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

Bluetooth: L2CAP: Fix UAF in channel timeout by holding conn ref

l2cap_chan_timeout() runs asynchronously and accesses chan->conn. If
the connection is torn down while the timer is running or pending,
chan->conn can be freed, leading to a use-after-free when the timer
worker attempts to lock conn->lock:

| BUG: KASAN: slab-use-after-free in instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
| BUG: KASAN: slab-use-after-free in atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:4456 [inline]
| BUG: KASAN: slab-use-after-free in __mutex_trylock_fast kernel/locking/mutex.c:161 [inline]
| BUG: KASAN: slab-use-after-free in mutex_lock+0x4f/0xa0 kernel/locking/mutex.c:318
| Write of size 8 at addr ffff8881298d9550 by task kworker/2:1/83
|
| CPU: 2 UID: 0 PID: 83 Comm: kworker/2:1 Not tainted 7.1.0-rc6-next-20260601-dirty #6 PREEMPT(full)
| Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-debian-1.17.0-1 04/01/2014
| Workqueue: events l2cap_chan_timeout
| Call Trace:
|  <TASK>
|  instrument_atomic_read_write include/linux/instrumented.h:112 [inline]
|  atomic_long_try_cmpxchg_acquire include/linux/atomic/atomic-instrumented.h:4456 [inline]
|  __mutex_trylock_fast kernel/locking/mutex.c:161 [inline]
|  mutex_lock+0x4f/0xa0 kernel/locking/mutex.c:318
|  l2cap_chan_timeout+0x5d/0x1b0 net/bluetooth/l2cap_core.c:422
|  process_one_work kernel/workqueue.c:3326 [inline]
|  process_scheduled_works+0x7c8/0xfb0 kernel/workqueue.c:3409
|  worker_thread+0x8a9/0xcf0 kernel/workqueue.c:3490
|  kthread+0x346/0x430 kernel/kthread.c:436
|  ret_from_fork+0x1a3/0x470 arch/x86/kernel/process.c:158
|  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
|  </TASK>
|
| Allocated by task 320:
|  l2cap_conn_add+0xa7/0x820 net/bluetooth/l2cap_core.c:7075
|  l2cap_connect_cfm+0xdb/0xd70 net/bluetooth/l2cap_core.c:7452
|  hci_connect_cfm include/net/bluetooth/hci_core.h:2139 [inline]
|  hci_remote_features_evt+0x52f/0x9f0 net/bluetooth/hci_event.c:3760
|  hci_event_func net/bluetooth/hci_event.c:7796 [inline]
|  hci_event_packet+0x561/0xa70 net/bluetooth/hci_event.c:7847
|  hci_rx_work+0x370/0x890 net/bluetooth/hci_core.c:4040
|  process_one_work kernel/workqueue.c:3326 [inline]
|  process_scheduled_works+0x7c8/0xfb0 kernel/workqueue.c:3409
|  worker_thread+0x8a9/0xcf0 kernel/workqueue.c:3490
|  kthread+0x346/0x430 kernel/kthread.c:436
|  ret_from_fork+0x1a3/0x470 arch/x86/kernel/process.c:158
|  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
|
| Freed by task 322:
|  hci_disconn_cfm include/net/bluetooth/hci_core.h:2154 [inline]
|  hci_conn_hash_flush+0x101/0x1f0 net/bluetooth/hci_conn.c:2736
|  hci_dev_close_sync+0x889/0xde0 net/bluetooth/hci_sync.c:5405
|  hci_dev_do_close net/bluetooth/hci_core.c:502 [inline]
|  hci_unregister_dev+0x1f7/0x370 net/bluetooth/hci_core.c:2679
|  vhci_release+0x12a/0x180 drivers/bluetooth/hci_vhci.c:690
|  __fput+0x369/0x890 fs/file_table.c:510
|  task_work_run+0x160/0x1d0 kernel/task_work.c:233
|  get_signal+0xf5b/0x1120 kernel/signal.c:2810
|  arch_do_signal_or_restart+0x4d/0x600 arch/x86/kernel/signal.c:337
|  __exit_to_user_mode_loop kernel/entry/common.c:64 [inline]
|  exit_to_user_mode_loop+0x85/0x510 kernel/entry/common.c:98
|  do_syscall_64+0x263/0x3d0 arch/x86/entry/syscall_64.c:100
|  entry_SYSCALL_64_after_hwframe+0x77/0x7f
|
| The buggy address belongs to the object at ffff8881298d9400
|  which belongs to the cache kmalloc-512 of size 512
| The buggy address is located 336 bytes inside of
|  freed 512-byte region [ffff8881298d9400, ffff8881298d9600)

Fix it by having chan->conn hold a reference to l2cap_conn (via
l2cap_conn_get) when the channel is added to the connection, and
releasing it in the channel destructor. This ensures the l2cap_conn
remains alive as long as the channel exists.

