INFO: rcu detected stall in debug_check_no_obj_freed

Status: upstream: reported syz repro on 2025/11/10 02:51
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+5fcc1b3bf71ed6bc6780@syzkaller.appspotmail.com
First crash: 260d, last: 121d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/11/10 linux-5.15.y (ToT) cc5ec8769306 syz [report] INFO: rcu detected stall in corrupted
2025/11/10 upstream (ToT) e9a6fb0bcdd7 syz Didn't crash
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream BUG: soft lockup in debug_check_no_obj_freed serial 1 syz 2 646d 646d 0/29 auto-obsoleted due to no activity on 2025/01/27 15:36
linux-6.6 INFO: rcu detected stall in debug_check_no_obj_freed origin:lts-only 1 C error 1 226d 258d 0/2 upstream: reported C repro on 2025/11/11 10:45
upstream INFO: rcu detected stall in debug_check_no_obj_freed fs 1 1 541d 541d 0/29 auto-obsoleted due to no activity on 2025/05/03 06:53
upstream BUG: soft lockup in debug_check_no_obj_freed (2) kernel 1 1 233d 233d 0/29 closed as invalid on 2026/01/09 17:04
▶ ▼ Last patch testing requests (5)
Created Duration User Patch Repo Result
2026/06/21 12:59 17m retest repro linux-5.15.y report log
2026/06/21 12:59 20m retest repro linux-5.15.y report log
2026/04/12 01:03 20m retest repro linux-5.15.y report log
2026/04/12 01:03 12m retest repro linux-5.15.y report log
2026/01/20 09:05 15m retest repro linux-5.15.y error
▶ ▼ Fix bisection attempts (6)
Created Duration User Patch Repo Result
2026/07/12 02:58 30m fix candidate upstream error job log
2026/05/26 13:58 18m fix candidate upstream error job log
2026/03/24 16:39 34m fix candidate upstream error job log
2026/02/22 14:59 1m fix candidate upstream error job log
2026/01/23 13:07 1m fix candidate upstream error job log
2025/11/18 21:07 0m fix candidate upstream error

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	0-....: (1 GPs behind) idle=c2b/1/0x4000000000000000 softirq=7111/7112 fqs=5250 
	(detected by 1, t=10502 jiffies, g=8269, q=385)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4409 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:check_wait_context kernel/locking/lockdep.c:-1 [inline]
RIP: 0010:__lock_acquire+0x9a5/0x7d10 kernel/locking/lockdep.c:4962
Code: 4c 89 f0 48 c1 e8 03 42 0f b6 04 00 84 c0 0f 85 e9 00 00 00 41 0f b6 06 84 c0 74 0e 41 0f b6 cd 44 0f b6 e8 38 c1 44 0f 42 e9 <48> 8b 84 24 88 00 00 00 42 0f b6 04 00 84 c0 0f 85 e3 00 00 00 48
RSP: 0018:ffffc900000070a0 EFLAGS: 00000046
RAX: 0000000000000002 RBX: 0000000000000000 RCX: 0000000000000002
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff901d40c0
RBP: ffffc900000072f0 R08: dffffc0000000000 R09: 1ffffffff203a818
R10: dffffc0000000000 R11: fffffbfff203a819 R12: ffff888017bf4690
R13: 0000000000000002 R14: ffffffff8fb5cff8 R15: ffff888017bf4690
FS:  000055557911a500(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b30863fff CR3: 0000000020029000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:313
 rcu_read_lock include/linux/rcupdate.h:740 [inline]
 __perf_event_output kernel/events/core.c:7800 [inline]
 perf_event_output_forward+0xbc/0x2e0 kernel/events/core.c:7822
 __perf_event_overflow+0x364/0x530 kernel/events/core.c:9515
 perf_swevent_overflow kernel/events/core.c:9591 [inline]
 perf_swevent_event+0x4ad/0x530 kernel/events/core.c:9629
 perf_tp_event+0x383/0xbf0 kernel/events/core.c:10047
 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 12 f2 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:ffffc90000007b00 EFLAGS: 00000206
RAX: 90a3d73cea550100 RBX: 1ffff92000000f64 RCX: 90a3d73cea550100
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: ffffffff8a79f980
RBP: ffffc90000007bd8 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: ffffffff8c322f00
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]
 ieee80211_iterate_active_interfaces_atomic+0x132/0x140 net/mac80211/util.c:831
 mac80211_hwsim_beacon+0x9b/0x180 drivers/net/wireless/mac80211_hwsim.c:1865
 __run_hrtimer kernel/time/hrtimer.c:1685 [inline]
 __hrtimer_run_queues+0x4f2/0xb70 kernel/time/hrtimer.c:1749
 hrtimer_run_softirq+0x176/0x240 kernel/time/hrtimer.c:1766
 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> 2f 8a 8c f7 65 8b 05 d0 97 3c 76 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc9000337fc00 EFLAGS: 00000206
RAX: dffffc0000000004 RBX: 0000000000000a02 RCX: 90a3d73cea550100
RDX: dffffc0000000000 RSI: ffffffff8a2b2780 RDI: 0000000000000001
RBP: ffffc9000337fc98 R08: ffff8880b903b30b R09: 1ffff11017207661
R10: dffffc0000000000 R11: ffffed1017207662 R12: dffffc0000000000
R13: ffff888019bcc070 R14: ffffffff9651e4a8 R15: 1ffff9200066ff80
 __debug_check_no_obj_freed lib/debugobjects.c:982 [inline]
 debug_check_no_obj_freed+0x515/0x530 lib/debugobjects.c:1003
 slab_free_hook mm/slub.c:1685 [inline]
 slab_free_freelist_hook+0x8b/0x170 mm/slub.c:1736
 slab_free mm/slub.c:3504 [inline]
 kmem_cache_free+0x8f/0x210 mm/slub.c:3520
 file_free fs/file_table.c:55 [inline]
 __fput+0x627/0x930 fs/file_table.c:324
 task_work_run+0x125/0x1a0 kernel/task_work.c:188
 tracehook_notify_resume include/linux/tracehook.h:189 [inline]
 exit_to_user_mode_loop+0x10f/0x130 kernel/entry/common.c:181
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f479f098819
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:00007ffc9450d8a8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007f479f313da0 RCX: 00007f479f098819
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 00007f479f313da0 R08: 00007f479f312038 R09: 0000000000000000
R10: 000000000003fde0 R11: 0000000000000246 R12: 000000000001c2c6
R13: 00007f479f311fac R14: 000000000001bfb9 R15: 00007ffc9450d9b0
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/28 23:32 linux-5.15.y 91d48252ad4b b5ceaad2 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in debug_check_no_obj_freed
2025/11/10 02:51 linux-5.15.y cc5ec8769306 4e1406b4 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: rcu detected stall in debug_check_no_obj_freed
* Struck through repros no longer work on HEAD.