syzbot

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-...!: (1 ticks this GP) idle=fc54/1/0x4000000000000000 softirq=40790/40790 fqs=0
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P9100/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=30125, q=108 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 9105 Comm: syz.1.681 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:enqueue_hrtimer+0xb4/0x380 kernel/time/hrtimer.c:1082
Code: 02 00 00 00 e8 2d 6c 12 00 40 84 ed 74 14 e8 23 52 f8 ff 84 c0 0f 84 1c 01 00 00 e8 16 69 12 00 eb 05 e8 0f 69 12 00 4d 89 f5 <49> c1 ed 03 43 80 7c 25 00 00 74 08 4c 89 f7 e8 b8 ba 78 00 4d 8b
RSP: 0018:ffffc90000007d08 EFLAGS: 00000006
RAX: ffffffff81af47da RBX: ffff888028551300 RCX: ffff88802d159e80
RDX: 0000000000010000 RSI: ffffffff8bc02340 RDI: ffffffff8bc02300
RBP: 0000000000000001 R08: ffffffff8f817677 R09: 1ffffffff1f02ece
R10: dffffc0000000000 R11: fffffbfff1f02ecf R12: dffffc0000000000
R13: ffff8880b8628340 R14: ffff8880b8628340 R15: 0000000000000000
FS:  00007f907f16c6c0(0000) GS:ffff888125e44000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30d05ff8 CR3: 000000007a1ec000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 __run_hrtimer kernel/time/hrtimer.c:1794 [inline]
 __hrtimer_run_queues+0x636/0xc30 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:memset+0xf/0x20 arch/x86/lib/memset_64.S:38
Code: 44 88 1f e9 2e 58 b5 f5 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 49 89 f9 40 88 f0 48 89 d1 <f3> aa 4c 89 c8 e9 02 58 b5 f5 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc9000c287428 EFLAGS: 00000246
RAX: ffff88802b093000 RBX: 0000000000000000 RCX: 000000000000000f
RDX: 0000000000000200 RSI: 0000000000000000 RDI: ffffc9000c287621
RBP: ffffc9000c287658 R08: ffffffff817612e8 R09: ffffc9000c287430
R10: dffffc0000000000 R11: fffffbfff1f02ecf R12: dffffc0000000000
R13: 1ffff92001850ee0 R14: 0000000000000000 R15: ffffc9000c287430
 kasan_save_stack+0x2f/0x60 mm/kasan/common.c:53
 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556
 __call_rcu_common kernel/rcu/tree.c:3119 [inline]
 call_rcu+0x157/0x9c0 kernel/rcu/tree.c:3239
 slab_free_hook mm/slub.c:2504 [inline]
 slab_free mm/slub.c:6663 [inline]
 kmem_cache_free+0x488/0x620 mm/slub.c:6774
 __fput_deferred+0x227/0x390 fs/file_table.c:523
 fput_close+0x113/0x220 fs/file_table.c:585
 path_openat+0x367c/0x3dd0 fs/namei.c:4796
 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: 0033:0x7f907e38f749
Code: 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 01 48
RSP: 002b:00007f907f16c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f907e5e5fa0 RCX: 00007f907e38f749
RDX: 0000000000000002 RSI: 0000200000000000 RDI: ffffffffffffff9c
RBP: 00007f907e413f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f907e5e6038 R14: 00007f907e5e5fa0 R15: 00007ffe11a3a808
 </TASK>
task:syz.7.680       state:R  running task     stack:25336 pid:9100  tgid:9099  ppid:8047   task_flags:0x400140 flags:0x00080000
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_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:rcu_read_lock include/linux/rcupdate.h:868 [inline]
RIP: 0010:class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
RIP: 0010:unwind_next_frame+0xc6/0x2390 arch/x86/kernel/unwind_orc.c:479
Code: 34 00 4c 8d 3d 00 00 00 00 48 c7 c7 e0 19 f4 8d 31 f6 31 d2 b9 02 00 00 00 45 31 c0 45 31 c9 41 57 e8 1e 35 2a 00 48 83 c4 08 <e8> 55 88 e6 09 85 c0 74 3a e8 3c 5a 33 00 84 c0 75 31 e8 43 88 e6
