==================================================================
BUG: KASAN: use-after-free in __mutex_lock+0x801/0x1350
Read of size 8 at addr ffff88811905c0a8 by task khidpd_10cf5502/6890

CPU: 0 UID: 0 PID: 6890 Comm: khidpd_10cf5502 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 __mutex_lock+0x801/0x1350
 l2cap_unregister_user+0x6a/0x1b0
 hidp_session_thread+0x3a1/0x420
 kthread+0x711/0x8a0
 ret_from_fork+0x599/0xb30
 ret_from_fork_asm+0x1a/0x30
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff88811905f800 pfn:0x11905c
flags: 0x17ff00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 017ff00000000000 ffff88823c640e40 ffff88823c640e40 0000000000000000
raw: ffff88811905f800 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x40dc0(GFP_KERNEL|__GFP_ZERO|__GFP_COMP), pid 6793, tgid 6793 (syz-executor), ts 107651485977, free_ts 137666174352
 post_alloc_hook+0x23d/0x2a0
 get_page_from_freelist+0x22f6/0x23d0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 ___kmalloc_large_node+0x4e/0x150
 __kmalloc_large_node_noprof+0x18/0x90
 __kmalloc_noprof+0x4c9/0x800
 hci_alloc_dev_priv+0x28/0x2060
 vhci_create_device+0x120/0x650
 vhci_write+0x3ce/0x4a0
 vfs_write+0x5c9/0xb30
 ksys_write+0x145/0x250
 do_syscall_64+0xfa/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 7624 tgid 7624 stack trace:
 __free_frozen_pages+0xb99/0xd10
 bt_host_release+0x82/0x90
 device_release+0x9e/0x1d0
 kobject_put+0x228/0x570
 vhci_release+0x15a/0x1a0
 __fput+0x44c/0xa70
 task_work_run+0x1d4/0x260
 do_exit+0x8bd/0x25b0
 do_group_exit+0x21c/0x2d0
 get_signal+0x1285/0x1340
 arch_do_signal_or_restart+0x9a/0x7a0
 exit_to_user_mode_loop+0x87/0x4f0
 do_syscall_64+0x2d0/0xf80
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88811905bf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88811905c000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88811905c080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                  ^
 ffff88811905c100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88811905c180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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