INFO: rcu detected stall in sys_unshare (9)

Status: upstream: reported C repro on 2023/11/11 00:17
Subsystems: kernfs
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+872bccd9a68c6ba47718@syzkaller.appspotmail.com
First crash: 1040d, last: 8d09h
Cause bisection: the issue happens on the oldest tested release (bisect log)
Crash: INFO: rcu detected stall in corrupted (log)
Repro: C syz .config
  
Fix bisection: fixed by (bisect log) :
commit 5f6bd380c7bdbe10f7b4e8ddcceed60ce0714c6d
Author: Peter Zijlstra <peterz@infradead.org>
Date: Mon May 27 12:06:55 2024 +0000

  sched/rt: Remove default bandwidth control

  
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
6c385aa6 assessment-security DenialOfService: ❌ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: rcu detected stall in sys_unshare (9) 2026/05/22 19:16 2026/05/22 19:16 2026/05/22 19:49 df8ac09c
▶ ▼ Discussions (15)
Title Replies (including bot) Last reply
[syzbot] Monthly kernfs report (Sep 2026) 0 (1) 2026/09/01 20:33
[syzbot] Monthly net report (Jul 2026) 0 (1) 2026/07/25 04:32
[syzbot] Monthly kernfs report (Jul 2026) 0 (1) 2026/07/01 12:32
[syzbot] Monthly mm report (May 2026) 0 (1) 2026/05/23 12:32
[syzbot] Monthly kernfs report (Feb 2026) 0 (1) 2026/02/26 12:58
[syzbot] Monthly kernfs report (Jan 2026) 0 (1) 2026/01/26 07:12
[syzbot] Monthly kernfs report (Dec 2025) 0 (1) 2025/12/26 07:48
[syzbot] Monthly kernfs report (Nov 2025) 0 (1) 2025/11/25 08:46
[syzbot] Monthly kernfs report (Sep 2025) 0 (1) 2025/09/23 13:33
[syzbot] Monthly kernfs report (Aug 2025) 0 (1) 2025/08/23 16:32
[syzbot] [bpf?] INFO: rcu detected stall in sys_unshare (9) 0 (2) 2025/03/11 15:56
[syzbot] Monthly bpf report (Feb 2025) 0 (1) 2025/02/20 19:03
[syzbot] Monthly bpf report (Mar 2024) 0 (1) 2024/03/11 10:18
[syzbot] Monthly bpf report (Jan 2024) 1 (2) 2024/01/10 00:28
[syzbot] Monthly bpf report (Dec 2023) 0 (1) 2023/12/08 13:16
▶ ▼ Similar bugs (12)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: rcu detected stall in sys_unshare (2) mm 1 1 2439d 2439d 0/29 closed as invalid on 2020/01/08 05:23
upstream INFO: rcu detected stall in sys_unshare (5) net 1 1 1702d 1702d 0/29 closed as invalid on 2022/02/08 10:10
linux-6.6 INFO: rcu detected stall in sys_unshare 1 1 421d 421d 0/2 auto-obsoleted due to no activity on 2025/10/26 06:21
upstream INFO: rcu detected stall in sys_unshare (3) net 1 1 1925d 1925d 0/29 auto-closed as invalid on 2021/09/03 04:28
linux-5.15 INFO: rcu detected stall in sys_unshare missing-backport origin:upstream 1 syz, C done 13 206d 845d 0/3 upstream: reported C repro on 2024/05/20 16:51
upstream INFO: rcu detected stall in sys_unshare (6) kernfs 1 1 1671d 1671d 0/29 auto-closed as invalid on 2022/05/15 15:21
upstream INFO: rcu detected stall in sys_unshare mm 1 3 2475d 2475d 0/29 closed as invalid on 2019/12/04 14:04
upstream INFO: rcu detected stall in sys_unshare (4) kernel 1 1 1834d 1834d 0/29 auto-closed as invalid on 2021/12/03 09:38
upstream INFO: rcu detected stall in sys_unshare (7) bpf net 1 12 1287d 1418d 0/29 auto-obsoleted due to no activity on 2023/06/03 15:22
linux-6.1 INFO: rcu detected stall in sys_unshare origin:upstream missing-backport 1 syz, C unreliable 5 736d 1013d 0/3 upstream: reported C repro on 2023/12/04 08:29
android-5-15 BUG: soft lockup in sys_unshare 1 1 860d 860d 0/2 auto-obsoleted due to no activity on 2024/08/03 08:28
upstream INFO: task hung in linkwatch_event (4) prio:low net 1 syz, C done 4355 now 777d 0/29 upstream: reported C repro on 2024/07/27 06:21
▶ ▼ Last patch testing requests (10)
Created Duration User Patch Repo Result
2025/02/23 06:07 37m retest repro upstream no crash log
2024/10/26 22:53 23m retest repro upstream no crash log
2024/10/21 09:49 3h35m retest repro upstream no crash log
2024/08/17 22:32 2h32m retest repro upstream report log
2024/08/17 22:32 17m retest repro upstream report log
