CVE-2022-49909 (Important severity, published 2025-04-30)
CVSS score: 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Description: In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: L2CAP: fix use-after-free in l2cap_conn_del()

When l2cap_recv_frame() is invoked to receive data, and the cid is
L2CAP_CID_A2MP, if the channel does not exist, it will create a channel.
However, after a channel is created, the hold operation of the channel
is not performed. In this case, the value of channel reference counting
is 1. As a result, after hci_error_reset() is triggered, l2cap_conn_del()
invokes the close hook function of A2MP to release the channel. Then
 l2cap_chan_unlock(chan) will trigger UAF issue.

The process is as follows:
Receive data:
l2cap_data_channel()
    a2mp_channel_create()  --->channel ref is 2
    l2cap_chan_put()       --->channel ref is 1

Triger event:
    hci_error_reset()
        hci_dev_do_close()
        ...
        l2cap_disconn_cfm()
            l2cap_conn_del()
                l2cap_chan_hold()    --->channel ref is 2
                l2cap_chan_del()     --->channel ref is 1
                a2mp_chan_close_cb() --->channel ref is 0, release channel
                l2cap_chan_unlock()  --->UAF of channel

The detailed Call Trace is as follows:
BUG: KASAN: use-after-free in __mutex_unlock_slowpath+0xa6/0x5e0
Read of size 8 at addr ffff8880160664b8 by task kworker/u11:1/7593
Workqueue: hci0 hci_error_reset
Call Trace:
 <TASK>
 dump_stack_lvl+0xcd/0x134
 print_report.cold+0x2ba/0x719
 kasan_report+0xb1/0x1e0
 kasan_check_range+0x140/0x190
 __mutex_unlock_slowpath+0xa6/0x5e0
 l2cap_conn_del+0x404/0x7b0
 l2cap_disconn_cfm+0x8c/0xc0
 hci_conn_hash_flush+0x11f/0x260
 hci_dev_close_sync+0x5f5/0x11f0
 hci_dev_do_close+0x2d/0x70
 hci_error_reset+0x9e/0x140
 process_one_work+0x98a/0x1620
 worker_thread+0x665/0x1080
 kthread+0x2e4/0x3a0
 ret_from_fork+0x1f/0x30
 </TASK>

Allocated by task 7593:
 kasan_save_stack+0x1e/0x40
 __kasan_kmalloc+0xa9/0xd0
 l2cap_chan_create+0x40/0x930
 amp_mgr_create+0x96/0x990
 a2mp_channel_create+0x7d/0x150
 l2cap_recv_frame+0x51b8/0x9a70
 l2cap_recv_acldata+0xaa3/0xc00
 hci_rx_work+0x702/0x1220
 process_one_work+0x98a/0x1620
 worker_thread+0x665/0x1080
 kthread+0x2e4/0x3a0
 ret_from_fork+0x1f/0x30

Freed by task 7593:
 kasan_save_stack+0x1e/0x40
 kasan_set_track+0x21/0x30
 kasan_set_free_info+0x20/0x30
 ____kasan_slab_free+0x167/0x1c0
 slab_free_freelist_hook+0x89/0x1c0
 kfree+0xe2/0x580
 l2cap_chan_put+0x22a/0x2d0
 l2cap_conn_del+0x3fc/0x7b0
 l2cap_disconn_cfm+0x8c/0xc0
 hci_conn_hash_flush+0x11f/0x260
 hci_dev_close_sync+0x5f5/0x11f0
 hci_dev_do_close+0x2d/0x70
 hci_error_reset+0x9e/0x140
 process_one_work+0x98a/0x1620
 worker_thread+0x665/0x1080
 kthread+0x2e4/0x3a0
 ret_from_fork+0x1f/0x30

Last potentially related work creation:
 kasan_save_stack+0x1e/0x40
 __kasan_record_aux_stack+0xbe/0xd0
 call_rcu+0x99/0x740
 netlink_release+0xe6a/0x1cf0
 __sock_release+0xcd/0x280
 sock_close+0x18/0x20
 __fput+0x27c/0xa90
 task_work_run+0xdd/0x1a0
 exit_to_user_mode_prepare+0x23c/0x250
 syscall_exit_to_user_mode+0x19/0x50
 do_syscall_64+0x42/0x80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

Second to last potentially related work creation:
 kasan_save_stack+0x1e/0x40
 __kasan_record_aux_stack+0xbe/0xd0
 call_rcu+0x99/0x740
 netlink_release+0xe6a/0x1cf0
 __sock_release+0xcd/0x280
 sock_close+0x18/0x20
 __fput+0x27c/0xa90
 task_work_run+0xdd/0x1a0
 exit_to_user_mode_prepare+0x23c/0x250
 syscall_exit_to_user_mode+0x19/0x50
 do_syscall_64+0x42/0x80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
Statement: A use-after-free vulnerability was found in the Bluetooth L2CAP implementation. When receiving data on the A2MP channel, a newly created channel was not properly reference-counted due to a missing l2cap_chan_hold() call, leading to potential memory corruption when the channel was later freed and accessed. This issue can be triggered locally by an unprivileged user with Bluetooth access and may result in denial of service or potential code execution. Fixed starting from Red Hat Enterprise Linux 8.6 (and later) versions.