syzbot


INFO: rcu detected stall in sys_pipe2 (2)

Status: upstream: reported syz repro on 2024/11/10 15:52
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+693a483dd6ac06c62b09@syzkaller.appspotmail.com
First crash: 544d, last: 11d
Cause bisection: introduced by (bisect log) :
commit d15121be7485655129101f3960ae6add40204463
Author: Paolo Abeni <pabeni@redhat.com>
Date: Mon May 8 06:17:44 2023 +0000

  Revert "softirq: Let ksoftirqd do its job"

Crash: no output from test machine (log)
Repro: syz .config
  
Fix bisection: fixed by (bisect log) :
commit 66951e4860d3c688bfa550ea4a19635b57e00eca
Author: Peter Zijlstra <peterz@infradead.org>
Date: Mon Jan 13 12:50:11 2025 +0000

  sched/fair: Fix update_cfs_group() vs DELAY_DEQUEUE

  
Discussions (1)
Title Replies (including bot) Last reply
[syzbot] [mm?] INFO: rcu detected stall in sys_pipe2 (2) 0 (4) 2025/12/26 16:43
Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in sys_pipe2 1 3 63d 103d 0/2 upstream: reported on 2025/12/05 08:23
upstream INFO: rcu detected stall in sys_pipe2 fs 1 1 1611d 1611d 0/29 auto-closed as invalid on 2022/01/17 19:05
Last patch testing requests (4)
Created Duration User Patch Repo Result
2025/11/21 02:36 23m retest repro net-next report log
2025/09/06 23:10 19m retest repro net-next report log
2025/05/05 15:17 23m retest repro net-next report log
2025/02/04 13:24 19m retest repro net-next 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): P12520/1:b..l P20445/1:b..l P7855/1:b..l P10998/1:b..l P5805/1:b..l
rcu: 	(detected by 1, t=10502 jiffies, g=105537, q=1002 ncpus=2)
task:syz-executor    state:R  running task     stack:21600 pid:5805  tgid:5805  ppid:5804   task_flags:0x400100 flags:0x00080800
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0x15dd/0x52d0 kernel/sched/core.c:6908
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7235
 irqentry_exit+0x599/0x620 kernel/entry/common.c:239
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x20b/0x2e0 kernel/locking/lockdep.c:5872
Code: e9 30 ff ff ff e8 65 4d 0c 0a f7 c3 00 02 00 00 0f 84 38 ff ff ff 65 48 8b 05 e1 6a 7a 11 48 3b 44 24 30 75 33 fb 48 83 c4 38 <5b> 41 5c 41 5d 41 5e 41 5f 5d e9 46 33 0f 0a cc 48 8d 3d 6e 76 73
RSP: 0018:ffffc900039f76b8 EFLAGS: 00000286
RAX: c6262eb43d942800 RBX: 0000000000000246 RCX: 0000000000000046
RDX: 00000000a1697acb RSI: ffffffff8e1654fc RDI: ffffffff8c27b280
RBP: 0000000000000000 R08: ffffffff81767a45 R09: ffffffff8e7602e0
R10: ffffc900039f7818 R11: ffffffff81b0bb70 R12: 0000000000000002
R13: ffffffff8e7602e0 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 rcu_read_lock include/linux/rcupdate.h:850 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1193 [inline]
 unwind_next_frame+0xc2/0x23c0 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:165
 __reset_page_owner+0x71/0x1f0 mm/page_owner.c:320
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
 __slab_free+0x263/0x2b0 mm/slub.c:5576
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 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:4542 [inline]
 slab_alloc_node mm/slub.c:4869 [inline]
 kmem_cache_alloc_noprof+0x2bc/0x650 mm/slub.c:4876
 lsm_inode_alloc security/security.c:228 [inline]
 security_inode_alloc+0x39/0x310 security/security.c:1189
 inode_init_always_gfp+0x9ed/0xdc0 fs/inode.c:307
 inode_init_always include/linux/fs.h:2922 [inline]
 alloc_inode+0x82/0x1b0 fs/inode.c:354
 new_inode_pseudo include/linux/fs.h:3003 [inline]
 get_pipe_inode fs/pipe.c:888 [inline]
 create_pipe_files+0x51/0x7e0 fs/pipe.c:928
 __do_pipe_flags+0x46/0x1f0 fs/pipe.c:990
 do_pipe2+0xaa/0x190 fs/pipe.c:1038
 __do_sys_pipe2 fs/pipe.c:1056 [inline]
 __se_sys_pipe2 fs/pipe.c:1054 [inline]
 __x64_sys_pipe2+0x5a/0x70 fs/pipe.c:1054
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb6b579b7c9
RSP: 002b:00007fffe00abc28 EFLAGS: 00000246 ORIG_RAX: 0000000000000125
RAX: ffffffffffffffda RBX: 0000555557679f80 RCX: 00007fb6b579b7c9
RDX: 0000000000000006 RSI: 0000000000000000 RDI: 00007fffe00abc48
