INFO: rcu detected stall in sys_clone

Status: fixed on 2025/12/06 23:11
Reported-by: syzbot+4a0c2a1f63c5084ccdd9@syzkaller.appspotmail.com
Fix commit: b41642c87716 rcu: Fix rcu_read_unlock() deadloop due to IRQ work
First crash: 352d, last: 267d
Fix bisection: fixed by (bisect log) :
commit e7a375453cca2b8a0d2fa1b82b913f3fed7c0507
Author: Joel Fernandes <joelagnelf@nvidia.com>
Date: Tue Jul 8 14:22:19 2025 +0000

  rcu: Fix rcu_read_unlock() deadloop due to IRQ work

  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2025/09/15 upstream (ToT) f83ec76bf285 C Didn't crash
▶ ▼ Similar bugs (19)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-5.15 INFO: rcu detected stall in sys_clone 1 1 966d 966d 0/3 auto-obsoleted due to no activity on 2024/03/15 18:08
linux-6.1 INFO: rcu detected stall in sys_clone 1 3 1113d 1186d 0/3 auto-obsoleted due to no activity on 2023/10/20 18:18
upstream INFO: rcu detected stall in sys_clone (2) mm 1 49 2340d 2456d 0/29 auto-closed as invalid on 2020/06/01 05:26
upstream INFO: rcu detected stall in sys_clone (4) kernel 1 1 1856d 1856d 0/29 auto-closed as invalid on 2021/09/27 17:49
upstream INFO: rcu detected stall in sys_clone (3) mm 1 2 2192d 2214d 0/29 auto-closed as invalid on 2020/10/26 22:48
upstream INFO: rcu detected stall in sys_clone (6) kasan mm 1 1 1527d 1527d 0/29 auto-closed as invalid on 2022/08/23 03:28
upstream INFO: rcu detected stall in sys_clone kernel 1 1 2513d 2513d 13/29 fixed on 2019/10/09 10:54
upstream INFO: rcu detected stall in sys_clone (8) mm 1 syz, C error 470 4h49m 853d 0/29 upstream: reported C repro on 2024/03/29 00:16
linux-4.19 INFO: rcu detected stall in sys_clone 1 2 2411d 2430d 0/1 auto-closed as invalid on 2020/04/21 05:46
upstream INFO: rcu detected stall in sys_clone (5) kernfs 1 5 1661d 1761d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in sys_clone (7) fs 1 1 1262d 1262d 0/29 auto-obsoleted due to no activity on 2023/05/14 17:18
linux-5.15 INFO: rcu detected stall in sys_clone (2) missing-backport origin:upstream 1 syz, C done 168 3d09h 855d 0/3 upstream: reported C repro on 2024/03/27 00:16
linux-6.1 INFO: rcu detected stall in sys_clone (2) origin:upstream missing-backport 1 syz, C error 92 6d08h 862d 0/3 upstream: reported C repro on 2024/03/20 15:17
linux-6.6 INFO: rcu detected stall in sys_clone (2) 1 20 1d10h 233d 0/2 upstream: reported on 2025/12/09 09:13
android-5-10 BUG: soft lockup in sys_clone 1 1 752d 752d 0/2 auto-obsoleted due to no activity on 2024/10/06 12:58
android-5-10 BUG: soft lockup in sys_clone (2) 1 1 326d 326d 0/2 auto-obsoleted due to no activity on 2025/12/06 02:03
android-5-10 BUG: soft lockup in sys_clone (4) 1 1 53d 53d 0/2 premoderation: reported on 2026/06/07 05:26
android-5-10 BUG: soft lockup in sys_clone (3) 1 1 178d 178d 0/2 auto-obsoleted due to no activity on 2026/05/02 19:39
android-5-15 BUG: soft lockup in sys_clone origin:upstream 1 syz, C error 18 688d 831d 0/2 auto-obsoleted due to no activity on 2024/12/19 12:14

