[syzbot] [bridge?] INFO: rcu detected stall in br_handle_frame (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f83a4f2a4d8c Merge tag 'erofs-for-6.17-rc6-fixes' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17d98762580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4d8792ecb6308d0f
dashboard link: https://syzkaller.appspot.com/bug?extid=f8850bc3986562f79619
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=102d3b62580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=174fb934580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/446b6da00381/disk-f83a4f2a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/acc2d4e8a1cc/vmlinux-f83a4f2a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cec01f1ca35a/bzImage-f83a4f2a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f8850b...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-...!: (2 ticks this GP) idle=e7fc/1/0x4000000000000000 softirq=18961/18961 fqs=0
rcu: (detected by 1, t=10502 jiffies, g=12417, q=367 ncpus=2)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 807 Comm: kworker/u8:5 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: ipv6_addrconf addrconf_dad_work
RIP: 0010:taprio_set_budgets+0x12b/0x3b0 net/sched/sch_taprio.c:671
Code: e8 48 c1 e8 03 48 89 44 24 10 31 db 45 31 e4 4c 89 6c 24 18 bf 10 00 00 00 4c 89 e6 e8 8e 70 24 f8 49 83 fc 0f 48 89 6c 24 30 <0f> 87 8a 01 00 00 4d 8d 2c 2f 4c 89 e8 48 c1 e8 03 48 b9 00 00 00
RSP: 0018:ffffc90000006060 EFLAGS: 00000093
RAX: ffffffff899b5352 RBX: 0000000000000000 RCX: ffff88802481bc00
RDX: 0000000000010100 RSI: 0000000000000000 RDI: 0000000000000010
RBP: 0000000000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000000c08 R12: 0000000000000000
R13: ffff8880313e32e0 R14: ffff8880743df930 R15: ffff8880743dfc00
FS: 0000000000000000(0000) GS:ffff888125c15000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055556d266808 CR3: 000000007e704000 CR4: 00000000003526f0
Call Trace:
<IRQ>
advance_sched+0x963/0xc90 net/sched/sch_taprio.c:982
__run_hrtimer kernel/time/hrtimer.c:1761 [inline]
__hrtimer_run_queues+0x52c/0xc60 kernel/time/hrtimer.c:1825
hrtimer_interrupt+0x45b/0xaa0 kernel/time/hrtimer.c:1887
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1039 [inline]
__sysvec_apic_timer_interrupt+0x108/0x410 arch/x86/kernel/apic/apic.c:1056
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
sysvec_apic_timer_interrupt+0x52/0xc0 arch/x86/kernel/apic/apic.c:1050
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:stack_trace_consume_entry+0x5/0x280 kernel/stacktrace.c:83
Code: f0 5b 41 5e 5d c3 cc cc cc cc cc e8 05 fc cd 09 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 55 <41> 57 41 56 41 55 41 54 53 48 83 ec 18 48 ba 00 00 00 00 00 fc ff
RSP: 0018:ffffc90000006518 EFLAGS: 00000286
RAX: ffffffff8184f87d RBX: ffffc900000065e0 RCX: 7a67f0fb8b1bf500
RDX: 0000000000000001 RSI: ffffffff8184f87d RDI: ffffc900000065e0
RBP: ffffc900000065b0 R08: ffffc90003387170 R09: 0000000000000000
R10: ffffc90000006578 R11: ffffffff81ac4b00 R12: ffff88802481bc00
R13: 0000000000000000 R14: ffffffff81ac4b00 R15: ffffc90000006528
arch_stack_walk+0x10d/0x150 arch/x86/kernel/stacktrace.c:27
stack_trace_save+0x9c/0xe0 kernel/stacktrace.c:122
kasan_save_stack mm/kasan/common.c:47 [inline]
kasan_save_track+0x3e/0x80 mm/kasan/common.c:68
kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:243 [inline]
__kasan_slab_free+0x5b/0x80 mm/kasan/common.c:275
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2422 [inline]
slab_free mm/slub.c:4695 [inline]
kmem_cache_free+0x18f/0x400 mm/slub.c:4797
