CVE-2023-52490

Summary

CVE-2023-52490 is a vulnerability affecting the Linux kernel. During page migration, an incorrect page mapping was found, leading to a NULL pointer dereference and system crash. The issue occurs when a thread performs memory hotplug on a page being migrated, discovering the page's refcount as 1 and attempting to offline it. However, the target page's mapping only saves the 'anon_vma' pointer without setting the PAGE_MAPPING_ANON flag, causing confusion for PFN walkers. Several solutions were considered, including flag setting, page locking, or using target page's private field. The chosen fix was using the private field to save the 'anon_vma' pointer and page state, which eliminates the impact on PFN walkers and simplifies the process.

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