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 listene…

Overview

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().

Affected

• linux_kernel >= 2.6.12.1, < 5.10.259
• linux_kernel >= 5.11, < 5.15.210
• linux_kernel >= 5.16, < 6.1.176
• linux_kernel >= 6.2, < 6.6.143
• linux_kernel >= 6.7, < 6.12.94
• linux_kernel >= 6.13, < 6.18.36
• linux_kernel >= 6.19, < 7.0.13
• linux_kernel = 2.6.12
• linux_kernel = 7.1

Remediation

Upgrade past the affected range:

• linux_kernel 7.0.13