05 61 57 ba 7e 00 00 e8 2c 0b 36 00 fb 89 5c 24 34 <b8> ff ff ff ff 0f bc 44 24 34 41 89 c5 41 ff c5 0f 85 d2 00 00 00
RSP: 0018:ffffc90000dd0e20 EFLAGS: 00000282
RAX: a91e8cf12ce04a00 RBX: 0000000000000200 RCX: a91e8cf12ce04a00
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f980
RBP: ffffc90000dd0f30 R08: ffffffff901d40cf R09: 1ffffffff203a819
R10: dffffc0000000000 R11: fffffbfff203a81a R12: 000000000000000a
R13: 0000000000000000 R14: ffff888074491dc0 R15: dffffc0000000000
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 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:rcu_read_unlock_special+0x3c/0x4a0 kernel/rcu/tree_plugin.h:625
Code: 81 ec a0 00 00 00 65 48 8b 04 25 28 00 00 00 48 89 84 24 80 00 00 00 49 bd 00 00 00 00 00 fc ff df 48 c7 44 24 20 b3 8a b5 41 <48> c7 44 24 28 79 e3 bf 8b 48 c7 44 24 30 40 7d 65 81 48 8d 5c 24
RSP: 0018:ffffc9000334f640 EFLAGS: 00000282
RAX: a91e8cf12ce04a00 RBX: ffff8880744921fc RCX: 0000000000080000
RDX: ffffc90003ce3000 RSI: 000000000007ffff RDI: ffff888074491dc0
RBP: ffffc9000334f720 R08: dffffc0000000000 R09: 1ffffffff203a818
R10: dffffc0000000000 R11: fffffbfff203a819 R12: 1ffff1100e89243f
R13: dffffc0000000000 R14: ffff888074492200 R15: dffffc0000000000
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 inet_twsk_purge+0x7a2/0x840 net/ipv4/inet_timewait_sock.c:309
 ops_exit_list net/core/net_namespace.c:177 [inline]
 setup_net+0x844/0xa10 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+0x1834/0x3e20 kernel/fork.c:2293
 kernel_clone+0x23f/0x990 kernel/fork.c:2679
 __do_sys_clone kernel/fork.c:2796 [inline]
 __se_sys_clone kernel/fork.c:2780 [inline]
 __x64_sys_clone+0x19a/0x210 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: 0033:0x7f001e6de819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f001c937fd8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f001e957fa0 RCX: 00007f001e6de819
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040800000
RBP: 00007f001e774c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f001e958038 R14: 00007f001e957fa0 R15: 00007fff3fe034d8
 </TASK>