skb_ext_del include/linux/skbuff.h:4929 [inline]
nf_bridge_info_free net/bridge/br_netfilter_hooks.c:156 [inline]
br_nf_dev_queue_xmit+0x4ee/0x24a0 net/bridge/br_netfilter_hooks.c:851
NF_HOOK+0x618/0x6b0 include/linux/netfilter.h:318
br_nf_post_routing+0xb66/0xfe0 net/bridge/br_netfilter_hooks.c:966
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
nf_hook include/linux/netfilter.h:273 [inline]
NF_HOOK+0x215/0x3c0 include/linux/netfilter.h:316
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+0xa40/0xe60 net/bridge/br_netfilter_hooks.c:662
NF_HOOK+0x618/0x6b0 include/linux/netfilter.h:318
br_nf_forward_ip+0x647/0x7e0 net/bridge/br_netfilter_hooks.c:716
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_slow+0xc5/0x220 net/netfilter/core.c:623
nf_hook include/linux/netfilter.h:273 [inline]
NF_HOOK+0x215/0x3c0 include/linux/netfilter.h:316
__br_forward+0x41e/0x600 net/bridge/br_forward.c:115
br_handle_frame_finish+0x14b4/0x19b0 net/bridge/br_input.c:221
br_nf_hook_thresh+0x3c3/0x4a0 net/bridge/br_netfilter_hooks.c:-1
br_nf_pre_routing_finish_ipv6+0x948/0xd00 net/bridge/br_netfilter_ipv6.c:-1
NF_HOOK include/linux/netfilter.h:318 [inline]
br_nf_pre_routing_ipv6+0x37e/0x6b0 net/bridge/br_netfilter_ipv6.c:184
nf_hook_entry_hookfn include/linux/netfilter.h:158 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:283 [inline]
br_handle_frame+0x982/0x14c0 net/bridge/br_input.c:434
__netif_receive_skb_core+0x10b6/0x4020 net/core/dev.c:5878
__netif_receive_skb_one_core net/core/dev.c:5989 [inline]
__netif_receive_skb+0x72/0x380 net/core/dev.c:6104
process_backlog+0x60e/0x14f0 net/core/dev.c:6456
__napi_poll+0xc7/0x360 net/core/dev.c:7506
napi_poll net/core/dev.c:7569 [inline]
net_rx_action+0x707/0xe30 net/core/dev.c:7696
handle_softirqs+0x283/0x870 kernel/softirq.c:579
do_softirq+0xec/0x180 kernel/softirq.c:480
</IRQ>
<TASK>
__local_bh_enable_ip+0x17d/0x1c0 kernel/softirq.c:407
local_bh_enable include/linux/bottom_half.h:33 [inline]
rcu_read_unlock_bh include/linux/rcupdate.h:910 [inline]
__dev_queue_xmit+0x1d79/0x3b50 net/core/dev.c:4752
neigh_output include/net/neighbour.h:547 [inline]
ip6_finish_output2+0x11fb/0x16a0 net/ipv6/ip6_output.c:141
NF_HOOK include/linux/netfilter.h:318 [inline]
ndisc_send_skb+0xb54/0x1440 net/ipv6/ndisc.c:512
ndisc_send_ns+0xcb/0x150 net/ipv6/ndisc.c:670
addrconf_dad_work+0xaae/0x14b0 net/ipv6/addrconf.c:4282
process_one_work kernel/workqueue.c:3236 [inline]
process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3319
worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
kthread+0x70e/0x8a0 kernel/kthread.c:463
ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
rcu: rcu_preempt kthread timer wakeup didn't happen for 10501 jiffies! g12417 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402
rcu: Possible timer handling issue on cpu=0 timer-softirq=3323
rcu: rcu_preempt kthread starved for 10502 jiffies! g12417 f0x0 RCU_GP_WAIT_FQS(5) ->state=0x402 ->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:I stack:26632 pid:16 tgid:16 ppid:2 task_flags:0x208040 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5357 [inline]
__schedule+0x1798/0x4cc0 kernel/sched/core.c:6961
__schedule_loop kernel/sched/core.c:7043 [inline]
schedule+0x165/0x360 kernel/sched/core.c:7058
schedule_timeout+0x12b/0x270 kernel/time/sleep_timeout.c:99
rcu_gp_fqs_loop+0x301/0x1540 kernel/rcu/tree.c:2083
rcu_gp_kthread+0x99/0x390 kernel/rcu/tree.c:2285
kthread+0x70e/0x8a0 kernel/kthread.c:463
ret_from_fork+0x436/0x7d0 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>


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