UBSAN: array-index-out-of-bounds in qfq_update_agg

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    3db1a3fa Merge tag 'staging-5.11-rc1' of git://git.kernel...
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1286be67500000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a6e6725884106332
dashboard link: https://syzkaller.appspot.com/bug?extid=7c315a573dd9374a3220
compiler:       gcc (GCC) 10.1.0-syz 20200507

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7c315a573dd9374a3220@xxxxxxxxxxxxxxxxxxxxxxxxx

================================================================================
UBSAN: array-index-out-of-bounds in net/sched/sch_qfq.c:300:24
index 29 is out of range for type 'qfq_group [25]'
CPU: 0 PID: 20516 Comm: syz-executor.3 Not tainted 5.10.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
 __ubsan_handle_out_of_bounds.cold+0x62/0x6c lib/ubsan.c:356
 qfq_update_agg+0x7b8/0x7d0 net/sched/sch_qfq.c:300
 qfq_add_to_agg+0x75/0x500 net/sched/sch_qfq.c:317
 qfq_change_class+0x5da/0x18f0 net/sched/sch_qfq.c:510
 tc_ctl_tclass+0x526/0xc70 net/sched/sch_api.c:2111
 rtnetlink_rcv_msg+0x493/0xb40 net/core/rtnetlink.c:5564
 netlink_rcv_skb+0x153/0x420 net/netlink/af_netlink.c:2494
 netlink_unicast_kernel net/netlink/af_netlink.c:1304 [inline]
 netlink_unicast+0x533/0x7d0 net/netlink/af_netlink.c:1330
 netlink_sendmsg+0x907/0xe10 net/netlink/af_netlink.c:1919
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg+0xd3/0x130 net/socket.c:672
 ____sys_sendmsg+0x6e8/0x810 net/socket.c:2336
 ___sys_sendmsg+0xf3/0x170 net/socket.c:2390
 __sys_sendmsg+0xe5/0x1b0 net/socket.c:2423
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x45e219
Code: 0d b4 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 db b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fe1c8c30c68 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 000000000045e219
RDX: 0000000000000000 RSI: 0000000020000540 RDI: 0000000000000003
RBP: 000000000119c068 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000119c034
R13: 00007ffc62cfe08f R14: 00007fe1c8c319c0 R15: 000000000119c034
================================================================================


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