=============================
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
8 locks held by kworker/u4:7/4323:
 #0: ffff88801d488138 ((wq_completion)wg-kex-wg2#9){+.+.}-{0:0}, at: process_one_work+0x760/0x1000 kernel/workqueue.c:-1
 #1: ffffc90003dc7d00 ((work_completion)(&peer->transmit_handshake_work)){+.+.}-{0:0}, at: process_one_work+0x7a3/0x1000 kernel/workqueue.c:2285
 #2: ffff88806055f1f8 (&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: ffff88807b8fa908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
 #6: ffff88807b8fa908 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3911 [inline]
 #6: ffff88807b8fa908 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xb8a/0x2ed0 net/core/dev.c:4253
 #7: ffffffff8c11c360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311

stack backtrace:
CPU: 1 PID: 4323 Comm: kworker/u4:7 Not tainted 5.15.189-syzkaller #0
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:
 <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
 sfq_enqueue+0x1164/0x2260 net/sched/sch_sfq.c:471
 qdisc_enqueue include/net/sch_generic.h:832 [inline]
 tbf_enqueue+0x224/0x6e0 net/sched/sch_tbf.c:243
 dev_qdisc_enqueue+0x48/0x210 net/core/dev.c:3852
 __dev_xmit_skb net/core/dev.c:3936 [inline]
 __dev_queue_xmit+0xd7e/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
 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>