syzbot


INFO: rcu detected stall in sys_clone (2)

Status: upstream: reported on 2025/12/09 09:13
Reported-by: syzbot+7919861b650883ef99d9@syzkaller.appspotmail.com
First crash: 51d, last: 5d01h
Similar bugs (17)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.6 INFO: rcu detected stall in sys_clone 1 C done 8 86d 170d 2/2 fixed on 2025/12/06 23:11
linux-5.15 INFO: rcu detected stall in sys_clone 1 1 785d 785d 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 932d 1004d 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 2159d 2275d 0/29 auto-closed as invalid on 2020/06/01 05:26
upstream INFO: rcu detected stall in sys_clone (4) kernel 1 1 1675d 1675d 0/29 auto-closed as invalid on 2021/09/27 17:49
upstream INFO: rcu detected stall in sys_clone (3) mm 1 2 2011d 2033d 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 1346d 1346d 0/29 auto-closed as invalid on 2022/08/23 03:28
upstream INFO: rcu detected stall in sys_clone kernel 1 1 2332d 2332d 13/29 fixed on 2019/10/09 10:54
upstream INFO: rcu detected stall in sys_clone (8) mm 1 C error 373 10d 672d 0/29 upstream: reported C repro on 2024/03/29 00:16
linux-4.19 INFO: rcu detected stall in sys_clone 1 2 2230d 2248d 0/1 auto-closed as invalid on 2020/04/21 05:46
upstream INFO: rcu detected stall in sys_clone (5) kernfs 1 5 1480d 1579d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in sys_clone (7) fs 1 1 1081d 1081d 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 C done 76 4d14h 674d 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 C error 41 8d17h 680d 0/3 upstream: reported C repro on 2024/03/20 15:17
android-5-10 BUG: soft lockup in sys_clone 1 1 570d 570d 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 145d 145d 0/2 auto-obsoleted due to no activity on 2025/12/06 02:03
android-5-15 BUG: soft lockup in sys_clone origin:upstream 1 C error 18 506d 650d 0/2 auto-obsoleted due to no activity on 2024/12/19 12:14

Sample crash report:
bridge0: received packet on veth0_to_bridge 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): P5766/1:b..l
rcu: 	(detected by 0, t=10503 jiffies, g=11081, q=1032 ncpus=2)
task:syz-executor    state:R  running task     stack:21704 pid:5766  ppid:1      flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 preempt_schedule_common+0x82/0xc0 kernel/sched/core.c:6867
 preempt_schedule+0xc0/0xd0 kernel/sched/core.c:6891
 preempt_schedule_thunk+0x1a/0x30 arch/x86/entry/thunk_64.S:45
 unwind_next_frame+0x200f/0x2970 arch/x86/kernel/unwind_orc.c:672
 arch_stack_walk+0x144/0x190 arch/x86/kernel/stacktrace.c:25
 stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
 save_stack+0x125/0x230 mm/page_owner.c:128
 __reset_page_owner+0x4e/0x190 mm/page_owner.c:149
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 __slab_free+0x35a/0x400 mm/slub.c:3736
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4b0 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+0x11a/0x2d0 mm/slub.c:3519
 ptlock_alloc+0x20/0x70 mm/memory.c:6177
 ptlock_init include/linux/mm.h:2964 [inline]
 pagetable_pte_ctor include/linux/mm.h:2987 [inline]
 __pte_alloc_one include/asm-generic/pgalloc.h:71 [inline]
 pte_alloc_one+0xcc/0x530 arch/x86/mm/pgtable.c:33
 __pte_alloc+0x22/0x2a0 mm/memory.c:438
 copy_pte_range mm/memory.c:1029 [inline]
 copy_pmd_range mm/memory.c:1168 [inline]
 copy_pud_range mm/memory.c:1205 [inline]
 copy_p4d_range mm/memory.c:1229 [inline]
 copy_page_range+0x2d96/0x3670 mm/memory.c:1323
 dup_mmap kernel/fork.c:764 [inline]
 dup_mm kernel/fork.c:1692 [inline]
 copy_mm+0x11cb/0x1d50 kernel/fork.c:1741
 copy_process+0x16f7/0x3d80 kernel/fork.c:2506
 kernel_clone+0x24b/0x8a0 kernel/fork.c:2914
