syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P16406/1:b..l
rcu: 	(detected by 1, t=10505 jiffies, g=104537, q=631 ncpus=2)
task:syz.3.2788      state:R  running task     stack:25928 pid:16406 tgid:16402 ppid:15544  task_flags:0x400040 flags:0x00080003
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7256
 irqentry_exit+0x6f/0x90 kernel/entry/common.c:211
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:get_current arch/x86/include/asm/current.h:25 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x8/0x70 kernel/kcov.c:216
Code: 8b 3d 24 c2 d2 0b 48 89 de 5b e9 53 86 5a 00 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 8b 04 24 <65> 48 8b 0c 25 08 20 6e 92 65 8b 15 28 1c ae 10 81 e2 00 01 ff 00
RSP: 0018:ffffc90003fdf7c0 EFLAGS: 00000246
RAX: ffffffff8211db2f RBX: 000020000026a000 RCX: ffff88802732bc80
RDX: 0000000000000002 RSI: 0000000000000043 RDI: 0000000000000043
RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff8211d989
R10: dffffc0000000000 R11: fffff520007fbf32 R12: 000000007bfaf067
R13: dffffc0000000000 R14: ffff88806bb11008 R15: 0000000000000043
 pmd_page_vaddr arch/x86/include/asm/pgtable.h:1023 [inline]
 pte_offset_kernel include/linux/pgtable.h:117 [inline]
 __pte_map include/linux/pgtable.h:132 [inline]
 ___pte_offset_map+0x1cf/0x250 mm/pgtable-generic.c:301
 __pte_offset_map include/linux/mm.h:3118 [inline]
 pte_offset_map_rw_nolock+0x3b/0x160 mm/pgtable-generic.c:326
 handle_pte_fault mm/memory.c:6162 [inline]
 __handle_mm_fault+0xb3a/0x5400 mm/memory.c:6318
 handle_mm_fault+0x40a/0x8e0 mm/memory.c:6487
 do_user_addr_fault+0x764/0x1380 arch/x86/mm/fault.c:1387
 handle_page_fault arch/x86/mm/fault.c:1476 [inline]
 exc_page_fault+0x82/0x100 arch/x86/mm/fault.c:1532
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618
RIP: 0010:__clear_user arch/x86/include/asm/uaccess_64.h:188 [inline]
RIP: 0010:clear_user arch/x86/include/asm/uaccess_64.h:205 [inline]
RIP: 0010:read_zero+0x9a/0x1d0 drivers/char/mem.c:486
Code: e8 5b 60 a8 fc 49 39 ef 0f 82 f6 00 00 00 48 c7 c7 5c 2e 73 8d be b5 00 00 00 e8 b1 b4 f5 fc 0f 01 cb 31 c0 4c 89 e9 48 89 ef <f3> aa 0f 1f 00 48 89 cd 0f 01 ca 31 ff 48 89 ce e8 a1 62 a8 fc 48
RSP: 0018:ffffc90003fdfc58 EFLAGS: 00050246
RAX: 0000000000000000 RBX: 0000000000269000 RCX: 0000000000000040
RDX: 0000000000000000 RSI: ffffffff8d8f287e RDI: 000020000026a000
RBP: 0000200000269040 R08: 0000000000000000 R09: ffffffff820d5b70
R10: dffffc0000000000 R11: ffffed1004e65791 R12: dffffc0000000000
R13: 0000000000001000 R14: 000000007fd96000 R15: 00007ffffffff000
 vfs_read+0x200/0xa30 fs/read_write.c:570
 ksys_read+0x145/0x250 fs/read_write.c:715
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ffb4d38efc9
RSP: 002b:00007ffb4e2a3038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007ffb4d5e6180 RCX: 00007ffb4d38efc9
RDX: 00000000ffffff96 RSI: 0000200000000040 RDI: 0000000000000006
RBP: 00007ffb4d411f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffb4d5e6218 R14: 00007ffb4d5e6180 R15: 00007ffd9b57a8c8
 </TASK>
rcu: rcu_preempt kthread starved for 10422 jiffies! g104537 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:26464 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5325 [inline]
 __schedule+0x1798/0x4cc0 kernel/sched/core.c:6929
 __schedule_loop kernel/sched/core.c:7011 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:7026
 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+0x4bc/0x870 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: 8373 Comm: kworker/u8:26 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:csd_lock_wait kernel/smp.c:342 [inline]
RIP: 0010:smp_call_function_many_cond+0xd33/0x12d0 kernel/smp.c:877
Code: 45 8b 2c 24 44 89 ee 83 e6 01 31 ff e8 b6 73 0b 00 41 83 e5 01 49 bd 00 00 00 00 00 fc ff df 75 07 e8 61 6f 0b 00 eb 38 f3 90 <42> 0f b6 04 2b 84 c0 75 11 41 f7 04 24 01 00 00 00 74 1e e8 45 6f
RSP: 0018:ffffc90004aaf640 EFLAGS: 00000293
RAX: ffffffff81b494ab RBX: 1ffff11017108441 RCX: ffff888024425ac0
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90004aaf7c0 R08: ffffffff8f7cd377 R09: 1ffffffff1ef9a6e
R10: dffffc0000000000 R11: fffffbfff1ef9a6f R12: ffff8880b8842208
R13: dffffc0000000000 R14: ffff8880b893b240 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff88812623e000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000000dd38000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3f/0x80 kernel/smp.c:1043
 on_each_cpu include/linux/smp.h:71 [inline]
 smp_text_poke_sync_each_cpu arch/x86/kernel/alternative.c:2713 [inline]
 smp_text_poke_batch_finish+0x5f9/0x1130 arch/x86/kernel/alternative.c:2923
 arch_jump_label_transform_apply+0x1c/0x30 arch/x86/kernel/jump_label.c:146
 static_key_disable_cpuslocked+0xc5/0x1b0 kernel/jump_label.c:240
 static_key_disable+0x1a/0x20 kernel/jump_label.c:248
 toggle_allocation_gate+0x1a1/0x240 mm/kfence/core.c:857
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>