An issue was discovered in Xen through 4.13.x, allowing guest OS users to cause a denial of service because of a bad error path in GNTTABOP_map_grant. Grant table operations are expected to return 0 for success, and a negative number for errors. Some misplaced brackets cause one error path to return 1 instead of a negative value. The grant table code in Linux treats this condition as success, and proceeds with incorrectly initialised state. A buggy or malicious guest can construct its grant table in such a way that, when a backend domain tries to map a grant, it hits the incorrect error path. This will crash a Linux based dom0 or backend domain.

References

• https://nvd.nist.gov/vuln/detail/CVE-2020-11743
• https://lists.fedoraproject.org/archives/list/[email protected]/message/5M2XRNCHOGGTJQBZQJ7DCV6ZNAKN3LE2/
• https://lists.fedoraproject.org/archives/list/[email protected]/message/NVTP4OYHCTRU3ONFJOFJQVNDFB25KLLG/
• https://lists.fedoraproject.org/archives/list/[email protected]/message/YMAW7D2MP6RE4BFI5BZWOBBWGY3VSOFN/
• https://security.gentoo.org/glsa/202005-08
• https://www.debian.org/security/2020/dsa-4723
• https://xenbits.xen.org/xsa/advisory-316.html
• http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00006.html
• http://www.openwall.com/lists/oss-security/2020/04/14/3
• http://xenbits.xen.org/xsa/advisory-316.html