====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ kworker/0:11/14961 is trying to acquire lock: ffff88807b4955c0 (&br->multicast_lock){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] ffff88807b4955c0 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_add_group net/bridge/br_multicast.c:1566 [inline] ffff88807b4955c0 (&br->multicast_lock){+.-.}-{3:3}, at: br_ip6_multicast_add_group net/bridge/br_multicast.c:1619 [inline] ffff88807b4955c0 (&br->multicast_lock){+.-.}-{3:3}, at: br_ip6_multicast_mld2_report net/bridge/br_multicast.c:3038 [inline] ffff88807b4955c0 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_ipv6_rcv net/bridge/br_multicast.c:3976 [inline] ffff88807b4955c0 (&br->multicast_lock){+.-.}-{3:3}, at: br_multicast_rcv+0x3b5f/0x7640 net/bridge/br_multicast.c:4034 but task is already holding lock: ffff88804872cff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline] ffff88804872cff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&hsr->seqnr_lock){+.-.}-{3:3}: __raw_spin_lock_bh include/linux/spinlock_api_smp.h:150 [inline] _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:182 spin_lock_bh include/linux/spinlock.h:348 [inline] hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 __netdev_start_xmit include/linux/netdevice.h:5371 [inline] netdev_start_xmit include/linux/netdevice.h:5380 [inline] xmit_one net/core/dev.c:3888 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3904 __dev_queue_xmit+0x14d9/0x3950 net/core/dev.c:4870 dev_queue_xmit include/linux/netdevice.h:3421 [inline] br_dev_queue_push_xmit+0x370/0x4b0 net/bridge/br_forward.c:53 NF_HOOK include/linux/netfilter.h:318 [inline] __br_multicast_send_query+0x2f4a/0x4630 net/bridge/br_multicast.c:1807 br_multicast_send_query+0x509/0x6b0 net/bridge/br_multicast.c:1886 br_multicast_port_query_expired net/bridge/br_multicast.c:1911 [inline] br_ip6_multicast_port_query_expired+0x2b5/0x380 net/bridge/br_multicast.c:1931 call_timer_fn+0x192/0x5e0 kernel/time/timer.c:1748 expire_timers kernel/time/timer.c:1799 [inline] __run_timers kernel/time/timer.c:2374 [inline] __run_timer_base+0x652/0x8b0 kernel/time/timer.c:2386 run_timer_base kernel/time/timer.c:2395 [inline] run_timer_softirq+0xb7/0x170 kernel/time/timer.c:2405 handle_softirqs+0x22a/0x840 kernel/softirq.c:622 __do_softirq kernel/softirq.c:656 [inline] invoke_softirq kernel/softirq.c:496 [inline] __irq_exit_rcu+0xca/0x220 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+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1061 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697 console_flush_one_record arch/x86/include/asm/irqflags.h:-1 [inline] console_flush_all+0x801/0xb20 kernel/printk/printk.c:3343 __console_flush_and_unlock kernel/printk/printk.c:3373 [inline] console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413 vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479 _printk+0xdd/0x130 kernel/printk/printk.c:2504 br_multicast_set_startup_query_intvl+0x158/0x160 net/bridge/br_multicast.c:-1 br_changelink+0x1073/0x18d0 net/bridge/br_netlink.c:1506 rtnl_changelink net/core/rtnetlink.c:3759 [inline] __rtnl_newlink net/core/rtnetlink.c:3972 [inline] rtnl_newlink+0x1607/0x1bb0 net/core/rtnetlink.c:4109 rtnetlink_rcv_msg+0x7d5/0xbe0 net/core/rtnetlink.c:6995 netlink_rcv_skb+0x232/0x4b0 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline] netlink_unicast+0x75c/0x8e0 net/netlink/af_netlink.c:1344 netlink_sendmsg+0x813/0xb40 net/netlink/af_netlink.c:1894 sock_sendmsg_nosec net/socket.c:787 [inline] __sock_sendmsg net/socket.c:802 [inline] ____sys_sendmsg+0x972/0x9f0 net/socket.c:2698 ___sys_sendmsg+0x2a5/0x360 net/socket.c:2752 __sys_sendmsg net/socket.c:2784 [inline] __do_sys_sendmsg net/socket.c:2789 [inline] __se_sys_sendmsg net/socket.c:2787 [inline] __x64_sys_sendmsg+0x1bd/0x2a0 net/socket.c:2787 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (&br->multicast_lock){+.-.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 __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_multicast_add_group net/bridge/br_multicast.c:1566 [inline] br_ip6_multicast_add_group net/bridge/br_multicast.c:1619 [inline] br_ip6_multicast_mld2_report net/bridge/br_multicast.c:3038 [inline] br_multicast_ipv6_rcv net/bridge/br_multicast.c:3976 [inline] br_multicast_rcv+0x3b5f/0x7640 net/bridge/br_multicast.c:4034 br_dev_xmit+0xb67/0x1990 net/bridge/br_device.c:98 __netdev_start_xmit include/linux/netdevice.h:5371 [inline] netdev_start_xmit include/linux/netdevice.h:5380 [inline] xmit_one net/core/dev.c:3888 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3904 __dev_queue_xmit+0x14d9/0x3950 net/core/dev.c:4870 dev_queue_xmit include/linux/netdevice.h:3421 [inline] hsr_xmit net/hsr/hsr_forward.c:440 [inline] hsr_forward_do net/hsr/hsr_forward.c:581 [inline] hsr_forward_skb+0x167e/0x2a80 net/hsr/hsr_forward.c:743 hsr_dev_xmit+0x242/0x360 