=============================
WARNING: suspicious RCU usage
5.15.174-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
7 locks held by ksoftirqd/1/20:
 #0: ffff80001bdb7a00 ((&peer->hb_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline]
 #0: ffff80001bdb7a00 ((&peer->hb_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd0/0x8f0 kernel/time/timer.c:1441
 #1: ffff0000d38863a0 (slock-AF_INET6){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
 #1: ffff0000d38863a0 (slock-AF_INET6){+.-.}-{2:2}, at: sctp_generate_heartbeat_event+0x90/0x3dc net/sctp/sm_sideeffect.c:371
 #2: ffff800014d42360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311
 #3: ffff800014d423c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311
 #4: ffff800014d423c0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311
 #5: ffff0000dd1f6108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline]
 #5: ffff0000dd1f6108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3879 [inline]
 #5: ffff0000dd1f6108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0x8a0/0x2ac8 net/core/dev.c:4221
 #6: ffff800014d42360 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:311

stack backtrace:
CPU: 1 PID: 20 Comm: ksoftirqd/1 Not tainted 5.15.174-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
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+0x208/0x4a4 net/sched/sch_api.c:800
 pfifo_tail_enqueue+0x280/0x38c net/sched/sch_fifo.c:51
 qdisc_enqueue include/net/sch_generic.h:832 [inline]
 tbf_enqueue+0x2f0/0x620 net/sched/sch_tbf.c:243
 dev_qdisc_enqueue+0x60/0x35c net/core/dev.c:3820
 __dev_xmit_skb net/core/dev.c:3904 [inline]
 __dev_queue_xmit+0x1018/0x2ac8 net/core/dev.c:4221
 dev_queue_xmit+0x24/0x34 net/core/dev.c:4289
 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
 sctp_v4_xmit+0x430/0xb00 net/sctp/protocol.c:1071
 sctp_packet_transmit+0x1ec0/0x237c net/sctp/output.c:652
 sctp_outq_flush_transports net/sctp/outqueue.c:1170 [inline]
 sctp_outq_flush+0xf74/0x2e84 net/sctp/outqueue.c:1218
 sctp_outq_uncork+0x84/0xc0 net/sctp/outqueue.c:761
 sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline]
 sctp_do_sm+0x485c/0x4e80 net/sctp/sm_sideeffect.c:1170
 sctp_generate_heartbeat_event+0x2b4/0x3dc net/sctp/sm_sideeffect.c:391
 call_timer_fn+0x19c/0x8f0 kernel/time/timer.c:1451
 expire_timers kernel/time/timer.c:1496 [inline]
 __run_timers+0x554/0x718 kernel/time/timer.c:1767
 run_timer_softirq+0x7c/0x114 kernel/time/timer.c:1780
 handle_softirqs+0x384/0xdbc kernel/softirq.c:558
 run_ksoftirqd+0x6c/0x29c kernel/softirq.c:925
 smpboot_thread_fn+0x4b0/0x920 kernel/smpboot.c:164
 kthread+0x37c/0x45c kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:870