CVE-2026-74533: Bluetooth: ISO: fix race of kfree vs kref_get_unless_zero

From: Greg Kroah-Hartman <[email protected]>

Description
===========

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

Bluetooth: ISO: fix race of kfree vs kref_get_unless_zero

hci_conn::iso_data is accessed and modified without lock or RCU.
This leads to a race

    [Task hdev->workqueue]                 	[Task 2]
    iso_recv                                    iso_conn_put(conn)
      conn = LOAD hcon->iso_data                  iso_conn_free(conn)
      iso_conn_hold_unless_zero(conn)               hcon->iso_data = NULL
                                                    kfree(conn)
        kref_get_unless_zero(&conn->ref) /* UAF */

and also to races in iso_conn_add() vs. iso_conn_free().

Fix by adding spinlock hci_conn::proto_lock and using it to guard
hci_conn::iso_data.

The Linux kernel CVE team has assigned CVE-2026-74533 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.13 with commit dc26097bdb864a0d5955b9a25e43376ffc1af99b and fixed in 7.1.8 with commit 876a3e94c70d0859d1dad1c986112d4f0d99eba8
	Issue introduced in 6.13 with commit dc26097bdb864a0d5955b9a25e43376ffc1af99b and fixed in 7.2-rc6 with commit af24e338bf5dafb80f42baa9a0b9e9b57b1c5d9c
	Issue introduced in 6.11.11 with commit f53e7489273dc2bb307bf50f319b3762d45534f0
	Issue introduced in 6.12.2 with commit a58d0f5dac322e16cc75334d000666512341bde5

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-74533
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	include/net/bluetooth/hci_core.h
	net/bluetooth/hci_conn.c
	net/bluetooth/iso.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/876a3e94c70d0859d1dad1c986112d4f0d99eba8
	https://git.kernel.org/stable/c/af24e338bf5dafb80f42baa9a0b9e9b57b1c5d9c