CVE-2022-48707

In the Linux kernel, the following vulnerability has been resolved:
cxl/region: Fix null pointer dereference for resetting decoder Not all
decoders have a reset callback. The CXL specification allows a host bridge
with a single root port to have no explicit HDM decoders. Currently the
region driver assumes there are none. As such the CXL core creates a
special pass through decoder instance without a commit/reset callback.
Prior to this patch, the ->reset() callback was called unconditionally when
calling cxl_region_decode_reset. Thus a configuration with 1 Host Bridge, 1
Root Port, and one directly attached CXL type 3 device or multiple CXL type
3 devices attached to downstream ports of a switch can cause a null pointer
dereference. Before the fix, a kernel crash was observed when we destroy
the region, and a pass through decoder is reset. The issue can be
reproduced as below, 1) create a region with a CXL setup which includes a
HB with a single root port under which a memdev is attached directly. 2)
destroy the region with cxl destroy-region regionX -f.