Hi

When using Healer to fuzz the Linux kernel, UBSAN reported a
shift-out-of-bounds bug in net/sched/sch_api.c:580:10.

Here are the details:
commit:   89698becf06d341a700913c3d89ce2a914af69a2
version:   Linux 5.12
git tree:    upstream
kernel config, reproduction program can be found in the attached file.

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UBSAN: shift-out-of-bounds in net/sched/sch_api.c:580:10
shift exponent 247 is too large for 32-bit type 'int'
CPU: 1 PID: 3176 Comm: kworker/1:2 Not tainted 5.12.0-rc7+ #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS
rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
Workqueue: ipv6_addrconf addrconf_dad_work
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0xfa/0x151 lib/dump_stack.c:120
 ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
 __ubsan_handle_shift_out_of_bounds.cold+0xb1/0x20c lib/ubsan.c:327
 __qdisc_calculate_pkt_len.cold+0x1b/0xcf net/sched/sch_api.c:580
 qdisc_calculate_pkt_len include/net/sch_generic.h:787 [inline]
 __dev_xmit_skb net/core/dev.c:3803 [inline]
 __dev_queue_xmit+0x13b2/0x3020 net/core/dev.c:4162
 neigh_hh_output include/net/neighbour.h:499 [inline]
 neigh_output include/net/neighbour.h:508 [inline]
 ip_finish_output2+0xf20/0x2240 net/ipv4/ip_output.c:230
 __ip_finish_output net/ipv4/ip_output.c:308 [inline]
 __ip_finish_output+0x699/0xe20 net/ipv4/ip_output.c:290
 ip_finish_output+0x35/0x200 net/ipv4/ip_output.c:318
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip_output+0x201/0x610 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:448 [inline]
 ip_local_out+0xaf/0x1a0 net/ipv4/ip_output.c:126
 iptunnel_xmit+0x618/0x9f0 net/ipv4/ip_tunnel_core.c:82
 geneve_xmit_skb drivers/net/geneve.c:967 [inline]
 geneve_xmit+0xea7/0x41b0 drivers/net/geneve.c:1075
 __netdev_start_xmit include/linux/netdevice.h:4825 [inline]
 netdev_start_xmit include/linux/netdevice.h:4839 [inline]
 xmit_one net/core/dev.c:3605 [inline]
 dev_hard_start_xmit+0x1ff/0x940 net/core/dev.c:3621
 __dev_queue_xmit+0x2699/0x3020 net/core/dev.c:4194
 neigh_resolve_output net/core/neighbour.c:1491 [inline]
 neigh_resolve_output+0x4ee/0x810 net/core/neighbour.c:1471
 neigh_output include/net/neighbour.h:510 [inline]
 ip6_finish_output2+0xd09/0x21f0 net/ipv6/ip6_output.c:117
 __ip6_finish_output+0x4bb/0xe10 net/ipv6/ip6_output.c:182
 ip6_finish_output+0x35/0x200 net/ipv6/ip6_output.c:192
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip6_output+0x242/0x810 net/ipv6/ip6_output.c:215
 dst_output include/net/dst.h:448 [inline]
 NF_HOOK include/linux/netfilter.h:301 [inline]
 ndisc_send_skb+0xf52/0x14c0 net/ipv6/ndisc.c:508
 ndisc_send_ns+0x3a9/0x840 net/ipv6/ndisc.c:650
 addrconf_dad_work+0xd29/0x1380 net/ipv6/addrconf.c:4119
 process_one_work+0x9ad/0x1620 kernel/workqueue.c:2275
 worker_thread+0x96/0xe20 kernel/workqueue.c:2421
 kthread+0x374/0x490 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
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