syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5953/2:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=12101, q=4163 ncpus=2)
task:syz.1.8         state:R  running task     stack:24344 pid:5953  tgid:5953  ppid:5836   task_flags:0x2040004c flags:0x00080001
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1190/0x5de0 kernel/sched/core.c:6929
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7256
 irqentry_exit+0x36/0x90 kernel/entry/common.c:211
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:native_irq_disable arch/x86/include/asm/irqflags.h:37 [inline]
RIP: 0010:arch_local_irq_disable arch/x86/include/asm/irqflags.h:114 [inline]
RIP: 0010:arch_local_irq_save arch/x86/include/asm/irqflags.h:128 [inline]
RIP: 0010:lock_acquire kernel/locking/lockdep.c:5864 [inline]
RIP: 0010:lock_acquire+0x133/0x350 kernel/locking/lockdep.c:5825
Code: 00 65 8b 05 d7 1d 09 12 85 c0 0f 85 a2 00 00 00 65 48 8b 05 17 dc 08 12 8b 90 2c 0b 00 00 85 d2 0f 85 8c 00 00 00 9c 8f 04 24 <fa> 48 c7 c7 f8 84 b1 8d e8 30 47 c5 09 45 89 e0 89 e9 44 89 ea 65
RSP: 0018:ffffc900046eeb10 EFLAGS: 00000246
RAX: ffff8880281bdac0 RBX: ffffffff8e3c45e0 RCX: 0000000000000001
RDX: 0000000000000000 RSI: ffffffff816bb3e1 RDI: fffffbfff1c788bc
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000037e43 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:867 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0xd1/0x20a0 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:56
 kasan_record_aux_stack+0xa7/0xc0 mm/kasan/generic.c:559
 slab_free_hook mm/slub.c:2504 [inline]
 slab_free mm/slub.c:6642 [inline]
 kmem_cache_free+0x15e/0x6c0 mm/slub.c:6752
 mempool_free+0x102/0x750 mm/mempool.c:576
 bio_put_percpu_cache block/bio.c:805 [inline]
 bio_put+0x355/0x5b0 block/bio.c:824
 bio_endio+0x713/0x860 block/bio.c:1672
 blk_update_request+0x93e/0x15f0 block/blk-mq.c:998
 blk_mq_end_request+0x4f/0x90 block/blk-mq.c:1160
 blk_mq_complete_request block/blk-mq.c:1338 [inline]
 blk_mq_complete_request+0x8b/0xb0 block/blk-mq.c:1335
 nullb_complete_cmd drivers/block/null_blk/main.c:1402 [inline]
 null_handle_cmd drivers/block/null_blk/main.c:1454 [inline]
 null_queue_rq+0xb69/0xfd0 drivers/block/null_blk/main.c:1693
 null_queue_rqs+0xe9/0x2f0 drivers/block/null_blk/main.c:1707
 __blk_mq_flush_list block/blk-mq.c:2837 [inline]
 __blk_mq_flush_list+0x9a/0xc0 block/blk-mq.c:2833
 blk_mq_dispatch_queue_requests+0x184/0x7b0 block/blk-mq.c:2882
 blk_mq_flush_plug_list+0x1f2/0x600 block/blk-mq.c:2970
 blk_add_rq_to_plug+0x1ca/0x540 block/blk-mq.c:1399
 blk_mq_submit_bio+0x1ecc/0x3380 block/blk-mq.c:3222
 __submit_bio+0x3cf/0x690 block/blk-core.c:637
 __submit_bio_noacct_mq block/blk-core.c:724 [inline]
 submit_bio_noacct_nocheck+0x53d/0xc10 block/blk-core.c:755
 submit_bio_noacct+0x5bd/0x1f60 block/blk-core.c:879
 __block_write_full_folio+0x735/0xe00 fs/buffer.c:1933
 block_write_full_folio+0x341/0x400 fs/buffer.c:2753
 blkdev_writepages+0xb8/0x140 block/fops.c:491
 do_writepages+0x27a/0x600 mm/page-writeback.c:2604
 filemap_fdatawrite_wbc mm/filemap.c:389 [inline]
 filemap_fdatawrite_wbc+0x104/0x160 mm/filemap.c:379
 __filemap_fdatawrite_range+0xb9/0x100 mm/filemap.c:422
 filemap_write_and_wait_range mm/filemap.c:694 [inline]
 filemap_write_and_wait_range+0xa3/0x130 mm/filemap.c:685
 filemap_write_and_wait include/linux/pagemap.h:68 [inline]
 sync_blockdev block/bdev.c:260 [inline]
 sync_blockdev block/bdev.c:256 [inline]
 bdev_release+0x4d3/0x6d0 block/bdev.c:1126
 blkdev_release+0x15/0x20 block/fops.c:709
 __fput+0x402/0xb70 fs/file_table.c:468
 task_work_run+0x150/0x240 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x86f/0x2bf0 kernel/exit.c:966
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1107
 __do_sys_exit_group kernel/exit.c:1118 [inline]
 __se_sys_exit_group kernel/exit.c:1116 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1116
 x64_sys_call+0x150b/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
