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: 4d09h, last: 1d09h
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 38d 123d 2/2 fixed on 2025/12/06 23:11
linux-5.15 INFO: rcu detected stall in sys_clone 1 1 738d 738d 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 885d 957d 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 2111d 2227d 0/29 auto-closed as invalid on 2020/06/01 05:26
upstream INFO: rcu detected stall in sys_clone (4) kernel 1 1 1628d 1628d 0/29 auto-closed as invalid on 2021/09/27 17:49
upstream INFO: rcu detected stall in sys_clone (3) mm 1 2 1963d 1986d 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 1298d 1298d 0/29 auto-closed as invalid on 2022/08/23 03:28
upstream INFO: rcu detected stall in sys_clone kernel 1 1 2284d 2284d 13/29 fixed on 2019/10/09 10:54
upstream INFO: rcu detected stall in sys_clone (8) mm 1 C error 337 10h33m 624d 0/29 upstream: reported C repro on 2024/03/29 00:16
linux-4.19 INFO: rcu detected stall in sys_clone 1 2 2182d 2201d 0/1 auto-closed as invalid on 2020/04/21 05:46
upstream INFO: rcu detected stall in sys_clone (5) kernfs 1 5 1432d 1532d 0/29 closed as invalid on 2022/02/08 10:00
upstream INFO: rcu detected stall in sys_clone (7) fs 1 1 1034d 1034d 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 56 10h12m 626d 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 39 12d 633d 0/3 upstream: reported C repro on 2024/03/20 15:17
android-5-10 BUG: soft lockup in sys_clone 1 1 523d 523d 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 97d 97d 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 459d 602d 0/2 auto-obsoleted due to no activity on 2024/12/19 12:14

Sample crash report:
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 	Tasks blocked on level-0 rcu_node (CPUs 0-1): P8237/1:b..l
rcu: 	(detected by 1, t=10503 jiffies, g=26957, q=265 ncpus=2)
task:syz.2.680       state:R  running task     stack:25800 pid:8237  ppid:5766   flags:0x00004002
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:1523 [inline]
 zap_pmd_range mm/memory.c:1571 [inline]
 zap_pud_range mm/memory.c:1600 [inline]
 zap_p4d_range mm/memory.c:1621 [inline]
 unmap_page_range+0x236f/0x2fe0 mm/memory.c:1642
 unmap_vmas+0x25e/0x3a0 mm/memory.c:1732
 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: 0033:0x7f248d58f749
RSP: 002b:00007f248b7f60e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f248d7e5fa8 RCX: 00007f248d58f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f248d7e5fa8
RBP: 00007f248d7e5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f248d7e6038 R14: 00007ffd15249840 R15: 00007ffd15249928
 </TASK>
rcu: rcu_preempt kthread starved for 1071 jiffies! g26957 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x0 ->cpu=1
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:26568 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:2168
 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: 1 PID: 8234 Comm: syz.0.679 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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:ffffc900001efa40 EFLAGS: 00000206
RAX: 0000000000000001 RBX: 0000000000000000 RCX: 837be190e7696e00
RDX: 0000000000000000 RSI: ffffffff8aaace60 RDI: ffffffff8afc6f80
RBP: ffffc900001efb48 R08: dffffc0000000000 R09: 1ffffffff21b28a0
R10: dffffc0000000000 R11: fffffbfff21b28a1 R12: 1ffff9200003df54
R13: ffffffff8cd2ff20 R14: 0000000000000246 R15: dffffc0000000000
FS:  00007f17736236c0(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3c8d3b5698 CR3: 000000002cc54000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000200000000300 DR2: 0000200000000300
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <IRQ>
 rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 rcu_read_lock include/linux/rcupdate.h:786 [inline]
 net_generic+0x3a/0x240 include/net/netns/generic.h:45
 is_pppoe_ip net/bridge/br_netfilter_hooks.c:121 [inline]
 br_nf_post_routing+0x4de/0xfb0 net/bridge/br_netfilter_hooks.c:958
 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+0x213/0x3d0 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:-1 [inline]
 br_nf_forward_finish+0xa33/0xe50 net/bridge/br_netfilter_hooks.c:684
 NF_HOOK+0x613/0x6a0 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+0x213/0x3d0 include/linux/netfilter.h:302
 __br_forward+0x41f/0x600 net/bridge/br_forward.c:115
 br_handle_frame_finish+0x143d/0x1950 net/bridge/br_input.c:215
 br_nf_hook_thresh+0x3b6/0x480 net/bridge/br_netfilter_hooks.c:1184
 br_nf_pre_routing_finish_ipv6+0x9e3/0xd90 net/bridge/br_netfilter_ipv6.c:-1
 NF_HOOK include/linux/netfilter.h:304 [inline]
 br_nf_pre_routing_ipv6+0x34d/0x680 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+0x957/0x14c0 net/bridge/br_input.c:424
 __netif_receive_skb_core+0xf6b/0x3ac0 net/core/dev.c:5502
 __netif_receive_skb_one_core net/core/dev.c:5606 [inline]
 __netif_receive_skb+0x74/0x290 net/core/dev.c:5722
 process_backlog+0x380/0x6e0 net/core/dev.c:6050
 __napi_poll+0xc0/0x460 net/core/dev.c:6612
 napi_poll net/core/dev.c:6679 [inline]
 net_rx_action+0x5ea/0xbf0 net/core/dev.c:6815
 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+0xc7/0x190 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:task_dead_fair+0x0/0x1a0 kernel/sched/fair.c:8287
Code: e1 07 80 c1 03 38 c1 0f 8c 6a ff ff ff 48 8b 7c 24 08 e8 13 1b 7d 00 e9 5b ff ff ff 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <f3> 0f 1e fa 55 41 57 41 56 41 55 41 54 53 50 48 89 fb 48 bd 00 00
RSP: 0018:ffffc9000479f490 EFLAGS: 00010286
RAX: ffffffff815fe390 RBX: ffff88802c9e1e00 RCX: ffffffff815c504a
RDX: 0000000000000001 RSI: 0000000000000004 RDI: ffff88802c9e1e00
RBP: ffffc9000479f4f0 R08: ffff88807da31303 R09: 1ffff1100fb46260
R10: dffffc0000000000 R11: ffffed100fb46261 R12: ffff88802bb78540
R13: dffffc0000000000 R14: ffffffff8c7c1b60 R15: ffff88807da31300
 finish_task_switch+0x43a/0x920 kernel/sched/core.c:5284
 context_switch kernel/sched/core.c:5383 [inline]
 __schedule+0x14da/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
 __up_write kernel/locking/rwsem.c:1377 [inline]
 up_write+0x1ec/0x410 kernel/locking/rwsem.c:1626
 mmap_write_unlock include/linux/mmap_lock.h:133 [inline]
 dup_mmap kernel/fork.c:781 [inline]
 dup_mm kernel/fork.c:1692 [inline]
 copy_mm+0x1723/0x1ca0 kernel/fork.c:1741
 copy_process+0x16d3/0x3d70 kernel/fork.c:2506
 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: 0033:0x7f177278f749
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1773622fe8 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007f17729e5fa0 RCX: 00007f177278f749
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007f1772813f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f17729e6038 R14: 00007f17729e5fa0 R15: 00007ffc0a5c09d8
 </TASK>
net_ratelimit: 69 callbacks suppressed
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
net_ratelimit: 3821 callbacks suppressed
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:0c, vlan:0)
bridge0: received packet on team0 with own address as source address (addr:aa:aa:aa:aa:aa:20, vlan:0)

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
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.