INFO: rcu detected stall in sys_pivot_root

Status: upstream: reported C repro on 2025/03/11 10:54
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+8065de3dd3b774ccd188@syzkaller.appspotmail.com
First crash: 500d, last: 434d
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/03/11 linux-6.1.y (ToT) 6ae7ac5c4251 C [report] INFO: rcu detected stall in corrupted
2025/03/11 upstream (ToT) 4d872d51bc9d C Didn't crash
▶ ▼ Similar bugs (1)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in pivot_root prio:high fs 1 syz 1 208d 204d 0/29 upstream: reported syz repro on 2026/01/02 08:20
▶ ▼ Fix bisection attempts (7)
Created Duration User Patch Repo Result
2026/06/01 12:21 14m fix candidate upstream error job log
2026/03/26 13:17 24m fix candidate upstream error job log
2026/02/24 09:15 0m fix candidate upstream error job log
2026/01/24 03:50 1m fix candidate upstream error job log
2025/06/18 20:47 16m bisect fix linux-6.1.y error job log
2025/05/16 17:22 3h52m bisect fix linux-6.1.y OK (0) job log log
2025/04/15 00:14 1h23m bisect fix linux-6.1.y OK (0) job log log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P4256/2:b..l
	(detected by 1, t=10502 jiffies, g=5877, q=42 ncpus=2)
task:syz-executor522 state:R  running task     stack:25400 pid:4256  ppid:4249   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5243 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6560
 preempt_schedule_irq+0xf7/0x1c0 kernel/sched/core.c:6872
 irqentry_exit+0x53/0x80 kernel/entry/common.c:439
 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:lock_acquire+0x26f/0x5a0 kernel/locking/lockdep.c:5666
Code: 2b 00 74 08 4c 89 f7 e8 9f 56 77 00 f6 44 24 61 02 0f 85 84 01 00 00 41 f7 c7 00 02 00 00 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 25 00 00 00 00 00 43 c7 44 25 09 00 00 00 00 43 c7 44 25
RSP: 0018:ffffc90003e87560 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 1ffff920007d0eb8 RCX: 1ffff920007d0e58
RDX: dffffc0000000000 RSI: ffffffff8b0c2ec0 RDI: ffffffff8b5f6f80
RBP: ffffc90003e876b0 R08: dffffc0000000000 R09: fffffbfff225724d
R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff920007d0eb4
R13: dffffc0000000000 R14: ffffc90003e875c0 R15: 0000000000000246
 rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 rcu_read_lock include/linux/rcupdate.h:791 [inline]
 is_bpf_text_address+0x3e/0x2a0 kernel/bpf/core.c:735
 kernel_text_address+0x9f/0xd0 kernel/extable.c:125
 __kernel_text_address+0x9/0x40 kernel/extable.c:79
 unwind_get_return_address+0x49/0x80 arch/x86/kernel/unwind_orc.c:323
 arch_stack_walk+0xf3/0x140 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x113/0x1c0 kernel/stacktrace.c:122
 save_stack+0xf6/0x1e0 mm/page_owner.c:127
 __reset_page_owner+0x52/0x1a0 mm/page_owner.c:148
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1459 [inline]
 free_pcp_prepare mm/page_alloc.c:1509 [inline]
 free_unref_page_prepare+0x12a6/0x15b0 mm/page_alloc.c:3384
 free_unref_page+0x33/0x3e0 mm/page_alloc.c:3479
 qlink_free mm/kasan/quarantine.c:168 [inline]
 qlist_free_all+0x76/0xe0 mm/kasan/quarantine.c:187
 kasan_quarantine_reduce+0x156/0x170 mm/kasan/quarantine.c:294
 __kasan_slab_alloc+0x1f/0x70 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook+0x52/0x3a0 mm/slab.h:737
 slab_alloc_node mm/slub.c:3398 [inline]
 __kmem_cache_alloc_node+0x137/0x260 mm/slub.c:3437
 kmalloc_trace+0x26/0xe0 mm/slab_common.c:1026
 kmalloc include/linux/slab.h:563 [inline]
 get_mountpoint+0x207/0x440 fs/namespace.c:794
 lock_mount+0xba/0x2c0 fs/namespace.c:2300
 __do_sys_pivot_root fs/namespace.c:3910 [inline]
 __se_sys_pivot_root+0x291/0x1640 fs/namespace.c:3884
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f78640dc849
RSP: 002b:00007ffe2ce75898 EFLAGS: 00000246 ORIG_RAX: 000000000000009b
RAX: ffffffffffffffda RBX: 00007f786412c0ff RCX: 00007f78640dc849
RDX: 00007f78640db5c7 RSI: 00007f786412c1d6 RDI: 00007f786412c0ff
RBP: 00007f786412c1d6 R08: 0000000000000000 R09: 00007ffe2ce75980