2024/05/28 18:20 3h04m retest repro upstream report log
2024/05/28 17:31 19m retest repro upstream report log
2024/05/27 22:41 25m retest repro upstream report log
2024/03/18 11:00 1h07m retest repro upstream error
2024/03/18 11:00 7h44m retest repro upstream error
▶ ▼ Fix bisection attempts (6)
Created Duration User Patch Repo Result
2025/03/11 08:23 7h32m bisect fix upstream OK (1) job log
2024/09/02 22:19 1h38m bisect fix upstream OK (0) job log log
2024/08/03 20:07 2h09m bisect fix upstream OK (0) job log log
2024/06/07 03:02 2h10m bisect fix upstream OK (0) job log log
2024/01/07 02:12 1h35m bisect fix upstream OK (0) job log log
2023/12/07 20:41 3h39m bisect fix upstream OK (0) job log log

Sample crash report:
bridge0: received packet on veth0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P18472/1:b..l P17379/1:b..l P155/1:b..l P18955/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=166013, q=728 ncpus=2)
task:syz.5.4146      state:R  running task     stack:25288 pid:18955 tgid:18952 ppid:18772  task_flags:0x400140 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x17d4/0x5820 kernel/sched/core.c:7270
 preempt_schedule_irq+0x4b/0x90 kernel/sched/core.c:7592
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x14f/0x910 kernel/entry/common.c:167
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:lock_acquire+0x222/0x350 kernel/locking/lockdep.c:5890
Code: ff ff ff e8 c0 bd 3d 0a f7 44 24 08 00 02 00 00 0f 84 39 ff ff ff 65 48 8b 05 12 49 f0 11 48 3b 44 24 58 75 33 fb 48 83 c4 60 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d f7 53 da
RSP: 0018:ffffc900056eeca8 EFLAGS: 00000282
RAX: 46aeaead68f3c300 RBX: 0000000000000000 RCX: 0000000000000046
RDX: 000000007bf1f7e1 RSI: ffffffff8e6f4850 RDI: ffffffff8c6d5780
RBP: ffffffff8177810f R08: ffffffff8177810f R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8ed5a420 R12: 0000000000000002
R13: ffffffff8ed5a420 R14: 0000000000000000 R15: 0000000000000246
 rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 rcu_read_lock include/linux/rcupdate.h:849 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1216 [inline]
 unwind_next_frame+0xac/0x2550 arch/x86/kernel/unwind_orc.c:495
 __unwind_start+0x514/0x660 arch/x86/kernel/unwind_orc.c:787
 unwind_start arch/x86/include/asm/unwind.h:64 [inline]
 arch_stack_walk+0xe3/0x150 arch/x86/kernel/stacktrace.c:24
 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
 save_stack+0x122/0x230 mm/page_owner.c:183
 __reset_page_owner+0x71/0x1f0 mm/page_owner.c:338
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 __free_frozen_pages+0xc93/0xd90 mm/page_alloc.c:2962
 __slab_free+0x274/0x2c0 mm/slub.c:5815
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4683 [inline]
 slab_alloc_node mm/slub.c:4996 [inline]
 kmem_cache_alloc_noprof+0x2b9/0x600 mm/slub.c:5010
 __kernfs_new_node+0xe6/0x980 fs/kernfs/dir.c:665
 kernfs_new_node+0xea/0x140 fs/kernfs/dir.c:751
 __kernfs_create_file+0x4b/0x2e0 fs/kernfs/file.c:1050
 sysfs_add_file_mode_ns+0x237/0x300 fs/sysfs/file.c:316
 create_files fs/sysfs/group.c:82 [inline]
 internal_create_group+0x679/0x1180 fs/sysfs/group.c:189
 internal_create_groups fs/sysfs/group.c:229 [inline]
 sysfs_create_groups+0x59/0x120 fs/sysfs/group.c:255
 device_add_groups drivers/base/core.c:2911 [inline]
 device_add_attrs+0xde/0x600 drivers/base/core.c:2975
 device_add+0x488/0xb80 drivers/base/core.c:3715
 netdev_register_kobject+0x197/0x350 net/core/net-sysfs.c:2340
 register_netdevice+0x1433/0x1eb0 net/core/dev.c:11503
 __ip_tunnel_create+0x3e8/0x550 net/ipv4/ip_tunnel.c:268
 ip_tunnel_init_net+0x2e5/0x820 net/ipv4/ip_tunnel.c:1137
 vti_init_net+0x2f/0x100 net/ipv4/ip_vti.c:517
 ops_init+0x35d/0x5d0 net/core/net_namespace.c:137
 setup_net+0x118/0x350 net/core/net_namespace.c:450
 copy_net_ns+0x4f9/0x720 net/core/net_namespace.c:583
