Fan Ni

**Name of the Vulnerable Software and Affected Versions** Linux kernel (affected versions not specified) **Description** The issue is related to a null pointer dereference in the cxl/region component of the Linux kernel. This occurs when the `cxl region decode reset` function is called, and the `->reset()` callback is invoked unconditionally, even if a decoder does not have a reset callback. The CXL specification allows a host bridge with a single root port to have no explicit HDM decoders, and the region driver assumes there are none, creating a special pass-through decoder instance without a commit/reset callback. This can cause a null pointer dereference in configurations 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. A kernel crash was observed when destroying the region and a pass-through decoder is reset. The issue can be reproduced by creating a region with a CXL setup and destroying it with the `cxl destroy-region` command. **Recommendations** At the moment, there is no information about a newer version that contains a fix for this vulnerability.