============================= 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 10 locks held by kworker/0:3/4156: #0: ffff888017472138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2283 #1: ffffc90002e0fd20 ((work_completion)(&(&ssp->work)->work)){+.+.}-{0:0}, at: process_one_work+0x7d0/0x10c0 kernel/workqueue.c:2285 #2: ffff88802160d4e8 (&ssp->srcu_gp_mutex){+.+.}-{3:3}, at: srcu_advance_state kernel/rcu/srcutree.c:1177 [inline] #2: ffff88802160d4e8 (&ssp->srcu_gp_mutex){+.+.}-{3:3}, at: process_srcu+0x2f/0xc20 kernel/rcu/srcutree.c:1325 #3: ffffc90000007be0 ((&peer->hb_timer)){+.-.}-{0:0}, at: lockdep_copy_map include/linux/lockdep.h:45 [inline] #3: ffffc90000007be0 ((&peer->hb_timer)){+.-.}-{0:0}, at: call_timer_fn+0xbe/0x560 kernel/time/timer.c:1441 #4: ffff88802b3b2da0 (slock-AF_INET6){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #4: ffff88802b3b2da0 (slock-AF_INET6){+.-.}-{2:2}, at: sctp_generate_heartbeat_event+0x8c/0x450 net/sctp/sm_sideeffect.c:371 #5: ffffffff8cb1fd20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #6: ffffffff8cb1fd80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #7: ffffffff8cb1fd80 (rcu_read_lock_bh){....}-{1:2}, at: rcu_lock_acquire+0x9/0x30 include/linux/rcupdate.h:312 #8: ffff88807dd76108 (&sch->q.lock){+.-.}-{2:2}, at: spin_lock include/linux/spinlock.h:363 [inline] #8: ffff88807dd76108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_xmit_skb net/core/dev.c:3879 [inline] #8: ffff88807dd76108 (&sch->q.lock){+.-.}-{2:2}, at: __dev_queue_xmit+0xc1f/0x32b0 net/core/dev.c:4221 #9: ffffffff8cb1fd20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311 stack backtrace: CPU: 0 PID: 4156 Comm: kworker/0:3 Not tainted 5.15.174-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024 Workqueue: rcu_gp process_srcu Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106 qdisc_lookup+0xa8/0x630 net/sched/sch_api.c:304 qdisc_tree_reduce_backlog+0x212/0x4f0 net/sched/sch_api.c:800 pfifo_tail_enqueue+0x2ca/0x400 net/sched/sch_fifo.c:51 qdisc_enqueue include/net/sch_generic.h:832 [inline] tbf_enqueue+0x35d/0x6f0 net/sched/sch_tbf.c:243 dev_qdisc_enqueue+0x47/0x240 net/core/dev.c:3820 __dev_xmit_skb net/core/dev.c:3904 [inline] __dev_queue_xmit+0xe32/0x32b0 net/core/dev.c:4221 neigh_hh_output include/net/neighbour.h:493 [inline] neigh_output include/net/neighbour.h:507 [inline] ip_finish_output2+0xcd7/0x11a0 net/ipv4/ip_output.c:228 dst_output include/net/dst.h:443 [inline] ip_local_out net/ipv4/ip_output.c:126 [inline] __ip_queue_xmit+0x12df/0x1d90 net/ipv4/ip_output.c:532 sctp_packet_transmit+0x2565/0x2b70 net/sctp/output.c:652 sctp_outq_flush_transports net/sctp/outqueue.c:1170 [inline] sctp_outq_flush+0x13c7/0x3d70 net/sctp/outqueue.c:1218 sctp_side_effects net/sctp/sm_sideeffect.c:1199 [inline] sctp_do_sm+0x55e7/0x5c80 net/sctp/sm_sideeffect.c:1170 sctp_generate_heartbeat_event+0x321/0x450 net/sctp/sm_sideeffect.c:391 call_timer_fn+0x16d/0x560 kernel/time/timer.c:1451 expire_timers kernel/time/timer.c:1496 [inline] __run_timers+0x67c/0x890 kernel/time/timer.c:1767 run_timer_softirq+0x63/0xf0 kernel/time/timer.c:1780 handle_softirqs+0x3a7/0x930 kernel/softirq.c:558 __do_softirq kernel/softirq.c:592 [inline] invoke_softirq kernel/softirq.c:432 [inline] __irq_exit_rcu+0x157/0x240 kernel/softirq.c:641 irq_exit_rcu+0x5/0x20 kernel/softirq.c:653 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1108 [inline] sysvec_apic_timer_interrupt+0xa0/0xc0 arch/x86/kernel/apic/apic.c:1108 asm_sysvec_apic_timer_interrupt+0x16/0x20 arch/x86/include/asm/idtentry.h:676 RIP: 0010:should_resched arch/x86/include/asm/preempt.h:103 [inline] RIP: 0010:delay_tsc+0x52/0xd0 arch/x86/lib/delay.c:77 Code: 09 c3 0f 01 f9 66 90 48 89 d5 48 c1 e5 20 48 09 c5 48 29 dd 4c 39 f5 73 67 bf 01 00 00 00 e8 f5 e2 1b fd 65 8b 05 06 c6 c6 7b <85> c0 74 2f f3 90 bf 01 00 00 00 e8 5e e1 1b fd e8 b9 58 03 06 41 RSP: 0018:ffffc90002e0fae0 EFLAGS: 00000297 RAX: 0000000080000000 RBX: 0000004d0daa978e RCX: 0000000000000001 RDX: 000000000000004d RSI: ffffffff8af9efe0 RDI: 0000000000000001 RBP: 0000000000000854 R08: ffffffff84364b44 R09: fffff520005c1f2d R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000004 R13: 1ffffffff1c14c47 R14: 0000000000002af9 R15: 0000000000000000 try_check_zero+0x2f2/0x360 kernel/rcu/srcutree.c:702 srcu_advance_state kernel/rcu/srcutree.c:1227 [inline] process_srcu+0x1aa/0xc20 kernel/rcu/srcutree.c:1325 process_one_work+0x8a1/0x10c0 kernel/workqueue.c:2310 worker_thread+0xaca/0x1280 kernel/workqueue.c:2457 kthread+0x3f6/0x4f0 kernel/kthread.c:334 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287 ---------------- Code disassembly (best guess): 0: 09 c3 or %eax,%ebx 2: 0f 01 f9 rdtscp 5: 66 90 xchg %ax,%ax 7: 48 89 d5 mov %rdx,%rbp a: 48 c1 e5 20 shl $0x20,%rbp e: 48 09 c5 or %rax,%rbp 11: 48 29 dd sub %rbx,%rbp 14: 4c 39 f5 cmp %r14,%rbp 17: 73 67 jae 0x80 19: bf 01 00 00 00 mov $0x1,%edi 1e: e8 f5 e2 1b fd call 0xfd1be318 23: 65 8b 05 06 c6 c6 7b mov %gs:0x7bc6c606(%rip),%eax # 0x7bc6c630 * 2a: 85 c0 test %eax,%eax <-- trapping instruction 2c: 74 2f je 0x5d 2e: f3 90 pause 30: bf 01 00 00 00 mov $0x1,%edi 35: e8 5e e1 1b fd call 0xfd1be198 3a: e8 b9 58 03 06 call 0x60358f8 3f: 41 rex.B