====================================================== WARNING: possible circular locking dependency detected 6.16.0-rc6-syzkaller-00145-g14822f782700 #0 Not tainted ------------------------------------------------------ kworker/u8:10/11635 is trying to acquire lock: ffff888064a27218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888064a27218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{3:3}, at: __dev_xmit_skb net/core/dev.c:4136 [inline] ffff888064a27218 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{3:3}, at: __dev_queue_xmit+0x2228/0x3a70 net/core/dev.c:4679 but task is already holding lock: ffff888026e87558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff888026e87558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4651 [inline] ffff888026e87558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x153/0x4b0 net/sched/sch_generic.c:342 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}: lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __netif_tx_lock include/linux/netdevice.h:4651 [inline] sch_direct_xmit+0x153/0x4b0 net/sched/sch_generic.c:342 __dev_xmit_skb net/core/dev.c:4102 [inline] __dev_queue_xmit+0x17b6/0x3a70 net/core/dev.c:4679 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0x11fb/0x16a0 net/ipv6/ip6_output.c:141 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:317 mld_sendpack+0x800/0xd80 net/ipv6/mcast.c:1868 mld_send_cr net/ipv6/mcast.c:2169 [inline] mld_ifc_work+0x835/0xde0 net/ipv6/mcast.c:2702 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 -> #0 (dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2){+...}-{3:3}: check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __dev_xmit_skb net/core/dev.c:4136 [inline] __dev_queue_xmit+0x2228/0x3a70 net/core/dev.c:4679 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0x11fb/0x16a0 net/ipv6/ip6_output.c:141 ip6_send_skb+0x1d5/0x390 net/ipv6/ip6_output.c:1982 icmp6_send+0x12c6/0x1940 net/ipv6/icmp.c:632 __icmpv6_send include/linux/icmpv6.h:28 [inline] icmpv6_send include/linux/icmpv6.h:49 [inline] ip6_link_failure+0x3b/0x4c0 net/ipv6/route.c:2843 ip_tunnel_xmit+0x175b/0x2380 net/ipv4/ip_tunnel.c:865 __gre_xmit+0x19a/0x240 net/ipv4/ip_gre.c:488 erspan_xmit+0xa04/0x1220 net/ipv4/ip_gre.c:747 __netdev_start_xmit include/linux/netdevice.h:5215 [inline] netdev_start_xmit include/linux/netdevice.h:5224 [inline] xmit_one net/core/dev.c:3830 [inline] dev_hard_start_xmit+0x2d4/0x830 net/core/dev.c:3846 sch_direct_xmit+0x241/0x4b0 net/sched/sch_generic.c:344 qdisc_restart net/sched/sch_generic.c:409 [inline] __qdisc_run+0xb16/0x15f0 net/sched/sch_generic.c:417 __dev_xmit_skb net/core/dev.c:4171 [inline] __dev_queue_xmit+0xfe1/0x3a70 net/core/dev.c:4679 dev_queue_xmit include/linux/netdevice.h:3355 [inline] neigh_hh_output include/net/neighbour.h:523 [inline] neigh_output include/net/neighbour.h:537 [inline] ip6_finish_output2+0x11bc/0x16a0 net/ipv6/ip6_output.c:141 ip6tunnel_xmit include/net/ip6_tunnel.h:161 [inline] udp_tunnel6_xmit_skb+0x5da/0xa60 net/ipv6/ip6_udp_tunnel.c:111 send6+0x5aa/0x8d0 drivers/net/wireguard/socket.c:152 wg_socket_send_skb_to_peer+0x111/0x1d0 drivers/net/wireguard/socket.c:178 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline] wg_packet_handshake_send_worker+0x1db/0x320 drivers/net/wireguard/send.c:51 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 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(&qdisc_xmit_lock_key#4); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2); lock(&qdisc_xmit_lock_key#4); lock(dev->qdisc_tx_busylock ?: &qdisc_tx_busylock#2); *** DEADLOCK *** 12 locks held by kworker/u8:10/11635: #0: ffff888031f0d148 ((wq_completion)wg-kex-wg2){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline] #0: ffff888031f0d148 ((wq_completion)wg-kex-wg2){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3321 #1: ffffc9001aae7bc0 ((work_completion)(&peer->transmit_handshake_work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline] #1: ffffc9001aae7bc0 ((work_completion)(&peer->transmit_handshake_work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3321 #2: ffff888059c4bce8 (&peer->endpoint_lock){++-.