Bluetooth: ISO: release unused CIS holds after channel attach

Overview

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

Bluetooth: ISO: release unused CIS holds after channel attach

hci_bind_cis() and hci_connect_cis() return one hci_conn hold for the ISO layer. A new channel association consumes that hold, which is eventually released by iso_conn_free().

There are two cases where iso_chan_add() does not create an association: it returns success when the socket is already attached to the same iso_conn, and it returns -EBUSY when another socket is attached. The hold returned for the current call is unused in both cases. This occurs when deferred setup calls iso_connect_cis() again for its existing socket, or when another socket attempts to reuse the CIS.

Detect the idempotent case while the connection is locked and release the unused hold after iso_chan_add(). Also release it on -EBUSY. Do not drop it for other errors: a newly allocated iso_conn releases the transferred hold when its last temporary reference is put.

Affected

• Linux >= 69997d50ec574be816b4ee8f9cee52ebbd53f8bd < e0e8b70207eaf27aee0a05ec5bf2d1b6bcb004d1
• Linux >= 69997d50ec574be816b4ee8f9cee52ebbd53f8bd < ed4c026cc4094dfb7a329b9d8df0ddd0be1b2458
• Linux >= 69997d50ec574be816b4ee8f9cee52ebbd53f8bd < e5fcca51177f224604e3a8c926ffd5edbeb58b09
• Linux >= 69997d50ec574be816b4ee8f9cee52ebbd53f8bd < 0fcd4dad555c96e0bd3a1b8c569f989be85c7341
• Linux 6.6

Remediation

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