syzbot


INFO: rcu detected stall in dentry_kill

Status: upstream: reported on 2026/05/06 04:01
Reported-by: syzbot+e788d199648e5ddfa0a8@syzkaller.appspotmail.com
First crash: 31d, last: 1d06h
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in dentry_kill 1 10 1d06h 125d 0/2 upstream: reported on 2026/02/01 10:07
linux-6.1 INFO: rcu detected stall in dentry_kill 1 10 8d09h 136d 0/3 upstream: reported on 2026/01/20 19:30

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (1 ticks this GP) idle=e3f/1/0x4000000000000002 softirq=34722/34722 fqs=2100 
	(detected by 1, t=10503 jiffies, g=49717, q=1231)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 12116 Comm: syz.8.1825 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:perf_tp_event_match kernel/events/core.c:9995 [inline]
RIP: 0010:perf_tp_event+0x278/0xbf0 kernel/events/core.c:10046
Code: 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 0f 85 d2 01 00 00 45 8b 3f 44 89 fe 83 e6 01 31 ff e8 b8 9c e0 ff <41> 83 e7 01 75 44 4d 8d bd 00 01 00 00 4c 89 f8 48 c1 e8 03 48 b9
RSP: 0018:ffffc900000077c0 EFLAGS: 00000046
RAX: ffffffff8198af98 RBX: 1ffff11017206a4a RCX: ffff88805eaf1dc0
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000007a28 R08: ffffffff8d8a06ef R09: 1ffffffff1b140dd
R10: dffffc0000000000 R11: fffffbfff1b140de R12: ffff8880b9035250
R13: ffff88807d9735b8 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f733d479d58 CR3: 000000002f792000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000200000000300 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10021
 perf_trace_preemptirq_template+0x2aa/0x360 include/trace/events/preemptirq.h:14
 trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
 trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
 asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
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 f2 cc 9c 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0018:ffffc90000007c60 EFLAGS: 00000206
RAX: 5b1c84b9d09f3300 RBX: 1ffff92000000f90 RCX: 5b1c84b9d09f3300
RDX: dffffc0000000000 RSI: ffffffff8a2b3180 RDI: ffffffff8a7a09c0
RBP: ffffc90000007d28 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: ffffffff8c323800
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
 __rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 rebalance_domains+0xa0a/0xb30 kernel/sched/fair.c:10660
 handle_softirqs+0x339/0x830 kernel/softirq.c:576
 __do_softirq kernel/softirq.c:610 [inline]
 invoke_softirq kernel/softirq.c:450 [inline]
 __irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
 irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
 sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xbc/0x120 kernel/locking/spinlock.c:194
Code: c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f7 44 24 20 00 02 00 00 41 c6 04 07 f8 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 4f 9d 8b f7 65 8b 05 70 86 3b 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000310efa0 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: 5b1c84b9d09f3300
RDX: dffffc0000000000 RSI: ffffffff8a2b3180 RDI: 0000000000000001
RBP: ffffc9000310f038 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: dffffc0000000000
R13: ffff888059c57000 R14: ffffffff96559680 R15: 1ffff92000621df4
 __debug_check_no_obj_freed lib/debugobjects.c:982 [inline]
 debug_check_no_obj_freed+0x515/0x530 lib/debugobjects.c:1003
 free_pages_prepare mm/page_alloc.c:1345 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0x237/0x6c0 mm/page_alloc.c:3317
 free_unref_page_list+0x119/0x820 mm/page_alloc.c:3433
 release_pages+0x186c/0x1be0 mm/swap.c:963
 __pagevec_release+0x6d/0xe0 mm/swap.c:983
 pagevec_release include/linux/pagevec.h:81 [inline]
 shmem_undo_range+0x62b/0x1930 mm/shmem.c:964
 shmem_truncate_range mm/shmem.c:1063 [inline]
 shmem_evict_inode+0x220/0xa40 mm/shmem.c:1145
 evict+0x4c9/0x8d0 fs/inode.c:647
 __dentry_kill+0x431/0x650 fs/dcache.c:586
 dentry_kill+0xb8/0x290 fs/dcache.c:-1
 dput+0xd8/0x1a0 fs/dcache.c:893
 __fput+0x5ee/0x930 fs/file_table.c:319
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 exit_task_work include/linux/task_work.h:33 [inline]
 do_exit+0x626/0x20c0 kernel/exit.c:884
 do_group_exit+0x12e/0x300 kernel/exit.c:998
 get_signal+0x6d6/0x12d0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xe7/0x12c0 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 irqentry_exit_to_user_mode+0x5/0x30 kernel/entry/common.c:320
 exc_general_protection+0x1e4/0x270 arch/x86/kernel/traps.c:562
 asm_exc_general_protection+0x22/0x30 arch/x86/include/asm/idtentry.h:600
RIP: 0033:0x7f59081a5e61
Code: Unable to access opcode bytes at RIP 0x7f59081a5e37.
RSP: 002b:0000200000000470 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007f590841efa0 RCX: 00007f59081a5e59
RDX: 0000200000000480 RSI: 0000200000000470 RDI: 0000000001800600
RBP: 00007f590823bd6f R08: 0000200000000500 R09: 0000200000000500
R10: 00002000000004c0 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f590841f038 R14: 00007f590841efa0 R15: 00007ffcf5bd7f78
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/06/05 08:10 linux-5.15.y dc027a595035 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in dentry_kill
2026/05/27 14:03 linux-5.15.y 241d66fa280c 8777bdc3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in dentry_kill
2026/05/23 16:39 linux-5.15.y 241d66fa280c c69befb3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in dentry_kill
2026/05/06 04:01 linux-5.15.y ef251c45f1cd 26da2c66 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: rcu detected stall in dentry_kill
* Struck through repros no longer work on HEAD.