RBP: 00007fffe00ac200 R08: 0000000000000830 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fffe00ac040
R13: 00005555576789d0 R14: 000055555767ea10 R15: 00007fffe00abd80
 </TASK>
task:syz-executor    state:R  running task     stack:22432 pid:10998 tgid:10998 ppid:10988  task_flags:0x400140 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0x15dd/0x52d0 kernel/sched/core.c:6908
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7235
 irqentry_exit+0x599/0x620 kernel/entry/common.c:239
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:lock_acquire+0x20b/0x2e0 kernel/locking/lockdep.c:5872
Code: e9 30 ff ff ff e8 65 4d 0c 0a f7 c3 00 02 00 00 0f 84 38 ff ff ff 65 48 8b 05 e1 6a 7a 11 48 3b 44 24 30 75 33 fb 48 83 c4 38 <5b> 41 5c 41 5d 41 5e 41 5f 5d e9 46 33 0f 0a cc 48 8d 3d 6e 76 73
RSP: 0018:ffffc9000c20f898 EFLAGS: 00000282
RAX: 4e95aa821a770b00 RBX: 0000000000000246 RCX: 0000000000000046
RDX: 00000000a1697acb RSI: ffffffff8e1654fc RDI: ffffffff8c27b280
RBP: 0000000000000000 R08: ffffffff81767a45 R09: ffffffff8e7602e0
R10: ffffc9000c20f9f8 R11: ffffffff81b0bb70 R12: 0000000000000002
R13: ffffffff8e7602e0 R14: 0000000000000000 R15: 0000000000000000
 rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 rcu_read_lock include/linux/rcupdate.h:850 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1193 [inline]
 unwind_next_frame+0xc2/0x23c0 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:165
 __reset_page_owner+0x71/0x1f0 mm/page_owner.c:320
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
 __slab_free+0x263/0x2b0 mm/slub.c:5576
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 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:4542 [inline]
 slab_alloc_node mm/slub.c:4869 [inline]
 kmem_cache_alloc_noprof+0x2bc/0x650 mm/slub.c:4876
 alloc_filename fs/namei.c:142 [inline]
 do_getname+0x2e/0x250 fs/namei.c:182
 getname_flags fs/namei.c:225 [inline]
 getname include/linux/fs.h:2512 [inline]
 class_filename_constructor include/linux/fs.h:2539 [inline]
 __do_sys_unlink fs/namei.c:5574 [inline]
 __se_sys_unlink+0x1e/0x140 fs/namei.c:5572
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f86c6d9b887
RSP: 002b:00007f86c713ecb8 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f86c6d9b887
RDX: 00007f86c713ece0 RSI: 00007f86c713ed70 RDI: 00007f86c713ed70
RBP: 00007f86c713ed70 R08: 00007f86c713fd70 R09: 00000000ffffffff
R10: 0000000000000100 R11: 0000000000000206 R12: 00007f86c713fe00
R13: 00007f86c6e31f90 R14: 00000000000bc6b8 R15: 00007f86c713fe40
 </TASK>
task:syz.0.508       state:R  running task     stack:26912 pid:7855  tgid:7855  ppid:5836   task_flags:0x40044c flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0x15dd/0x52d0 kernel/sched/core.c:6908
 preempt_schedule_common+0x82/0xd0 kernel/sched/core.c:7092
 preempt_schedule_thunk+0x16/0x30 arch/x86/entry/thunk.S:12
 __raw_spin_unlock include/linux/spinlock_api_smp.h:169 [inline]
 _raw_spin_unlock+0x3f/0x50 kernel/locking/spinlock.c:186
 spin_unlock include/linux/spinlock.h:389 [inline]
 zap_pte_range mm/memory.c:1959 [inline]
 zap_pmd_range mm/memory.c:2021 [inline]
 zap_pud_range mm/memory.c:2049 [inline]
 zap_p4d_range mm/memory.c:2070 [inline]
 unmap_page_range+0x3b71/0x48f0 mm/memory.c:2091
 unmap_single_vma mm/memory.c:2133 [inline]
 unmap_vmas+0x48f/0x6a0 mm/memory.c:2171
 exit_mmap+0x280/0xa10 mm/mmap.c:1302
 __mmput+0x118/0x430 kernel/fork.c:1174
 exit_mm+0x168/0x220 kernel/exit.c:581
 do_exit+0x6a2/0x23c0 kernel/exit.c:964
 do_group_exit+0x21b/0x2d0 kernel/exit.c:1118
 get_signal+0x1284/0x1330 kernel/signal.c:3034
 arch_do_signal_or_restart+0xbc/0x830 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
 exit_to_user_mode_loop+0x86/0x480 kernel/entry/common.c:98
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x32d/0xf80 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f437e75cfce
RSP: 002b:00007f437f6c2f58 EFLAGS: 00000246 ORIG_RAX: 00000000000000e6
