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INFO: rcu detected stall in sys_newfstat (4)

Status: upstream: reported C repro on 2025/12/22 03:48
Subsystems: tomoyo
[Documentation on labels]
Reported-by: syzbot+5fb7dcd004f42cb418d7@syzkaller.appspotmail.com
First crash: 57d, last: 3d09h
Cause bisection: failed (error log, bisect log)
  
▶ ▼ Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [tomoyo?] [mm?] INFO: rcu detected stall in sys_newfstat (4) 0 (2) 2025/12/24 15:25
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: rcu detected stall in sys_newfstat 1 1 37d 37d 0/3 upstream: reported on 2025/12/14 02:05
linux-6.6 INFO: rcu detected stall in sys_newfstat 1 1 210d 210d 0/2 auto-obsoleted due to no activity on 2025/10/02 03:58
linux-5.15 INFO: rcu detected stall in sys_newfstat 1 6 1d07h 225d 0/3 upstream: reported on 2025/06/09 10:15
upstream INFO: rcu detected stall in sys_newfstat (2) mm 1 1 2204d 2204d 0/29 closed as invalid on 2020/01/08 05:33
upstream INFO: rcu detected stall in sys_newfstat mm 1 1 2239d 2239d 0/29 closed as invalid on 2019/12/04 14:04

