syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 GPs behind) idle=1e64/1/0x4000000000000000 softirq=45773/45774 fqs=0
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P12268/1:b..l
rcu: 	(detected by 1, t=10505 jiffies, g=53969, q=441 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 12265 Comm: syz.3.2262 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
RIP: 0010:debug_objects_fill_pool+0x45/0x5a0 lib/debugobjects.c:715
Code: 24 10 b3 8a b5 41 48 8d 5c 24 10 48 c7 44 24 18 6c 0c f8 8d 48 c1 eb 03 48 c7 44 24 20 70 53 ff 84 48 01 d8 c7 00 f1 f1 f1 f1 <c7> 40 04 00 f3 f3 f3 65 48 8b 05 44 2c 13 0f 48 89 44 24 68 31 c0
RSP: 0018:ffffc90000007cb8 EFLAGS: 00000086
RAX: fffff52000000f99 RBX: 1ffff92000000f99 RCX: ffffffff81f4953b
RDX: ffff888059e00000 RSI: ffffffff8bb2c7c0 RDI: ffff88807d90a300
RBP: ffffc90000007e48 R08: 0000000000000005 R09: ffffc90000007d80
R10: 0000000000000001 R11: 0000000000000001 R12: dffffc0000000000
R13: ffff88807d90a300 R14: 0000000000000001 R15: 1ffff92000000fb0
FS:  00007f9c199d56c0(0000) GS:ffff8881242f8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f8f4548aff8 CR3: 000000003a9ea000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 debug_object_activate+0x103/0x490 lib/debugobjects.c:831
 debug_hrtimer_activate kernel/time/hrtimer.c:485 [inline]
 debug_activate kernel/time/hrtimer.c:528 [inline]
 enqueue_hrtimer+0x75/0x2f0 kernel/time/hrtimer.c:1109
 __run_hrtimer kernel/time/hrtimer.c:1946 [inline]
 __hrtimer_run_queues+0x73d/0xa00 kernel/time/hrtimer.c:1994
 hrtimer_interrupt+0x3e5/0x940 kernel/time/hrtimer.c:2113
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 __sysvec_apic_timer_interrupt+0x10b/0x460 arch/x86/kernel/apic/apic.c:1067
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
 sysvec_apic_timer_interrupt+0x9e/0xc0 arch/x86/kernel/apic/apic.c:1061
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x70 kernel/kcov.c:210
Code: 56 6e 5b 00 48 89 df 5b e9 9d ee 60 00 be 03 00 00 00 5b e9 82 64 ee 02 66 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 65 8b 05 25 ab 09 12 48 8b 34 24 65 48 8b 15 01 ab 09
RSP: 0018:ffffc9000535f848 EFLAGS: 00000286
RAX: 0000000000000000 RBX: ffff88803a574c80 RCX: ffffffff8b9712cd
RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffffc9000535f798
RBP: 0000000000000000 R08: 0000000000000001 R09: fffff52000a6bef3
R10: ffffc9000535f79f R11: 0000000000000000 R12: ffff88803a575210
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 __unix_dgram_recvmsg+0x766/0xc30 net/unix/af_unix.c:2662
 unix_dgram_recvmsg+0xcd/0x100 net/unix/af_unix.c:2676
 sock_recvmsg_nosec net/socket.c:1137 [inline]
 ____sys_recvmsg+0x5b3/0x640 net/socket.c:2916
 ___sys_recvmsg+0x16a/0x1a0 net/socket.c:2960
 do_recvmmsg+0x301/0x760 net/socket.c:3055
 __sys_recvmmsg net/socket.c:3129 [inline]
 __do_sys_recvmmsg net/socket.c:3152 [inline]
 __se_sys_recvmmsg net/socket.c:3145 [inline]
 __x64_sys_recvmmsg+0x22a/0x280 net/socket.c:3145
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9c1b79c819
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:00007f9c199d5028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00007f9c1ba16090 RCX: 00007f9c1b79c819
RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000006
RBP: 00007f9c1b832c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9c1ba16128 R14: 00007f9c1ba16090 R15: 00007ffd45861378
 </TASK>
task:modprobe        state:R  running task     stack:25896 pid:12268 tgid:12268 ppid:12210  task_flags:0x400000 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5387 [inline]
