[v6.1] INFO: rcu detected stall in br_handle_frame (2)

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Oct 6, 2025, 2:18:33 PM (12 days ago) Oct 6
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Hello,

syzbot found the following issue on:

HEAD commit: 882efbdd9d34 Linux 6.1.155
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17b84ee2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=7eb38bd5021fec61
dashboard link: https://syzkaller.appspot.com/bug?extid=f80e255c3d4ba8ded1e0
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/92dcc467d133/disk-882efbdd.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9b1ac6d1ee0e/vmlinux-882efbdd.xz
kernel image: https://storage.googleapis.com/syzbot-assets/afb3b2815837/bzImage-882efbdd.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f80e25...@syzkaller.appspotmail.com

rcu: INFO: rcu_preempt detected expedited stalls on CPUs/tasks: { 0-.... } 2657 jiffies s: 23877 root: 0x1/.
rcu: blocking rcu_node structures (internal RCU debug):
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8444 Comm: syz.3.1361 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
RIP: 0010:rdtsc_ordered arch/x86/include/asm/msr.h:215 [inline]
RIP: 0010:read_tsc+0x3/0x10 arch/x86/kernel/tsc.c:1095
Code: 38 c1 0f 8c fd fe ff ff 4c 89 ff e8 37 7d a2 00 e9 f0 fe ff ff e8 cd 13 e9 08 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 0f 01 f9 <66> 90 48 c1 e2 20 48 09 d0 c3 0f 1f 00 48 c7 c0 4c 37 1f 8e 48 c1
RSP: 0018:ffffc900000060e8 EFLAGS: 00000046
RAX: 000000007276476a RBX: ffffffff8c9645c0 RCX: 0000000000000000
RDX: 00000000000000be RSI: 0000000000000000 RDI: ffffffff8c9645c0
RBP: 0000000000000019 R08: dffffc0000000000 R09: fffffbfff1c3ecb6
R10: fffffbfff1c3ecb6 R11: 1ffffffff1c3ecb5 R12: ffff8880b8e2a5d0
R13: dffffc0000000000 R14: 00000000000110ec R15: dffffc0000000000
FS: 00007fe63aa4c6c0(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f32a53f5f98 CR3: 00000000603c6000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
tk_clock_read kernel/time/timekeeping.c:195 [inline]
timekeeping_get_delta kernel/time/timekeeping.c:255 [inline]
timekeeping_get_ns kernel/time/timekeeping.c:388 [inline]
ktime_get_update_offsets_now+0xf8/0x3e0 kernel/time/timekeeping.c:2320
hrtimer_update_base kernel/time/hrtimer.c:659 [inline]
hrtimer_interrupt+0x130/0x9c0 kernel/time/hrtimer.c:1855
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1107 [inline]
__sysvec_apic_timer_interrupt+0x153/0x5a0 arch/x86/kernel/apic/apic.c:1124
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0x4d/0xc0 arch/x86/kernel/apic/apic.c:1118
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xa5/0x100 kernel/locking/spinlock.c:194
Code: 74 05 e8 8e 80 65 f7 48 c7 44 24 20 00 00 00 00 9c 8f 44 24 20 f6 44 24 21 02 75 4b f7 c3 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 96 0b 36 f7 65 8b 05 97 c4 e0 75 85 c0 74 3c 48 c7 04 24 0e 36
RSP: 0018:ffffc90000006380 EFLAGS: 00000206
RAX: 5cbbe516a2b5cf00 RBX: 0000000000000a02 RCX: 5cbbe516a2b5cf00
RDX: dffffc0000000000 RSI: ffffffff8a8c0500 RDI: 0000000000000001
RBP: ffffc90000006408 R08: dffffc0000000000 R09: fffffbfff215c44f
R10: fffffbfff215c44f R11: 1ffffffff215c44e R12: dffffc0000000000
R13: ffff88805c97e640 R14: ffff8880b8e3bdd0 R15: 1ffff92000000c70
spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
rps_unlock_irq_restore net/core/dev.c:241 [inline]
enqueue_to_backlog+0x95d/0xd30 net/core/dev.c:4772
netif_rx_internal+0x131/0x560 net/core/dev.c:5046
__netif_rx+0x74/0xb0 net/core/dev.c:5066
veth_forward_skb drivers/net/veth.c:290 [inline]
veth_xmit+0x650/0xb00 drivers/net/veth.c:343
__netdev_start_xmit include/linux/netdevice.h:4896 [inline]
netdev_start_xmit include/linux/netdevice.h:4910 [inline]
xmit_one net/core/dev.c:3670 [inline]
dev_hard_start_xmit+0x262/0x870 net/core/dev.c:3686
__dev_queue_xmit+0x1bf1/0x3760 net/core/dev.c:4346
dev_queue_xmit include/linux/netdevice.h:3051 [inline]
