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BUG: KASAN: use-after-free in l2cap_chan_close+0x661/0xa10 net/bluetooth/l2cap_core.c:734
Read of size 1 at addr ffff88809e4a4020 by task kworker/0:76/3186

CPU: 0 PID: 3186 Comm: kworker/0:76 Not tainted 5.6.0-rc3-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.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x32 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:641
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 l2cap_chan_close+0x661/0xa10 net/bluetooth/l2cap_core.c:734
 do_enable_set+0x53f/0x960 net/bluetooth/6lowpan.c:1074
 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2264
 worker_thread+0x98/0xe40 kernel/workqueue.c:2410
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Allocated by task 3002:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 __kasan_kmalloc mm/kasan/common.c:515 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:488
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:529
 kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 l2cap_chan_create+0x45/0x3a0 net/bluetooth/l2cap_core.c:446
 chan_create+0x10/0xe0 net/bluetooth/6lowpan.c:640
 bt_6lowpan_listen net/bluetooth/6lowpan.c:959 [inline]
 do_enable_set+0x583/0x960 net/bluetooth/6lowpan.c:1078
 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2264
 worker_thread+0x98/0xe40 kernel/workqueue.c:2410
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

Freed by task 3002:
 save_stack+0x23/0x90 mm/kasan/common.c:72
 set_track mm/kasan/common.c:80 [inline]
 kasan_set_free_info mm/kasan/common.c:337 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:476
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:485
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3757
 l2cap_chan_destroy net/bluetooth/l2cap_core.c:484 [inline]
 kref_put include/linux/kref.h:65 [inline]
 l2cap_chan_put+0x1b7/0x240 net/bluetooth/l2cap_core.c:498
 do_enable_set+0x54b/0x960 net/bluetooth/6lowpan.c:1075
 process_one_work+0xa05/0x17a0 kernel/workqueue.c:2264
 worker_thread+0x98/0xe40 kernel/workqueue.c:2410
 kthread+0x361/0x430 kernel/kthread.c:255
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff88809e4a4000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 32 bytes inside of
 2048-byte region [ffff88809e4a4000, ffff88809e4a4800)
The buggy address belongs to the page:
page:ffffea0002792900 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea00027dab48 ffffea000261cfc8 ffff8880aa400e00
raw: 0000000000000000 ffff88809e4a4000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809e4a3f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88809e4a3f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88809e4a4000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff88809e4a4080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809e4a4100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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