syzbot
INFO: rcu detected stall in br_handle_frame
Status:
upstream: reported on 2025/11/21 04:49
Reported-by: syzbot+a0b26fcabafa4609b88c@syzkaller.appspotmail.com
First crash: 264d, last: 34d
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): P6034/1:b..l
rcu: (detected by 1, t=10502 jiffies, g=11937, q=938 ncpus=2)
task:syz.0.58 state:R running task stack:27088 pid:6034 ppid:5781 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x15ae/0x4660 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
__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]
copy_pte_range mm/memory.c:1107 [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+0x2be5/0x3700 mm/memory.c:1323
dup_mmap kernel/fork.c:769 [inline]
dup_mm kernel/fork.c:1694 [inline]
copy_mm+0x1751/0x1e30 kernel/fork.c:1743
copy_process+0x171d/0x3df0 kernel/fork.c:2508
kernel_clone+0x24b/0x8a0 kernel/fork.c:2917
__do_sys_clone kernel/fork.c:3060 [inline]
__se_sys_clone kernel/fork.c:3044 [inline]
__x64_sys_clone+0x1b7/0x230 kernel/fork.c:3044
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fdcc5f9de59
RSP: 002b:00007fdcc6e80fd8 EFLAGS: 00000202 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007fdcc6226180 RCX: 00007fdcc5f9de59
RDX: 0000200000000640 RSI: 0000200000000610 RDI: 0000000000040080
RBP: 00007fdcc6033e6f R08: 00002000000006c0 R09: 00002000000006c0
R10: 0000200000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007fdcc6226218 R14: 00007fdcc6226180 R15: 00007ffd12d8eb98
</TASK>
rcu: rcu_preempt kthread starved for 808 jiffies! g11937 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:27096 pid:17 ppid:2 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5381 [inline]
__schedule+0x15ae/0x4660 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+0x30d/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:
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 6019 Comm: syz.1.55 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:__sanitizer_cov_trace_pc+0x4/0x60 kernel/kcov.c:212
Code: 1f 80 00 00 00 00 f3 0f 1e fa 53 48 89 fb e8 13 00 00 00 48 8b 3d ec 87 05 0d 48 89 de 5b e9 23 a7 57 00 cc cc cc f3 0f 1e fa <48> 8b 04 24 65 48 8b 0d c0 d2 7c 7e 65 8b 15 c1 d2 7c 7e 81 e2 00
RSP: 0018:ffffc90000005d28 EFLAGS: 00000006
RAX: ffffffff81014c7c RBX: ffffc900000063e8 RCX: ffff88802ab69e00
RDX: 0000000000010100 RSI: 0000000000000000 RDI: ffffc900000063e8
RBP: ffffc90000005e90 R08: dffffc0000000000 R09: 1ffffffff223cea0
R10: dffffc0000000000 R11: fffffbfff223cea1 R12: ffffc90000005dc0
R13: 0000000000000000 R14: 0000000000000000 R15: dffffc0000000000
FS: 00007feb144486c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2df0dff8 CR3: 000000002f6cc000 CR4: 00000000003506f0
Call Trace:
<IRQ>
kvm_guest_state+0xf/0xf0 virt/kvm/kvm_main.c:6013
perf_guest_state include/linux/perf_event.h:1520 [inline]
perf_misc_flags+0x21/0xd0 arch/x86/events/core.c:3016
perf_prepare_header kernel/events/core.c:7937 [inline]
__perf_event_output kernel/events/core.c:7967 [inline]
perf_event_output_forward+0x20b/0x3e0 kernel/events/core.c:7987
__perf_event_overflow+0x461/0x660 kernel/events/core.c:9712
perf_event_overflow kernel/events/core.c:9733 [inline]
perf_swevent_hrtimer+0x437/0x610 kernel/events/core.c:11222
__run_hrtimer kernel/time/hrtimer.c:1754 [inline]
__hrtimer_run_queues+0x4e8/0xc10 kernel/time/hrtimer.c:1818
hrtimer_interrupt+0x39d/0x980 kernel/time/hrtimer.c:1880
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1077 [inline]
__sysvec_apic_timer_interrupt+0xfb/0x3b0 arch/x86/kernel/apic/apic.c:1094
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1088 [inline]
sysvec_apic_timer_interrupt+0x51/0xc0 arch/x86/kernel/apic/apic.c:1088
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:687
RIP: 0010:unwind_next_frame+0xc7/0x2990 arch/x86/kernel/unwind_orc.c:482
Code: 00 00 85 ed 74 76 4c 89 74 24 60 48 89 5c 24 18 bf 01 00 00 00 e8 49 43 21 00 49 8d 6d 50 48 89 e8 48 c1 e8 03 48 89 44 24 58 <42> 80 3c 38 00 74 08 48 89 ef e8 aa 38 a4 00 4c 8b 75 00 4d 85 f6
RSP: 0018:ffffc90000006498 EFLAGS: 00000a06
RAX: 1ffff92000000cc3 RBX: 1ffff92000000cb9 RCX: ffffffff972ee403
RDX: ffff88802ab69e00 RSI: 0000000000000002 RDI: 0000000000000001
RBP: ffffc90000006618 R08: ffffc90000006600 R09: 0000000000000000
R10: ffffc900000065c8 R11: fffff52000000cc5 R12: ffffc90000006568