RAX: fffffffffffffdfc RBX: 00007f437f6c36c0 RCX: 00007f437e75cfce
RDX: 00007f437f6c2fb0 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f437e832bd9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f437ea16038 R14: 00007f437ea15fa0 R15: 00007f437eb3fa48
 </TASK>
task:kworker/1:4     state:R  running task     stack:22080 pid:20445 tgid:20445 ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: usb_hub_wq hub_event
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0x15dd/0x52d0 kernel/sched/core.c:6908
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7235
 irqentry_exit+0x599/0x620 kernel/entry/common.c:239
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:__orc_find arch/x86/kernel/unwind_orc.c:110 [inline]
RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:238 [inline]
RIP: 0010:unwind_next_frame+0x2b4/0x23c0 arch/x86/kernel/unwind_orc.c:510
Code: 00 00 fc ff df 0f 84 1c 04 00 00 4a 8d 14 ad 64 f2 23 90 45 29 e8 4a 8d 1c 82 48 83 c3 fc 49 89 d5 48 39 da 0f 86 21 02 00 00 <49> 29 d5 49 c1 fd 02 4a 8d 04 6d 00 00 00 00 4c 01 e8 48 8d 14 46
RSP: 0018:ffffc9000dc9ed58 EFLAGS: 00000202
RAX: ffffffff905c9f40 RBX: ffffffff905c9f44 RCX: ffffffff905c9f48
RDX: ffffffff905c9f44 RSI: ffffffff90f206b8 RDI: ffffffff8c27b220
RBP: ffffffff905c9f48 R08: 0000000000000001 R09: ffffffff8e7602e0
R10: ffffc9000dc9ee78 R11: ffffffff81b0bb70 R12: ffffffff85fed1e8
R13: ffffffff905c9f44 R14: ffffc9000dc9ee28 R15: ffffffff905c9f44
 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:165
 __reset_page_owner+0x71/0x1f0 mm/page_owner.c:320
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
 __slab_free+0x263/0x2b0 mm/slub.c:5576
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 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:4542 [inline]
 slab_alloc_node mm/slub.c:4869 [inline]
 __kmalloc_cache_noprof+0x2ba/0x660 mm/slub.c:5378
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 call_usermodehelper_setup+0x8e/0x270 kernel/umh.c:362
 kobject_uevent_env+0x658/0x9e0 lib/kobject_uevent.c:628
 really_probe+0x789/0xaf0 drivers/base/dd.c:711
 __driver_probe_device+0x18c/0x320 drivers/base/dd.c:803
 driver_probe_device+0x4f/0x240 drivers/base/dd.c:833
 __device_attach_driver+0x2d4/0x4c0 drivers/base/dd.c:961
 bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:500
 __device_attach+0x2c5/0x450 drivers/base/dd.c:1033
 device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1088
 bus_probe_device+0x12a/0x220 drivers/base/bus.c:574
 device_add+0x7b6/0xb70 drivers/base/core.c:3689
 usb_new_device+0xa08/0x16f0 drivers/usb/core/hub.c:2695
 hub_port_connect drivers/usb/core/hub.c:5567 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x2a1c/0x4f30 drivers/usb/core/hub.c:5953
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0xb02/0x1830 kernel/workqueue.c:3358
 worker_thread+0xa50/0xfc0 kernel/workqueue.c:3439
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
task:kworker/u8:14   state:R  running task     stack:26968 pid:12520 tgid:12520 ppid:2      task_flags:0x4208060 flags:0x00080000
Workqueue: krds_cp_wq#1/0 rds_connect_worker
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0x15dd/0x52d0 kernel/sched/core.c:6908
 preempt_schedule_irq+0x4d/0xa0 kernel/sched/core.c:7235
 irqentry_exit+0x599/0x620 kernel/entry/common.c:239
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:on_stack arch/x86/include/asm/stacktrace.h:58 [inline]
RIP: 0010:stack_access_ok arch/x86/kernel/unwind_orc.c:409 [inline]
RIP: 0010:deref_stack_reg+0x96/0x230 arch/x86/kernel/unwind_orc.c:419
Code: 89 f7 e8 3d 3c b9 00 4c 8b 04 24 48 be 00 00 00 00 00 fc ff df 4c 89 74 24 08 4d 8b 77 10 4c 89 fd 48 c1 ed 03 0f b6 44 35 00 <84> c0 0f 85 3c 01 00 00 41 83 3f 00 0f 95 c0 4c 39 c3 0f 96 c1 20
RSP: 0018:ffffc900041270e0 EFLAGS: 00000a06
RAX: 0000000000000000 RBX: ffffc90004120000 RCX: 0000000000000000
RDX: ffffc90004127248 RSI: dffffc0000000000 RDI: ffffc90004127208
RBP: 1ffff92000824e41 R08: ffffc90004127480 R09: 0000000000000000