br_dev_queue_push_xmit+0x6a2/0x850 net/bridge/br_forward.c:53
NF_HOOK+0x5f7/0x680 include/linux/netfilter.h:302
br_nf_post_routing+0xa0d/0xe40 net/bridge/br_netfilter_hooks.c:977
nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
nf_hook_slow+0xb9/0x200 net/netfilter/core.c:614
nf_hook include/linux/netfilter.h:257 [inline]
NF_HOOK+0x20f/0x3d0 include/linux/netfilter.h:300
br_forward_finish+0xcf/0x120 net/bridge/br_forward.c:66
br_nf_hook_thresh net/bridge/br_netfilter_hooks.c:-1 [inline]
br_nf_forward_finish+0x96a/0xee0 net/bridge/br_netfilter_hooks.c:684
NF_HOOK+0x5f7/0x680 include/linux/netfilter.h:302
br_nf_forward_ip+0xc7d/0x1140 net/bridge/br_netfilter_hooks.c:754
nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
nf_hook_slow+0xb9/0x200 net/netfilter/core.c:614
nf_hook include/linux/netfilter.h:257 [inline]
NF_HOOK+0x20f/0x3d0 include/linux/netfilter.h:300
__br_forward+0x41f/0x600 net/bridge/br_forward.c:115
br_handle_frame_finish+0x12bf/0x1710 net/bridge/br_input.c:198
br_nf_hook_thresh+0x3b2/0x480 net/bridge/br_netfilter_hooks.c:1184
br_nf_pre_routing_finish_ipv6+0x9e1/0xda0 net/bridge/br_netfilter_ipv6.c:-1
NF_HOOK include/linux/netfilter.h:302 [inline]
br_nf_pre_routing_ipv6+0x349/0x670 net/bridge/br_netfilter_ipv6.c:243
nf_hook_entry_hookfn include/linux/netfilter.h:142 [inline]
nf_hook_bridge_pre net/bridge/br_input.c:260 [inline]
br_handle_frame+0x919/0x12f0 net/bridge/br_input.c:406
__netif_receive_skb_core+0xfc5/0x3840 net/core/dev.c:5475
__netif_receive_skb_one_core net/core/dev.c:5579 [inline]
__netif_receive_skb+0x74/0x290 net/core/dev.c:5695
process_backlog+0x37c/0x6e0 net/core/dev.c:6023
__napi_poll+0xc0/0x460 net/core/dev.c:6590
napi_poll net/core/dev.c:6657 [inline]
net_rx_action+0x5b1/0xad0 net/core/dev.c:6771
handle_softirqs+0x2a1/0x920 kernel/softirq.c:596
__do_softirq kernel/softirq.c:630 [inline]
invoke_softirq kernel/softirq.c:470 [inline]
__irq_exit_rcu+0x12f/0x220 kernel/softirq.c:679
irq_exit_rcu+0x5/0x20 kernel/softirq.c:691
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1118 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1118
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:691
RIP: 0010:schedule_debug kernel/sched/core.c:5802 [inline]
RIP: 0010:__schedule+0x14d/0x40b0 kernel/sched/core.c:6454
Code: f7 48 8b 1b 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 80 3c 08 00 74 08 48 89 df e8 da 0b b1 f7 48 81 3b 9d 6e ac 57 <0f> 85 4f 12 00 00 45 85 ff 75 56 49 8d 5c 24 18 48 89 d8 48 c1 e8
RSP: 0018:ffffc90003ae7ae0 EFLAGS: 00000246
RAX: 1ffff9200075c000 RBX: ffffc90003ae0000 RCX: dffffc0000000000
RDX: 0000000000000010 RSI: 0000000000000000 RDI: ffffc90003ae7c10
RBP: ffffc90003ae7c70 R08: dffffc0000000000 R09: ffffc90003ae7c00
R10: fffff5200075cf82 R11: 1ffff9200075cf80 R12: ffff88802f039dc0
R13: ffff8880b8e00000 R14: dffffc0000000000 R15: 0000000000000001
preempt_schedule_notrace+0xca/0x110 kernel/sched/core.c:6823
preempt_schedule_notrace_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:35
trace_lock_release include/trace/events/lock.h:69 [inline]
lock_release+0x8af/0x910 kernel/locking/lockdep.c:5673
__sys_socketpair+0xaa/0x540 net/socket.c:1720
__do_sys_socketpair net/socket.c:1786 [inline]
__se_sys_socketpair net/socket.c:1783 [inline]
__x64_sys_socketpair+0x97/0xb0 net/socket.c:1783
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fe639b8eec9
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:00007fe63aa4c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000035
RAX: ffffffffffffffda RBX: 00007fe639de5fa0 RCX: 00007fe639b8eec9
RDX: 0000000000000001 RSI: 0000000000000803 RDI: 000000000000001d
RBP: 00007fe639c11f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000200000000040 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe639de6038 R14: 00007fe639de5fa0 R15: 00007ffec7b347f8
</TASK>


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