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f786413313c
R13: 00007f786412c157 R14: 0000000000000003 R15: 00007ffe2ce759e0
 </TASK>
rcu: rcu_preempt kthread starved for 10548 jiffies! g5877 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=0
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:25592 pid:16    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5243 [inline]
 __schedule+0x143f/0x4570 kernel/sched/core.c:6560
 schedule+0xbf/0x180 kernel/sched/core.c:6636
 schedule_timeout+0x1b9/0x300 kernel/time/timer.c:1965
 rcu_gp_fqs_loop+0x2d2/0x1150 kernel/rcu/tree.c:1706
 rcu_gp_kthread+0xa3/0x3b0 kernel/rcu/tree.c:1905
 kthread+0x28d/0x320 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4275 Comm: syz-executor522 Not tainted 6.1.130-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
RIP: 0010:bytes_is_nonzero mm/kasan/generic.c:84 [inline]
RIP: 0010:memory_is_nonzero mm/kasan/generic.c:102 [inline]
RIP: 0010:memory_is_poisoned_n mm/kasan/generic.c:128 [inline]
RIP: 0010:memory_is_poisoned mm/kasan/generic.c:159 [inline]
RIP: 0010:check_region_inline mm/kasan/generic.c:180 [inline]
RIP: 0010:kasan_check_range+0x74/0x290 mm/kasan/generic.c:189
Code: 49 c1 ea 03 49 bb 01 00 00 00 00 fc ff df 4f 8d 34 1a 4c 89 f5 4c 29 cd 48 83 fd 10 7f 26 48 85 ed 0f 84 3a 01 00 00 49 f7 d2 <49> 01 da 41 80 39 00 0f 85 c4 01 00 00 49 ff c1 49 ff c2 75 ee e9
RSP: 0018:ffffc90003fa7510 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 1ffffffff225724d RCX: ffffffff816b145a
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff912b9268
RBP: 0000000000000001 R08: dffffc0000000000 R09: fffffbfff225724d
R10: e00000000dda8db2 R11: dffffc0000000001 R12: ffff88802a358ad8
R13: dffffc0000000000 R14: fffffbfff225724e R15: ffff88802a358b30
FS:  000055557df1f3c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f78640f5a20 CR3: 0000000030169000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 instrument_atomic_read include/linux/instrumented.h:72 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 hlock_class kernel/locking/lockdep.c:228 [inline]
 mark_lock+0x9a/0x340 kernel/locking/lockdep.c:4606
 mark_usage kernel/locking/lockdep.c:4549 [inline]
 __lock_acquire+0xc6a/0x1f80 kernel/locking/lockdep.c:5003
 lock_acquire+0x1f8/0x5a0 kernel/locking/lockdep.c:5662
 seqcount_lockdep_reader_access+0xf8/0x220 include/linux/seqlock.h:102
 timekeeping_get_delta kernel/time/timekeeping.c:254 [inline]
 timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
 ktime_get+0x7f/0x270 kernel/time/timekeeping.c:848
 clockevents_program_event+0xe1/0x310 kernel/time/clockevents.c:326
 hrtimer_start_range_ns+0xada/0xc80 kernel/time/hrtimer.c:1303
 posixtimer_rearm+0x1ad/0x3f0 kernel/time/posix-timers.c:328
 dequeue_signal+0x245/0x590 kernel/signal.c:704
 get_signal+0x5ed/0x17a0 kernel/signal.c:2751
 arch_do_signal_or_restart+0xb0/0x1a10 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x6a/0x100 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x60/0x270 kernel/entry/common.c:303
 do_syscall_64+0x47/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f78640dc849
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 71 1d 00 00 90 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe2ce756d8 EFLAGS: 00000246
RAX: 0000000000000000 RBX: 0000000000000003 RCX: 00007f78640dc849
RDX: 000040000006b000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00007f7864094990 R09: 00007f7864094990
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f786413313c
R13: 00007f786412c157 R14: 00007ffe2ce75710 R15: 0000000000000000
 </TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.224 msecs
sched: RT throttling activated
hrtimer: interrupt took 1181310670 ns

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/03/11 10:54 linux-6.1.y 6ae7ac5c4251 16256247 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan INFO: rcu detected stall in sys_pivot_root
* Struck through repros no longer work on HEAD.