Linux Kernel Hugetlb VMA Split Unsharing Vulnerability

A vulnerability in the Linux kernel's handling of hugetlb memory management has been addressed. The issue arose because the __split_vma() function initiated the unsharing of hugetlb page tables too early, before acquiring the necessary locks. This premature action allowed for race conditions where VMA-locked page faults and rmap walks from other processes could inadvertently cause page tables to be shared again before the split was completed. The vulnerability affects several versions of the Linux kernel, as the problematic behavior was introduced in version 5.13 and backported to earlier versions.

Impact

Exploitation of this vulnerability could lead to unintended sharing of hugetlb page tables, causing race conditions that disrupt normal memory management operations.