RSP: 0018:ffffc9000bfdef38 EFLAGS: 00000282
RAX: cd6132acbc1d0800 RBX: ffffffff82659d69 RCX: cd6132acbc1d0800
RDX: 0000000083038513 RSI: ffffffff8d96d334 RDI: ffffffff8bc02360
RBP: dffffc0000000000 R08: ffffffff81743f85 R09: ffffffff8df419e0
R10: dffffc0000000000 R11: ffffffff81ad9fb0 R12: 1ffff920017fbe01
R13: ffffc9000bfdf040 R14: ffffc9000bfdf008 R15: ffffffff81743f85
 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
 unpoison_slab_object mm/kasan/common.c:339 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:365
 kasan_slab_alloc include/linux/kasan.h:252 [inline]
 slab_post_alloc_hook mm/slub.c:4948 [inline]
 slab_alloc_node mm/slub.c:5258 [inline]
 kmem_cache_alloc_noprof+0x37d/0x710 mm/slub.c:5265
 __kernfs_new_node+0xdc/0x880 fs/kernfs/dir.c:637
 kernfs_new_node+0x102/0x210 fs/kernfs/dir.c:716
 __kernfs_create_file+0x4b/0x2e0 fs/kernfs/file.c:1057
 sysfs_add_file_mode_ns+0x238/0x300 fs/sysfs/file.c:313
 create_files fs/sysfs/group.c:82 [inline]
 internal_create_group+0x667/0x1170 fs/sysfs/group.c:189
 internal_create_groups fs/sysfs/group.c:229 [inline]
 sysfs_create_groups+0x59/0x120 fs/sysfs/group.c:255
 create_dir lib/kobject.c:78 [inline]
 kobject_add_internal+0x6e9/0xcc0 lib/kobject.c:240
 kobject_add_varg lib/kobject.c:374 [inline]
 kobject_init_and_add+0x125/0x190 lib/kobject.c:457
 ext4_register_sysfs+0xae/0x2a0 fs/ext4/sysfs.c:577
 __ext4_fill_super fs/ext4/super.c:5692 [inline]
 ext4_fill_super+0x5bed/0x6160 fs/ext4/super.c:5777
 get_tree_bdev_flags+0x40e/0x4d0 fs/super.c:1691
 vfs_get_tree+0x92/0x2a0 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount+0x302/0xa10 fs/namespace.c:3712
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x313/0x410 fs/namespace.c:4201
 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: 0033:0x7fcf69190eea
RSP: 002b:00007fcf6a014e68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fcf6a014ef0 RCX: 00007fcf69190eea
RDX: 0000200000000180 RSI: 00002000000001c0 RDI: 00007fcf6a014eb0
RBP: 0000200000000180 R08: 00007fcf6a014ef0 R09: 0000000000000800
R10: 0000000000000800 R11: 0000000000000246 R12: 00002000000001c0
R13: 00007fcf6a014eb0 R14: 00000000000004a1 R15: 0000200000000700
 </TASK>
rcu: rcu_preempt kthread starved for 10502 jiffies! g30125 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:26856 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:
CPU: 1 UID: 0 PID: 0 Comm: swapper/1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:pv_native_safe_halt+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: be 83 b5 f5 cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d f3 90 0d 00 f3 0f 1e fa fb f4 <e9> 93 83 b5 f5 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc90000197de0 EFLAGS: 000002c6
RAX: e9cbeec4f6fcc400 RBX: ffffffff81978eba RCX: e9cbeec4f6fcc400
RDX: 0000000000000001 RSI: ffffffff8d786800 RDI: ffffffff8bc02360
RBP: ffffc90000197f10 R08: ffff8880b87336db R09: 1ffff110170e66db
R10: dffffc0000000000 R11: ffffed10170e66dc R12: ffffffff8f817670
R13: 1ffff110038dab70 R14: 0000000000000001 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888125f44000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30d09ff8 CR3: 000000007a1ec000 CR4: 0000000000350ef0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x73/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x1ea/0x520 kernel/sched/idle.c:332
 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:430
 start_secondary+0x101/0x110 arch/x86/kernel/smpboot.c:312
 common_startup_64+0x13e/0x147
 </TASK>