CVE-2022-49909

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> Bluetooth: L2CAP: fix use-after-free in l2cap_conn_del()<br /> <br /> When l2cap_recv_frame() is invoked to receive data, and the cid is<br /> L2CAP_CID_A2MP, if the channel does not exist, it will create a channel.<br /> However, after a channel is created, the hold operation of the channel<br /> is not performed. In this case, the value of channel reference counting<br /> is 1. As a result, after hci_error_reset() is triggered, l2cap_conn_del()<br /> invokes the close hook function of A2MP to release the channel. Then<br /> l2cap_chan_unlock(chan) will trigger UAF issue.<br /> <br /> The process is as follows:<br /> Receive data:<br /> l2cap_data_channel()<br /> a2mp_channel_create() ---&gt;channel ref is 2<br /> l2cap_chan_put() ---&gt;channel ref is 1<br /> <br /> Triger event:<br /> hci_error_reset()<br /> hci_dev_do_close()<br /> ...<br /> l2cap_disconn_cfm()<br /> l2cap_conn_del()<br /> l2cap_chan_hold() ---&gt;channel ref is 2<br /> l2cap_chan_del() ---&gt;channel ref is 1<br /> a2mp_chan_close_cb() ---&gt;channel ref is 0, release channel<br /> l2cap_chan_unlock() ---&gt;UAF of channel<br /> <br /> The detailed Call Trace is as follows:<br /> BUG: KASAN: use-after-free in __mutex_unlock_slowpath+0xa6/0x5e0<br /> Read of size 8 at addr ffff8880160664b8 by task kworker/u11:1/7593<br /> Workqueue: hci0 hci_error_reset<br /> Call Trace:<br /> <br /> dump_stack_lvl+0xcd/0x134<br /> print_report.cold+0x2ba/0x719<br /> kasan_report+0xb1/0x1e0<br /> kasan_check_range+0x140/0x190<br /> __mutex_unlock_slowpath+0xa6/0x5e0<br /> l2cap_conn_del+0x404/0x7b0<br /> l2cap_disconn_cfm+0x8c/0xc0<br /> hci_conn_hash_flush+0x11f/0x260<br /> hci_dev_close_sync+0x5f5/0x11f0<br /> hci_dev_do_close+0x2d/0x70<br /> hci_error_reset+0x9e/0x140<br /> process_one_work+0x98a/0x1620<br /> worker_thread+0x665/0x1080<br /> kthread+0x2e4/0x3a0<br /> ret_from_fork+0x1f/0x30<br /> <br /> <br /> Allocated by task 7593:<br /> kasan_save_stack+0x1e/0x40<br /> __kasan_kmalloc+0xa9/0xd0<br /> l2cap_chan_create+0x40/0x930<br /> amp_mgr_create+0x96/0x990<br /> a2mp_channel_create+0x7d/0x150<br /> l2cap_recv_frame+0x51b8/0x9a70<br /> l2cap_recv_acldata+0xaa3/0xc00<br /> hci_rx_work+0x702/0x1220<br /> process_one_work+0x98a/0x1620<br /> worker_thread+0x665/0x1080<br /> kthread+0x2e4/0x3a0<br /> ret_from_fork+0x1f/0x30<br /> <br /> Freed by task 7593:<br /> kasan_save_stack+0x1e/0x40<br /> kasan_set_track+0x21/0x30<br /> kasan_set_free_info+0x20/0x30<br /> ____kasan_slab_free+0x167/0x1c0<br /> slab_free_freelist_hook+0x89/0x1c0<br /> kfree+0xe2/0x580<br /> l2cap_chan_put+0x22a/0x2d0<br /> l2cap_conn_del+0x3fc/0x7b0<br /> l2cap_disconn_cfm+0x8c/0xc0<br /> hci_conn_hash_flush+0x11f/0x260<br /> hci_dev_close_sync+0x5f5/0x11f0<br /> hci_dev_do_close+0x2d/0x70<br /> hci_error_reset+0x9e/0x140<br /> process_one_work+0x98a/0x1620<br /> worker_thread+0x665/0x1080<br /> kthread+0x2e4/0x3a0<br /> ret_from_fork+0x1f/0x30<br /> <br /> Last potentially related work creation:<br /> kasan_save_stack+0x1e/0x40<br /> __kasan_record_aux_stack+0xbe/0xd0<br /> call_rcu+0x99/0x740<br /> netlink_release+0xe6a/0x1cf0<br /> __sock_release+0xcd/0x280<br /> sock_close+0x18/0x20<br /> __fput+0x27c/0xa90<br /> task_work_run+0xdd/0x1a0<br /> exit_to_user_mode_prepare+0x23c/0x250<br /> syscall_exit_to_user_mode+0x19/0x50<br /> do_syscall_64+0x42/0x80<br /> entry_SYSCALL_64_after_hwframe+0x63/0xcd<br /> <br /> Second to last potentially related work creation:<br /> kasan_save_stack+0x1e/0x40<br /> __kasan_record_aux_stack+0xbe/0xd0<br /> call_rcu+0x99/0x740<br /> netlink_release+0xe6a/0x1cf0<br /> __sock_release+0xcd/0x280<br /> sock_close+0x18/0x20<br /> __fput+0x27c/0xa90<br /> task_work_run+0xdd/0x1a0<br /> exit_to_user_mode_prepare+0x23c/0x250<br /> syscall_exit_to_user_mode+0x19/0x50<br /> do_syscall_64+0x42/0x80<br /> entry_SYSCALL_64_after_hwframe+0x63/0xcd