 __do_sys_clone kernel/fork.c:3057 [inline]
 __se_sys_clone kernel/fork.c:3041 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:3041
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f4ab75c3752
RSP: 002b:00007ffd718ea0f0 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffd718ea0f0 RCX: 00007f4ab75c3752
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffd718ea27c R08: 0000000000000000 R09: 0000000000000001
R10: 000055558786b7d0 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 0000000000017aaa R15: 00007ffd718ea2d0
 </TASK>
rcu: rcu_preempt kthread starved for 575 jiffies! g11081 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:17    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5381 [inline]
 __schedule+0x1553/0x45a0 kernel/sched/core.c:6700
 schedule+0xbd/0x170 kernel/sched/core.c:6774
 schedule_timeout+0x188/0x2d0 kernel/time/timer.c:2168
 rcu_gp_fqs_loop+0x313/0x1590 kernel/rcu/tree.c:1667
 rcu_gp_kthread+0x9d/0x3b0 kernel/rcu/tree.c:1866
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
rcu: Stack dump where RCU GP kthread last ran:
CPU: 0 PID: 6067 Comm: syz.3.81 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:lock_is_held_type+0x13e/0x190 kernel/locking/lockdep.c:5830
Code: 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 75 46 41 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 08 75 3c 89 e8 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f
RSP: 0018:ffffc90000006898 EFLAGS: 00000206
RAX: b1cff16a0febc000 RBX: ffff8880238bbc00 RCX: b1cff16a0febc000
RDX: 0000000000000100 RSI: ffffffff8acada80 RDI: ffffffff8b1c80e0
RBP: 0000000000000001 R08: ffffffff911be52f R09: 1ffffffff2237ca5
R10: dffffc0000000000 R11: fffffbfff2237ca6 R12: 0000000000000004
R13: 0000000000000246 R14: ffffffff8d131fe0 R15: ffff8880238bc780
FS:  00007f6b3c82f6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fc5a6b0fe80 CR3: 00000000744a8000 CR4: 00000000003506f0
Call Trace:
 <IRQ>
 skb_dst include/linux/skbuff.h:1119 [inline]
 br_drop_fake_rtable include/linux/netfilter_bridge.h:21 [inline]
 br_dev_queue_push_xmit+0x106/0x870 net/bridge/br_forward.c:39
 NF_HOOK+0x66e/0x700 include/linux/netfilter.h:304
 br_nf_post_routing+0xb41/0xfb0 net/bridge/br_netfilter_hooks.c:977
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:259 [inline]
 NF_HOOK+0x23e/0x3e0 include/linux/netfilter.h:302
 br_forward_finish+0xd3/0x130 net/bridge/br_forward.c:66
 br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:1184 [inline]
 br_nf_forward_finish+0xa51/0xe80 net/bridge/br_netfilter_hooks.c:684
 NF_HOOK+0x66e/0x700 include/linux/netfilter.h:304
 br_nf_forward_ip+0xcc1/0x1110 net/bridge/br_netfilter_hooks.c:754
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_slow+0xbd/0x200 net/netfilter/core.c:626
 nf_hook include/linux/netfilter.h:259 [inline]
 NF_HOOK+0x23e/0x3e0 include/linux/netfilter.h:302
 __br_forward+0x433/0x610 net/bridge/br_forward.c:115
 deliver_clone net/bridge/br_forward.c:131 [inline]
 maybe_deliver+0xb5/0x150 net/bridge/br_forward.c:191
 br_flood+0x31b/0x670 net/bridge/br_forward.c:237
 br_handle_frame_finish+0x149b/0x19b0 net/bridge/br_input.c:215
 br_nf_hook_thresh+0x3cd/0x4a0 net/bridge/br_netfilter_hooks.c:1184
 br_nf_pre_routing_finish_ipv6+0x9dc/0xd00 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:304 [inline]
 br_nf_pre_routing_ipv6+0x349/0x6b0 net/bridge/br_netfilter_ipv6.c:184
 nf_hook_entry_hookfn include/linux/netfilter.h:144 [inline]
 nf_hook_bridge_pre net/bridge/br_input.c:277 [inline]
 br_handle_frame+0x96b/0x14e0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xfab/0x3af0 net/core/dev.c:5532
 __netif_receive_skb_one_core net/core/dev.c:5636 [inline]
 __netif_receive_skb+0x74/0x290 net/core/dev.c:5752
 process_backlog+0x396/0x700 net/core/dev.c:6080