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P5874/1:b..l P5857/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=11205, q=25 ncpus=2)
task:udevd           state:R  running task     stack:25240 pid:5857  tgid:5857  ppid:5198   task_flags:0x400140 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5258 [inline]
 __schedule+0x150e/0x5070 kernel/sched/core.c:6866
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7193
 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:debug_lockdep_rcu_enabled+0xf/0x40 kernel/rcu/update.c:320
Code: 48 0f b9 3a 90 eb ca cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 31 c0 83 3d 17 78 44 04 00 74 1e <83> 3d 2a a7 44 04 00 74 15 65 48 8b 0c 25 08 b0 9f 92 31 c0 83 b9
RSP: 0018:ffffc9000425f510 EFLAGS: 00000202
RAX: 0000000000000000 RBX: ffffffff8228283e RCX: f504a25577f97f00
RDX: 00000000c1e3b5cc RSI: ffffffff8db7ed49 RDI: ffffffff8be07960
RBP: dffffc0000000000 R08: ffffffff81742f85 R09: ffffffff8e13f2e0
R10: ffffc9000425f638 R11: ffffffff81ad9d50 R12: 1ffff9200084bebd
R13: ffffc9000425f620 R14: ffffc9000425f5e8 R15: ffffffff81742f85
 rcu_read_lock include/linux/rcupdate.h:868 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1195 [inline]
 unwind_next_frame+0xcb/0x23d0 arch/x86/kernel/unwind_orc.c:495
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __do_kmalloc_node mm/slub.c:5661 [inline]
 __kmalloc_noprof+0x41d/0x800 mm/slub.c:5673
 kmalloc_noprof include/linux/slab.h:961 [inline]
 kzalloc_noprof include/linux/slab.h:1094 [inline]
 tomoyo_encode2 security/tomoyo/realpath.c:45 [inline]
 tomoyo_encode+0x28b/0x550 security/tomoyo/realpath.c:80
 tomoyo_realpath_from_path+0x58d/0x5d0 security/tomoyo/realpath.c:283
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_path_perm+0x213/0x4b0 security/tomoyo/file.c:822
 security_inode_getattr+0x12f/0x330 security/security.c:1869
 vfs_getattr fs/stat.c:259 [inline]
 vfs_fstat fs/stat.c:281 [inline]
 __do_sys_newfstat fs/stat.c:555 [inline]
 __se_sys_newfstat fs/stat.c:550 [inline]
 __x64_sys_newfstat+0xfc/0x200 fs/stat.c:550
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2f2b711ad7
RSP: 002b:00007ffeeebbb7b8 EFLAGS: 00000297 ORIG_RAX: 0000000000000005
RAX: ffffffffffffffda RBX: 0000564ba16cb8a0 RCX: 00007f2f2b711ad7
RDX: 00007f2f2b7efea0 RSI: 00007ffeeebbb7c0 RDI: 0000000000000008
RBP: 00007f2f2b7efff0 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000297 R12: 000000000000000a
R13: 0000000000003fff R14: 0000000000000000 R15: 0000564ba16cb8a0
 </TASK>
task:syz-executor360 state:R  running task     stack:25816 pid:5874  tgid:5867  ppid:5855   task_flags:0x400040 flags:0x00080800
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5258 [inline]
 __schedule+0x150e/0x5070 kernel/sched/core.c:6866
 preempt_schedule_irq+0xb5/0x150 kernel/sched/core.c:7193
 irqentry_exit+0x5d8/0x660 kernel/entry/common.c:216
 asm_sysvec_reschedule_ipi+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:unwind_next_frame+0x18cc/0x23d0 arch/x86/kernel/unwind_orc.c:-1
Code: 30 0a 00 00 4c 89 e8 48 c1 e8 03 0f b6 04 28 84 c0 0f 85 43 0a 00 00 49 0f bf 04 24 48 01 c6 4c 89 f7 48 89 da e8 84 0d 00 00 <84> c0 0f 84 47 01 00 00 48 bd 00 00 00 00 00 fc ff df 48 8b 44 24
RSP: 0018:ffffc9000436f2b8 EFLAGS: 00000282
RAX: 1ffff9200086de01 RBX: ffffffff90315ccc RCX: 0000000000000001
RDX: ffffc9000436f3c8 RSI: dffffc0000000000 RDI: ffffc9000436f978
RBP: dffffc0000000000 R08: ffffc9000436f978 R09: 0000000000000000
R10: ffffc9000436f3d8 R11: fffff5200086de7d R12: ffffc9000436f3d8
R13: 1ffff9200086de73 R14: ffffc9000436f388 R15: 1ffffffff2062b99
 arch_stack_walk+0x11c/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 unpoison_slab_object mm/kasan/common.c:340 [inline]
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4953 [inline]
 slab_alloc_node mm/slub.c:5267 [inline]
 kmem_cache_alloc_lru_noprof+0x36c/0x6e0 mm/slub.c:5286
 alloc_inode+0x6a/0x1b0 fs/inode.c:346
 new_inode+0x22/0x170 fs/inode.c:1175
 debugfs_get_inode fs/debugfs/inode.c:72 [inline]
 __debugfs_create_file+0xb8/0x400 fs/debugfs/inode.c:433
 debugfs_create_file_full+0x3f/0x60 fs/debugfs/inode.c:460
 kvm_arch_create_vcpu_debugfs+0x41/0x160 arch/x86/kvm/debugfs.c:61
 kvm_create_vcpu_debugfs+0x138/0x1a0 virt/kvm/kvm_main.c:4167
 kvm_vm_ioctl_create_vcpu+0x62a/0x930 virt/kvm/kvm_main.c:4271
 kvm_vm_ioctl+0x7f7/0xc60 virt/kvm/kvm_main.c:5180
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xfc/0x170 fs/ioctl.c:583
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa7ebb76d89
RSP: 002b:00007fa7ebb05218 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fa7ebbfb3f8 RCX: 00007fa7ebb76d89
RDX: 0000000000000000 RSI: 000000000000ae41 RDI: 0000000000000004
RBP: 00007fa7ebbfb3f0 R08: 00007ffddfa031f7 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fa7ebbc72e4
R13: 0000200000000000 R14: 0000200000000140 R15: 0000200000000040
 </TASK>
rcu: rcu_preempt kthread starved for 10587 jiffies! g11205 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:26264 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5258 [inline]
 __schedule+0x150e/0x5070 kernel/sched/core.c:6866
 __schedule_loop kernel/sched/core.c:6948 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6963
 schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
 rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x599/0xb30 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 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 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+0x13/0x20 arch/x86/kernel/paravirt.c:82
Code: cc cc cc cc cc cc cc 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 33 9e 2a 00 f3 0f 1e fa fb f4 <e9> 48 ee 02 00 cc cc cc cc cc cc cc cc 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffffff8de07d80 EFLAGS: 000002c6
RAX: e8fee117958a6b00 RBX: ffffffff819786ba RCX: e8fee117958a6b00
RDX: 0000000000000001 RSI: ffffffff8d997e54 RDI: ffffffff8be07960
RBP: ffffffff8de07ea8 R08: ffff8880b86336db R09: 1ffff110170c66db
R10: dffffc0000000000 R11: ffffed10170c66dc R12: ffffffff8fa22f70
R13: 1ffffffff1bd29b8 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888125c25000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa7ebb2da90 CR3: 0000000074c04000 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+0x73/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x1ea/0x520 kernel/sched/idle.c:332
 cpu_startup_entry+0x44/0x60 kernel/sched/idle.c:430
 rest_init+0x2de/0x300 init/main.c:758
 start_kernel+0x3ac/0x400 init/main.c:1208
 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x147
 </TASK>

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/12/24 15:24 linux-next cc3aa43b44bd d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_newfstat
2025/12/18 09:53 linux-next 12b95d29eb97 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: rcu detected stall in sys_newfstat
2025/12/18 03:36 linux-next 12b95d29eb97 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: rcu detected stall in sys_newfstat
2026/01/17 06:28 upstream 39d3389331ab d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_newfstat
2025/12/23 15:17 upstream b927546677c8 d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_newfstat
2025/12/10 21:22 upstream 0048fbb4011e d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_newfstat
2025/11/23 22:17 upstream d13f3ac64efb 4fb8ef37 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in sys_newfstat
2026/01/04 22:30 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_newfstat
2026/01/01 22:15 linux-next cc3aa43b44bd d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_newfstat
* Struck through repros no longer work on HEAD.