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INFO: rcu detected stall in sys_readlink

Status: upstream: reported on 2025/11/30 09:31
Reported-by: syzbot+3002409a7f7a90f185b9@syzkaller.appspotmail.com
First crash: 112d, last: 1d14h
▶ ▼ Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_readlink (2) kernel 1 3 1165d 1225d 0/29 auto-obsoleted due to no activity on 2023/04/24 08:02
linux-5.15 INFO: rcu detected stall in sys_readlink (4) 1 4 84d 166d 0/3 upstream: reported on 2025/10/07 07:00
linux-5.15 INFO: rcu detected stall in sys_readlink 1 1 935d 935d 0/3 auto-obsoleted due to no activity on 2023/12/08 09:32
upstream INFO: rcu detected stall in sys_readlink fs 1 1 1429d 1429d 0/29 auto-closed as invalid on 2022/07/22 05:22
linux-5.15 INFO: rcu detected stall in sys_readlink (2) 1 3 599d 624d 0/3 auto-obsoleted due to no activity on 2024/11/07 23:07
upstream INFO: rcu detected stall in sys_readlink (4) fs 1 2 839d 843d 0/29 auto-obsoleted due to no activity on 2024/03/02 18:22
linux-6.1 INFO: rcu detected stall in sys_readlink (2) 1 2 247d 275d 0/3 auto-obsoleted due to no activity on 2025/10/26 06:03
linux-6.1 INFO: rcu detected stall in sys_readlink 1 4 408d 598d 0/3 auto-obsoleted due to no activity on 2025/05/18 03:23
upstream INFO: rcu detected stall in sys_readlink (3) fs bpf 1 2 1041d 1047d 0/29 auto-obsoleted due to no activity on 2023/08/14 04:05
upstream INFO: rcu detected stall in sys_readlink (5) kernfs mm 1 syz done error 45 12d 520d 0/29 upstream: reported syz repro on 2024/10/18 11:28
linux-5.15 INFO: rcu detected stall in sys_readlink (3) 1 3 270d 403d 0/3 auto-obsoleted due to no activity on 2025/10/02 16:41
android-5-15 BUG: soft lockup in sys_readlink 1 2 650d 708d 0/2 auto-obsoleted due to no activity on 2024/09/08 11:06

