============================================
WARNING: possible recursive locking detected
syzkaller #0 Tainted: G L
--------------------------------------------
swapper/0/0 is trying to acquire lock:
ffff88804d0715e0 (&br->multicast_lock){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline]
ffff88804d0715e0 (&br->multicast_lock){+.-.}-{3:3}, at: br_ip4_multicast_query net/bridge/br_multicast.c:3500 [inline]
ffff88804d0715e0 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_ipv4_rcv net/bridge/br_multicast.c:3914 [inline]
ffff88804d0715e0 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_rcv+0xbf4/0x6a10 net/bridge/br_multicast.c:4030
but task is already holding lock:
ffff8880276715e0 (&br->multicast_lock){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline]
ffff8880276715e0 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_port_query_expired+0x61/0x350 net/bridge/br_multicast.c:1903
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&br->multicast_lock);
lock(&br->multicast_lock);
*** DEADLOCK ***
May be due to missing lock nesting notation
5 locks held by swapper/0/0:
#0: ffffc90000007c98 ((&pmctx->ip4_own_query.timer)){+.-.}-{0:0}, at: call_timer_fn+0x11f/0x640 kernel/time/timer.c:1745
#1: ffff8880276715e0 (&br->multicast_lock){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline]
#1: ffff8880276715e0 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_port_query_expired+0x61/0x350 net/bridge/br_multicast.c:1903
#2: ffffffff8e7e5480 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline]
#2: ffffffff8e7e5480 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline]
#2: ffffffff8e7e5480 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x296/0x4950 net/core/dev.c:4791
#3: ffffffff8e7e5480 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline]
#3: ffffffff8e7e5480 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline]
#3: ffffffff8e7e5480 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x296/0x4950 net/core/dev.c:4791
#4: ffffffff8e7e54e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#4: ffffffff8e7e54e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
#4: ffffffff8e7e54e0 (rcu_read_lock){....}-{1:3}, at: br_dev_xmit+0x181/0x18e0 net/bridge/br_device.c:52
stack backtrace:
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Call Trace:
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_deadlock_bug.cold+0xbd/0xca kernel/locking/lockdep.c:3041
check_deadlock kernel/locking/lockdep.c:3093 [inline]
validate_chain kernel/locking/lockdep.c:3895 [inline]
__lock_acquire+0x12bb/0x2630 kernel/locking/lockdep.c:5237
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b1/0x370 kernel/locking/lockdep.c:5825
__raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:158
spin_lock include/linux/spinlock.h:342 [inline]
br_ip4_multicast_query net/bridge/br_multicast.c:3500 [inline]
br_multicast_ipv4_rcv net/bridge/br_multicast.c:3914 [inline]
br_multicast_rcv+0xbf4/0x6a10 net/bridge/br_multicast.c:4030
br_dev_xmit+0x9d3/0x18e0 net/bridge/br_device.c:98
__netdev_start_xmit include/linux/netdevice.h:5368 [inline]
netdev_start_xmit include/linux/netdevice.h:5377 [inline]
xmit_one net/core/dev.c:3888 [inline]
dev_hard_start_xmit+0x128/0x7a0 net/core/dev.c:3904
__dev_queue_xmit+0x1baa/0x4950 net/core/dev.c:4870
dev_queue_xmit include/linux/netdevice.h:3418 [inline]
team_dev_queue_xmit include/linux/if_team.h:249 [inline]
lb_transmit+0x24d/0x6c0 drivers/net/team/team_mode_loadbalance.c:230
team_xmit+0x351/0x470 drivers/net/team/team_core.c:1848
__netdev_start_xmit include/linux/netdevice.h:5368 [inline]
netdev_start_xmit include/linux/netdevice.h:5377 [inline]
xmit_one net/core/dev.c:3888 [inline]
dev_hard_start_xmit+0x128/0x7a0 net/core/dev.c:3904
__dev_queue_xmit+0x1baa/0x4950 net/core/dev.c:4870
dev_queue_xmit include/linux/netdevice.h:3418 [inline]
br_dev_queue_push_xmit+0x361/0x530 net/bridge/br_forward.c:53
NF_HOOK include/linux/netfilter.h:318 [inline]
__br_multicast_send_query+0x298a/0x41b0 net/bridge/br_multicast.c:1807
br_multicast_send_query+0x2d0/0x540 net/bridge/br_multicast.c:1886
br_multicast_port_query_expired+0x288/0x350 net/bridge/br_multicast.c:1911
call_timer_fn+0x19a/0x640 kernel/time/timer.c:1748
expire_timers kernel/time/timer.c:1799 [inline]
__run_timers+0x75f/0xaf0 kernel/time/timer.c:2374
__run_timer_base kernel/time/timer.c:2386 [inline]
__run_timer_base kernel/time/timer.c:2378 [inline]
run_timer_base+0x114/0x190 kernel/time/timer.c:2395
run_timer_softirq+0x1a/0x50 kernel/time/timer.c:2405
handle_softirqs+0x1ea/0xa00 kernel/softirq.c:622
__do_softirq kernel/softirq.c:656 [inline]
invoke_softirq kernel/softirq.c:496 [inline]
__irq_exit_rcu+0x162/0x210 kernel/softirq.c:735
irq_exit_rcu+0x9/0x30 kernel/softirq.c:752
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1061 [inline]
sysvec_apic_timer_interrupt+0xa3/0xc0 arch/x86/kernel/apic/apic.c:1061
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:63
Code: 46 93 02 e9 c3 42 03 00 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d a3 80 21 00 fb f4 cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffffff8e407e00 EFLAGS: 00000246
RAX: 0000000004e71dc3 RBX: ffffffff8e4955c0 RCX: ffffffff8b8a1045
RDX: 0000000000000000 RSI: ffffffff8df1fea8 RDI: ffffffff8c1c3600
RBP: 0000000000000000 R08: 0000000000000001 R09: ffffed10170867b5
R10: ffff8880b8433dab R11: 0000000000000000 R12: 0000000000000000
R13: fffffbfff1c92ab8 R14: 0000000000000000 R15: ffffffff90d79b50
arch_safe_halt arch/x86/include/asm/paravirt.h:62 [inline]
default_idle+0x9/0x10 arch/x86/kernel/process.c:767
default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x464/0x590 kernel/sched/idle.c:352
cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:451
rest_init+0x251/0x260 init/main.c:762
start_kernel+0x484/0x490 init/main.c:1220
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x12b/0x130 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x148
----------------
Code disassembly (best guess):
0: 46 93 rex.RX xchg %eax,%ebx
2: 02 e9 add %cl,%ch
4: c3 ret
5: 42 03 00 rex.X add (%rax),%eax
8: 0f 1f 00 nopl (%rax)
b: 90 nop
c: 90 nop
d: 90 nop
e: 90 nop
f: 90 nop
10: 90 nop
11: 90 nop
12: 90 nop
13: 90 nop
14: 90 nop
15: 90 nop
16: 90 nop
17: 90 nop
18: 90 nop
19: 90 nop
1a: 90 nop
1b: f3 0f 1e fa endbr64
1f: 66 90 xchg %ax,%ax
21: 0f 00 2d a3 80 21 00 verw 0x2180a3(%rip) # 0x2180cb
28: fb sti
29: f4 hlt
* 2a: c3 ret <-- trapping instruction
2b: cc int3
2c: cc int3
2d: cc int3
2e: cc int3
2f: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1)
36: 00 00 00
39: 66 90 xchg %ax,%ax
3b: 90 nop
3c: 90 nop
3d: 90 nop
3e: 90 nop
3f: 90 nop