 create_new_namespaces+0x3f0/0x6b0 kernel/nsproxy.c:132
 unshare_nsproxy_namespaces+0x149/0x190 kernel/nsproxy.c:234
 ksys_unshare+0x5a7/0x950 kernel/fork.c:3292
 __do_sys_unshare kernel/fork.c:3356 [inline]
 __se_sys_unshare kernel/fork.c:3354 [inline]
 __x64_sys_unshare+0x38/0x50 kernel/fork.c:3354
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc23599e0d9
RSP: 002b:00007fc2367da028 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007fc235c25fa0 RCX: 00007fc23599e0d9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000068040200
RBP: 00007fc235a35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc235c26038 R14: 00007fc235c25fa0 R15: 00007fc235d4fa48
 </TASK>
task:kworker/u8:6    state:R  running task     stack:21544 pid:155   tgid:155   ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: events_unbound cfg80211_wiphy_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x17d4/0x5820 kernel/sched/core.c:7270
 preempt_schedule_irq+0x4b/0x90 kernel/sched/core.c:7592
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x14f/0x910 kernel/entry/common.c:167
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:deref_stack_reg arch/x86/kernel/unwind_orc.c:422 [inline]
RIP: 0010:unwind_next_frame+0xcbc/0x2550 arch/x86/kernel/unwind_orc.c:614
Code: c0 20 c8 3c 01 0f 85 76 0e 00 00 48 89 d7 e8 eb 23 00 00 48 89 c3 49 bc 00 00 00 00 00 fc ff df 48 8b 44 24 20 42 80 3c 20 00 <4d> 8d 7e 48 74 08 4c 89 ff e8 96 64 bf 00 49 89 1f 48 8b 44 24 38
RSP: 0018:ffffc90002eeea20 EFLAGS: 00000246
RAX: 1ffff920005ddd62 RBX: ffffffff8b2b4200 RCX: 1ffff920005ddd01
RDX: ffffc90002eeeef8 RSI: 0000000000000002 RDI: ffffc90002eeeef8
RBP: 1ffffffff223d7b8 R08: ffffc90002eeef00 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8ed5a420 R12: dffffc0000000000
R13: ffffc90002ef0000 R14: ffffc90002eeeac8 R15: ffffc90002ee8000
 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xa9/0x100 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:5414 [inline]
 __kmalloc_noprof+0x36b/0x720 mm/slub.c:5439
 _kmalloc_noprof include/linux/slab.h:995 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 cfg80211_inform_single_bss_data+0x990/0x1be0 net/wireless/scan.c:2382
 cfg80211_inform_bss_data+0x263/0x3cc0 net/wireless/scan.c:3266
 cfg80211_inform_bss_frame_data+0x3c7/0x840 net/wireless/scan.c:3358
 ieee80211_bss_info_update+0x791/0xa50 net/mac80211/scan.c:230
 ieee80211_rx_bss_info net/mac80211/ibss.c:1065 [inline]
 ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1546 [inline]
 ieee80211_ibss_rx_queued_mgmt+0x1ce3/0x2c40 net/mac80211/ibss.c:1573
 ieee80211_iface_process_skb net/mac80211/iface.c:1769 [inline]
 ieee80211_iface_work+0x78a/0x1010 net/mac80211/iface.c:1823
 cfg80211_wiphy_work+0x29e/0x420 net/wireless/core.c:541
 process_one_work kernel/workqueue.c:3387 [inline]
 process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
task:syz.1.3610      state:R  running task     stack:26920 pid:17379 tgid:17379 ppid:15023  task_flags:0x40044c flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x17d4/0x5820 kernel/sched/core.c:7270
 preempt_schedule_common+0x7f/0xd0 kernel/sched/core.c:7449
 preempt_schedule_thunk+0x16/0x40 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:201 [inline]
 _raw_spin_unlock+0x41/0x50 kernel/locking/spinlock.c:213
 spin_unlock include/linux/spinlock.h:401 [inline]
 zap_pte_range mm/memory.c:2033 [inline]
 zap_pmd_range mm/memory.c:2089 [inline]
 zap_pud_range mm/memory.c:2117 [inline]
 zap_p4d_range mm/memory.c:2138 [inline]
 __zap_vma_range+0x4082/0x4f20 mm/memory.c:2178
 unmap_vmas+0x390/0x550 mm/memory.c:2247
 exit_mmap+0x293/0x9f0 mm/mmap.c:1315
 __mmput+0x118/0x420 kernel/fork.c:1193
 exit_mm+0x221/0x2d0 kernel/exit.c:614
 do_exit+0x6cd/0x2360 kernel/exit.c:996
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1151
 get_signal+0x121b/0x12c0 kernel/signal.c:3039
 arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x10e/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4bfb75e90e
RSP: 002b:00007f4bfc6d3f58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e6
RAX: fffffffffffffdfc RBX: 00007f4bfc6d46c0 RCX: 00007f4bfb75e90e
RDX: 00007f4bfc6d3fb0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f4bfb835024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4bfba26128 R14: 00007f4bfba26090 R15: 00007f4bfbb4fa48
 </TASK>
task:syz.4.3985      state:R  running task     stack:24896 pid:18472 tgid:18471 ppid:16704  task_flags:0x40054c flags:0x00080001
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x17d4/0x5820 kernel/sched/core.c:7270
 preempt_schedule_irq+0x4b/0x90 kernel/sched/core.c:7592
 irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:539 [inline]
 irqentry_exit+0x14f/0x910 kernel/entry/common.c:167
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:lock_acquire+0x222/0x350 kernel/locking/lockdep.c:5890
Code: ff ff ff e8 c0 bd 3d 0a f7 44 24 08 00 02 00 00 0f 84 39 ff ff ff 65 48 8b 05 12 49 f0 11 48 3b 44 24 58 75 33 fb 48 83 c4 60 <5b> 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc cc 48 8d 3d f7 53 da
RSP: 0018:ffffc900054274c0 EFLAGS: 00000286
RAX: bd0075b2d07fae00 RBX: 0000000000000000 RCX: 0000000000000046
RDX: 000000005a44979c RSI: ffffffff8e6f4850 RDI: ffffffff8c6d5780
RBP: ffffffff8177810f R08: ffffffff8177810f R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8ed5a420 R12: 0000000000000002
R13: ffffffff8ed5a420 R14: 0000000000000000 R15: 0000000000000246
 rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 rcu_read_lock include/linux/rcupdate.h:849 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1216 [inline]
 unwind_next_frame+0xac/0x2550 arch/x86/kernel/unwind_orc.c:495
 arch_stack_walk+0x11b/0x150 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xa9/0x100 kernel/stacktrace.c:122
 save_stack+0x122/0x230 mm/page_owner.c:183
 __reset_page_owner+0x71/0x1f0 mm/page_owner.c:338
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1418 [inline]
 free_pages_prepare+0x9eb/0xaf0 mm/page_alloc.c:1463
 __free_contig_range_common+0x174/0x340 mm/page_alloc.c:7060
 __free_contig_range mm/page_alloc.c:7105 [inline]
 free_pages_bulk+0x48/0x120 mm/page_alloc.c:5322
 vm_area_free_pages mm/vmalloc.c:3462 [inline]
 vfree+0x226/0x4a0 mm/vmalloc.c:3511
 kcov_put kernel/kcov.c:451 [inline]
 kcov_close+0x28/0x50 kernel/kcov.c:556
 __fput+0x418/0xa50 fs/file_table.c:512
 task_work_run+0x1d9/0x270 kernel/task_work.c:233
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0x73a/0x2360 kernel/exit.c:1008
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1151
 get_signal+0x121b/0x12c0 kernel/signal.c:3039
 arch_do_signal_or_restart+0xbb/0x860 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x10e/0x770 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:336 [inline]
 do_syscall_64+0x328/0x520 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5309f9e0d9
RSP: 002b:00007f530aefc0e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f530a225fa8 RCX: 00007f5309f9e0d9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f530a225fa8
RBP: 00007f530a225fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f530a226038 R14: 00007f530a34f960 R15: 00007f530a34fa48
 </TASK>
rcu: rcu_preempt kthread starved for 5881 jiffies! g166013 f0x0 RCU_GP_WAIT_FQS(5) ->state=R ->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:27752 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5520 [inline]
 __schedule+0x17d4/0x5820 kernel/sched/core.c:7270
 __schedule_loop kernel/sched/core.c:7347 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7362
 schedule_timeout+0x152/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x30c/0x11f0 kernel/rcu/tree.c:2122
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2330
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
