Bluetooth: ISO: balance the parent hold in hci_bind_bis()

Overview

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

Bluetooth: ISO: balance the parent hold in hci_bind_bis()

hci_conn_link() takes a lifetime reference to its parent with hci_conn_get(), but only takes an operational hold on the child. hci_conn_unlink() later balances both a hold and a reference on the parent.

The SCO and CIS paths pass a parent acquired from a connect helper, so it already has a hold. For an additional BIS, hci_bind_bis() obtains the parent from hci_conn_hash_lookup_big(), which returns a bare pointer. Unlinking the child then drops the parent's existing hold and can schedule it for disconnection while its socket is still using it.

Take a hold on the parent before linking it and drop that hold if linking fails. A successful link transfers the hold to hci_conn_unlink().

Affected

• Linux >= 11dc486ed5d4626e6b92a23b67ed76cb6c48bfc9 < ff28e6c67143c76ef50c3eac01f2fad411705f71
• Linux >= fa224d0c094a458e9ebf5ea9b1c696136b7af427 < 03a91cdf6862fb351a74f035ad21e70112438552
• Linux >= fa224d0c094a458e9ebf5ea9b1c696136b7af427 < 4e49206d9574a4c109480198e73aea34ad0ed7f6
• Linux >= fa224d0c094a458e9ebf5ea9b1c696136b7af427 < bbcd723ee7a84bc868142fd57717af88e54e555a
• Linux >= fa224d0c094a458e9ebf5ea9b1c696136b7af427 < 4c94557dd02569efa6c1072a0439addaef9a5224
• Linux >= 6.6.67 < 6.6.158
• Linux 6.8

Remediation

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