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BUG: KASAN: use-after-free in atomic_inc include/asm-generic/atomic-instrumented.h:239 [inline]
BUG: KASAN: use-after-free in hci_sock_bind+0x183f/0x1aa0 net/bluetooth/hci_sock.c:1250
Write of size 4 at addr ffff88804749d250 by task syz-executor.2/5450

CPU: 1 PID: 5450 Comm: syz-executor.2 Not tainted 5.7.0-rc7-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+0x1e9/0x30e lib/dump_stack.c:118
 print_address_description+0x74/0x5c0 mm/kasan/report.c:382
 __kasan_report+0x103/0x1a0 mm/kasan/report.c:511
 kasan_report+0x4d/0x80 mm/kasan/common.c:625

Allocated by task 5453:
 save_stack mm/kasan/common.c:49 [inline]
 set_track mm/kasan/common.c:57 [inline]
 __kasan_kmalloc+0x114/0x160 mm/kasan/common.c:495
 kmem_cache_alloc_trace+0x234/0x300 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 hci_alloc_dev+0x4c/0x1840 net/bluetooth/hci_core.c:3365
 __vhci_create_device drivers/bluetooth/hci_vhci.c:99 [inline]
 vhci_create_device+0x113/0x520 drivers/bluetooth/hci_vhci.c:148
 vhci_get_user drivers/bluetooth/hci_vhci.c:205 [inline]
 vhci_write+0x36d/0x400 drivers/bluetooth/hci_vhci.c:285
 call_write_iter include/linux/fs.h:1907 [inline]
 new_sync_write fs/read_write.c:484 [inline]
 __vfs_write+0x54c/0x710 fs/read_write.c:497
 vfs_write+0x274/0x580 fs/read_write.c:559
 ksys_write+0x11b/0x220 fs/read_write.c:612
 do_syscall_64+0xf3/0x1b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

Freed by task 5445:
 save_stack mm/kasan/common.c:49 [inline]
 set_track mm/kasan/common.c:57 [inline]
 kasan_set_free_info mm/kasan/common.c:317 [inline]
 __kasan_slab_free+0x125/0x190 mm/kasan/common.c:456
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x10a/0x220 mm/slab.c:3757
 bt_host_release+0x18/0x20 net/bluetooth/hci_sysfs.c:86
 device_release+0x70/0x1a0 drivers/base/core.c:1390
 kobject_cleanup lib/kobject.c:693 [inline]
 kobject_release lib/kobject.c:722 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1cf/0x290 lib/kobject.c:739
 vhci_release+0x7b/0xc0 drivers/bluetooth/hci_vhci.c:341
 __fput+0x2ed/0x750 fs/file_table.c:280
 task_work_run+0x147/0x1d0 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:165 [inline]
 prepare_exit_to_usermode+0x48e/0x600 arch/x86/entry/common.c:196
 entry_SYSCALL_64_after_hwframe+0x49/0xb3

The buggy address belongs to the object at ffff88804749c000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 4688 bytes inside of
 8192-byte region [ffff88804749c000, ffff88804749e000)
The buggy address belongs to the page:
page:ffffea00011d2700 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 head:ffffea00011d2700 order:2 compound_mapcount:0 compound_pincount:0
flags: 0xfffe0000010200(slab|head)
raw: 00fffe0000010200 ffffea00013e8208 ffffea0001298608 ffff8880aa4021c0
raw: 0000000000000000 ffff88804749c000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88804749d100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804749d180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88804749d200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff88804749d280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88804749d300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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