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BUG: KASAN: use-after-free in hci_chan_del+0x14f/0x190 net/bluetooth/hci_conn.c:1728
Read of size 8 at addr ffff8880a850fe18 by task syz-executor.3/10935

CPU: 0 PID: 10935 Comm: syz-executor.3 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 hci_chan_del+0x14f/0x190 net/bluetooth/hci_conn.c:1728
 l2cap_conn_del+0x61b/0x9e0 net/bluetooth/l2cap_core.c:1900
 l2cap_disconn_cfm net/bluetooth/l2cap_core.c:8160 [inline]
 l2cap_disconn_cfm+0x85/0xa0 net/bluetooth/l2cap_core.c:8153
 hci_disconn_cfm include/net/bluetooth/hci_core.h:1438 [inline]
 hci_conn_hash_flush+0x114/0x220 net/bluetooth/hci_conn.c:1557
 hci_dev_do_close+0x5c6/0x1080 net/bluetooth/hci_core.c:1770
 hci_unregister_dev+0x1bd/0xe30 net/bluetooth/hci_core.c:3790
 vhci_release+0x70/0xe0 drivers/bluetooth/hci_vhci.c:340
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:135
 exit_task_work include/linux/task_work.h:25 [inline]
 do_exit+0xb7d/0x29f0 kernel/exit.c:806
 do_group_exit+0x125/0x310 kernel/exit.c:903
 get_signal+0x40b/0x1ee0 kernel/signal.c:2743
 arch_do_signal+0x82/0x2520 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:135 [inline]
 exit_to_user_mode_prepare+0x15d/0x1c0 kernel/entry/common.c:166
 syscall_exit_to_user_mode+0x59/0x2b0 kernel/entry/common.c:241
 __do_fast_syscall_32+0x63/0x80 arch/x86/entry/common.c:127
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:149
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7f09549
Code: Bad RIP value.
RSP: 002b:00000000f550312c EFLAGS: 00000292 ORIG_RAX: 00000000000000f0
RAX: fffffffffffffe00 RBX: 0000000008b9bfa8 RCX: 0000000000000080
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000008b9bfac
RBP: 00000000f5503228 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 12762:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x16e/0x2c0 mm/slab.c:3550
 kmalloc include/linux/slab.h:554 [inline]
 kzalloc include/linux/slab.h:666 [inline]
 cdev_alloc+0x3d/0xd0 fs/char_dev.c:635
 tty_cdev_add+0x4a/0x290 drivers/tty/tty_io.c:3044
 tty_register_device_attr+0x476/0x7b0 drivers/tty/tty_io.c:3158
 gsmld_attach_gsm drivers/tty/n_gsm.c:2390 [inline]
 gsmld_open+0x5cc/0x8d0 drivers/tty/n_gsm.c:2516
 tty_ldisc_open+0x9b/0x110 drivers/tty/tty_ldisc.c:464
 tty_set_ldisc+0x2e8/0x670 drivers/tty/tty_ldisc.c:591
 tiocsetd drivers/tty/tty_io.c:2333 [inline]
 tty_ioctl+0xadf/0x15f0 drivers/tty/tty_io.c:2593
 tty_compat_ioctl+0x295/0x410 drivers/tty/tty_io.c:2818
 __do_compat_sys_ioctl+0x1d3/0x230 fs/ioctl.c:842
 do_syscall_32_irqs_on arch/x86/entry/common.c:84 [inline]
 __do_fast_syscall_32+0x57/0x80 arch/x86/entry/common.c:126
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:149
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

The buggy address belongs to the object at ffff8880a850fe00
 which belongs to the cache kmalloc-128 of size 128
The buggy address is located 24 bytes inside of
 128-byte region [ffff8880a850fe00, ffff8880a850fe80)
The buggy address belongs to the page:
page:00000000f2d0f444 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880a850f400 pfn:0xa850f
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002565088 ffffea0002447748 ffff8880aa040400
raw: ffff8880a850f400 ffff8880a850f000 000000010000000e 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a850fd00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880a850fd80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880a850fe00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8880a850fe80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880a850ff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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