syzbot

rcu: INFO: rcu_preempt self-detected stall on CPU
rcu: 	1-....: (1 GPs behind) idle=a46/1/0x4000000000000002 softirq=57464/57470 fqs=5228 
rcu: 	 (t=10500 jiffies g=64585 q=2534)
NMI backtrace for cpu 1
CPU: 1 PID: 28525 Comm: syz-executor.5 Not tainted 4.19.71 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <IRQ>
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x172/0x1f0 lib/dump_stack.c:113
 nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
 nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_single_cpu_backtrace include/linux/nmi.h:164 [inline]
 rcu_dump_cpu_stacks+0x189/0x1d5 kernel/rcu/tree.c:1340
 print_cpu_stall kernel/rcu/tree.c:1478 [inline]
 check_cpu_stall kernel/rcu/tree.c:1550 [inline]
 __rcu_pending kernel/rcu/tree.c:3293 [inline]
 rcu_pending kernel/rcu/tree.c:3336 [inline]
 rcu_check_callbacks.cold+0x5e3/0xd90 kernel/rcu/tree.c:2682
 update_process_times+0x32/0x80 kernel/time/timer.c:1636
 tick_sched_handle+0xa2/0x190 kernel/time/tick-sched.c:164
 tick_sched_timer+0x47/0x130 kernel/time/tick-sched.c:1274
 __run_hrtimer kernel/time/hrtimer.c:1398 [inline]
 __hrtimer_run_queues+0x33b/0xdc0 kernel/time/hrtimer.c:1460
 hrtimer_interrupt+0x314/0x770 kernel/time/hrtimer.c:1518
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1067 [inline]
 smp_apic_timer_interrupt+0x111/0x550 arch/x86/kernel/apic/apic.c:1092
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:893
 </IRQ>
RIP: 0010:__read_once_size include/linux/compiler.h:193 [inline]
RIP: 0010:check_kcov_mode kernel/kcov.c:69 [inline]
RIP: 0010:__sanitizer_cov_trace_pc+0x20/0x50 kernel/kcov.c:101
Code: 90 90 90 90 90 90 90 90 90 90 55 48 89 e5 48 8b 75 08 65 48 8b 04 25 40 ee 01 00 65 8b 15 28 87 96 7e 81 e2 00 01 1f 00 75 2b <8b> 90 d0 12 00 00 83 fa 02 75 20 48 8b 88 d8 12 00 00 8b 80 d4 12
RSP: 0018:ffff8880aa3af048 EFLAGS: 00000246 ORIG_RAX: ffffffffffffff13
RAX: ffff88804ff745c0 RBX: ffff8880a05de778 RCX: ffffc900108c2000
RDX: 0000000000000000 RSI: ffffffff858e88bb RDI: ffff8880a05de780
RBP: ffff8880aa3af048 R08: ffff88804ff745c0 R09: 0000000000000005
R10: ffff88804ff74f08 R11: 000000000745693b R12: dffffc0000000000
R13: ffff8880a05de4c0 R14: ffff8880a05de800 R15: ffff8880a05de810
 hhf_dequeue+0x4eb/0xa00 net/sched/sch_hhf.c:427
 dequeue_skb net/sched/sch_generic.c:277 [inline]
 qdisc_restart net/sched/sch_generic.c:380 [inline]
 __qdisc_run+0x1e7/0x1960 net/sched/sch_generic.c:398
 __dev_xmit_skb net/core/dev.c:3501 [inline]
 __dev_queue_xmit+0x165c/0x2fe0 net/core/dev.c:3811
 dev_queue_xmit+0x18/0x20 net/core/dev.c:3876
 br_dev_queue_push_xmit+0x405/0x5d0 net/bridge/br_forward.c:56
 NF_HOOK include/linux/netfilter.h:289 [inline]
 NF_HOOK include/linux/netfilter.h:283 [inline]
 br_forward_finish+0xfa/0x400 net/bridge/br_forward.c:69
 NF_HOOK include/linux/netfilter.h:289 [inline]
 NF_HOOK include/linux/netfilter.h:283 [inline]
 __br_forward+0x647/0xb30 net/bridge/br_forward.c:113
 deliver_clone+0x61/0xc0 net/bridge/br_forward.c:129
 maybe_deliver net/bridge/br_forward.c:184 [inline]
 maybe_deliver net/bridge/br_forward.c:172 [inline]
 br_flood+0x4da/0x710 net/bridge/br_forward.c:226
 br_dev_xmit+0xe6f/0x1490 net/bridge/br_device.c:107
 __netdev_start_xmit include/linux/netdevice.h:4303 [inline]
 netdev_start_xmit include/linux/netdevice.h:4312 [inline]
 xmit_one net/core/dev.c:3257 [inline]
 dev_hard_start_xmit+0x1a5/0x980 net/core/dev.c:3273
 __dev_queue_xmit+0x2704/0x2fe0 net/core/dev.c:3843
 dev_queue_xmit+0x18/0x20 net/core/dev.c:3876
 pppoe_sendmsg+0x654/0x7e0 drivers/net/ppp/pppoe.c:904
 sock_sendmsg_nosec net/socket.c:622 [inline]
 sock_sendmsg+0xd7/0x130 net/socket.c:632
 ___sys_sendmsg+0x3e2/0x920 net/socket.c:2115
 __sys_sendmmsg+0x1bf/0x4e0 net/socket.c:2210
 __do_sys_sendmmsg net/socket.c:2239 [inline]
 __se_sys_sendmmsg net/socket.c:2236 [inline]
 __x64_sys_sendmmsg+0x9d/0x100 net/socket.c:2236
 do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4598e9
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe7f0683c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00000000004598e9
RDX: 000000000000033b RSI: 000000002000d180 RDI: 0000000000000005
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fe7f06846d4
R13: 00000000004c70a7 R14: 00000000004dc768 R15: 00000000ffffffff