R10: ffffc90004127258 R11: fffff52000824e4d R12: 1ffff92000824e42
R13: 1ffff92000824e43 R14: ffffc90004128000 R15: ffffc90004127208
 unwind_next_frame+0x18c6/0x23c0 arch/x86/kernel/unwind_orc.c:-1
 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:165
 __reset_page_owner+0x71/0x1f0 mm/page_owner.c:320
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1433 [inline]
 __free_frozen_pages+0xc2b/0xdb0 mm/page_alloc.c:2978
 __slab_free+0x263/0x2b0 mm/slub.c:5576
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
 __kasan_kmalloc+0x22/0xb0 mm/kasan/common.c:406
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x31c/0x660 mm/slub.c:5383
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 ref_tracker_alloc+0x15a/0x4c0 lib/ref_tracker.c:270
 __netns_tracker_alloc include/net/net_namespace.h:367 [inline]
 sk_alloc+0x2c3/0x390 net/core/sock.c:2322
 inet_create+0x7a0/0x1000 net/ipv4/af_inet.c:328
 __sock_create+0x4b2/0x9d0 net/socket.c:1605
 rds_tcp_conn_path_connect+0x2d7/0x930 net/rds/tcp_connect.c:-1
 rds_connect_worker+0x1d8/0x290 net/rds/threads.c:176
 process_one_work kernel/workqueue.c:3275 [inline]
 process_scheduled_works+0xb02/0x1830 kernel/workqueue.c:3358
 worker_thread+0xa50/0xfc0 kernel/workqueue.c:3439
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
rcu: rcu_preempt kthread starved for 10543 jiffies! g105537 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:27656 pid:16    tgid:16    ppid:2      task_flags:0x208040 flags:0x00080000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5295 [inline]
 __schedule+0x15dd/0x52d0 kernel/sched/core.c:6908
 __schedule_loop kernel/sched/core.c:6990 [inline]
 schedule+0x164/0x360 kernel/sched/core.c:7005
 schedule_timeout+0x158/0x2c0 kernel/time/sleep_timeout.c:99
 rcu_gp_fqs_loop+0x312/0x11d0 kernel/rcu/tree.c:2095
 rcu_gp_kthread+0x9e/0x2b0 kernel/rcu/tree.c:2297
 kthread+0x388/0x470 kernel/kthread.c:436
 ret_from_fork+0x51e/0xb90 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:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
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 02/12/2026
RIP: 0010:separate_irq_context kernel/locking/lockdep.c:4703 [inline]
RIP: 0010:__lock_acquire+0x73c/0x2cf0 kernel/locking/lockdep.c:5221
Code: 84 8e 00 00 00 41 83 ff 31 0f 83 ca 23 00 00 4b 8d 04 bf 4d 89 ec 41 8b 6d 20 48 8b 4c 24 20 8b 44 c1 f8 31 e8 25 00 60 00 00 <0f> 95 c1 89 0c 24 31 c9 f7 d8 48 19 c9 48 09 cb 48 83 bc 24 20 01
RSP: 0018:ffffc90000007358 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0ac0d5affe09d4ff RCX: ffffffff8e495a18
RDX: 0000000000000008 RSI: ffffffff8e495a40 RDI: ffffffff8e494ec0
RBP: 0000000000022007 R08: ffffffff81767a45 R09: ffffffff8e7602e0
R10: ffffc90000007638 R11: ffffffff81b0bb70 R12: ffffffff8e495a40
R13: ffffffff8e495a40 R14: ffffffff8e494ec0 R15: 0000000000000001
FS:  0000000000000000(0000) GS:ffff888125461000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb6b37255c2 CR3: 000000004641a000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 000000000000000c DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
 rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
 rcu_read_lock include/linux/rcupdate.h:850 [inline]
 class_rcu_constructor include/linux/rcupdate.h:1193 [inline]
 unwind_next_frame+0xc2/0x23c0 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
 kasan_save_stack mm/kasan/common.c:57 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2692 [inline]
 slab_free mm/slub.c:6168 [inline]
 kmem_cache_free+0x187/0x630 mm/slub.c:6298
 kfree_skb_reason include/linux/skbuff.h:1322 [inline]
 kfree_skb include/linux/skbuff.h:1331 [inline]
 ip6_mc_input+0x8de/0xbd0 net/ipv6/ip6_input.c:593
 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318
 __netif_receive_skb_one_core net/core/dev.c:6164 [inline]
 __netif_receive_skb net/core/dev.c:6277 [inline]
 process_backlog+0x7dd/0x1950 net/core/dev.c:6628
 __napi_poll+0xae/0x340 net/core/dev.c:7692
 napi_poll net/core/dev.c:7755 [inline]
 net_rx_action+0x627/0xf70 net/core/dev.c:7912