Sample crash report:
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P12029/1:b..l P12023/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=60149, q=46 ncpus=2)
task:syz.0.1975      state:R  running task     stack:24616 pid:12023 ppid:5785   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_irq+0xb5/0x140 kernel/sched/core.c:7009
 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+0x1f2/0x410 kernel/locking/lockdep.c:5758
Code: 00 9c 8f 84 24 80 00 00 00 f6 84 24 81 00 00 00 02 0f 85 f5 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 66 43 c7 44 3c 09 00 00 43 c6 44 3c 0b 00
RSP: 0018:ffffc9001083ea60 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 2a5feed0747ce000
RDX: 0000000000000000 RSI: ffffffff8aaace60 RDI: ffffffff8afc6b00
RBP: ffffc9001083eb70 R08: dffffc0000000000 R09: 1ffffffff21b50a0
R10: dffffc0000000000 R11: fffffbfff21b50a1 R12: 1ffff92002107d58
R13: ffffffff8cd2fee0 R14: 0000000000000246 R15: dffffc0000000000
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 is_bpf_text_address+0x47/0x2a0 kernel/bpf/core.c:741
 kernel_text_address+0xa0/0xd0 kernel/extable.c:125
 __kernel_text_address+0xd/0x30 kernel/extable.c:79
 unwind_get_return_address+0x5d/0xc0 arch/x86/kernel/unwind_orc.c:369
 arch_stack_walk+0x11d/0x190 arch/x86/kernel/stacktrace.c:26
 stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:328
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 slab_alloc mm/slub.c:3503 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3510 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3519
 kmem_cache_zalloc include/linux/slab.h:711 [inline]
 __kernfs_new_node+0xd8/0x7e0 fs/kernfs/dir.c:624
 kernfs_new_node+0x14c/0x260 fs/kernfs/dir.c:700
 __kernfs_create_file+0x4b/0x2e0 fs/kernfs/file.c:1068
 sysfs_add_file_mode_ns+0x238/0x300 fs/sysfs/file.c:294
 create_files fs/sysfs/group.c:64 [inline]
 internal_create_group+0x428/0xd00 fs/sysfs/group.c:152
 internal_create_groups fs/sysfs/group.c:192 [inline]
 sysfs_create_groups+0x59/0x120 fs/sysfs/group.c:218
 setup_gid_attrs drivers/infiniband/core/sysfs.c:1174 [inline]
 ib_setup_port_attrs+0x1401/0x2040 drivers/infiniband/core/sysfs.c:1451
 add_one_compat_dev+0x3d6/0x5c0 drivers/infiniband/core/device.c:978
 rdma_dev_init_net+0x1da/0x270 drivers/infiniband/core/device.c:1194
 ops_init+0x397/0x640 net/core/net_namespace.c:139
 setup_net+0x3a5/0xa00 net/core/net_namespace.c:343
 copy_net_ns+0x36d/0x5e0 net/core/net_namespace.c:520
 create_new_namespaces+0x3d3/0x6f0 kernel/nsproxy.c:110
 copy_namespaces+0x430/0x4a0 kernel/nsproxy.c:179
 copy_process+0x1700/0x3d70 kernel/fork.c:2509
 kernel_clone+0x21b/0x840 kernel/fork.c:2914
 __do_sys_clone kernel/fork.c:3057 [inline]
 __se_sys_clone kernel/fork.c:3041 [inline]
 __x64_sys_clone+0x18c/0x1e0 kernel/fork.c:3041
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f04c978f6c9
RSP: 002b:00007f04ca58bfe8 EFLAGS: 00000206 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f04c99e5fa0 RCX: 00007f04c978f6c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000040042600
RBP: 00007f04c9811f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000000
R13: 00007f04c99e6038 R14: 00007f04c99e5fa0 R15: 00007ffe4fa7dac8
 </TASK>
task:syz.1.1976      state:R  running task     stack:25832 pid:12029 ppid:5786   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6866
 preempt_schedule+0xab/0xc0 kernel/sched/core.c:6890
 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]
 zap_pte_range mm/memory.c:1522 [inline]
 zap_pmd_range mm/memory.c:1570 [inline]
 zap_pud_range mm/memory.c:1599 [inline]
 zap_p4d_range mm/memory.c:1620 [inline]
 unmap_page_range+0x236f/0x2fe0 mm/memory.c:1641
 unmap_vmas+0x25e/0x3a0 mm/memory.c:1731
 exit_mmap+0x200/0xb50 mm/mmap.c:3302
 __mmput+0x118/0x3c0 kernel/fork.c:1355
 exit_mm+0x1da/0x2c0 kernel/exit.c:569
 do_exit+0x88e/0x23c0 kernel/exit.c:870
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1024
 get_signal+0x12fc/0x1400 kernel/signal.c:2902
 arch_do_signal_or_restart+0x9c/0x7b0 arch/x86/kernel/signal.c:310
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xf6/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:302
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fd49718f6c9
