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BUG: KASAN: use-after-free in l2cap_chan_close+0x608/0x910 net/bluetooth/l2cap_core.c:727
Read of size 1 at addr ffff8880874109e0 by task kworker/0:2/3389

CPU: 0 PID: 3389 Comm: kworker/0:2 Not tainted 4.19.102-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+0x197/0x210 lib/dump_stack.c:118
 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_load1_noabort+0x14/0x20 mm/kasan/report.c:430
 l2cap_chan_close+0x608/0x910 net/bluetooth/l2cap_core.c:727
 do_enable_set+0x535/0x950 net/bluetooth/6lowpan.c:1086
 process_one_work+0x989/0x1750 kernel/workqueue.c:2153
 worker_thread+0x98/0xe40 kernel/workqueue.c:2296
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Allocated by task 3389:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc mm/kasan/kasan.c:553 [inline]
 kasan_kmalloc+0xce/0xf0 mm/kasan/kasan.c:531
 kmem_cache_alloc_trace+0x152/0x760 mm/slab.c:3625
 kmalloc include/linux/slab.h:515 [inline]
 kzalloc include/linux/slab.h:709 [inline]
 l2cap_chan_create+0x45/0x390 net/bluetooth/l2cap_core.c:441
 chan_create+0x10/0xe0 net/bluetooth/6lowpan.c:652
 bt_6lowpan_listen net/bluetooth/6lowpan.c:971 [inline]
 do_enable_set+0x579/0x950 net/bluetooth/6lowpan.c:1090
 process_one_work+0x989/0x1750 kernel/workqueue.c:2153
 worker_thread+0x98/0xe40 kernel/workqueue.c:2296
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Freed by task 8242:
 save_stack+0x45/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3503 [inline]
 kfree+0xcf/0x220 mm/slab.c:3822
 l2cap_chan_destroy+0x14f/0x1c0 net/bluetooth/l2cap_core.c:479
 kref_put include/linux/kref.h:70 [inline]
 l2cap_chan_put+0x3a/0x50 net/bluetooth/l2cap_core.c:493
 do_enable_set+0x541/0x950 net/bluetooth/6lowpan.c:1087
 process_one_work+0x989/0x1750 kernel/workqueue.c:2153
 worker_thread+0x98/0xe40 kernel/workqueue.c:2296
 kthread+0x354/0x420 kernel/kthread.c:246
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

The buggy address belongs to the object at ffff8880874109c0
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 32 bytes inside of
 2048-byte region [ffff8880874109c0, ffff8880874111c0)
The buggy address belongs to the page:
page:ffffea00021d0400 count:1 mapcount:0 mapping:ffff88812c31cc40 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffffea0002802e88 ffffea0002802288 ffff88812c31cc40
raw: 0000000000000000 ffff888087410140 0000000100000003 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888087410880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888087410900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888087410980: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
                                                       ^
 ffff888087410a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888087410a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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