 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: 0033:0x7fc82278f6c9
RSP: 002b:00007ffed35a5458 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc82278f6c9
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffed35a54bc R08: 0000001ed35a554f R09: 00000000000927c0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000002
R13: 00000000000927c0 R14: 000000000001b5c9 R15: 00007ffed35a5510
 </TASK>
rcu: rcu_preempt kthread starved for 1734 jiffies! g12101 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->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:R  running task     stack:28968 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
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_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285
 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>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:lockdep_rtnl_is_held+0x29/0x40 net/core/rtnetlink.c:182
Code: 90 f3 0f 1e fa 53 e8 16 2d 86 f8 be ff ff ff ff 48 c7 c7 08 ae 0e 90 e8 d5 5a 27 02 31 ff 89 c3 89 c6 e8 3a 28 86 f8 85 db 5b <0f> 95 c0 e9 7f 5c 2a 02 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40
RSP: 0018:ffffc90000a083b8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: ffffffff89362b16
RDX: ffff88801d2ddac0 RSI: 0000000000000000 RDI: 0000000000000005
RBP: ffffc90000a084c8 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff888032f98cdf
R13: ffff888032f98cc8 R14: 1ffff92000141087 R15: ffff88801db37000
FS:  0000000000000000(0000) GS:ffff888124b0d000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2513dc7000 CR3: 00000000722cc000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 __in6_dev_get include/net/addrconf.h:347 [inline]
 ip6_ignore_linkdown include/net/addrconf.h:443 [inline]
 find_match+0x34b/0x15d0 net/ipv6/route.c:780
 __find_rr_leaf+0x140/0xe00 net/ipv6/route.c:868
 find_rr_leaf net/ipv6/route.c:889 [inline]
 rt6_select net/ipv6/route.c:933 [inline]
 fib6_table_lookup+0x57c/0xa30 net/ipv6/route.c:2233
 ip6_pol_route+0x1cc/0x1230 net/ipv6/route.c:2269
 pol_lookup_func include/net/ip6_fib.h:617 [inline]
 fib6_rule_lookup+0x536/0x720 net/ipv6/fib6_rules.c:120
 ip6_route_input_lookup net/ipv6/route.c:2338 [inline]
 ip6_route_input+0x662/0xc70 net/ipv6/route.c:2641
 ip6_rcv_finish_core.constprop.0+0x1a0/0x5d0 net/ipv6/ip6_input.c:66
 ip6_rcv_finish net/ipv6/ip6_input.c:77 [inline]
 NF_HOOK include/linux/netfilter.h:318 [inline]
 NF_HOOK include/linux/netfilter.h:312 [inline]
 ipv6_rcv+0x1e8/0x650 net/ipv6/ip6_input.c:311
 __netif_receive_skb_one_core+0x12d/0x1e0 net/core/dev.c:6079
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:6192
 process_backlog+0x439/0x15e0 net/core/dev.c:6544
 __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:7594
 napi_poll net/core/dev.c:7657 [inline]
 net_rx_action+0x97f/0xef0 net/core/dev.c:7784
 handle_softirqs+0x219/0x8e0 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x109/0x170 kernel/softirq.c:723
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1052 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1052
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:82
Code: 77 6f 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 23 94 2c 00 fb f4 <e9> 3c 0a 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffc90000197de8 EFLAGS: 000002c6
RAX: 0000000000373cb9 RBX: 0000000000000001 RCX: ffffffff8b5d92a9
RDX: 0000000000000000 RSI: ffffffff8da28d25 RDI: ffffffff8bf075c0
RBP: ffffed1003a5bb58 R08: 0000000000000001 R09: ffffed10170a6655
R10: ffff8880b85332ab R11: 0000000000000001 R12: 0000000000000001
R13: ffff88801d2ddac0 R14: ffffffff908248d0 R15: 0000000000000000
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:190 [inline]
 do_idle+0x38d/0x500 kernel/sched/idle.c:330
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:428
 start_secondary+0x21d/0x2b0 arch/x86/kernel/smpboot.c:315
 common_startup_64+0x13e/0x148
 </TASK>