syzbot
INFO: rcu detected stall in dentry_kill
Status:
upstream: reported on 2026/01/20 19:30
Reported-by: syzbot+ecc91afd56cfea8535b2@syzkaller.appspotmail.com
First crash: 209d, last: 8d08h
Sample crash report:
rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2629 jiffies s: 259105 root: 0x1/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 26860 Comm: syz.2.5893 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x4/0x60 kernel/kcov.c:215
Code: 00 00 00 00 00 90 53 48 89 fb e8 17 00 00 00 48 8b 3d 00 df 9e 0c 48 89 de 5b e9 77 62 50 00 00 00 cc cc 00 00 cc 48 8b 04 24 <65> 48 8b 0d 14 41 80 7e 65 8b 15 15 41 80 7e 81 e2 00 01 ff 00 74
RSP: 0018:ffffc90000007938 EFLAGS: 00000806
RAX: ffffffff81aa7c3b RBX: 1ffff92000000f28 RCX: 0000000000000001
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000008
RBP: ffffc900000079e8 R08: ffffffff8e210aef R09: 1ffffffff1c4215d
R10: dffffc0000000000 R11: fffffbfff1c4215e R12: dffffc0000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: ffff888027a35618
FS: 00007f42272eb6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000032b0c000 CR4: 00000000003506f0
DR0: 0000000000000008 DR1: 0000000000000008 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
ct_irq_exit_irqson+0x6b/0x170 kernel/context_tracking.c:418
trace_irq_enable_rcuidle+0xd8/0x140 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x24/0x40 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:728
RIP: 0010:rcu_read_unlock_special+0x7f/0x510 kernel/rcu/tree_plugin.h:685
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 a2 7c 95 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 40 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007ae0 EFLAGS: 00000206
RAX: f218d20fb1351200 RBX: 1ffff92000000f64 RCX: f218d20fb1351200
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: ffffffff8adf5de0
RBP: ffffc90000007bd0 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: 0000000000000246
R13: dffffc0000000000 R14: ffff8880b8e3bb00 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:426
rcu_read_unlock include/linux/rcupdate.h:823 [inline]
ieee80211_iterate_active_interfaces_atomic+0x156/0x170 net/mac80211/util.c:826
mac80211_hwsim_beacon+0xb7/0x1b0 drivers/net/wireless/mac80211_hwsim.c:2147
__run_hrtimer kernel/time/hrtimer.c:1751 [inline]
__hrtimer_run_queues+0x522/0xc90 kernel/time/hrtimer.c:1815
hrtimer_run_softirq+0x173/0x290 kernel/time/hrtimer.c:1832
handle_softirqs+0x291/0x910 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:finish_task_switch+0x267/0x8e0 kernel/sched/core.c:5125
Code: d6 08 85 c0 0f 84 38 01 00 00 48 85 db 0f 85 57 01 00 00 0f 1f 44 00 00 4c 89 e7 e8 93 b1 e0 08 e8 2e 11 2f 00 fb 4c 8b 65 b8 <49> 8d bc 24 f8 15 00 00 48 89 f8 48 c1 e8 03 42 0f b6 04 30 84 c0
RSP: 0018:ffffc90004207820 EFLAGS: 00000282
RAX: f218d20fb1351200 RBX: 0000000000000000 RCX: f218d20fb1351200
RDX: dffffc0000000000 RSI: ffffffff8a8c17a0 RDI: ffffffff8adf5de0
RBP: ffffc90004207870 R08: ffff8880b8e3580b R09: 1ffff110171c6b01
R10: dffffc0000000000 R11: ffffed10171c6b02 R12: ffff888025863c00
R13: 1ffff110171c76fa R14: dffffc0000000000 R15: ffff8880b8e3b7d0
context_switch kernel/sched/core.c:5249 [inline]
__schedule+0x1087/0x4030 kernel/sched/core.c:6563
preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:6732
preempt_schedule+0xbc/0xd0 kernel/sched/core.c:6756
preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:34
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
_raw_spin_unlock_irqrestore+0x10d/0x120 kernel/locking/spinlock.c:194
__debug_check_no_obj_freed lib/debugobjects.c:1054 [inline]
debug_check_no_obj_freed+0x471/0x520 lib/debugobjects.c:1075
slab_free_hook mm/slub.c:1704 [inline]
slab_free_freelist_hook+0x64/0x1b0 mm/slub.c:1742
slab_free mm/slub.c:3687 [inline]
kmem_cache_free+0xf7/0x2a0 mm/slub.c:3709
__dentry_kill+0x4db/0x630 fs/dcache.c:625
dentry_kill+0xb8/0x290 fs/dcache.c:-1
dput+0xfa/0x1d0 fs/dcache.c:918
__fput+0x597/0x8b0 fs/file_table.c:328
task_work_run+0x1d0/0x260 kernel/task_work.c:203
resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:177
exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
__syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f422639e0d9
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:00007f42272eb028 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffef RBX: 00007f4226626090 RCX: 00007f422639e0d9
RDX: 0000000000000050 RSI: 00002000000002c0 RDI: 000000000000001c
RBP: 00007f4226435024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4226626128 R14: 00007f4226626090 R15: 00007ffd244b10c8
</TASK>
* Struck through repros no longer work on HEAD.