 __schedule+0x10e9/0x6820 kernel/sched/core.c:7188
 preempt_schedule_common+0x42/0xc0 kernel/sched/core.c:7369
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:169 [inline]
 _raw_spin_unlock+0x3e/0x50 kernel/locking/spinlock.c:190
 spin_unlock include/linux/spinlock.h:390 [inline]
 finish_fault+0x8e8/0x1400 mm/memory.c:5763
 do_cow_fault mm/memory.c:5935 [inline]
 do_fault+0xff2/0x1750 mm/memory.c:6029
 do_pte_missing mm/memory.c:4550 [inline]
 handle_pte_fault mm/memory.c:6411 [inline]
 __handle_mm_fault+0x187d/0x2a00 mm/memory.c:6549
 handle_mm_fault+0x36d/0xa20 mm/memory.c:6718
 do_user_addr_fault+0x5a3/0x12f0 arch/x86/mm/fault.c:1334
 handle_page_fault arch/x86/mm/fault.c:1474 [inline]
 exc_page_fault+0x6f/0xd0 arch/x86/mm/fault.c:1527
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0033:0x7f246c26940c
RSP: 002b:00007fffbcc17f50 EFLAGS: 00010202
RAX: 000000b3acfe664f RBX: 0000000000000000 RCX: 00007f246c282de0
RDX: 00007f246c281e80 RSI: 00007f246c24d000 RDI: 00007fffbcc18010
RBP: 00007fffbcc18000 R08: 000000006fffffff R09: 0000000070000029
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10505 jiffies! g53969 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:27992 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5387 [inline]
 __schedule+0x10e9/0x6820 kernel/sched/core.c:7188
 __schedule_loop kernel/sched/core.c:7267 [inline]
 schedule+0xdd/0x390 kernel/sched/core.c:7282
 schedule_timeout+0x127/0x280 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1a9/0x900 kernel/rcu/tree.c:2095
 rcu_gp_kthread+0x179/0x230 kernel/rcu/tree.c:2297
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 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: 12 Comm: kworker/u8:0 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:check_kcov_mode kernel/kcov.c:185 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x39/0x70 kernel/kcov.c:217
Code: 65 48 8b 15 01 ab 09 12 a9 00 01 ff 00 74 1b f6 c4 01 74 07 a9 00 00 ff 00 74 05 c3 cc cc cc cc 8b 82 cc 16 00 00 85 c0 74 f1 <8b> 82 a8 16 00 00 83 f8 02 75 e6 48 8b 8a b0 16 00 00 8b 92 ac 16
RSP: 0018:ffffc90000117868 EFLAGS: 00000246
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ffffffff81fc587d
RDX: ffff88801e6a4a00 RSI: ffffffff81fc5857 RDI: ffff88801e6a4a00
RBP: ffff8880b84432c0 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000003
R13: ffffed1017088659 R14: 0000000000000001 R15: ffff8880b853c580
FS:  0000000000000000(0000) GS:ffff8881243f8000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc15fce5a7f CR3: 000000000e598000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 native_pause arch/x86/include/asm/vdso/processor.h:13 [inline]
 cpu_relax arch/x86/include/asm/vdso/processor.h:18 [inline]
 csd_lock_wait kernel/smp.c:342 [inline]
 smp_call_function_many_cond+0x587/0x1500 kernel/smp.c:892
 on_each_cpu_cond_mask+0x40/0x90 kernel/smp.c:1057
 on_each_cpu include/linux/smp.h:72 [inline]
 smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2761 [inline]
 smp_text_poke_batch_finish+0x337/0xc60 arch/x86/kernel/alternative.c:2971
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 jump_label_update+0x37a/0x550 kernel/jump_label.c:910
 static_key_disable_cpuslocked+0x162/0x1c0 kernel/jump_label.c:240
 static_key_disable+0x1a/0x20 kernel/jump_label.c:248
 toggle_allocation_gate mm/kfence/core.c:913 [inline]
 toggle_allocation_gate+0x149/0x2d0 mm/kfence/core.c:898
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302
 process_scheduled_works kernel/workqueue.c:3385 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466
 kthread+0x370/0x450 kernel/kthread.c:436
 ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>