Bluetooth: Fix use-after-free bugs caused by sco_sock_timeout

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: Fix use-after-free bugs caused by sco_sock_timeout

When the sco connection is established and then, the sco socket
is releasing, timeout_work will be scheduled to judge whether
the sco disconnection is timeout. The sock will be deallocated
later, but it is dereferenced again in sco_sock_timeout. As a
result, the use-after-free bugs will happen. The root cause is
shown below:

Cleanup Thread | Worker Thread
sco_sock_release |
sco_sock_close |
__sco_sock_close |
sco_sock_set_timer |
schedule_delayed_work |
sco_sock_kill | (wait a time)
sock_put(sk) //FREE | sco_sock_timeout
| sock_hold(sk) //USE

The KASAN report triggered by POC is shown below:

[ 95.890016] ==================================================================
[ 95.890496] BUG: KASAN: slab-use-after-free in sco_sock_timeout+0x5e/0x1c0
[ 95.890755] Write of size 4 at addr ffff88800c388080 by task kworker/0:0/7
...
[ 95.890755] Workqueue: events sco_sock_timeout
[ 95.890755] Call Trace:
[ 95.890755] <TASK>
[ 95.890755] dump_stack_lvl+0x45/0x110
[ 95.890755] print_address_description+0x78/0x390
[ 95.890755] print_report+0x11b/0x250
[ 95.890755] ? __virt_addr_valid+0xbe/0xf0
[ 95.890755] ? sco_sock_timeout+0x5e/0x1c0
[ 95.890755] kasan_report+0x139/0x170
[ 95.890755] ? update_load_avg+0xe5/0x9f0
[ 95.890755] ? sco_sock_timeout+0x5e/0x1c0
[ 95.890755] kasan_check_range+0x2c3/0x2e0
[ 95.890755] sco_sock_timeout+0x5e/0x1c0
[ 95.890755] process_one_work+0x561/0xc50
[ 95.890755] worker_thread+0xab2/0x13c0
[ 95.890755] ? pr_cont_work+0x490/0x490
[ 95.890755] kthread+0x279/0x300
[ 95.890755] ? pr_cont_work+0x490/0x490
[ 95.890755] ? kthread_blkcg+0xa0/0xa0
[ 95.890755] ret_from_fork+0x34/0x60
[ 95.890755] ? kthread_blkcg+0xa0/0xa0
[ 95.890755] ret_from_fork_asm+0x11/0x20
[ 95.890755] </TASK>
[ 95.890755]
[ 95.890755] Allocated by task 506:
[ 95.890755] kasan_save_track+0x3f/0x70
[ 95.890755] __kasan_kmalloc+0x86/0x90
[ 95.890755] __kmalloc+0x17f/0x360
[ 95.890755] sk_prot_alloc+0xe1/0x1a0
[ 95.890755] sk_alloc+0x31/0x4e0
[ 95.890755] bt_sock_alloc+0x2b/0x2a0
[ 95.890755] sco_sock_create+0xad/0x320
[ 95.890755] bt_sock_create+0x145/0x320
[ 95.890755] __sock_create+0x2e1/0x650
[ 95.890755] __sys_socket+0xd0/0x280
[ 95.890755] __x64_sys_socket+0x75/0x80
[ 95.890755] do_syscall_64+0xc4/0x1b0
[ 95.890755] entry_SYSCALL_64_after_hwframe+0x67/0x6f
[ 95.890755]
[ 95.890755] Freed by task 506:
[ 95.890755] kasan_save_track+0x3f/0x70
[ 95.890755] kasan_save_free_info+0x40/0x50
[ 95.890755] poison_slab_object+0x118/0x180
[ 95.890755] __kasan_slab_free+0x12/0x30
[ 95.890755] kfree+0xb2/0x240
[ 95.890755] __sk_destruct+0x317/0x410
[ 95.890755] sco_sock_release+0x232/0x280
[ 95.890755] sock_close+0xb2/0x210
[ 95.890755] __fput+0x37f/0x770
[ 95.890755] task_work_run+0x1ae/0x210
[ 95.890755] get_signal+0xe17/0xf70
[ 95.890755] arch_do_signal_or_restart+0x3f/0x520
[ 95.890755] syscall_exit_to_user_mode+0x55/0x120
[ 95.890755] do_syscall_64+0xd1/0x1b0
[ 95.890755] entry_SYSCALL_64_after_hwframe+0x67/0x6f
[ 95.890755]
[ 95.890755] The buggy address belongs to the object at ffff88800c388000
[ 95.890755] which belongs to the cache kmalloc-1k of size 1024
[ 95.890755] The buggy address is located 128 bytes inside of
[ 95.890755] freed 1024-byte region [ffff88800c388000, ffff88800c388400)
[ 95.890755]
[ 95.890755] The buggy address belongs to the physical page:
[ 95.890755] page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88800c38a800 pfn:0xc388
[ 95.890755] head: order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
[ 95.890755] ano
---truncated---