 handle_softirqs+0x22a/0x870 kernel/softirq.c:622
 __do_softirq kernel/softirq.c:656 [inline]
 invoke_softirq kernel/softirq.c:496 [inline]
 __irq_exit_rcu+0x5f/0x150 kernel/softirq.c:723
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:739
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1056
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:63
Code: 0e 6d 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 c3 90 1b 00 fb f4 <e9> fc e9 02 00 cc cc cc cc cc cc cc cc cc cc cc cc 90 90 90 90 90
RSP: 0018:ffffffff8e407dc0 EFLAGS: 00000246
RAX: 0000000001bc84bb RBX: ffffffff819a88ed RCX: 0000000080000001
RDX: 0000000000000001 RSI: ffffffff8def4811 RDI: ffffffff8c27b280
RBP: ffffffff8e407eb0 R08: ffff8880b863395b R09: 1ffff110170c672b
R10: dffffc0000000000 R11: ffffed10170c672c R12: ffffffff9011a8b0
R13: 1ffffffff1c929d8 R14: 0000000000000000 R15: 0000000000000000
 arch_safe_halt arch/x86/kernel/process.c:766 [inline]
 default_idle+0x9/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x72/0xb0 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0x1bd/0x500 kernel/sched/idle.c:332
 cpu_startup_entry+0x43/0x60 kernel/sched/idle.c:430
 rest_init+0x2de/0x300 init/main.c:760
 start_kernel+0x385/0x3d0 init/main.c:1210
 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>
net_ratelimit: 7868 callbacks suppressed
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ba:f4:09:ff:10:4e, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:1b, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ba:f4:09:ff:10:4e, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:ba:f4:09:ff:10:4e, vlan:0)
bridge0: received packet on bridge_slave_0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)

Crashes (113):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/03/07 14:37 upstream 651690480a96 5cb44a80 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2026/02/15 16:17 upstream ca4ee40bf13d 1e62d198 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2026/01/22 11:30 upstream a66191c590b3 a16aed1d .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_pipe2
2025/11/24 23:25 upstream ac3fd01e4c1e bf6fe8fe .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2025/11/22 21:08 upstream 2eba5e05d9bc 4fb8ef37 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/11/06 21:56 upstream c2c2ccfd4ba7 4e1406b4 .config console log report info [disk image] [vmlinux] [kernel image] ci-qemu-gce-upstream-auto INFO: rcu detected stall in sys_pipe2
2025/11/05 05:44 upstream c9cfc122f037 a6c9c731 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2025/10/23 11:08 upstream 250a17e8f955 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_pipe2
2025/09/27 12:24 upstream fec734e8d564 001c9061 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-root INFO: rcu detected stall in sys_pipe2
2025/09/24 07:14 upstream cec1e6e5d1ab 0abd0691 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2025/09/16 10:02 upstream 46a51f4f5eda e2beed91 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2025/08/17 23:28 upstream 8d561baae505 1804e95e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2025/08/07 07:35 upstream cca7a0aae895 4bd24a3e .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/08/04 11:59 upstream 038d61fd6422 7368264b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_pipe2
2025/07/10 07:35 upstream 8c2e52ebbe88 956bd956 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/06/20 02:31 upstream 24770983ccfe ed3e87f7 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/04/21 13:08 upstream 9d7a0577c9db 2a20f901 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/04/19 19:37 upstream 8560697b23dc 2a20f901 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_pipe2
2025/04/09 05:45 upstream bec7dcbc242c b133e63a .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/04/05 03:53 upstream e48e99b6edf4 1c4febdb .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2025/03/27 13:17 upstream 1e1ba8d23dae 20510e88 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_pipe2