RSP: 002b:00007fd49807e0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007fd4973e5fa8 RCX: 00007fd49718f6c9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fd4973e5fa8
RBP: 00007fd4973e5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd4973e6038 R14: 00007ffc9442cd10 R15: 00007ffc9442cdf8
 </TASK>
rcu: rcu_preempt kthread starved for 6012 jiffies! g60149 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:26920 pid:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5380 [inline]
 __schedule+0x14d2/0x44d0 kernel/sched/core.c:6699
 schedule+0xbd/0x170 kernel/sched/core.c:6773
 schedule_timeout+0x160/0x280 kernel/time/timer.c:2167
 rcu_gp_fqs_loop+0x302/0x1560 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x99/0x380 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: 0 PID: 12025 Comm: syz.3.1974 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:27 [inline]
RIP: 0010:static_key_false include/linux/jump_label.h:207 [inline]
RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:147 [inline]
RIP: 0010:wrmsr arch/x86/include/asm/msr.h:254 [inline]
RIP: 0010:native_apic_msr_write+0x39/0x50 arch/x86/include/asm/apic.h:196
Code: 74 2a 83 ff 30 74 25 eb 10 81 ff d0 00 00 00 74 1b 81 ff e0 00 00 00 74 13 c1 ef 04 81 c7 00 08 00 00 89 f9 89 f0 31 d2 0f 30 <66> 90 c3 f3 0f 1e fa 89 f6 31 d2 e9 e7 14 19 03 0f 1f 80 00 00 00
RSP: 0018:ffffc90010807cd8 EFLAGS: 00000246
RAX: 00000000000000f6 RBX: 0000000000000200 RCX: 000000000000083f
RDX: 0000000000000000 RSI: 00000000000000f6 RDI: 000000000000083f
RBP: 0000000000000000 R08: ffffc90010807c47 R09: 1ffff92002100f88
R10: dffffc0000000000 R11: fffff52002100f89 R12: ffff8880b8e35001
R13: dffffc0000000000 R14: ffff8880b8e35050 R15: 0000000000000020
FS:  00007fe7edc756c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fe7edc75000 CR3: 00000000214c4000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 __apic_send_IPI_self arch/x86/include/asm/apic.h:454 [inline]
 arch_irq_work_raise+0x68/0x70 arch/x86/kernel/irq_work.c:31
 irq_work_queue+0x99/0x140 kernel/irq_work.c:124
 bpf_send_signal_common+0x2b6/0x420 kernel/trace/bpf_trace.c:875
 ____bpf_send_signal kernel/trace/bpf_trace.c:884 [inline]
 bpf_send_signal+0x19/0x20 kernel/trace/bpf_trace.c:882
 bpf_prog_7ba5217f62dcd359+0x40/0x44
 bpf_dispatcher_nop_func include/linux/bpf.h:1224 [inline]
 __bpf_prog_run include/linux/filter.h:612 [inline]
 bpf_prog_run include/linux/filter.h:619 [inline]
 __bpf_trace_run kernel/trace/bpf_trace.c:2322 [inline]
 bpf_trace_run2+0x1d1/0x3c0 kernel/trace/bpf_trace.c:2361
 trace_sys_enter+0x69/0x80 include/trace/events/syscalls.h:18
 syscall_trace_enter+0xf0/0x150 kernel/entry/common.c:81
 do_syscall_64+0x28/0xb0 arch/x86/entry/common.c:77
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe7ecd2b779
Code: 64 c7 00 16 00 00 00 b8 ff ff ff ff c3 0f 1f 40 00 90 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 c7 c0 0f 00 00 00 0f 05 <0f> 1f 80 00 00 00 00 48 81 ec 48 01 00 00 49 89 d0 64 48 8b 04 25
RSP: 002b:00007fe7edc74b40 EFLAGS: 00000246 ORIG_RAX: 000000000000000f
RAX: ffffffffffffffda RBX: 00007fe7ecfe6098 RCX: 00007fe7ecd2b779
RDX: 00007fe7edc74b40 RSI: 00007fe7edc74c70 RDI: 0000000000000011
RBP: 00007fe7ecfe6090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe7ecfe6128 R14: 00007fffd09148f0 R15: 00007fffd09149d8
 </TASK>

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/05 01:53 linux-6.6.y 0a805b6ea8cd 686bf657 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clone
2025/11/04 02:43 linux-6.6.y 0a805b6ea8cd 686bf657 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clone
2025/10/22 20:08 linux-6.6.y f231f248323d c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clone
2025/10/03 21:35 linux-6.6.y f34f16e5c632 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clone
2025/08/30 05:56 linux-6.6.y cc1a1c5b404a 807a3b61 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clone
2025/08/26 05:29 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2025/08/26 04:07 linux-6.6.y bb9c90ab9c5a bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2025/08/12 09:36 linux-6.6.y 3a8ababb8b6a c06e8995 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
* Struck through repros no longer work on HEAD.