 __napi_poll+0xc0/0x460 net/core/dev.c:6642
 napi_poll net/core/dev.c:6709 [inline]
 net_rx_action+0x616/0xc50 net/core/dev.c:6846
 handle_softirqs+0x280/0x820 kernel/softirq.c:578
 __do_softirq kernel/softirq.c:612 [inline]
 invoke_softirq kernel/softirq.c:452 [inline]
 __irq_exit_rcu+0xd3/0x190 kernel/softirq.c:661
 irq_exit_rcu+0x9/0x20 kernel/softirq.c:673
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
 sysvec_apic_timer_interrupt+0xa4/0xc0 arch/x86/kernel/apic/apic.c:1088
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:slab_update_freelist mm/slub.c:617 [inline]
RIP: 0010:__slab_free+0x22f/0x400 mm/slub.c:3682
Code: 75 33 48 89 f7 4c 89 d6 4c 89 ea 48 89 d9 4d 89 f8 e8 b5 df ff ff 41 89 c7 eb 55 4c 89 f9 4c 89 d0 4c 89 ea f0 48 0f c7 4e 20 <0f> 84 86 00 00 00 e9 9f fe ff ff 48 89 6c 24 08 48 89 f5 4c 89 64
RSP: 0018:ffffc9000bbe7250 EFLAGS: 00000242
RAX: ffff88802e4bda50 RBX: ffff88802e4bd2d0 RCX: 0000000000220008
RDX: 0000000000220009 RSI: ffffea0000b92f40 RDI: 0000000000000000
RBP: ffff888019e4d280 R08: 0000000000000001 R09: 0000000000000000
R10: ffff88802e4bda50 R11: fffffbfff2237ca6 R12: ffff888019e4d280
R13: 0000000000220009 R14: 0000000000220008 R15: 0000000000220008
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4b0 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+0x11a/0x2d0 mm/slub.c:3519
 ptlock_alloc+0x20/0x70 mm/memory.c:6177
 ptlock_init include/linux/mm.h:2964 [inline]
 pagetable_pte_ctor include/linux/mm.h:2987 [inline]
 __pte_alloc_one include/asm-generic/pgalloc.h:71 [inline]
 pte_alloc_one+0xcc/0x530 arch/x86/mm/pgtable.c:33
 __pte_alloc+0x22/0x2a0 mm/memory.c:438
 copy_pte_range mm/memory.c:1029 [inline]
 copy_pmd_range mm/memory.c:1168 [inline]
 copy_pud_range mm/memory.c:1205 [inline]
 copy_p4d_range mm/memory.c:1229 [inline]
 copy_page_range+0x2d96/0x3670 mm/memory.c:1323
 dup_mmap kernel/fork.c:764 [inline]
 dup_mm kernel/fork.c:1692 [inline]
 copy_mm+0x11cb/0x1d50 kernel/fork.c:1741
 copy_process+0x16f7/0x3d80 kernel/fork.c:2506
 kernel_clone+0x24b/0x8a0 kernel/fork.c:2914
 __do_sys_clone kernel/fork.c:3057 [inline]
 __se_sys_clone kernel/fork.c:3041 [inline]
 __x64_sys_clone+0x1b7/0x230 kernel/fork.c:3041
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f6b3b99acb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f6b3c82efd8 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f6b3bc15fa0 RCX: 00007f6b3b99acb9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f6b3ba08bf7 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6b3bc16038 R14: 00007f6b3bc15fa0 R15: 00007ffd53b994f8
 </TASK>
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 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:06:7d:9a:1c:f0:98, 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:06:7d:9a:1c:f0:98, vlan:0)
bridge0: received packet on veth0_to_bridge with own address as source address (addr:06:7d:9a:1c:f0:98, 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 (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/25 06:11 linux-6.6.y cbb31f77b879 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2026/01/25 00:50 linux-6.6.y cbb31f77b879 40acda8a .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2026/01/19 18:52 linux-6.6.y cbb31f77b879 a9fc5226 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2025/12/31 06:17 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: rcu detected stall in sys_clone
2025/12/12 09:20 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan-perf INFO: rcu detected stall in sys_clone
2025/12/09 09:12 linux-6.6.y 5fa4793a2d2d d6526ea3 .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.