CVE-2024-35993: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-35993 affects the Linux kernel's memory management system, specifically the handling of hugetlb (huge page) functionality. The vulnerability was discovered in May 2024 and involves the folio_test_hugetlb() function, which can be fooled by a concurrent folio split into returning true for a folio that has never belonged to hugetlbfs (Kernel Git).

The vulnerability exists in the Linux kernel's memory management subsystem where the folio_test_hugetlb() function can return incorrect results during concurrent folio splits. This occurs because the current implementation can be deceived when a caller doesn't hold a refcount on the folio. The issue specifically affects memory-failure, compaction, and procfs operations. In systems with CONFIG_DEBUG_VM enabled, this can result in an oops condition, particularly since the commit 9c5ccf2db04b which added VM_BUG_ON() checks in the PageHuge() testing path (Kernel Git).

When exploited, this vulnerability could lead to incorrect handling of huge pages in the Linux kernel. This is particularly concerning in systems where memory-failure handling, memory compaction, or procfs operations are active. The issue could potentially result in system crashes (oops) when running with CONFIG_DEBUG_VM enabled (Kernel Git).

The vulnerability requires specific conditions to be exploited, particularly during concurrent folio splits when the caller doesn't hold a refcount. It primarily affects systems that use hugetlb pages and can be triggered through memory-failure, compaction, or procfs operations (Kernel Git).

The issue has been fixed in various Linux kernel versions, including Ubuntu 24.04 LTS (noble) with kernel version 6.8.0-40.40, Ubuntu 22.04 LTS with kernel version 6.8.0-40.40~22.04.3, and several other distributions. The fix involves turning folio_test_hugetlb into a PageType and implementing proper reference counting (Ubuntu Security).