=============================
WARNING: suspicious RCU usage
5.15.169-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
6 locks held by syz.4.362/5329:
 #0: ffff0000dc6c3120 (sk_lock-AF_INET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1678 [inline]
 #0: ffff0000dc6c3120 (sk_lock-AF_INET){+.+.}-{0:0}, at: tcp_sendmsg+0x30/0x64 net/ipv4/tcp.c:1456
 #1: ffff800014c822e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311
 #2: ffff800014c82340 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311
 #3: ffff800014c82340 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311
 #4: ffff0000dae18908 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
 #4: ffff0000dae18908 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3875 [inline]
 #4: ffff0000dae18908 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0x8a0/0x2ac8 net/core/dev.c:4217
 #5: ffff800014c822e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:311

stack backtrace:
CPU: 0 PID: 5329 Comm: syz.4.362 Not tainted 5.15.169-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call trace:
 dump_backtrace+0x0/0x530 arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x108/0x170 lib/dump_stack.c:106
 dump_stack+0x1c/0x58 lib/dump_stack.c:113
 lockdep_rcu_suspicious+0x188/0x1e0 kernel/locking/lockdep.c:6571
 qdisc_lookup+0xc8/0x64c net/sched/sch_api.c:304
 qdisc_tree_reduce_backlog+0x200/0x4e8 net/sched/sch_api.c:800
 cake_enqueue+0x1bb0/0x7930 net/sched/sch_cake.c:1775
 qdisc_enqueue include/net/sch_generic.h:832 [inline]
 tbf_enqueue+0x2f8/0x5f0 net/sched/sch_tbf.c:237
 dev_qdisc_enqueue+0x60/0x35c net/core/dev.c:3816
 __dev_xmit_skb net/core/dev.c:3900 [inline]
 __dev_queue_xmit+0x1018/0x2ac8 net/core/dev.c:4217
 dev_queue_xmit+0x24/0x34 net/core/dev.c:4285
 neigh_hh_output include/net/neighbour.h:493 [inline]
 neigh_output include/net/neighbour.h:507 [inline]
 ip_finish_output2+0xd3c/0x131c net/ipv4/ip_output.c:228
 __ip_finish_output+0x1b0/0x458
 ip_finish_output+0x40/0x218 net/ipv4/ip_output.c:316
 NF_HOOK_COND include/linux/netfilter.h:291 [inline]
 ip_output+0x330/0x49c net/ipv4/ip_output.c:430
 dst_output include/net/dst.h:443 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 __ip_queue_xmit+0xe90/0x1a04 net/ipv4/ip_output.c:532
 ip_queue_xmit+0x5c/0x78 net/ipv4/ip_output.c:546
 __tcp_transmit_skb+0x1944/0x31e8 net/ipv4/tcp_output.c:1402
 tcp_transmit_skb net/ipv4/tcp_output.c:1420 [inline]
 tcp_write_xmit+0x12bc/0x4dc0 net/ipv4/tcp_output.c:2705
 tcp_push_one+0xb4/0xfc net/ipv4/tcp_output.c:2904
 tcp_sendmsg_locked+0x1858/0x30a8 net/ipv4/tcp.c:1410
 tcp_sendmsg+0x40/0x64 net/ipv4/tcp.c:1457
 inet_sendmsg+0x15c/0x290 net/ipv4/af_inet.c:836
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 __sys_sendto+0x388/0x4d0 net/socket.c:2063
 __do_sys_sendto net/socket.c:2075 [inline]
 __se_sys_sendto net/socket.c:2071 [inline]
 __arm64_sys_sendto+0xd8/0xf8 net/socket.c:2071
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x58/0x14c arch/arm64/kernel/syscall.c:181
 el0_svc+0x7c/0x1f0 arch/arm64/kernel/entry-common.c:608
 el0t_64_sync_handler+0x84/0xe4 arch/arm64/kernel/entry-common.c:626
 el0t_64_sync+0x1a0/0x1a4 arch/arm64/kernel/entry.S:584