RIP: 0010:__sanitizer_cov_trace_const_cmp4+0x0/0xb0 kernel/kcov.c:309
Code: 74 0a 18 48 89 44 0a 20 c3 cc cc cc cc cc 66 66 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 <f3> 0f 1e fa 48 8b 04 24 65 48 8b 0d 98 ac cb 11 65 48 8b 15 98 ac
RSP: 0018:ffffc900000066f8 EFLAGS: 00000246
RAX: ffffffff89ae1979 RBX: 0000000000000000 RCX: ffffffff8ea8ef80
RDX: 8000000000000300 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 0000000000000001 R08: 0000000000000100 R09: 1ffffffff20f38e7
R10: dffffc0000000000 R11: fffffbfff20f38e8 R12: ffff88814bf35500
R13: ffffffff86b434c6 R14: 0000000000000300 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888124cf1000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000404030 CR3: 0000000035f0e000 CR4: 00000000003526f0
Call Trace:
 <IRQ>
 cpu_max_bits_warn include/linux/cpumask.h:139 [inline]
 cpumask_check include/linux/cpumask.h:146 [inline]
 cpumask_test_cpu include/linux/cpumask.h:650 [inline]
 cpu_online include/linux/cpumask.h:1232 [inline]
 trace_netif_rx_exit+0x2c/0x1f0 include/trace/events/net.h:321
 __netif_rx+0x87/0xd0 net/core/dev.c:5802
 veth_forward_skb drivers/net/veth.c:326 [inline]
 veth_xmit+0x5b5/0xe60 drivers/net/veth.c:380
 __netdev_start_xmit include/linux/netdevice.h:5429 [inline]
 netdev_start_xmit include/linux/netdevice.h:5438 [inline]
 xmit_one net/core/dev.c:3937 [inline]
 dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3953
 __dev_queue_xmit+0x14c0/0x3820 net/core/dev.c:4926
 dev_queue_xmit include/linux/netdevice.h:3461 [inline]
 br_dev_queue_push_xmit+0x370/0x4b0 net/bridge/br_forward.c:53
 NF_HOOK+0x64e/0x6e0 include/linux/netfilter.h:325
 br_nf_post_routing+0xa53/0xee0 net/bridge/br_netfilter_hooks.c:964
 nf_hook_entry_hookfn include/linux/netfilter.h:165 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:280 [inline]
 NF_HOOK+0x23e/0x3f0 include/linux/netfilter.h:323
 br_forward_finish+0xd3/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:1165 [inline]
 br_nf_forward_finish+0xa76/0xea0 net/bridge/br_netfilter_hooks.c:667
 NF_HOOK+0x64e/0x6e0 include/linux/netfilter.h:325
 br_nf_forward_ip+0x7eb/0xa30 net/bridge/br_netfilter_hooks.c:721
 nf_hook_entry_hookfn include/linux/netfilter.h:165 [inline]
 nf_hook_slow+0xc5/0x220 net/netfilter/core.c:619
 nf_hook include/linux/netfilter.h:280 [inline]
 NF_HOOK+0x23e/0x3f0 include/linux/netfilter.h:323
 __br_forward+0x397/0x540 net/bridge/br_forward.c:115
 deliver_clone net/bridge/br_forward.c:131 [inline]
 maybe_deliver net/bridge/br_forward.c:191 [inline]
 br_flood+0x3e6/0x8d0 net/bridge/br_forward.c:245
 br_handle_frame_finish+0x1119/0x1950 net/bridge/br_input.c:229
 br_nf_hook_thresh+0x3dd/0x4c0 net/bridge/br_netfilter_hooks.c:-1
 br_nf_pre_routing_finish_ipv6+0x90c/0xc40 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:325 [inline]
 br_nf_pre_routing_ipv6+0x382/0x6f0 net/bridge/br_netfilter_ipv6.c:183
 nf_hook_entry_hookfn include/linux/netfilter.h:165 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:291 [inline]
 br_handle_frame+0x127f/0x1510 net/bridge/br_input.c:442
 __netif_receive_skb_core+0x989/0x30c0 net/core/dev.c:6151
 __netif_receive_skb_one_core net/core/dev.c:6262 [inline]
 __netif_receive_skb net/core/dev.c:6377 [inline]
 process_backlog+0x727/0x18b0 net/core/dev.c:6728
 __napi_poll+0xaa/0x330 net/core/dev.c:7787
 napi_poll net/core/dev.c:7850 [inline]
 net_rx_action+0x61d/0xf50 net/core/dev.c:8007
 handle_softirqs+0x226/0x860 kernel/softirq.c:645
 __do_softirq kernel/softirq.c:679 [inline]
 invoke_softirq kernel/softirq.c:519 [inline]
 __irq_exit_rcu+0xcb/0x220 kernel/softirq.c:767
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:784
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1062 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1062
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:674
