Bluetooth: ISO: Reject concurrent BIS listener setup

Overview

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

Bluetooth: ISO: Reject concurrent BIS listener setup

iso_sock_listen() drops the socket lock before calling iso_listen_bis() to preserve the hdev->lock ordering. Two concurrent listen() calls on the same broadcast socket can therefore both observe BT_BOUND. Caller A can attach connA and release the locks, then caller B can acquire them and attach connB before A publishes BT_LISTEN.

__iso_chan_add() checks whether connB already has a socket, but not whether the socket already has a connection. The second attachment overwrites iso_pi(sk)->conn, leaking the connA reference and leaving connA->sk intact. Socket teardown follows connB, so later events on connA can cause a stale socket access.

Recheck BT_BOUND and require iso_pi(sk)->conn to be NULL after taking both the HCI device and socket locks in iso_listen_bis(). The connection check also covers the interval between attachment and publication of BT_LISTEN. Reject a competing setup with -EBADFD through the existing unlock path before allocating another connection.

A recorded KASAN report from an instrumented kernel shows:

BUG: KASAN: slab-use-after-free in iso_sock_hold+0x119/0x1f0 Call Trace: iso_sock_hold+0x119/0x1f0 iso_conn_del+0xe4/0x270 hci_disconn_complete_evt+0x351/0x8c0 hci_event_packet+0x71b/0xb20 hci_rx_work+0x293/0x730

Allocated by task 93: sk_prot_alloc+0x113/0x220 sk_alloc+0x2b/0x6d0 bt_sock_alloc+0x29/0x370 iso_sock_alloc.constprop.0+0x19/0x300 iso_sock_create+0x94/0x100

Freed by task 93: kfree+0x121/0x3c0 __sk_destruct+0x42b/0x540 iso_sock_release+0x29d/0x340 __sock_release+0xa1/0x260 sock_close+0x10/0x20

Affected

• Linux >= c541d7b5e17987ed330798b07d4ad508859c1c93 < 559e4d2b6f83aaa96061659cc7104b7a0293f9ef
• Linux >= 168e28305b871d8ec604a8f51f35467b8d7ba05b < 90b744066ca520d1a6a505a11ade9c9a5f48accf
• Linux >= 168e28305b871d8ec604a8f51f35467b8d7ba05b < 79993e9919a87068183ba3622c383f05c049c4bc
• Linux >= 168e28305b871d8ec604a8f51f35467b8d7ba05b < 555ff78fa719f50ff4cdbdb40aa1acc6e8e327d3
• Linux >= 6.12.6 < 6.12.113
• Linux 6.13

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.