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BUG: KASAN: use-after-free in l2cap_chan_close+0x4fb/0x770 net/bluetooth/l2cap_core.c:727
Read of size 1 at addr ffff88809860f320 by task kworker/1:0/18

CPU: 1 PID: 18 Comm: kworker/1:0 Not tainted 4.14.191-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:17 [inline]
 dump_stack+0x1b2/0x283 lib/dump_stack.c:58
 print_address_description.cold+0x54/0x1d3 mm/kasan/report.c:252
 kasan_report_error.cold+0x8a/0x194 mm/kasan/report.c:351
 kasan_report mm/kasan/report.c:409 [inline]
 __asan_report_load1_noabort+0x68/0x70 mm/kasan/report.c:427
 l2cap_chan_close+0x4fb/0x770 net/bluetooth/l2cap_core.c:727
 do_enable_set+0x473/0x8a0 net/bluetooth/6lowpan.c:1086
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Allocated by task 3348:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x131/0x3d0 mm/slab.c:3618
 kmalloc include/linux/slab.h:488 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 l2cap_chan_create+0x3e/0x3c0 net/bluetooth/l2cap_core.c:441
 chan_create net/bluetooth/6lowpan.c:652 [inline]
 bt_6lowpan_listen net/bluetooth/6lowpan.c:971 [inline]
 do_enable_set+0x4ac/0x8a0 net/bluetooth/6lowpan.c:1090
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

Freed by task 3348:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xc3/0x1a0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3496 [inline]
 kfree+0xc9/0x250 mm/slab.c:3815
 l2cap_chan_destroy net/bluetooth/l2cap_core.c:479 [inline]
 kref_put include/linux/kref.h:70 [inline]
 l2cap_chan_put+0x152/0x1b0 net/bluetooth/l2cap_core.c:493
 do_enable_set+0x47f/0x8a0 net/bluetooth/6lowpan.c:1087
 process_one_work+0x793/0x14a0 kernel/workqueue.c:2116
 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2250
 kthread+0x30d/0x420 kernel/kthread.c:232
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

The buggy address belongs to the object at ffff88809860f300
 which belongs to the cache kmalloc-2048 of size 2048
The buggy address is located 32 bytes inside of
 2048-byte region [ffff88809860f300, ffff88809860fb00)
The buggy address belongs to the page:
page:ffffea0002618380 count:1 mapcount:0 mapping:ffff88809860e200 index:0x0 compound_mapcount: 0
flags: 0xfffe0000008100(slab|head)
raw: 00fffe0000008100 ffff88809860e200 0000000000000000 0000000100000003
raw: ffffea000234ec20 ffffea0002618220 ffff88812fe52c40 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809860f200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809860f280: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88809860f300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff88809860f380: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809860f400: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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