CVE-2023-52771

In the Linux kernel, the following vulnerability has been resolved:
cxl/port: Fix delete_endpoint() vs parent unregistration race The CXL
subsystem, at cxl_mem ->probe() time, establishes a lineage of ports
(struct cxl_port objects) between an endpoint and the root of a CXL
topology. Each port including the endpoint port is attached to the cxl_port
driver. Given that setup, it follows that when either any port in that
lineage goes through a cxl_port ->remove() event, or the memdev goes
through a cxl_mem ->remove() event. The hierarchy below the removed port,
or the entire hierarchy if the memdev is removed needs to come down. The
delete_endpoint() callback is careful to check whether it is being called
to tear down the hierarchy, or if it is only being called to teardown the
memdev because an ancestor port is going through ->remove(). That care
needs to take the device_lock() of the endpoint’s parent. Which requires 2
bugs to be fixed: 1/ A reference on the parent is needed to prevent
use-after-free scenarios like this signature: BUG: spinlock bad magic on
CPU#0, kworker/u56:0/11 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
BIOS edk2-20230524-3.fc38 05/24/2023 Workqueue: cxl_port detach_memdev
[cxl_core] RIP: 0010:spin_bug+0x65/0xa0 Call Trace:
do_raw_spin_lock+0x69/0xa0 __mutex_lock+0x695/0xb80
delete_endpoint+0xad/0x150 [cxl_core] devres_release_all+0xb8/0x110
device_unbind_cleanup+0xe/0x70 device_release_driver_internal+0x1d2/0x210
detach_memdev+0x15/0x20 [cxl_core] process_one_work+0x1e3/0x4c0
worker_thread+0x1dd/0x3d0 2/ In the case of RCH topologies, the parent
device that needs to be locked is not always @port->dev as returned by
cxl_mem_find_port(), use endpoint->dev.parent instead.