KASAN: use-after-free Write in batadv_iv_ogm_schedule

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: c1141b3a Linux 4.14.166
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11e86359e00000
kernel config: https://syzkaller.appspot.com/x/.config?x=a99b4b74c4c01851
dashboard link: https://syzkaller.appspot.com/bug?extid=5b61e5e7ea0ff1aae244
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+5b61e5...@syzkaller.appspotmail.com

batman_adv: batadv0: Interface deactivated: batadv_slave_0
batman_adv: batadv0: Removing interface: batadv_slave_0
Unknown ioctl -1054845647
==================================================================
BUG: KASAN: use-after-free in batadv_iv_ogm_schedule+0xdc4/0xe20 net/batman-adv/bat_iv_ogm.c:951
Write of size 2 at addr ffff8880518bcc16 by task kworker/u4:3/276

CPU: 0 PID: 276 Comm: kworker/u4:3 Not tainted 4.14.166-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x142/0x197 lib/dump_stack.c:58
print_address_description.cold+0x7c/0x1dc mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report mm/kasan/report.c:409 [inline]
kasan_report.cold+0xa9/0x2af mm/kasan/report.c:393
__asan_report_store2_noabort+0x17/0x20 mm/kasan/report.c:433
batadv_iv_ogm_schedule+0xdc4/0xe20 net/batman-adv/bat_iv_ogm.c:951
batadv_iv_send_outstanding_bat_ogm_packet+0x4a1/0x680 net/batman-adv/bat_iv_ogm.c:1809
process_one_work+0x863/0x1600 kernel/workqueue.c:2114
worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
kthread+0x319/0x430 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 276:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_kmalloc mm/kasan/kasan.c:551 [inline]
kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:529
__do_kmalloc mm/slab.c:3720 [inline]
__kmalloc+0x15d/0x7a0 mm/slab.c:3729
kmalloc include/linux/slab.h:493 [inline]
batadv_tvlv_realloc_packet_buff net/batman-adv/tvlv.c:288 [inline]
batadv_tvlv_container_ogm_append+0x12b/0x480 net/batman-adv/tvlv.c:329
batadv_iv_ogm_schedule+0xba0/0xe20 net/batman-adv/bat_iv_ogm.c:945
batadv_iv_send_outstanding_bat_ogm_packet+0x4a1/0x680 net/batman-adv/bat_iv_ogm.c:1809
process_one_work+0x863/0x1600 kernel/workqueue.c:2114
worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
kthread+0x319/0x430 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Freed by task 5:
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x45/0xd0 mm/kasan/kasan.c:447
set_track mm/kasan/kasan.c:459 [inline]
kasan_slab_free+0x75/0xc0 mm/kasan/kasan.c:524
__cache_free mm/slab.c:3496 [inline]
kfree+0xcc/0x270 mm/slab.c:3815
batadv_iv_ogm_iface_disable+0x39/0x80 net/batman-adv/bat_iv_ogm.c:393
batadv_hardif_disable_interface.cold+0x605/0x840 net/batman-adv/hard-interface.c:836
batadv_softif_destroy_netlink+0xad/0x140 net/batman-adv/soft-interface.c:1134
default_device_exit_batch+0x22c/0x3d0 net/core/dev.c:8724
ops_exit_list.isra.0+0xfc/0x150 net/core/net_namespace.c:145
cleanup_net+0x3ba/0x870 net/core/net_namespace.c:484
process_one_work+0x863/0x1600 kernel/workqueue.c:2114
worker_thread+0x5d9/0x1050 kernel/workqueue.c:2248
kthread+0x319/0x430 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

The buggy address belongs to the object at ffff8880518bcc00
which belongs to the cache kmalloc-192 of size 192
The buggy address is located 22 bytes inside of
192-byte region [ffff8880518bcc00, ffff8880518bccc0)
The buggy address belongs to the page:
page:ffffea0001462f00 count:1 mapcount:0 mapping:ffff8880518bc000 index:0x0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffff8880518bc000 0000000000000000 0000000100000010
raw: ffffea000147d9a0 ffffea00029ec2a0 ffff8880aa800040 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880518bcb00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8880518bcb80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8880518bcc00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff8880518bcc80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
ffff8880518bcd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
overlayfs: filesystem on './file0' not supported as upperdir
Unknown ioctl -1054845647


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.