}-{3:3}, at: wg_socket_send_skb_to_peer+0x54/0x1d0 drivers/net/wireguard/socket.c:173 #3: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #3: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:892 [inline] #3: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: send6+0x220/0x8d0 drivers/net/wireguard/socket.c:118 #4: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #4: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #4: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: ip6_finish_output2+0x701/0x16a0 net/ipv6/ip6_output.c:126 #5: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #5: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:892 [inline] #5: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27e/0x3a70 net/core/dev.c:4638 #6: ffff888026e87558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: spin_lock include/linux/spinlock.h:351 [inline] #6: ffff888026e87558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4651 [inline] #6: ffff888026e87558 (&qdisc_xmit_lock_key#4){+.-.}-{3:3}, at: sch_direct_xmit+0x153/0x4b0 net/sched/sch_generic.c:342 #7: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #7: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #7: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: icmp6_send+0x1e9/0x1940 net/ipv6/icmp.c:477 #8: ffff8880304d01d8 (k-slock-AF_INET6){+.-.}-{3:3}, at: spin_trylock include/linux/spinlock.h:361 [inline] #8: ffff8880304d01d8 (k-slock-AF_INET6){+.-.}-{3:3}, at: icmpv6_xmit_lock net/ipv6/icmp.c:108 [inline] #8: ffff8880304d01d8 (k-slock-AF_INET6){+.-.}-{3:3}, at: icmp6_send+0xc5c/0x1940 net/ipv6/icmp.c:554 #9: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #9: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #9: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: ip6_send_skb+0x10f/0x390 net/ipv6/ip6_output.c:1981 #10: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline] #10: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline] #10: ffffffff8e13f0e0 (rcu_read_lock){....}-{1:3}, at: ip6_finish_output2+0x701/0x16a0 net/ipv6/ip6_output.c:126 #11: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #11: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:892 [inline] #11: ffffffff8e13f140 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x27e/0x3a70 net/core/dev.c:4638 stack backtrace: CPU: 0 UID: 0 PID: 11635 Comm: kworker/u8:10 Not tainted 6.16.0-rc6-syzkaller-00145-g14822f782700 #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 Workqueue: wg-kex-wg2 wg_packet_handshake_send_worker Call Trace: dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120 print_circular_bug+0x2ee/0x310 kernel/locking/lockdep.c:2046 check_noncircular+0x134/0x160 kernel/locking/lockdep.c:2178 check_prev_add kernel/locking/lockdep.c:3168 [inline] check_prevs_add kernel/locking/lockdep.c:3287 [inline] validate_chain+0xb9b/0x2140 kernel/locking/lockdep.c:3911 __lock_acquire+0xab9/0xd20 kernel/locking/lockdep.c:5240 lock_acquire+0x120/0x360 kernel/locking/lockdep.c:5871 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] __dev_xmit_skb net/core/dev.c:4136 [inline] __dev_queue_xmit+0x2228/0x3a70 net/core/dev.c:4679 neigh_output include/net/neighbour.h:539 [inline] ip6_finish_output2+0x11fb/0x16a0 net/ipv6/ip6_output.c:141 ip6_send_skb+0x1d5/0x390 net/ipv6/ip6_output.c:1982 icmp6_send+0x12c6/0x1940 net/ipv6/icmp.c:632 __icmpv6_send include/linux/icmpv6.h:28 [inline] icmpv6_send include/linux/icmpv6.h:49 [inline] ip6_link_failure+0x3b/0x4c0 net/ipv6/route.c:2843 ip_tunnel_xmit+0x175b/0x2380 net/ipv4/ip_tunnel.c:865 __gre_xmit+0x19a/0x240 net/ipv4/ip_gre.c:488 erspan_xmit+0xa04/0x1220 net/ipv4/ip_gre.c:747 __netdev_start_xmit include/linux/netdevice.h:5215 [inline] netdev_start_xmit include/linux/netdevice.h:5224 [inline] xmit_one net/core/dev.c:3830 [inline] dev_hard_start_xmit+0x2d4/0x830 net/core/dev.c:3846 sch_direct_xmit+0x241/0x4b0 net/sched/sch_generic.c:344 qdisc_restart net/sched/sch_generic.c:409 [inline] __qdisc_run+0xb16/0x15f0 net/sched/sch_generic.c:417 __dev_xmit_skb net/core/dev.c:4171 [inline] __dev_queue_xmit+0xfe1/0x3a70 net/core/dev.c:4679 dev_queue_xmit include/linux/netdevice.h:3355 [inline] neigh_hh_output include/net/neighbour.h:523 [inline] neigh_output include/net/neighbour.h:537 [inline] ip6_finish_output2+0x11bc/0x16a0 net/ipv6/ip6_output.c:141 ip6tunnel_xmit include/net/ip6_tunnel.h:161 [inline] udp_tunnel6_xmit_skb+0x5da/0xa60 net/ipv6/ip6_udp_tunnel.c:111 send6+0x5aa/0x8d0 drivers/net/wireguard/socket.c:152 wg_socket_send_skb_to_peer+0x111/0x1d0 drivers/net/wireguard/socket.c:178 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline] wg_packet_handshake_send_worker+0x1db/0x320 drivers/net/wireguard/send.c:51 process_one_work kernel/workqueue.c:3238 [inline] process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3321 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3402 kthread+0x70e/0x8a0 kernel/kthread.c:464 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245