============================================ WARNING: possible recursive locking detected 6.16.0-rc5-syzkaller-00266-g3f31a806a62e #0 Not tainted -------------------------------------------- syz.6.3462/22585 is trying to acquire lock: ffff88805d76d508 (&br->multicast_lock){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff88805d76d508 (&br->multicast_lock){+.-.}-{3:3}, at: br_ip6_multicast_query net/bridge/br_multicast.c:3592 [inline] ffff88805d76d508 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_ipv6_rcv net/bridge/br_multicast.c:3988 [inline] ffff88805d76d508 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_rcv+0x2d0b/0x74b0 net/bridge/br_multicast.c:4043 but task is already holding lock: ffff8880354fd508 (&br->multicast_lock){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff8880354fd508 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_port_query_expired+0x62/0x370 net/bridge/br_multicast.c:1905 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 7 locks held by syz.6.3462/22585: #0: ffffc90000a08be0 ((&pmctx->ip6_own_query.timer)){+.-.}-{0:0}, at: call_timer_fn+0xbe/0x5f0 kernel/time/timer.c:1744 #1: ffff8880354fd508 (&br->multicast_lock){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] #1: ffff8880354fd508 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_port_query_expired+0x62/0x370 net/bridge/br_multicast.c:1905 #2: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #2: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:892 [inline] #2: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27e/0x3a70 net/core/dev.c:4638 #3: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #3: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:892 [inline] #3: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27e/0x3a70 net/core/dev.c:4638 #4: ffffffff8e13f0a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #4: ffffffff8e13f0a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #4: ffffffff8e13f0a0 (rcu_read_lock){....}-{1:3}, at: bond_start_xmit+0x101/0x1a90 drivers/net/bonding/bond_main.c:5607 #5: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:892 [inline] #5: ffffffff8e13f100 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27e/0x3a70 net/core/dev.c:4638 #6: ffffffff8e13f0a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #6: ffffffff8e13f0a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #6: ffffffff8e13f0a0 (rcu_read_lock){....}-{1:3}, at: br_dev_xmit+0x185/0x1840 net/bridge/br_device.c:52 stack backtrace: CPU: 1 UID: 0 PID: 22585 Comm: syz.6.3462 Not tainted 6.16.0-rc5-syzkaller-00266-g3f31a806a62e #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_deadlock_bug+0x28b/0x2a0 kernel/locking/lockdep.c:3044 check_deadlock kernel/locking/lockdep.c:3096 [inline] validate_chain+0x1a3f/0x2140 kernel/locking/lockdep.c:3898 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] br_ip6_multicast_query net/bridge/br_multicast.c:3592 [inline] br_multicast_ipv6_rcv net/bridge/br_multicast.c:3988 [inline] br_multicast_rcv+0x2d0b/0x74b0 net/bridge/br_multicast.c:4043 br_dev_xmit+0xaf7/0x1840 net/bridge/br_device.c:98 __netdev_start_xmit include/linux/netdevice.h:5215 [inline] netdev_start_xmit include/linux/netdevice.h:5224 [inline] xmit_one net/core/dev.c:3830 [inline] dev_hard_start_xmit+0x2d4/0x830 net/core/dev.c:3846 __dev_queue_xmit+0x1adf/0x3a70 net/core/dev.c:4713 __bond_start_xmit include/linux/netdevice.h:-1 [inline] bond_start_xmit+0x1207/0x1a90 drivers/net/bonding/bond_main.c:5609 __netdev_start_xmit include/linux/netdevice.h:5215 [inline] netdev_start_xmit include/linux/netdevice.h:5224 [inline] xmit_one net/core/dev.c:3830 [inline] dev_hard_start_xmit+0x2d4/0x830 net/core/dev.c:3846 __dev_queue_xmit+0x1adf/0x3a70 net/core/dev.c:4713 dev_queue_xmit_accel include/linux/netdevice.h:3361 [inline] macvlan_queue_xmit drivers/net/macvlan.c:557 [inline] macvlan_start_xmit+0x46d/0x6e0 drivers/net/macvlan.c:581 __netdev_start_xmit include/linux/netdevice.h:5215 [inline] netdev_start_xmit include/linux/netdevice.h:5224 [inline] xmit_one net/core/dev.c:3830 [inline] dev_hard_start_xmit+0x2d4/0x830 net/core/dev.c:3846 __dev_queue_xmit+0x1adf/0x3a70 net/core/dev.c:4713 dev_queue_xmit include/linux/netdevice.h:3355 [inline] br_dev_queue_push_xmit+0x6c5/0x890 net/bridge/br_forward.c:53 NF_HOOK include/linux/netfilter.h:317 [inline] __br_multicast_send_query+0x2ea1/0x4580 net/bridge/br_multicast.c:1809 br_multicast_send_query+0x4d6/0x680 net/bridge/br_multicast.c:1888 br_multicast_port_query_expired+0x2a4/0x370 net/bridge/br_multicast.c:1913 call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747 expire_timers kernel/time/timer.c:1798 [inline] __run_timers kernel/time/timer.c:2372 [inline] __run_timer_base+0x61a/0x860 kernel/time/timer.c:2384 run_timer_base kernel/time/timer.c:2393 [inline] run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403 handle_softirqs+0x286/0x870 kernel/softirq.c:579 __do_softirq kernel/softirq.c:613 [inline] invoke_softirq kernel/softirq.c:453 [inline] __irq_exit_rcu+0xca/0x1f0 kernel/softirq.c:680 irq_exit_rcu+0x9/0x30 kernel/softirq.c:696 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline] sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1050 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702 RIP: 0010:__put_user_4+0xd/0x20 arch/x86/lib/putuser.S:94 Code: 66 89 01 31 c9 0f 01 ca c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 48 89 cb 48 c1 fb 3f 48 09 d9 0f 01 cb <89> 01 31 c9 0f 01 ca c3 cc cc cc cc 90 90 90 90 90 90 90 90 90 90 RSP: 0018:ffffc90004627c38 EFLAGS: 00040206 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000020000004dbb8 RDX: 0000000000000000 RSI: ffffffff8db869b0 RDI: ffffffff8be29d80 RBP: ffffc90004627e10 R08: 0000000000000000 R09: ffffffff820c2ce0 R10: dffffc0000000000 R11: fffff520008c4ecd R12: 000020000004db80 R13: dffffc0000000000 R14: 0000000000000002 R15: 000000000000136b do_recvmmsg+0x33c/0x770 net/socket.c:2929 __sys_recvmmsg net/socket.c:2997 [inline] __do_sys_recvmmsg net/socket.c:3020 [inline] __se_sys_recvmmsg net/socket.c:3013 [inline] __x64_sys_recvmmsg+0x190/0x240 net/socket.c:3013 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f83c178e929 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:00007f83c251b038 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007f83c19b6080 RCX: 00007f83c178e929 RDX: 0000000000010106 RSI: 00002000000000c0 RDI: 0000000000000003 RBP: 00007f83c1810b39 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000002 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f83c19b6080 R15: 00007f83c1adfa28 vkms_vblank_simulate: vblank timer overrun vkms_vblank_simulate: vblank timer overrun ---------------- Code disassembly (best guess): 0: 66 89 01 mov %ax,(%rcx) 3: 31 c9 xor %ecx,%ecx 5: 0f 01 ca clac 8: c3 ret 9: cc int3 a: cc int3 b: cc int3 c: cc int3 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: 90 nop 1c: 90 nop 1d: 48 89 cb mov %rcx,%rbx 20: 48 c1 fb 3f sar $0x3f,%rbx 24: 48 09 d9 or %rbx,%rcx 27: 0f 01 cb stac * 2a: 89 01 mov %eax,(%rcx) <-- trapping instruction 2c: 31 c9 xor %ecx,%ecx 2e: 0f 01 ca clac 31: c3 ret 32: cc int3 33: cc int3 34: cc int3 35: cc int3 36: 90 nop 37: 90 nop 38: 90 nop 39: 90 nop 3a: 90 nop 3b: 90 nop 3c: 90 nop 3d: 90 nop 3e: 90 nop 3f: 90 nop