CWE-1316 Fabric-Address Map Allows Programming of Unwarranted Overlaps of Protected and Unprotected Ranges

The address map of the on-chip fabric has protected and unprotected regions overlapping, allowing an attacker to bypass access control to the overlapping portion of the protected region.

Occasionally, ranges in the address map could overlap. The overlap could either be intentional (e.g. due to a limited number of range registers or limited choice in choosing size of the range) or unintentional (e.g. introduced by errors). Some hardware designs allow dynamic remapping of address ranges assigned to peripheral MMIO ranges. In such designs, intentional address overlaps can be created through misconfiguration by malicious software.

• Confidentiality, Integrity, Access Control, Authorization: Bypass Protection Mechanism, Read Memory, Modify Memory — When protected and unprotected ranges overlap, an attacker could send a transaction and potentially compromise the protections in place, violating the principle of least privilege.

• [Architecture and Design] When architecting the address map of the chip, ensure that protected and unprotected ranges are isolated and do not overlap. When designing, ensure that ranges hardcoded in Register-Transfer Level (RTL) do not overlap. • [Implementation] Ranges configured by firmware should not overlap. If overlaps are mandatory because of constraints such as a limited number of registers, then ensure that no assets are present in the overlapped portion. • [Testing] Validate mitigation actions with robust testing.

• Automated Dynamic Analysis: Review address map in specification to see if there are any overlapping ranges. • Manual Static Analysis: Negative testing of access control on overlapped ranges.

• CVE-2009-4419: Attacker can modify MCHBAR register to overlap with an attacker-controlled region, which modification prevents the SENTER instruction from properly applying VT-d protection while a Measured Launch Environment is being launched.