CVE-2026-53256

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

Bluetooth: RFCOMM: hold listener socket in rfcomm_connect_ind()

rfcomm_get_sock_by_channel() scans rfcomm_sk_list under the list lock,

but returns the selected listener after dropping that lock without

taking a reference. rfcomm_connect_ind() then locks the listener,

queues a child socket on it, and may notify it after unlocking it.

The buggy scenario involves two paths, with each column showing the

order within that path:

rfcomm_connect_ind(): listener close:

1. Find parent in 1. close() enters

rfcomm_get_sock_by_channel() rfcomm_sock_release().

2. Drop rfcomm_sk_list.lock 2. rfcomm_sock_shutdown()

without pinning parent. closes the listener.

3. Call lock_sock(parent) and 3. rfcomm_sock_kill()

bt_accept_enqueue(parent, unlinks and puts parent.

sk, true).

4. Read parent flags and may 4. parent can be freed.

call sk_state_change().

If close wins the race, parent can be freed before

rfcomm_connect_ind() reaches lock_sock(), bt_accept_enqueue(), or the

deferred-setup callback.

Take a reference on the listener before leaving rfcomm_sk_list.lock.

After lock_sock() succeeds, recheck that it is still in BT_LISTEN

before queueing a child, cache the deferred-setup bit while the parent

is locked, and drop the reference after the last parent use.

KASAN reported a slab-use-after-free in lock_sock_nested() from

rfcomm_connect_ind(), with the freeing stack going through

rfcomm_sock_kill() and rfcomm_sock_release().