=============================
WARNING: suspicious RCU usage
5.15.189-syzkaller #0 Not tainted
-----------------------------
net/sched/sch_api.c:304 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
9 locks held by kworker/u4:1/144:
 #0: ffff88807340c138 ((wq_completion)wg-kex-wg1){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc9000175fd00 ((work_completion)(&peer->transmit_handshake_work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff888075f71d98 (&peer->endpoint_lock){++-.}-{2:2}, at: wg_socket_send_skb_to_peer+0x50/0x1c0 drivers/net/wireguard/socket.c:173
 #3: ffffffff8c11c3c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #4: ffffffff8c11c3c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #5: ffffffff8c11c3c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312
 #6: ffff8880226ed148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: neigh_hh_output include/net/neighbour.h:493 [inline]
 #6: ffff8880226ed148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: neigh_output include/net/neighbour.h:507 [inline]
 #6: ffff8880226ed148 (dev->qdisc_running_key ?: &qdisc_running_key){+...}-{0:0}, at: ip_finish_output2+0xc69/0x1080 net/ipv4/ip_output.c:228
 #7: ffff8880226ed108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
 #7: ffff8880226ed108 (&sch->q.lock){+.-.}-{2:2}, at: sch_direct_xmit+0x305/0x4a0 net/sched/sch_generic.c:354
 #8: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311

stack backtrace:
CPU: 0 PID: 144 Comm: kworker/u4:1 Not tainted 5.15.189-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: wg-kex-wg1 wg_packet_handshake_send_worker
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
 qdisc_lookup+0xa6/0x650 net/sched/sch_api.c:304
 qdisc_tree_reduce_backlog+0x190/0x430 net/sched/sch_api.c:793
 fq_codel_dequeue+0x28ee/0x2b30 net/sched/sch_fq_codel.c:321
 qdisc_peek_dequeued+0x6e/0x1f0 include/net/sch_generic.h:1115
 tbf_dequeue+0x7d/0xce0 net/sched/sch_tbf.c:265
 dequeue_skb net/sched/sch_generic.c:292 [inline]
 qdisc_restart net/sched/sch_generic.c:397 [inline]
 __qdisc_run+0x237/0x1480 net/sched/sch_generic.c:415
 __dev_xmit_skb net/core/dev.c:3942 [inline]
 __dev_queue_xmit+0xeb9/0x2ed0 net/core/dev.c:4253
 neigh_hh_output include/net/neighbour.h:493 [inline]
 neigh_output include/net/neighbour.h:507 [inline]
 ip_finish_output2+0xc69/0x1080 net/ipv4/ip_output.c:228
 ip_do_fragment+0x8ca/0x19e0 net/ipv4/ip_output.c:913
 iptunnel_xmit+0x525/0x960 net/ipv4/ip_tunnel_core.c:82
 udp_tunnel_xmit_skb+0x1b7/0x280 net/ipv4/udp_tunnel_core.c:175
 send4+0x96b/0xd90 drivers/net/wireguard/socket.c:85
 wg_socket_send_skb_to_peer+0xcd/0x1c0 drivers/net/wireguard/socket.c:175
 wg_packet_send_handshake_initiation drivers/net/wireguard/send.c:40 [inline]
 wg_packet_handshake_send_worker+0x1d8/0x310 drivers/net/wireguard/send.c:51
 process_one_work+0x863/0x1000 kernel/workqueue.c:2310
 worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
 kthread+0x436/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog
GRED: Unable to relocate VQ 0x0 after dequeue, screwing up backlog