syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P76/1:b..l P5483/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=9353, q=473 ncpus=2)
task:dhcpcd          state:R  running task     stack:21256 pid:5483  tgid:5483  ppid:5482   task_flags:0x400140 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1139/0x6150 kernel/sched/core.c:6863
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7190
 irqentry_exit+0x1d8/0x8c0 kernel/entry/common.c:216
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:on_stack arch/x86/include/asm/stacktrace.h:55 [inline]
RIP: 0010:stack_access_ok+0x0/0x200 arch/x86/kernel/unwind_orc.c:409
Code: 20 ff ff ff 44 8b 85 30 ff ff ff e9 ba fe ff ff 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <48> b8 00 00 00 00 00 fc ff df 41 57 41 56 4c 8d 77 08 41 55 41 54
RSP: 0018:ffffc90002f574e0 EFLAGS: 00000287
RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffffffff912fc08c
RDX: 0000000000000008 RSI: ffffc90002f578c0 RDI: ffffc90002f57558
RBP: ffffc90002f578c0 R08: 0000000000000001 R09: 00000000d50c1a4a
R10: 0000000000000002 R11: 000000000001288c R12: ffffc90002f575a8
R13: ffffc90002f57558 R14: ffffc90002f578e0 R15: ffffc90002f5758c
 deref_stack_reg arch/x86/kernel/unwind_orc.c:419 [inline]
 unwind_next_frame+0x1509/0x20b0 arch/x86/kernel/unwind_orc.c:663
 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:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x89/0x90 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5263 [inline]
 kmem_cache_alloc_noprof+0x25e/0x770 mm/slub.c:5270
 vm_area_dup+0x27/0x8d0 mm/vma_init.c:123
 dup_mmap+0x6a4/0x20e0 mm/mmap.c:1773
 dup_mm kernel/fork.c:1529 [inline]
 copy_mm kernel/fork.c:1581 [inline]
 copy_process+0x3b9f/0x7430 kernel/fork.c:2221
 kernel_clone+0xfc/0x910 kernel/fork.c:2651
 __do_sys_clone+0xce/0x120 kernel/fork.c:2792
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff4c1b6a636
RSP: 002b:00007ffc938c8640 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffc938c8648 RCX: 00007ff4c1b6a636
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffc938e8b90 R08: 0000000000000000 R09: 0000000000000001
R10: 00007ff4c1a96a10 R11: 0000000000000246 R12: 00007ffc938c8780
R13: 0000000000000000 R14: 0000000000000000 R15: 000055651dd35ac0
 </TASK>
task:kworker/u8:5    state:R  running task     stack:25480 pid:76    tgid:76    ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1139/0x6150 kernel/sched/core.c:6863
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7190
 irqentry_exit+0x1d8/0x8c0 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x62/0x330 kernel/locking/lockdep.c:5872
Code: b4 18 12 83 f8 07 0f 87 a2 02 00 00 89 c0 48 0f a3 05 22 bb ee 0e 0f 82 74 02 00 00 8b 35 ba eb ee 0e 85 f6 0f 85 8d 00 00 00 <48> 8b 44 24 30 65 48 2b 05 39 b4 18 12 0f 85 ad 02 00 00 48 83 c4
RSP: 0018:ffffc9000216f9c8 EFLAGS: 00000206
RAX: 0000000000000046 RBX: ffffffff8e3c96a0 RCX: 000000006fe00776
RDX: 0000000000000000 RSI: ffffffff8daa7ee5 RDI: ffffffff8bf2b400
RBP: 0000000000000002 R08: 00000000e7bdffda R09: 00000000ae7bdffd
R10: 0000000000000002 R11: ffff88801cf32ff0 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]
 batadv_iv_ogm_slide_own_bcast_window net/batman-adv/bat_iv_ogm.c:761 [inline]
 batadv_iv_ogm_schedule_buff+0x5d0/0x14c0 net/batman-adv/bat_iv_ogm.c:833
 batadv_iv_ogm_schedule net/batman-adv/bat_iv_ogm.c:873 [inline]
 batadv_iv_ogm_schedule net/batman-adv/bat_iv_ogm.c:866 [inline]
 batadv_iv_send_outstanding_bat_ogm_packet+0x329/0x920 net/batman-adv/bat_iv_ogm.c:1709
 process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
rcu: rcu_preempt kthread starved for 10562 jiffies! g9353 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:28440 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1139/0x6150 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6960
 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+0x983/0xb10 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 6137 Comm: vhost-6136 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x70 kernel/kcov.c:210
Code: f6 63 58 00 48 89 df 5b e9 3d 16 5e 00 be 03 00 00 00 5b e9 f2 d5 ed 02 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 48 8b 34 24 65 48 8b 15 48 c7 f3 11 65 8b 05 59 c7 f3
RSP: 0018:ffffc9000433fb50 EFLAGS: 00000246
RAX: 0000000000000000 RBX: ffff888074f84300 RCX: 1ffff92000867f58
RDX: ffff888030c48000 RSI: 0000000000000000 RDI: ffff888074f84300
RBP: ffff888030c48000 R08: 0000000000000005 R09: 0000000000000000
R10: 00000000fffffff2 R11: ffff888030c48b30 R12: 0000000000000000
R13: 00000000ffffffff R14: ffff88805ee54cb8 R15: 0000200000000900
FS:  00007f7bb95f66c0(0000) GS:ffff8881248f5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00002000000015c0 CR3: 000000007d8c8000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 get_current arch/x86/include/asm/current.h:25 [inline]
 eventfd_signal_mask+0x1f/0x1e0 fs/eventfd.c:68
 eventfd_signal include/linux/eventfd.h:89 [inline]
 vhost_update_used_flags+0x340/0x3d0 drivers/vhost/vhost.c:2585
 vhost_enable_notify+0x338/0x6e0 drivers/vhost/vhost.c:3227
 vhost_vsock_handle_tx_kick+0x900/0xdb0 drivers/vhost/vsock.c:519
 vhost_run_work_list+0x18b/0x230 drivers/vhost/vhost.c:454
 vhost_task_fn+0x165/0x460 kernel/vhost_task.c:49
 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>