CVE-2024-50017

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> x86/mm/ident_map: Use gbpages only where full GB page should be mapped.<br /> <br /> When ident_pud_init() uses only GB pages to create identity maps, large<br /> ranges of addresses not actually requested can be included in the resulting<br /> table; a 4K request will map a full GB. This can include a lot of extra<br /> address space past that requested, including areas marked reserved by the<br /> BIOS. That allows processor speculation into reserved regions, that on UV<br /> systems can cause system halts.<br /> <br /> Only use GB pages when map creation requests include the full GB page of<br /> space. Fall back to using smaller 2M pages when only portions of a GB page<br /> are included in the request.<br /> <br /> No attempt is made to coalesce mapping requests. If a request requires a<br /> map entry at the 2M (pmd) level, subsequent mapping requests within the<br /> same 1G region will also be at the pmd level, even if adjacent or<br /> overlapping such requests could have been combined to map a full GB page.<br /> Existing usage starts with larger regions and then adds smaller regions, so<br /> this should not have any great consequence.