============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- kworker/0:17/8720 is trying to acquire lock: ffff8880551f9070 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] ffff8880551f9070 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 but task is already holding lock: ffff88804b339070 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] ffff88804b339070 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x237/0x360 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 locks held by kworker/0:17/8720: 13, last CPU#0: #0: ffff88803274b940 ((wq_completion)mld){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #0: ffff88803274b940 ((wq_completion)mld){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #0: ffff88803274b940 ((wq_completion)mld){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline] #0: ffff88803274b940 ((wq_completion)mld){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479 #1: ffffc90006907c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #1: ffffc90006907c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #1: ffffc90006907c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline] #1: ffffc90006907c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479 #2: ffff88802e965530 (&idev->mc_lock){+.+.}-{4:4}, at: mld_ifc_work+0x2d/0xd60 net/ipv6/mcast.c:2738 #3: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #3: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #3: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: mld_sendpack+0x206/0xe10 net/ipv6/mcast.c:1862 #4: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #4: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #4: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x11e/0x540 net/ipv6/ip6_output.c:236 #5: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline] #5: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:4908 #6: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #6: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #6: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: hsr_dev_xmit+0x2d/0x360 net/hsr/hsr_device.c:229 #7: ffff88804b339070 (&hsr->seqnr_lock){+.-.}-{3:3}, at: spin_lock_bh include/linux/spinlock.h:353 [inline] #7: ffff88804b339070 (&hsr->seqnr_lock){+.-.}-{3:3}, at: hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 #8: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #8: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #8: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: hsr_forward_skb+0xb9/0x2b70 net/hsr/hsr_forward.c:772 #9: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #9: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline] #9: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:4908 #10: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #10: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #10: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: br_dev_xmit+0x182/0x19b0 net/bridge/br_device.c:52 #11: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #11: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:902 [inline] #11: ffffffff8ed5c900 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x29b/0x3920 net/core/dev.c:4908 #12: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline] #12: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline] #12: ffffffff8ed5c8a0 (rcu_read_lock){....}-{1:3}, at: hsr_dev_xmit+0x2d/0x360 net/hsr/hsr_device.c:229 stack backtrace: CPU: 0 UID: 0 PID: 8720 Comm: kworker/0:17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 Workqueue: mld mld_ifc_work Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_deadlock_bug+0x27a/0x290 kernel/locking/lockdep.c:3085 check_deadlock kernel/locking/lockdep.c:3137 [inline] validate_chain kernel/locking/lockdep.c:3939 [inline] __lock_acquire+0x25db/0x2de0 kernel/locking/lockdep.c:5288 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 __raw_spin_lock_bh include/linux/spinlock_api_smp.h:182 [inline] _raw_spin_lock_bh+0x36/0x50 kernel/locking/spinlock.c:205 spin_lock_bh include/linux/spinlock.h:353 [inline] hsr_dev_xmit+0x237/0x360 net/hsr/hsr_device.c:235 __netdev_start_xmit include/linux/netdevice.h:5433 [inline] netdev_start_xmit include/linux/netdevice.h:5442 [inline] xmit_one net/core/dev.c:3989 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:4005 __dev_queue_xmit+0x14d1/0x3920 net/core/dev.c:4994 dev_queue_xmit include/linux/netdevice.h:3462 [inline] br_dev_queue_push_xmit+0x370/0x4b0 net/bridge/br_forward.c:67 NF_HOOK+0x360/0x3f0 include/linux/netfilter.h:325 br_forward_finish+0xd3/0x130 net/bridge/br_forward.c:80 NF_HOOK+0x360/0x3f0 include/linux/netfilter.h:325 __br_forward+0x41e/0x5d0 net/bridge/br_forward.c:130 deliver_clone net/bridge/br_forward.c:146 [inline] maybe_deliver+0x373/0x5b0 net/bridge/br_forward.c:212 br_flood+0x142/0x650 net/bridge/br_forward.c:345 br_dev_xmit+0x11d1/0x19b0 net/bridge/br_device.c:109 __netdev_start_xmit include/linux/netdevice.h:5433 [inline] netdev_start_xmit include/linux/netdevice.h:5442 [inline] xmit_one net/core/dev.c:3989 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:4005 __dev_queue_xmit+0x14d1/0x3920 net/core/dev.c:4994 dev_queue_xmit include/linux/netdevice.h:3462 [inline] hsr_xmit net/hsr/hsr_forward.c:440 [inline] hsr_forward_do net/hsr/hsr_forward.c:603 [inline] hsr_forward_skb+0x1701/0x2b70 net/hsr/hsr_forward.c:777 hsr_dev_xmit+0x242/0x360 net/hsr/hsr_device.c:236 __netdev_start_xmit include/linux/netdevice.h:5433 [inline] netdev_start_xmit include/linux/netdevice.h:5442 [inline] xmit_one net/core/dev.c:3989 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:4005 __dev_queue_xmit+0x14d1/0x3920 net/core/dev.c:4994 NF_HOOK_COND include/linux/netfilter.h:314 [inline] ip6_output+0x337/0x540 net/ipv6/ip6_output.c:248 dst_output include/net/dst.h:472 [inline] NF_HOOK+0x177/0x4f0 include/linux/netfilter.h:325 mld_sendpack+0x890/0xe10 net/ipv6/mcast.c:1890 mld_send_cr net/ipv6/mcast.c:2191 [inline] mld_ifc_work+0x842/0xd60 net/ipv6/mcast.c:2739 process_one_work kernel/workqueue.c:3396 [inline] process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3479 worker_thread+0xa47/0xfb0 kernel/workqueue.c:3560 kthread+0x38b/0x480 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