UBUNTU-CVE-2024-26761

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UBUNTU-CVE-2024-26761

Summary:

Details: In the Linux kernel, the following vulnerability has been resolved: cxl/pci: Fix disabling memory if DVSEC CXL Range does not match a CFMWS window The Linux CXL subsystem is built on the assumption that HPA == SPA. That is, the host physical address (HPA) the HDM decoder registers are programmed with are system physical addresses (SPA). During HDM decoder setup, the DVSEC CXL range registers (cxl-3.1, 8.1.3.8) are checked if the memory is enabled and the CXL range is in a HPA window that is described in a CFMWS structure of the CXL host bridge (cxl-3.1, 9.18.1.3). Now, if the HPA is not an SPA, the CXL range does not match a CFMWS window and the CXL memory range will be disabled then. The HDM decoder stops working which causes system memory being disabled and further a system hang during HDM decoder initialization, typically when a CXL enabled kernel boots. Prevent a system hang and do not disable the HDM decoder if the decoder's CXL range is not found in a CFMWS window. Note the change only fixes a hardware hang, but does not implement HPA/SPA translation. Support for this can be added in a follow on patch series.

References: https://ubuntu.com/security/CVE-2024-26761, https://git.kernel.org/linus/0cab687205986491302cd2e440ef1d253031c221, https://git.kernel.org/stable/c/031217128990d7f0ab8c46db1afb3cf1e075fd29, https://git.kernel.org/stable/c/2cc1a530ab31c65b52daf3cb5d0883c8b614ea69, https://git.kernel.org/stable/c/3a3181a71935774bda2398451256d7441426420b, https://git.kernel.org/stable/c/0cab687205986491302cd2e440ef1d253031c221, https://www.cve.org/CVERecord?id=CVE-2024-26761