R13: ffffc900000065c8 R14: ffffc90000006600 R15: dffffc0000000000
__unwind_start+0x5bb/0x730 arch/x86/kernel/unwind_orc.c:760
unwind_start arch/x86/include/asm/unwind.h:64 [inline]
arch_stack_walk+0xf8/0x190 arch/x86/kernel/stacktrace.c:24
stack_trace_save+0xaa/0x100 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:46 [inline]
kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
kasan_slab_free include/linux/kasan.h:164 [inline]
slab_free_hook mm/slub.c:1811 [inline]
slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
slab_free mm/slub.c:3830 [inline]
kmem_cache_free+0xf8/0x290 mm/slub.c:3852
skb_ext_del include/linux/skbuff.h:4830 [inline]
nf_bridge_info_free net/bridge/br_netfilter_hooks.c:152 [inline]
br_nf_dev_queue_xmit+0x53b/0x1d60 net/bridge/br_netfilter_hooks.c:870
NF_HOOK+0x66e/0x700 include/linux/netfilter.h:304
br_nf_post_routing+0xa3b/0xec0 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+0xa69/0xe90 net/bridge/br_netfilter_hooks.c:684
NF_HOOK+0x66e/0x700 include/linux/netfilter.h:304
br_nf_forward_ip+0xc78/0x10d0 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
br_handle_frame_finish+0xf2d/0x15c0 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+0x9e5/0xd20 net/bridge/br_netfilter_ipv6.c:-1
NF_HOOK include/linux/netfilter.h:304 [inline]
br_nf_pre_routing_ipv6+0x34d/0x6a0 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+0x1240/0x14d0 net/bridge/br_input.c:424
__netif_receive_skb_core+0xf94/0x3ab0 net/core/dev.c:5540
__netif_receive_skb_one_core net/core/dev.c:5644 [inline]
__netif_receive_skb+0x74/0x290 net/core/dev.c:5760
process_backlog+0x380/0x710 net/core/dev.c:6088
__napi_poll+0xbb/0x460 net/core/dev.c:6650
napi_poll net/core/dev.c:6717 [inline]
net_rx_action+0x65f/0xcc0 net/core/dev.c:6853
handle_softirqs+0x27d/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:release_task_stack kernel/fork.c:588 [inline]
RIP: 0010:put_task_stack+0x5d/0x200 kernel/fork.c:598
Code: e8 17 00 00 bf 01 00 00 00 89 ee e8 3d 29 37 00 83 fd 01 0f 85 fd 00 00 00 49 bc 00 00 00 00 00 fc ff df 4c 8d 73 18 4c 89 f0 <48> c1 e8 03 42 0f b6 04 20 84 c0 0f 85 66 01 00 00 41 8b 2e bf 80
RSP: 0018:ffffc900032878e8 EFLAGS: 00010246
RAX: ffff88802bcc0018 RBX: ffff88802bcc0000 RCX: 0000000000000002
RDX: ffff88802ab69e00 RSI: 0000000000000001 RDI: 0000000000000001
RBP: 0000000000000001 R08: ffff88802bcc17eb R09: 1ffff110057982fd
R10: dffffc0000000000 R11: ffffed10057982fe R12: dffffc0000000000
R13: 1ffff110171c79a9 R14: ffff88802bcc0018 R15: ffffffff8ca88f60
finish_task_switch+0x440/0x8f0 kernel/sched/core.c:5288
context_switch kernel/sched/core.c:5384 [inline]
__schedule+0x15b6/0x4660 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
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
_raw_spin_unlock_irqrestore+0x111/0x120 kernel/locking/spinlock.c:194
__do_sys_perf_event_open kernel/events/core.c:12950 [inline]
__se_sys_perf_event_open+0x1849/0x1c60 kernel/events/core.c:12601
do_syscall_x64 arch/x86/entry/common.c:46 [inline]
do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7feb1359de59
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:00007feb14448028 EFLAGS: 00000246 ORIG_RAX: 000000000000012a
RAX: ffffffffffffffda RBX: 00007feb13825fa0 RCX: 00007feb1359de59
RDX: ffffffffffffffff RSI: 0000000000000000 RDI: 0000200000000480
RBP: 00007feb13633e6f R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
R13: 00007feb13826038 R14: 00007feb13825fa0 R15: 00007fffdc22e9e8
</TASK>
net_ratelimit: 8331 callbacks suppressed
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:be:12:a4:dc:87:6f, 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 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 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:be:12:a4:dc:87:6f, 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:be:12:a4:dc:87:6f, vlan:0)
net_ratelimit: 12037 callbacks suppressed
bridge0: received packet on veth0_to_bridge with own address as source address (addr:be:12:a4:dc:87:6f, 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:be:12:a4:dc:87:6f, 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:be:12:a4:dc:87:6f, 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 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 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:1b, vlan:0)
* Struck through repros no longer work on HEAD.