syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4174/2:b..l
	(detected by 0, t=10502 jiffies, g=41105, q=69)
task:udevd           state:R  running task     stack:23216 pid: 4174 ppid:  3560 flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 preempt_schedule_irq+0xbb/0x160 kernel/sched/core.c:6799
 irqentry_exit+0x63/0x70 kernel/entry/common.c:432
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:lock_acquire+0x208/0x400 kernel/locking/lockdep.c:5627
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3d 04 f8 0f 85 f1 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 43 c7 44 3d 08 00 00 00 00 65 48 8b 04
RSP: 0018:ffffc90002e6f6c0 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: ec060365ca4ba600
RDX: 0000000000000000 RSI: ffffffff8a2b3a20 RDI: ffffffff8a79f780
RBP: ffffc90002e6f7d0 R08: dffffc0000000000 R09: 1ffffffff203a218
R10: dffffc0000000000 R11: fffffbfff203a219 R12: ffffffff8c31eaa0
R13: 1ffff920005cdee4 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 prepend_path+0x1d5/0xbb0 fs/d_path.c:169
 d_absolute_path+0x9e/0x140 fs/d_path.c:235
 tomoyo_get_absolute_path security/tomoyo/realpath.c:101 [inline]
 tomoyo_realpath_from_path+0x331/0x610 security/tomoyo/realpath.c:276
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path2_perm+0x27e/0x840 security/tomoyo/file.c:922
 tomoyo_path_rename+0xfd/0x150 security/tomoyo/tomoyo.c:278
 security_path_rename+0x1dc/0x280 security/security.c:1205
 do_renameat2+0x69b/0xf60 fs/namei.c:4980
 __do_sys_rename fs/namei.c:5039 [inline]
 __se_sys_rename fs/namei.c:5037 [inline]
 __x64_sys_rename+0x82/0x90 fs/namei.c:5037
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f8343ef5cc7
RSP: 002b:00007fff15114198 EFLAGS: 00000206 ORIG_RAX: 0000000000000052
RAX: ffffffffffffffda RBX: 000055ec256f3990 RCX: 00007f8343ef5cc7
RDX: 000055ec256cf010 RSI: 00007fff151141b0 RDI: 00007fff151145b0
RBP: 000055ec256e2e20 R08: 00000000000001e0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007fff151141b0
R13: 00007fff151145b0 R14: 0000000000000000 R15: 000055ec06e859dd
 </TASK>
rcu: rcu_preempt kthread starved for 10524 jiffies! g41105 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:I stack:27760 pid:   15 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11ef/0x43c0 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 schedule_timeout+0x184/0x2d0 kernel/time/timer.c:1914
 rcu_gp_fqs_loop+0x2be/0x11d0 kernel/rcu/tree.c:1972
 rcu_gp_kthread+0x9b/0x370 kernel/rcu/tree.c:2145
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </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 PID: 4677 Comm: kworker/u4:12 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Workqueue: writeback wb_workfn (flush-8:0)
RIP: 0010:csd_lock_wait kernel/smp.c:440 [inline]
RIP: 0010:smp_call_function_many_cond+0xbb5/0xd90 kernel/smp.c:969
Code: b6 44 05 00 84 c0 0f 85 9d 00 00 00 41 8b 1c 24 89 de 83 e6 01 31 ff e8 29 60 0b 00 83 e3 01 75 07 e8 bf 5c 0b 00 eb 43 f3 90 <48> b8 00 00 00 00 00 fc ff df 41 0f b6 44 05 00 84 c0 75 11 41 f7
RSP: 0018:ffffc90004a56680 EFLAGS: 00000293
RAX: ffffffff816dc308 RBX: 0000000000000001 RCX: ffff88807adb0000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: ffffc90004a567c0 R08: ffff8880b913b3d7 R09: 1ffff1101722767a
R10: dffffc0000000000 R11: ffffed101722767b R12: ffff8880b9042848
R13: 1ffff11017208509 R14: ffff8880b913b3c0 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f7fe09725d8 CR3: 0000000062c09000 CR4: 00000000003526e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 on_each_cpu_cond_mask+0x3b/0x80 kernel/smp.c:1134
 __flush_tlb_multi arch/x86/include/asm/paravirt.h:87 [inline]
 flush_tlb_multi arch/x86/mm/tlb.c:946 [inline]
 flush_tlb_mm_range+0x365/0x580 arch/x86/mm/tlb.c:1034
 flush_tlb_page arch/x86/include/asm/tlbflush.h:240 [inline]
 ptep_clear_flush+0x112/0x140 mm/pgtable-generic.c:97
 page_mkclean_one+0x1eb/0x3e0 mm/rmap.c:938
 rmap_walk_file+0x408/0x610 mm/rmap.c:2378
 rmap_walk mm/rmap.c:2396 [inline]
 page_mkclean+0x2f4/0x400 mm/rmap.c:1006
 clear_page_dirty_for_io+0x3f8/0x9f0 mm/page-writeback.c:2749
 mpage_submit_page+0x8a/0x210 fs/ext4/inode.c:2093
 mpage_process_page_bufs+0x6d8/0x8b0 fs/ext4/inode.c:2227
 mpage_prepare_extent_to_map+0xbc2/0xfe0 fs/ext4/inode.c:2655
 ext4_writepages+0xa9a/0x2df0 fs/ext4/inode.c:2783
 do_writepages+0x476/0x6e0 mm/page-writeback.c:2386
 __writeback_single_inode+0x153/0xda0 fs/fs-writeback.c:1657
 writeback_sb_inodes+0xa4e/0x1680 fs/fs-writeback.c:1940
 __writeback_inodes_wb+0x12a/0x3f0 fs/fs-writeback.c:2011
 wb_writeback+0x46f/0xbe0 fs/fs-writeback.c:2116
 wb_check_old_data_flush fs/fs-writeback.c:2216 [inline]
 wb_do_writeback fs/fs-writeback.c:2269 [inline]
 wb_workfn+0xb15/0xf20 fs/fs-writeback.c:2298
 process_one_work+0x85f/0x1010 kernel/workqueue.c:2310
 worker_thread+0xaa6/0x1290 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>