syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5195/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=15513, q=269 ncpus=2)
task:udevd           state:R  running task     stack:25440 pid:5195  tgid:5195  ppid:1      task_flags:0x400140 flags:0x00080800
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x14bc/0x5000 kernel/sched/core.c:6863
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7190
 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:orc_ip arch/x86/kernel/unwind_orc.c:80 [inline]
RIP: 0010:__orc_find arch/x86/kernel/unwind_orc.c:102 [inline]
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:227 [inline]
RIP: 0010:unwind_next_frame+0x12f9/0x2390 arch/x86/kernel/unwind_orc.c:494
Code: 00 49 89 d5 48 89 d5 48 89 d8 48 29 e8 48 89 c1 48 c1 f9 02 48 c1 e8 3f 48 01 c8 48 83 e0 fe 4c 8d 3c 45 00 00 00 00 49 01 ef <4c> 89 f8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84
RSP: 0018:ffffc90003a97178 EFLAGS: 00000286
RAX: 0000000000000000 RBX: ffffffff8fba3784 RCX: 0000000000000000
RDX: ffffffff8fba3780 RSI: ffffffff9045c17e RDI: ffffffff8bc08300
RBP: ffffffff8fba3784 R08: 0000000000000002 R09: ffffffff8df419e0
R10: dffffc0000000000 R11: ffffffff81ada000 R12: ffffffff84448241
R13: ffffffff8fba3780 R14: ffffc90003a97248 R15: ffffffff8fba3784
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:252 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:284
 kasan_slab_free include/linux/kasan.h:234 [inline]
 slab_free_hook mm/slub.c:2540 [inline]
 slab_free mm/slub.c:6668 [inline]
 kfree+0x1c0/0x660 mm/slub.c:6876
 tomoyo_check_open_permission+0x2c2/0x3b0 security/tomoyo/file.c:786
 security_file_open+0xb1/0x270 security/security.c:2636
 do_dentry_open+0x34e/0x1420 fs/open.c:939
 vfs_open+0x3b/0x340 fs/open.c:1094
 do_open fs/namei.c:4628 [inline]
 path_openat+0x340e/0x3dd0 fs/namei.c:4787
 do_filp_open+0x1fa/0x410 fs/namei.c:4814
 do_sys_openat2+0x121/0x200 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x138/0x170 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f15538a7407
RSP: 002b:00007fff0e257350 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f1553f5e880 RCX: 00007f15538a7407
RDX: 0000000000080000 RSI: 00007fff0e2574d0 RDI: ffffffffffffff9c
RBP: 0000000000000008 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000557f01b5a7f5
R13: 0000557f01b5a7f5 R14: 0000000000000001 R15: 00007fff0e25bb20
 </TASK>
rcu: rcu_preempt kthread starved for 10553 jiffies! g15513 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:27736 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x14bc/0x5000 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6960
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </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 UID: 0 PID: 6144 Comm: syz.1.18 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:task_tgid_nr include/linux/pid.h:252 [inline]
RIP: 0010:is_global_init include/linux/pid.h:335 [inline]
RIP: 0010:sig_task_ignored kernel/signal.c:91 [inline]
RIP: 0010:sig_ignored kernel/signal.c:124 [inline]
RIP: 0010:prepare_signal+0x79a/0xc00 kernel/signal.c:935
Code: f3 48 81 c3 98 00 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 48 89 df e8 a9 35 a0 00 48 8b 1b <4d> 8d b4 24 1c 06 00 00 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00
RSP: 0018:ffffc90000a08bf8 EFLAGS: 00000046
RAX: 1ffff1100fddce73 RBX: 00007f855e1b7e80 RCX: dffffc0000000000
RDX: ffff888025350000 RSI: 0000000000000021 RDI: 0000000000000009
RBP: 0000000000000001 R08: ffffffff8187853a R09: ffff88807eee6f18
R10: 0000000000000000 R11: fffff52000141164 R12: ffff888025350000
R13: 0000000000000020 R14: ffff88807eee6f00 R15: ffff888025350960
FS:  00007f855f0086c0(0000) GS:ffff888125f35000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000021365000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 posixtimer_send_sigqueue+0x33c/0xa70 kernel/signal.c:2006
 posix_timer_queue_signal kernel/time/posix-timers.c:364 [inline]
 posix_timer_fn+0x121/0x1c0 kernel/time/posix-timers.c:379
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x51c/0xc30 kernel/time/hrtimer.c:1841
 hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1903
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
 __sysvec_apic_timer_interrupt+0x102/0x3e0 arch/x86/kernel/apic/apic.c:1062
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0xa1/0xc0 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:srso_alias_safe_ret+0x5/0x7 arch/x86/lib/retpoline.S:213
Code: cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc cc 48 8d 64 24 08 <c3> cc e8 f4 ff ff ff 0f 0b cc cc cc cc cc cc cc cc cc cc cc cc cc
RSP: 0018:ffffc90003307a80 EFLAGS: 00000293
RAX: ffffffff81697700 RBX: ffff888025350000 RCX: ffff888025350000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff888025350000
RBP: 0000000000000000 R08: ffff888025350007 R09: 1ffff11004a6a000
R10: dffffc0000000000 R11: ffffed1004a6a001 R12: 0000000000000000
R13: dffffc0000000000 R14: 00007f855f008068 R15: ffffc90003307b60
 x86_task_fpu+0x10/0x90 arch/x86/kernel/fpu/core.c:62
 fpu__alloc_mathframe+0x36/0x130 arch/x86/kernel/fpu/signal.c:493
 get_sigframe+0x41a/0x7d0 arch/x86/kernel/signal.c:132
 x64_setup_rt_frame+0x15b/0xd40 arch/x86/kernel/signal_64.c:175
 setup_rt_frame arch/x86/kernel/signal.c:250 [inline]
 handle_signal arch/x86/kernel/signal.c:294 [inline]
 arch_do_signal_or_restart+0x3d1/0x7a0 arch/x86/kernel/signal.c:339
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop+0x87/0x4f0 kernel/entry/common.c:75
 __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_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x2d0/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f855e18f747
Code: ff ff 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
RSP: 002b:00007f855f0080e8 EFLAGS: 00000246
RAX: 00000000000000ca RBX: 00007f855e3e5fa8 RCX: 00007f855e18f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f855e3e5fa8
RBP: 00007f855e3e5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f855e3e6038 R14: 00007ffd7f010320 R15: 00007ffd7f010408
 </TASK>