A new FLAG_DEL channel flag is introduced to indicate that the ch
---truncated---

https://git.kernel.org/stable/c/0b0e2bf39cf99e458d991b9df253727e036a7d7d

https://git.kernel.org/stable/c/50c38d9f42a529691e4e67ea9cedf4f0bfc8d277

https://git.kernel.org/stable/c/91047a4396a8b1857a6f712a90cf33ec0012b189

https://git.kernel.org/stable/c/b66774b48dd98f07254951f74ea6f513efe7ff8b

https://git.kernel.org/stable/c/d3b739db5dc6f688a60d56da872fabaf65246032

[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","programFiles":["include/net/bluetooth/l2cap.h","net/bluetooth/l2cap_core.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"89dec92041717b027216e110599e4f6d6c921b79","lessThan":"91047a4396a8b1857a6f712a90cf33ec0012b189","versionType":"git","status":"affected"},{"version":"50dfec218808b148ab4247b1858031b7a32015c5","lessThan":"0b0e2bf39cf99e458d991b9df253727e036a7d7d","versionType":"git","status":"affected"},{"version":"859d3ace791ed878ae9ba5522c7844d960da8f88","lessThan":"d3b739db5dc6f688a60d56da872fabaf65246032","versionType":"git","status":"affected"},{"version":"8c8e620467a7b51562dbcefbd1f09f288d7d710d","lessThan":"50c38d9f42a529691e4e67ea9cedf4f0bfc8d277","versionType":"git","status":"affected"},{"version":"8c8e620467a7b51562dbcefbd1f09f288d7d710d","lessThan":"b66774b48dd98f07254951f74ea6f513efe7ff8b","versionType":"git","status":"affected"},{"version":"3634cbdc2eb414b69ffa752ddbe5e0458518e321","versionType":"git","status":"affected"},{"version":"e1c100e2d61bd8c718b7d91fe3e050780a9bf72d","versionType":"git","status":"affected"},{"version":"deb8493a8fa599f6c95e2465b12bfdfb7f94a1d9","versionType":"git","status":"affected"},{"version":"7555fd885a0603f50e49a655850a1f2bd8a25398","versionType":"git","status":"affected"},{"version":"6.6.143","lessThan":"6.6.145","versionType":"semver","status":"affected"},{"version":"6.12.93","lessThan":"6.12.97","versionType":"semver","status":"affected"},{"version":"6.18.35","lessThan":"6.18.39","versionType":"semver","status":"affected"},{"version":"5.10.259","lessThan":"5.11","versionType":"semver","status":"affected"},{"version":"5.15.210","lessThan":"5.16","versionType":"semver","status":"affected"},{"version":"6.1.176","lessThan":"6.2","versionType":"semver","status":"affected"},{"version":"7.0.12","lessThan":"7.1","versionType":"semver","status":"affected"}]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","programFiles":["include/net/bluetooth/l2cap.h","net/bluetooth/l2cap_core.c"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"7.1","status":"affected"},{"version":"0","lessThan":"7.1","versionType":"semver","status":"unaffected"},{"version":"6.6.145","lessThanOrEqual":"6.6.*","versionType":"semver","status":"unaffected"},{"version":"6.12.97","lessThanOrEqual":"6.12.*","versionType":"semver","status":"unaffected"},{"version":"6.18.39","lessThanOrEqual":"6.18.*","versionType":"semver","status":"unaffected"},{"version":"7.1.4","lessThanOrEqual":"7.1.*","versionType":"semver","status":"unaffected"},{"version":"7.2-rc1","lessThanOrEqual":"*","versionType":"original_commit_for_fix","status":"unaffected"}]}]