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: 9c 93 02 c3 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 93 10 29 00 fb f4 <e9> 4c 0b 03 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8ea07ca0 EFLAGS: 00000246
RAX: 00000000013b76a5 RBX: ffffffff819b2c50 RCX: 8000000000000001
RDX: 0000000000000001 RSI: ffffffff8e46df3e RDI: ffffffff8c6d5780
RBP: ffffffff8ea07d78 R08: ffff8880b8633a1b R09: 1ffff110170c6743
R10: dffffc0000000000 R11: ffffed10170c6744 R12: 0000000000000000
R13: 1ffffffff1d51df0 R14: 1ffffffff1d40f9c R15: dffffc0000000000
 arch_safe_halt arch/x86/kernel/process.c:767 [inline]
 default_idle+0x9/0x20 arch/x86/kernel/process.c:768
 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:199 [inline]
 do_idle+0x2e0/0x540 kernel/sched/idle.c:355
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:454
 rest_init+0x378/0x3a0 init/main.c:723
 start_kernel+0x392/0x3e0 init/main.c:1181
 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x157
 </TASK>
net_ratelimit: 12207 callbacks suppressed
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:18, vlan:0)
bridge0: received packet on veth1 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)

Crashes (180):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/25 08:36 upstream 66498c75b4f8 23caa175 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_unshare
2026/08/11 16:16 upstream d58772d8520c 557a89d3 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/08/02 01:16 upstream 2d2338c93da7 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/07/31 21:08 upstream 8ba098e6b6ff db462e94 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/07/29 17:35 upstream fc02acf6ac0c 4a865b71 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/07/26 11:33 upstream 3dab139d4795 4a865b71 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/07/25 02:15 upstream 48a5a7ab8d6a 4a865b71 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/07/17 02:51 upstream 37e2f878a7a6 8f30cfd7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/01 00:08 upstream dc59e4fea9d8 00e8b0fd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_unshare
2026/06/09 00:26 upstream 4549871118cf 656e94c6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_unshare
2026/06/08 17:40 upstream 4549871118cf 656e94c6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_unshare
2026/06/05 20:22 upstream ddd664bbff63 48b6c3fa .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_unshare
2026/05/29 11:55 upstream 8fde5d1d47f6 4624854e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_unshare
2026/05/20 02:06 upstream 27fa82620cba 0909d65f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_unshare
2026/05/18 10:22 upstream 5200f5f493f7 55156e84 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_unshare
2026/04/23 15:26 upstream 2e6803928193 629ff21a .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/04/21 22:33 upstream 4ee64205ffaa 0b6ab7ec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_unshare
2026/04/19 19:16 upstream faeab166167f 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/04/16 09:51 upstream 40286d6379aa df15c5f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/04/16 02:15 upstream 40286d6379aa df15c5f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/04/11 22:35 upstream e753c16cb3dd 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/04/06 21:39 upstream 591cd656a1bf 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_unshare
2026/04/05 04:50 upstream 3aae9383f42f 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/04/03 21:32 upstream d8a9a4b11a13 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/04/01 23:22 upstream 9147566d8016 0285fe54 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_unshare
2026/03/30 19:23 upstream 7aaa8047eafd 458630d8 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_unshare
