==================================================================
BUG: KASAN: use-after-free in qdisc_pkt_len_segs_init+0x7f8/0xa30
Read of size 2 at addr ffff8882123ab174 by task syz.2.4958/2755

CPU: 0 UID: 0 PID: 2755 Comm: syz.2.4958 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <IRQ>
 dump_stack_lvl+0xe8/0x150
 print_address_description+0x55/0x1e0
 print_report+0x58/0x70
 kasan_report+0x117/0x150
 qdisc_pkt_len_segs_init+0x7f8/0xa30
 __dev_queue_xmit+0x29a/0x3950
 br_dev_queue_push_xmit+0x370/0x4b0
 NF_HOOK+0x360/0x3f0
 br_forward_finish+0xd3/0x130
 NF_HOOK+0x360/0x3f0
 __br_forward+0x397/0x540
 br_handle_frame_finish+0x1521/0x1c80
 br_handle_frame+0x80f/0x1510
 __netif_receive_skb_core+0x98f/0x3170
 __netif_receive_skb_list_core+0x24d/0x810
 netif_receive_skb_list_internal+0x995/0xcf0
 napi_complete_done+0x299/0x730
 gro_cell_poll+0x5a9/0x5d0
 __napi_poll+0xae/0x340
 net_rx_action+0x627/0xf70
 handle_softirqs+0x22a/0x840
 do_softirq+0x76/0xd0
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0xf8/0x130
 tun_rx_batched+0x617/0x790
 tun_get_user+0x2bbc/0x43e0
 tun_chr_write_iter+0x113/0x200
 vfs_write+0x61d/0xb90
 ksys_write+0x150/0x270
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f32c379ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f32c4598028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f32c3a15fa0 RCX: 00007f32c379ce59
RDX: 000000000000fdef RSI: 00002000000002c0 RDI: 0000000000000007
RBP: 00007f32c3832d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f32c3a16038 R14: 00007f32c3a15fa0 R15: 00007ffe7d942ec8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x2123ab
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000000 ffffea000848eac8 ffffea000848eac8 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff8882123ab000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8882123ab080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8882123ab100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                                             ^
 ffff8882123ab180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8882123ab200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