net/hsr/hsr_device.c:236 __netdev_start_xmit include/linux/netdevice.h:5371 [inline] netdev_start_xmit include/linux/netdevice.h:5380 [inline] xmit_one net/core/dev.c:3888 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3904 __dev_queue_xmit+0x14d9/0x3950 net/core/dev.c:4870 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:246 dst_output include/net/dst.h:470 [inline] NF_HOOK+0x177/0x4f0 include/linux/netfilter.h:318 mld_sendpack+0x8b4/0xe40 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x835/0xe70 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3302 [inline] process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&hsr->seqnr_lock); lock(&br->multicast_lock); lock(&hsr->seqnr_lock); lock(&br->multicast_lock); *** DEADLOCK *** 11 locks held by kworker/0:11/14961: #0: ffff88803218d940 ((wq_completion)mld){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3277 [inline] #0: ffff88803218d940 ((wq_completion)mld){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3385 #1: ffffc90006967c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3278 [inline] #1: ffffc90006967c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3385 #2: ffff8880685e8530 (&idev->mc_lock){+.+.}-{4:4}, at: mld_ifc_work+0x2d/0xe70 net/ipv6/mcast.c:2692 #3: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #3: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #3: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: mld_sendpack+0x213/0xe40 net/ipv6/mcast.c:1827 #4: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #4: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #4: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x126/0x550 net/ipv6/ip6_output.c:234 #5: ffffffff8e95cd40 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8e95cd40 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline] #5: ffffffff8e95cd40 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x2b6/0x3950 net/core/dev.c:4791 #6: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #6: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #6: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: hsr_dev_xmit+0x2d/0x360 net/hsr/hsr_device.c:229 #7: ffff88804872cff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline] #7: ffff88804872cff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 #8: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #8: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #8: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: hsr_forward_skb+0xbb/0x2a80 net/hsr/hsr_forward.c:738 #9: ffffffff8e95cd40 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #9: ffffffff8e95cd40 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline] #9: ffffffff8e95cd40 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x2b6/0x3950 net/core/dev.c:4791 #10: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #10: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #10: ffffffff8e95cce0 (rcu_read_lock){....}-{1:3}, at: br_dev_xmit+0x193/0x1990 net/bridge/br_device.c:52 stack backtrace: CPU: 0 UID: 0 PID: 14961 Comm: kworker/0:11 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 Workqueue: mld mld_ifc_work Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868 __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_multicast_add_group net/bridge/br_multicast.c:1566 [inline] br_ip6_multicast_add_group net/bridge/br_multicast.c:1619 [inline] br_ip6_multicast_mld2_report net/bridge/br_multicast.c:3038 [inline] br_multicast_ipv6_rcv net/bridge/br_multicast.c:3976 [inline] br_multicast_rcv+0x3b5f/0x7640 net/bridge/br_multicast.c:4034 br_dev_xmit+0xb67/0x1990 net/bridge/br_device.c:98 __netdev_start_xmit include/linux/netdevice.h:5371 [inline] netdev_start_xmit include/linux/netdevice.h:5380 [inline] xmit_one net/core/dev.c:3888 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3904 __dev_queue_xmit+0x14d9/0x3950 net/core/dev.c:4870 dev_queue_xmit include/linux/netdevice.h:3421 [inline] hsr_xmit net/hsr/hsr_forward.c:440 [inline] hsr_forward_do net/hsr/hsr_forward.c:581 [inline] hsr_forward_skb+0x167e/0x2a80 net/hsr/hsr_forward.c:743 hsr_dev_xmit+0x242/0x360 net/hsr/hsr_device.c:236 __netdev_start_xmit include/linux/netdevice.h:5371 [inline] netdev_start_xmit include/linux/netdevice.h:5380 [inline] xmit_one net/core/dev.c:3888 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3904 __dev_queue_xmit+0x14d9/0x3950 net/core/dev.c:4870 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:246 dst_output include/net/dst.h:470 [inline] NF_HOOK+0x177/0x4f0 include/linux/netfilter.h:318 mld_sendpack+0x8b4/0xe40 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x835/0xe70 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3302 [inline] process_scheduled_works+0xb5d/0x1860 kernel/workqueue.c:3385 worker_thread+0xa53/0xfc0 kernel/workqueue.c:3466 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245