2025/03/21 00:25 upstream 5fc319360819 62330552 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2025/03/03 00:42 upstream b91872c56940 c3901742 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/02/28 22:48 upstream 76544811c850 1e7a43e1 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_pipe2
2025/02/18 15:01 upstream 2408a807bfc3 c37c7249 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_pipe2
2025/02/13 04:02 upstream 4dc1d1bec898 b27c2402 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/02/07 06:00 upstream bb066fe812d6 53657d1b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/16 04:11 upstream 619f0b6fad52 968edaf4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/13 11:46 upstream 5bc55a333a2f 6dbc6a9b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_pipe2
2025/01/10 01:33 upstream eea6e4b4dfb8 40f46913 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/07 14:54 upstream fbfd64d25c7a f3558dbf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/06 09:44 upstream ab75170520d4 f3558dbf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2024/12/29 09:17 upstream 059dd502b263 d3ccff63 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_pipe2
2024/12/21 20:55 upstream e84a3bf7f4aa d7f584ee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2024/11/07 19:11 upstream ff7afaeca1a1 c069283c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-smack-root INFO: rcu detected stall in sys_pipe2
2024/11/06 08:01 upstream 2e1b3cc9d7f7 3a465482 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce INFO: rcu detected stall in sys_pipe2
2024/11/01 06:54 upstream 6c52d4da1c74 96eb609f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: rcu detected stall in sys_pipe2
2025/08/20 18:19 upstream b19a97d57c15 bd178e57 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in sys_pipe2
2025/06/12 16:12 upstream 2c4a1f3fe03e 98683f8f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-386 INFO: rcu detected stall in sys_pipe2
2025/01/21 09:44 net d640627663bf 6e87cfa2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/20 23:38 net 4395a44acb15 6e87cfa2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/20 02:51 net bc50835e83f6 f2cb035c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/15 17:18 net 001ba0902046 7315a7cf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/13 03:47 net 47e55e4b410f 6dbc6a9b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_pipe2
2024/12/28 02:29 net a024e377efed d3ccff63 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_pipe2
2024/12/27 06:45 net b3a69c559899 d3ccff63 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-this-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/05/16 08:37 net-next 1119e5519dcd cfde8269 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/07 17:00 net-next 912d6f669725 f3558dbf .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/01/02 07:35 net-next 9268abe611b0 d3ccff63 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_pipe2
2024/12/28 12:24 net-next 9268abe611b0 d3ccff63 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_pipe2
2024/12/25 00:21 net-next 9268abe611b0 444551c4 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_pipe2
2024/12/22 00:48 net-next ae418e95dd93 d7f584ee .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_pipe2
2024/12/19 22:11 net-next 6b3099ebca13 1d58202c .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-net-kasan-gce INFO: rcu detected stall in sys_pipe2
2025/08/23 02:18 linux-next 7fa4d8dc380f bf27483f .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_pipe2
2025/07/22 15:05 linux-next d086c886ceb9 1555463b .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_pipe2
2024/12/23 12:01 linux-next 8155b4ef3466 444551c4 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-linux-next-kasan-gce-root INFO: rcu detected stall in sys_pipe2
* Struck through repros no longer work on HEAD.