Vulnerability details

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

• https://git.kernel.org/stable/c/62ce8b33eb238cf18c15207332fbdc26d858f592
• https://git.kernel.org/stable/c/3873f3449701b3dc98cba577923be6493598e7a1
• https://git.kernel.org/stable/c/7ded3264106418c6456ccceaafd9fda596ce12c3
• https://git.kernel.org/stable/c/82425b14f0fb22e46cfddc56d6465570f5ed0ce6
• https://git.kernel.org/stable/c/1b7841ffad08e911e8c4b9470f3fa08423568940
• https://git.kernel.org/stable/c/946d76db77ee5f922968ce558629ae47b381e3fc
• https://git.kernel.org/stable/c/fbf7961964a6e93360179f64712320ae9a1e9577
• https://git.kernel.org/stable/c/759c185d0bbdb131357408f50b8735e04ed3caff