============================================ WARNING: possible recursive locking detected syzkaller #0 Not tainted -------------------------------------------- kworker/0:14/10766 is trying to acquire lock: ffff888078375558 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] ffff888078375558 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4780 [inline] ffff888078375558 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: sch_direct_xmit+0x15f/0x4c0 net/sched/sch_generic.c:370 but task is already holding lock: ffff8880445d0d58 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] ffff8880445d0d58 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4780 [inline] ffff8880445d0d58 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: sch_direct_xmit+0x15f/0x4c0 net/sched/sch_generic.c:370 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&qdisc_xmit_lock_key#3); lock(&qdisc_xmit_lock_key#3); *** DEADLOCK *** May be due to missing lock nesting notation 15 locks held by kworker/0:14/10766: #0: ffff888030fff940 ((wq_completion)mld){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3277 [inline] #0: ffff888030fff940 ((wq_completion)mld){+.+.}-{0:0}, at: process_scheduled_works+0xa35/0x1860 kernel/workqueue.c:3385 #1: ffffc90003667c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3278 [inline] #1: ffffc90003667c40 ((work_completion)(&(&idev->mc_ifc_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0xa70/0x1860 kernel/workqueue.c:3385 #2: ffff888076c72530 (&idev->mc_lock){+.+.}-{4:4}, at: mld_ifc_work+0x2d/0xe70 net/ipv6/mcast.c:2679 #3: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #3: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #3: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: mld_sendpack+0x213/0xe40 net/ipv6/mcast.c:1814 #4: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #4: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #4: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: ip6_output+0x126/0x550 net/ipv6/ip6_output.c:234 #5: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline] #5: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x2b6/0x3950 net/core/dev.c:4791 #6: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #6: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #6: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: bond_start_xmit+0xb4/0x1900 drivers/net/bonding/bond_main.c:5591 #7: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #7: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline] #7: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x2b6/0x3950 net/core/dev.c:4791 #8: ffff888052704228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: spin_trylock include/linux/spinlock.h:354 [inline] #8: ffff888052704228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: qdisc_run_begin include/net/sch_generic.h:205 [inline] #8: ffff888052704228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4196 [inline] #8: ffff888052704228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_queue_xmit+0x11a6/0x3950 net/core/dev.c:4831 #9: ffff8880445d0d58 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] #9: ffff8880445d0d58 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4780 [inline] #9: ffff8880445d0d58 (&qdisc_xmit_lock_key#3){+.-.}-{3:3}, at: sch_direct_xmit+0x15f/0x4c0 net/sched/sch_generic.c:370 #10: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #10: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #10: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: ip_output+0x5b/0x450 net/ipv4/ip_output.c:433 #11: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #11: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #11: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: ip_finish_output2+0x3c2/0x1070 net/ipv4/ip_output.c:230 #12: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline] #12: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline] #12: ffffffff8e95cd60 (rcu_read_lock){....}-{1:3}, at: arp_xmit+0x23/0x270 net/ipv4/arp.c:663 #13: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #13: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline] #13: ffffffff8e95cdc0 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x2b6/0x3950 net/core/dev.c:4791 #14: ffff88804f11b228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: spin_trylock include/linux/spinlock.h:354 [inline] #14: ffff88804f11b228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: qdisc_run_begin include/net/sch_generic.h:205 [inline] #14: ffff88804f11b228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4196 [inline] #14: ffff88804f11b228 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#5){+...}-{3:3}, at: __dev_queue_xmit+0x11a6/0x3950 net/core/dev.c:4831 stack backtrace: CPU: 0 UID: 0 PID: 10766 Comm: kworker/0:14 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_deadlock_bug+0x279/0x290 kernel/locking/lockdep.c:3041 check_deadlock kernel/locking/lockdep.c:3093 [inline] validate_chain kernel/locking/lockdep.c:3895 [inline] __lock_acquire+0x253f/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] __netif_tx_lock include/linux/netdevice.h:4780 [inline] sch_direct_xmit+0x15f/0x4c0 net/sched/sch_generic.c:370 __dev_xmit_skb net/core/dev.c:4209 [inline] __dev_queue_xmit+0x180f/0x3950 net/core/dev.c:4831 NF_HOOK+0x33a/0x3c0 include/linux/netfilter.h:-1 arp_xmit+0x16c/0x270 net/ipv4/arp.c:665 arp_solicit+0xbe0/0xe40 net/ipv4/arp.c:392 neigh_probe net/core/neighbour.c:1096 [inline] __neigh_event_send+0xf05/0x14d0 net/core/neighbour.c:1276 neigh_event_send_probe include/net/neighbour.h:480 [inline] neigh_event_send include/net/neighbour.h:486 [inline] neigh_resolve_output+0x198/0x750 net/core/neighbour.c:1603 neigh_output include/net/neighbour.h:556 [inline] ip_finish_output2+0xca9/0x1070 net/ipv4/ip_output.c:237 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip_output+0x29f/0x450 net/ipv4/ip_output.c:438 iptunnel_xmit+0x621/0xd10 net/ipv4/ip_tunnel_core.c:97 ip_tunnel_xmit+0x193a/0x1f20 net/ipv4/ip_tunnel.c:845 __gre_xmit+0x19e/0x240 net/ipv4/ip_gre.c:491 erspan_xmit+0xa41/0x14d0 net/ipv4/ip_gre.c:750 __netdev_start_xmit include/linux/netdevice.h:5367 [inline] netdev_start_xmit include/linux/netdevice.h:5376 [inline] xmit_one net/core/dev.c:3888 [inline] dev_hard_start_xmit+0x2cd/0x830 net/core/dev.c:3904 sch_direct_xmit+0x251/0x4c0 net/sched/sch_generic.c:372 __dev_xmit_skb net/core/dev.c:4209 [inline] __dev_queue_xmit+0x180f/0x3950 net/core/dev.c:4831 __bond_start_xmit drivers/net/bonding/bond_main.c:5571 [inline] bond_start_xmit+0x766/0x1900 drivers/net/bonding/bond_main.c:5593 __netdev_start_xmit include/linux/netdevice.h:5367 [inline] netdev_start_xmit include/linux/netdevice.h:5376 [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:1842 mld_send_cr net/ipv6/mcast.c:2141 [inline] mld_ifc_work+0x835/0xe70 net/ipv6/mcast.c:2680 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