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BUG: KASAN: use-after-free in hci_chan_del+0x131/0x180 net/bluetooth/hci_conn.c:1547
Read of size 8 at addr ffff8880a8f17198 by task syz-executor.0/6376

CPU: 1 PID: 6376 Comm: syz-executor.0 Not tainted 4.14.192-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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_load8_noabort+0x68/0x70 mm/kasan/report.c:430
 hci_chan_del+0x131/0x180 net/bluetooth/hci_conn.c:1547
 l2cap_conn_del+0x417/0x670 net/bluetooth/l2cap_core.c:1736
 l2cap_disconn_cfm net/bluetooth/l2cap_core.c:7435 [inline]
 l2cap_disconn_cfm+0x6b/0x80 net/bluetooth/l2cap_core.c:7428
 hci_disconn_cfm include/net/bluetooth/hci_core.h:1226 [inline]
 hci_conn_hash_flush+0x114/0x220 net/bluetooth/hci_conn.c:1376
 hci_dev_do_close+0x542/0xc50 net/bluetooth/hci_core.c:1620
 hci_unregister_dev+0x170/0x7a0 net/bluetooth/hci_core.c:3191
 vhci_release+0x70/0xe0 drivers/bluetooth/hci_vhci.c:354
 __fput+0x25f/0x7a0 fs/file_table.c:210
 task_work_run+0x11f/0x190 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0xa08/0x27f0 kernel/exit.c:865
 do_group_exit+0x100/0x2e0 kernel/exit.c:962
 SYSC_exit_group kernel/exit.c:973 [inline]
 SyS_exit_group+0x19/0x20 kernel/exit.c:971
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x45ccd9
RSP: 002b:00007ffe10af8d98 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000045ccd9
RDX: 0000000000416731 RSI: 0000000000ca85f0 RDI: 0000000000000043
RBP: 00000000004c2963 R08: 000000000000000b R09: 0000000000000000
R10: 0000000002b09940 R11: 0000000000000246 R12: 0000000000000005
R13: 00007ffe10af8ee0 R14: 00000000001efbab R15: 00007ffe10af8ef0

Allocated by task 3656:
 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]
 call_usermodehelper_setup+0x73/0x2e0 kernel/umh.c:374
 kobject_uevent_env+0xab1/0xcb0 lib/kobject_uevent.c:525
 kobject_synth_uevent+0x5b6/0x6ca lib/kobject_uevent.c:205
 uevent_store+0x21/0x60 drivers/base/core.c:1005
 dev_attr_store+0x56/0x80 drivers/base/core.c:723
 sysfs_kf_write+0x106/0x160 fs/sysfs/file.c:141
 kernfs_fop_write+0x289/0x440 fs/kernfs/file.c:316
 __vfs_write+0xe4/0x630 fs/read_write.c:480
 vfs_write+0x17f/0x4d0 fs/read_write.c:544
 SYSC_write fs/read_write.c:590 [inline]
 SyS_write+0xf2/0x210 fs/read_write.c:582
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb

Freed by task 30113:
 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
 call_usermodehelper_freeinfo kernel/umh.c:43 [inline]
 umh_complete kernel/umh.c:57 [inline]
 call_usermodehelper_exec_async+0x3f2/0x4a0 kernel/umh.c:110
 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404

The buggy address belongs to the object at ffff8880a8f17180
 which belongs to the cache kmalloc-128 of size 128
The buggy address is located 24 bytes inside of
 128-byte region [ffff8880a8f17180, ffff8880a8f17200)
The buggy address belongs to the page:
page:ffffea0002a3c5c0 count:1 mapcount:0 mapping:ffff8880a8f17000 index:0xffff8880a8f179c0
flags: 0xfffe0000000100(slab)
raw: 00fffe0000000100 ffff8880a8f17000 ffff8880a8f179c0 0000000100000010
raw: ffffea000279afa0 ffffea00026cf520 ffff88812fe52640 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a8f17080: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8880a8f17100: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
>ffff8880a8f17180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8880a8f17200: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8880a8f17280: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
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