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BUG: KASAN: use-after-free in batadv_interface_tx+0x1194/0x1880 net/batman-adv/soft-interface.c:226
Read of size 2 at addr ffff88808f269d0b by task syz-executor1/19212

CPU: 0 PID: 19212 Comm: syz-executor1 Not tainted 4.20.0+ #3
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1db/0x2d0 lib/dump_stack.c:113
 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report mm/kasan/report.c:412 [inline]
 kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:396
 __asan_report_load_n_noabort+0xf/0x20 mm/kasan/report.c:443
 batadv_interface_tx+0x1194/0x1880 net/batman-adv/soft-interface.c:226
 __netdev_start_xmit include/linux/netdevice.h:4382 [inline]
 netdev_start_xmit include/linux/netdevice.h:4391 [inline]
 dev_direct_xmit+0x368/0x670 net/core/dev.c:3930
 packet_direct_xmit+0xfb/0x170 net/packet/af_packet.c:246
 packet_snd net/packet/af_packet.c:2932 [inline]
 packet_sendmsg+0x2753/0x6830 net/packet/af_packet.c:2957
 sock_sendmsg_nosec net/socket.c:621 [inline]
 sock_sendmsg+0xdd/0x130 net/socket.c:631
 __sys_sendto+0x387/0x5f0 net/socket.c:1788
 __do_sys_sendto net/socket.c:1800 [inline]
 __se_sys_sendto net/socket.c:1796 [inline]
 __x64_sys_sendto+0xe1/0x1a0 net/socket.c:1796
 do_syscall_64+0x1a3/0x800 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457ec9
Code: 6d 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 3b b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fd765a2fc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 0000000000457ec9
RDX: 000000000000003d RSI: 00000000200001c0 RDI: 0000000000000003
RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fd765a306d4
R13: 00000000004c53f5 R14: 00000000004d8ef0 R15: 00000000ffffffff

The buggy address belongs to the page:
page:ffffea00023c9a40 count:0 mapcount:-128 mapping:0000000000000000 index:0x0
flags: 0x1fffc0000000000()
raw: 01fffc0000000000 ffffea000236aac8 ffffea00023cec08 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffff7f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808f269c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88808f269c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88808f269d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                      ^
 ffff88808f269d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88808f269e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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