syzbot
INFO: rcu detected stall in mld_dad_work
Status:
upstream: reported on 2026/09/21 10:36
Reported-by: syzbot+223d3220e0f0516420a2@syzkaller.appspotmail.com
First crash: 1d15h, last: 1d15h
Sample crash report:
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)
rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
rcu: 0-....: (1 GPs behind) idle=159/1/0x4000000000000002 softirq=83290/83291 fqs=4069
(detected by 1, t=10502 jiffies, g=111373, q=424671)
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 10289 Comm: kworker/0:52 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: mld mld_dad_work
RIP: 0010:__sanitizer_cov_trace_pc+0x0/0x60 kernel/kcov.c:201
Code: 2e 0f 1f 84 00 00 00 00 00 90 53 48 89 fb e8 17 00 00 00 48 8b 3d 80 0c 12 0c 48 89 de 5b e9 47 6b 44 00 00 00 cc cc 00 00 cc <48> 8b 04 24 65 48 8b 0d 14 5b 89 7e 65 8b 15 15 5b 89 7e 81 e2 00
RSP: 0000:ffffc90000007250 EFLAGS: 00000083
RAX: 0000000000000001 RBX: 0000000000000001 RCX: ffff8880395a0000
RDX: 0000000000000100 RSI: ffffffff8a7a48a0 RDI: ffff8880395a0000
RBP: ffffc90000007390 R08: ffffc90000007317 R09: ffffc90000007300
R10: dffffc0000000000 R11: fffff52000000e63 R12: 1ffff92000000e5c
R13: ffffc900000073e0 R14: dffffc0000000000 R15: ffff88809f4ed390
FS: 0000000000000000(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fffb51f9018 CR3: 000000000c08e000 CR4: 00000000003506f0
DR0: 0000200000000300 DR1: 0000200000000300 DR2: 0000200000000300
DR3: 0000200000000300 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
<IRQ>
rcu_lock_release+0x5/0x40 include/linux/rcupdate.h:317
__perf_output_begin kernel/events/ring_buffer.c:262 [inline]
perf_output_begin_forward+0x793/0xa30 kernel/events/ring_buffer.c:271
__perf_event_output kernel/events/core.c:7814 [inline]
perf_event_output_forward+0x19b/0x2e0 kernel/events/core.c:7832
__perf_event_overflow+0x35f/0x550 kernel/events/core.c:9525
perf_swevent_overflow kernel/events/core.c:9601 [inline]
perf_swevent_event+0x4b8/0x540 kernel/events/core.c:9639
perf_tp_event+0x324/0xbe0 kernel/events/core.c:10057
perf_trace_run_bpf_submit+0xf3/0x1c0 kernel/events/core.c:10031
perf_trace_preemptirq_template+0x2aa/0x360 include/trace/events/preemptirq.h:14
trace_irq_enable_rcuidle+0x108/0x180 include/trace/events/preemptirq.h:40
trace_hardirqs_on+0x57/0x80 kernel/trace/trace_preemptirq.c:44
asm_sysvec_irq_work+0x16/0x20 arch/x86/include/asm/idtentry.h:713
RIP: 0010:rcu_read_unlock_special+0x7f/0x4a0 kernel/rcu/tree_plugin.h:674
Code: eb 03 48 b8 f1 f1 f1 f1 f8 f2 f2 f2 4a 89 04 2b 42 c7 44 2b 08 f8 f3 f3 f3 65 44 8b 35 42 0b 9d 7e 41 f7 c6 00 00 f0 00 74 40 <48> c7 44 24 20 0e 36 e0 45 4a c7 04 2b 00 00 00 00 42 c7 44 2b 08
RSP: 0000:ffffc90000007a20 EFLAGS: 00000206
RAX: b960cff1b8750800 RBX: 1ffff92000000f48 RCX: b960cff1b8750800
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a48c0
RBP: ffffc90000007b00 R08: ffffffff901f1157 R09: 1ffffffff203e22a
R10: dffffc0000000000 R11: fffffbfff203e22b R12: ffffffff8c323400
R13: dffffc0000000000 R14: 0000000000000246 R15: 0000000000000001
__rcu_read_unlock+0x78/0xd0 kernel/rcu/tree_plugin.h:422
rcu_read_unlock include/linux/rcupdate.h:772 [inline]
process_backlog+0x3e5/0x770 net/core/dev.c:6543
__napi_poll+0xbb/0x430 net/core/dev.c:7101
napi_poll net/core/dev.c:7168 [inline]
net_rx_action+0x522/0xa80 net/core/dev.c:7258
handle_softirqs+0x336/0x830 kernel/softirq.c:576
__do_softirq kernel/softirq.c:610 [inline]
invoke_softirq kernel/softirq.c:450 [inline]
__irq_exit_rcu+0x13b/0x230 kernel/softirq.c:659
irq_exit_rcu+0x5/0x20 kernel/softirq.c:671
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline]
sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108
</IRQ>
<TASK>
asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676
RIP: 0010:___slab_alloc+0xcf7/0xdd0 mm/slub.c:3079
Code: 48 c7 44 24 40 00 00 00 00 9c 8f 44 24 40 f7 44 24 40 00 02 00 00 75 44 f7 c5 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 <48> 3b 44 24 48 75 6a 4c 89 e8 48 83 c4 50 5b 41 5c 41 5d 41 5e 41
RSP: 0000:ffffc900043278c0 EFLAGS: 00000206
RAX: b960cff1b8750800 RBX: ffff8880b903dfb0 RCX: b960cff1b8750800
RDX: dffffc0000000000 RSI: ffffffff8a2b2be0 RDI: ffffffff8a7a48c0
RBP: 0000000000000246 R08: ffffffff901f1157 R09: 1ffffffff203e22a
R10: dffffc0000000000 R11: fffffbfff203e22b R12: 0000000000000000
R13: ffff8880932b9000 R14: 0000000000000000 R15: ffff8880b903dfb0
__slab_alloc mm/slub.c:3100 [inline]
slab_alloc_node mm/slub.c:3191 [inline]
__kmalloc_node_track_caller+0x13d/0x3a0 mm/slub.c:4963
kmalloc_reserve net/core/skbuff.c:356 [inline]
__alloc_skb+0x22c/0x750 net/core/skbuff.c:427
alloc_skb include/linux/skbuff.h:1162 [inline]
mld_newpack+0x12f/0xba0 net/ipv6/mcast.c:1773
add_grhead net/ipv6/mcast.c:1884 [inline]
add_grec+0x1364/0x1840 net/ipv6/mcast.c:2023
mld_send_initial_cr+0x288/0x540 net/ipv6/mcast.c:2268
mld_dad_work+0x39/0x470 net/ipv6/mcast.c:2294
process_one_work+0x867/0xff0 kernel/workqueue.c:2310
worker_thread+0xad7/0x12a0 kernel/workqueue.c:2457
kthread+0x42e/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
net_ratelimit: 35443 callbacks suppressed
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:0c, 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: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 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: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: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 veth0_to_bridge with own address as source address (addr:c2:c7:4d:22:6c:84, vlan:0)
net_ratelimit: 38397 callbacks suppressed
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:0c, 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 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: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:0c, 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: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)
* Struck through repros no longer work on HEAD.