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BUG: KASAN: use-after-free in l2cap_chan_close+0x763/0xb10 net/bluetooth/l2cap_core.c:794
Read of size 1 at addr ffff88808ad32020 by task kworker/1:158/3242

CPU: 1 PID: 3242 Comm: kworker/1:158 Not tainted 5.7.0-rc1-next-20200415-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events do_enable_set
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x188/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xd3/0x315 mm/kasan/report.c:382
 __kasan_report.cold+0x35/0x4d mm/kasan/report.c:511
 kasan_report+0x33/0x50 mm/kasan/common.c:625
 l2cap_chan_close+0x763/0xb10 net/bluetooth/l2cap_core.c:794
 do_enable_set+0x4cf/0x8e0 net/bluetooth/6lowpan.c:1074
 process_one_work+0x965/0x16a0 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x388/0x470 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 2718:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc mm/kasan/common.c:495 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:468
 kmem_cache_alloc_trace+0x153/0x7d0 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 l2cap_chan_create+0x40/0x3a0 net/bluetooth/l2cap_core.c:450
 chan_create+0xc/0xd0 net/bluetooth/6lowpan.c:640
 bt_6lowpan_listen net/bluetooth/6lowpan.c:959 [inline]
 do_enable_set+0x511/0x8e0 net/bluetooth/6lowpan.c:1078
 process_one_work+0x965/0x16a0 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x388/0x470 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Freed by task 2728:
 save_stack+0x1b/0x40 mm/kasan/common.c:49
 set_track mm/kasan/common.c:57 [inline]
 kasan_set_free_info mm/kasan/common.c:317 [inline]
 __kasan_slab_free+0xf7/0x140 mm/kasan/common.c:456
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x109/0x2b0 mm/slab.c:3757
 l2cap_chan_destroy net/bluetooth/l2cap_core.c:488 [inline]
 kref_put include/linux/kref.h:65 [inline]
 l2cap_chan_put+0x1b2/0x230 net/bluetooth/l2cap_core.c:502
 do_enable_set+0x4db/0x8e0 net/bluetooth/6lowpan.c:1075
 process_one_work+0x965/0x16a0 kernel/workqueue.c:2268
 worker_thread+0x96/0xe20 kernel/workqueue.c:2414
 kthread+0x388/0x470 kernel/kthread.c:268
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff88808ad32000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 32 bytes inside of
 2048-byte region [ffff88808ad32000, ffff88808ad32800)
The buggy address belongs to the page:
page:ffffea00022b4c80 refcount:1 mapcount:0 mapping:00000000628e4504 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00024e7688 ffffea00022b4cc8 ffff8880aa000e00
raw: 0000000000000000 ffff88808ad32000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88808ad31f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88808ad31f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88808ad32000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff88808ad32080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88808ad32100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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