CVE-2026-89569

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

Bluetooth: RFCOMM: serialize security confirmation handling

rfcomm security cfm() looks up a session on session list and then walks its DLC list without holding rfcomm mutex. Since RFCOMM session teardown uses rfcomm mutex, krfcommd can close and free the same session and DLCs concurrently:

hci rx work krfcommd

rfcomm session get() rfcomm lock() rfcomm session close() rfcomm dlc unlink() rfcomm session del() kfree(s) rfcomm unlock() walk s->dlcs

The callback can then read a freed session list head and touch freed DLCs while updating their flags or timers.

Serialize the session lookup and DLC traversal in rfcomm security cfm() with rfcomm mutex. This matches the existing RFCOMM session lifetime rules and prevents concurrent rfcomm session del() / rfcomm dlc unlink() from tearing the objects down while the callback is using them.

KASAN reported:

BUG: KASAN: slab-use-after-free in rfcomm security cfm+0x41c/0x440 Read of size 8 at addr ffff888111fb3960 by task kworker/u17:1/89 Workqueue: hci0 hci rx work Call Trace: rfcomm security cfm+0x41c/0x440 hci encrypt cfm+0x139/0x590 hci encrypt change evt+0x37b/0xc40 hci event packet+0x71b/0xb20 hci rx work+0x293/0x730 Allocated by task 69: rfcomm session add+0x9e/0x2f0 rfcomm run+0x44b/0x41e0 Freed by task 69: kfree+0x131/0x3c0 rfcomm session del+0x188/0x220 rfcomm run+0x1985/0x41e0