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P19700/1:b..l P5137/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=203317, q=192 ncpus=2)
task:udevd           state:R  running task     stack:23048 pid:5137  ppid:1      flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_irq+0xbf/0x150 kernel/sched/core.c:7010
 irqentry_exit+0x67/0x70 kernel/entry/common.c:438
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:lock_acquire+0x208/0x420 kernel/locking/lockdep.c:5758
Code: f7 84 24 80 00 00 00 00 02 00 00 43 c6 44 3c 04 f8 0f 85 f0 00 00 00 41 f7 c6 00 02 00 00 74 01 fb 48 c7 44 24 60 0e 36 e0 45 <4b> c7 04 3c 00 00 00 00 43 c7 44 3c 08 00 00 00 00 65 48 8b 04 25
RSP: 0018:ffffc90003297820 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: fedfd28e6f9a5600
RDX: 0000000000000000 RSI: ffffffff8acadae0 RDI: ffffffff8b1c85a0
RBP: ffffc90003297930 R08: dffffc0000000000 R09: 1ffffffff22382a0
R10: dffffc0000000000 R11: fffffbfff22382a1 R12: 1ffff92000652f10
R13: ffffffff8d132060 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 __d_lookup+0xac/0x7c0 fs/dcache.c:2489
 lookup_fast+0x7c/0x4d0 fs/namei.c:1660
 walk_component fs/namei.c:2006 [inline]
 link_path_walk+0x5ff/0xe30 fs/namei.c:2337
 path_lookupat+0x9d/0x440 fs/namei.c:2490
 filename_lookup+0x228/0x560 fs/namei.c:2520
 user_path_at_empty+0x42/0x60 fs/namei.c:2917
 do_readlinkat+0xdd/0x490 fs/stat.c:494
 __do_sys_readlink fs/stat.c:527 [inline]
 __se_sys_readlink fs/stat.c:524 [inline]
 __x64_sys_readlink+0x7f/0x90 fs/stat.c:524
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f29065153a7
RSP: 002b:00007ffdde038cc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000059
RAX: ffffffffffffffda RBX: 00007ffdde0391a0 RCX: 00007f29065153a7
RDX: 0000000000000400 RSI: 00007ffdde038cd0 RDI: 00007ffdde0391a0
RBP: 00007ffdde038cd0 R08: 0000555683ac8e04 R09: 0000000000000001
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000400
R13: 00000000000000ff R14: 0000555662034be0 R15: 00007ffdde039c60
 </TASK>
task:syz-executor    state:R  running task     stack:21704 pid:19700 ppid:19689  flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 __raw_spin_unlock include/linux/spinlock_api_smp.h:143 [inline]
 _raw_spin_unlock+0x3a/0x40 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:391 [inline]
 copy_pte_range mm/memory.c:1107 [inline]
 copy_pmd_range mm/memory.c:1168 [inline]
 copy_pud_range mm/memory.c:1205 [inline]
 copy_p4d_range mm/memory.c:1229 [inline]
 copy_page_range+0x2ba0/0x3670 mm/memory.c:1323
 dup_mmap kernel/fork.c:764 [inline]
 dup_mm kernel/fork.c:1692 [inline]
 copy_mm+0x11cb/0x1d50 kernel/fork.c:1741
 copy_process+0x16f7/0x3d80 kernel/fork.c:2506
 kernel_clone+0x24b/0x8a0 kernel/fork.c:2914
 __do_sys_clone kernel/fork.c:3057 [inline]
 __se_sys_clone kernel/fork.c:3041 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:3041
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc8d11c5212
RSP: 002b:00007fffd2fe8f70 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fffd2fe8f70 RCX: 00007fc8d11c5212
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007fffd2fe90fc R08: 0000000000000000 R09: 0000000000000001
R10: 0000555581ec27d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 00000000001c2dea R15: 00007fffd2fe9150
 </TASK>
rcu: rcu_preempt kthread starved for 10445 jiffies! g203317 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:27344 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 1 PID: 0 Comm: swapper/1 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
RIP: 0010:pv_native_safe_halt+0xf/0x10 arch/x86/kernel/paravirt.c:148
Code: 40 22 02 c3 cc cc cc cc cc cc cc f3 0f 1e fa 0f 0b 66 2e 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 66 90 0f 00 2d c3 29 43 00 fb f4 <c3> 66 0f 1f 00 55 41 57 41 56 41 54 53 50 8b 2f eb 2e 41 89 de 80
RSP: 0018:ffffc90000187de0 EFLAGS: 000002c6
RAX: 30f799da78cc2200 RBX: ffffffff8162ac40 RCX: 30f799da78cc2200
RDX: 0000000000000001 RSI: ffffffff8acac960 RDI: ffffffff8b1c85a0
RBP: ffffc90000187f20 R08: ffff8880b8f36b2b R09: 1ffff110171e6d65
R10: dffffc0000000000 R11: ffffed10171e6d66 R12: 1ffff110036cd780
R13: 1ffff92000030fc8 R14: 0000000000000001 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005555925884e8 CR3: 0000000025f0a000 CR4: 00000000003506e0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:108 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:753
 default_idle_call+0x6c/0xa0 kernel/sched/idle.c:97
 cpuidle_idle_call kernel/sched/idle.c:170 [inline]
 do_idle+0x1f0/0x4e0 kernel/sched/idle.c:282
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:380
 start_secondary+0xee/0xf0 arch/x86/kernel/smpboot.c:323
 secondary_startup_64_no_verify+0x179/0x17b
 </TASK>

Crashes (3):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/20 22:51 linux-6.6.y 4fc00fe35d46 ac6f1dff .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_readlink
2026/01/13 21:24 linux-6.6.y c596736dadab d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_readlink
2025/11/30 09:30 linux-6.6.y 1e89a1be4fe9 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_readlink
* Struck through repros no longer work on HEAD.