CVE-2023-52849

In the Linux kernel, the following vulnerability has been resolved:
cxl/mem: Fix shutdown order Ira reports that removing cxl_mock_mem causes a
crash with the following trace: BUG: kernel NULL pointer dereference,
address: 0000000000000044 […] RIP: 0010:cxl_region_decode_reset+0x7f/0x180
[cxl_core] […] Call Trace: <TASK> cxl_region_detach+0xe8/0x210 [cxl_core]
cxl_decoder_kill_region+0x27/0x40 [cxl_core] cxld_unregister+0x29/0x40
[cxl_core] devres_release_all+0xb8/0x110 device_unbind_cleanup+0xe/0x70
device_release_driver_internal+0x1d2/0x210 bus_remove_device+0xd7/0x150
device_del+0x155/0x3e0 device_unregister+0x13/0x60
devm_release_action+0x4d/0x90 ? __pfx_unregister_port+0x10/0x10 [cxl_core]
delete_endpoint+0x121/0x130 [cxl_core] devres_release_all+0xb8/0x110
device_unbind_cleanup+0xe/0x70 device_release_driver_internal+0x1d2/0x210
bus_remove_device+0xd7/0x150 device_del+0x155/0x3e0 ?
lock_release+0x142/0x290 cdev_device_del+0x15/0x50
cxl_memdev_unregister+0x54/0x70 [cxl_core] This crash is due to the
clearing out the cxl_memdev’s driver context (@cxlds) before the subsystem
is done with it. This is ultimately due to the region(s), that this memdev
is a member, being torn down and expecting to be able to de-reference
@cxlds, like here: static int cxl_region_decode_reset(struct cxl_region
*cxlr, int count) … if (cxlds->rcd) goto endpoint_reset; … Fix it by
keeping the driver context valid until memdev-device unregistration, and
subsequently the entire stack of related dependencies, unwinds.