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INFO: rcu detected stall in sys_symlink (6)

Status: upstream: reported C repro on 2025/10/27 21:18
Subsystems: tomoyo fs mm
[Documentation on labels]
Reported-by: syzbot+e538d3da32f1c0337b01@syzkaller.appspotmail.com
First crash: 60d, last: 2d16h
Cause bisection: failed (error log, bisect log)
  
Fix bisection: the issue occurs on the latest tested release (bisect log)
  
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[syzbot] Monthly input report (Nov 2025) 0 (1) 2025/11/17 07:50
[syzbot] [lsm?] [input?] [usb?] INFO: rcu detected stall in sys_symlink (6) 0 (1) 2025/10/27 21:18
▶ ▼ Similar bugs (7)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sys_symlink 1 1 5d04h 5d04h 0/3 upstream: reported on 2025/12/21 12:04
upstream INFO: rcu detected stall in sys_symlink (3) mm 1 4 2179d 2179d 0/29 closed as invalid on 2020/01/09 08:13
upstream INFO: rcu detected stall in sys_symlink (2) mm cgroups 1 2 2179d 2179d 0/29 closed as invalid on 2020/01/08 05:23
linux-6.6 INFO: rcu detected stall in sys_symlink 1 1 180d 180d 0/2 auto-obsoleted due to no activity on 2025/10/07 08:06
upstream INFO: rcu detected stall in sys_symlink mm 1 17 2214d 2215d 0/29 closed as invalid on 2019/12/04 14:14
upstream INFO: rcu detected stall in sys_symlink (4) bpf 1 11 1442d 1546d 0/29 closed as invalid on 2022/02/08 09:50
upstream INFO: rcu detected stall in sys_symlink (5) mm fs 1 syz inconclusive done 6 391d 441d 0/29 closed as invalid on 2025/02/03 10:48
▶ ▼ Last patch testing requests (1)
Created Duration User Patch Repo Result
2025/11/09 18:14 27m retest repro upstream report log

