============================================ WARNING: possible recursive locking detected 6.1.146-syzkaller #0 Not tainted -------------------------------------------- kworker/1:3/4270 is trying to acquire lock: ffff888023eda218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888023eda218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3925 [inline] ffff888023eda218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x208f/0x3760 net/core/dev.c:4300 but task is already holding lock: ffff888028a5c258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:361 [inline] ffff888028a5c258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:195 [inline] ffff888028a5c258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3882 [inline] ffff888028a5c258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x129a/0x3760 net/core/dev.c:4300 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock); *** DEADLOCK *** May be due to missing lock nesting notation 14 locks held by kworker/1:3/4270: #0: ffff88802fff0d38 ((wq_completion)mld){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267 #1: ffffc90004087d00 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7a1/0x1160 kernel/workqueue.c:2267 #2: ffff888059019538 (&idev->mc_lock){+.+.}-{3:3}, at: mld_ifc_work+0x29/0xb40 net/ipv6/mcast.c:2658 #3: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #3: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #3: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: mld_sendpack+0x1f7/0xe80 net/ipv6/mcast.c:1798 #4: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #4: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #4: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: ip6_finish_output2+0x593/0x1590 net/ipv6/ip6_output.c:123 #5: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:843 [inline] #5: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x26f/0x3760 net/core/dev.c:4257 #6: ffff888028a5c258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:361 [inline] #6: ffff888028a5c258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: qdisc_run_begin include/net/sch_generic.h:195 [inline] #6: ffff888028a5c258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3882 [inline] #6: ffff888028a5c258 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock){+...}-{2:2}, at: __dev_queue_xmit+0x129a/0x3760 net/core/dev.c:4300 #7: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #7: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #7: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: ip6_finish_output2+0x593/0x1590 net/ipv6/ip6_output.c:123 #8: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #8: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:843 [inline] #8: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x26f/0x3760 net/core/dev.c:4257 #9: ffff8880304c87f0 (k-slock-AF_INET6){+...}-{2:2}, at: spin_trylock include/linux/spinlock.h:361 [inline] #9: ffff8880304c87f0 (k-slock-AF_INET6){+...}-{2:2}, at: icmpv6_xmit_lock net/ipv6/icmp.c:108 [inline] #9: ffff8880304c87f0 (k-slock-AF_INET6){+...}-{2:2}, at: icmp6_send+0xb5f/0x18d0 net/ipv6/icmp.c:553 #10: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #10: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: icmp6_send+0xaa6/0x18d0 net/ipv6/icmp.c:544 #11: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #11: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #11: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: ip6_send_skb+0x10b/0x380 net/ipv6/ip6_output.c:2008 #12: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline] #12: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline] #12: ffffffff8cb2ae20 (rcu_read_lock){....}-{1:2}, at: ip6_finish_output2+0x593/0x1590 net/ipv6/ip6_output.c:123 #13: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #13: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_read_lock_bh include/linux/rcupdate.h:843 [inline] #13: ffffffff8cb2ae80 (rcu_read_lock_bh){....}-{1:2}, at: __dev_queue_xmit+0x26f/0x3760 net/core/dev.c:4257 stack backtrace: CPU: 1 PID: 4270 Comm: kworker/1:3 Not tainted 6.1.146-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Workqueue: mld mld_ifc_work Call Trace: dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106 __lock_acquire+0x122f/0x7c50 kernel/locking/lockdep.c:-1 lock_acquire+0x1b4/0x490 kernel/locking/lockdep.c:5662 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __dev_xmit_skb net/core/dev.c:3925 [inline] __dev_queue_xmit+0x208f/0x3760 net/core/dev.c:4300 neigh_output include/net/neighbour.h:544 [inline] ip6_finish_output2+0xda2/0x1590 net/ipv6/ip6_output.c:138 ip6_send_skb+0x1d1/0x380 net/ipv6/ip6_output.c:2009 icmp6_send+0x1292/0x18d0 net/ipv6/icmp.c:632 __icmpv6_send include/linux/icmpv6.h:28 [inline] icmpv6_send include/linux/icmpv6.h:49 [inline] ip6_link_failure+0x37/0x4c0 net/ipv6/route.c:2827 dst_link_failure include/net/dst.h:423 [inline] ipip6_tunnel_xmit net/ipv6/sit.c:1039 [inline] sit_tunnel_xmit+0xaf0/0x1f60 net/ipv6/sit.c:1076 __netdev_start_xmit include/linux/netdevice.h:4896 [inline] netdev_start_xmit include/linux/netdevice.h:4910 [inline] xmit_one net/core/dev.c:3658 [inline] dev_hard_start_xmit+0x262/0x870 net/core/dev.c:3674 sch_direct_xmit+0x24e/0x4a0 net/sched/sch_generic.c:342 __dev_xmit_skb net/core/dev.c:3941 [inline] __dev_queue_xmit+0x1aa3/0x3760 net/core/dev.c:4300 neigh_output include/net/neighbour.h:544 [inline] ip6_finish_output2+0xda2/0x1590 net/ipv6/ip6_output.c:138 ip6tunnel_xmit+0x1a6/0x3a0 include/net/ip6_tunnel.h:161 ip6_tnl_xmit+0x225b/0x2ab0 net/ipv6/ip6_tunnel.c:1280 __gre6_xmit+0x960/0xc70 net/ipv6/ip6_gre.c:809 ip6gre_xmit_ipv6 net/ipv6/ip6_gre.c:865 [inline] ip6gre_tunnel_xmit+0xf76/0x13d0 net/ipv6/ip6_gre.c:937 __netdev_start_xmit include/linux/netdevice.h:4896 [inline] netdev_start_xmit include/linux/netdevice.h:4910 [inline] xmit_one net/core/dev.c:3658 [inline] dev_hard_start_xmit+0x262/0x870 net/core/dev.c:3674 sch_direct_xmit+0x24e/0x4a0 net/sched/sch_generic.c:342 __dev_xmit_skb net/core/dev.c:3895 [inline] __dev_queue_xmit+0x18cd/0x3760 net/core/dev.c:4300 neigh_output include/net/neighbour.h:544 [inline] ip6_finish_output2+0xda2/0x1590 net/ipv6/ip6_output.c:138 dst_output include/net/dst.h:453 [inline] NF_HOOK+0x15d/0x460 include/linux/netfilter.h:302 mld_sendpack+0x893/0xe80 net/ipv6/mcast.c:1826 mld_send_cr net/ipv6/mcast.c:2127 [inline] mld_ifc_work+0x836/0xb40 net/ipv6/mcast.c:2659 process_one_work+0x898/0x1160 kernel/workqueue.c:2292 worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439 kthread+0x29d/0x330 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295