============================= WARNING: suspicious RCU usage 5.15.180-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 swapper/0/0: #0: ffff800008007ba0 ((&peer->hb_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline] #0: ffff800008007ba0 ((&peer->hb_timer)){+.-.}-{0:0}, at: call_timer_fn+0xd0/0x8f0 kernel/time/timer.c:1441 #1: ffff0000d3a1daa0 (slock-AF_INET6){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #1: ffff0000d3a1daa0 (slock-AF_INET6){+.-.}-{2:2}, at: sctp_generate_heartbeat_event+0x98/0x3e4 net/sctp/sm_sideeffect.c:371 #2: ffff800014d51b60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311 #3: ffff800014d51bc0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311 #4: ffff800014d51bc0 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x18/0x54 include/linux/rcupdate.h:311 #5: ffff0000d2579108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #5: ffff0000d2579108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3910 [inline] #5: ffff0000d2579108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0x8a0/0x2ac8 net/core/dev.c:4252 #6: ffff800014d51b60 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:311 stack backtrace: CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.15.180-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 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+0x2e8/0x414 net/sched/sch_fifo.c:54 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:3851 __dev_xmit_skb net/core/dev.c:3935 [inline] __dev_queue_xmit+0x1018/0x2ac8 net/core/dev.c:4252 dev_queue_xmit+0x24/0x34 net/core/dev.c:4320 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 net/ipv4/ip_output.c:-1 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:452 [inline] ip_local_out net/ipv4/ip_output.c:126 [inline] __ip_queue_xmit+0xde8/0x190c net/ipv4/ip_output.c:532 sctp_v4_xmit+0x42c/0xcd4 net/sctp/protocol.c:1071 sctp_packet_transmit+0x1ec4/0x2380 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_cmd_interpreter net/sctp/sm_sideeffect.c:-1 [inline] 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+0x2bc/0x3e4 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 __do_softirq kernel/softirq.c:592 [inline] do_softirq_own_stack include/asm-generic/softirq_stack.h:10 [inline] invoke_softirq kernel/softirq.c:439 [inline] __irq_exit_rcu+0x268/0x4d8 kernel/softirq.c:641 irq_exit+0x14/0x88 kernel/softirq.c:665 handle_domain_irq+0x14c/0x1fc kernel/irq/irqdesc.c:711 gic_handle_irq+0x78/0x1c8 drivers/irqchip/irq-gic-v3.c:765 call_on_irq_stack+0x24/0x4c arch/arm64/kernel/entry.S:899 do_interrupt_handler+0x74/0x94 arch/arm64/kernel/entry-common.c:267 el1_interrupt+0x30/0x58 arch/arm64/kernel/entry-common.c:454 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:470 el1h_64_irq+0x78/0x7c arch/arm64/kernel/entry.S:522 arch_local_irq_enable+0xc/0x18 arch/arm64/include/asm/irqflags.h:35 default_idle_call+0xcc/0x4a8 kernel/sched/idle.c:112 cpuidle_idle_call kernel/sched/idle.c:194 [inline] do_idle+0x1d4/0x4dc kernel/sched/idle.c:306 cpu_startup_entry+0x24/0x28 kernel/sched/idle.c:403 rest_init+0x364/0x38c init/main.c:741 arch_call_rest_init+0x14/0x20 init/main.c:893 start_kernel+0x440/0x600 init/main.c:1140 __primary_switched+0xa8/0xb0 arch/arm64/kernel/head.S:468 vkms_vblank_simulate: vblank timer overrun