============================================ WARNING: possible recursive locking detected syzkaller #0 Tainted: G L -------------------------------------------- kworker/0:2/867 is trying to acquire lock: ffff0000d6a6cff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline] ffff0000d6a6cff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x214/0x354 net/hsr/hsr_device.c:235 but task is already holding lock: ffff0000d6114ff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline] ffff0000d6114ff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x214/0x354 net/hsr/hsr_device.c:235 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&hsr->seqnr_lock); lock(&hsr->seqnr_lock); *** DEADLOCK *** May be due to missing lock nesting notation 13 locks held by kworker/0:2/867: #0: ffff0000ceb53940 ((wq_completion)mld){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline] #0: ffff0000ceb53940 ((wq_completion)mld){+.+.}-{0:0}, at: process_scheduled_works+0x748/0x1098 kernel/workqueue.c:3397 #1: ffff800093bc7c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3289 [inline] #1: ffff800093bc7c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x750/0x1098 kernel/workqueue.c:3397 #2: ffff0000dde66530 (&idev->mc_lock){+.+.}-{4:4}, at: mld_ifc_work+0x38/0x9dc net/ipv6/mcast.c:2692 #3: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #3: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #3: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: mld_sendpack+0x1b4/0xff0 net/ipv6/mcast.c:1827 #4: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #4: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #4: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x114/0x644 net/ipv6/ip6_output.c:234 #5: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #5: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:894 [inline] #5: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x234/0x2c18 net/core/dev.c:4791 #6: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #6: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #6: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: hsr_dev_xmit+0x48/0x354 net/hsr/hsr_device.c:229 #7: ffff0000d6114ff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:348 [inline] #7: ffff0000d6114ff0 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x214/0x354 net/hsr/hsr_device.c:235 #8: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #8: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #8: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: hsr_forward_skb+0xc8/0x22a0 net/hsr/hsr_forward.c:738 #9: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #9: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:894 [inline] #9: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x234/0x2c18 net/core/dev.c:4791 #10: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #10: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #10: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: br_dev_xmit+0x16c/0x14d8 net/bridge/br_device.c:52 #11: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #11: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:894 [inline] #11: ffff800088b673c0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x234/0x2c18 net/core/dev.c:4791 #12: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #12: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #12: ffff800088b67360 (rcu_read_lock){....}-{1:3}, at: hsr_dev_xmit+0x48/0x354 net/hsr/hsr_device.c:229 stack backtrace: CPU: 0 UID: 0 PID: 867 Comm: kworker/0:2 Tainted: G L syzkaller #0 PREEMPT Tainted: [L]=SOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Workqueue: mld mld_ifc_work Call trace: show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) __dump_stack+0x30/0x40 lib/dump_stack.c:94 dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 dump_stack+0x1c/0x28 lib/dump_stack.c:129 print_deadlock_bug+0x2e8/0x2f0 kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain kernel/locking/lockdep.c:3895 [inline] __lock_acquire+0x27ec/0x2f44 kernel/locking/lockdep.c:5237 lock_acquire+0x140/0x368 kernel/locking/lockdep.c:5868 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:150 [inline] _raw_spin_lock_bh+0x48/0x60 kernel/locking/spinlock.c:182 spin_lock_bh include/linux/spinlock.h:348 [inline] hsr_dev_xmit+0x214/0x354 net/hsr/hsr_device.c:235 __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+0x1e8/0x9ec net/core/dev.c:3904 __dev_queue_xmit+0xfc0/0x2c18 net/core/dev.c:4870 dev_queue_xmit include/linux/netdevice.h:3418 [inline] br_dev_queue_push_xmit+0x2e4/0x40c net/bridge/br_forward.c:53 rcu_read_unlock include/linux/rcupdate.h:867 [inline] nf_hook include/linux/netfilter.h:275 [inline] NF_HOOK+0x304/0x394 include/linux/netfilter.h:316 br_forward_finish+0xd4/0x11c net/bridge/br_forward.c:66 rcu_read_unlock include/linux/rcupdate.h:867 [inline] nf_hook include/linux/netfilter.h:275 [inline] NF_HOOK+0x304/0x394 include/linux/netfilter.h:316 __br_forward+0x2d8/0x43c net/bridge/br_forward.c:115 deliver_clone+0x6c/0xc8 net/bridge/br_forward.c:131 maybe_deliver+0x98/0x124 net/bridge/br_forward.c:191 br_flood+0x288/0x55c net/bridge/br_forward.c:238 br_dev_xmit+0xd90/0x14d8 net/bridge/br_device.c:-1 __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+0x1e8/0x9ec net/core/dev.c:3904 __dev_queue_xmit+0xfc0/0x2c18 net/core/dev.c:4870 dev_queue_xmit include/linux/netdevice.h:3418 [inline] hsr_xmit net/hsr/hsr_forward.c:440 [inline] hsr_forward_do net/hsr/hsr_forward.c:581 [inline] hsr_forward_skb+0x11e8/0x22a0 net/hsr/hsr_forward.c:743 hsr_dev_xmit+0x220/0x354 net/hsr/hsr_device.c:236 __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+0x1e8/0x9ec net/core/dev.c:3904 __dev_queue_xmit+0xfc0/0x2c18 net/core/dev.c:4870 dev_queue_xmit include/linux/netdevice.h:3418 [inline] neigh_connected_output+0x354/0x3e8 net/core/neighbour.c:1648 neigh_output include/net/neighbour.h:560 [inline] ip6_finish_output2+0xce4/0x1a7c net/ipv6/ip6_output.c:136 __ip6_finish_output net/ipv6/ip6_output.c:-1 [inline] ip6_finish_output+0x230/0x618 net/ipv6/ip6_output.c:219 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x2d0/0x644 net/ipv6/ip6_output.c:246 dst_output include/net/dst.h:470 [inline] NF_HOOK+0x14c/0x45c include/linux/netfilter.h:318 mld_sendpack+0x7fc/0xff0 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x760/0x9dc net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3314 [inline] process_scheduled_works+0x79c/0x1098 kernel/workqueue.c:3397 worker_thread+0x754/0xba0 kernel/workqueue.c:3478 kthread+0x2f8/0x3c8 kernel/kthread.c:436 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:842