2026/03/28 11:10 upstream 7df48e363130 ef441708 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/03/25 19:52 upstream bbeb83d3182a 4367a094 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2026/03/19 06:46 upstream 8a30aeb0d1b4 0199f9a1 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_unshare
2025/06/30 15:31 upstream d0b3b7b22dfa fc9d8ee5 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_unshare
2024/03/04 02:30 upstream 58c806d867bf 25905f5d .config console log report syz C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_unshare
2024/02/27 21:09 upstream 45ec2f5f6ed3 05e69c83 .config console log report syz C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_unshare
2023/11/07 00:07 upstream d2f51b3516da 78fae24e .config console log report syz C [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_unshare
2026/08/10 05:43 upstream b9b3e33b70b7 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in sys_unshare
2026/06/06 15:55 upstream c10130c234c8 cc095639 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in sys_unshare
2026/09/04 09:16 net adf50c47a47f 801f0966 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/08/28 01:39 net 81eb1867e059 e2fa417d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/30 12:13 net 54ad7ea45d63 2377cd3d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/30 03:34 net 3bd438a58e91 cb1587ea .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/18 06:11 net 56d96fededd6 72524a66 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/08 00:39 net 60444706aa17 88a4b44c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/05 09:28 net 660667cd4066 fcece630 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/06/19 11:24 net 5c121ee63568 d7ffd47b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/05/26 13:55 net f229426072fc a3e47276 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/05/22 16:05 net 68993ced0f61 e16cf9f3 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/05/21 23:18 net 0377bd2722c1 e195359d .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/05/09 22:23 net 496c0c4c53bb 29233ece .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/05/03 23:50 net bd3a4795d574 a0d91488 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/05/01 21:20 net 85da3965df5e 753c55b9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_unshare
2026/09/02 21:06 net-next c29b37ed7a4d 85995287 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/08/09 03:05 net-next 001b5d347d8b 5d63f80b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/08/01 19:24 net-next 69963a0678a3 e611ffe1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/22 21:22 net-next 24d0af194bcc 881ce5c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/13 05:29 net-next f6f3b36c15ed d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/07/10 13:39 net-next b470fde8f77b 99e64375 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/06/22 19:58 net-next b85966adbf5d 5a630be6 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/06/20 07:25 net-next b85966adbf5d 43bfcdb0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/06/07 03:21 net-next 903db046d557 cc095639 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/06/01 17:26 net-next c2c0486c5680 8d8eeb3a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/04/22 01:16 net-next 1f5ffc672165 0b6ab7ec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/03/30 02:16 net-next 02d0e59e36e0 356bdfc9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_unshare
2026/08/11 14:56 linux-next 3d08ff75a47a 37a258dd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_unshare
2026/04/16 22:29 linux-next 452c3b1ea875 321ae225 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_unshare
2025/10/02 15:36 linux-next 3b9b1f8df454 49379ee0 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-rust-kasan-gce INFO: rcu detected stall in sys_unshare
* Struck through repros no longer work on HEAD.