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5960/1:b..l P5953/1:b..l
rcu: 	(detected by 0, t=10502 jiffies, g=8065, q=370 ncpus=2)
task:kworker/1:9     state:R  running task     stack:23704 pid:5953  tgid:5953  ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: events_power_efficient gc_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1139/0x6150 kernel/sched/core.c:6863
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7190
 irqentry_exit+0x1d8/0x8c0 kernel/entry/common.c:216
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:lock_release+0x183/0x2d0 kernel/locking/lockdep.c:5893
Code: 0f c1 05 48 01 19 12 83 f8 01 0f 85 03 01 00 00 9c 58 f6 c4 02 0f 85 ee 00 00 00 41 f7 c5 00 02 00 00 74 01 fb 48 8b 44 24 10 <65> 48 2b 05 dd b9 18 12 0f 85 32 01 00 00 48 83 c4 18 5b 41 5c 41
RSP: 0018:ffffc90002fd7a90 EFLAGS: 00000206
RAX: 68c6c5ea27bed900 RBX: ffffffff8e3c96a0 RCX: ffffc90002fd7a9c
RDX: 0000000000000002 RSI: ffffffff8daa7ea1 RDI: ffffffff8bf2b400
RBP: ffffffff9b0a38ac R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000001 R11: ffff888035cdaff0 R12: ffffffff89940a39
R13: 0000000000000206 R14: ffff888035cda4c0 R15: 0000000000000003
 rcu_lock_release include/linux/rcupdate.h:341 [inline]
 rcu_read_unlock include/linux/rcupdate.h:897 [inline]
 gc_worker+0x99e/0x16e0 net/netfilter/nf_conntrack_core.c:1617
 process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257
 process_scheduled_works kernel/workqueue.c:3340 [inline]
 worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246
 </TASK>
task:syz-executor248 state:R  running task     stack:28792 pid:5960  tgid:5960  ppid:5833   task_flags:0x400040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1139/0x6150 kernel/sched/core.c:6863
 preempt_schedule_irq+0x51/0x90 kernel/sched/core.c:7190
 irqentry_exit+0x1d8/0x8c0 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x62/0x330 kernel/locking/lockdep.c:5872
Code: b4 18 12 83 f8 07 0f 87 a2 02 00 00 89 c0 48 0f a3 05 72 b9 ee 0e 0f 82 74 02 00 00 8b 35 0a ea ee 0e 85 f6 0f 85 8d 00 00 00 <48> 8b 44 24 30 65 48 2b 05 89 b4 18 12 0f 85 ad 02 00 00 48 83 c4
RSP: 0018:ffffc90003097570 EFLAGS: 00000206
RAX: 0000000000000046 RBX: ffffffff8e3c96a0 RCX: 000000007a0f8404
RDX: 0000000000000000 RSI: ffffffff8daa7ea1 RDI: ffffffff8bf2b400
RBP: 0000000000000002 R08: 0000000077c9b173 R09: 00000000377c9b17
R10: 0000000000000002 R11: ffff888031f38b30 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 rcu_read_lock include/linux/rcupdate.h:867 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0xd1/0x20b0 arch/x86/kernel/unwind_orc.c:495
 arch_stack_walk+0x94/0x100 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x8e/0xc0 kernel/stacktrace.c:122
 kasan_save_stack+0x33/0x60 mm/kasan/common.c:56
 kasan_save_track+0x14/0x30 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:397 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:414
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __do_kmalloc_node mm/slub.c:5657 [inline]
 __kmalloc_noprof+0x33d/0x910 mm/slub.c:5669
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 tomoyo_encode2+0x100/0x3e0 security/tomoyo/realpath.c:45
 tomoyo_encode+0x29/0x50 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x18f/0x6e0 security/tomoyo/realpath.c:283
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x274/0x460 security/tomoyo/file.c:822
 tomoyo_path_symlink+0x97/0xe0 security/tomoyo/tomoyo.c:212
 security_path_symlink+0x152/0x2e0 security/security.c:1476
 do_symlinkat+0x126/0x4b0 fs/namei.c:5539
 __do_sys_symlink fs/namei.c:5567 [inline]
 __se_sys_symlink fs/namei.c:5565 [inline]
 __x64_sys_symlink+0x75/0x90 fs/namei.c:5565
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcd12c779b7
RSP: 002b:00007ffdcf644ef8 EFLAGS: 00000206 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fcd12c779b7
RDX: 0000000000000009 RSI: 00007fcd12cc604e RDI: 00007fcd12cc6059
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 00007fcd12cc64e1
R13: 0000000000000003 R14: 00007ffdcf644f30 R15: 0000000000000000
 </TASK>
rcu: rcu_preempt kthread starved for 10567 jiffies! g8065 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:28328 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5256 [inline]
 __schedule+0x1139/0x6150 kernel/sched/core.c:6863
 __schedule_loop kernel/sched/core.c:6945 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6960
 schedule_timeout+0x123/0x290 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x1ea/0xaf0 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x26d/0x380 kernel/rcu/tree.c:2285
 kthread+0x3c5/0x780 kernel/kthread.c:463
 ret_from_fork+0x983/0xb10 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:
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
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+0xf/0x20 arch/x86/kernel/paravirt.c:82
Code: c6 5f 02 c3 cc cc cc cc 0f 1f 00 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 13 49 12 00 fb f4 <e9> cc 35 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffc90000197de8 EFLAGS: 000002c6
RAX: 00000000000ee8a3 RBX: 0000000000000001 RCX: ffffffff8b7816d9
RDX: 0000000000000000 RSI: ffffffff8dacdf23 RDI: ffffffff8bf2b400
RBP: ffffed1003b57498 R08: 0000000000000001 R09: ffffed10170a673d
R10: ffff8880b85339eb R11: ffff88801dabaff0 R12: 0000000000000001
R13: ffff88801daba4c0 R14: ffffffff9088b4d0 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881249f5000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fcd12c9f150 CR3: 000000007bae7000 CR4: 00000000003526f0
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+0x6c/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x38d/0x510 kernel/sched/idle.c:332
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:430
 start_secondary+0x21d/0x2d0 arch/x86/kernel/smpboot.c:312
 common_startup_64+0x13e/0x148
 </TASK>

Crashes (4):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/23 23:41 upstream b927546677c8 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_symlink
2025/10/26 17:08 upstream 72761a7e3122 c0460fcd .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_symlink
2025/12/23 17:43 linux-next cc3aa43b44bd d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_symlink
2025/11/15 18:10 upstream 7a0892d2836e f7988ea4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in sys_symlink
* Struck through repros no longer work on HEAD.